As of August 29, 2026, the three largest insider holders of JBIO are Venture Partners X, L.P. Sofinnova (TenPercentOwner, 3.76Mn shares), Venture Fund Xii, L.P. Atlas (TenPercentOwner, 2.33Mn shares), Funds Management Llc Fairmount (Director, 1.90Mn shares).
| # | Insider | Position | Direct | Indirect | Total | Share of Insiders | Last Filed |
|---|---|---|---|---|---|---|---|
| 1 | Venture Partners X, L.P. Sofinnova | TenPercentOwner | 3,758,686 | 0 | 3,758,686 | 44.0% | 06 Jul, 2021 |
| 2 | Venture Fund Xii, L.P. Atlas | TenPercentOwner | 2,327,909 | 0 | 2,327,909 | 27.2% | 19 Jul, 2022 |
| 3 | Funds Management Llc Fairmount | Director, TenPercentOwner | 0 | 1,897,677 | 1,897,677 | 22.2% | 08 Oct, 2025 |
| 4 | Andrew James King | Officer | 386,113 | 0 | 386,113 | 4.5% | 13 Feb, 2026 |
| 5 | Tom Frohlich | Chief Executive Officer | 86,331 | 0 | 86,331 | 1.0% | 13 Feb, 2026 |
| 6 | Bradford D. Dahms | Chief Financial Officer | 37,813 | 0 | 37,813 | 0.4% | 13 Feb, 2026 |
| 7 | Elizabeth Balta | Officer | 28,125 | 0 | 28,125 | 0.3% | 13 Feb, 2026 |
| 8 | Benjamin T Dake | Officer | 14,252 | 0 | 14,252 | 0.2% | 02 Aug, 2024 |
| 9 | Hunter Gillies | Chief Medical Officer | 5,602 | 0 | 5,602 | 0.1% | 14 Jun, 2024 |
| 10 | George A Eldridge | Officer | 5,022 | 0 | 5,022 | 0.1% | 14 Jun, 2024 |
| 11 | Ralph Niven | Chief Scientific Officer | 1,609 | 0 | 1,609 | 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 | Christopher W. Cain | 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 |
| 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 |
| 12 Feb, 2026 | Elizabeth Balta | Officer | Acquired A | 28,125 | $0.00 | $0 | 28,125 | 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 | Tom Frohlich | Chief Executive Officer | Acquired A | 78,750 | $0.00 | $0 | 86,331 | Direct |
| 12 Feb, 2026 | Andrew James King | Officer | Acquired A | 41,250 | $0.00 | $0 | 386,113 | Direct |
| 12 Feb, 2026 | Andrew James King | Officer | Acquired A | 41,250 | $0.00 | $0 | 386,113 | Direct |
| 12 Feb, 2026 | Andrew James King | Officer | Acquired A | 41,250 | $0.00 | $0 | 386,113 | Direct |
| 12 Feb, 2026 | Andrew James King | Officer | Acquired A | 247,500 | $0.00 | $0 | 247,500 | Direct |
| 12 Feb, 2026 | Tom Frohlich | Chief Executive Officer | Acquired A | 472,500 | $0.00 | $0 | 472,500 | Direct |
| 12 Feb, 2026 | Andrew James King | Officer | Acquired A | 247,500 | $0.00 | $0 | 247,500 | Direct |
| 12 Feb, 2026 | Andrew James King | Officer | Acquired A | 247,500 | $0.00 | $0 | 247,500 | Direct |
| 12 Feb, 2026 | Andrew James King | Officer | Acquired A | 247,500 | $0.00 | $0 | 247,500 | Direct |
| 12 Feb, 2026 | Bradford D. Dahms | Chief Financial Officer | Acquired A | 226,875 | $0.00 | $0 | 226,875 | Direct |
| 12 Feb, 2026 | Elizabeth Balta | Officer | Acquired A | 168,750 | $0.00 | $0 | 168,750 | Direct |
| 06 Oct, 2025 | Funds Management Llc Fairmount | Director, TenPercentOwner | Acquired A | 1,333,126 | $9.14 | $12.18Mn | 1,897,677 | Indirect |