Prothena (NASDAQ:PRTA) Stock: Insider William Scully Purchases 125,000 Shares

Posted by Francis Steltz on Oct 9th, 2026

Prothena Corporation plc (NASDAQ:PRTA – Get Free Report) major shareholder William Scully bought 125,000 shares of the stock in a transaction on Wednesday, October 7th. The stock was purchased at an average cost of $8.40 per share, for a total transaction of $1,050,000.00. Following the acquisition, the insider directly owned 439,000 shares of the company’s stock, valued at $3,687,600. The trade was a 39.81% increase in their position. The acquisition was disclosed in a document filed with the SEC, which is available through this hyperlink. Major shareholders that own more than 10% of a company’s shares are required to disclose their transactions with the SEC.

Prothena Stock Performance

NASDAQ PRTA traded up $0.26 during trading hours on Friday, reaching $8.87. The company’s stock had a trading volume of 190,055 shares, compared to its average volume of 508,207. Prothena Corporation plc has a fifty-two week low of $7.73 and a fifty-two week high of $11.80. The stock has a market cap of $464.24 million, a PE ratio of -10.54, a PEG ratio of 2.99 and a beta of -0.29. The company’s 50-day moving average is $8.88 and its two-hundred day moving average is $9.34.

Prothena (NASDAQ:PRTA – Get Free Report) last issued its quarterly earnings results on Thursday, August 6th. The biotechnology company reported ($0.32) EPS for the quarter, topping the consensus estimate 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 firm had revenue of $1.01 million during the quarter, compared to analyst estimates of $0.42 million. Equities analysts expect that Prothena Corporation plc will post 0.08 earnings per share for the current fiscal year.

Hedge Funds Weigh In On Prothena

A number of hedge funds have recently modified their holdings of the stock. Rubric Capital Management LP grew its position in Prothena by 36.0% in the first quarter. Rubric Capital Management LP now owns 5,000,000 shares of the biotechnology company’s stock worth $48,600,000 after acquiring an additional 1,322,669 shares in the last quarter. ADAR1 Capital Management LLC raised its holdings in shares of Prothena by 8.5% during the 1st quarter. ADAR1 Capital Management LLC now owns 1,581,443 shares of the biotechnology company’s stock valued at $15,372,000 after purchasing an additional 123,679 shares in the last quarter. Dimensional Fund Advisors LP lifted its stake in shares of Prothena by 1.0% in the 1st quarter. Dimensional Fund Advisors LP now owns 782,603 shares of the biotechnology company’s stock valued at $7,606,000 after purchasing an additional 7,396 shares during the last quarter. Renaissance Technologies LLC increased its position in Prothena by 39.5% during the first quarter. Renaissance Technologies LLC now owns 607,515 shares of the biotechnology company’s stock worth $5,905,000 after buying an additional 172,000 shares during the last quarter. Finally, Penbrook Management LLC acquired a new position in Prothena during the first quarter worth $2,641,000. 97.08% of the stock is owned by institutional investors and hedge funds.

Wall Street Analysts Forecast Growth

PRTA has been the topic of several analyst reports. UBS Group restated a “buy” rating on shares of Prothena in a research report on Friday, July 24th. HC Wainwright reaffirmed a “buy” rating and set a $30.00 price target on shares of Prothena in a research note on Friday, July 24th. Wall Street Zen lowered Prothena from a “buy” rating to a “hold” rating in a report on Saturday, July 25th. Finally, Weiss Ratings cut shares of Prothena from a “sell (d-)” rating to a “sell (e+)” rating in a research report on Thursday, September 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. Based on data from MarketBeat.com, the company currently has an average rating of “Moderate Buy” and a consensus price target of $24.57.

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About Prothena

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Prothena Corporation plc is a clinical-stage biotechnology company focused on discovering and developing therapies for diseases caused by protein misfolding or abnormal protein accumulation. Its research programs target neurological and systemic disorders, including Alzheimer’s disease, Parkinson’s disease, and transthyretin amyloidosis.

The company’s pipeline has included PRX012, an investigational next-generation antibody targeting amyloid beta for Alzheimer’s disease; prasinezumab, an anti-alpha-synuclein antibody being developed for Parkinson’s disease through a collaboration with Roche; and birtamimab, an investigational treatment designed to target misfolded light chains associated with AL amyloidosis.