As filed with the Securities and Exchange Commission on ~~July~~November 149, 2023

Registration No. 333-__________

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM S-1

REGISTRATION STATEMENT UNDER THE SECURITIES ACT OF 1933

~~under~~ATHERSYS, ~~the Securities Act of 1933~~ INC.

Athersys, Inc.

(Exact name of registrant as specified in its charter)

Delaware	2834	20-4864095
(State or other jurisdiction of incorporation or organization)	(Primary Standard Industrial Classification Code Number)	(I.R.S. Employer Identification Number)
(State or jurisdiction of	(Primary Standard Industrial	(I.R.S. Employer
incorporation or organization)	Classification Code Number)	Identification No.)

3201 Carnegie Avenue

Cleveland, Ohio 44115-2634

Phone: (216) 431-9900

(Address, including zip code, and telephone number, including area code, of registrant’s principal executive offices)

Daniel A. Camardo

Chief Executive Officer

Athersys, Inc.

3201 Carnegie Avenue

Cleveland, Ohio 44115-2634

Phone: (216) 431-9900

(Name, address, including zip code, and telephone number, including area code, of agent for service)

Copies to:

Faith L. Charles, Esq. Naveen Pogula, Esq. Thompson Hine LLP 300 Madison Avenue, 27th Floor New York, New York 10017-4611 (212) 344-5680 Leslie Marlow, Esq. Patrick J. Egan, Esq. Hank Gracin, Esq. Blank Rome LLP 1271 Avenue of the Americas New York, New York 10020 (212) 885-5001

~~Approximate~~Thompson ~~date~~Hine ~~of commencement of proposed sale to the public:~~LLP

As300 ~~soon~~Madison asAvenue, ~~practicable~~27th ~~after the effective date of this registration statement.~~ Floor

IfNew ~~any of the securities being registered on this Form are to be offered on a delayed or continuous basis pursuant to Rule 415 under the Securities Act of 1933~~York, asNew ~~amended,~~York ~~check the following box. ☒~~10017-6232

IfPhone: ~~this Form is filed to register additional securities for an offering pursuant to Rule 462~~(b212) ~~under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering. ☐~~344-5680

Fax: (212) 344-6101

Approximate date of commencement of proposed sale to the public: As soon as practicable after the effective date of this registration statement.

If any of the securities being registered on this Form are to be offered on a delayed or continuous basis pursuant to Rule 415 under the Securities Act of 1933, check the following box. ☒

If this Form is filed to register additional securities for an offering pursuant to Rule 462(b) under the Securities Act, please check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering. ☐

If this Form is a post-effective amendment filed pursuant to Rule 462(c) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering. ☐

If this Form is a post-effective amendment filed pursuant to Rule 462(d) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering. ☐

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, a smaller reporting company, or an emerging growth company. See the definitions of “large accelerated filer,” “accelerated filer,” “smaller reporting company,” and “emerging growth company” in Rule 12b-2 of the Exchange Act.

Large ~~Accelerated~~accelerated ~~Filer~~filer ☐ ~~Smaller~~Accelerated ~~Reporting~~filer ~~Company~~☐ ☒Non-accelerated ~~Accelerated~~filer ~~Filer~~☒ ☐Smaller ~~Emerging~~reporting ~~Growth~~company ~~Company~~☒ ☐Emerging ~~Non-Accelerated~~growth ~~Filer~~company ☒☐

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided to Section 7(a)(2)(B) of the Securities Act. ☐

The registrant hereby amends this registration statement on such date or dates as may be necessary to delay its effective date until the registrant shall file a further amendment ~~that~~which specifically states that this registration statement shall thereafter become effective in accordance with Section 8(a) of the Securities Act of 1933, as amended, or until ~~this~~the registration statement shall become effective on such date as the Securities and Exchange Commission, acting pursuant to said Section 8(a), may determine.

~~The~~Table ~~information~~of in this preliminary prospectus is not complete and may be changed. These securities may not be sold until the registration statement filed with the Securities and Exchange Commission is effective. This preliminary prospectus is not an offer to sell these securities and it is not soliciting an offer to buy these securities in any state where the offer or sale is not permitted. Contents

~~PRELIMINARY~~The ~~PROSPECTUS~~information ~~SUBJECT~~in TOthis ~~COMPLETION,~~prospectus ~~DATED~~is ~~July~~not ~~14,~~complete ~~2023~~and may be changed. The Selling Stockholders may not sell these securities until the registration statement filed with the Securities and Exchange Commission is effective. This prospectus is not an offer to sell these securities and it is not soliciting an offer to buy these securities in any jurisdiction where the offer or sale is not permitted.

UpPROSPECTUS ~~to Shares~~SUBJECT ofTO ~~Common~~COMPLETION, ~~Stock~~DATED NOVEMBER 9, 2023

~~Common~~Up ~~Warrants~~ to ~~purchase~~76,249,080 upShares ~~to shares~~ of ~~Common Stock~~

~~Pre-Funded Warrants to purchase up to shares of~~ Common Stock

UpPursuant to this prospectus, the selling stockholders identified herein, or their permitted transferees that may be identified in this prospectus or by prospectus supplement (the “Selling Stockholders”), are offering on a resale basis, from time to time, up to 76,249,080 shares of ~~Common~~common ~~Stock~~stock, ~~underlying~~par value $0.001 per share, of Athersys, Inc. (the ~~Common~~“Company”), consisting of (i) 56,249,080 shares of common stock that are issuable upon the exercise of warrants to purchase shares of common stock at an original exercise price of $0.1395 per share and a current exercise price (after a reduction in the exercise price agreed to on October 30, 2023) of $0.01 per share (the “Inducement Warrants”) issued by us to the Selling Stockholders in a private placement of the Inducement Warrants which closed on October 16, 2023 pursuant to a letter agreement dated October 11, 2023 (the “Inducement Letter”), and (ii) 20,000,000 shares of common stock that are issuable upon exercise of certain warrants (the “October 30, 2023 Warrants” and, together with the Inducement Warrants, the “Subject Warrants”) to purchase shares of common stock at an exercise price of $0.01 per share issued by the Company on October 30, 2023 in a transaction pursuant to an offer letter dated October 30, 2023 (the “Letter Agreement”).

UpWe are not offering any shares of our common stock for sale by us under this prospectus. We are registering the shares of common stock covered by this prospectus to be sold by the Selling Stockholders under the terms of the Inducement Letter and the Letter Agreement. We will not receive any proceeds from the sale of shares of ~~Common~~common ~~Stock~~stock ~~underlying~~offered for resale by the ~~Pre-Funded~~Selling ~~Warrants~~Stockholders.

WeThe ~~are~~Selling ~~offering~~Stockholders upmay tosell ~~$ shares (~~the ~~“Shares”)~~shares of our common stock, ~~par~~covered ~~value~~by ~~$0.001~~this ~~per~~prospectus ~~share,~~from ~~together~~time ~~with common warrants~~ to ~~purchase~~time upthrough ~~to shares~~any of ~~common stock (~~the ~~“Common~~means ~~Warrants”)~~described atin anthe ~~assumed~~section ~~combined public offering price~~ of ~~$ ,~~this ~~which~~prospectus isentitled ~~the~~“Plan ~~last sale price~~ of ~~our~~Distribution.” ~~common stock as reported by~~ The ~~Nasdaq~~prices ~~Capital~~at ~~Market~~which ~~(“Nasdaq” or~~ the ~~"Nasdaq~~Selling ~~Capital~~Stockholders ~~Market")~~may ~~on ,~~sell ~~2023.~~the ~~The~~shares ~~Shares and Common Warrants are immediately separable and~~ will be ~~issued~~determined ~~separately~~by inthe ~~this~~prevailing ~~offering.~~market ~~Our~~price ~~common~~for ~~stock~~the isshares ~~currently~~or ~~listed~~in onnegotiated ~~Nasdaq and trades under the symbol “ATHX~~transactions.”

WeOur are offering to certain purchasers whose purchase of Shares in this offering would otherwise result in the purchaser, together with its affiliates and certain related parties, beneficially owning more than 4.99% of our outstanding shares of common stock ~~immediately~~is ~~following~~quoted ~~the~~on ~~consummation of this offering,~~ the ~~opportunity~~Pink toOpen ~~purchase,~~Market iftier ~~any~~operated ~~such~~by ~~purchaser~~OTC soMarkets ~~chooses~~Group, ~~pre-funded~~Inc. ~~warrants~~ (the “~~Pre-Funded~~OTC ~~Warrants~~Pink”), under inthe ~~lieu~~symbol of“ATHX.” ~~Shares~~On ~~that~~November ~~otherwise~~8, ~~would result in such purchaser’s beneficial ownership exceeding 4.99% (or~~2023, at the ~~election~~last ofreported ~~the~~sale ~~purchaser,~~price ~~9.99%)~~ of our ~~outstanding shares of~~ common stock. ~~Each~~on ~~Pre-Funded~~the ~~Warrant~~OTC isPink was ~~exercisable~~$0.275 ~~for~~per ~~one~~ share. ofWe ~~common~~have ~~stock~~applied atto anhave ~~exercise~~our ~~price~~common ofstock ~~$0.0001,~~quoted ~~and~~on the ~~assumed~~OTCQB ~~purchase~~Venture ~~price~~Market, ~~for~~but athere ~~Pre-Funded Warrant and accompanying Common Warrant~~ is ~~$ .~~no ~~The~~assurance ~~Pre-Funded~~that ~~Warrants~~our ~~and~~application ~~accompanying Common Warrants are immediately separable and~~ will be ~~issued~~accepted ~~separately~~or inas ~~this~~to ~~offering. The Pre-Funded Warrants are immediately exercisable and may be exercised at any time until all of~~ the ~~Pre-Funded~~timing ~~Warrants are exercised in full. For each Pre-Funded Warrant we sell, the number~~ of ~~Shares~~any ~~we are offering will be decreased on a one-for-one basis~~acceptance.

~~There~~This isprospectus nodescribes ~~established~~the ~~trading~~general ~~market~~manner ~~for~~in ~~the~~which ~~Pre-Funded~~shares ~~Warrants~~of orcommon ~~Common~~stock ~~Warrants,~~may be offered and wesold doby ~~not~~any ~~expect~~Selling aStockholders. ~~market~~When tothe ~~develop.~~Selling InStockholders ~~addition~~sell shares of common stock under this prospectus, we domay, ~~not~~if ~~intend~~necessary toand ~~list~~required by law, provide a prospectus supplement that will contain specific information about the ~~Pre-Funded~~terms ~~Warrants~~of orthat ~~Common~~offering. ~~Warrants~~Any onprospectus ~~Nasdaq,~~supplement ~~any~~may ~~other~~also ~~national~~add ~~securities~~to, ~~exchange~~update, modify, or ~~any~~replace ~~other~~information ~~trading~~contained ~~system~~in this prospectus. ~~Without~~We anurge ~~active~~you ~~trading~~to ~~market,~~carefully ~~the~~read ~~liquidity~~this ofprospectus, ~~the~~any ~~Pre-Funded~~prospectus ~~Warrants~~supplement, and ~~Common~~any ~~Warrants~~documents ~~may~~we beincorporate ~~limited~~by reference into this prospectus before you make your investment decision.

WeINVESTING ~~have~~IN ~~engaged~~OUR ~~A.G.P./Alliance~~SECURITIES ~~Global~~INVOLVES ~~Partners (whom we refer to herein as the “Placement Agent”) to act as our exclusive placement agent in connection with the securities offered by this prospectus~~RISKS. ~~The~~YOU ~~Placement~~SHOULD ~~Agent~~REVIEW ~~has~~CAREFULLY noTHE ~~obligation~~RISKS toAND ~~buy~~UNCERTAINTIES ~~any~~DESCRIBED ofUNDER ~~the~~THE ~~securities~~HEADING ~~from~~“RISK usFACTORS” orBEGINNING toON ~~arrange~~PAGE ~~for~~3 OF ~~the~~THIS ~~purchase~~PROSPECTUS orAND ~~sale~~UNDER ofSIMILAR ~~any~~HEADINGS ~~specific~~IN ~~number~~THE orOTHER ~~dollar~~DOCUMENTS ~~amount~~THAT ofARE ~~securities~~INCORPORATED ~~but~~BY ~~has~~REFERENCE ~~agreed~~INTO toTHIS ~~use its reasonable best efforts to arrange for the sale of the securities offered by this prospectus~~PROSPECTUS. ~~We have agreed to pay the Placement Agent a fee based upon the aggregate gross proceeds raised in this offering as set forth in the table below.~~

~~There~~NEITHER isTHE noSECURITIES ~~minimum~~AND ~~number~~EXCHANGE ofCOMMISSION ~~securities~~NOR orANY ~~minimum~~STATE ~~aggregate~~SECURITIES ~~amount~~COMMISSION ofHAS ~~proceeds~~APPROVED ~~for~~OR ~~this~~DISAPPROVED ~~offering~~OF toTHESE ~~close.~~SECURITIES WeOR ~~expect~~PASSED ~~this~~UPON ~~offering~~THE toADEQUACY beOR ~~completed~~ACCURACY ~~not~~OF ~~later~~THIS than two (2) business days following the commencement of this offering and we will deliver all securities to be issued in connection with this offering delivery versus payment (“DVP”)/receipt versus payment (“RVP”) upon receipt of investor funds received by usPROSPECTUS. ~~Accordingly,~~ANY ~~neither~~REPRESENTATION weTO ~~nor~~THE ~~the~~CONTRARY ~~Placement~~IS ~~Agent~~A ~~have~~CRIMINAL made any arrangements to place investor funds in an escrow account or trust account since the Placement Agent will not receive investor funds in connection with the sale of the securities offered hereunderOFFENSE.

The ~~final~~date ~~public offering price~~ of ~~the securities sold in~~ this ~~offering~~prospectus ~~will~~is ~~be determined between us~~__________, ~~the Placement Agent, and the investors in the offering and may be at a discount to the current market price of our common stock~~2023. ~~Therefore, the recent market price used throughout this prospectus will not be indicative of the actual public offering price.~~

~~Investing~~Table ~~in our securities involves a high degree~~ of ~~risk. See the “Risk Factors” section beginning on page 13 of this prospectus for a discussion of information that should be considered in connection with an investment in our securities.~~ Contents

	Per Share and accompanying Common Warrant	Per Pre- Funded Warrant and accompanying Common Warrant	Total
Public offering price(1)	$	$	$
Placement Agent’s fees (2)	$	$	$
Proceeds to us, before expenses(3)	$	$	$

(1) The combined public offering price is $ per share of common stock and accompanying Common Warrant and $ per Pre-Funded Warrant and accompanying Common Warrant.

