STOCK TITAN

RPID (RAPID MICRO BIOSYSTEMS) CFO acquires shares and Series A/B warrants in direct offering

Filing Impact
(Neutral)
Filing Sentiment
(Neutral)
Form Type
4

Rhea-AI Filing Summary

RAPID MICRO BIOSYSTEMS, INC. Chief Financial Officer Sean M. Wirtjes acquired 12,787 shares of Class A Common Stock in a registered direct offering at $1.955 per share, together with accompanying Series A and Series B warrants for 12,787 shares each.

The Series A Warrant has a $1.955 exercise price and expires on May 29, 2027, while the Series B Warrant has a $2.340 exercise price and expires on May 29, 2031. After these awards, he directly holds 568,981 shares of Class A Common Stock and 12,787 Series A and 12,787 Series B warrants. Both warrant series are subject to a 4.99% beneficial ownership cap on exercise.

Positive

  • None.

Negative

  • None.
Insider WIRTJES SEAN M
Role CHIEF FINANCIAL OFFICER
Type Security Shares Price Value
Grant/Award Series A Warrant (right to buy) 12,787 $0.00 --
Grant/Award Series B Warrant (right to buy) 12,787 $0.00 --
Grant/Award Class A Common Stock 12,787 $1.955 $25K
Holdings After Transaction: Series A Warrant (right to buy) — 12,787 shares (Direct, null); Series B Warrant (right to buy) — 12,787 shares (Direct, null); Class A Common Stock — 568,981 shares (Direct, null)
Footnotes (1)
  1. On May 29, 2026, the Reporting Person purchased, in a registered direct offering, 12,787 shares of the Issuer's Class A Common Stock, as well as an accompanying Series A Warrant to purchase 12,787 shares of the Issuer's Class A Common Stock (or pre-funded warrants in lieu thereof) and an accompanying Series B Warrant to purchase 12,787 shares of the Issuer's Class A Common Stock (or pre-funded warrants in lieu thereof). The purchase price of each share of Issuer Class A Common Stock and accompanying Series A and Series B Warrant was $1.955. The issuance of such securities was approved by the Issuer's compensation committee of the board of directors in accordance with Rule 16(b)-3 of the Securities Exchange Act of 1934, as amended. The Series A and Series B Warrants 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 4.99% of the total number of shares of the Issuer's Class A Common Stock then outstanding immediately following such exercise.
Common shares acquired 12,787 shares Class A Common Stock purchased in registered direct offering
Purchase price per share $1.955 per share Price for each share plus accompanying Series A and Series B Warrant
Shares held after transaction 568,981 shares Total Class A Common Stock directly owned after acquisition
Series A Warrant size 12,787 warrants Each exercisable into one share of Class A Common Stock
Series A Warrant exercise price $1.955 per share Exercise price for Series A Warrant into Class A Common Stock
Series B Warrant exercise price $2.340 per share Exercise price for Series B Warrant into Class A Common Stock
Beneficial ownership cap 4.99% Maximum beneficial ownership allowed after warrant exercise
Series B Warrant expiration May 29, 2031 Final expiration date of the Series B Warrant
registered direct offering financial
"purchased, in a registered direct offering, 12,787 shares of the Issuer's Class A Common Stock"
A registered direct offering is a way for a company to sell new shares of its stock directly to select investors with regulatory approval. This method allows the company to raise funds quickly and efficiently without needing a public auction, similar to offering exclusive access to a limited number of buyers. For investors, it often provides an opportunity to purchase shares at a favorable price, while giving the company immediate access to capital.
Series A Warrant financial
"an accompanying Series A Warrant to purchase 12,787 shares of the Issuer's Class A Common Stock"
A Series A warrant is a contract issued alongside a company’s early funding round that gives the holder the right to buy a set number of shares later at a fixed price. Think of it like a coupon that lets an investor purchase stock at today’s agreed price even if the company’s value rises; it can boost potential upside for the warrant holder and create dilution for existing shareholders, so investors watch them when assessing ownership and future share value.
Series B Warrant financial
"an accompanying Series B Warrant to purchase 12,787 shares of the Issuer's Class A Common Stock"
A Series B warrant is a tradable right issued alongside a Series B funding round that lets its holder buy a specified number of company shares at a fixed price for a set period. It matters to investors because exercising the warrant increases the total shares outstanding (dilution) and can be a cheap way to gain ownership if the company’s value rises — think of it like a coupon to buy stock later at today’s price.
Rule 16(b)-3 regulatory
"approved by the Issuer's compensation committee of the board of directors in accordance with Rule 16(b)-3"
Section 13(d) regulatory
"beneficial ownership would be aggregated for purposes of Section 13(d) of the Act"
beneficially own financial
"would beneficially own more than 4.99% of the total number of shares"
Beneficially own means having the economic rights and risks of a security—such as the right to receive dividends, sell the shares, or profit from price changes—whether or not your name appears on the official share register. Think of it like renting a car: you use it and reap the benefits even if the title lists someone else. Investors care because beneficial ownership determines who truly controls value, must be disclosed under securities rules, and can signal potential influence or trading activity that affects a stock’s price.
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SEC Form 4
FORM 4UNITED 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*
WIRTJES SEAN M

