[SCHEDULE 13D] Rapid Micro Biosystems, Inc. SEC Filing

Rhea-AI Filing Summary

Robert G. Spignesi Jr., President and CEO of Rapid Micro Biosystems (RPID), reports beneficial ownership of 2,647,256 shares of Class A common stock, representing approximately 6.3% of the outstanding Class A shares. This total includes 493,931 shares held directly, 10 shares issuable upon exercise of warrants within 60 days, and 2,153,315 shares issuable upon exercise of options exercisable within 60 days. He also holds 731,871 restricted stock units subject to vesting and options to purchase 2,619,434 shares at exercise prices between $0.75 and $10.85. The filing discloses recent vesting-related acquisitions of 125,722 shares and open-market sales of 57,443 shares to satisfy tax withholding.

Positive

• Meaningful insider ownership: Reporting Person beneficially owns approximately 6.3% of Class A shares, aligning executive and shareholder interests.
• Transparent disclosure of equity awards: Filing details RSUs and options and provides exercise price ranges, improving clarity on potential dilution.

Negative

• Potential dilution: Large outstanding equity awards (options to purchase 2,619,434 shares and 731,871 RSUs) could dilute current shareholders if exercised or vested.
• Vesting-related sales: The CEO sold 57,443 shares between July 8–14, 2025 to satisfy tax withholding, reducing his direct holdings.

Insights

Corporate Governance Expert

TL;DR: CEO ownership of 6.3% aligns management and shareholder interests but substantial outstanding option grants could dilute holders.

Spignesi's reported stake and his role as President and CEO give him meaningful alignment with shareholders and potential influence on corporate actions. The filing details large equity incentive programs: 731,871 RSUs (time- and performance-based) and options for 2,619,434 shares, which, if exercised or vested, could materially increase share count. The filing properly discloses vested share settlements and tax-sale activity. Investors should note the degree of equity compensation as a governance and dilution consideration.

Securities Analyst

TL;DR: Beneficial ownership disclosure clarifies insider position and recent transactions; option/warrant exercisability increases reported ownership to 6.3%.

The filer reports 2,647,256 shares beneficially owned, calculated by including 2,163,315 exercisable options/warrants per SEC rules, based on 39,710,799 outstanding Class A shares. The statement also lists historic purchase cost for 493,931 directly held shares and specific open-market sale prices tied to RSU tax withholding. The combination of exercised/vested shares and exercisable options means near-term dilution and ownership metrics reflect more than just currently outstanding shares.

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13D

Under the Securities Exchange Act of 1934

RAPID MICRO BIOSYSTEMS, INC.

(Name of Issuer)

Class A Common Stock, $0.01 par value per share

(Title of Class of Securities)

75340L104

(CUSIP Number)

Robert G. Spignesi, Jr.
Rapid Micro Biosystems, Inc., 25 Hartwell Avenue
Lexington, MA, 02421
978-349-3200

(Name, Address and Telephone Number of Person Authorized to Receive Notices and Communications)

03/28/2024

(Date of Event Which Requires Filing of This Statement)

If the filing person has previously filed a statement on Schedule 13G to report the acquisition that is the subject of this Schedule 13D, and is filing this schedule because of §§ 240.13d-1(e), 240.13d-1(f) or 240.13d-1(g), check the following box.

The information required on the remainder of this cover page shall not be deemed to be "filed" for the purpose of Section 18 of the Securities Exchange Act of 1934 ("Act") or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act (however, see the Notes).

SCHEDULE 13D

CUSIP No. 75340L104

1

Name of reporting person

SPIGNESI ROBERT G JR

2

Check the appropriate box if a member of a Group (See Instructions)

(a)
(b)

3

SEC use only

4

Source of funds (See Instructions)

PF

5

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

6

Citizenship or place of organization

UNITED STATES

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 2,647,256.00
8	Shared Voting Power 0.00
9	Sole Dispositive Power 2,647,256.00
10	Shared Dispositive Power 0.00

11

Aggregate amount beneficially owned by each reporting person

2,647,256.00

12

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

13

Percent of class represented by amount in Row (11)

6.3 %

14

Type of Reporting Person (See Instructions)

