The simultaneous large buy and sell by two major 10% owners creates a split signal. EcoR1's $4.74M purchase is a bullish vote of confidence, but Panacea's $3.17M sale suggests some insiders are taking profits. Given ATRA's small $71M market cap and the historical pattern of poor T+20 performance on prior calls, traders should wait for a clearer directional catalyst (e.g., earnings, pipeline update) before taking a position.
Price Chart
Executive Summary
Atara Biotherapeutics saw a mixed insider cluster: 10% owner EcoR1 Capital bought $4.74M worth of shares, while director/10% owner Panacea Innovation sold $3.17M worth on the same day. The net $1.57M buying is modest relative to ATRA's $71M market cap (~2.2%), but the simultaneous insider buying and selling creates a conflicting signal that warrants caution.
Key Financial Metrics
Key Facts
- EcoR1 Capital purchased 507,407 shares at $9.35 for $4.74M on 2026-05-07
- Panacea Innovation sold 313,446 shares at $10.10 for $3.17M on 2026-05-07
- Net insider buying of ~$1.57M, representing ~2.2% of ATRA's $71M market cap
- Both parties are 10% owners; no C-suite insiders traded
- Historical calibration shows past neutral calls on ATRA had a 25% win rate at T+20 with avg alpha of -10.81%
Financial Impact
Net insider buying of ~$1.57M, ~2.2% of market cap
Risk Factors
- Insider selling by a 10% owner may signal lack of confidence in near-term prospects
- ATRA's small market cap makes it highly volatile; past neutral calls have underperformed SPY by -10.81% at T+20
- No C-suite participation reduces the signal strength of insider activity
Market Snapshot
Investment Themes
Documents Analyzed
This report is based on 1 SEC document filed with EDGAR.
| Document | Accession Number |
|---|---|
| CLUSTER Data (Synthetic) | cluster-ATRA-1778539528445 |
Filters
| Type | Now | ||||
|---|---|---|---|---|---|
Jun 26, 2026 14w ago | 8-K | $11.17 $8.93 | ▼ −20.05% | ▼ −24.44% | $9.48 (−15.13%) |
Jun 15, 2026 15w ago | 3 | $9.62 $9.89 | ▲ +2.81% | ▲ +1.81% | $9.48 (−1.46%) |
May 7, 2026 21w ago | 8-K | $9.93 $8.55 | ▼ −13.90% | ▼ −17.73% | $9.48 (−4.53%) |
May 7, 2026 21w ago | Insider Cluster | $9.93 $8.55 | ▼ −13.90% | ▼ −17.73% | $9.48 (−4.53%) |
Apr 24, 2026 23w ago | DEFA14A | $4.99 $8.13 | ▲ +62.83% | ▲ +58.05% | $9.48 (+89.98%) |
Mar 17, 2026 28w ago | S-3 | $5.00 $10.46 | ▲ +109.20% | ▲ +97.67% | $9.48 (+89.60%) |
Mar 12, 2026 29w ago | 8-K | $6.90 $9.92 | ▲ +43.77% | ▲ +33.07% | $9.48 (+37.39%) |
Mar 3, 2026 30w ago | 8-K | $5.42 $10.54 | ▲ +94.46% | ▲ +84.15% | $9.48 (+74.91%) |
Mar 2, 2026 30w ago | Insider Cluster | $4.91 $9.61 | ▲ +95.72% | ▲ +86.40% | $9.48 (+93.08%) |
US Market Status
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