(2) We have agreed to pay the Placement Agent a total cash fee equal to 7.0% of the gross proceeds of the offering. We have also agreed to reimburse the Placement Agent for its accountable offering-related legal expenses in an amount up to $80,000 and pay the Placement Agent a non-accountable expense allowance of up to $75,000. See “Plan of Distribution” for a description of the compensation payable to the Placement Agent.

(3) Does not include potential proceeds from the exercise of the Common Warrants and/or Pre-Funded Warrants for cash, if any.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities, or determined if this prospectus is truthful or complete. Any representation to the contrary is a criminal offense.

Delivery of the securities is expected to be made on or about                           , 2023.

Sole Placement Agent

A.G.P.

The date of this prospectus is , 2023

TABLE OF CONTENTS

PROSPECTUS SUMMARY	5
	Page
SUMMARY FINANCIAL DATA	12
DISCLOSURE REGARDING FORWARD-LOOKING STATEMENTS	ii
RISK FACTORS	13
ABOUT THIS PROSPECTUS	1
CAUTIONARY NOTE REGARDING FORWARD-LOOKING STATEMENTS	20
SUMMARY	2
USE OF PROCEEDS	21
RISK FACTORS	3
DIVIDEND POLICY	22
USE OF PROCEEDS	5
CAPITALIZATION	23
DIVIDEND POLICY	5
DILUTION	25
DESCRIPTION OF SECURITIES	6
DESCRIPTION OF CAPITAL STOCK	27
SELLING STOCKHOLDERS	7
DESCRIPTION OF SECURITIES WE ARE OFFERING	28
PLAN OF DISTRIBUTION	8
PLAN OF DISTRIBUTION	31
LEGAL MATTERS	11
LEGAL MATTERS	33
EXPERTS	11
EXPERTS	33
WHERE YOU CAN FIND MORE INFORMATION	11
INCORPORATION OF CERTAIN INFORMATION BY REFERENCE	33
INFORMATION WE INCORPORATE BY REFERENCE	12
WHERE YOU CAN FIND MORE INFORMATION	34

WeNo ~~are~~dealer, ~~responsible for the information contained in this prospectus. We have not~~salesperson, ~~and~~or ~~the~~other ~~Placement~~person ~~Agent~~is ~~has not,~~ authorized ~~anyone~~ to ~~provide~~give ~~you~~any ~~with~~information ~~any~~or ~~other~~to ~~information~~represent ~~other~~anything ~~than~~not contained in this prospectus,. ~~and~~You wemust ~~take no responsibility for, and the Placement Agent has~~ not ~~taken~~rely ~~responsibility~~on ~~for,~~ any ~~other~~unauthorized information ~~others~~or ~~may give you~~representations. WeThis ~~are~~prospectus ~~not, and the Placement Agent~~ is ~~not, making~~ an offer to sell ~~these~~only the securities inoffered ~~any~~hereby, ~~jurisdiction~~but ~~where~~only ~~the~~under ~~offer~~circumstances orand ~~sale~~in isjurisdictions ~~not~~where ~~permitted.~~it ~~You~~is ~~should~~lawful ~~not~~to ~~assume~~do ~~that~~so. ~~the~~The information contained in this prospectus is ~~accurate~~current only as of ~~any date other than~~ its date. ~~Our business, financial condition, results of operations and prospects may have changed since that date.~~

~~PROSPECTUS~~Table ~~SUMMARY~~of Contents

~~This~~DISCLOSURE ~~summary~~REGARDING highlights certain information appearing elsewhere in or incorporated by reference into this prospectus. This summary is not complete and does not contain all of the information you should consider prior to investing in the securities offered hereby. After you read this summary, you should read and consider carefully the more detailed information and financial statements and related notes that we include or incorporate by reference in this prospectus, including the information incorporated by reference from our most recent Annual Report on Form 10FORWARD-KLOOKING ~~and any subsequent Quarterly Reports on Form 10-Q or Current Reports on Form 8-K. If you invest in our securities, you are assuming a high degree of risk.~~STATEMENTS

~~References~~This inprospectus, ~~this~~including the documents incorporated by reference, contains, and any prospectus supplement may contain, “forward-looking statements” as defined in the Private Securities Litigation Reform Act of 1995 that involve risks and uncertainties. These forward-looking statements relate to, among other things, the ~~terms~~timing of initiation of new clinical sites and patient enrollment in our clinical trials, the expected timetable for development of our product candidates, our growth strategy, and our future financial performance, including our operations, economic performance, financial condition, prospects, and other future events. We have attempted to identify forward-looking statements by using such words as “weanticipates,” “usbelieves,” or“can,” “~~the~~continue,” ~~Company~~“could,” or“estimates,” ~~other~~“expects,” ~~similar~~“intends,” ~~terms~~“may,” ~~mean~~“plans,” ~~Athersys~~“potential,” ~~Inc~~“should,” “suggest,” “will,” or other similar expressions. ~~and~~These ~~its~~forward-looking ~~consolidated~~statements ~~subsidiaries,~~are ~~unless~~only wepredictions ~~state~~and ~~otherwise~~are orlargely ~~the~~based ~~context~~on ~~indicates~~our ~~otherwise.~~current expectations.

~~Company~~In ~~Overview~~addition, a number of known and unknown risks, uncertainties, and other factors could affect the accuracy of these statements. Some of the more significant known risks that we face are the risks and uncertainties inherent in the process of discovering, developing, and commercializing products that are safe and effective for use as therapeutics, including the uncertainty regarding market acceptance of our product candidates and our ability to generate revenues. The following risks and uncertainties may cause our actual results, levels of activity, performance, or achievements to differ materially from any future results, levels of activity, performance, or achievements expressed or implied by these forward-looking statements:

We● ~~are~~our aability ~~biotechnology~~to ~~company~~raise ~~that~~capital isto ~~focused~~fund ~~primarily~~our operations in the ~~field~~near ofterm ~~regenerative~~and ~~medicine.~~long Weterm, ~~are~~including ~~committed~~our ability to ~~the~~obtain ~~discovery~~funding through public or private equity offerings, debt financings, collaborations and ~~development~~licensing ofarrangements ~~best-in-class~~or ~~therapies~~other ~~designed~~sources, on terms acceptable to ~~extend~~us or at all, and ~~enhance~~to ~~the~~continue ~~quality~~as ofa ~~human~~going ~~life~~concern; ● our collaborators’ ability and ~~have~~willingness ~~established~~to acontinue ~~portfolio~~to fulfill their obligations under the terms of ~~therapeutic~~our ~~product~~collaboration ~~development~~agreements ~~programs~~and generate sales related to ~~address~~our ~~significant~~technologies; ~~unmet~~● ~~medical~~the ~~needs~~possibility inof ~~multiple~~unfavorable ~~disease~~results ~~areas.~~from ~~Our~~ongoing and additional clinical trials involving MultiStem®; ~~(invimestrocel)~~● ~~cell~~the ~~therapy,~~risk that positive results in a ~~patented~~clinical ~~and~~trial ~~proprietary~~may ~~allogeneic~~not ~~stem~~be ~~cell~~replicated ~~product~~in ~~candidate,~~subsequent isor ~~our~~confirmatory ~~lead~~trials ~~platform~~or ~~product~~success ~~and~~in isan ~~currently~~early stage clinical trial may not be predictive of results in ~~late-~~later stage or large scale clinical ~~development.~~trials; ~~Our~~● ~~most~~the ~~advanced~~timing ~~therapeutic~~and ~~program~~nature isof ~~focused~~results onfrom MultiStem clinical trials, including the MASTERS-2 Phase 3 clinical trial evaluating the administration of MultiStem for the treatment of ischemic stroke; ● our ability to meet milestones and earn royalties under our collaboration agreements, ~~which~~including isthe ~~currently~~success ~~being~~of ~~evaluated~~our incollaboration awith ~~pivotal~~Healios; ~~Phase~~● 3the success of our MACOVIA clinical trial ~~ongoing~~evaluating inthe administration of MultiStem for the ~~United~~treatment ~~States~~of ~~under~~ARDS ainduced ~~Special~~by ~~Protocol~~COVID-19 ~~Assessment~~and ~~agreement~~other ~~(“SPA”)~~pathogens, ~~from~~and the ~~U.S.~~MATRICS-1 ~~Food~~clinical ~~and~~trial ~~Drug~~being ~~Administration~~conducted (with The University of Texas Health Science Center at Houston evaluating the ~~“FDA”),~~treatment inof ~~Europe~~patients ~~and~~with serious traumatic injuries; ● the availability of product sufficient to meet commercial demand shortly following any approval; ● the possibility of delays in, ~~certain~~adverse ~~other~~results ~~international~~of, ~~locations.~~and ~~Our~~excessive ~~current~~costs ~~clinical~~of the development ~~programs~~process; ~~are~~● ~~focused~~our onability ~~treating~~to ~~critical~~successfully ~~care~~initiate and ~~other~~complete ~~conditions~~clinical ~~where~~trials ~~current~~of ~~standard~~our product candidates; ● the possibility of ~~care~~delays, iswork ~~limited~~stoppages or ~~inadequate~~interruptions ~~for~~in ~~many~~manufacturing ~~patients.~~by ~~These~~third ~~represent~~parties ~~major~~or ~~areas~~us, ofsuch ~~clinical~~as ~~need~~due to material supply constraints, ascontaminations, ~~well~~operational asrestrictions ~~substantial~~due ~~commercial~~to ~~opportunities.~~COVID-19 or other public health emergencies, labor constraints, regulatory issues or other factors that could negatively impact our trials and the trials of our collaborators;

We● ~~believe~~uncertainty regarding market acceptance of our product candidates and our ability to generate revenues, including MultiStem cell therapy ~~product~~for ~~candidate~~neurological, ~~represents~~inflammatory aand ~~potential~~immune, ~~breakthrough~~cardiovascular and other critical care indications; ● changes in ~~the~~external ~~field~~market offactors; ~~regenerative~~● ~~medicine~~changes ~~and~~in ~~stem~~our ~~cell~~industry’s ~~therapy,~~overall ~~and~~performance; ~~could~~● bechanges ~~used~~in toour ~~treat~~business astrategy; ~~range~~● ofour ~~disease~~ability ~~indications.~~to ~~MultiStem~~protect ~~received~~and ~~Regenerative~~defend ~~Medicine~~our ~~Advanced~~intellectual ~~Therapy~~property ~~(“RMAT”),~~and ~~designation~~related ~~for~~business operations, including the ~~treatment~~successful prosecution of ~~both~~our ~~ischemic~~patent ~~stroke~~applications and ~~acute~~enforcement ~~respiratory~~of ~~distress~~our ~~syndrome~~patent ~~(“ARDS”).~~rights, ~~MultiStem~~and ~~treatment~~operate ~~has~~our ~~shown~~business ~~the~~in ~~potential~~an toenvironment ~~enhance~~of ~~tissue~~rapid ~~repair~~technology and ~~healing~~intellectual inproperty ~~multiple~~development; ~~ways,~~● ~~including~~our ~~reducing~~possible ~~inflammatory~~inability ~~damage,~~to ~~protecting~~realize ~~tissue~~commercially ~~that~~valuable isdiscoveries atin ~~risk~~our ~~following~~collaborations ~~acute~~with orpharmaceutical ~~ischemic~~and ~~injury,~~other ~~and~~biotechnology ~~promoting~~companies; ~~formation~~● the success of our efforts to enter into new ~~blood~~strategic ~~vessels~~partnerships inand ~~regions~~advance ofour ~~ischemic~~programs; ~~injury.~~● ~~These~~our ~~cells~~possible ~~appear~~inability to beexecute ~~responsive~~our tostrategy ~~the~~due ~~environment~~to changes in ~~which~~our ~~they~~industry ~~are~~or ~~administered,~~the byeconomy ~~homing~~generally; to● ~~sites~~changes ofin ~~injury~~productivity and~~/or~~ ~~organs~~reliability ~~involved~~of insuppliers; ~~injury~~● ~~response~~the ~~and~~success ~~providing~~of ~~active~~our ~~disease~~competitors ~~response.~~and ~~These~~the ~~cells~~emergence ~~also~~of ~~produce~~new ~~proteins~~competitors; ~~that~~● ~~may~~our ~~provide~~ability ~~benefit~~to inmaintain ~~both~~quotation ~~acute~~of ~~and~~our ~~chronic~~common ~~conditions~~stock ~~and~~on ~~regulate~~the ~~other~~OTC ~~cell~~Pink; ~~types.~~● Inour ~~contrast~~ability to ~~traditional~~identify, ~~pharmaceutical~~evaluate, ~~products~~and orcomplete ~~biologics~~any strategic alternative that ~~generally~~yields ~~act~~value ~~through~~for aour ~~single~~stockholders; ~~biological~~and ~~mechanism~~● ofthe ~~action,~~risks ~~MultiStem~~described ~~cell~~in ~~therapy~~our ~~may~~Annual ~~enhance~~Report ~~healing~~on ~~and~~Form ~~tissue~~10-K ~~repair~~for ~~through~~the ~~several~~year ~~distinct~~ended ~~mechanisms~~December ~~acting~~31, in2022, ~~parallel~~under Item 1A, ~~resulting~~“Risk inFactors” aand ~~more~~our ~~effective~~other ~~therapeutic~~filings ~~response~~with the SEC.

WeAny ~~believe~~forward-looking ~~the~~statement ~~therapeutic~~you ~~and~~read ~~commercial~~in ~~potential~~this ~~for~~prospectus, ~~MultiStem~~any ~~cell~~prospectus ~~therapy~~supplement or any document incorporated by reference reflects our current views with respect to befuture ~~very~~events ~~broad,~~and ~~applying~~is subject to ~~many~~these ~~areas~~and ofother ~~significant~~risks, ~~unmet~~uncertainties ~~medical~~and ~~need~~assumptions relating to our operations, operating results, growth strategy and liquidity. Although we ~~are~~currently ~~pursuing~~believe ~~opportunities~~that inthe ~~several~~expectations ~~potential~~reflected ~~multi~~in the forward-~~billion~~looking ~~dollar~~statements ~~markets~~are reasonable, we cannot guarantee our future results, levels of activity or performance. ~~While~~You ~~traditional~~should ~~pharmaceuticals~~not ~~and~~place ~~biologic~~undue ~~therapies~~reliance ~~typically~~on ~~may~~these beforward-looking ~~used~~statements tobecause ~~treat~~such statements speak only aas ~~single~~of ~~disease~~the ordate awhen ~~narrowly~~made. ~~defined~~We ~~set~~undertake no obligation to publicly update forward-looking statements, whether as a result of ~~related~~new ~~conditions~~information, ~~MultiStem~~future ~~cell~~events ~~therapy~~or ~~may~~otherwise, ~~have~~except ~~far~~as ~~broader~~otherwise ~~potential~~required ~~and~~by ~~could~~law. beYou ~~developed~~are advised, however, to consult any further disclosures we make on related subjects in ~~different~~our ~~formulations~~reports on Forms 10-Q, 8-K and ~~with~~10-K ~~different~~furnished ~~delivery~~to ~~approaches~~the SEC. You should understand that it is not possible to ~~effectively~~predict ~~treat~~or identify all risk factors. Consequently, you should not consider any such list to be a ~~wide~~complete ~~range~~set of ~~disease~~all ~~indications~~potential risks or uncertainties.

