NASDAQ:PRTA Prothena (PRTA) Stock Price, News & Analysis $9.83 0.00 (0.00%) Closing price 05/22/2026 04:00 PM EasternExtended Trading$9.57 -0.26 (-2.63%) As of 05/22/2026 04:17 PM Eastern Extended trading is trading that happens on electronic markets outside of regular trading hours. This is a fair market value extended hours price provided by Massive. Learn more. Add Compare Share Share Stock Analysis Stock AnalysisAnalyst ForecastsChartCompetitorsEarningsFDA EventsFinancialsHeadlinesInsider TradesOptions ChainOwnershipSEC FilingsShort InterestTrendsBuy This Stock About Prothena Stock (NASDAQ:PRTA) View Price History Chart DataSkip Price History Chart 1 Day 5 Days 30 Days 90 Days 1 Year Advanced 1 Day 1 Day 5 Days 30 Days 90 Days 1 Year Advanced Show volume Show extended hours Get Prothena alerts:Sign Up Key Stats Today's Range$9.36▼$10.0050-Day Range$8.54▼$11.5152-Week Range$4.32▼$11.80Volume510,854 shsAverage Volume507,699 shsMarket Capitalization$514.60 millionP/E RatioN/ADividend YieldN/APrice Target$21.78Consensus RatingHold Company Overview Prothena Corporation plc is a clinical-stage biotechnology company dedicated to the discovery and development of novel therapies for neurodegenerative and rare diseases driven by misfolded proteins. The company’s research focuses on immunotherapies and small molecules designed to target and clear disease-causing protein aggregates. Prothena leverages proprietary protein engineering and antibody discovery platforms to advance candidates through preclinical and clinical stages. The company’s most advanced program is an antibody targeting aggregated alpha-synuclein for the potential treatment of Parkinson’s disease, currently in mid-stage clinical trials. Additional pipeline candidates include therapies for amyloid light chain (AL) amyloidosis and other protein misfolding disorders. Prothena collaborates with global pharmaceutical partners to further develop and commercialize its product candidates, pooling resources and expertise to accelerate research timelines. Founded in 2012 as a spin-out from Elan Corporation, Prothena is headquartered in South San Francisco, California, with research operations in both the United States and Ireland. The company maintains a global focus, engaging regulators and trial sites across North America, Europe and Asia to support its clinical development programs. Prothena’s commitment to addressing high-unmet-need diseases is reflected in its strategic partnerships and research investments. Prothena is led by President and Chief Executive Officer Gene Kinney, whose experience spans decades in the pharmaceutical and biotechnology sectors. Under his leadership, the company has built a multidisciplinary team of scientists, clinicians and commercial experts. Prothena’s board and management team bring deep expertise in protein science, immunology and drug development to guide the company’s mission of bringing new treatment options to patients worldwide. AI Generated. May Contain Errors. Read More Prothena Stock Analysis - MarketRank™See Top-Rated MarketRank™ Stocks33rd Percentile Overall ScorePRTA MarketRank™: Prothena scored higher than 33% of companies evaluated by MarketBeat, and ranked 728th out of 869 stocks in the medical sector. Scores are calculated by averaging available category scores, with extra weight given to analysis and valuation. Analyst's Opinion3.8 / 5Analyst RatingHold Consensus RatingProthena has received a consensus rating of Hold. The company's average rating score is 2.36, and is based on 1 strong buy rating, 4 buy ratings, 4 hold ratings, and 2 sell ratings.Upside PotentialProthena has a consensus price target of $21.78, representing about 121.5% upside from its current price of $9.83.Amount of Analyst CoverageProthena has only been the subject of 3 research reports in the past 90 days.Read more about Prothena's stock forecast and price target. Earnings and Valuation0.0 / 5Proj. Earnings GrowthDecreasing Earnings GrowthEarnings for Prothena are expected to decrease in the coming year, from $0.18 to ($1.13) per share.Price to Earnings Ratio vs. the MarketThe P/E ratio of Prothena is -3.49, which means that its earnings are negative and its P/E ratio cannot be compared to companies with positive earnings.Price to Earnings Ratio vs. SectorThe P/E ratio of Prothena is -3.49, which means that its earnings are negative and its P/E ratio cannot be compared to companies with positive earnings.Price to Earnings Growth RatioProthena has a PEG Ratio of 1.57. PEG Ratios above 1 indicate that a company could be overvalued.Price to Book Value per Share RatioProthena has a P/B Ratio of 1.65. P/B Ratios below 3 indicates that a company is reasonably valued with respect to its assets and liabilities.Read more about Prothena's valuation and earnings. Short Interest1.0 / 5Short Interest LevelBearish Percentage of Shares Shorted14.65% of the float of Prothena has been sold short.Short Interest Ratio / Days to CoverProthena has a short interest ratio ("days to cover") of 18.33, which indicates bearish sentiment.Change versus previous monthShort interest in Prothena has recently decreased by 2.90%, indicating that investor sentiment is improving. Dividend0.0 / 5Dividend StrengthN/A Dividend YieldProthena does not currently pay a dividend.Dividend GrowthProthena does not have a long track record of dividend growth. News and Social Media0.6 / 5News SentimentN/A News Coverage This WeekMarketBeat has tracked 1 news article for Prothena this week, compared to 2 articles on an average week.Search Interest2 people have searched for PRTA on MarketBeat in the last 30 days. This is an increase of 100% compared to the previous 30 days. Company Ownership1.1 / 5Insider TradingN/A Insider Buying