UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d)

of the Securities Exchange Act of 1934

Date of Report (Date of earliest event reported): ~~July 1~~August 14, 2025

IGM Biosciences, Inc.

(Exact name of Registrant as Specified in Its Charter)

Delaware		001-39045		77-0349194
(State or Other Jurisdictionof Incorporation)		(~~CommissionFile~~Commission File Number)		(IRS EmployerIdentification No.)

Address Not Applicable1		94043
(Address of Principal Executive Offices)		(Zip Code)

Address Not Applicable¹

~~Registrant’s~~(Address, ~~Telephone~~including ~~Number~~zip code, ~~Including~~of ~~Area~~Registrant’s ~~Code:~~Principal ~~(650)~~Executive ~~965-7873~~Offices)

(650) 965-7873

(Registrant’s Telephone Number, Including Area Code)

Not Applicable

(Former Name or Former Address, if Changed Since Last Report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

☐

Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

☐

Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

☐

Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

☐

Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

Securities registered pursuant to Section 12(b) of the Act:

Title of each class		TradingSymbol(s)		Name of each ~~exchangeon~~exchange on which registered
Common Stock, par value $0.01 per share		IGMS		The Nasdaq Global Select Market

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§ 230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§ 240.12b-2 of this chapter).

Emerging growth 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 pursuant to Section 13(a) of the Exchange Act. ☐

1 IGM Biosciences, Inc. (the “Registrant”) terminated its lease agreements for office space. Accordingly, the Registrant does not maintain headquarters. For purposes of compliance with applicable requirements of the Securities Act of 1933, as amended, and Securities Exchange Act of 1934, as amended, any stockholder communication required to be sent to the Registrant’s principal executive offices may be sent to IGM Biosciences, Inc., 3 East Third Avenue, Suite 200, San Mateo, CA, 94401.

Item 12.01 ~~Entry~~Completion ~~into~~of aAcquisition ~~Material~~or ~~Definitive~~Disposition ~~Agreement~~of Assets.

As previously disclosed by IGM Biosciences, Inc. (the “Company” or “IGM”) in the Company’s Current Report on Form 8-K filed with the Securities and Exchange Commission (the “SEC”) on July 1, 2025, the Company entered into an Agreement and Plan of Merger, dated as of July 1, 2025 (the “Merger Agreement”) with Concentra Biosciences, LLC, a Delaware limited liability company (“Parent”), and Concentra Merger Sub V, Inc., a Delaware corporation and a wholly owned subsidiary of Parent (“Merger Sub”).

OnPursuant ~~July 1,~~to ~~2025,~~the ~~IGM~~Merger ~~Biosciences~~Agreement, ~~Inc.~~and (upon the ~~“Company”)~~terms ~~entered into an Agreement~~ and ~~Plan~~subject ofto ~~Merger (~~the ~~“Merger~~conditions ~~Agreement”)~~thereof, ~~with~~on ~~Concentra Biosciences~~August 14, ~~LLC~~2025, aParent ~~Delaware~~completed ~~limited~~a ~~liability~~tender ~~company~~offer ~~(“Concentra”),~~to ~~and~~purchase ~~Concentra~~all ~~Merger~~of ~~Sub~~the V,Company’s ~~Inc.,~~outstanding ashares ~~Delaware~~of ~~corporation~~common ~~and~~stock, apar ~~wholly~~value ~~owned~~$0.01 ~~subsidiary~~per ofshare ~~Concentra~~ (the “~~Merger~~Common ~~Sub~~Stock”). ~~The~~and ~~Merger~~shares ~~Agreement~~of ~~provides~~Common ~~for~~Stock, ~~among~~“Shares”), ~~other~~in ~~things:~~exchange for (i) ~~the~~ ~~acquisition~~$1.247 ofin ~~all~~cash ofper Share (the ~~Company’s~~“Cash ~~outstanding~~Amount”); ~~shares~~plus of(ii) one ~~common~~non-transferable ~~stock,~~contractual ~~par~~contingent value ~~$0.01~~right per ~~share~~Share (~~the~~each, ~~“Common~~a ~~Stock”)~~“CVR,” byand ~~Concentra~~each ~~through~~CVR atogether ~~cash~~with ~~tender~~the ~~offer~~Cash (Amount, the “Offer Price”), ~~for~~which aCVR ~~price~~represents ~~per~~the ~~share~~right ofto receive potential payments pursuant to the ~~Common~~terms ~~Stock~~and subject to the conditions of ~~(A)~~the ~~$1.247~~contingent invalue ~~cash~~rights agreement (the “~~Cash~~CVR ~~Amount~~Agreement”), ~~subject~~dated toAugust 14, ~~applicable~~2025, ~~tax~~by ~~withholding~~ and ~~without~~among ~~interest;~~Parent, ~~plus~~Merger ~~(B) one~~Sub, ~~contingent~~Broadridge ~~value~~Corporate ~~right~~Issuer (Solutions, LLC, a ~~“CVR”)~~Pennsylvania ~~(such~~limited ~~amount~~liability ~~being~~company, ~~the~~and ~~“CVR~~Fortis ~~Amount”~~Advisors LLC, a Delaware limited liability company, all subject to and in accordance with the ~~Cash~~terms ~~Amount~~and ~~plus~~conditions set forth in the ~~CVR~~Offer ~~Amount~~to Purchase, ~~collectively~~dated ~~being~~July 16, 2025 ( the “Offer ~~Price~~to Purchase”), and ~~(ii)~~ in the ~~merger~~related Letter of ~~Merger~~Transmittal ~~Sub~~(as ~~with~~amended ~~and~~or ~~into~~supplemented ~~the~~from ~~Company~~time (to time, the “~~Merger~~Letter of Transmittal,”) which, together with the ~~Company~~Offer ~~surviving~~to Purchase, as each may have been amended or supplemented, constituted the ~~Merger~~“Offer”).

