Prothena (PRTA) 10% Owner Scully William P Buys $85K of Stock

William Scully, a beneficial owner of more than 10% of Prothena Corporation plc (NasdaqGS: PRTA), bought 10,000 shares on October 14, 2026, for $8.46 each. This purchase is valued at about $84,569.

Inside Scully's Trade

Scully's recent buy adds to his significant stake in Prothena, which he has been increasing steadily over the past month. This transaction follows his previous purchases, including a buy of 100,000 shares for $835,480 just a day earlier on October 13, 2026. His commitment to Prothena indicates confidence in the company's future amid current market conditions.

Other Institutional Activity in Prothena

Several other institutional investors have also adjusted their positions in Prothena. FMR, LLC reduced its holdings by 351,881 shares, bringing its total to 7,199,218 shares worth about $60.1 million. Meanwhile, Blackrock Inc. added 223,846 shares, increasing its stake to 4,867,955 shares valued at approximately $40.6 million. State Street Corporation grew its holdings by 454,958 shares, ending with 2,393,424 shares valued at about $19.9 million. Acadian Asset Management also increased its position by 463,043 shares, totaling 2,010,645 shares worth about $16.8 million.

Prothena Corporation plc Stock Down 0.1%

As of October 16, 2026, Prothena's shares are trading around $8.49, which is below its 50-day moving average of $8.87 and 28.1% under its 52-week high of $11.80. The stock is also trading significantly below its mean price target of $21.40, indicating a challenging market position for the company.

Recent Earnings

Prothena reported trailing twelve-month revenue of $54.53 million, with a net margin of -80.7%. The company has a next earnings report scheduled for November 5, 2026. Investors will be watching closely to see if there is any improvement in revenue growth, which has seen a decline of 77.1% year-over-year.

Insider Buying and Selling at Prothena Corporation plc

William Scully has been actively buying shares in Prothena. Prior to his latest purchase, he bought 100,000 shares on October 2, 2026, for $857,240, and he made additional purchases of 162,000 shares at $8.68 each and 103,500 shares at $8.60 each on September 29 and 28, 2026, respectively. His consistent buying suggests a strong belief in the company's potential despite its current struggles.

About Prothena Corporation

Prothena Corporation plc is a biotechnology company based in Dublin, Ireland, focusing on developing therapies for diseases caused by protein dysregulation. Its lead product, Prasinezumab, is in a Phase 3 clinical trial aimed at treating Parkinson's disease. With a small team of 67 employees, Prothena is navigating a challenging biotech landscape but remains focused on its innovative pipeline.

Bottom Line

Scully's recent share purchase shows continued confidence in Prothena, especially as the company prepares for its earnings report on November 5, 2026. Investors will be keen to see if the company can turn its financial performance around amidst a tough market environment.