~~The~~Any ~~MultiStem~~document ~~product~~incorporated ~~candidate~~by ~~under~~reference ~~development~~or ~~may~~any beprospectus ~~unique~~supplement ~~among~~may ~~regenerative~~also ~~medicine~~contain ~~approaches~~statistical ~~because~~data itand ~~has~~estimates ~~the~~we ~~potential~~obtained tofrom beindustry ~~manufactured~~publications ~~on a large scale, can be administered in an “off-the-shelf” manner with minimal processing,~~ and ~~has~~reports ~~the~~generated ~~potential to augment healing~~ by ~~providing~~third ~~biological~~parties. ~~potency~~Although ~~and~~we ~~therapeutic~~believe ~~effects~~ that ~~other~~the ~~cell~~publications ~~therapy approaches may not be able to achieve. Additionally, MultiStem treatment has consistently demonstrated good tolerability in both preclinical~~ and ~~clinical~~reports ~~studies.~~are ~~Like conventional drugs and biologics~~reliable, ~~the product candidate is cleared from the body over time, which~~ we ~~believe~~have ~~may enhance product safety relative to other types of stem cell therapy. While the product candidate does~~ not ~~permanently~~independently ~~engraft~~verified intheir ~~the patient, the therapeutic effects of treatment with MultiStem cells appear to be durable based on both clinical and preclinical results~~data.

We have evaluated the use of MultiStem cell therapy as a potential treatment in several disease areas. Working with an international network of leading investigators and prominent research and clinical institutions, and through our own internal efforts, we have explored the potential for MultiStem cell therapy to be used as a treatment of acute and chronic forms of neurological conditions or injury, inflammatory and immune disorders, certain pulmonary conditions and cardiovascular disease. We have advanced several MultiStem programs into clinical development, targeting areas of significant medical need and major commercial market opportunities, and have two ongoing clinical trials in the critical care area. We have a collaboration with HEALIOS K.K. (“Healios”), to develop and commercialize MultiStem for the treatment of certain indications in Japan. Among other things, Healios has a license to our technology and is responsible for the development and commercialization of MultiStem for ischemic stroke and ARDS in Japan on an exclusive basis.ii

~~Our~~Table ~~lead program is our pivotal Phase 3 clinical trial to evaluate the potential for MultiStem treatment~~ of patients who have suffered neurological damage from an ischemic stroke entitled, “MultiStem Administration for Stroke Treatment and Enhanced Recovery Study-2,” or MASTERS-2. The results from our completed Phase 2 study demonstrated favorable tolerability for MultiStem, consistent with the results from prior studies. Though the Phase 2 study did not achieve the primary endpoints for the intent-to-treat population, MultiStem treatment was associated with lower rates of mortality and life-threatening adverse events, infections and pulmonary events, and a reduction in hospitalization and time in the intensive care unit (“ICU”). In addition, analyses show that patients who received MultiStem treatment earlier in the study’s treatment window (24 to 36 hours post-stroke, in accordance with the original study protocol) had better recovery in comparison to placebo. Furthermore, analysis of biomarker data obtained from samples of study subjects indicated that MultiStem treatment reduced post-stroke inflammation compared to placebo, and the results suggest that this effect was more pronounced for subjects who received MultiStem earlier within the treatment window. This effect is consistent with our hypothesis regarding mechanisms of action and related preclinical data, and with the clinical data suggesting faster and improved recovery for MultiStem-treated patients relative to current standard of care.Contents

5ABOUT THIS PROSPECTUS

~~The~~This ~~one-year~~prospectus ~~follow-up~~is ~~data~~part ~~from~~of ~~the~~a ~~Phase~~registration 2statement ~~trial demonstrated~~ that ~~MultiStem-treated~~we ~~subjects~~have onfiled ~~average~~with ~~continued~~the toU.S. ~~improve~~Securities ~~through one year~~ and ~~had~~Exchange aCommission ~~significantly~~(the ~~higher rate of~~ “~~Excellent Outcome,~~SEC” ~~as defined below, compared to placebo subjects at one year when evaluating all of the intent-to-treat subjects enrolled in the study~~). ~~Achievement~~Under ofthis anregistration ~~Excellent Outcome is important because it means that a patient has substantially improved (i.e.~~statement, ~~receiving an “Excellent” score in each of~~ the ~~three~~Selling ~~clinical~~Stockholders ~~rating~~may ~~scales~~sell ~~used~~from totime ~~assess patient improvement) and has regained the ability~~ to ~~live~~time ~~and function independently with a high quality of life. The relative improvement~~ in ~~Excellent~~one ~~Outcome~~or ~~was even~~ more ~~pronounced~~offerings in the ~~study~~common ~~subjects~~stock ~~who~~described ~~received~~in ~~MultiStem~~this ~~treatment within 36 hours of the stroke~~prospectus. IfYou ~~the~~should ~~MultiStem~~read ~~cell~~this ~~therapy~~prospectus ~~candidate~~and isany ~~proven~~applicable ~~effective~~prospectus ~~in our ongoing Phase 3 registrational study~~supplement, ~~and~~together ifwith ~~it receives a marketing authorization from~~ the ~~FDA,~~information ~~this~~incorporated ~~treatment~~herein ~~window~~by ~~and~~reference ~~its~~as ~~favorable~~described ~~administration~~under ~~profile~~the ~~would~~headings ~~make~~“Where ~~this~~You ~~therapy~~Can ~~available~~Find toMore ~~most~~Information” ~~ischemic~~and ~~stroke~~“Information ~~patients~~We inIncorporate ~~contrast~~by ~~to other therapies (e~~Reference.~~g., tissue plasminogen activator, or tPA, or mechanical thrombectomy), which have shorter treatment windows or are limited to certain patients.~~”

~~Our~~You ~~MASTERS-2~~should ~~trial~~rely ~~treating~~only ~~ischemic~~on ~~stroke patients is ongoing in~~ the ~~United~~information ~~States and certain other international locations. We received agreement from the FDA under a SPA~~ that ~~the design and planned analysis of MASTERS-2 adequately address the objectives necessary to support a regulatory submission. It is possible that following MASTERS-2~~ we ~~will~~have ~~conduct~~provided ~~either a post-registry study~~ or aincorporated ~~confirmatory~~by ~~study,~~reference ~~depending~~in onthis ~~the~~prospectus ~~strength~~ and ~~robustness~~any ofapplicable ~~the~~prospectus ~~study outcome~~supplement. ~~The~~We ~~FDA~~have ~~granted~~not usauthorized, ~~Fast~~nor ~~Track~~has ~~and~~any ~~RMAT~~Selling ~~designations~~Stockholder ~~for~~authorized, ~~our~~any ~~clinical~~dealer, ~~product~~salesman, ~~for~~or ~~the~~other ~~treatment~~person ofto ~~ischemic~~give ~~stroke.~~any ~~Fast~~information ~~Track~~or ~~is an important designation given~~ to ~~qualified~~make ~~investigational~~any ~~therapies~~representation ~~that~~other ~~show~~than ~~promise~~those incontained ~~providing~~or ~~benefit~~incorporated toby ~~patients~~reference in ~~areas~~this ofprospectus ~~significant~~or ~~unmet~~any ~~medical~~applicable ~~need~~prospectus supplement. ~~Fast~~You ~~Track~~should ~~designation~~not ~~allows~~rely ~~for~~upon anany ~~expedited~~information ~~regulatory~~or ~~review~~representation ~~process~~not ~~after~~contained ~~the~~or ~~clinical~~incorporated ~~data~~by isreference ~~submitted to help speed development of promising therapies to the market~~ in ~~order~~this toprospectus ~~help~~or ~~patients~~any inaccompanying ~~areas~~prospectus ~~where current standard of care is limited~~supplement. ~~Such~~We ~~designation for a new biologic product means that the FDA will~~ take ~~such~~no ~~actions~~responsibility ~~as are appropriate to expedite the development and review of our application to approve the product, and specifically, under Fast Track designation, the program becomes eligible~~ for ~~rolling submission~~, ~~accelerated approval~~ and ~~priority~~can ~~review,~~provide ~~facilitating~~no aassurance ~~timely~~as regulatory review. This program subsequently received the RMAT designation from the FDA that was established under the 21st Century Cures Legislation. The RMAT designation may be obtained for eligible cell therapy and other regenerative medicine and advanced therapies when the FDA agrees that preliminary clinical evidence indicates that the therapy has demonstrated the potential to ~~effectively address unmet medical needs for a serious or life-threatening disease or condition. The RMAT designation is~~ the ~~equivalent~~reliability of ~~the non-regenerative medicine product’s Breakthrough Therapy designation~~, ~~and~~any ~~designated~~other ~~products~~information ~~benefit~~that ~~from~~others ~~all~~may ~~Breakthrough~~give ~~Therapy features, in addition to eligibility for filing for registration under accelerated approval path~~you. The designation also enables sponsors to discuss with the FDA multidisciplinary strategic development plans, including expediting manufacturing development plans for commercialization and supporting priority review and rolling submission.

~~The~~This ~~design~~prospectus ofand ~~MASTERS-2~~any ~~has~~accompanying ~~also~~prospectus ~~received~~supplement ado ~~Final~~not ~~Scientific~~constitute ~~Advice~~an ~~positive~~offer ~~opinion~~to ~~from~~sell or the ~~European~~solicitation ~~Medicines~~of ~~Agency~~an ~~(“EMA”),~~offer ~~representing~~to buy any securities other than the ~~EMA’s~~registered ~~agreement~~securities ~~that~~to ~~successful~~which ~~results~~they ~~from~~relate, nor do this prospectus and any accompanying prospectus supplement constitute an offer to sell or the ~~trial~~solicitation ~~could~~of ~~result~~an offer to buy securities in ~~registration~~any ~~and~~jurisdiction ~~marketing~~to ~~approval~~any ofperson ~~the~~to ~~MultiStem~~whom ~~cell~~it ~~therapy.~~is Weunlawful ~~have~~to ~~also~~make ~~received~~such ~~Advanced~~offer ~~Therapy~~or ~~Medicinal~~solicitation ~~Product~~in ~~(“ATMP”),~~such ~~Certificate~~jurisdiction. ~~for~~You ~~Quality~~should ~~Data~~not ~~from~~assume that the ~~EMA.~~information Wecontained ~~believe~~in ~~these~~this ~~designations~~prospectus ~~from~~or any applicable prospectus supplement is accurate on any date subsequent to the ~~FDA~~date ~~and~~set ~~EMA~~forth ~~could~~on ~~accelerate~~the front of the ~~development,~~document ~~regulatory~~or ~~review~~that ~~and~~any information we have incorporated by reference is correct on any date subsequent ~~commercialization~~to the date of ~~products~~the document incorporated by reference, ~~like~~even ~~MultiStem~~though ~~cell~~this ~~therapy~~prospectus ~~for~~or ~~ischemic~~any ~~stroke~~applicable ~~and~~prospectus ~~ARDS,~~supplement ifis ~~future~~delivered ~~clinical~~or ~~evaluation~~securities ~~demonstrates~~are ~~appropriate~~sold ~~safety~~on ~~and~~a ~~therapeutic~~later ~~effectiveness~~date.

~~Business~~References ~~Strategy~~in this prospectus to the terms “we,” “us,” or the “Company” or other similar terms mean Athersys, Inc. and its consolidated subsidiaries, unless we state otherwise or the context indicates otherwise.

Our principal business objective is to discover, develop and commercialize novel therapeutic products for disease indications that represent significant areas of clinical need and where we believe there is a substantial commercial opportunity. The key elements of our strategy are outlined below:1

•Table ~~Advance our Lead Programs through Clinical Developments to Registration and Commercialization. We are focused on the design and execution~~ of clinical studies (e.g., ischemic stroke and trauma) intended to enable product registration in major markets. We are also engaged in activities intended to enable effective commercialization (e.g., preparation for scaled commercial manufacturing, product branding, product reimbursement and marketing strategies). We may partner with other companies to complete such development and preparation activities, and to market the product upon regulatory approval.Contents

• Efficiently Conduct Clinical Development to Establish Clinical Proof-of-Concept and Biological Activity for Other Applications of our Product Candidates. We conduct our clinical studies with the intent to establish safety and efficacy proof-of-concept and/or evidence of biological activity in a number of important disease areas where our cell therapies are expected to have benefit. Our strategy is to conduct well-designed studies beginning early in the clinical development process, thus establishing a robust foundation for later-stage development, partnering activity and expansion into complementary areas. We are committed to a rigorous clinical and regulatory approach, which we believe has helped us to advance our programs efficiently, providing high quality, transparent communications and regulatory submissions.SUMMARY

