The insider sales are too small relative to market cap to carry a bearish signal. The historical track record of insider signals on this ticker has been poor (44% win rate, negative average alpha). Ignore this cluster as routine portfolio diversification. Monitor for any material news (pipeline updates, earnings) that could explain the timing, but do not trade on this filing alone.
Price Chart
Executive Summary
Two C-suite insiders at Prothena (PRTA) sold a combined $136K in open-market sales on July 29, 2026, following tax-withholding transactions on July 28. The sales represent 0.03% of the $448M market cap, which is trivial. The cluster is not amplified by the proportionality band, and the historical calibration for this ticker shows a 44% win rate at T+20 with negative average alpha, suggesting insider signals here have been unreliable. The cross-filing actuarial verdicts show all pairs as amplifiers, but the standalone dollar amount is too small to warrant a directional score.
Key Financial Metrics
Key Facts
- General Counsel Michael John Isaacs sold 8,386 shares at $8.47 for $71K
- Chief Strategy Officer Anne Evans sold 7,662 shares at $8.47 for $65K
- Both insiders also had tax-withholding transactions on July 28 (non-cash, no economic signal)
- Total open-market sales = $136K, or 0.03% of $448M market cap
- No insider buying in the cluster; net direction is selling
Financial Impact
Total open-market sales of $136K represent 0.03% of market cap — immaterial
Risk Factors
- Insider sales could precede negative news, but the dollar amount is too small to be predictive
- Historical insider signals on PRTA have underperformed, reducing reliability
Market Snapshot
Investment Themes
Documents Analyzed
This report is based on 1 SEC document filed with EDGAR.
| Document | Accession Number |
|---|---|
| CLUSTER Data (Synthetic) | cluster-PRTA-1785457900635 |
Filters
| Type | Now | ||||
|---|---|---|---|---|---|
Sep 3, 2026 28d ago | Insider Buy | $9.82 $8.86 | ▼ −9.78% | ▼ −8.57% | $8.44 (−14.05%) |
Aug 21, 2026 6w ago | Insider Buy | $9.45 $9.33 | ▼ −1.27% | ▼ −1.74% | $8.44 (−10.69%) |
Aug 10, 2026 7w ago | Insider Buy | $9.12 $8.88 | ▼ −2.63% | ▼ −2.58% | $8.44 (−7.46%) |
Jul 31, 2026 9w ago | Insider Cluster | $8.12 $8.76 | ▲ +7.88% | ▲ +4.37% | $8.44 (+3.94%) |
Jun 18, 2026 15w ago | Insider Buy | $8.93 $9.27 | ▲ +3.81% | ▲ +5.47% | $8.44 (−5.49%) |
Jun 12, 2026 15w ago | Insider Buy | $8.15 $9.15 | ▲ +12.27% | ▲ +13.65% | $8.44 (+3.56%) |
May 14, 2026 20w ago | 3 | $9.76 $9.83 | ▲ +0.72% | ▼ −0.25% | $8.44 (−13.52%) |
May 7, 2026 21w ago | 8-K | $10.73 $9.86 | ▼ −8.11% | ▼ −9.57% | $8.44 (−21.34%) |
Mar 27, 2026 26w ago | DEFA14A | $9.25 $10.36 | ▲ +12.00% | ▲ +7.70% | $8.44 (−8.76%) |
Mar 3, 2026 30w ago | EFFECT | $9.36 $9.77 | ▲ +4.38% | ▲ +4.86% | $8.44 (−9.83%) |
US Market Status
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