Rapid Micro (NASDAQ: RPID) CEO sells shares to cover tax obligations

Rhea-AI Filing Summary

RAPID MICRO BIOSYSTEMS, INC. president and CEO Robert G. Spignesi Jr. reported an automatic sale of 17,922 shares of Class A common stock at $4.1115 per share on March 10, 2026.

The footnote explains this sale was made solely to cover tax obligations related to the vesting of restricted stock units. After the transaction, he directly owned 1,169,848 shares, indicating this was a small, routine disposition relative to his overall stake.

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

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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^*

Spignesi Robert G. Jr.

(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)

X	Director		10% Owner
X	Officer (give title below)		Other (specify below)
	PRESIDENT AND CEO

3. Date of Earliest Transaction (Month/Day/Year)
03/10/2026

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	03/10/2026		S		17,922(1)	D	$4.1115	1,169,848	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 Robert G. Spignesi, Jr.	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).
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FAQ

What insider transaction did RPID CEO Robert Spignesi report?

Robert G. Spignesi Jr., president and CEO of Rapid Micro Biosystems, reported selling 17,922 shares of Class A common stock. The shares were sold automatically to cover tax obligations triggered by the vesting of restricted stock units, not as a discretionary open-market sale.

At what price were the RPID shares sold by the CEO?

The 17,922 Rapid Micro Biosystems Class A shares were sold at an average price of $4.1115 per share. This transaction was described as an automatic sale to satisfy tax obligations arising from restricted stock unit vesting, rather than a typical open-market trading decision.

How many RPID shares does the CEO hold after this Form 4 transaction?

Following the reported sale, CEO Robert G. Spignesi Jr. directly held 1,169,848 shares of Rapid Micro Biosystems Class A common stock. This indicates the 17,922 shares sold for tax obligations represented a small portion of his overall direct ownership stake in the company.

Was the RPID CEO’s sale a discretionary open-market trade?

The filing footnote states the sale was automatic and intended only to cover tax obligations associated with restricted stock unit vesting. This distinguishes it from a discretionary open-market trade, reducing its informational value about the CEO’s personal view on Rapid Micro Biosystems’ share price.

What does a tax-related stock sale mean for RPID investors?

A tax-related stock sale, like the CEO’s 17,922-share transaction, is usually a mechanical event tied to equity compensation. Because the purpose is to pay taxes on vested awards, it typically carries less signaling value about management’s outlook on Rapid Micro Biosystems’ future performance.