•This ~~Enter~~summary ~~into~~highlights ~~Arrangements~~certain ~~with~~information ~~Business~~appearing ~~Partners~~elsewhere toin ~~Accelerate~~this ~~Development~~prospectus and ~~Create~~in ~~Value~~the documents we incorporate by reference into this prospectus. InThe ~~addition~~summary tois ~~our~~not ~~internal~~complete ~~development~~and ~~efforts,~~does annot ~~important~~contain ~~part~~all of the information that you should consider before investing in our ~~strategy~~common isstock. toAfter ~~work~~you ~~with~~read ~~collaborators~~this summary, you should read and ~~partners~~carefully toconsider ~~accelerate~~the ~~product~~entire ~~development,~~prospectus ~~reduce~~and ~~our~~any ~~development~~prospectus ~~costs~~supplement and ~~broaden~~the more detailed information and financial statements and related notes that are incorporated by reference into this prospectus. If you invest in our ~~commercial~~shares, ~~access~~you are assuming a high degree of risk. The Company We ~~anticipate~~are a biotechnology company that ~~this~~is ~~strategy~~focused ~~will~~primarily ~~help~~in usthe tofield ~~develop~~of regenerative medicine. Our MultiStem® (invimestrocel) cell therapy, a ~~portfolio~~patented ofand ~~high-quality~~proprietary ~~product~~allogeneic ~~development~~stem ~~opportunities~~cell product candidate, ~~enhance~~is our lead platform product and is currently in clinical development in several therapeutic and ~~commercialization~~geographic ~~capabilities~~areas. Our most advanced program is an ongoing Phase 3 clinical trial for the treatment of ischemic stroke. Our current clinical development programs are focused on treating neurological conditions, inflammatory and ~~increase~~immune disorders, certain pulmonary conditions, cardiovascular disease and other conditions where the current standard of care is limited or inadequate for many patients, particularly in the critical care segment. Corporate Information We were incorporated in Delaware and our ~~ability~~headquarters are located at 3201 Carnegie Avenue, Cleveland, Ohio 44115. Our telephone number is (216) 431-9900. Our website is http://www.athersys.com. The information accessible on or through our website is not part of this prospectus, other than the documents that we file with the SEC that are specifically incorporated by reference into this prospectus. Background of the Subject Warrants We issued to ~~generate~~the ~~value~~Selling ~~from~~Stockholders common warrants to purchase shares of our ~~proprietary~~common ~~technologies~~stock on August 17, 2022, September 22, 2022, November 10, 2022, and August 21, 2023 (the “Prior Warrants”). ~~Historically~~On October 11, 2023, we ~~have~~and the Selling Stockholders entered into ~~licensing~~the ~~arrangements~~Inducement ~~with~~Letter, ~~companies~~pursuant ~~such~~to aswhich, ~~Healios~~we (i) issued the Inducement Warrants to purchase up to a number of shares of common stock equal to 200% of the number of warrant shares that would have otherwise been issued pursuant to the exercise of certain of the Prior Warrants, ~~Chugai~~at ~~Pharmaceutical~~an Coexercise price of $0.1395 per share, ~~Ltd~~and (ii) reduced the exercise price for the Prior Warrants to $0.,1395 ~~Pfizer~~per ~~Inc~~share during the period from the date of the Inducement Letter until 7:30 a.m., ~~Bristol-Myers~~Eastern ~~Squibb~~Time, ~~Company~~on October 12, ~~Johnson~~2023. &On ~~Johnson~~October 30, ~~Wyeth~~2023, ~~Pharmaceuticals~~we ~~Inc.~~and the Selling Stockholders entered into the Letter Agreement to (~~now~~1) ~~part~~reduce the exercise price of ~~Pfizer~~the Inducement Warrants from $0.1395 to $0.01 per share, (2) issue to the Selling Stockholders the October 30, ~~RTI~~2023 ~~Surgical~~Warrants; and (3) make the Inducement Warrants immediately exercisable. In addition, ~~Inc~~on October 30, 2023, the Company and the Selling Stockholders entered into an Amendment to the Inducement Warrants which amended the Inducement Warrants to reflect (i) the reduced exercise price of $0.01 per share, (ii) that the Inducement Warrants are immediately exercisable, and ~~others~~(iii) that the Inducement Warrants will terminate on October 30, 2028. The Offering

Common Stock Offered by the Selling Stockholders:		We are registering the resale by the Selling Stockholders named in this prospectus, or their permitted transferees, up to 76,249,080 shares of common stock consisting of (i) 56,249,080 shares of common stock that are issuable upon the exercise the Inducement Warrants issued by us to the Selling Stockholders in a private placement of the Inducement Warrants which closed on October 16, 2023 pursuant the Inducement Letter, and (ii) 20,000,000 shares of common stock that are issuable upon exercise of the October 30, 2023 Warrants issued by the Company on October 30, 2023 pursuant to the Letter Agreement.

Plan of Distribution:		The Selling Stockholders will determine when and how it will sell the common stock offered in this prospectus, as described in “Plan of Distribution” section of this prospectus.

Use of Proceeds:		We will not receive any proceeds from the sale of shares of our common stock by the Selling Stockholders.

Risk Factors:		Before investing in our securities, you should carefully read and consider the information set forth in the “Risk Factors” section of this prospectus and under similar headings in any amendments or supplements to this prospectus and the documents incorporated herein by reference.

OTC Pink symbol:		ATHX

•Throughout ~~Efficiently~~this ~~Explore~~prospectus, ~~New~~when ~~High~~we ~~Potential~~refer ~~Therapeutic~~to ~~Applications,~~the ~~Leveraging~~shares ~~Third-Party~~of ~~Research Collaborations and~~ our ~~Results~~common ~~from~~stock ~~Related~~being ~~Areas.~~registered ~~Our~~on ~~MultiStem~~behalf ~~cell~~of ~~therapy~~the ~~has~~Selling ~~shown~~Stockholders ~~promise~~for inoffer ~~many disease areas, including in treating neurological conditions, inflammatory~~ and ~~immune disorders~~sale, ~~certain~~we ~~pulmonary~~are ~~conditions,~~referring ~~cardiovascular~~to ~~disease, and other conditions where~~ the ~~current~~shares ~~standard~~ of ~~care is limited or inadequate for many patients. We have explored potential clinical indications where~~ our ~~therapies~~common ~~may~~stock ~~achieve~~that ~~best-in-class~~are ~~profile~~issuable ~~and~~upon ~~where~~exercise weof believe we can effectively address significant unmet medical needs. In order to achieve this goal, we leveraged collaborative research relationships with investigators from many leading research and clinical institutions across the ~~United~~Subject ~~States~~Warrants ~~and~~as ~~Europe,~~described ~~including~~under the ~~Cleveland~~above ~~Clinic,~~section ~~Case~~entitled ~~Western~~“—Background ~~Reserve University, the University~~ of ~~Minnesota,~~ the ~~Medical~~Subject ~~College~~Warrants.” ofWhen ~~Georgia~~we atrefer ~~Augusta~~to ~~University,~~ the ~~University~~Selling ofStockholders ~~Oregon~~in ~~Health~~this ~~Sciences Center~~prospectus, ~~the~~we ~~University~~are ofreferring ~~Pittsburgh~~to ~~Medical Center,~~ the ~~Katholieke~~Selling ~~Universiteit~~Stockholders ~~Leuven,~~identified ~~and~~in ~~the~~this ~~University~~prospectus ~~of Regensburg~~and, ~~among~~as ~~other institutions~~applicable, ~~with~~their ~~current research ongoing at UTHealth~~donees, ~~Maastricht University~~pledgees, ~~the University of Birmingham~~transferees, ~~and~~or ~~Newcastle~~other ~~University.~~successors-in-interest ~~Through~~selling ~~this~~shares ~~network~~ of ~~collaborations,~~common westock ~~have~~or ~~evaluated~~interests ~~MultiStem cell therapy~~ in ashares ~~range~~ of ~~preclinical~~common ~~models~~stock ~~that~~received ~~reflect~~after ~~various~~the ~~types~~date of ~~human~~this ~~disease~~prospectus orfrom ~~injury~~a ~~and~~Selling ~~have~~Stockholder ~~advanced~~as ~~several indications to~~ a ~~state of Investigational New Drug Application (“IND”)~~gift, ~~readiness~~pledge, ~~which could be quickly advanced upon via a future~~ partnership distribution, or ~~internally~~other ~~if we elect to move them into the clinical stage~~transfer.

• Continue to Expand our Intellectual Property Portfolio. We have a broad intellectual property estate that covers our proprietary products and technologies, as well as methods of production and methods of use. Our intellectual property is important to our business and we take significant steps to protect its value. We have ongoing research and development efforts through collaborative research activities with others, which aim to develop new technologies, applications and intellectual property and enable us to file patent applications that cover new applications of our existing technologies or product candidates, including MultiStem cell therapy as well as methods of production and method of use and other opportunities. We currently have approximately 360 patents related to our technologies, providing protection in the United States, Europe, Japan and other areas.2

~~Risk~~Table ~~Factor~~of ~~Summary~~Contents

Our ability to execute on our business strategy is subject to a number of risks, which are discussed more fully in the section “Risk Factors” of this prospectus and in our Annual Report on Form 10-K for the year ended December 31, 2022 and in any subsequent Quarterly Reports on Form 10-Q, each filed with the SEC and incorporated herein by reference. You should carefully consider these risks before making an investment in our common stock. These risks include, among others, the following:

• Our management will have broad discretion over the use of the proceeds to us from this offering and may apply it to uses that do not improve our operating results or the value of our securities.

• You will experience immediate and substantial dilution in the net tangible book value per share of the common stock you purchase.

• There is substantial doubt about our ability to continue as a going concern, which may affect our ability to obtain future financing and may require us to curtail our operations. We will need substantial additional funding to develop our products and for our future operations. If we are unable to obtain the funds necessary to do so, we may be required to further delay, scale back or eliminate our product development activities or may be unable to continue our business.

• If we are unable to raise capital, we could be forced to eliminate our product development programs, may be unable to continue our business and may need to file for protection under the bankruptcy laws.

• We have incurred losses since inception, and we expect to incur significant net losses in the foreseeable future and may never become profitable.

• We are heavily dependent on the successful development and commercialization of MultiStem products, and if we encounter delays or difficulties in the development of these product candidates, our business could be harmed.

• We have reduced the size of our organization, and we may encounter difficulties in managing our business as a result of this reduction, which could disrupt our operations. In addition, we may not achieve anticipated benefits and savings from the reduction.

• Our product candidates are currently in the development stage and we have no therapeutic products approved for sale. If we are unable to develop, obtain regulatory approval or market any of our product candidates, our financial condition will be negatively affected, and we may have to curtail or cease our operations.

• We may experience delays in clinical trials and regulatory approval relating to our products that could adversely affect our financial results and our commercial prospects for our pharmaceutical or stem cell products.

• Even if we obtain regulatory approval of any of our product candidates, the approved products may be subject to post-approval studies and will remain subject to ongoing regulatory requirements. If we fail to comply, or if concerns are identified in subsequent studies, our approval could be withdrawn, and our product sales could be suspended.

• We are not currently in compliance with Nasdaq’s continued listing requirements. If we are unable to comply with Nasdaq’s continued listing requirements, our common stock could be delisted, which could affect the price of our common stock and liquidity and reduce our ability to raise capital.

• If we inadvertently violate the guidelines pertaining to promotion and advertising of our clinical candidates or approved products, we may be subject to disciplinary action by the FDA’s Division of Drug Marketing, Advertising, and Communications or other regulatory bodies.

• Even if we or our collaborators receive regulatory approval for our products, those products may never be commercially successful.

• We may not successfully maintain our existing collaborative and licensing arrangements, or establish new ones, which could adversely affect our ability to develop and commercialize our product candidates.

• We rely on third parties to manufacture our MultiStem product candidate.

• Our ability to compete may decline if we are not successful in adequately protecting our patented and other proprietary technologies.

• We may not have adequate protection for our unpatented proprietary information, which could adversely affect our competitive position.

• Many potential competitors, including those who have greater resources and experience than we do, may develop products or technologies that make ours obsolete or noncompetitive.

• The availability, manner, and amount of reimbursement for our product candidates from government and private payers are uncertain, and our inability to obtain adequate reimbursement for any products could severely limit our product sales.

• Increased information technology security threats and more sophisticated and targeted computer crime could pose a risk to our systems, networks, and products.

Recent Developments

Forbearance, Restructuring and Settlement Agreement

On May 17, 2023, we entered into a Forbearance, Restructuring and Settlement Agreement (the “Forbearance Agreement”) with a supplier, which amends certain supply agreements between us and the supplier (the “Supply Agreements”). The Forbearance Agreement restructures our matured and unmatured liabilities owed to the supplier under the Supply Agreements, comprised of past due and current due obligations in the approximate amount of $20.9 million and future obligations in the approximate amount of $9.8 million, less (i) approximately $3.9 million in credits applied by the supplier based upon prior agreements. The Forbearance Agreement provides that the supplier shall forbear from exercising rights and remedies available as a result of existing overdue amounts under the Supply Agreements, so long as we pay to the supplier an aggregate of $11.8 million, in monthly payments of $0.25 million, commencing in October 2023.

Under the Forbearance Agreement, we also issued a convertible promissory note, guaranteed by certain of our subsidiaries, to the supplier in the principal amount of $15.0 million (the “Note”). The Note bears interest at a rate of 10.0% per annum, which shall be capitalized and added to the principal amount semi-annually on January 1 and July 1, commencing on July 1, 2023, and must be repaid in full, including accrued and unpaid interest thereunder, on (or before, subject to certain conditions) May 17, 2026 (the “Maturity Date”). If an Event of Default (as defined in the Note) occurs, then (i) the interest on the Note shall accrue at a rate of 14.0% per annum (or, if less, the maximum rate permitted by applicable law) and (ii) the Maturity Date may be accelerated. Subject to a beneficial ownership limitation of 19.99% of our outstanding common stock and any shareholder approval requirements, the supplier may elect, at its sole discretion, to convert any outstanding principal and interest on the Note into shares of our common stock at a conversion price of $1.30 per share.

Nasdaq Compliance

On October 14, 2022, we received a written notice (the “Notice”) from the Listing Qualifications Department of The Nasdaq Stock Market LLC that we are not in compliance with the requirement to maintain a minimum market value of listed securities of $35 million, as set forth in Nasdaq Listing Rule 5550(b)(2) (the “Market Value Standard”) because the market value of the common stock was below $35 million for 30 consecutive business days. The Notice provided that, in accordance with Nasdaq Listing Rule 5810(c)(3)(C), we had a period of 180 calendar days from the date of the Notice, or until April 12, 2023, to regain compliance under the Market Value Standard.

On April 13, 2023, we received notice from Nasdaq that we had not regained compliance with the Market Value Standard. On April 14, 2023, we filed our request for a hearing, which was held before the Nasdaq Hearing Panel (the “Panel”) on May 18, 2023.

On June 26, 2023, the Panel notified us that it had granted our request for an exception through September 15, 2023, to the continued listing requirements, subject to our demonstrating compliance with the Market Value Standard by September 15, 2023. In accordance with the Market Value Standard and Nasdaq Listing Rule 5810(c)(3)(C), compliance with the Market Value Standard may be achieved if at any time during the compliance period the market value of the listed securities closes at a value of at least $35 million for a minimum of ten consecutive business days.

