Rapid Micro Biosystems
Automates microbial quality-control workflows for pharmaceutical, medical-device, and personal-care manufacturing.
$1.57
After-hours close0.00 (0.00%)
At close$1.57(−2.48%)
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Breakdown13F · Form 4
Institutions 34.95%15.84M sharesInsiders 5.50%2.49M sharesOther 59.55%26.99M shares
Shares outstanding 45.32M · Float 26.44M · 58.3% free float
Institutions13F, as of Mar 31, 2026
46 holders · 15.84M shares · 13 new positions · 30 increased · 9 reduced · 9 closed
| Holder | Shares | % outstanding | Chg q/q | Filed |
|---|---|---|---|---|
| Bain Capital Life Sciences Investors, LLC | 8.43M | 18.61% | 0 | May 15, 2026 |
| Abg-WTT Global Life Science Capital Partners GP Ltd | 1.85M | 4.08% | 0 | May 18, 2026 |
| Vanguard Capital Management LLC | 982.5K | 2.17% | +982.5Knew | May 15, 2026 |
| Essex Investment Management Co LLC | 883.9K | 1.95% | +821.6K | May 11, 2026 |
| Advent International Corp/MA | 552.4K | 1.22% | −25.4K | May 15, 2026 |
| Evernest Financial Advisors, LLC | 432.5K | 0.95% | +307.5K | May 4, 2026 |
| SEI Investments Co | 284.8K | 0.63% | +191.2K | May 13, 2026 |
| Millennium Management LLC | 283.3K | 0.63% | +166.8K | May 15, 2026 |
Beneficial owners13D/G · 5% or more, as filed
| Holder | % of class | Shares | Form | Filed |
|---|---|---|---|---|
| Longitude Capital Partners II, LLC | 8.60% | 3.53M | 13G | May 15, 2026 ↗ |
| Armistice Capital, LLC | 7.29% | 3.33M | 13G | Aug 14, 2026 ↗ |
| Spignesi Robert G Jr | 6.30% | 2.65M | 13D | Aug 19, 2025 ↗ |
| Endeavour Medtech Growth II LP | 5.70% | 2.26M | 13G | Feb 13, 2026 ↗ |
InsidersForm 4
| Insider | Role | Shares | % outstanding | Filed |
|---|---|---|---|---|
| Robert G. Jr. Spignesi | director, officer: PRESIDENT AND CEO | 1.19M | 2.63% | Jul 24, 2026 |
| Sean M. Wirtjes | officer: CHIEF FINANCIAL OFFICER | 569.0K | 1.26% | Jun 2, 2026 |
| John J. Addington Wilson | officer: CHIEF OPERATING OFFICER | 316.8K | 0.70% | Mar 12, 2026 |
| Richard S. Kollender | director | 132.0K | 0.29% | Jul 24, 2026 |
| Melinda Litherland Pei | director | 100.7K | 0.22% | Jun 2, 2026 |
| Inese Lowenstein | director | 70.7K | 0.16% | Jun 2, 2026 |
| Kirk Malloy | director | 60.7K | 0.13% | Jun 2, 2026 |
| Natale S. Ricciardi | director | 29.4K | 0.06% | Mar 2, 2026 |
| Dafni Bika | director | 19.3K | 0.04% | May 26, 2026 |
4 ten-percent owners hold 9.48M shares by Form 4, outside the officers-and-directors figure above · 6 people have not refiled in the last 18 months (2.35M shares), so they are not in the figure above
Latest trades
| Date | Insider | Type | Shares | Avg price | Owned after |
|---|---|---|---|---|---|
| May 20, 2026 | Bain Capital Life Sciences Investors, LLC10 percent owner | Purchase · 3 lots | 4,389,000 | $1.44 | 4,389,000 |
| Mar 10, 2026 | Robert G. Jr. Spignesidirector, officer: PRESIDENT AND CEO | Sale | 17,922 | $4.11 | 1,169,848 |
| Mar 11, 2026 | Sean M. Wirtjesofficer: CHIEF FINANCIAL OFFICER | Sale | 7,480 | $4.32 | 556,194 |
| Mar 11, 2026 | John J. Addington Wilsonofficer: CHIEF OPERATING OFFICER | Sale | 9,603 | $4.32 | 316,762 |
| Feb 19, 2026 | Robert G. Jr. Spignesidirector, officer: PRESIDENT AND CEO | Sale | 38,327 | $3.89 | 1,187,770 |
| Feb 20, 2026 | Sean M. Wirtjesofficer: CHIEF FINANCIAL OFFICER | Sale | 17,254 | $3.92 | 563,674 |
| Feb 20, 2026 | John J. Addington Wilsonofficer: CHIEF OPERATING OFFICER | Sale | 5,403 | $3.92 | 326,365 |
| Feb 9, 2026 | Robert G. Jr. Spignesidirector, officer: PRESIDENT AND CEO | Sale | 12,840 | $3.78 | 962,097 |
| Feb 9, 2026 | Sean M. Wirtjesofficer: CHIEF FINANCIAL OFFICER | Sale | 6,027 | $3.78 | 483,928 |
| Feb 9, 2026 | John J. Addington Wilsonofficer: CHIEF OPERATING OFFICER | Sale | 4,610 | $3.78 | 257,768 |
CongressHouse and Senate disclosures
Not reported.