SECURITIESFORM AND EXCHANGE COMMISSION8-K

☐Item Pre-commencement communications pursuant to Rule 14d-2(b).02 underResults theof ExchangeOperations Actand (17Financial CFR 240Condition.14d-2(b))

Item 9.01 Financial Statements and Exhibits.

UNITED ~~STATES~~STATESSECURITIES AND EXCHANGE COMMISSIONWASHINGTON, D.C. 20549

~~WASHINGTON,~~CURRENT ~~D.C. 20549~~REPORT

~~FORM~~Pursuant ~~8-K~~to Section 13 or 15(d) of the Securities Exchange Act of 1934

~~CURRENT~~Date ~~REPORT~~of Report (Date of earliest event reported): October 28, 2025

~~Pursuant~~REPLIGEN ~~to Section 13 or 15(d)~~CORPORATION

(Exact name of ~~the~~Registrant ~~Securities~~as ~~Exchange~~Specified ~~Act~~in ofIts ~~1934~~Charter)

Date of Report (Date of earliest event reported): September 1, 2025


Delaware	000-14656	04-2729386
(State or Other Jurisdiction of Incorporation)	(Commission File Number)	(IRS Employer Identification No.)

41 Seyon Street
Waltham, Massachusetts		02453
(Address of Principal Executive Offices)		(Zip Code)

Registrant’s ~~REPLIGEN~~Telephone ~~CORPORATION~~Number, Including Area Code: (781) 250-0111

(~~Exact~~Former ~~name~~Name ofor ~~Registrant~~Former asAddress, ~~Specified~~if inChanged ~~Its~~Since ~~Charter~~Last Report)

Delaware		000-14656		04-2729386
(State or Other Jurisdictionof Incorporation)		(Commission File Number)		(IRS EmployerIdentification No.)

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:

41 Seyon Street
Waltham, Massachusetts		02453
(Address of Principal Executive Offices)		(Zip Code)


☐	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))

~~Registrant’s~~Securities ~~Telephone~~registered ~~Number,~~pursuant ~~Including~~to ~~Area~~Section ~~Code:~~ 12(~~781~~b) ~~250-0111~~of the Act:

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


Title of each class	Trading Symbol(s)	Name of each exchange on which registered
Common Stock, par value $0.01 per share	RGEN	Nasdaq Global Select Market

~~Check~~Indicate by check mark whether the ~~appropriate~~registrant ~~box~~is ~~below~~an ifemerging growth company as defined in Rule 405 of the ~~Form~~Securities ~~8-K~~Act ~~filing~~of is1933 ~~intended~~(§230.405 toof ~~simultaneously~~this ~~satisfy~~chapter) ~~the~~or ~~filing~~Rule ~~obligation~~12b-2 of the ~~registrant~~Securities ~~under~~Exchange ~~any~~Act of ~~the~~1934 ~~following~~(§240.12b-2 ~~provisions:~~of this chapter).

☐Emerging ~~Written~~growth ~~communications~~company ~~pursuant to Rule 425 under the Securities Act (17 CFR 230.425)~~☐

☐If ~~Soliciting~~an ~~material~~emerging ~~pursuant~~growth tocompany, ~~Rule~~indicate ~~14a-12~~by ~~under~~check mark if the ~~Exchange~~registrant ~~Act~~has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(17a) ~~CFR~~of ~~240~~the Exchange Act.~~14a-12)~~ ☐

☐On ~~Pre-commencement~~October ~~communications~~28, ~~pursuant~~2025, toRepligen ~~Rule~~Corporation ~~13e-4(c)~~announced ~~under~~its financial results for the ~~Exchange~~third ~~Act~~quarter ~~(17~~ended ~~CFR~~September ~~240~~30, 2025.~~13e~~ The full text of the press release issued in connection with the announcement is attached as Exhibit 99.1 to this Current Report on Form 8-~~4(c))~~K.

~~Securities~~The ~~registered~~information ~~pursuant~~in tothis Form 8-K and the exhibit attached hereto shall not be deemed “filed” for purposes of Section 12 18 of the Securities Exchange Act of 1934, as amended (bthe “Exchange Act”), or otherwise subject to the liabilities of that section, nor shall it be deemed incorporated by reference in any filing under the Securities Act: of 1933, as amended, or the Exchange Act, except as expressly set forth by specific reference in such a filing.