The Panel noted that it reserves the right to reconsider the terms of this exception based on any event, condition or circumstance that exists or develops that would, in the opinion of the Panel, make continued listing of our securities on Nasdaq inadvisable or unwarranted. In addition, the Nasdaq Listing and Hearing Review Council may, on its own motion, determine to review any Panel decision within 45 calendar days after issuance of the written decision. There can be no assurance that we will be able to regain compliance under the Market Value Standard, or will otherwise be in compliance with other Nasdaq listing criteria. While we are exercising diligent efforts to maintain the listing of our common stock on The Nasdaq Capital Market, there can be no assurance that we will be able to regain or maintain compliance with Nasdaq listing criteria.

Corporate Information

We were incorporated in Delaware and our headquarters are located at 3201 Carnegie Avenue, Cleveland, Ohio 44115. Our telephone number is (216) 431-9900. Our website is http://www.athersys.com. The information accessible on or through our website is not part of this prospectus. We have included our website address in this prospectus solely as an inactive textual reference.

THE OFFERING

The summary below describes the principal terms of this offering. The “Description of Capital Stock” section of this prospectus contains a more detailed description of our common stock.

Issuer		Athersys, Inc.
Common stock offered by us		Up to Shares based on an assumed combined public offering price of $ , which is equal to the last sale price of our common stock as reported by Nasdaq on , 2023.
Common Warrants offered by us		Common Warrants to purchase up to shares of our common stock, which will be exercisable during the period commencing on the date of their issuance and ending years from such date at an exercise price per share equal to 100% of the public offering price/assumed exercise price of $ . Each Share (or Pre-Funded Warrant in lieu of a Share) is being sold together with one Common Warrant but are immediately separable and will be issued separately in this offering. This prospectus also relates to the shares of common stock issuable upon exercise of any Common Warrants sold in this offering.
Pre-Funded Warrants offered by us		We are offering to certain purchasers whose purchase of Shares in this offering would otherwise result in the purchaser, together with its affiliates and certain related parties, beneficially owning more than 4.99% of our outstanding shares of common stock immediately following the closing of this offering, the opportunity to purchase, if such purchasers so choose, Pre-Funded Warrants, in lieu of Shares that would otherwise result in any such purchaser’s beneficial ownership, together with its affiliates and certain related parties, exceeding 4.99% (or, at the election of such purchaser, 9.99%) of our outstanding shares of common stock immediately following the consummation of this offering. The purchase price of each Pre- Funded Warrant and accompanying Common Warrant is equal to the purchase price of the Shares and accompanying Common Warrant in this offering minus $0.0001, the exercise price of each Pre-Funded Warrant. Each Pre-Funded Warrant is immediately exercisable and may be exercised at any time until it has been exercised in full. For each Pre-Funded Warrant we sell, the number of Shares we are offering will be decreased on a one- for-one basis. This offering also relates to the shares of common stock issuable upon exercise of any Pre-Funded Warrants sold in this offering.
Common stock to be outstanding immediately after this offering		Up to shares (assuming the sale of the maximum number of Shares in this offering, at the assumed combined public offering price of $ ).
Use of proceeds		We estimate that the net proceeds from the sale of securities in this offering will be approximately $ million, based on the assumed public offering price of $ per share, the last reported sale price of our common stock on Nasdaq on , 2023, and after deducting estimated placement agent fees and estimated offering expenses payable by us. We intend to use the net proceeds of this offering for working capital and general corporate purposes. See “Use of Proceeds.”

Prior Warrant Amendments		In connection with this offering, we may enter into privately negotiated agreements with the holders of certain existing outstanding warrants to purchase shares of our common stock (the “Prior Warrants”) to, among other things, reduce the exercise price of such Prior Warrants to that of the Common Warrants being offered and sold in this offering and to extend the current expiration date of the Prior Warrants to the expiration date of the Common Warrants being offered and sold in this offering. In addition, we expect that certain terms of the Prior Warrants will also be amended to be substantially consistent with those of the Common Warrants being offered hereby. There can be no assurance that we will amend the Prior Warrants in connection with this offering or as to the final terms of any amendments to the Prior Warrants.
Risk factors		An investment in our securities involves a high degree of risk. See “Risk Factors” beginning on page 13 for a discussion of certain factors that you should consider when evaluating an investment in our securities.
Nasdaq trading symbol		Our common stock is listed on The Nasdaq Capital Market under the symbol “ATHX.”

Unless otherwise indicated, all information contained in this prospectus exclude, as of March 31, 2023:

• a total of 1,626,312 shares of common stock authorized and reserved for future issuance under outstanding awards under our equity incentive plans;

• a total of 27,491 shares of common stock authorized and reserved for future issuance under our equity incentive plans;

• a total of 429,500 shares of common stock authorized and reserved for future issuance under outstanding inducement awards granted outside of our equity incentive plans;

• 1,920,000 shares of common stock authorized and reserved for future issuance upon exercise of warrants issued and sold in August 2022;

• 2,000,000 shares of common stock authorized and reserved for future issuance upon exercise of warrants issued in September 2022;

• a total of 9,109,090 shares of common stock authorized and reserved for future issuance upon exercise of warrants issued in connection with our November 2022 public offering;

• a total of 3,685,000 shares of common stock authorized and reserved for future issuance upon exercise of warrants issued in connection with our April 2023 public offering;

• a total of 11,538,461 shares of common stock authorized and reserved for future issuance upon conversation feature of our May 2023 Convertible Note;

• 400,000 shares of common stock authorized and reserved for future issuance upon exercise of warrants held by Healios; and

• no exercise of the Common Warrants or Pre-Funded Warrants sold in this offering.

The information discussed above is illustrative only and will adjust based on the actual public offering price and other terms of this offering determined at pricing. Unless expressly indicated or the context requires otherwise, all information in this prospectus assumes an assumed public offering price of $ per share of common stock, which is the last reported sale price of our common stock on Nasdaq on , 2023.

SUMMARY FINANCIAL DATA

The following is a summary of our results of operations and financial position. The summary consolidated financial data set forth below should be read in conjunction with “Selected Consolidated Financial Data” and “Management’s Discussion and Analysis of Financial Condition and Results of Operations” and the financial statements and the notes thereto incorporated by reference into this prospectus.

	Three Months Ended March 31,						Year Ended December 31,
	2023			2022			2023			2022
	(in thousands, except per share data)
Consolidated Statement of Operations Data:
Contract and grant revenues		—			2,912			5,325			5,514
Operating expenses		7,334			25,289			82,334			92,571
Loss from operations		(7,334	)		(22,378	)		(77,009	)		(87,058	)
Other income (expense), net		(477	)		162			4,475			102
Net loss		(7,811	)		(22,216	)		(72,534	)		(86,955	)
Net loss per share, basic and diluted	$	(0.43	)	$	(2.27	)	$	(6.07	)	$	(9.69	)
Weighted average shares outstanding, basic and diluted		18,292			9,768			11,945			8,971

Please see Note C to our audited consolidated financial statements incorporated by reference into this prospectus for an explanation of the method used to calculate net loss attributable to common stockholders, basic and diluted net loss per common share, and the number of shares used in the computation of per share amounts.

	Historical			Pro forma (1)
	March 31,			March 31,
	2023			2023
	(in thousands)
Consolidated Balance Sheet Data:
Cash, cash equivalents and available-for-sale securities		3,121			6,366
Working capital		(31,847	)		(28,601	)
Total assets		21,632			24,878
Warrant liabilities and note payable		(1,163	)		(1,163	)
Total stockholders’ equity		(31,011	)		(27,766	)

(1) Pro forma figures give effect to the receipt of $3,380,347 of net proceeds from the issuance of 2,315,000 shares of common stock in the April 2023 Offerings, the receipt of $81 of proceeds upon exercise of 813,000 shares of common stock underlying the pre-funded warrants issued in the April 2023 Offerings, and the vesting of 367,664 restricted stock units. Pro forma figures exclude the effect of the April 2023 amendment to the August 2022 and September 2022 Warrants to, among other things, reduce the exercise price to $0.96 per share with respect to 1,920,000 shares of Common Stock covered by the August 2022 Warrants and 1,760,000 shares of Common Stock covered by the September 2022 Warrants.

RISK FACTORS

~~Investment~~Investing in our common stock involves risk. Prior to making a ~~high~~decision ~~degree~~about ofinvesting ~~risk~~in ~~and~~our ~~uncertainty.~~common ~~You~~stock, you should carefully consider ~~each of~~ the ~~risks~~risk ~~and~~factors ~~uncertainties~~below ~~described~~as ~~below~~well ~~and~~as those discussed under the ~~section~~heading ~~captioned~~ “Risk Factors” ~~contained~~ in our ~~Annual~~most ~~Report~~recent annual report on Form 10-K ~~for the year ended December 31~~, ~~2022,~~which ~~(the~~is ~~“Annual~~incorporated ~~Report”),as~~herein ~~updated~~ by ~~our~~reference ~~subsequent~~and ~~filings~~may ~~under~~be ~~the Securities Exchange Act of 1934~~amended, ~~as amended~~supplemented, ~~each~~or ofsuperseded ~~which~~from istime ~~incorporated~~to time by ~~reference~~other inreports ~~this~~we ~~prospectus~~have infiled ~~their entirety, together~~ with ~~other~~the ~~information~~SEC inor ~~this~~will ~~prospectus~~file ~~and~~with the ~~information~~SEC ~~and documents incorporated by reference~~ in ~~this~~the ~~prospectus, before you decide to buy our securities~~future. If any of ~~the~~these risks ~~and~~actually ~~uncertainties therein or below materializes~~occurs, our business, ~~financial condition, liquidity and~~ results of operations, ~~could~~and befinancial ~~materially~~condition ~~and~~could ~~adversely affected~~suffer. ~~This~~In ~~could~~that ~~cause~~case, the trading price of our common stock tocould decline, and you could lose all or a part of your investment. ~~You should not interpret the disclosure of any risk factor to imply that the risk has not already materialized.~~

Risks Related to ~~Our~~this ~~Business~~ Offering

~~There~~The issale ~~substantial~~or ~~doubt~~availability ~~about~~for ~~our~~sale ~~ability~~of toshares ~~continue~~issuable aspursuant ~~a going concern, which may affect our ability~~ to ~~obtain~~this ~~future~~prospectus ~~financing and~~ may ~~require~~depress usthe toprice ~~curtail~~of our ~~operations.~~common Westock, ~~will~~dilute ~~need~~the ~~substantial~~interest ~~additional~~of ~~funding to develop~~ our ~~products~~existing stockholders, and ~~for~~encourage ~~our~~short ~~future~~sales ~~operations.~~by Ifthird ~~we are unable to obtain the funds necessary to do so~~parties, wewhich ~~may~~could ~~be required to~~ further ~~delay,~~depress ~~scale~~the ~~back~~price orof ~~eliminate~~ our ~~product~~common ~~development activities or may be unable to continue our business~~stock.

~~The~~To ~~audited~~the ~~financial~~extent ~~statements~~that ~~and~~the ~~accompanying~~Selling ~~notes~~Stockholders ~~presented~~sell inshares of our ~~Annual~~common ~~Report~~stock ~~include~~pursuant ~~disclosures~~to ~~and~~this anprospectus, ~~opinion~~the ~~from~~market ~~our~~price ~~independent~~of ~~registered~~such ~~public~~shares ~~accounting~~may ~~firm~~decrease ~~stating~~due ~~that~~to ~~our~~the ~~recurring~~additional ~~losses~~selling ~~and~~pressure ~~negative~~in ~~cash~~the ~~flows~~market. In addition, the dilution from ~~operations~~exercise ~~raise~~of ~~substantial~~the ~~doubt~~Subject ~~about~~Warrants may cause stockholders to sell their shares of our ~~ability~~common stock, which could further contribute to ~~continue~~any asdecline ain ~~going~~the ~~concern~~price of our common stock. ~~Our~~Any ~~financial~~downward ~~statements~~pressure ason the price of ~~December~~our ~~31,~~common ~~2022~~stock ~~and~~caused ~~2021~~by ~~were~~the ~~prepared~~sale ~~under~~or potential sale of such shares could encourage short sales by third parties. Such sales could place downward pressure on the ~~assumption~~price ~~that~~of weour ~~will~~common ~~continue~~stock asby aincreasing ~~going~~the ~~concern~~number ~~and~~of doshares ~~not~~of ~~include~~our ~~any~~common ~~adjustments~~stock ~~that~~being ~~might~~sold, ~~result~~which ~~from~~could further contribute to any decline in the ~~outcome~~market price of ~~this~~our ~~uncertainty~~common stock.

~~The~~Risks ~~development~~Related ~~of our product candidates will require a commitment of substantial funds~~ to ~~conduct~~Our ~~the~~Common research, which may include preclinical and clinical testing, necessary to obtain regulatory approvals and bring our products to market. Net cash used in our operations was $59.0 million in 2022, $76.2 million in 2021 and $61.8 million in 2020.Stock

AtCurrently ~~December~~there ~~31, 2022, we had $9.0 million of cash and cash equivalents. As of March 31, 2023, we had accounts payable of $29.0 million, of which approximately 75%~~ is ~~owed~~a tolimited ~~our~~public ~~primary~~market ~~contract manufacturer, that was subsequently agreed to be settled~~ for aour ~~convertible~~common ~~note as described in “Prospectus Summary — Recent Developments~~stock,” and we ~~only~~cannot ~~had~~predict ~~cash~~the ~~and~~future ~~cash~~prices ~~equivalents~~or ofthe ~~$3.1~~amount ~~million.~~of ~~Accordingly,~~liquidity weof ~~will need substantially more funding to advance~~ our ~~product~~common ~~candidates through development and into commercialization, including to put in place manufacturing capacity to support such commercial activity~~stock. ~~Our future capital requirements will depend on many factors, including:~~

•Currently, there is a limited public market for our ~~ability~~common stock. Our common stock is quoted on the OTC Pink under the symbol “ATHX.” However, the OTC Pink is not a liquid market in contrast to ~~raise~~the ~~capital~~major stock exchanges. Prices for securities traded solely on the OTC Pink may be difficult to ~~fund~~obtain and holders of common stock may be unable to resell their securities at or near their original offering price or at any price. We cannot assure you as to the liquidity or the future market prices of our ~~operations;~~common stock if a market does develop. If an active market for our common stock does not develop, the fair market value of our common stock could be materially adversely affected. We cannot predict the future prices of our common stock.

•Trading ~~the~~in ~~progress, scope, costs and results of~~ our ~~clinical~~common ~~and~~stock ~~preclinical~~on ~~testing~~the ofOTC ~~any~~Pink ~~current~~has orbeen ~~future~~subject ~~product~~to ~~candidates;~~wide fluctuations.

