As of November 6, 2026, 5 holders' latest Schedule 13D or 13G filings report owning 5% or more of Rapid Micro Biosystems, Inc. The largest reported stake is Bain Capital Life Sciences Fund, L.P.'s, at 16.76%. 5 filings are on record since August 19, 2025 (Schedule 13G/A, August 14, 2026).
Sell to companies like Rapid Micro Biosystems, Inc? Enter your website and see 10 with a filed reason to buy from you this month. Free.
Opens in a new tab. No signup.
Key facts
- · Reporting person: Bain Capital Life Sciences Fund, L.P. · Sole voting: 0 · Shared voting: 7,651,369 · Sole dispositive: 0 · Shared dispositive: 7,651,369 · SCHEDULE 13G/A, 2026-08-14
- · Reporting person: Armistice Capital, LLC · Sole voting: 0 · Shared voting: 3,328,000 · Sole dispositive: 0 · Shared dispositive: 3,328,000 · SCHEDULE 13G, 2026-08-14
- · Holder: Longitude Capital Partners II, LLC · Percent: 8.6% · SCHEDULE 13G/A
- · Holder: Endeavour Medtech Growth II LP · Percent: 5.7% · SCHEDULE 13G/A
- · Holder: Spignesi Robert G Jr · Percent: 6.3% · SCHEDULE 13D
Rapid Micro Biosystems, Inc. has 5 Schedule 13D or 13G filings on record since 2025-08-19. 5 holders' latest filing reports 5% or more of class a common stock, par value $0.01 per share. Each figure below is the holder's own, as filed, with the filing linked.
Holders
| Holder | Percent | Shares | Latest | Event date |
|---|---|---|---|---|
| Bain Capital Life Sciences Fund, L.P. | 16.76% | 7,651,369 | SCHEDULE 13G/A, 2026-08-14 | 2026-06-30 |
| Longitude Capital Partners II, LLC | 8.6% | 3,529,245 | SCHEDULE 13G/A, 2026-05-15 | 2026-03-31 |
| Armistice Capital, LLC | 7.29% | 3,328,000 | SCHEDULE 13G, 2026-08-14 | 2026-06-30 |
| 6.3% | 2,647,256 | SCHEDULE 13D, 2025-08-19 | 2024-03-28 | |
| Endeavour Medtech Growth II LP | 5.7% | 2,257,099 | SCHEDULE 13G/A, 2026-02-13 | 2025-12-31 |
Holding shares or following this stake? See who's behind Rapid Micro Biosystems, Inc. and the warning signs.
Free to see. No signup.
Keep reading
More on Rapid Micro Biosystems, Inc. and the records around it.
Rapid Micro Biosystems, Inc. elsewhere on the record
Companies that share a holder
- Endeavour Medtech Growth II LP also filed stake reports on 1 other company: Kestra Medical Technologies, Ltd. (Feb 2026)
- Bain Capital Life Sciences Fund, L.P. also filed stake reports on 2 other companies: Pharvaris N.V. (Feb 2026), X4 PHARMACEUTICALS, INC. (Feb 2026)
- Armistice Capital, LLC also filed stake reports on 120 other companies: Autolus Therapeutics plc (Aug 2026), Bicycle Therapeutics plc (Aug 2026), BioXcel Therapeutics, Inc. (Aug 2026)
Watch Rapid Micro Biosystems, Inc.
Get an email when Rapid Micro Biosystems, Inc. files again: a new raise, a leadership change, a layoff or an IPO filing. One email first to confirm; nothing else until you click it. At most one a day, one click to stop. Free for up to 3 companies.
Want the whole picture on Rapid Micro Biosystems, Inc.?
Example from a real report (our sample on Target): “The Q2 2026 earnings report, published August 19, 2026, showed adjusted EPS of $2.46 against an expected $2.33” Source: CNBC
A Full Report on Rapid Micro Biosystems, Inc.: verified, sourced, every claim cited, ready in a few minutes. See pricing.
What the Full Report on Rapid Micro Biosystems, Inc. covers
The Short Answer
Which Company This Is
What They Do, And How The Money Works
Who Runs It, And How To Reach Them
The Money: Funding, Valuation, Runway
Who Pays Them, And Who They Are Up Against
Warning Bells
Sources
5 cited sources found
Plus the sections for what you are deciding, which you pick after ordering.
A real finished report, first screen. Opens in a new tab.
Not ready to order yet? Keep this snapshot.
