Rapid Micro Biosystems (RPID) director adds shares plus Series A and B warrants

Rhea-AI Filing Summary

Rapid Micro Biosystems director Inese Lowenstein increased her stake through a combined share purchase and warrant grant. On May 29, 2026, she acquired 12,787 shares of Class A Common Stock at $1.955 per share in a registered direct offering, together with Series A and Series B Warrants to purchase 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 $2.34 exercise price and expires on May 29, 2031. After this transaction, she directly holds 70,687 Class A shares. The warrants are subject to a 4.99% beneficial ownership cap that restricts exercises that would push her above that ownership level.

Insider Trade Summary

3 transactions reported

Mixed 3 txns

Insider LOWENSTEIN INESE

Role null

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 — 70,687 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.

Key Figures

Shares acquired: 12,787 shares Purchase price: $1.955 per share Post-transaction holdings: 70,687 shares +5 more

8 metrics

Shares acquired 12,787 shares Class A Common Stock acquired on May 29, 2026 at $1.955

Purchase price $1.955 per share Price per share for Class A stock plus accompanying warrants

Post-transaction holdings 70,687 shares Total Class A Common Stock directly held after the transaction

Series A Warrant size 12,787 shares Underlying Class A shares for Series A Warrant

Series A exercise price $1.955 per share Exercise price for Series A Warrant

Series A expiration May 29, 2027 Expiration date of Series A Warrant

Series B exercise price $2.34 per share Exercise price for Series B Warrant

Series B expiration May 29, 2031 Expiration date of Series B Warrant

Key Terms

registered direct offering, Series A Warrant, Series B Warrant, Rule 16(b)-3, +2 more

6 terms

registered direct offering financial

"the Reporting Person purchased, in a registered direct offering, 12,787 shares"

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"

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"

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 ... 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 more than 4.99% financial

"would beneficially own more than 4.99% of the total number of shares"

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Form 4 Insider Transactions: What Each Field Means →

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^*

LOWENSTEIN INESE

(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)

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

2a. Foreign Trading Symbol

3. Date of Earliest Transaction (Month/Day/Year)
05/29/2026

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

X	Form 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)
			Code	V	Amount	(A) or (D)	Price
Class A Common Stock	05/29/2026		A(1)		12,787	A	$1.955	70,687	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
Series A Warrant (right to buy)	$1.955	05/29/2026		A(1)		12,787		11/29/2026(2)	05/29/2027	Class A Common Stock	12,787	$0(1)	12,787	D
Series B Warrant (right to buy)	$2.34	05/29/2026		A(1)		12,787		11/29/2026(2)	05/29/2031	Class A Common Stock	12,787	$0(1)	12,787	D

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. Wirtjes, Attorney-in-Fact for Inese Lowenstein	06/02/2026
	** 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.
* Form 4: SEC 1474 (03-26)

FAQ

What did Inese Lowenstein acquire in the latest Form 4 for RPID?

Inese Lowenstein acquired 12,787 shares of Rapid Micro Biosystems Class A stock and matching Series A and Series B Warrants for 12,787 shares each, all tied to a $1.955 per-share purchase in a registered direct offering approved by the compensation committee.

At what price did the RPID director acquire new shares?

The director acquired 12,787 Class A shares at $1.955 per share. This price also covered accompanying Series A and Series B Warrants, each exercisable for 12,787 shares of Class A Common Stock or pre-funded warrants in lieu thereof.

How many Rapid Micro Biosystems shares does the director hold after this transaction?

Following the transaction, Inese Lowenstein directly holds 70,687 shares of Rapid Micro Biosystems Class A Common Stock. This total reflects the newly acquired 12,787 shares in addition to her prior direct holdings disclosed in the Form 4 data.

What are the key terms of the RPID Series A and Series B Warrants?

The Series A Warrant covers 12,787 shares at a $1.955 exercise price and expires May 29, 2027. The Series B Warrant also covers 12,787 shares, with a $2.34 exercise price and a longer expiration date of May 29, 2031.

Is there an ownership cap on exercising the RPID warrants?

Yes. The Series A and Series B Warrants cannot be exercised if doing so would cause the holder and certain related parties to beneficially own more than 4.99% of Rapid Micro Biosystems Class A shares outstanding immediately after the exercise.

How were the RPID share and warrant issuances approved for the director?

The issuances were approved by Rapid Micro Biosystems’ compensation committee of the board of directors. The approval was made in accordance with Rule 16(b)-3 under the Securities Exchange Act of 1934, as described in the Form 4 footnotes.