Prothena (PRTA) Stock Chart & Stock Price History $8.77 +0.21 (+2.45%) Closing price 04:00 PM EasternExtended Trading$8.76 -0.01 (-0.17%) As of 07:44 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 58.73%, with a year-to-date return of -36.68%. In the past month, the stock has increased 34.30%, reflecting recent market activity. As of the latest close, Prothena traded at $8.56 with a market cap of $460.79 million and volume of 854,179 shares. Five years ago, the stock traded at $13.04, representing a 32.75% decrease over that period. At the time, it had a market cap of $493.70 million and a volume of 165,400 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. Email Address 5 Day Performance+6.30%1 Month Performance+34.30%3 Month Performance+33.89%Year-To-Date Performance-36.68%1 Year Performance-58.73%5 Year Performance-32.75% PRTA Stock Chart for Friday, August, 22, 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 Capitalization08/21/2025$8.52$8.56+0.47%$8.57$8.32854,179 shs$460.79 million08/20/2025$8.52$8.52$8.60$8.28639,174 shs$458.63 million08/19/2025$8.53$8.52-0.12%$8.70$8.35827,098 shs$458.63 million08/18/2025$8.25$8.53+3.39%$8.66$8.301.16 million shs$459.17 million08/15/2025$8.06$8.25+2.36%$8.34$8.001.13 million shs$444.10 million08/14/2025$8.05$8.06+0.12%$8.12$7.78590,269 shs$433.33 million08/13/2025$7.54$8.05+6.76%$8.17$7.581.60 million shs$433.33 million08/12/2025$7.67$7.54-1.69%$7.96$7.50906,550 shs$405.88 million08/11/2025$7.69$7.67-0.26%$7.85$7.391.15 million shs$412.88 million08/08/2025$7.72$7.69-0.39%$7.94$7.64921,204 shs$413.95 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. 08/07/2025$7.92$7.72-2.53%$7.98$7.521.09 million shs$415.57 million08/06/2025$7.03$7.92+12.66%$8.01$7.283.11 million shs$426.33 million08/05/2025$6.94$7.03+1.30%$7.54$6.731.57 million shs$378.40 million08/04/2025$6.81$6.94+1.91%$6.99$6.70957,382 shs$373.58 million08/01/2025$6.87$6.81-0.87%$6.87$6.61840,982 shs$366.58 million07/31/2025$6.88$6.87-0.15%$7.23$6.83994,942 shs$369.81 million07/30/2025$6.93$6.88-0.72%$7.33$6.741.24 million shs$370.33 million07/29/2025$6.87$6.93+0.87%$7.10$6.80724,870 shs$373.04 million07/28/2025$6.68$6.87+2.84%$6.89$6.63804,697 shs$369.81 million07/25/2025$6.70$6.68-0.30%$6.86$6.58771,560 shs$359.58 million07/24/2025$6.76$6.70-0.89%$6.76$6.54717,762 shs$360.64 million07/23/2025$6.53$6.76+3.52%$6.94$6.51898,765 shs$363.89 million07/22/2025$6.29$6.53+3.82%$6.59$6.29722,319 shs$351.51 million07/21/2025$6.26$6.29+0.48%$6.52$6.24686,660 shs$338.57 million Related Companies Dyne Therapeutics Stock Chart Apogee Therapeutics Stock Chart Twist Bioscience Stock Chart Travere Therapeutics Stock Chart Biohaven Stock Chart Immunocore Stock Chart Cidara Therapeutics Stock Chart Aurinia Pharmaceuticals Stock Chart WAVE Life Sciences Stock Chart Janux Therapeutics 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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