OO

SCHEDULE 13D

Item 1.	Security and Issuer
(a)	Title of Class of Securities: Class A Common Stock, $0.01 par value per share
(b)	Name of Issuer: RAPID MICRO BIOSYSTEMS, INC.
(c)	Address of Issuer's Principal Executive Offices: 25 Hartwell Avenue, Lexington, MASSACHUSETTS , 02421.
Item 2.	Identity and Background
(a)	This Schedule 13D is being filed by Robert G. Spignesi Jr. (the "Reporting Person").
(b)	The principal business address of the Reporting Person is 25 Hartwell Avenue, Lexington, MA 02421.
(c)	The Reporting Person is President and Chief Executive Officer and a member of the Board of Directors of the Issuer.
(d)	During the last five years, the Reporting Person has not been convicted in a criminal proceeding (excluding traffic violations or similar misdemeanors).
(e)	During the last five years, the Reporting Person has not been party to a civil proceeding of a judicial or administrative body of competent jurisdiction and as a result of such proceeding was or is subject to a judgment, decree or final order enjoining future violations of, or prohibiting or mandating activities subject to, federal or state securities laws or finding any violation with respect to such laws.
(f)	The Reporting Person is a citizen of the United States.
Item 3.	Source and Amount of Funds or Other Consideration
	The information set forth or incorporated by reference in Item 6 of this Statement is incorporated by reference into this Item 3. The 493,931 shares of Class A Common Stock held directly by the Reporting Person were purchased for an aggregate of $346,555 (excluding commissions and other execution-related costs) using personal funds.
Item 4.	Purpose of Transaction
	The information set forth or incorporated by reference in Items 3 and 6 of this Statement is incorporated by reference into this Item 4. The Reporting Person intends to continuously review his investment in the Issuer and may in the future determine (1) to acquire additional securities of the Issuer, through open market purchases, private agreements or otherwise, (2) to dispose of all or a portion of the securities of the Issuer owned by him or (3) to take any other available course of action. Notwithstanding anything contained herein, the Reporting Person specifically reserves the right to change his intention with respect to any or all of such matters. In reaching any decision as to his course of action (as well as to the specific elements thereof), the Reporting Person currently expects that he would take into consideration a variety of factors, including, but not limited to, the following: the Issuer's business and prospects; other developments concerning the Issuer and its business generally; other business opportunities available to the Reporting Person; developments with respect to the business of the Reporting Person; changes in law and government regulations; general economic conditions; and money and stock market conditions, including the market price of the securities of the Issuer. The Reporting Person is President and Chief Executive Officer and a member of the Board of Directors of the Issuer and, accordingly, in such capacity, may have influence over the corporate activities of the Issuer, including activities which may relate to items described in subparagraphs (a) through (j) of Item 4 of Schedule 13D. Subject to the Issuer's Insider Trading Policy, the Reporting Person may from time to time buy or sell securities of the Issuer as appropriate for his personal circumstances.
Item 5.	Interest in Securities of the Issuer
(a)	The information set forth in rows 7 through 13 of the cover page to this Schedule 13D is incorporated by reference. The Reporting Person beneficially owns an aggregate of 2,647,256 shares of Class A Common Stock, which consists of (i) 493,931 shares of Class A Common Stock held directly by the Reporting Person, (ii) 10 shares of Class A Common Stock issuable to the Reporting Person upon exercise of warrants exercisable within 60 days of this Statement and (iii) 2,153,315 shares of Class A Common Stock issuable to the Reporting Person upon exercise of stock options exercisable within 60 days of this Statement. The foregoing excludes 1,197,990 shares of Class A Common Stock underlying equity awards that are currently unvested and are not substantially certain to vest within 60 days of this statement.
