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SEC Form 4

FORM 4		UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934 or Section 30(h) of the Investment Company Act of 1940	OMB APPROVAL OMB Number: 3235-0287 Estimated average burden hours per response: 0.5
	Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).
	Check this box to indicate that a transaction was made pursuant to a contract, instruction or written plan for the purchase or sale of equity securities of the issuer that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c). See Instruction 10.

1. Name and Address of Reporting Person* Bain Capital Life Sciences Investors, LLC (Last) (First) (Middle) 200 CLARENDON STREET (Street) BOSTON MA 02116 (City) (State) (Zip)	2. Issuer Name and Ticker or Trading Symbol RAPID MICRO BIOSYSTEMS, INC. [ RPID ]	5. Relationship of Reporting Person(s) to Issuer (Check all applicable) Director X 10% Owner Officer (give title below) Other (specify below)
	3. Date of Earliest Transaction (Month/Day/Year) 05/20/2026
	4. If Amendment, Date of Original Filed (Month/Day/Year)	6. Individual or Joint/Group Filing (Check Applicable Line) Form filed by One Reporting Person X Form filed by More than One Reporting Person

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1. Title of Security (Instr. 3)	2. Transaction Date (Month/Day/Year)	2A. Deemed Execution Date, if any (Month/Day/Year)	3. Transaction Code (Instr. 8)		4. Securities Acquired (A) or Disposed Of (D) (Instr. 3, 4 and 5)			5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4)	6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	7. Nature of Indirect Beneficial Ownership (Instr. 4)
			Code	V	Amount	(A) or (D)	Price
Class A Common Stock								8,434,560	I	See footnotes(4)(5)(6)

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security (Instr. 3)	2. Conversion or Exercise Price of Derivative Security	3. Transaction Date (Month/Day/Year)	3A. Deemed Execution Date, if any (Month/Day/Year)	4. Transaction Code (Instr. 8)		5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5)		6. Date Exercisable and Expiration Date (Month/Day/Year)		7. Title and Amount of Securities Underlying Derivative Security (Instr. 3 and 4)		8. Price of Derivative Security (Instr. 5)	9. Number of derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4)	10. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	11. Nature of Indirect Beneficial Ownership (Instr. 4)
				Code	V	(A)	(D)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares
Pre-Funded Warrant (right to buy)	$0.01	05/20/2026		P(1)		1,463,000		05/20/2026(2)	(3)	Class A Common Stock	1,463,000(2)	(1)	1,463,000	I	See footnotes(1)(6)
Series A Warrant (right to buy)	$1.955	05/20/2026		P(1)		1,463,000		11/20/2026(2)	05/20/2027	Class A Common Stock	1,463,000(2)	(1)	1,463,000	I	See footnotes(1)(6)
Series B Warrant (right to buy)	$2.34	05/20/2026		P(1)		1,463,000		11/20/2026(2)	05/20/2031	Class A Common Stock	1,463,000(2)	(1)	1,463,000	I	See footnotes(1)(6)

1. Name and Address of Reporting Person* Bain Capital Life Sciences Investors, LLC (Last) (First) (Middle) 200 CLARENDON STREET (Street) BOSTON MA 02116 (City) (State) (Zip) Relationship of Reporting Person(s) to Issuer Director X 10% Owner Officer (give title below) Other (specify below)

1. Name and Address of Reporting Person* Bain Capital Life Sciences Partners, LP (Last) (First) (Middle) 200 CLARENDON STREET (Street) BOSTON MA 02116 (City) (State) (Zip) Relationship of Reporting Person(s) to Issuer Director X 10% Owner Officer (give title below) Other (specify below)

1. Name and Address of Reporting Person* Bain Capital Life Sciences Fund, L.P. (Last) (First) (Middle) 200 CLARENDON STREET (Street) BOSTON MA 02116 (City) (State) (Zip) Relationship of Reporting Person(s) to Issuer Director X 10% Owner Officer (give title below) Other (specify below)

1. Name and Address of Reporting Person* BCIP Life Sciences Associates, LP (Last) (First) (Middle) 200 CLARENDON STREET (Street) BOSTON MA 02116 (City) (State) (Zip) Relationship of Reporting Person(s) to Issuer Director X 10% Owner Officer (give title below) Other (specify below)

Explanation of Responses:

1. On May 20, 2026, BCLS I Investco, LP ("BCLS I Investco") purchased, in an underwritten public offering, a Pre-Funded Warrant to purchase 1,463,000 shares of the Issuer's Class A Common Stock, as well as an accompanying Series A Warrant to purchase 1,463,000 shares of the Issuer's Class A Common Stock (or pre-funded warrants in lieu thereof) and an accompanying Series B Warrant to purchase 1,463,000 shares of the Issuer's Class A Common Stock (or pre-funded warrants in lieu thereof). The purchase price of each pre-funded warrant and accompanying Series A Warrant and Series B Warrant was $1.945.

2. The Pre-Funded Warrant, Series A Warrant and Series B Warrant cannot be exercised for shares of the Issuer's Class A Common Stock if, as a result of such exercise, the holder, together with its affiliates and any other persons whose beneficial ownership would be aggregated for purposes of Section 13(d) of the Act, would beneficially own more than 9.99% of the total number of shares of the Issuer's Class A Common Stock then outstanding immediately following such exercise.

3. The Pre-Funded Warrant does not expire.

4. Represents 7,651,369 shares of the Issuer's Class A Common Stock held directly by Bain Capital Life Sciences Fund, L.P. ("BCLS Fund I") and 783,191 shares of the Issuer's Class A Common Stock held directly by BCIP Life Sciences Associates, LP ("BCIPLS," and together with BCLS Fund I and BCLS I Investco, the "Bain Capital Life Sciences Entities").

5. Bain Capital Life Sciences Partners, LP ("BCLSP") is the general partner of BCLS Fund I. As a result, BCLSP may be deemed to share voting and dispositive power with respect to the securities held by BCLS Fund I. BCLSP disclaims beneficial ownership of such securities except to the extent of its pecuniary interest therein.

6. Bain Capital Life Sciences Investors, LLC ("BCLSI") is the general partner of each of BCLSP and BCLS I Investco and governs the investment strategy and decision-making process with respect to investments held by BCIPLS. As a result, BCLSI may be deemed to share voting and dispositive power with respect to the securities held by the Bain Capital Life Sciences Entities. BCLSI disclaims beneficial ownership of such securities except to the extent of its pecuniary interest therein.

	See signatures included in Exhibit 99.1	05/22/2026
	** Signature of Reporting Person	Date
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