RAPID MICRO BIOSYSTEMS (RPID) COO’s 9,603-share sale tied to RSU tax

Rhea-AI Filing Summary

RAPID MICRO BIOSYSTEMS, INC. chief operating officer John J. Addington reported an automatic sale of 9,603 shares of Class A common stock at an average price of $4.3181 per share. The shares were sold to cover tax obligations arising from the vesting of restricted stock units, according to the footnote.

After this transaction, he directly holds 316,762 shares of Class A common stock, indicating the sale represents a small portion of his overall position and is tied to routine equity-compensation tax withholding rather than discretionary selling.

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^*

Wilson John J. Addington

(Last) (First) (Middle)

C/O RAPID MICRO BIOSYSTEMS, INC.

25 HARTWELL AVENUE

(Street)

LEXINGTON MA 02421

(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		10% Owner
X	Officer (give title below)		Other (specify below)
	CHIEF OPERATING OFFICER

3. Date of Earliest Transaction (Month/Day/Year)
03/11/2026

4. If Amendment, Date of Original Filed (Month/Day/Year)

6. Individual or Joint/Group Filing (Check Applicable Line)

X	Form filed by One Reporting Person
	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	03/11/2026		S		9,603(1)	D	$4.3181	316,762	D

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

Explanation of Responses:

1. Represents the automatic sale of stock to cover the associated tax obligations with the vesting of restricted stock units.

Remarks:

	/s/ Sean M. Wirtjes, Attorney-in-Fact for John J. Addington Wilson	03/12/2026
	** Signature of Reporting Person	Date
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
* If the form is filed by more than one reporting person, see Instruction 4 (b)(v).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.
Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB Number.

FAQ

What insider transaction did RAPID MICRO BIOSYSTEMS (RPID) report for John J. Addington?

RAPID MICRO BIOSYSTEMS reported that COO John J. Addington had 9,603 shares of Class A common stock sold at $4.3181 per share. The transaction reflects stock automatically sold to satisfy tax obligations tied to vesting restricted stock units, not a discretionary open-market sale.

Why were shares sold in the latest RPID Form 4 filing for John J. Addington?

The 9,603 shares were automatically sold to cover associated tax obligations from vesting restricted stock units. This type of transaction is a common administrative step in equity compensation programs, rather than an intentional decision to reduce investment exposure to the company’s stock.

How many RPID shares does John J. Addington hold after the reported Form 4 transaction?

Following the tax-related sale, John J. Addington directly holds 316,762 shares of RPID Class A common stock. This remaining stake shows the sale was a relatively small portion of his total holdings and primarily related to equity-compensation tax withholding mechanics.

Was the RPID insider transaction by John J. Addington an open-market sale?

While coded as an open-market sale, the footnote explains it was an automatic sale to cover tax obligations from vesting restricted stock units. That means the transaction is more administrative in nature, not a discretionary decision to exit or materially reduce his share position.

What does the recent RPID Form 4 imply about John J. Addington’s ownership position?

The filing shows a small number of shares sold for tax purposes and 316,762 shares still held directly. This indicates his overall ownership in RAPID MICRO BIOSYSTEMS remains substantial, with the transaction reflecting routine management of taxes on equity compensation awards.