The ~~Company’s~~Offer ~~Board~~expired ofone ~~Directors~~minute ~~(the~~after ~~“Board”),~~11:59 ~~has~~p.m. ~~unanimously:~~Eastern ~~(i) determined~~Time ~~that~~on ~~the~~Wednesday, ~~Offer~~August 13, ~~the~~2025. ~~Merger~~According ~~and~~to ~~the~~Broadridge ~~other~~Corporate ~~transactions~~Issuer ~~contemplated~~Solutions, byLLC, the ~~Merger~~depositary ~~Agreement~~for ~~and~~ the ~~CVR Agreement (as defined below) (collectively~~Offer, ~~the~~a ~~“Transactions”)~~total ~~are~~of ~~fair to~~28,373,092 ~~and~~voting inShares ~~the~~were ~~best~~validly ~~interest of~~tendered, ~~the Company~~ and ~~its~~not ~~stockholders;~~validly ~~(ii) approved and declared advisable the Merger and the execution~~withdrawn, ~~delivery~~representing ~~and~~approximately ~~performance~~77.53% ~~by the Company~~ of the ~~Merger~~outstanding ~~Agreement~~voting ~~and~~Shares. ~~the~~The ~~consummation~~number of ~~the~~voting ~~Transactions;~~Shares ~~(iii) resolved~~tendered ~~that~~satisfied the ~~Merger~~Minimum ~~Agreement~~Tender ~~and~~Condition ~~the Merger shall be governed by and effected under Section 251~~(~~h) of the Delaware General Corporation Law (the “DGCL”) and that the Merger shall be consummated~~ as ~~soon as practicable following the Offer Closing Time (as~~ defined in the Merger Agreement);. ~~and~~All ~~(iv) recommended~~other ~~that~~conditions ~~the Company’s stockholders accept the Offer and tender their shares of Common Stock pursuant~~ to the Offer. ~~Under~~were ~~the~~satisfied ~~Merger~~and ~~Agreement,~~Parent ~~Concentra~~accepted isfor ~~required~~payment toall ~~commence~~Shares ~~the~~validly ~~Offer~~tendered ~~as promptly as practicable,~~ (and innot ~~any~~validly ~~event no later than ten (10~~withdrawn) ~~business~~ ~~days~~prior ~~after~~to the ~~date~~expiration of the ~~Merger Agreement~~Offer.

~~Pursuant~~Following to the ~~terms~~consummation of the ~~Merger Agreement~~Offer, asthe ofremaining ~~immediately~~conditions ~~prior~~ to the ~~effective~~Merger ~~time~~set offorth in the Merger ~~(the~~Agreement ~~“Effective~~were ~~Time”)~~satisfied, ~~by virtue of the Merger~~ and ~~without any action~~ on ~~the part of the holders of Common Stock: (i)~~August ~~each outstanding share of Common Stock~~14, ~~other~~2025 ~~than any shares of Common Stock held in~~ (the ~~treasury~~“Closing ~~of the Company~~Date”), ~~owned by Concentra,~~ Merger Sub ormerged ~~any~~with ~~other subsidiary of Concentra, or by any stockholders of the Company who are entitled to~~ and ~~who properly exercise appraisal rights under Delaware law, will be converted~~ into the ~~right~~Company ~~to receive the Offer Price without interest, less any applicable withholding taxes;~~ (~~ii) (A) each option to purchase shares of Common Stock from~~ the ~~Company (~~“~~Company Stock Options,~~Merger” ~~and each~~), athe ~~“Company~~separate ~~Stock~~corporate ~~Option”)~~existence ~~that~~of isMerger ~~then~~Sub ~~outstanding~~ceased ~~but not then vested or exercisable shall become immediately vested~~ and ~~exercisable~~the ~~in full, (B) each~~ Company ~~Stock~~continued ~~Option~~as ~~that~~the ~~has~~surviving ancorporation ~~exercise~~in ~~price per share that is less than~~ the ~~Cash~~Merger ~~Amount~~ (~~each,~~the an “~~In-the-Money~~Surviving ~~Option~~Corporation”) ~~that is then outstanding will be cancelled~~ and, ina ~~exchange~~wholly ~~therefor,~~owned ~~the~~subsidiary ~~holder~~ of ~~such~~Parent. ~~cancelled~~The ~~In-the-Money~~Merger ~~Option~~was ~~will~~completed bepursuant ~~entitled~~ to ~~receive in consideration of the cancellation of such In-the-Money Option (x)~~Section ~~an amount in cash without interest, less any applicable tax withholding, equal to the product obtained by multiplying~~ 251(1h) ~~the~~ ~~excess~~ of the ~~Cash~~General ~~Amount~~Corporation ~~over~~Law ~~the exercise price per share~~ of ~~Common Stock underlying such In-~~the~~-Money~~ ~~Option~~State ~~by (2) the number~~ of ~~shares~~Delaware, ~~of Common Stock underlying such In-the-Money Option~~ as ofamended ~~immediately prior to the Effective Time and~~ (~~y) one CVR for each share of Common Stock underlying such In-~~the~~-Money~~ ~~Option~~“DGCL”), ~~and~~with ~~(C) each~~no ~~Company~~stockholder ~~Stock~~vote ~~Option~~required. ~~that~~At ~~has an exercise price per share that is equal to or greater than~~ the ~~Cash~~effective ~~Amount~~time ~~that is then outstanding will be cancelled for no consideration; and (iii) the vesting for each restricted stock unit~~ of the ~~Company~~Merger (~~“Company~~the ~~Restricted Stock Units,” and each, a~~ “~~Company~~Effective ~~Restricted Stock Unit~~Time”), ~~shall be accelerated and~~ each ~~Company Restricted Stock Unit that is then~~ outstanding ~~will be cancelled and~~Share, inother ~~exchange~~than ~~therefor,~~any ~~the~~Shares ~~holder~~held ~~of such cancelled Company Restricted Stock Unit will be entitled to receive~~ in ~~consideration of~~ the ~~cancellation~~treasury of ~~such~~the Company ~~Restricted Stock Unit (A) an amount in cash without interest~~, ~~less~~owned ~~any~~by ~~applicable tax withholding~~Parent, ~~equal~~Merger toSub ~~the~~or ~~Cash~~any ~~Amount~~other ~~and~~subsidiary ~~(B) one~~of ~~CVR. In addition~~Parent, ator ~~the~~by ~~Effective~~any ~~Time,~~stockholders ~~each~~of ~~pre-funded warrant~~the ~~(each, a “~~Company ~~Pre-Funded~~who ~~Warrant”)~~are toentitled ~~purchase Common Stock sold pursuant~~ to ~~that certain Underwriting Agreement, dated as of December 8, 2020, by~~ and ~~among~~who ~~the~~properly ~~Company~~exercise ~~and~~appraisal ~~the~~rights ~~representatives~~under ofDelaware ~~the several underwriters named therein~~law, ~~shall~~was beconverted ~~canceled~~into ~~and~~ the ~~holder~~right ~~thereof shall be entitled~~ to receive: ~~(x) an~~the ~~amount~~Offer inPrice ~~cash~~ without interest, less any applicable ~~tax~~ withholding, equal to the product obtained by multiplying (A) the excess of the Cash Amount over the exercise price per share of Common Stock underlying such Company Pre-Funded Warrant by (B) the number of shares of the Common Stock underlying such Company Pre-Funded Warrant; and (ii) one CVR for each share of Common Stock underlying such Company Pre-Funded Warranttaxes.

