Prothena (PRTA)
Develops investigational protein-dysregulation therapies with a partner-heavy clinical pipeline.
$8.69
vs last close−0.30 (−3.29%)
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13F · 13D/G · Form 4
| Institutions | 92.75% | 47.62M shares | |
|---|---|---|---|
| 197 holders · as of Jun 30, 2026 | |||
| Insiders | 20.43% | 10.49M shares | |
| 11 holders · as of Sep 21, 2026 | |||
| Strategic holders | 10.33% | 5.30M shares | |
| 1 holder · as of May 6, 2025 | |||
| Adds to | 123.51% | ||
51.34M company shares as of Sep 23, 2026 · institutions as of Jun 30, 2026 · holders as of their latest filing
These groups come from separate filings that can overlap, so they add to 123.51%; nothing is left for Other.
13F, as of Jun 30, 2026
197 holders · 47.62M shares · 31 new positions · 89 increased · 58 reduced · 24 closed
| Holder | Shares | % outstanding | Chg q/q | Filed |
|---|---|---|---|---|
| FMR LLC | 7.20M | 14.02% | −352.0K | Aug 13, 2026 |
| Rubric Capital Management LP | 5.00M | 9.74% | 0 | Aug 14, 2026 |
| BlackRock, Inc. | 4.87M | 9.48% | +223.8K | Aug 7, 2026 |
| State Street Corp | 2.39M | 4.66% | +454.9K | Aug 7, 2026 |
| Acadian Asset Management LLC | 2.01M | 3.92% | +463.1K | Aug 13, 2026 |
| Vanguard Portfolio Management LLC | 1.65M | 3.22% | +205.3K | Aug 13, 2026 |
| D. E. Shaw & Co., Inc. | 1.61M | 3.14% | −151.9K | Aug 14, 2026 |
| Adar1 Capital Management, LLC | 1.55M | 3.03% | −26.9K | Aug 14, 2026 |
13D/G · 5% or more, as filed
| Holder | % of class | Shares | Form | Filed |
|---|---|---|---|---|
| Scully William P | 10.30% | 5.38M | 13G | May 11, 2026 |
| Rubric Capital Management LP | 9.29% | 5.00M | 13G | May 15, 2026 |
| Fennell Todd W. | 8.40% | 4.50M | 13G | Nov 12, 2025 |
| BlackRock, Inc. | 5.70% | 3.09M | 13G | Oct 17, 2025 |
Form 4
Latest trades
| Date | Insider | Type | Shares | Avg price | Owned after |
|---|---|---|---|---|---|
| Sep 18, 2026 | William P. Scully10 percent owner | Purchase | 100,000 | $8.43 | 927,000 |
| Sep 2, 2026 | William P. Scully10 percent owner | Purchase | 27,000 | $9.47 | 827,000 |
| Aug 20, 2026 | William P. Scully10 percent owner | Purchase | 50,000 | $8.79 | 800,000 |
| Aug 7, 2026 | William P. Scully10 percent owner | Purchase · 2 lots | 37,500 | $8.62 | 873,500 |
| Jul 29, 2026 | Michael John Isaacsofficer: General Counsel & Company Sec. | Sale | 8,386 | $8.47 | 35,745 |
| Jul 29, 2026 | Anne Evans Kingstonofficer: Chief Strategy Officer | Sale | 7,662 | $8.47 | 55,782 |
| Jun 16, 2026 | William P. Scully10 percent owner | Purchase | 20,000 | $7.90 | 756,000 |
| Jun 11, 2026 | William P. Scully10 percent owner | Purchase | 125,000 | $8.17 | 1,061,000 |
| Jun 4, 2026 | William P. Scully10 percent owner | Purchase | 50,000 | $9.31 | 936,000 |
| Jun 2, 2026 | William P. Scully10 percent owner | Purchase | 50,000 | $9.43 | 886,000 |
House and Senate disclosures
Not reported.