(b)	The 2,647,256 shares of Class A Common Stock beneficially owned by the Reporting Person represents approximately 6.3% of the outstanding shares of Class A Common Stock. The percent of class was calculated based on (i) 39,710,799 shares of Class A Common Stock outstanding, as reported by the Issuer to the Reporting Person, plus (ii) 2,163,315 shares of Class A Common Stock underlying stock options and/or warrants held by the Reporting Person that are exercisable within 60 days, which are deemed outstanding pursuant to SEC Rule 13-3(d)(1)(i).
(c)	Between July 8, 2025 and July 14, 2025, the Reporting Person acquired an aggregate of 125,722 shares of Class A Common Stock upon satisfaction of performance criteria underlying previously granted restricted stock units ("RSUs") subject to performance-based vesting conditions. In connection with tax withholding obligations relating to the vesting and settlement of such RSUs, the Reporting Person sold an aggregate of 57,443 shares of Class A Common Stock as follows: (i) 10,824 shares sold on July 8, 2025 at a price per share of $3.5127; (ii) 11,247 shares sold on July 9, 2025 at a price per share $3.5103; (iii) 11,617 shares sold on July 10, 2025 at a price per share of $3.398; (iv) 11,874 shares sold on July 11, 2025 at a price per share of $3.3265; and (v) 11,881 shares sold on July 14, 2025 at a price per share of $3.323. The sales were effected on the open-market through broker-assisted transactions. In addition, during the 60 days preceding this statement, the Reporting Person acquired beneficial ownership of 38,757 shares of Class A Common Stock underlying equity awards subject to vesting, as further described in Item 6 below. Except as otherwise described in this Item 5(c), the Reporting Person has not effected any transactions in the Issuer's Class A Common Stock during the past 60 days.
(d)	Not applicable.
(e)	Not applicable.
Item 6.	Contracts, Arrangements, Understandings or Relationships With Respect to Securities of the Issuer
	The information contained in Item 3 is incorporated herein by reference. The Reporting Person is and will be entitled to receive compensation and other benefits as President and Chief Executive Officer of the Issuer. In such capacity, he may also be granted equity awards with respect to the Issuer's Class A Common Stock from time to time. The Reporting Person currently holds (i) 731,871 RSUs subject to time-based and performance-based vesting, each representing the contingent right to receive one share of Class A Common Stock, and (ii) stock options to purchase an aggregate of 2,619,434 shares of Class A Common Stock at exercise prices ranging between $0.75 and $10.85 per share. The equity plans under which such awards have been granted and the form of award agreements representing such equity awards are filed as Exhibits 99.1 and 99.2 hereto, and are incorporated by reference into this Item 6 in their entirety.
Item 7.	Material to be Filed as Exhibits.
	Exhibit 99.1 Rapid Micro Biosystems, Inc. 2010 Stock Option and Grant Plan and forms of award agreements thereunder (Incorporated by reference to Exhibit 10.1 to the Issuer's Registration Statement on Form S-1 (Reg. No. 333-257431) filed on June 25, 2021). Exhibit 99.2 Rapid Micro Biosystems, Inc 2021 Incentive Award Plan and forms of award agreements thereunder (incorporated by reference to Exhibit 10.2 to Amendment No. 1 to the Issuer's Registration Statement on Form S-1 (Reg. No. 333-257431) filed on July 12, 2021).

SIGNATURE

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

SPIGNESI ROBERT G JR

Signature:	/s/ Robert G. Spignesi, Jr.
Name/Title:	Robert G. Spignesi, Jr.
Date:	08/19/2025

FAQ

How many Rapid Micro Biosystems (RPID) Class A shares does the CEO own?

The filing reports the CEO beneficially owns 2,647,256 Class A shares, representing about 6.3% of outstanding Class A stock.

What equity awards does Robert G. Spignesi Jr. hold in RPID?

He holds 731,871 restricted stock units subject to vesting and stock options to purchase 2,619,434 shares with exercise prices between $0.75 and $10.85.

Did the CEO sell any RPID shares recently?

Yes. To cover tax withholding from RSU settlements, he sold 57,443 shares on July 8–14, 2025 at prices between $3.323 and $3.5127 per share.

How was the 6.3% ownership percentage calculated?

The percentage is based on 39,710,799 outstanding Class A shares plus 2,163,315 options/warrants exercisable within 60 days, per SEC rules.

Does the filing indicate any legal or criminal issues for the reporting person?

No. The reporting person states he has not been convicted of a crime nor subject to disqualifying civil judgments in the past five years.