Summary
Updated Aug 31, 2026
William P. Scully is 10% Owner of PROTHENA CORP PUBLIC LTD CO (PRTA). 11 SEC Form 4 filings on record going back to 2025, most recently on 21 August 2026. Most recent open-market trade: bought $439K of PRTA on 21 August 2026. Lifetime open-market purchases: $6.61M. Historical track record: 3/5 stars across 7 tracked purchases.
Recent Transactions
20Every recent SEC Form 4 transaction William P. Scully has reported, most recent first.
Track Record
InsiderAlpha computes a forward-return-based score for every insider with enough Form 4 purchase history. The metrics below reflect realized performance after each tracked open-market purchase.
| Metric | Value |
|---|---|
| InsiderAlpha rating | ★★★☆☆ (3/5) |
| Total purchases tracked | 7 |
| Purchases with forward-return data | 7 |
| 30-day win rate | 71% |
| 90-day win rate | 14% |
| Avg 5-day return | +4.28% |
| Avg 30-day return | +4.15% |
| Avg 90-day return | -9.96% |
| Best 30-day return | +15.23% |
Trading Pattern
InsiderAlpha's records for William P. Scully go back to 2025: 11 primary Form 4 filings, an average of 5.5 per year. The typical open-market purchase is $472K (14 buys totaling $6.61M). The largest single buy on record is $1.28M of PRTA in 2025. No transaction on record carries a Rule 10b5-1 flag - the filings look discretionary rather than pre-scheduled, which makes their timing more informative as a signal.
Other Insiders Active in the Same Stocks
Insiders who reported open-market trades in the last 12 months at the companies William P. Scully files at. Multiple unrelated insiders buying the same stock within a short window, cluster buying, has historically been one of the strongest Form 4 signals.
- Michael John Isaacs - $71K of PRTA open-market activity in the last 12 months
- Anne Evans Kingston - $65K of PRTA open-market activity in the last 12 months
More Notable Insiders
Other corporate insiders with significant SEC Form 4 track records on InsiderAlpha:
Frequently Asked Questions
Who is William P. Scully?
William P. Scully is a corporate insider, tracked as 10% Owner of PROTHENA CORP PUBLIC LTD CO (PRTA). InsiderAlpha holds 11 primary Form 4 filings for them, the earliest from 2025, updated as new SEC EDGAR filings are processed.
How many SEC Form 4 filings has William P. Scully submitted recently?
9 primary Form 4 filings in the last 90 days, covering 1 company.
Has William P. Scully been buying or selling stock?
Recorded transactions: 14 open-market purchases ($6.61M) and 0 open-market sales across all tracked filings.
How accurate is William P. Scully's historical track record?
Across 7 tracked purchases, William P. Scully averaged +4.2% avg 30-day return with a 71% 30-day win rate. InsiderAlpha rates the track record at 3/5 stars.
Where can I see all of William P. Scully's SEC filings?
All Form 4 filings, transaction values, and 10b5-1 plan flags are listed on this page and updated in real time as new SEC EDGAR filings are processed.
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