Prothena (PRTA) 10% Owner William P Scully Buys $404K of Stock
Key Points
- William P Scully, a 10% owner of Prothena Corporation, purchased 50,000 shares at an average price of $8.07 on October 23, 2026.
- The stock closed at $8.20 on the same day and recently traded at about $8.40, which is 2.4% above the closing price.
- Scully has increased his stake in Prothena by 4.4% with this recent purchase, now holding a total of 1,187,000 shares.
Since the trade, $PRTA is up 2.4% to date (from the $8.20 close on Oct 23, 2026).
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On October 23, 2026, William P Scully bought 50,000 shares of Prothena Corporation plc (NASDAQ: PRTA) for about $403,525. This purchase increases his total ownership to 1,187,000 shares. The details of the transaction were reported in a Form 4 filing with the SEC.
Scully's recent buy adds to his previous purchases, including a buy of 100,000 shares on September 18 and another 100,000 shares on October 13. His trading activity indicates a growing confidence in Prothena's prospects.
PRTA
Prothena Corporation plc
William P Scully vs. the S&P 500
Hypothetical returns from William P Scully's disclosed trades, not real profit or advice. How we model this.
Other Institutional Activity in Prothena Corporation
Rubric Capital Management LP holds 5,000,000 shares of Prothena, valued at about $42 million. Acadian Asset Management LLC added 463,043 shares, bringing its total to 2,010,645 shares worth about $16.9 million. Meanwhile, Shaw D.E. & Co., Inc. trimmed its stake by 151,818 shares, leaving it with 1,611,457 shares valued at around $13.5 million. Adar1 Capital Management, LLC slightly decreased its holdings by 26,884 shares, now owning 1,554,535 shares worth about $13.1 million. Two Sigma Investments, LP increased its position by 58,974 shares to a total of 1,264,987 shares valued at approximately $10.6 million.
Prothena Corporation plc Stock Up 1.8%
On October 23, 2026, Prothena shares closed at $8.20. The stock has recently traded around $8.40, which is 2.4% above its closing price. However, it remains about 28.8% below its 52-week high of $11.80. The stock is also below its 50-day moving average of $8.79 and its 200-day average of $9.25.
Recent Earnings
For the trailing twelve months, Prothena reported revenue of $54.5 million, but its revenue growth year-over-year has declined by 77.1%. The company is not currently profitable, with an EPS of -$0.82. The next earnings report is scheduled for November 5, 2026.
Insider Buying and Selling at Prothena Corporation plc
William P Scully has been active in buying shares of Prothena. Earlier this year, he purchased 20,000 shares on June 16 for $158,000 and followed that with multiple purchases in September and October, including 100,000 shares for $843,460 on September 18 and another 100,000 shares on October 13 for $835,480. His most recent purchase of 50,000 shares on October 23 further solidifies his position as a significant shareholder in the company.
Analysts Set New Price Targets
The average target price among analysts who cover the stock is $21.40, indicating a potential upside from its recent trading levels.
About Prothena Corporation
Prothena Corporation plc is a biotechnology company based in Dublin, Ireland. It focuses on developing therapies for diseases related to protein dysregulation. Its notable product in development is Prasinezumab, aimed at treating Parkinson's disease and other related conditions.
Bottom Line
William P Scully's recent purchase of Prothena shares reflects his confidence in the company's future. Investors should watch for the upcoming earnings report on November 5, 2026, for further insights into Prothena's performance.
Related Filing Alerts
Source: William P Scully's Form 4 filing on $PRTA (Oct 23, 2026). Written by software, not financial advice. How we make alerts