Prothena (PRTA) 10% Owner William P Scully Buys $819K of Stock
Key Points
- William Scully's recent purchase increased his stake in Prothena Corporation to 1.137 million shares, reflecting a 9.64% rise in his ownership.
- After the trade, William P Scully holds 1,137,000 $PRTA shares, up 9.64% from before the trade.
- The stock closed at $8.25 on the day of the transaction, but recently traded around $8.40, which is about 1.8% higher than the event close.
- Prothena has a market cap of about $421 million and is set to announce its next earnings on November 5, 2026.
Since the trade, $PRTA is up 1.8% to date (from the $8.25 close on Oct 22, 2026).
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William Scully, a 10% owner of Prothena Corporation plc (PRTA), bought 100,000 shares on October 22, 2026, for approximately $818,520. This purchase brings his total holdings to about 1.137 million shares. The information comes from a Form 4 filing with the SEC.
Scully's recent buy represents a 9.64% increase in his ownership. He acquired these shares at an average price of $8.19. The stock closed at $8.25 on the same day, and it has since traded recently around $8.40, which is about 1.8% higher than that closing price.
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
Several other institutional investors hold significant stakes in Prothena. Rubric Capital Management LP maintains 5 million shares valued at about $42 million. Acadian Asset Management LLC increased its holdings by 463,043 shares, bringing its total to about 2.01 million shares worth approximately $16.9 million. Shaw D.E. & Co., Inc. has 1.61 million shares, while Adar1 Capital Management, LLC holds about 1.55 million shares. Two Sigma Investments, LP has 1.26 million shares of Prothena.
Prothena Corporation plc Stock Up 1.8%
Prothena has been trading below both its 50-day moving average of $8.79 and its 200-day average of $9.25. The stock is currently about 28.8% lower than its 52-week high of $11.80 but is above its 52-week low of $7.73 by about 8.7%. The recent trading price of around $8.40 shows some resilience compared to its recent closing prices.
Recent Earnings
Prothena reported trailing twelve-month revenue of $54.53 million, but it has experienced a significant decline in revenue growth, at -77.1%. The company also has a negative net margin of -80.7% and a return on equity of -14.4%. The next earnings report is expected on November 5, 2026.
Insider Buying and Selling at Prothena Corporation plc
In addition to Scully's recent purchase, he also bought 100,000 shares on September 18, 2026, for about $843,460, and 100,000 shares on October 13, 2026, for approximately $835,480. Earlier, on June 16, he purchased 20,000 shares for $158,000. These transactions indicate Scully’s continued confidence in Prothena's future.
Analysts Set New Price Targets
However, the consensus recommendation remains a buy, with a mean price target of $21.40, significantly higher than the current trading levels.
About Prothena Corporation
Prothena Corporation plc is a biotechnology company based in Dublin, Ireland. It focuses on developing therapies for diseases caused by protein dysregulation. Its product pipeline includes Prasinezumab, an investigational treatment for Parkinson's disease and other related conditions.
Bottom Line
Investors should keep an eye on Prothena's upcoming earnings report on November 5, 2026, for insights into its financial health. Scully's continued investment suggests he sees potential in the company's future, despite its current challenges.
Related Filing Alerts
Source: William P Scully's Form 4 filing on $PRTA (Oct 22, 2026). Written by software, not financial advice. How we make alerts