~~Concentra’s~~Pursuant ~~obligation~~ to ~~accept~~the ~~shares~~terms of ~~Common~~the ~~Stock~~Merger ~~tendered~~Agreement, inat the ~~Offer~~Effective isTime, ~~subject~~by tovirtue ~~conditions,~~of ~~including:~~the Merger and without any action on the part of the holders, (i) ~~that~~each option to purchase Shares from the ~~number~~Company of(each, ~~shares~~a of“Company ~~voting~~Stock ~~Common~~Option”) was accelerated and (A) each Company Stock ~~validly~~Option ~~tendered~~with an exercise price per share less than the Cash Amount (~~and~~each, ~~not~~an ~~properly~~“In-the-Money ~~withdrawn~~Option”) ~~prior~~was tocancelled and, in exchange therefor, the ~~expiration~~holder of such cancelled In-the-Money ~~Offer~~Option ~~(excluding~~received ~~shares~~in ~~tendered~~consideration ~~pursuant~~of tothe ~~guaranteed~~cancellation ~~delivery~~of ~~procedures~~such ~~that~~In-the-Money ~~have~~Option ~~not~~(x) an ~~yet~~amount ~~been~~in ~~“received”~~cash bywithout ~~the~~interest, ~~“depository~~less any applicable tax withholding,” asequal ~~such~~to ~~terms~~the ~~are~~product ~~defined~~obtained by ~~Section 251~~multiplying (h1) the excess of the ~~DGCL)~~Cash ~~that,~~Amount ~~when~~over ~~considered~~the ~~together~~exercise ~~with~~price ~~all~~per ~~other~~Share ~~shares~~underlying ofsuch In-the-Money ~~voting~~Option ~~Common~~by ~~Stock~~ (~~if any~~2) the ~~owned~~number byof ~~Concentra~~Shares ~~and~~underlying ~~its~~such ~~“affiliates”~~In-the-Money (Option as ~~defined~~of inimmediately ~~Section 251(h)(6)(a)~~prior ofto the ~~DGCL),~~Effective ~~equals~~Time atand ~~least~~ (y) one ~~share~~CVR ~~more~~for ~~than~~each ~~50%~~Share ofunderlying ~~all~~such ~~shares~~In-the-Money ofOption, ~~voting~~and ~~Common~~(B) each Company Stock ~~then~~Option ~~issued~~that ~~and~~had ~~outstanding~~an asexercise ofprice ~~the~~per ~~expiration~~share ofequal to or greater than the ~~Offer~~Cash Amount was cancelled for no consideration; (ii) the ~~absence~~vesting offor ~~any~~each ~~Legal~~restricted ~~Restraint~~stock unit of the Company (aseach, ~~defined~~a in“Company ~~the~~Restricted ~~Merger~~Stock ~~Agreement~~Unit”) inwas ~~effect~~accelerated ~~preventing~~and oreach ~~prohibiting~~Company ~~the~~Restricted ~~consummation~~Stock ofUnit ~~the~~that ~~Offer~~was outstanding was cancelled and, ~~the~~in ~~Merger~~exchange ortherefor, ~~any~~the holder of ~~the~~such ~~other~~cancelled ~~transactions~~Company ~~contemplated~~Restricted byStock ~~the~~Unit ~~Merger~~received ~~Agreement~~in orconsideration of the ~~CVR~~cancellation ~~Agreement;~~of such Company Restricted Stock Unit (~~iii~~A) ~~the~~an ~~accuracy~~amount ofin cash without interest, less any applicable tax withholding, equal to the ~~representations~~Cash Amount and ~~warranties~~(B) one ~~made~~CVR. byIn addition, at the Effective Time, each pre-funded warrant (each, a “Company Pre-Funded Warrant”) into ~~the~~purchase ~~Merger~~Common ~~Agreement,~~Stock ~~subject~~sold pursuant to ~~specified~~that ~~materiality~~certain ~~qualifications~~Underwriting ~~and~~Agreement, ~~exceptions;~~dated ~~(iv)~~as of December ~~compliance~~8, 2020, by and among the Company ~~with~~and ~~its~~the ~~covenants~~representatives ~~under~~of the ~~Merger~~several ~~Agreement~~underwriters innamed ~~all~~therein, ~~material~~shall ~~respects;~~be canceled and ~~(v)~~ the ~~Closing~~holder ~~Net~~thereof ~~Cash~~received (asx) an ~~defined~~amount in cash without interest, less any applicable tax withholding, equal to the ~~Merger~~product ~~Agreement~~obtained by multiplying (A) the ~~shall~~excess beof nothe ~~less~~Cash ~~than~~Amount ~~$82 million.~~over ~~The~~the ~~obligations~~exercise price per share of ~~Concentra~~Common ~~and~~Stock ~~Merger~~underlying ~~Sub~~such toCompany Pre-Funded Warrant ~~consummate~~by (B) the ~~Offer~~number ~~and~~of shares of the ~~Merger~~Common ~~under~~Stock ~~the~~underlying ~~Merger~~such ~~Agreement~~Company Pre-Funded Warrant; ~~are~~and ~~not~~(y) one ~~subject~~CVR tofor aeach ~~financing~~share ~~condition~~of Common Stock underlying such Company Pre-Funded Warrant.

