RAPID MICRO BIOSYSTEMS (RPID) director exercises option, adds 842 shares

Rhea-AI Filing Summary

RAPID MICRO BIOSYSTEMS, INC. director Natale S. Ricciardi exercised a stock option and acquired Class A common shares. On February 27, 2026, he exercised an option for 842 shares at an exercise price of $0.75 per share. Following the exercise, his direct holdings of Class A common stock increased to 29,442 shares. The footnote indicates the option was already fully vested and exercisable, meaning this transaction reflects the use of an existing equity award rather than a new grant or open-market purchase.

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^*

RICCIARDI NATALE S

(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
	Officer (give title below)		Other (specify below)

3. Date of Earliest Transaction (Month/Day/Year)
02/27/2026

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	02/27/2026		M		842	A	$0.75	29,442	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
Stock Option (Right to Buy)	$0.75	02/27/2026		M			842	(1)	03/10/2026	Class A Common Stock	842	$0.75	0	D

Explanation of Responses:

1. The option is fully vested and exercisable.

Remarks:

	/s/ Sean M. Wirtjes, Attorney-in-Fact for Natale S. Ricciardi	03/02/2026
	** 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 RPID director Natale Ricciardi report on this Form 4?

Natale Ricciardi reported exercising a stock option and acquiring Class A common stock. He converted an option into 842 shares of RAPID MICRO BIOSYSTEMS, INC. common stock at an exercise price of $0.75 per share on February 27, 2026.

How many RPID shares did Natale Ricciardi acquire through the option exercise?

He acquired 842 shares of Class A common stock through the option exercise. The transaction reflects a derivative exercise/conversion rather than an open-market purchase, at an exercise price of $0.75 per share as disclosed in the Form 4 details.

What is Natale Ricciardi’s RPID share ownership after this Form 4 transaction?

After the transaction, Ricciardi directly holds 29,442 shares of RAPID MICRO BIOSYSTEMS, INC. Class A common stock. This total reflects the addition of 842 shares obtained by exercising a fully vested and exercisable stock option on February 27, 2026.

Was the RPID stock option exercised by Natale Ricciardi already vested?

Yes. A footnote states that the option is fully vested and exercisable. This means the Form 4 transaction records Ricciardi using an existing, fully earned equity award rather than receiving a new grant or conditional right to purchase additional RPID shares.

Did the RPID Form 4 report any stock sales by Natale Ricciardi?

No sales were reported in this Form 4. Both transactions are coded as M for an exercise or conversion of a derivative security, indicating an option exercise that increased his holdings, without any corresponding sale of RAPID MICRO BIOSYSTEMS, INC. shares.