Insider Buy ·Filed Oct 15, 2026
Insider cluster: 1 insiders, $835K total
Actionable Insight ▲ Bullish
A 10% owner's open-market buy of this size is a strong insider signal. Monitor for any upcoming corporate events (earnings, pipeline updates, or strategic announcements) that may have motivated the purchase.
Latest settled — T+5d ⚠ clustered
PRTA ▼ -1.80% at T+5d
LONG call ✗ call lost -1.80% · α vs SPY -1.37% · entry $8.35 → $8.20
T+1d
+1.56%
call +1.56% · α +1.13%
$8.48
settled 11d ago
T+5d
-1.80%
call -1.80% · α -1.37%
$8.20
settled 5d ago
T+20d
Pending
in 16d
T+60d
Pending
in 3mo
Price Chart
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Executive Summary
10% owner William P. Scully purchased 100,000 shares of Prothena Corp for $835K in an open-market transaction on October 13, 2026. This is a substantial conviction buy by a major insider, representing a meaningful vote of confidence in the company's prospects.
Key Financial Metrics
Direction
buying
Total Value
$835.0K
Insiders
1
Key Facts
- 10% owner William P. Scully bought 100,000 shares at $8.35/share for a total of $835K
- Open-market purchase (code P) — not a planned or derivative transaction
- Purchase represents approximately 0.26% of market cap ($326M)
- Single insider conviction buy — no other insiders traded in the window
Financial Impact
$835K open-market purchase by a 10% owner — 0.26% of market cap
insider ownershipmarket cap
Risk Factors
- The purchase is by a 10% owner, not a C-suite executive — slightly less informative than a CEO/CFO buy
- Biotech sector risk: clinical trial outcomes are binary and can overwhelm insider signals
Investment Themes
Documents Analyzed
This report is based on 1 SEC document filed with EDGAR.
| Document | Accession Number |
|---|---|
| INSIDER-BUY Data (Synthetic) | 0001045463-26-000021 |
15 reports for PRTA
50% 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 | — | $8.53 (+1.61%) |
Oct 15, 2026 11d ago | Insider Buy | $8.35 $8.48 | ▲ +1.56% | ▲ +1.13% | $8.53 (+2.22%) |
Sep 30, 2026 26d ago | Insider Buy | $8.54 $8.36 | ▼ −2.11% | ▼ −2.85% | $8.53 (−0.06%) |
Sep 29, 2026 27d ago | Insider Buy | $8.38 $8.54 | ▲ +1.91% | ▲ +1.73% | $8.53 (+1.85%) |
Sep 21, 2026 5w ago | Insider Buy | $8.99 $8.68 | ▼ −3.45% | ▼ −2.73% | $8.53 (−5.06%) |
Sep 3, 2026 7w ago | Insider Buy | $9.82 $9.54 | ▼ −2.85% | ▼ −2.30% | $8.53 (−13.09%) |
Aug 21, 2026 9w ago | Insider Buy | $9.45 $9.39 | ▼ −0.63% | ▼ −0.34% | $8.53 (−9.68%) |
Aug 10, 2026 11w ago | Insider Buy | $9.12 $9.22 | ▲ +1.10% | ▲ +1.42% | $8.53 (−6.41%) |
Jul 30, 2026 12w ago | Insider Cluster | $8.12 $8.33 | ▲ +2.59% | ▲ +1.16% | $8.53 (+5.11%) |
Jun 18, 2026 18w ago | Insider Buy | $8.93 $9.15 | ▲ +2.46% | ▲ +2.78% | $8.53 (−4.42%) |
Showing 10 of 15
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