Prothena (PRTA) Stock Chart & Stock Price History $10.22 -0.15 (-1.45%) Closing price 04:00 PM EasternExtended Trading$9.95 -0.27 (-2.63%) As of 07:54 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 Polygon.io. Learn more. Add Compare Share Share Chart Stock AnalysisAnalyst ForecastsChartCompetitorsEarningsFDA EventsFinancialsHeadlinesInsider TradesOptions ChainOwnershipSEC FilingsShort InterestTrendsBuy This Stock Prothena Stock Price Performance The Prothena (PRTA) stock chart highlights key performance trends across multiple timeframes. Over the last 12 months, the stock's price has decreased 38.06%, with a year-to-date return of -26.21%. In the past month, the stock has increased 26.64%, reflecting recent market activity. As of the latest close, Prothena traded at $10.37 with a market cap of $558.22 million and volume of 558,918 shares. Five years ago, the stock traded at $11.95, representing a 14.48% decrease over that period. At the time, it had a market cap of $476.94 million and a volume of 814,741 shares. Receive PRTA Stock News and Ratings via EmailSign-up to receive the latest news and ratings for Prothena and its competitors with MarketBeat's FREE daily newsletter. Subscribe Now View SMS TermsBy entering your phone number and clicking the sign-up button, you agree to receive periodic text messages from MarketBeat at the phone number you submitted, including texts that may be sent using an automatic telephone dialing system. Message and data rates may apply. Message frequency will vary. Messages will consist of stock alerts, news stories, and partner advertisements/offers. Consent is not a condition of the purchase of any goods or services. Text HELP for help/customer support. 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Read our full terms of service and privacy policy. 5 Day Performance+1.29%1 Month Performance+26.64%3 Month Performance+62.48%Year-To-Date Performance-26.21%1 Year Performance-38.06%5 Year Performance-14.48% PRTA Stock Chart for Tuesday, October, 21, 2025 PRTA Chart by TradingView Prothena Stock Price History Daily Weekly Monthly Yearly Time Frame Custom Range 1 Month 3 Months 6 Months Year-to-Date 1 Year 3 Year 5 Year Time Frame Start Date End Date Export to Excel DateOpening PriceClosing PriceHighLowVolumeMarket Capitalization10/21/2025$10.37$10.22-1.45%$10.61$10.18289,798 shs$550.14 million10/20/2025$9.92$10.37+4.54%$10.55$9.96558,918 shs$558.22 million10/17/2025$10.09$9.92-1.68%$10.23$9.61777,040 shs$533.99 million10/16/2025$10.66$10.09-5.35%$10.90$10.03624,810 shs$543.15 million10/15/2025$10.12$10.66+5.34%$10.72$10.12801,906 shs$573.83 million10/14/2025$10.35$10.12-2.22%$10.32$10.03392,072 shs$544.76 million10/13/2025$10.05$10.35+2.99%$10.35$10.00703,153 shs$557.14 million10/10/2025$10.30$10.05-2.43%$10.45$9.98734,065 shs$540.99 million10/09/2025$10.35$10.30-0.48%$10.65$10.28801,307 shs$554.45 million10/08/2025$10.17$10.35+1.77%$10.54$10.13650,918 shs$557.14 million Get the Latest News and Ratings for PRTA and Related StocksEnter your email address below to receive the latest news and analysts' ratings for Prothena and its competitors with MarketBeat's FREE daily newsletter. 10/07/2025$9.86$10.17+3.14%$10.37$9.921.03 million shs$547.45 million10/06/2025$9.92$9.86-0.60%$10.09$9.77343,437 shs$530.76 million10/03/2025$9.99$9.92-0.70%$10.16$9.58852,906 shs$533.99 million10/02/2025$9.92$9.99+0.71%$10.22$9.85766,735 shs$537.76 million10/01/2025$9.76$9.92+1.64%$10.46$9.78959,026 shs$533.99 million09/30/2025$9.76$9.76$9.85$9.50989,121 shs$525.38 million09/29/2025$9.41$9.76+3.72%$9.82$9.21946,500 shs$525.38 million09/26/2025$9.36$9.41+0.53%$9.46$9.02714,956 shs$506.54 million09/25/2025$9.32$9.36+0.43%$9.56$9.041.57 million shs$503.85 million09/24/2025$8.31$9.32+12.15%$9.34$8.301.12 million shs$501.70 million09/23/2025$8.29$8.31+0.24%$8.35$8.14404,695 shs$447.33 million09/22/2025$8.07$8.29+2.73%$8.43$8.02511,942 shs$446.25 million Related Companies Sarepta Therapeutics Stock Chart Ocular Therapeutix Stock Chart Dyne Therapeutics Stock Chart ANI Pharmaceuticals Stock Chart Vera Therapeutics Stock Chart Tilray Brands Stock Chart Twist Bioscience Stock Chart Cogent Biosciences Stock Chart Structure Therapeutics Stock Chart Biohaven Stock Chart Receive PRTA Stock News and Ratings via EmailSign-up to receive the latest news and ratings for Prothena and its competitors with MarketBeat's FREE daily newsletter. 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