•Our common stock is currently quoted for public trading on the ~~possibility~~OTC Pink. The trading price of ~~delays~~our common stock has been subject to wide fluctuations. Trading prices of our common stock may fluctuate in response to a number of factors, ~~adverse~~many ~~events~~of which will be beyond our control. The stock market has generally experienced extreme price and volume fluctuations that have often been unrelated or disproportionate to the operating performance of companies with limited business operation. There can be no assurance that trading prices and ~~excessive~~price ~~costs~~earnings ratios previously experienced by our common stock will be matched or maintained. These broad market and industry factors may adversely affect the market price of our common stock, regardless of our operating performance. In the ~~development~~past, ~~process;~~following periods of volatility in the market price of a company’s securities, securities class-action litigation has often been instituted. Such litigation, if instituted, could result in substantial costs for us and a diversion of management’s attention and resources.

•Our common stock is currently quoted only on the ~~cost~~OTC ofPink, ~~manufacturing~~which may have an unfavorable impact on our ~~product~~stock ~~candidates;~~price and liquidity.

•Our common stock is quoted on the ~~cost~~OTC ofPink, ~~prosecuting~~which is a significantly more limited market than the New York Stock Exchange, ~~defending~~the NYSE American, or The Nasdaq Stock Market. The quotation of our shares of common stock on the OTC Pink may result in a less liquid market available for existing and ~~enforcing~~potential ~~patent~~stockholders ~~claims~~to trade shares of our common stock, could depress the trading price of our common stock and ~~other~~could ~~intellectual~~have ~~property~~a ~~rights;~~long-term adverse impact on our ability to raise capital in the future.

~~• the time and cost involved in obtaining regulatory approvals;~~3

•Table ~~expenses related to complying with cGMP~~ of ~~therapeutic product candidates;~~Contents

•There ~~costs~~can be no assurance that there will be an active market for our shares of ~~financing~~common stock either now or ~~acquiring~~in ~~additional~~the ~~capital~~future. ~~equipment~~Market liquidity will depend on the perception of our operating business and ~~development~~any ~~technologies;~~steps that our management might take to bring us to the awareness of investors. There can be no assurance given that there will be any awareness generated. Consequently, investors may not be able to liquidate their investment in our shares of common stock or liquidate at a price that reflects the value of the business. As a result, holders of our shares of common stock may not find purchasers for such shares should they desire to sell them. Consequently, our shares of common stock should be purchased only by investors having no need for liquidity in their investment and who can hold such shares for an indefinite period of time.

•The ~~competing~~Company’s ~~technological~~common stock is considered a “penny stock” and ~~market~~may ~~developments;~~be difficult to sell.

•The ~~our~~Company’s ~~ability~~common stock is considered to ~~establish~~be ~~and~~a ~~maintain~~“penny ~~collaborative~~stock” ~~and~~under ~~other~~rules ~~arrangements~~promulgated ~~with~~pursuant ~~third~~to ~~parties~~the Exchange Act. Reasons for categorization as a penny stock include but are not limited to ~~assist~~the following: (i) the stock trades at a price less than $5.00 per share; (ii) it is not traded on a “recognized” national exchange; (iii) it is not quoted on The Nasdaq Stock Market, or even if so, has a price less than $5.00 per share; or (iv) it is issued by a company with net tangible assets less than $2.0 million, if in ~~bringing~~business ~~our~~more ~~products~~than toa ~~market~~continuous ~~and~~three years, or with average revenues of less than $6.0 million for the ~~cost~~past three years. The principal result or effect of ~~such~~being ~~arrangements;~~designated a “penny stock” is that securities broker-dealers cannot recommend the stock but must trade in it on an unsolicited basis.

13Additionally, Section 15(g) of the Exchange Act and Rule 15g-2 promulgated thereunder by the SEC require broker-dealers dealing in penny stocks to provide potential investors with a document disclosing the risks of penny stocks and to obtain a manually signed and dated written receipt of the document before effecting any transaction in a penny stock for the investor’s account.

•Holders in the ~~amount~~Company’s common stock are urged to obtain and ~~timing~~read such disclosure carefully before purchasing any shares that are deemed to be “penny stock.” Moreover, Rule 15g-9 requires broker-dealers in penny stocks to approve the account of ~~payments~~any orinvestor ~~equity~~for ~~investments~~transactions in such stocks before selling any penny stock to that weinvestor. ~~receive~~This procedure requires the broker-dealer to: (i) obtain from ~~collaborators~~the orinvestor ~~changes~~information concerning its financial situation, investment experience and investment objectives; (ii) reasonably determine, based on that information, that transactions in orpenny ~~terminations~~stocks are suitable for the investor and that the investor has sufficient knowledge and experience as to be reasonably capable of ~~future~~evaluating orthe ~~existing~~risks ~~collaboration~~of penny stock transactions; (iii) provide the investor with a written statement setting forth the basis on which the broker-dealer made the determination in (ii) above; and ~~licensing~~(iv) ~~arrangements~~receive a signed and dated copy of such statement from the ~~timing~~investor, confirming that it accurately reflects the investor’s financial situation, investment experience and ~~amount~~investment objectives. Compliance with these requirements may make it more difficult for holders of ~~expenses~~the weCompany’s ~~incur~~common stock to ~~support~~resell ~~these~~their ~~collaborations~~shares ~~and~~to ~~license~~third ~~agreements;~~parties or to otherwise dispose of them in the market or otherwise.

•The ~~costs~~Financial ~~associated~~Industry ~~with~~Regulatory ~~the~~Authority ~~integration~~(“FINRA”), ofhas ~~any~~adopted ~~new~~sales ~~operation,~~practice ~~including~~requirements ~~costs~~that ~~relating~~may toalso ~~future~~limit ~~mergers~~a ~~and~~stockholder’s ~~acquisitions~~ability ~~with~~to ~~companies~~buy ~~that~~and ~~have~~sell ~~complementary~~our ~~capabilities;~~stock.

•In ~~expenses~~addition ~~related~~to the “penny stock” rules described above, FINRA has adopted rules that require that, in recommending an investment to a customer, a broker-dealer must have reasonable grounds for believing that the ~~establishment~~investment ofis ~~sales~~suitable for that customer. Prior to recommending speculative low-priced securities to their non-institutional customers, broker-dealers must make reasonable efforts to obtain information about the customer’s financial status, tax status, investment objectives and ~~marketing~~other ~~capabilities~~information. Under interpretations of these rules, FINRA believes that there is a high probability that speculative low-priced securities will not be suitable for ~~products~~at ~~awaiting~~least ~~approval~~some orcustomers. ~~products~~FINRA requirements make it more difficult for broker-dealers to recommend that their customers buy our common stock, which may limit your ability to buy and sell our stock and have ~~been~~an ~~approved;~~adverse effect on the market for our shares.

~~• expenses related to establishing manufacturing capabilities;~~4

•Table ~~the level~~ of ~~our sales and marketing expenses; and~~Contents

• our ability to introduce and sell new products.

We have secured capital historically from grant revenues, collaboration proceeds and debt and equity offerings. We will need to secure substantial additional capital to fund our future operations. We cannot be certain that additional capital will be available on acceptable terms or at all. To the extent we raise additional capital through the sale of equity securities, the ownership position of our existing stockholders could be substantially diluted. If additional funds are raised through the issuance of preferred stock or debt securities, these securities are likely to have rights, preferences and privileges senior to our common stock. Fluctuating interest rates could also increase the costs of any debt financing we may obtain.

Importantly, we expect that the results of our MASTERS-2 clinical trial, will have a significant impact, favorable or unfavorable, on our ability to access capital from potential third-party commercial partners or the equity capital markets. Depending on the nature of these results, we may accelerate or may delay certain programs. In the longer term, we will have to continue to generate additional capital to meet our needs until we would become cash flow positive as a result of the sales of our clinical products, if they are approved for marketing.

Failure to successfully address ongoing liquidity requirements will have a material adverse effect on our business. If we are unable to obtain additional capital on acceptable terms when needed, we may be required to take actions that harm our business and our ability to achieve cash flow in the future, including possibly the surrender of our rights to some technologies or product opportunities, delaying our clinical trials or curtailing or ceasing operations.

If we are unable to raise capital, we could be forced to eliminate our product development programs, may be unable to continue our business and may need to file for protection under the bankruptcy laws.

There is substantial doubt about our ability to continue as a going concern, which may affect our ability to obtain future financing and may require us to curtail our operations. In the near term, we will need substantial additional funding to develop our MultiStem product candidate and to continue our operations. Even if we are able to obtain additional funding in the near term, such funding may not be sufficient to allow us to continue our operations for an extended period of time.

The audited financial statements and accompanying notes presented in the Annual Report on Form 10-K for the year ended December 31, 2022 include disclosures and an opinion from our independent registered public accounting firm stating that our recurring losses and negative cash flows from operations raise substantial doubt about our ability to continue as a going concern.

As of March 31, 2023, we had accounts payable of $29.0 million that is currently due and we only had cash and cash equivalents of $3.1 million. To conserve cash, we have been delaying payments to most of our suppliers and service providers, including our primary contract manufacturer. In the near term, we will need to obtain significant capital funding through public or private equity offerings, debt financings, collaborations and licensing arrangements or other sources to fund our operations. However, there can be no assurance that we will be able to obtain adequate funding on terms acceptable to us, on a timely basis or at all, particularly in light of our current stock price and liquidity. If we are unable to obtain funding, we may be required to further delay, reduce or eliminate our MultiStem product candidate approval efforts, which could adversely affect our business prospects, and we may be unable to continue operations.

If we raise additional funds through collaborations, strategic alliances or marketing, distribution or licensing arrangements with third parties, we may have to relinquish valuable rights to our technologies, future revenue streams, products or product candidates or to grant licenses on terms that may not be favorable to us.

Adequate additional financing may not be available to us on acceptable terms, or at all. There can be no assurance that we will be able to license-out our MultiStem product candidate on a timely basis or on terms that are favorable to us, or at all. Our failure to raise capital through financing or a license as and when needed would have a negative impact on our financial condition and our ability to pursue our business strategy. We could be forced to discontinue the development of our MultiStem product candidate and seek collaborators on terms that are less favorable than might otherwise be available, and relinquish or license, potentially on unfavorable terms, our rights to MultiStem. If we are unable to obtain adequate financing, we would likely have to file for protection under the bankruptcy laws to continue to pursue potential transactions and conduct a wind-down of our Company. If we decide to dissolve and liquidate our assets or to seek protection under the bankruptcy laws, it is unclear to what extent we will be able to pay our obligations, and, accordingly, it is further unclear whether and to what extent any resources will be available for distributions to stockholders.

We have incurred losses since inception, and we expect to incur significant net losses in the foreseeable future and may never become profitable.

Since our inception in 1995, we incurred significant losses and negative cash flows from operations. We incurred net losses of $72.5 million in 2022, $87.0 million in 2021 and $78.8 million in 2020. As of March 31, 2023, we had an accumulated deficit of $663.7 million, and we will not commence sales of our clinical product candidates until they receive regulatory approval for commercialization. We expect to spend significant resources over the next several years to continue our research and product development programs, including clinical trials of our product candidates and to prepare for possible regulatory approval and commercial activities. We expect to continue to incur substantial losses through at least the next several years and may incur losses in subsequent periods, and our ability to commercialize our product candidates is uncertain. To date, substantially all of our revenue has been derived from corporate collaborations, license agreements and government grants. In order to achieve profitability, we must develop products and technologies that can be commercialized by us or through our existing or future collaborations. Our ability to generate revenues and become profitable will depend on our ability, alone or with potential collaborators, to timely, efficiently and successfully complete the development of our product candidates. We have never earned revenue from selling a product and we may never do so, as none of our product candidates have been approved for sale, since they are currently being tested in human studies. We cannot assure you that we will ever earn sales revenue or that we will ever become profitable. If we sustain losses over an extended period, we may be unable to continue our business.

Risks Related to Our Dependence on Third Parties

We may not successfully maintain our existing collaborative and licensing arrangements, or establish new ones, which could adversely affect our ability to develop and commercialize our product candidates.

A key element of our business strategy is to commercialize some of our product candidates through collaborations with other companies. Our strategy includes establishing collaborations and licensing agreements with one or more pharmaceutical, biotechnology or device companies, preferably after we have advanced product candidates through the initial stages of clinical development. However, we may not be able to establish or maintain such licensing and collaboration arrangements necessary to develop and commercialize our product candidates. Even if we are able to maintain or establish licensing or collaboration arrangements, these arrangements may not be on favorable terms and may contain provisions that will restrict our ability to develop, test and market our product candidates. Any failure to maintain or establish licensing or collaboration arrangements on favorable terms could adversely affect our business prospects, financial condition or ability to develop and commercialize our product candidates.

Our agreements with our collaborators and licensees may have provisions that give rise to disputes regarding the rights and obligations of the parties. These and other possible disagreements could lead to termination of the agreement or delays in collaborative research, development, supply, or commercialization of certain product candidates, or could require or result in litigation or arbitration. Moreover, disagreements could arise with our collaborators over rights to intellectual property or our rights to share in any of the future revenues of products developed by our collaborators. These kinds of disagreements could result in costly and time-consuming litigation. Any such conflicts with our collaborators could reduce our ability to obtain future collaboration agreements and could have a negative impact on our relationship with existing collaborators.

Currently, we have a material collaboration and licensing arrangement is with Healios, also a significant holder of our outstanding shares of common stock, to develop and commercialize MultiStem cell therapy for the treatment of ischemic stroke and ARDS in Japan, among other things, and we also have license agreements with third parties pursuant to which we in-license certain aspects of our technologies. These arrangements may not have specific termination dates; rather, each arrangement terminates upon the occurrence of certain events.

Healios has alleged that we are in material breach of our comprehensive framework agreement for commercial manufacturing and ongoing support for, among other things, not meeting our supply obligations and cooperation and assistance obligations. We strongly disagree with Healios’ allegations and will continue to work with Healios to try to resolve this dispute. However, there can be no assurance that we will be able to resolve this dispute without legal proceedings, which could divert management’s attention, be costly and result in damages and/or costly injunctive or other remedies.

Risks Related to Our Common Stock and This Offering

Our management will have broad discretion over the use of the proceeds to us from this offering and may apply it to uses that do not improve our operating results or the value of our securities.

Our management will have broad discretion in the application of the net proceeds from this offering, and investors will be relying solely on such judgment of our management regarding the application of these proceeds. We have not allocated the net proceeds for specific purposes. Investors will not have the opportunity, as part of their investment decision, to assess whether the proceeds are being used appropriately. Our use of the proceeds may not improve our operating results or increase the value of the securities being offered hereby.

You will experience immediate and substantial dilution in the net tangible book value per share of the common stock you purchase.

