Atlas Venture Life Science Advisors, LLC
In its 13F for Q4 2025 (holdings as of December 31, 2025, filed February 13, 2026), Atlas Venture Life Science Advisors, LLC reported 8 stock positions worth $865.2 million. Its top holding was Kymera Therapeutics (KYMR) at 41.9% of the portfolio, followed by Dyne Therapeutics (DYN, 20.6%) and Sionna Therapeutics (SION, 14.2%). Compared with Q3 2025, it opened 1 new position, sold out of 2 and reduced 4. The biggest buy was a new position in Generation Bio (GBIO) and the biggest sale Disc Medicine (IRON, shares −29%).
- Most Recent 13F
- Q2 2026
- Location
- CAMBRIDGE, MA
- CIK
- 0001917529
- Portfolio Value
- $865.2M (Q4 2025)
- SEC Filing
- 0001104659-26-014463 ↗ filed Feb 13, 2026
Holdings Value
Holdings 8 stocks · $865.2M
| KYMR Kymera Therapeutics Inc. | 41.91% | 4,659,874 | $362.6M | Reduce -4.8% |
| DYN Dyne Therapeutics Inc. | 20.64% | 9,130,465 | $178.6M | No change |
| SION Sionna Therapeutics Inc. | 14.24% | 2,995,602 | $123.2M | Reduce -17.1% |
| IRON Disc Medicine Inc. | 13.90% | 1,513,875 | $120.2M | Reduce -29.3% |
| DAWN Day One Biopharmaceuticals I | 6.91% | 6,412,560 | $59.8M | Reduce -0.3% |
| KRRO Korro Bio Inc. | 1.05% | 1,137,149 | $9.1M | No change |
| QTTB Q32 Bio Inc. | 0.80% | 2,092,106 | $6.9M | No change |
| GBIO Generation Bio Co. | 0.54% | 827,946 | $4.7M | New |
Portfolio Sells Q3 2025 → Q4 2025
| IRON Disc Medicine Inc. | Reduce -29.3% | 13.90% | −4.92 |
| GBIO Generation Bio Co. | Sold out | 0.00% | −0.67 |
| IMA Imagenebio Inc. | Sold out | 0.00% | −0.41 |
| SION Sionna Therapeutics Inc. | Reduce -17.1% | 14.24% | +0.12 |
| DAWN Day One Biopharmaceuticals I | Reduce -0.3% | 6.91% | +0.88 |
| KYMR Kymera Therapeutics Inc. | Reduce -4.8% | 41.91% | +5.09 |
Portfolio Buys Q3 2025 → Q4 2025
| GBIO Generation Bio Co. | New | 0.54% | +0.54 |
All Filings
| Quarter | Positions | 13F Reported Value | Top Holdings |
|---|---|---|---|
| Q2 2026 | 7 | $881.3M | KYMR, DYN, SION, KLRA, IRON |
| Q1 2026 | 6 | $790.0M | KYMR, DYN, SION, IRON, QTTB |
| Q4 2025 | 8 | $865.2M | KYMR, DYN, SION, IRON, DAWN |
| Q3 2025 | 9 | $752.6M | KYMR, IRON, DYN, SION, KRRO |
| Q2 2025 | 11 | $662.4M | KYMR, IRON, DYN, SION, THRD |
| Q1 2025 | 13 | $521.8M | KYMR, IRON, DYN, DAWN, SION |
| Q4 2024 | 13 | $819.7M | KYMR, DYN, IRON, THRD, DAWN |
| Q3 2024 | 14 | $1.1B | DYN, KYMR, THRD, IRON, QTTB |
| Q2 2024 | 15 | $949.6M | DYN, KYMR, THRD, IRON, DAWN |
| Q1 2024 | 16 | $1.1B | DYN, KYMR, IRON, DAWN, THRD |