(Last)(First)(Middle)
C/O RAPID MICRO BIOSYSTEMS, INC.
25 HARTWELL AVENUE

(Street)
LEXINGTON MASSACHUSETTS 02421

(City)(State)(Zip)

UNITED STATES

(Country)
2. Issuer Name and Ticker or Trading Symbol
RAPID MICRO BIOSYSTEMS, INC. [ RPID ]
5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)
Director10% Owner
XOfficer (give title below)Other (specify below)
CHIEF FINANCIAL OFFICER
2a. Foreign Trading Symbol
3. Date of Earliest Transaction (Month/Day/Year)
05/29/2026
6. Individual or Joint/Group Filing (Check Applicable Line)
XForm filed by One Reporting Person
Form filed by More than One Reporting Person
4. If Amendment, Date of Original Filed (Month/Day/Year)

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)
CodeVAmount(A) or (D)Price
Class A Common Stock05/29/2026A(1)12,787A$1.955568,981D
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)
CodeV(A)(D)Date ExercisableExpiration DateTitleAmount or Number of Shares
Series A Warrant (right to buy)$1.95505/29/2026A(1)12,78711/29/2026(2)05/29/2027Class A Common Stock12,787$0(1)12,787D
Series B Warrant (right to buy)$2.3405/29/2026A(1)12,78711/29/2026(2)05/29/2031Class A Common Stock12,787$0(1)12,787D
Explanation of Responses:
1. On May 29, 2026, the Reporting Person purchased, in a registered direct offering, 12,787 shares of the Issuer's Class A Common Stock, as well as an accompanying Series A Warrant to purchase 12,787 shares of the Issuer's Class A Common Stock (or pre-funded warrants in lieu thereof) and an accompanying Series B Warrant to purchase 12,787 shares of the Issuer's Class A Common Stock (or pre-funded warrants in lieu thereof). The purchase price of each share of Issuer Class A Common Stock and accompanying Series A and Series B Warrant was $1.955. The issuance of such securities was approved by the Issuer's compensation committee of the board of directors in accordance with Rule 16(b)-3 of the Securities Exchange Act of 1934, as amended.
2. The Series A and Series B Warrants 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 4.99% of the total number of shares of the Issuer's Class A Common Stock then outstanding immediately following such exercise.
Remarks:
/s/ Sean M. Wirtjes06/02/2026
** Signature of Reporting PersonDate
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.
* Form 4: SEC 1474 (03-26)

FAQ

What did RPID CFO Sean M. Wirtjes acquire in this Form 4 filing?

Sean M. Wirtjes acquired 12,787 shares of Class A Common Stock and accompanying Series A and Series B warrants. Each warrant series covers 12,787 underlying shares as part of a registered direct offering at a combined purchase price of $1.955 per share.

What was the purchase price for the RPID shares and warrants reported?

The combined purchase price was $1.955 for each share of Class A Common Stock with its accompanying Series A and Series B warrant. This price applied to 12,787 shares purchased in a registered direct offering approved by the issuer’s compensation committee under Rule 16(b)-3.

What are the key terms of the RPID Series A Warrant received by the CFO?

The Series A Warrant covers 12,787 shares of Class A Common Stock at a $1.955 exercise price. It becomes exercisable on November 29, 2026 and expires on May 29, 2027, subject to a 4.99% beneficial ownership limitation on post-exercise holdings.

What are the key terms of the RPID Series B Warrant reported in this filing?

The Series B Warrant covers 12,787 shares of Class A Common Stock at a $2.340 exercise price. It becomes exercisable on November 29, 2026 and expires on May 29, 2031, and is also subject to the 4.99% beneficial ownership limitation on exercise.

How many RPID shares does the CFO hold after these transactions?

Following the transactions, Sean M. Wirtjes directly holds 568,981 shares of Class A Common Stock. He also holds 12,787 Series A Warrants and 12,787 Series B Warrants, each exercisable into an equal number of Class A Common Stock shares, subject to ownership limits.

What is the 4.99% beneficial ownership limitation mentioned for RPID warrants?

The Series A and Series B Warrants cannot be exercised if doing so would cause the holder and affiliates to beneficially own more than 4.99% of outstanding Class A Common Stock immediately after exercise. This cap limits how many shares can be issued through warrant exercises.

How was the issuance of RPID securities to the CFO approved?

The issuance of the Class A Common Stock and accompanying Series A and Series B Warrants was approved by the issuer’s compensation committee. The approval was made in accordance with Rule 16(b)-3 under the Securities Exchange Act of 1934, as disclosed in the footnotes.