Sends this preview to you once; we won't add you to any list
Voting and dispositive power, as filed
| Reporting person | Sole voting | Shared voting | Sole dispositive | Shared dispositive | Filing |
|---|---|---|---|---|---|
| Bain Capital Life Sciences Fund, L.P. | 0 | 7,651,369 | 0 | 7,651,369 | SCHEDULE 13G/A, 2026-08-14 |
| BCIP Life Sciences Associates, LP | 0 | 783,191 | 0 | 783,191 | SCHEDULE 13G/A, 2026-08-14 |
| Armistice Capital, LLC | 0 | 3,328,000 | 0 | 3,328,000 | SCHEDULE 13G, 2026-08-14 |
| Steven Boyd | 0 | 3,328,000 | 0 | 3,328,000 | SCHEDULE 13G, 2026-08-14 |
The latest filing identifies Rapid Micro Biosystems, Inc. by CUSIP 75340L104 and gives its principal executive office as 25 Hartwell Avenue, Lexington, MA 02421 (SCHEDULE 13G/A, 2026-08-14).
Purpose of Transaction (Item 4)
Spignesi Robert G Jr
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 …The first part of Item 4 of the SCHEDULE 13D filed 2025-08-19; the filing has the rest
Timeline
| Filed | Holder | Percent | Filing |
|---|---|---|---|
| 2025-08-19 | Spignesi Robert G Jr | 6.3% | SCHEDULE 13D |
| 2026-02-13 | Endeavour Medtech Growth II LP | 5.7% | SCHEDULE 13G/A |
| 2026-05-15 | Longitude Capital Partners II, LLC | 8.6% | SCHEDULE 13G/A |
| 2026-08-14 | Armistice Capital, LLC | 7.29% | SCHEDULE 13G |
| 2026-08-14 | Bain Capital Life Sciences Fund, L.P. | 16.76% | SCHEDULE 13G/A |
Questions about who owns Rapid Micro Biosystems, Inc.
Who owns Rapid Micro Biosystems, Inc.?
On this page, 5 holders' latest ownership filings report 5% or more of Rapid Micro Biosystems, Inc.: Bain Capital Life Sciences Fund, L.P. (16.76%, Schedule 13G/A, filed 2026-08-14), Longitude Capital Partners II, LLC (8.6%, Schedule 13G/A, filed 2026-05-15), Armistice Capital, LLC (7.29%, Schedule 13G, filed 2026-08-14), Spignesi Robert G Jr (6.3%, Schedule 13D, filed 2025-08-19) and Endeavour Medtech Growth II LP (5.7%, Schedule 13G/A, filed 2026-02-13).
Who are the largest shareholders of Rapid Micro Biosystems, Inc.?
By the share each holder's latest filing reports, the largest holders of Rapid Micro Biosystems, Inc. on this page are Bain Capital Life Sciences Fund, L.P. (16.76%), Longitude Capital Partners II, LLC (8.6%) and Armistice Capital, LLC (7.29%).
When did Bain Capital Life Sciences Fund, L.P. buy into Rapid Micro Biosystems, Inc.?
The filings give report dates, not purchase dates. The earliest filing from Bain Capital Life Sciences Fund, L.P. on this page is the Schedule 13G/A, filed 2026-08-14, reporting 16.76%. That earliest filing is itself an amendment, which updates an earlier report.
Is this an audit or a full list?
Neither. The ownership list on this page covers only Schedule 13D and 13G filings, which holders make once they own 5% or more of a class of shares (an amendment can report a stake that has since fallen below 5%); 5 such filings are shown here. It is not an audit and not a full cap table: holders who never reached 5% are not listed, and a stake can change after its latest filing.
Tools for this story
Each opens in a new tab, filled in for Rapid Micro Biosystems, Inc.. With no account yet, you sign up free and land on the result.
Where this comes from
Anyone who comes to own more than 5% of a class of a listed company's voting shares has to tell the SEC. A holder who may seek to change or influence the company files Schedule 13D, and has to say in Item 4, "Purpose of Transaction", what it intends to do. A holder with no such intent, such as many index and passive funds, may file the shorter Schedule 13G. Both are amended when the stake changes, including when it falls below 5%.
Every row here is one of those filings, linked to the filing itself. Percentages and share counts are exactly as the holder filed them, for the holder the filing names; an amendment showing a lower figure is shown as filed. Item 4 text is quoted word for word. Where a 13D's Item 4 contains a sentence stating a definite intent to influence the company, that sentence is marked and quoted; the page does not describe the holder or its motives beyond the words it filed. Nothing here is investment advice.