The 10% owner's open-market purchase is a positive signal, but PRTA's historical stock response to bullish calls has been poor (avg -4.55% at T+20). Watch for pipeline catalysts or earnings updates to confirm the insider's conviction. A small position relative to market cap limits immediate impact.
Price Chart
Executive Summary
William P. Scully, a 10% owner of Prothena Corp, purchased $1.18M of PRTA shares in two open-market transactions at ~$8.10 per share. This conviction buy by a major insider signals confidence, though historical bullish calls on PRTA have underperformed.
Key Financial Metrics
Key Facts
- 10% owner William P. Scully bought 145,000 shares total for $1.18M
- Purchases occurred on June 11 ($1.02M at $8.17) and June 16 ($158K at $7.90)
- Total buy represents ~0.27% of PRTA's $444M market cap
- Insider has been net buying over the past 30 days ($3.1M total)
Financial Impact
Insider purchase of $1.18M, modest relative to market cap
Risk Factors
- Historical bullish calls on PRTA have underperformed (40% win rate at T+20)
- Purchase size is modest at 0.27% of market cap
- Biotech sector risk with binary pipeline events
Market Snapshot
Investment Themes
Documents Analyzed
This report is based on 1 SEC document filed with EDGAR.
| Document | Accession Number |
|---|---|
| INSIDER-BUY Data (Synthetic) | 0001045463-26-000009 |
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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