Insider Buy ·Filed Sep 30, 2026
Insider cluster: 1 insiders, $2.3M total
Actionable Insight ▲ Bullish
Monitor for additional insider buying or a material catalyst (e.g., pipeline update) that could explain the conviction. The stock's recent decline may present a value entry if fundamentals support.
Latest settled — T+5d ⚠ clustered
PRTA ▲ +0.82% at T+5d
LONG call ✓ call won +0.82% · α vs SPY -0.48% · entry $8.54 → $8.61
Latest observation: T+16 -1.10% FF3 residual α
T+1d
-2.11%
call -2.11% · α -2.85%
$8.36
settled 26d ago
T+5d
+0.82%
call +0.82% · α -0.48%
$8.61
settled 20d ago
T+20d
Pending
in 18h
T+60d
Pending
in 8w
Price Chart
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Executive Summary
10% owner William P. Scully purchased 265,500 shares of Prothena for ~$2.30M in open-market transactions on September 28-29, 2026, at an average price of ~$8.66.
Key Financial Metrics
Direction
buying
Total Value
$2.3M
Insiders
1
Key Facts
- 10% owner William P. Scully bought 103,500 shares at $8.5978 on 2026-09-28, totaling ~$890K
- Scully bought 162,000 shares at $8.68 on 2026-09-29, totaling ~$1.41M
- Total open-market purchase: 265,500 shares for ~$2.30M
- Average purchase price: ~$8.66 per share
- No other insiders traded in the 7-day window
Financial Impact
~$2.30M in insider purchases by a 10% owner, representing a material vote of confidence
insider ownershipmarket sentiment
Risk Factors
- No disclosed catalyst for the purchase — could be averaging down rather than new information
- Biotech sector risk: PRTA is a clinical-stage company with binary pipeline events
Investment Themes
Documents Analyzed
This report is based on 1 SEC document filed with EDGAR.
| Document | Accession Number |
|---|---|
| INSIDER-BUY Data (Synthetic) | 0001045463-26-000018 |
15 reports for PRTA
63% Hit rate @ T+1 Went positive at some point 5 of 8 best @ T+60▲ +14.11%
Filters
Rows
| Type | Now | ||||
|---|---|---|---|---|---|
Oct 26, 2026 today | Insider Buy | $8.40 | awaiting T+1 | — | $8.71 (+3.69%) |
Oct 15, 2026 11d ago | Insider Buy | $8.35 $8.48 | ▲ +1.56% | ▲ +1.13% | $8.71 (+4.31%) |
Sep 30, 2026 26d ago | Insider Buy | $8.54 $8.36 | ▼ −2.11% | ▼ −2.85% | $8.71 (+1.99%) |
Sep 29, 2026 27d ago | Insider Buy | $8.38 $8.54 | ▲ +1.91% | ▲ +1.73% | $8.71 (+3.94%) |
Sep 21, 2026 5w ago | Insider Buy | $8.99 $8.68 | ▼ −3.45% | ▼ −2.73% | $8.71 (−3.11%) |
Sep 3, 2026 7w ago | Insider Buy | $9.82 $9.54 | ▼ −2.85% | ▼ −2.30% | $8.71 (−11.30%) |
Aug 21, 2026 9w ago | Insider Buy | $9.45 $9.39 | ▼ −0.63% | ▼ −0.34% | $8.71 (−7.83%) |
Aug 10, 2026 11w ago | Insider Buy | $9.12 $9.22 | ▲ +1.10% | ▲ +1.42% | $8.71 (−4.50%) |
Jul 30, 2026 12w ago | Insider Cluster | $8.12 $8.33 | ▲ +2.59% | ▲ +1.16% | $8.71 (+7.27%) |
Jun 18, 2026 18w ago | Insider Buy | $8.93 $9.15 | ▲ +2.46% | ▲ +2.78% | $8.71 (−2.46%) |
Showing 10 of 15
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