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

REPLIGEN CORPORATION

Date: September 2, 2025

/s/ Olivier Loeillot

Olivier Loeillot

President and Chief Executive Officer

~~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~~d) ~~or Rule 12b-2 of the Securities Exchange Act of 1934 (§240.12b-2 of this chapter).~~Exhibits

Emerging growth company ☐



99.1		Press Release by Repligen Corporation, dated October 28, 2025
104		Cover page from this Current Report on Form 8-K, formatted in Inline XBRL

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. ☐SIGNATURES

~~Item 5.02~~Pursuant ~~Departure~~to ofthe ~~Directors~~requirements orof ~~Certain~~the ~~Officers;~~Securities ~~Election~~Exchange Act of ~~Directors;~~1934, ~~Appointment~~the ofregistrant ~~Certain~~has ~~Officers;~~duly ~~Compensatory~~caused ~~Arrangements~~this ofreport ~~Certain~~to ~~Officers.~~be signed on its behalf by the undersigned hereunto duly authorized.

On September 2, 2025, Repligen Corporation (the “Company”) announced that it was appointing Violetta Hughes as the Company’s Chief Accounting Officer, effective September 1, 2025 (the “Effective Date”), in an effort to build a more robust infrastructure at the Company for financial reporting and oversight of matters related to the Sarbanes–Oxley Act. In this role, Ms. Hughes will become the Company’s principal accounting officer, replacing Jason K. Garland, who will continue to serve as the Company’s Chief Financial Officer with more of his time dedicated to corporate strategy, financial planning and analysis, capital markets, and driving growth.


		REPLIGEN CORPORATION

Date:	October 28, 2025	By:	/s/ Olivier Loeillot
			Olivier Loeillot
			President and Chief Executive Officer

Ms. Hughes, age 53, is a seasoned finance executive with deep expertise in financial controllership, operational finance, and global team leadership across diverse industries including life sciences, medical technology and pharmaceuticals. Ms. Hughes brings over 25 years of experience and a disciplined approach to financial governance with a strong track record of leading through change, including driving improvements in financial transparency, implementing SOX compliance frameworks, and partnering with business leaders to support strategic decision-making. Prior to joining the Company, from January 2023 to August 2025, Ms. Hughes served as VP and Chief Accounting Officer at Azenta, Inc. (NASDAQ: AZTA), a leading provider of life sciences solutions worldwide, where she led enterprise-wide initiatives to modernize financial systems, streamline close processes, and improve SOX compliance. From December 2020 to December 2022, Ms. Hughes served as SVP and Chief Accounting Officer at Akebia Therapeutics, Inc. (NASDAQ: AKBA), a fully-integrated biopharmaceutical company focusing on kidney diseases. Prior to AKBA, from December 2016 to November 2020, Ms. Hughes served as SVP of Accounting, Corporate Controller at AMAG Pharmaceuticals, Inc. (NASDAQ: AMAG), which was a publicly-traded pharmaceutical company developing products treating iron deficiency anemia in adults, until its acquisition by Covis Pharma in November 2020.

Ms. Hughes holds a B.S. in Accounting from the University of Massachusetts Lowell.

In connection with Ms. Hughes’ appointment, the Compensation Committee of the Board (the “Compensation Committee”) approved an annual base salary of $395,000, effective as of the Effective Date, and a one-time signing bonus of $150,000. Ms. Hughes will also be eligible for a target annual performance bonus of up to 50% of her base salary. In addition, Ms. Hughes’ offer letter provides for an annual equity award worth an aggregate amount of $750,000, $500,000 of which will be granted in the form of restricted stock units and $250,000 of which will be granted in the form of options to purchase the Company’s common stock, subject to the approval of the Compensation Committee and effective as of the Effective Date, which will vest in equal annual installments on each of the first, second, third, fourth and fifth anniversaries of the Effective Date, subject to Ms. Hughes’ continued employment with the Company through the applicable vesting date, and that she will be eligible to participate in all customary employee benefit plans or programs generally available to the Company’s full-time employees.

There are no arrangements or understandings between Ms. Hughes and any other person pursuant to which she was selected as an officer, no family relationships between Ms. Hughes and any other executive officer or director of the Company, and no related party transactions within the meaning of Item 404(a) of Regulation S-K between Ms. Hughes and the Company.

Item 9.01 Financial Statements and Exhibits.

(d) Exhibits

104 Cover page from this Current Report on Form 8-K, formatted in Inline XBRL

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.

Filing Compare · REPLIGEN CORP