As of September 29, 2026, the three largest insider holders of JBIO are Funds Management Llc Fairmount (Director, 1.90Mn shares), Andrew James King (Officer, 386.11K shares), Tom Frohlich (Chief Executive Officer, 86.33K shares).
| # | Insider | Position | Direct | Indirect | Total | Share of Insiders | Last Filed |
|---|---|---|---|---|---|---|---|
| 1 | Funds Management Llc Fairmount | Director, TenPercentOwner | 0 | 1,897,677 | 1,897,677 | 74.7% | 08 Oct, 2025 |
| 2 | Andrew James King | Officer | 386,113 | 0 | 386,113 | 15.2% | 13 Feb, 2026 |
| 3 | Tom Frohlich | Chief Executive Officer | 86,331 | 0 | 86,331 | 3.4% | 13 Feb, 2026 |
| 4 | Venture Fund Xii, L.P. Atlas | TenPercentOwner | 66,508 | 0 | 66,508 | 2.6% | 19 Jul, 2022 |
| 5 | Bradford D. Dahms | Chief Financial Officer | 37,813 | 0 | 37,813 | 1.5% | 13 Feb, 2026 |
| 6 | Capital Management, L.P. Ra | TenPercentOwner | 0 | 36,794 | 36,794 | 1.4% | 30 Apr, 2025 |
| 7 | Elizabeth Balta | Officer | 28,125 | 0 | 28,125 | 1.1% | 13 Feb, 2026 |
| 8 | David S. Grayzel | Director | 0 | 414 | 414 | 0.0% | 11 Apr, 2024 |
| 9 | Benjamin T Dake | Officer | 407 | 0 | 407 | 0.0% | 02 Aug, 2024 |
| 10 | Hunter Gillies | Chief Medical Officer | 160 | 0 | 160 | 0.0% | 14 Jun, 2024 |
| 11 | George A Eldridge | Officer | 143 | 0 | 143 | 0.0% | 14 Jun, 2024 |
| 12 | Ralph Niven | Chief Scientific Officer | 46 | 0 | 46 | 0.0% | 07 Feb, 2024 |
Each row is that insider’s most recently reported position, from Form 4 filings over the last 60 months — which is why this total does not tie to the quarterly series above, where a quarter counts only the insiders who filed in it. Shares held through a fund or institutional portfolio are counted on the institutional ownership page instead.
| Date | Insider | Position | Transaction | Shares | Price | Value | Shares Held After | Ownership |
|---|---|---|---|---|---|---|---|---|
| 25 Jun, 2026 | Mark Eisner | Director | Acquired A | 47,675 | $0.00 | $0 | 47,675 | Direct |
| 09 Jun, 2026 | Funds Management Llc Fairmount | Director, TenPercentOwner | Acquired A | 34,843 | $0.00 | $0 | 34,843 | Direct |
| 09 Jun, 2026 | Christopher W. Cain | Director | Acquired A | 34,843 | $0.00 | $0 | 34,843 | Direct |
| 09 Jun, 2026 | Lawrence Otto Klein | Director | Acquired A | 34,843 | $0.00 | $0 | 34,843 | Direct |
| 09 Jun, 2026 | Erin Lavelle | Director | Acquired A | 34,843 | $0.00 | $0 | 34,843 | Direct |
| 09 Jun, 2026 | Eric Dobmeier | Director | Acquired A | 34,843 | $0.00 | $0 | 34,843 | Direct |
| 12 Feb, 2026 | Andrew James King | Officer | Acquired A | 41,250 | $0.00 | $0 | 386,113 | Direct |
| 12 Feb, 2026 | Bradford D. Dahms | Chief Financial Officer | Acquired A | 37,813 | $0.00 | $0 | 37,813 | Direct |
| 12 Feb, 2026 | Elizabeth Balta | Officer | Acquired A | 28,125 | $0.00 | $0 | 28,125 | Direct |
| 12 Feb, 2026 | Tom Frohlich | Chief Executive Officer | Acquired A | 78,750 | $0.00 | $0 | 86,331 | Direct |
| 12 Feb, 2026 | Tom Frohlich | Chief Executive Officer | Acquired A | 472,500 | $0.00 | $0 | 472,500 | Direct |
| 12 Feb, 2026 | Elizabeth Balta | Officer | Acquired A | 168,750 | $0.00 | $0 | 168,750 | Direct |
| 12 Feb, 2026 | Bradford D. Dahms | Chief Financial Officer | Acquired A | 226,875 | $0.00 | $0 | 226,875 | Direct |
| 12 Feb, 2026 | Andrew James King | Officer | Acquired A | 247,500 | $0.00 | $0 | 247,500 | Direct |
| 06 Oct, 2025 | Funds Management Llc Fairmount | Director, TenPercentOwner | Acquired A | 1,333,126 | $9.14 | $12.18Mn | 1,897,677 | Indirect |
| 06 Oct, 2025 | Funds Management Llc Fairmount | Director, TenPercentOwner | Acquired A | 855,047 | $9.14 | $7.82Mn | 855,047 | Indirect |
| 14 Jul, 2025 | Bradford D. Dahms | Chief Financial Officer | Acquired A | 526,000 | $0.00 | $0 | 526,000 | Direct |
| 16 May, 2025 | Tom Frohlich | Chief Executive Officer | Acquired P | 6,000 | $7.40 | $44.40K | 6,000 | Direct |
| 29 Apr, 2025 | Lawrence Otto Klein | Director | Acquired A | 23,017 | $0.00 | $0 | 658 | Direct |
| 29 Apr, 2025 | Eric Dobmeier | Director | Acquired A | 23,017 | $0.00 | $0 | 658 | Direct |