~~Following~~The ~~the~~foregoing ~~completion~~description of the ~~Offer,~~Merger ~~upon~~Agreement and the ~~terms~~CVR Agreement and ~~subject~~the totransactions ~~the~~contemplated ~~conditions~~thereby ofdoes ~~the~~not ~~Merger~~purport ~~Agreement,~~to ~~Merger~~be ~~Sub~~complete ~~will~~and ~~merge~~is ~~with~~qualified ~~and~~in ~~into~~its ~~the~~entirety ~~Company,~~by ~~with~~reference to the ~~Company~~full ~~surviving~~text asof athe ~~wholly~~Merger ~~owned~~Agreement ~~subsidiary~~attached ofas ~~Concentra,~~Exhibit ~~pursuant~~2.1 to the ~~procedure~~Current ~~provided~~Report ~~for~~on ~~under~~Form ~~Section 251(h)~~8-K offiled by the ~~DGCL,~~Company ~~without~~on ~~any~~July 1, ~~additional~~2025 ~~Company~~and ~~stockholder~~the ~~approvals.~~full ~~The~~text ~~Merger~~of ~~will~~the beCVR ~~effected~~Agreement asattached ~~soon~~ as ~~practicable~~Exhibit ~~following~~(d)(5) to the ~~time~~Schedule ofTO-T/A ~~purchase~~filed by ~~Concentra~~Parent ofon ~~shares~~August 14, of2025, ~~Common~~both ~~Stock~~of ~~validly~~which ~~tendered~~are ~~and~~incorporated ~~not~~herein ~~withdrawn~~by ~~in the Offer~~reference.

~~The~~Item ~~Merger~~3.01 ~~Agreement~~Notice ~~contains representations and warranties from both the Company, on the one hand, and Concentra and Merger Sub, on the other hand, customary for a transaction~~ of ~~this~~Delisting ~~nature.~~or ~~The~~Failure ~~Merger Agreement also contains customary covenants and agreements, including with respect~~ to ~~the~~Satisfy ~~operations~~a ofContinued ~~the~~Listing ~~business~~Rule ofor ~~the~~Standard; ~~Company~~Transfer ~~between the date~~ of ~~the Merger Agreement and the closing of the Merger~~Listing.

The ~~Merger~~information ~~Agreement~~set ~~contains~~forth customary termination rights for both Concentra and Merger Sub, on the one hand, and the Company, on the other hand, including, among others, for failure to consummate the Offer on or before September 29, 2025. If the Merger Agreement is terminated under ~~certain~~Item circumstances specified in the Merger Agreement, including in connection with the Company’s entry into an agreement with respect to a superior proposal, the Company will be required to pay Concentra a termination fee of $2.~~425 million.~~01 ~~If Concentra terminates the Merger Agreement due to the Company having Closing Net Cash~~ of ~~less~~this ~~than~~Current ~~$82.0 million,~~Report ~~the~~on ~~Company~~Form ~~will~~8-K beis ~~required~~incorporated toherein ~~reimburse expenses incurred~~ by ~~Concentra~~reference upinto tothis aItem ~~maximum amount of $0~~3.~~5 million~~01.

