Updated Jul 16, 2026
EcoR1 Capital, LLC has filed 2 SEC Form 4 filings across 2 companies in the last 90 days — active on both sides. Lifetime open-market purchases: $96.63M. Lifetime open-market sales: $80.33M. Historical track record: 1/5 stars across 6 tracked purchases.
| Role | 10% Owner |
|---|
InsiderAlpha computes a forward-return-based score for every insider with enough Form 4 purchase history. The metrics below reflect realised performance after each tracked open-market purchase.
| InsiderAlpha rating | ★☆☆☆☆ (1/5) |
|---|---|
| Total purchases tracked | 6 |
| Purchases with forward-return data | 6 |
| 30-day win rate | 1667% |
| 90-day win rate | 0% |
| Avg 5-day return | -411.63% |
| Avg 30-day return | -553.04% |
| Avg 90-day return | -1323.90% |
| Best 30-day return | +480.91% |
| Date | Ticker | Company | Code | Shares | Price | Value |
|---|---|---|---|---|---|---|
| 2026-05-11 | ATRA | Atara Biotherapeutics, Inc. | P — Open-market purchase | 507.4K | $9.35 | $4.74M |
| 2026-04-22 | TRAX | First Tracks Biotherapeutics, Inc. | S — Open-market sale | 4.71M | $13.81 | $65.00M |
| 2026-01-13 | AKTS | Aktis Oncology, Inc. | P — Open-market purchase | 144.4K | $18.00 | $2.60M |
| 2026-01-13 | AKTS | Aktis Oncology, Inc. | P — Open-market purchase | 2.08M | $18.00 | $37.40M |
| 2026-01-13 | AKTS | Aktis Oncology, Inc. | J — Other acquisition / disposition | 128.5K | — | |
| 2026-01-13 | AKTS | Aktis Oncology, Inc. | J — Other acquisition / disposition | 202.9K | — | |
| 2026-01-13 | AKTS | Aktis Oncology, Inc. | J — Other acquisition / disposition | 2.27M | — | |
| 2025-07-28 | ADAP | Adaptimmune Therapeutics PLC | S — Open-market sale | 27.43M | $0.10 | $2.80M |
| 2025-07-28 | ADAP | Adaptimmune Therapeutics PLC | S — Open-market sale | 2.69M | $0.10 | $272K |
| 2025-07-28 | ADAP | Adaptimmune Therapeutics PLC | S — Open-market sale | 33.93M | $0.11 | $3.82M |
| 2024-12-27 | ZYME | Zymeworks Inc. | P — Open-market purchase | 101.7K | $14.49 | $1.47M |
| 2024-12-27 | ZYME | Zymeworks Inc. | P — Open-market purchase | 16.7K | $14.38 | $240K |
| 2024-12-27 | ZYME | Zymeworks Inc. | P — Open-market purchase | 12.0K | $14.12 | $169K |
| 2024-12-23 | MRSN | Mersana Therapeutics, Inc. | J — Other acquisition / disposition | 8.04M | — | |
| 2024-11-08 | TNGX | Tango Therapeutics, Inc. | S — Open-market sale | 1.14M | $2.92 | $3.33M |
| 2024-11-08 | TNGX | Tango Therapeutics, Inc. | S — Open-market sale | 62.3K | $3.29 | $205K |
| 2024-11-08 | TNGX | Tango Therapeutics, Inc. | S — Open-market sale | 1.49M | $3.28 | $4.90M |
EcoR1 Capital, LLC is a corporate insider — currently tracked as 10% Owner of Atara Biotherapeutics, Inc. (ATRA). InsiderAlpha tracks every SEC Form 4 filing in real time.
2 primary Form 4 filings in the last 90 days, covering 2 companies.
Recorded transactions: 7 open-market purchases ($96.63M) and 7 open-market sales ($80.33M) across all tracked filings.
Across 6 tracked purchases, EcoR1 Capital, LLC averaged -553.0% avg 30-day return with a 1667% 30-day win rate. InsiderAlpha rates the track record at 1/5 stars.
All Form 4 filings, transaction values, and 10b5-1 plan flags are listed on this page and updated in real time as new SEC EDGAR filings are processed.
Open the live EcoR1 Capital, LLC profile on InsiderAlpha for real-time alerts, AI-scored trade ideas, and full transaction history.