Since the price per share of our common stock being offered is substantially higher than the historical net tangible book value per share of our common stock, you will suffer substantial dilution in the net tangible book value of the common stock you purchase in this offering. If you purchase shares of common stock in this offering, you will suffer immediate and substantial dilution of approximately $ per share in the adjusted net tangible book value of the common stock. See the section entitled “Dilution” in this prospectus for a more detailed discussion of the dilution you will incur if you purchase common stock in this offering.

You may experience dilution of your ownership interests because of the future issuance of additional shares of our common stock.

In the future, we may need to issue additional authorized but previously unissued equity securities, resulting in the dilution of the ownership interests of our stockholders. In May 2023, we also issued the Note to a supplier in exchange for a reduction in the amount of our liabilities owed to the supplier, and the Note is convertible into a significant amount of our common stock. We also have outstanding options and warrants that are convertible into shares of common stock.We may also issue additional common stock or other securities that are convertible into or exercisable for common stock in connection with hiring or retaining employees, future acquisitions, future sales of securities for capital raising purposes, or for other business purposes. The future issuance of any such additional shares of common stock may create downward pressure on the trading price of our common stock. There can be no assurance that we will not be required to issue additional shares, warrants, or other convertible securities in the future in conjunction with any capital raising efforts, including at a price (or exercise prices) below the offering price of the shares of common stock in this offering.

We are not currently in compliance with Nasdaq’s continued listing requirements. If we are unable to comply with Nasdaq’s continued listing requirements, our common stock could be delisted, which could affect the price of our common stock and liquidity and reduce our ability to raise capital.

Our common stock is currently listed on The Nasdaq Capital Market. The Nasdaq Capital Market has established certain quantitative criteria and qualitative standards that companies must meet to remain listed for trading on this market.

On October 14, 2022, we received a written notice (the “Notice”) from the Listing Qualifications Department of The Nasdaq Stock Market LLC that we are not in compliance with the requirement to maintain a minimum market value of listed securities of $35 million, as set forth in Nasdaq Listing Rule 5550(b)(2) (the “Market Value Standard”) because the market value of the common stock was below $35 million for 30 consecutive business days. The Notice does not impact the listing of the common stock on The Nasdaq Capital Market at this time.

The Notice provided that, in accordance with Nasdaq Listing Rule 5810(c)(3)(C), the Company had a period of 180 calendar days from the date of the Notice, or until April 12, 2023, to regain compliance under the Market Value Standard.

On April 13, 2023, we received notice from The Nasdaq Stock Market that we had not regained compliance with the Market Value Standard. On April 14, 2023, we filed our request for a hearing, which was held before the Nasdaq Hearing Panel (the “Panel”) on May 18, 2023.

On June 26, 2023, the Panel notified the Company that it had granted our request for an exception through September 15, 2023, to the continued listing requirements, subject to the Company demonstrating compliance with the Market Value Standard by September 15, 2023.

There can be no assurance that the Company will be able to regain compliance with the Market Value Standard, or will otherwise be in compliance with other Nasdaq listing criteria. While the Company is exercising diligent efforts to maintain the listing of the Company’s common stock on The Nasdaq Capital Market, there can be no assurance that the Company will be able to regain or maintain compliance with Nasdaq listing criteria. If the Company fails to regain compliance with Nasdaq’s continued listing standards during the exception period granted by the Panel, our common stock will be subject to delisting from Nasdaq. Any delisting of our common stock could adversely affect the market liquidity of our common stock and the market price of our common stock could decrease. Furthermore, if our common stock were delisted it could adversely affect our ability to obtain financing for the continuation of our operations and our ability to attract and retain employees by means of equity compensation and/or result in the loss of confidence by investors.

Broad market and industry factors, as well as economic and political factors, also may materially adversely affect the market price of Athersys’ common stock. The market price of our common stock has been extremely volatile and may continue to be volatile due to numerous circumstances beyond our control.

The market price of our common stock has fluctuated, and may continue to fluctuate, widely, due to many factors, some of which may be beyond our control. The following factors, in addition to other risk factors described in this section, may have a significant impact on the market price of our common stock:

• developments in our clinical trials, particularly our MASTERS-2 trial;

• announcements of significant changes in our business or operations, including the decision to implement restructurings such as a reduction in our workforce;

• the development status of our MultiStem product candidate, including clinical study results and determinations by regulatory authorities with respect thereto;

• the initiation, termination or reduction in the scope of any collaboration arrangements, including with Healios, or any disputes or developments regarding such collaborations;

• our inability to obtain additional funding;

• disputes or other developments concerning our proprietary rights;

• additions or departures of key personnel;

• “short squeezes”;

• comments by securities analysts or discussions of our business, products, financial performance, prospects or stock price by the financial and scientific press and online investor communities;

• changes in, or failure to meet, securities analysts’ or investors’ expectations of our financial performance;

• large stockholders exiting their position in our common stock or an increase or decrease in the short interest in our common stock;

• public concern as to, and legislative action with respect to, the pricing and availability of prescription drugs or the safety of drugs and drug delivery techniques;

• regulatory developments in the United States and in foreign countries;

• dilutive effects of sales of shares of common stock by Athersys or Athersys’ stockholders; and

• overall general market fluctuations.

The market prices for securities of biopharmaceutical and biotechnology companies, and early-stage drug discovery and development companies like Athersys in particular, have experienced extreme price and volume fluctuations that have often been unrelated or disproportionate to the operating performance of those companies and our company. For example, on July 26, 2022 and July 28, 2022, the closing price of our common stock on The Nasdaq Capital Market was $4.25 and $8.25, respectively, and daily trading volume on these days was approximately 0.2 million and 10.7 million shares, respectively.

During this time, we did not release any material information regarding us or our business. These broad market fluctuations may adversely affect the trading price of our common stock. In particular, a proportion of our common stock has been and may continue to be traded by short sellers, which may put pressure on the supply and demand for our common stock, further influencing volatility in its market price. Additionally, these and other external factors have caused and may continue to cause the market price and demand for our common stock to fluctuate, which may limit or prevent investors from readily selling their shares of common stock and may otherwise negatively affect the liquidity of our common stock.

In addition, in the past, following periods of market volatility in the market price of a company’s securities or the reporting of unfavorable news, securities litigation has often been instituted against these companies. Volatility in the market price of our shares could also increase the likelihood of regulatory scrutiny. Securities litigation, if instituted against us, or any regulatory inquiries or actions that we face could result in substantial costs, diversion of our management’s attention and resources and unfavorable publicity, regardless of the merits of any claims made against us or the ultimate outcome of any such litigation or action.

A “short squeeze” is a sudden increase in demand for shares of our common stock that largely could lead to extreme price volatility in shares of our common stock.

Investors may purchase shares of our common stock to hedge existing exposure or to speculate on the price of our common stock. Speculation on the price of our common stock may involve long and short exposures. To the extent aggregate short exposure exceeds the number of shares of our common stock available for purchase on the open market, investors with short exposure may have to pay a premium to repurchase shares of our common stock for delivery to lenders of our common stock. Those repurchases may, in turn, dramatically increase the price of our common stock until additional shares of our common stock are available for trading or borrowing. This is often referred to as a “short squeeze.” A proportion of our common stock has been and may continue to be traded by short sellers, which may increase the likelihood that our common stock will be the target of a short squeeze. A short squeeze could lead to volatile price movements in shares of our common stock that are unrelated or disproportionate to our operating performance and, once investors purchase the shares of our common stock necessary to cover their short positions, the price of our common stock may rapidly decline. Investors that purchase shares of our common stock during a short squeeze may lose a significant portion of their investment.

There is no public market for the Pre-Funded Warrants or Common Warrant being offered in this offering.

There is no established public trading market for the Pre-Funded Warrants or Common Warrants being offered in this offering, and we do not expect a market to develop. In addition, we do not intend to apply to list the Pre-Funded Warrants or Common Warrants on Nasdaq or any national securities exchange or other nationally recognized trading system. Without an active market, the liquidity of the Pre-Funded Warrants and Common Warrants will be limited.

We may not receive any additional funds upon the exercise of the Pre-Funded Warrants or Common Warrants.

Each Pre-Funded Warrant and Common Warrant may be exercised by way of a cashless exercise, meaning that the holder may not pay a cash purchase price upon exercise, but instead would receive upon such exercise the net number of shares of our common stock determined according to the formula set forth in the Pre-Funded Warrant or Common Warrant. Accordingly, we may not receive any additional funds upon the exercise of the Pre-Funded Warrants or Common Warrants.

The Pre-Funded Warrants and Common Warrants are speculative in nature.

The Pre-Funded Warrants and Common Warrants do not confer any rights of common stock ownership on their holders, such as voting rights or the right to receive dividends, but rather merely represent the right to acquire shares of common stock at a fixed price for a limited period of time. Specifically, commencing on the date of issuance, holders of the Common Warrants may exercise their right to acquire common stock and pay an exercise price of $ per share, subject to certain adjustments, prior to years from the date on which such warrants were issued, after which date any unexercised Common Warrants will expire and have no further value. Holders of Pre-Funded Warrants have identical rights, except that the Pre-Funded Warrants have an exercise price of $0.0001 and do not expire until exercised in full. Moreover, following this offering, the market value of the Pre-Funded Warrants and Common Warrants, if any, is uncertain and there can be no assurance that the market value of the Pre-Funded Warrants and Common Warrants will equal or exceed their imputed offering price. The Pre-Funded Warrants and Common Warrants will not be listed or quoted for trading on any market or exchange. There can be no assurance that the market price of the common stock will ever equal or exceed the exercise price of the Common Warrants and consequently, whether it will ever be profitable for holders of the Common Warrants to exercise the warrants.

Holders of the Common Warrants and Pre-Funded Warrants offered hereby will have no rights as common stockholders with respect to the shares our common stock underlying the warrants until such holders exercise their warrants and acquire our common stock, except as otherwise provided in the Common Warrants and Pre-Funded Warrants.

Until holders of the Common Warrants and/or Pre-Funded Warrants acquire shares of our common stock upon exercise thereof, such holders will have no rights with respect to the shares of our common stock underlying such warrants, except to the extent that holders of such Common Warrants and Pre-Funded Warrants will have certain rights to participate in distributions or dividends paid on our common stock as set forth in the Common Warrants. Upon exercise of the Common Warrants and Pre-Funded Warrants, the holders will be entitled to exercise the rights of a common stockholder only as to matters for which the record date occurs after the exercise date.

The best efforts structure of this offering may have an adverse effect on our business plan.

The Placement Agent is offering the securities in this offering on a reasonable best efforts basis. The Placement Agent is not required to purchase any securities, but will use its reasonable best efforts to sell the securities offered. As a “best efforts” offering, there can be no assurance that the offering contemplated hereby will ultimately be consummated or will result in any proceeds being made available to us. The success of this offering will impact our ability to use the proceeds to execute our business plan. An adverse effect on the business may result from raising less than anticipated, and from the fact that there is no minimum raise.

Purchasers who purchase our securities in this offering pursuant to a securities purchase agreement may have rights not available to purchasers that purchase without the benefit of a securities purchase agreement.

In addition to rights and remedies available to all purchasers in this offering under federal securities and state law, the purchasers that enter into a securities purchase agreement will also be able to bring claims of breach of contract against us. The ability to pursue a claim for breach of contract provides those investors with the means to enforce the covenants uniquely available to them under the securities purchase agreement.

Additionally, in connection with this offering, we may agree to amend the terms of certain of our outstanding warrants held by certain significant purchasers in this offering who will enter into the securities purchase agreement. Any such amendments may, among other things, decrease the exercise prices to be the same as the exercise prices of the Common Warrants offered in this offering, or increase the term of exercise of those warrants.

CAUTIONARY NOTE REGARDING FORWARD-LOOKING STATEMENTS

This prospectus and the documents incorporated by reference herein and therein contain “forward-looking statements” as defined in the Private Securities Litigation Reform Act of 1995 that involve risks and uncertainties. These forward-looking statements relate to, among other things, the expected timetable for development of our product candidates, our growth strategy and our future financial performance, including our operations, economic performance, financial condition, prospects and other future events. We have attempted to identify forward-looking statements by using such words as “anticipates,” “believes,” “can,” “continue,” “could,” “estimates,” “expects,” “intends,” “may,” “plans,” “potential,” “should,” “suggest,” “will” or other similar expressions. These forward-looking statements are only predictions and are largely based on our current expectations.

In addition, a number of known and unknown risks, uncertainties and other factors could affect the accuracy of these statements. Some of the more significant known risks that we face are the risk that we will be unable to raise capital to fund our operations in the near term and long term, including our ability to obtain funding through public or private equity offerings, debt financings, collaborations and licensing arrangements or other sources, on terms acceptable to us or at all, and to continue as a going concern and our ability to successfully resolve the payment issues with our primary contract manufacturer and gain access to our clinical product. The following risks and uncertainties may cause our actual results, levels of activity, performance or achievements to differ materially from any future results, levels of activity, performance or achievements expressed or implied by these forward-looking statements:

• our ability to raise capital to fund our operations in the near term and long term, including our ability to obtain funding through public or private equity offerings, debt financings, collaborations and licensing arrangements or other sources, on terms acceptable to us or at all, and to continue as a going concern;

• our collaborators’ ability and willingness to continue to fulfill their obligations under the terms of our collaboration agreements and generate sales related to our technologies;

• the possibility of unfavorable results from ongoing and additional clinical trials involving our MultiStem® (invimestrocel) cell therapy, or MultiStem;

• the risk that positive results in a clinical trial may not be replicated in subsequent or confirmatory trials or success in an early stage clinical trial may not be predictive of results in later stage or large scale clinical trials;

• our ability to regain compliance with the requirement to maintain a minimum market value of listed securities of $35 million as set forth in Nasdaq Listing Rule 5550(b)(2);

• the timing and nature of results from MultiStem clinical trials, including the MASTERS-2 Phase 3 clinical trial evaluating the administration of MultiStem for the treatment of ischemic stroke;

• our ability to meet milestones and earn royalties under our collaboration agreements, including the success of our collaboration with Healios;

• the success of our MACOVIA clinical trial evaluating the administration of MultiStem for the treatment of ARDS induced by COVID-19 and other pathogens, and the MATRICS-1 clinical trial being conducted with The University of Texas Health Science Center at Houston evaluating the treatment of patients with serious traumatic injuries;

• the availability of product sufficient to meet our clinical needs and potential commercial demand following any approval;

• the possibility of delays in, adverse results of, and excessive costs of the development process;

• our ability to successfully initiate and complete clinical trials of our product candidates;

• the possibility of delays, work stoppages or interruptions in manufacturing by third parties or us, such as due to material supply constraints, contamination, operational restrictions due to COVID-19 or other public health emergencies, labor constraints, regulatory issues or other factors that could negatively impact our trials and the trials of our collaborators;

• uncertainty regarding market acceptance of our product candidates and our ability to generate revenues, including MultiStem cell therapy for neurological, inflammatory and immune, cardiovascular and other critical care indications;

• changes in external market factors;

• changes in our industry’s overall performance;

• changes in our business strategy;

• our ability to protect and defend our intellectual property and related business operations, including the successful prosecution of our patent applications and enforcement of our patent rights, and operate our business in an environment of rapid technology and intellectual property development;

• our possible inability to realize commercially valuable discoveries in our collaborations with pharmaceutical and other biotechnology companies;

• the success of our efforts to enter into new strategic partnerships and advance our programs;

• our possible inability to execute our strategy due to changes in our industry or the economy generally;

• changes in productivity and reliability of suppliers;

• the success of our competitors and the emergence of new competitors;

• our ability to maintain our listing on Nasdaq and meet Nasdaq’s listing requirements; and

• the risks described in our Annual Report on Form 10-K for the year ended December 31, 2022 and our other filings with the SEC.