~~The~~In ~~foregoing~~connection ~~description~~with of the ~~Merger~~consummation ~~Agreement~~of ~~does~~the ~~not~~Offer ~~purport to be complete~~ and ~~is qualified in its entirety by reference to~~ the Merger ~~Agreement~~, ~~a copy of which is filed as Exhibit 2.1 hereto and is incorporated herein by reference. The Merger Agreement and~~ the ~~foregoing description thereof has been included to provide investors and security holders with information regarding its terms. It is not intended to provide any other factual information about the~~ Company, ~~Concentra,~~(i) notified ~~Merger Sub or their respective subsidiaries and affiliates.~~ The ~~Merger~~Nasdaq ~~Agreement~~Stock ~~contains~~Market ~~representations~~LLC ~~and~~(“Nasdaq”) ~~warranties~~of by the ~~Company,~~consummation onof the ~~one hand, and Concentra and~~ Merger ~~Sub, on the other hand, made solely for the benefit of the other. The assertions embodied in those representations~~ and ~~warranties~~(ii) requested ~~are~~that ~~subject~~Nasdaq to(A) suspend ~~qualifications~~trading ~~and limitations agreed to by the respective parties in negotiating the terms~~ of the ~~Merger~~Shares ~~Agreement,~~effective ~~including~~before ~~information in confidential disclosure schedules delivered in connection with~~ the ~~signing~~opening of ~~the~~trading ~~Merger~~on ~~Agreement. Moreover~~August 14, ~~certain~~2025 ~~representations~~ and ~~warranties~~(B) file inwith the ~~Merger~~SEC ~~Agreement were made as of~~ a ~~specified~~Notification ~~date, may be subject to a contractual standard~~ of ~~materiality~~Removal ~~different~~ from ~~what~~Listing ~~might~~and/or beRegistration ~~viewed~~on asForm ~~material~~25 to ~~investors,~~effect ~~or may have been used for~~ the ~~purpose~~delisting of ~~allocating~~all ~~risk~~Shares ~~between~~from ~~the~~Nasdaq ~~Company,~~and on the ~~one~~deregistration ~~hand,~~of ~~and~~such ~~Concentra~~Shares ~~and~~under ~~Merger~~Section 12(b) ~~Sub,~~of on the ~~other~~Securities ~~hand,~~Exchange ~~rather~~Act ~~than~~of ~~establishing~~1934, ~~matters~~ as ~~facts.~~amended ~~Accordingly,~~ (the ~~representations~~“Exchange ~~and~~Act”). ~~warranties~~In inaddition, the ~~Merger~~Surviving ~~Agreement~~Corporation ~~should~~intends ~~not~~to befile ~~relied~~a onCertification byand ~~any~~Notice ~~persons~~of asTermination ~~characterizations~~ of ~~the~~Registration ~~actual~~on ~~state~~Form of15 ~~facts~~with ~~about~~ the ~~Company,~~SEC ~~Concentra,~~requesting ~~Merger~~the ~~Sub~~termination orof ~~their~~registration ~~respective~~of ~~subsidiaries or affiliates at~~ the ~~time~~Shares ~~they~~under ~~were~~Section 12(g) ~~made~~of orthe ~~otherwise.~~Exchange InAct ~~addition,~~and ~~information concerning~~ the ~~subject~~suspension ~~matter~~ of ~~the~~reporting ~~representations~~obligations ~~and~~under ~~warranties~~Section 13 ~~may~~and ~~change~~15(d) ~~after the date~~ of the ~~Merger~~Exchange ~~Agreement,~~Act ~~which~~with ~~subsequent~~respect ~~information~~to ~~may or may not be fully reflected in~~ the ~~Company’s public disclosures~~Shares.

~~Limited~~Item ~~Guaranty~~3.03 Material Modification to Rights of Security Holders.

~~Concurrently~~The ~~with~~information ~~the~~set ~~execution~~forth ofunder ~~the~~Items ~~Merger Agreement and the CVR Agreement~~2.01, ~~and as a condition and inducement to the Company’s willingness to enter into the Merger Agreement~~3.01, ~~Tang~~5.01 Capital Partners, LP, a Delaware limited partnership, has delivered to the Company a duly executed limited guaranty, dated as of the date of the Merger Agreement, in favor of the Company, in respect of certain of Concentra and ~~the Merger Sub’s obligations arising under, or in connection with, the Merger Agreement and CVR Agreement~~5.03 ~~Certain obligations under the Limited Guaranty are subject to a cap~~ of ~~$78.0 million,~~this ~~plus~~Current ~~certain~~Report ~~enforcement~~on ~~costs,~~Form ~~under~~8-K ~~the~~is ~~Merger~~incorporated ~~Agreement~~by ~~and~~reference aninto ~~amount~~this ~~equivalent~~Item ~~to the CVR Proceeds (as defined in the CVR Agreement), plus certain enforcement costs, under the CVR Agreement~~3.03.

~~Contingent~~Item ~~Value~~5.01 ~~Rights~~Changes ~~Agreement~~in Control of Registrant.

AtThe orinformation ~~prior~~set toforth ~~the~~under ~~time~~Items at which Concentra first irrevocably accepts for purchase the shares of Common Stock tendered in the Offer, Concentra and Merger Sub expect to enter into a Contingent Value Rights Agreement (the “CVR Agreement”) with a rights agent (“Rights Agent”) and a representative, agent and attorney-in-fact of the holders of CVRs2. Each CVR will represent a contractual right to receive contingent cash payments equal to: (i) 100% of the amount by which Closing Net Cash (as finally determined pursuant to the Merger Agreement) exceeds $82.0 million01, ~~adjusted for any claims Concentra reasonably determines to be valid five (~~5~~) business~~.02 ~~days prior to the Merger Closing Date (as defined in the Merger Agreement)~~ and ~~that~~5.03 ~~are not accounted for in such Closing Net Cash; and (ii) 80%~~ of ~~the~~this ~~Net~~Current ~~Proceeds~~Report ~~(as~~on ~~defined~~Form in8-K ~~the~~is ~~CVR~~incorporated ~~Agreement), if any, from any sale, transfer, license or other disposition or grant of rights (each, a “Disposition”)~~ by ~~Concentra~~reference orinto ~~any~~this ofItem its affiliates, including the Company after the Merger, of all or any part of (a) the Company’s product candidates known as (A) imvotamab, an IgM-based CD20 X CD3 bispecific antibody T cell engager; (B) IGM-2644, an IgM-based CD38 X CD3 bispecific T cell engager; (C) aplitabart (or IGM-8444), a Death Receptor 5 ~~agonist; and~~.01.

