Prothena (NASDAQ:PRTA) Stock: Insider William Scully Purchases 100,000 Shares

Posted by Brenda Bartman on Oct 26th, 2026

Prothena Corporation plc (NASDAQ:PRTA – Get Free Report) major shareholder William Scully bought 100,000 shares of the stock in a transaction dated Thursday, October 22nd. The stock was purchased at an average price of $8.19 per share, with a total value of $819,000.00. Following the acquisition, the insider directly owned 1,137,000 shares in the company, valued at approximately $9,312,030. The trade was a 9.64% increase in their position. The transaction was disclosed in a document filed with the Securities & Exchange Commission, which is available through the SEC website. Major shareholders that own at least 10% of a company’s stock are required to disclose their sales and purchases with the SEC.

Prothena Trading Up 2.4%

Shares of PRTA stock traded up $0.20 during trading hours on Monday, reaching $8.40. 594,544 shares of the stock were exchanged, compared to its average volume of 511,111. The firm has a market capitalization of $439.74 million, a price-to-earnings ratio of -10.00, a price-to-earnings-growth ratio of 2.89 and a beta of -0.29. Prothena Corporation plc has a 12-month low of $7.73 and a 12-month high of $11.80. The company’s 50-day moving average price is $8.80 and its 200-day moving average price is $9.25.

Prothena (NASDAQ:PRTA – Get Free Report) last posted its quarterly earnings data on Thursday, August 6th. The biotechnology company reported ($0.32) earnings per share for the quarter, topping analysts’ consensus estimates of ($0.39) by $0.07. Prothena had a negative net margin of 80.68% and a negative return on equity of 16.45%. The company had revenue of $1.01 million for the quarter, compared to analyst estimates of $0.42 million. On average, sell-side analysts expect that Prothena Corporation plc will post 0.08 EPS for the current year.

Analyst Upgrades and Downgrades

A number of research analysts have recently commented on PRTA shares. Wall Street Zen cut Prothena from a “buy” rating to a “hold” rating in a research note on Saturday, July 25th. UBS Group reissued a “buy” rating on shares of Prothena in a research note on Friday, July 24th. Weiss Ratings upgraded Prothena from a “sell (e+)” rating to a “sell (d-)” rating in a report on Wednesday, October 14th. Finally, HC Wainwright reaffirmed a “buy” rating and issued a $30.00 price objective on shares of Prothena in a research report on Friday, July 24th. One research analyst has rated the stock with a Strong Buy rating, five have assigned a Buy rating, one has issued a Hold rating and one has assigned a Sell rating to the company. According to MarketBeat, the company presently has an average rating of “Moderate Buy” and an average target price of $24.57.

Read Our Latest Report on PRTA

Institutional Trading of Prothena

Several institutional investors and hedge funds have recently modified their holdings of the stock. Versant Capital Management Inc boosted its holdings in shares of Prothena by 179.1% in the third quarter. Versant Capital Management Inc now owns 5,704 shares of the biotechnology company’s stock valued at $48,000 after purchasing an additional 3,660 shares during the period. CHICAGO TRUST Co NA bought a new position in Prothena in the first quarter worth approximately $146,000. Headlands Technologies LLC purchased a new position in Prothena during the 2nd quarter worth $148,000. Sei Investments Co. purchased a new position in Prothena during the 1st quarter worth $168,000. Finally, Great Lakes Advisors LLC purchased a new position in Prothena during the 2nd quarter worth $281,000. Institutional investors own 97.08% of the company’s stock.

About Prothena

(Get Free Report)

Prothena Corporation plc (NASDAQ: PRTA) is a clinical-stage biotechnology company focused on discovering and developing novel medicines for serious neurodegenerative and rare peripheral diseases. Its research is centered on disease-causing proteins, including amyloid-beta, alpha-synuclein and transthyretin, with the goal of creating antibody-based therapies that address underlying disease mechanisms.

The company’s product pipeline has included birtamimab, an investigational antibody being developed for the treatment of AL amyloidosis, and prasinezumab, an investigational alpha-synuclein antibody being developed in collaboration with Roche for certain forms of Parkinson’s disease.