Any forward-looking statement you read in this prospectus or any document incorporated by reference herein reflects our current views with respect to future events and is subject to these and other risks, uncertainties and assumptions relating to our operations, operating results, growth strategy and liquidity. Although we currently believe that the expectations reflected in these forward-looking statements are reasonable, we cannot guarantee our future results, levels of activity or performance. You should not place undue reliance on these forward-looking statements because such statements speak only as of the date when made. We undertake no obligation to publicly update forward-looking statements, whether as a result of new information, future events or otherwise, except as otherwise required by law. You are advised, however, to consult any further disclosures we make on related subjects in our reports on Forms 10-Q, 8-K and 10-K filed with the SEC. You should understand that it is not possible to predict or identify all risk factors. Consequently, you should not consider any such list to be a complete set of all potential risks or uncertainties.

Any document incorporated by reference in this prospectus may also contain statistical data and estimates we obtained from industry publications and reports generated by third parties. Although we believe that such publications and reports are reliable, we have not independently verified their data.

USE OF PROCEEDS

We ~~estimate~~will ~~that~~not ~~the~~receive ~~net~~any ~~proceeds~~of tothe usproceeds from the sale or other disposition of ~~the~~shares ~~all~~of ~~securities~~our ~~offered~~common ~~hereby~~stock ~~will~~held beby ~~approximately~~the ~~$ million,~~Selling ~~based~~Stockholders ~~upon~~pursuant anto ~~assumed~~this ~~public~~prospectus. ~~offering~~However, we will receive the exercise price of ~~$ per~~the ~~share~~Subject Warrants, which, isif ~~the~~exercised ~~last~~in ~~reported~~cash ~~sale~~with ~~price~~respect ofto ~~our~~the shares of common stock onoffered ~~Nasdaq~~hereby, onwould ,result ~~2023,~~in ~~assuming~~gross noproceeds ~~sale~~to us of ~~any~~approximately ~~Pre-Funded~~$762,000. ~~Warrants~~However, we cannot predict when and noin ~~exercise~~what ofamounts or if the ~~Common~~Subject Warrants ~~issued~~will inbe ~~connection~~exercised ~~with~~by ~~this~~payments ~~offering,~~of cash and ~~after~~it ~~deducting~~is ~~estimated~~possible ~~placement~~that ~~agent~~the ~~fees~~Subject Warrants may expire and ~~estimated~~never ~~offering~~be ~~expenses~~exercised, ~~payable~~in bywhich uscase we would not receive any cash proceeds.

~~Each~~We ~~$0.25~~will ~~increase~~bear ~~or decrease in~~ the ~~assumed~~out-of-pocket ~~public~~costs, ~~offering~~expenses, ~~price~~and offees ~~$ per~~incurred ~~share,~~in ~~which~~connection iswith the ~~last~~registration ~~reported~~of ~~sale~~shares ~~price~~ of our common stock ~~on Nasdaq on , 2023, would increase or decrease, as applicable, the net proceeds~~ to usbe ~~from~~sold ~~this offering~~ by ~~approximately $ million, assuming~~ the ~~number~~Selling ofStockholders ~~shares~~pursuant ~~offered~~to ~~by us, as set forth on the cover page of~~ this prospectus including, ~~remains~~without ~~the same~~limitation, ~~assuming~~all noregistration ~~sale of any Pre-Funded Warrants~~ and nofiling ~~exercise~~fees, ofstock ~~the~~exchange ~~Common~~or ~~Warrants~~OTC ~~issued~~listing ~~in connection with this offering~~fees, and ~~after deducting placement agent~~ fees and ~~estimated offering~~ expenses ~~payable by us. Similarly, each increase or decrease~~ of 1,000,000 shares in the number of shares of common stock offered by us would increase or decrease, as applicable, the net proceeds to us from this offering by approximately $ million, assuming the public offering price of $ per share, which is the last reported sale price of our ~~common~~counsel ~~stock on Nasdaq on , 2023, remains the same, assuming no sale of any Pre-Funded Warrants~~ and noour ~~exercise~~accountants. ofThe ~~the~~Selling ~~Common~~Stockholders ~~Warrants~~will ~~issued~~bear intheir ~~connection~~own ~~with~~underwriting ~~this~~discounts, ~~offering~~commissions, ~~and after deducting~~ placement agent fees, ~~and~~or ~~estimated~~other ~~offering~~similar expenses payable bywith ~~us.~~respect Weto dotheir ~~not~~sales ~~expect that a change in the public offering price or the number~~ of shares byof ~~these amounts would have a material effect on~~ our ~~uses~~common ~~of the proceeds from this offering, although it may accelerate the time at which we will need to seek additional capital~~stock.

We intend to use the net proceeds from this offering for working capital and general corporate purposes. The amount, timing and nature of specific expenditures of net proceeds from this offering will depend on a number of factors, including the timing, scope, progress and results of our development efforts and the timing and progress of any collaboration efforts. As of the date of this prospectus, we cannot specify with certainty all of the particular uses of the proceeds from this offering. Accordingly, we will retain broad discretion over the use of such proceeds.

DIVIDEND POLICY

We have never declared or paid any cash dividends on our common stock. We would have to rely upon dividends and other payments from our wholly-owned subsidiary, ABT Holding Company, to generate the funds necessary to make dividend payments, if any, on our common stock. ABT Holding Company, however, is legally distinct from us and has no obligation to pay amounts to us. We do not anticipate that we will pay any dividends on our common stock in the foreseeable future. Rather, we anticipate that we will retain earnings, if any, for use in the development of our business. Payment of future cash dividends, if any, will be at the discretion of our board of directors after taking into account various factors, including our financial condition, operating results, current and anticipated cash needs, the requirements of then-existing debt instruments, and other factors that the board of directors deems relevant.

225

~~CAPITALIZATION~~Table of Contents

~~The~~DESCRIPTION ~~following~~OF ~~table sets forth our cash and cash equivalents and our capitalization as of March 31, 2023:~~SECURITIES

• on an actual basis;

• on a pro forma basis to give effect to the receipt of $3,380,347 of net proceeds from the issuance of 2,315,000 shares of common stock in the April 2023 Offerings, the receipt of $81 of proceeds upon exercise of 813,000 shares of common stock underlying the pre-funded warrants issued in the April 2023 Offerings, and the vesting of 367,664 restricted stock units; and

• on a pro forma as adjusted basis to give effect to our issuance and sale of shares of our common stock in this offering at the assumed public offering price of $ per share, which is the last reported sale price of our common stock on Nasdaq on , 2023, and after deducting placement agent fees and estimated offering expenses payable by us.

The as adjusted information below is illustrative only, and our capitalization following the completion of this offering is subject to adjustment based on the actual public offering price of our common stock and other terms of this offering determined at pricing. You should read the information in this table together with our financial statements and the related notes appearing elsewhere in this prospectus and the “Management’s Discussion and Analysis of Financial Condition and Results of Operations” sections of our most recent Annual Report on Form 10-K and Quarterly Report on Form 10-Q.

		As of March 31, 2023
		Actual			Pro Forma			As Adjusted (1)(2)
		(in thousands except share and per share data)
Cash and cash equivalents		$	3,121		$	6,366
Warrant liabilities and note payable		$	(1,163	)	$	(1,163	)	$	(1,163	)
Stockholders’ equity:
	Preferred stock, at stated value; 10,000,000 shares authorized, and no shares issued and outstanding at March 31, 2023, actual and as adjusted		—			—
	Common stock, $0.001 par value; 600,000,000 shares authorized, and 18,448,489 shares issued and outstanding at March 31, 2023, actual, and shares issued and outstanding at March 31, 2023, as adjusted		18			22
	Additional paid-in capital		632,660			635,917
	Accumulated deficit		(663,689	)		(663,705	)		(663,705	)
Total stockholders’ equity			(31,011	)		(27,766	)
Total capitalization		$	(32,174	)	$	(28,929	)

(1) A $0.25 increase (decrease) in the assumed public offering price of $ per share, which is the last reported sale price of our common stock on Nasdaq on , 2023, would increase (decrease) each of our as adjusted cash and cash equivalents, common stock, total stockholders’ (deficit) equity and total capitalization by approximately $ million, assuming the number of shares offered by us, as set forth on the cover page of this prospectus, remains the same, and after deducting placement agent’s fees and estimated offering expenses payable by us. Similarly, each increase (decrease) of 1,000,000 shares in the number of shares of common stock offered by us would increase (decrease) each of our as adjusted cash and cash equivalents, common stock, total stockholders’ (deficit) equity and total capitalization by approximately $ million, assuming the assumed public offering price of $ per share, which is the last reported sale price of our common stock on Nasdaq on , 2023, remains the same, and after deducting placement agent fees and estimated offering expenses payable by us.

(2) The foregoing discussion and table above exclude, as of March 31, 2023, the following:

• a total of 1,626,312 shares of common stock authorized and reserved for future issuance under outstanding awards under our equity incentive plans;

• a total of 27,491 shares of common stock authorized and reserved for future issuance under our equity incentive plans;

• a total of 429,500 shares of common stock authorized and reserved for future issuance under outstanding inducement awards granted outside of our equity incentive plans;

• 1,920,000 shares of common stock authorized and reserved for future issuance upon exercise of warrants issued and sold in August 2022;

• 2,000,000 shares of common stock authorized and reserved for future issuance upon exercise of warrants issued in September 2022;

• a total of 9,109,090 shares of common stock authorized and reserved for future issuance upon exercise of warrants issued in connection with our November 2022 public offering;

• a total of 3,685,000 shares of common stock authorized and reserved for future issuance upon exercise of warrants issued in connection with our April 2023 public offering;

• a total of 11,538,461 shares of common stock authorized and reserved for future issuance upon conversation feature of our May 2023 Convertible Note; and

• 400,000 shares of common stock authorized and reserved for future issuance upon exercise of warrants held by Healios.

DILUTION

If you invest in our securities in this offering, your ownership interest will be diluted immediately to the extent of the difference between the public offering price per share of our common stock and the pro forma as adjusted net tangible book value per share of our common stock immediately after this offering.

As of March 31, 2023, we had a historical net tangible book value of -$31.01 million, or -$1.681 per share of common stock, based on the 18,448,489 shares of common stock outstanding as of such date. Our historical net tangible book value (deficit) is the amount of our total tangible assets less our total liabilities. Our historical net tangible book value (deficit) per share represents historical net tangible book value (deficit) divided by the number of shares of our common stock outstanding as of March 31, 2023.

After giving effect to our issuance and sale of shares of common stock in this offering at the assumed public offering price of $ per share, which is the last reported sale price of our common stock on Nasdaq on , 2023, assuming no sale of any Pre-Funded Warrants and no exercise of the Common Warrants issued in connection with this offering, and after deducting placement agent fees and estimated offering expenses payable by us, our pro forma as adjusted net tangible book value as of would have been $ million, or $ per share. This amount represents an immediate increase in our pro forma as adjusted net tangible book value of $ per share to our existing stockholders and an immediate dilution in our pro forma as adjusted net tangible book value of $ per share to investors purchasing shares of our common stock in this offering. We determine dilution per share to investors participating in this offering by subtracting pro forma as adjusted net tangible book value per share after this offering from the assumed initial public offering price per share paid by investors participating in this offering.

The following table illustrates this dilution on a per share basis:

Assumed public offering price per share			$
Pro forma net tangible book value per share as of March 31, 2023	$
Increase in net tangible book value (deficit) per share attributable to equity transactions since March 31, 2023	$	0.42
Increase in net tangible book value (deficit) per share attributable to new investors purchasing common stock in this offering	$
Pro forma as adjusted net tangible book value (deficit) per share after giving effect to this offering			$
Dilution in pro forma as adjusted net tangible book value (deficit) per share to new investors purchasing common stock in this offering			$

The dilution information discussed above is illustrative only and may change based on the actual public offering price and other terms of this offering. Each $0.25 increase or decrease in the assumed public offering price of $ per share, which is the last reported sale price of our common stock on Nasdaq on , 2023, would increase or decrease, as applicable, our pro forma as adjusted net tangible book value per share after this offering by $ per share and increase or decrease, as applicable, the dilution to investors purchasing shares in this offering by $ per share, in each case assuming the number of shares of common stock offered by us, as set forth on the cover page of this prospectus, remains the same, assuming no sale of any Pre-Funded Warrants and no exercise of the Common Warrants issued in connection with this offering, and after deducting placement agent fees and estimated offering expenses payable by us. Similarly, an increase of 1,000,000 in the number of shares of common stock offered by us would increase the pro forma as adjusted net tangible book value after this offering by $ per share and decrease the dilution per share to new investors participating in this offering by $ per share, and a decrease of 1,000,000 shares of common stock offered by us would decrease the pro forma as adjusted net tangible book value by $ per share, and increase the dilution per share to new investors in this offering by $ per share, in each case assuming the assumed public offering price of $ per share, which is the last reported sale price of our common stock on Nasdaq on , 2023, remains the same, assuming no sale of any Pre-Funded Warrants and no exercise of the Common Warrants issued in connection with this offering, and after deducting placement agent fees and estimated offering expenses payable by us.

The as adjusted number of shares of common stock outstanding after this offering includes the following:

• 18,448,489 shares of common stock outstanding as of March 31, 2023;

• shares of common stock to be issued at the closing of this offering.

The pro forma as adjusted number of shares of common stock outstanding after this offering excludes, as of March 31, 2023, the following:

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