As ~~(D) IGM-7354,~~ a ~~targeted~~result IL-15/IL-15R IgM antibody; (E) IGM-8447, an IgM-based Death Receptor 5 agonist; and (F) IGM-2537, an IgM-based CD123 X CD3 bispecific antibody T cell engager (the “CVR Product”) and (b) patents and patent applications owned or controlled by the Company immediately prior to the closing of the ~~Merger~~consummation ~~and set forth on Schedule 1~~ of the ~~CVR~~Offer ~~Agreement, together with all patents issuing thereon or claiming priority thereto, that occurs within the period beginning on the Merger Closing Date~~ and ~~ending on~~ the ~~first (1st) anniversary following the~~ Merger ~~Closing Date (the “Disposition Period”). In the event that no Dispositions occur by the first (1st) anniversary of the Merger Closing Date~~, ~~holders~~there ofwas ~~the CVRs will not receive any payment pursuant to the CVR Agreement with respect to~~ a ~~Disposition.~~change Concentra shall, and shall cause the Company after the Merger, to use commercially reasonable efforts to, among other things, during the Disposition Period: (i) enter into one or more Disposition Agreements (as defined in ~~the~~control ~~CVR Agreement) as soon as practicable following the Effective Time; (ii) retain an employee or consultant~~ of ~~Concentra or Merger Sub for~~ the ~~purpose of maintaining and preserving the CVR Products and~~ Company ~~Patents and seeking~~, ~~negotiating~~ and ~~executing Disposition Agreements; (iii) maintain~~ the ~~CVRs~~Company ~~(including~~became ~~fees~~a ~~and~~wholly ~~expenses~~owned ~~related~~subsidiary toof the Rights Agent and the Representative (each as defined in the CVR Agreement)); (iv) maintain and prosecute the intellectual property relating to the CVR Products and the intellectual property set forth on Schedule 1 to the CVR Agreement; and (v) continue the CMC Activities (as defined in the Merger Agreement)Parent.

~~The~~Item ~~right to the contingent payments contemplated by the CVR Agreement is a contractual right only and will not be transferable, except in the limited circumstances specified in the CVR Agreement~~5.02 ~~The~~Departures ~~CVRs~~of ~~will~~Directors ~~not be evidenced by a certificate~~ or ~~any~~Certain ~~other~~Officers; ~~instrument~~Election ~~and~~of ~~will~~Directors; ~~not~~Appointment beof ~~registered~~Certain ~~with~~Officers; ~~the~~Compensatory ~~U.S.~~Arrangements Securities and Exchange Commission (the “SEC”). The CVRs will not have any voting or dividend rights and will not represent any equity or ownership interest in Concentra, any constituent corporation party to the Merger or any of ~~their~~Certain ~~respective affiliates~~Officers.

~~The~~Pursuant ~~foregoing~~to ~~description~~the terms of the ~~CVR~~Merger Agreement, ~~does~~at ~~not~~the ~~purport~~Effective toTime, beeach ~~complete~~of ~~and~~Mary isBeth ~~qualified~~Harler, inM.D., ~~its~~Michael ~~entirety~~Lee, byM. ~~reference~~Kathleen toBehrens, ~~the~~Ph.D., ~~Form~~Julie ofHambleton, ~~CVR Agreement~~M.D., aChristina ~~copy~~Teng Topsøe, Jakob Haldor Topsøe, Felix J. Baker, Ph.D., William Strohl, Ph.D., and Elizabeth H.Z. Thompson, Ph.D., resigned from the board of ~~which~~directors isof ~~filed~~the Company. These resignations were tendered in connection with the Merger and not as ~~Exhibit~~a ~~10.1~~result ~~hereto~~of any disagreements between the Company and isthe ~~incorporated~~resigning ~~herein~~individuals byon ~~reference~~any matters related to the Company’s operations, policies, or practices.