vs. Insider SellingIn the past three months, Prothena insiders have not sold or bought any company stock.Percentage Held by Insiders10.40% of the stock of Prothena is held by insiders. A high percentage of insider ownership can be a sign of company health.Percentage Held by Institutions97.08% of the stock of Prothena is held by institutions. High institutional ownership can be a signal of strong market trust in this company.Read more about Prothena's insider trading history. Receive PRTA Stock News and Ratings via Email Sign-up to receive the latest news and ratings for Prothena and its competitors with MarketBeat's FREE daily newsletter. Submit View SMS TermsSMS is currently available in Australia, Belgium, Canada, France, Germany, Ireland, Italy, New Zealand, the Netherlands, Singapore, South Africa, Spain, Switzerland, the United Kingdom, and the United States. 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PlcMay 19, 2026 | edition.cnn.comProthena Corporation plc (NASDAQ:PRTA) Given Consensus Recommendation of "Hold" by BrokeragesMay 16, 2026 | americanbankingnews.com$30 stock to buy before Starlink goes public (WATCH NOW!)In the next 3 minutes… James Altucher – legendary investor and venture capitalist… And someone who’s known for playing his cards “close to the vest”… Is going to give you the name and ticker symbol of a company he believes will skyrocket thanks to the coming Starlink IPO…May 25 at 1:00 AM | Paradigm Press (Ad)Piper Sandler Sticks to Its Buy Rating for Prothena (PRTA)May 14, 2026 | theglobeandmail.comProthena (PRTA) Gets a Hold from RBC CapitalMay 14, 2026 | theglobeandmail.comEarnings Beat: Prothena Corporation plc Just Beat Analyst Forecasts, And Analysts Have Been Updating Their ModelsMay 12, 2026 | finance.yahoo.comProthena Reports First Quarter 2026 Financial Results and Business HighlightsMay 7, 2026 | businesswire.comProthena to Report First Quarter 2026 Financial Results on May 7April 30, 2026 | businesswire.comSee More Headlines PRTA Stock Analysis - Frequently Asked Questions How have PRTA shares performed this year? Prothena's stock was trading at $9.55 at the beginning of 2026. Since then, PRTA shares have increased by 2.9% and is now trading at $9.83. How were Prothena's earnings last quarter? Prothena Corporation plc (NASDAQ:PRTA) posted its earnings results on Thursday, May, 7th. The biotechnology company reported $0.60 earnings per share for the quarter, beating analysts' consensus estimates of ($0.31) by $0.91. The biotechnology company earned $51.08 million during the quarter, compared to analyst estimates of $0.81 million. Prothena had a negative net margin of 260.92% and a negative trailing twelve-month return on equity of 43.44%. Who are Prothena's major shareholders? Prothena's top institutional shareholders include Rubric Capital Management LP (9.55%), ADAR1 Capital Management LLC (3.02%), Dimensional Fund Advisors LP (1.45%) and Renaissance Technologies LLC (1.16%). Insiders that own company stock include William P Scully, Dennis J Selkoe, Carol D Karp, Brandon S Smith, Wagner M Zago, Michael J Malecek, Karin L Walker and Hideki Garren. View institutional ownership trends. How do I buy shares of Prothena? Shares of PRTA stock can be purchased through any online brokerage account. Popular online brokerages with access to the U.S. stock market include Charles Schwab, E*TRADE, Fidelity, and Vanguard Brokerage Services. What other stocks do shareholders of Prothena own? Based on aggregate information from My MarketBeat watchlists, some other companies that Prothena investors own include Voyager Therapeutics (VYGR), American Water Works (AWK), Humana (HUM), Waste Connections (WCN), The RMR Group (RMR), DiamondRock Hospitality (DRH) and AUO (AUOTY). Company Calendar Last Earnings5/07/2026Today5/25/2026Next Earnings (Estimated)8/03/2026Fiscal Year End12/31/2026Get Stock Alerts Health Indicator TradeSmith's Health IndicatorA long-term volatility-based measure designed for securities held 12 months or longer.Green: Strong and healthy uptrend with normal pullbacks.Yellow: Significant pullback but still within expected volatility.Red: Dropped beyond expected volatility; considered unhealthy. Green Zone (9m+) 1-Year History May 25 Aug 25 Nov 25 Feb 26 May 26 PRTA's financial health is in the Green zone, according to TradeSmith. PRTA has been in this zone for over 9 months. Industry, Sector and Symbol Stock ExchangeNASDAQ SectorMedical Industry MED - BIOMED/GENE Sub-IndustryPharmaceutical Products Current SymbolNASDAQ:PRTA CIK1559053 Webwww.prothena.com Phone(531) 236-2500Fax353-1902-3510Employees130Year Founded2012Price Target and Rating Average Price Target for Prothena$21.78 High Price Target$36.00 Low Price Target$6.00 Potential Upside/Downside+121.5%Consensus RatingHold Rating Score (0-4)2.36 Research Coverage11 Analysts Profitability EPS (Trailing Twelve Months)($2.82) Trailing P/E RatioN/A Forward P/E Ratio54.61 P/E Growth1.57Net Income-$244.09 million Net Margins-260.92% Pretax Margin-184.21% Return on Equity-43.44% Return on Assets-36.87% Debt Debt-to-Equity RatioN/A Current Ratio10.43 Quick Ratio10.43 Sales & Book Value Annual Sales$9.68 million Price / Sales53.16 Cash FlowN/A Price / Cash FlowN/A Book Value$5.97 per share Price / Book1.65Miscellaneous Outstanding Shares52,350,000Free Float46,908,000Market Cap$514.60 million OptionableOptionable Beta-0.23 Social Links Reduce the RiskMarket downturns give many investors pause, and for good reason. Wondering how to offset this risk? Click the link to learn more about using beta to protect your portfolio.Get This Free Report This page (NASDAQ:PRTA) was last updated on 5/25/2026 by MarketBeat.com Staff. 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