~~The~~Following ~~CVR~~the ~~Agreement~~Merger and ~~the~~pursuant ~~foregoing description thereof has been included~~ to ~~provide~~the ~~investors and security holders with information regarding its~~ terms. Itof ~~is not intended to provide any other factual information about~~ the ~~Company, Concentra,~~ Merger ~~Sub or their respective subsidiaries and affiliates. The CVR~~ Agreement, ~~contains~~at ~~representations and warranties by~~ the ~~Company~~Effective Time, on the ~~one~~directors ~~hand,~~ and ~~Concentra~~officers ~~and~~of Merger Sub, onimmediately ~~the~~prior ~~other hand, made solely for the benefit of the other. The assertions embodied in those representations and warranties are subject~~ to ~~qualifications and limitations agreed to by~~ the ~~respective~~Effective ~~parties~~Time inbecame ~~negotiating~~ the ~~terms~~directors ofand ~~the~~officers ~~CVR Agreement, including information in confidential disclosure schedules delivered in connection with the signing~~ of the ~~Merger~~Surviving ~~Agreement~~Corporation. ~~Moreover,~~The ~~certain~~sole ~~representations~~director ~~and warranties in the CVR Agreement were made as~~ of aMerger ~~specified~~Sub ~~date,~~immediately ~~may~~prior ~~be subject~~ to ~~a contractual standard of materiality different from what might be viewed as material to investors, or may have been used for~~ the ~~purpose~~Effective ofTime ~~allocating~~was ~~risk~~Kevin ~~between the Company, on the one hand, and Concentra and Merger Sub, on the other hand, rather than establishing matters as facts~~Tang. ~~Accordingly,~~The ~~the~~executive ~~representations~~officers ~~and warranties in the CVR Agreement should not be relied on by any persons as characterizations~~ of ~~the actual state of facts about the Company, Concentra,~~ Merger Sub orimmediately ~~their~~prior ~~respective~~to ~~subsidiaries or affiliates at~~ the ~~time~~Effective ~~they~~Time were: ~~made or otherwise~~(i) Mr. ~~In addition~~ Tang, ~~information~~Chief ~~concerning~~Executive ~~the~~Officer; ~~subject~~(ii) Michael ~~matter~~Hearne, ofChief ~~the~~Financial ~~representations~~Officer; ~~and~~(iii) Ryan ~~warranties~~Cole, ~~may~~Chief ~~change~~Operating ~~after~~Officer; ~~the date of the CVR~~(iv) ~~Agreement~~Stew Kroll, ~~which~~Chief ~~subsequent~~Development ~~information~~Officer; ~~may~~and or(v) Thomas ~~may~~Wei, ~~not~~Chief beBusiness ~~fully reflected in the Company’s public disclosures~~Officer.

~~Item~~Information ~~5.02.~~regarding ~~Departure~~the new director and executive officers of ~~Directors~~the orSurviving ~~Certain~~Corporation ~~Officers;~~has ~~Election~~been ofpreviously ~~Directors;~~disclosed ~~Appointment~~in ofSchedule ~~Certain~~A ~~Officers;~~to ~~Compensation~~the ~~Arrangements~~Offer ofto ~~Certain~~Purchase, ~~Officers~~which is incorporated herein by reference.

~~Departures~~Item 5.03 Amendments to Articles of ~~Section~~Incorporation 16or ~~Officers~~Bylaws; Change in Fiscal Year.

InPursuant ~~connection~~to ~~with~~ the ~~transactions~~terms ~~contemplated~~of by the Merger Agreement, onat ~~July 1, 2025, (1)~~ the ~~employment~~Effective ~~of Misbah Tahir~~Time, the Company’s ~~Chief~~certificate ~~Financial Officer, has been terminated effective as~~ of ~~August 1,~~incorporation ~~2025;~~and ~~(2)~~bylaws ~~the~~were ~~employment~~amended ofand ~~Steven~~restated ~~Weber,~~in ~~the~~their ~~Company’s Senior Vice President~~entirety, ~~Corporate Controller and Principal Accounting Officer, has been terminated effective~~ as ofset ~~July 11,~~forth ~~2025;~~on ~~and~~Exhibits (3~~) the employment of Lisa L~~. ~~Decker, the Company’s Chief Business Officer, has been terminated effective as of August~~ 1, ~~2025.~~and Mr3. ~~Tahir~~2, ~~Mr. Weber~~respectively, ~~and Dr. Decker may continue~~ to ~~assist~~this ~~the~~Current ~~Company~~Report ason ~~consultants~~Form ~~after~~8-K ~~each~~and ofare ~~their~~incorporated ~~last~~herein ~~day~~by ~~of employment with the Company in order to support the transition of their responsibilities~~reference.

In addition, it is expected that the employment of Mary Beth Harler, the Company’s Chief Executive Officer, will be terminated effective as of the Effective Time.

Item 7.01 Regulation FD Disclosure.

On July 1, 2025, the Company issued a press release announcing the signing of the Merger Agreement, a copy of which is attached hereto as Exhibit 99.1 and incorporated by reference herein.

The information contained in this Item 7.01, including Exhibit 99.1 attached hereto, is being furnished and shall not be deemed “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), or otherwise subject to the liabilities of that section, nor shall it be deemed incorporated by reference into any filing under the Securities Act of 1933, as amended, or the Exchange Act, except as expressly set forth by specific reference in such filing.

Important Additional Information and Where to Find It

The Offer described in this communication has not yet commenced, and this communication is neither a recommendation, nor an offer to purchase nor a solicitation of an offer to sell any shares of the common stock of the Company or any other securities, nor is it a substitute for the tender offer materials that Concentra and Merger Sub will file with the SEC on commencement of the Offer. On the commencement date of the Offer, Concentra and Merger Sub will file with the SEC a tender offer statement on Schedule TO, including an offer to purchase, a letter of transmittal and related documents, and the Company will file with the SEC a Solicitation/Recommendation Statement on Schedule 14D-9. The Offer to purchase the outstanding shares of Common Stock will only be made pursuant to the offer to purchase, the letter of transmittal and related documents filed as a part of the Schedule TO.

INVESTORS AND SECURITY HOLDERS ARE URGED TO READ THE TENDER OFFER MATERIALS (INCLUDING THE OFFER TO PURCHASE, A LETTER OF TRANSMITTAL AND RELATED DOCUMENTS) AND THE SOLICITATION/RECOMMENDATION STATEMENT ON SCHEDULE 14D-9 REGARDING THE OFFER, AS THEY MAY BE AMENDED OR SUPPLEMENTED FROM TIME TO TIME, WHEN THEY BECOME AVAILABLE BECAUSE THEY WILL CONTAIN IMPORTANT INFORMATION THAT INVESTORS AND SECURITY HOLDERS SHOULD CONSIDER BEFORE MAKING ANY DECISION REGARDING TENDERING THEIR SHARES, INCLUDING THE TERMS AND CONDITIONS OF THE OFFER.

Investors and security holders may obtain a free copy of these statements (when available) and other documents filed with the SEC at the website maintained by the SEC at www.sec.gov or by directing such requests to the information agent for the Offer, which will be named in the tender offer statement. Investors and security holders may also obtain, at no charge, the documents filed or furnished to the SEC by the Company under the “SEC Filings” subsection of the Company’s website at https://investor.igmbio.com/. The information contained in, or that can be accessed through, the Company’s website is not a part of, or incorporated by reference herein. In addition to the Offer to Purchase, the related Letter of Transmittal and certain other tender offer documents, as well as the Solicitation/Recommendation Statement, the Company files annual, quarterly, and current reports, proxy statements and other information with the SEC. You may read any reports, statements or other information filed by the Company with the SEC for free on the SEC’s website at www.sec.gov.

Cautionary Note Regarding Forward-Looking Statements

This Current Report on Form 8-K contains “forward-looking statements” within the meaning of the Private Securities Litigation Reform Act of 1995, including, but not limited to, statements regarding the Company’s beliefs and expectations and statements about the Offer, the Merger and the other Transactions, the ability to complete the transactions contemplated by the Merger Agreement, including the ability to satisfy the conditions to the consummation of the Offer contemplated thereby and the other conditions set forth in the Merger Agreement, the timing of the Transactions, the potential effects of the proposed Transactions on the Company and the potential payment of proceeds to the Company’s stockholders, if any, pursuant to the CVR Agreement. These statements may be identified by their use of forward-looking terminology including, but not limited to, “anticipate,” “believe,” “continue,” “could,” “estimate,” “expect,” “goal,” “intend,” “may,” “might,” “plan,” “potential,” “predict,” “project,” “should,” “target,” “will,” and “would,” and similar words expressions are intended to identify forward-looking statements. Forward-looking statements are neither historical facts nor assurances of future performance and involve risks and uncertainties that could cause actual results to differ

materially from those projected, expressed or implied by such forward-looking statements. These risks and uncertainties include, but are not limited to: the possibility that various closing conditions set forth in the Merger Agreement may not be satisfied or waived, including uncertainties as to the percentage of the Company’s stockholders tendering their shares in the Offer; the possibility that competing offers will be made; the risk that the Transactions may not be completed in a timely manner, or at all, which may adversely affect the Company’s business and the price of its common stock; significant costs associated with the proposed Transactions; the risk that any stockholder litigation in connection with the Transactions may result in significant costs of defense, indemnification and liability; the risk that activities related to the CVR Agreement may not result in any value to the Company’s stockholders; and other risks and uncertainties discussed in the Company’s most recent Annual Report on Form 10-K filed with the SEC on March 6, 2025 and the Amendment No. 1 to Annual Report on Form 10-K filed with the SEC on April 30, 2025 as well as in the Company’s subsequent filings with the SEC. As a result of such risks and uncertainties, the Company’s actual results may differ materially from any future results, performance or achievements discussed in or implied by the forward-looking statements contained herein. There can be no assurance that the proposed Transactions will in fact be consummated. The Company cautions investors not to unduly rely on any forward-looking statements.

The forward-looking statements contained in this Current Report on Form 8-K are made as of the date hereof, and the Company undertakes no obligation to update any forward-looking statements, whether as a result of future events, new information or otherwise, except as expressly required by law. All forward-looking statements in this document are qualified in their entirety by this cautionary statement.

Item 9.01

Financial Statements and Exhibits.

(d) Exhibits

No.		Description of Exhibit
2.1+		Agreement and Plan of Merger, dated July 1, 2025, by and among Concentra Biosciences, LLC, Concentra Merger Sub V, Inc. and IGM Biosciences, Inc. (incorporated herein by reference to Exhibit 2.1 to the Company’s Current Report on Form 8-K filed on July 1, 2025).
10.1		Form of Contingent Value Rights Agreement by and among Concentra Biosciences, LLC, Concentra Merger Sub V, Inc. and the other parties thereto.
2.2+		Contingent Value Rights Agreement, dated August 14, 2025, by and among Concentra Biosciences, LLC, Concentra Merger Sub V, Inc., Broadridge Corporate Issuer Solutions, LLC and Fortis Advisors LLC (incorporated herein by reference to Exhibit (d)(5) the Schedule TO-T/A filed by Concentra Biosciences, LLC on August 14, 2025).
99.1		Press Release of IGM Biosciences, Inc. dated July 1, 2025.
3.1		Amended and Restated Certificate of Incorporation of IGM Biosciences, Inc.
3.2		Amended and Restated Bylaws of the IGM Biosciences, Inc.
104		Cover Page Interactive Data File (embedded within the Inline XBRL document).

Certain schedules and annexes have been omitted pursuant to Item 601(a)(5) of Regulation S-K. The Company hereby undertakes to furnish supplementally copies of any of the omitted schedules and annexes upon request by the SEC; provided, however, that the Company may request confidential treatment pursuant to Rule 24b-2 of the Exchange Act for any annexes or schedules so furnished.

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

IGM BIOSCIENCES, INC.

Date: July 1, 2025

/s/ Misbah Tahir

Date: August 14, 2025

/s/ Mary Beth Harler, M.D.

Misbah TahirChief Financial Officer

Mary Beth Harler, M.D.Chief Executive Officer

Filing Compare · IGM Biosciences, Inc.