Prothena (PRTA) Stock Chart & Stock Price History $9.84 -0.08 (-0.81%) As of 02:46 PM Eastern This is a fair market value 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 41.77%, with a year-to-date return of -29.12%. In the past month, the stock has increased 14.82%, reflecting recent market activity. As of the latest close, Prothena traded at $9.92 with a market cap of $533.99 million and volume of 852,906 shares. Five years ago, the stock traded at $10.93, representing a 10.18% decrease over that period. At the time, it had a market cap of $436.23 million and a volume of 279,664 shares. 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Read our full terms of service and privacy policy. 5 Day Performance-1.04%1 Month Performance+14.82%3 Month Performance+51.73%Year-To-Date Performance-29.12%1 Year Performance-41.77%5 Year Performance-10.18% PRTA Stock Chart for Monday, October, 6, 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 Capitalization10/03/2025$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 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. 09/19/2025$8.18$8.07-1.34%$8.23$8.06910,675 shs$434.41 million09/18/2025$8.06$8.18+1.49%$8.35$8.05459,042 shs$440.33 million09/17/2025$8.16$8.06-1.23%$8.39$8.04507,319 shs$433.87 million09/16/2025$8.16$8.16$8.36$8.12362,452 shs$439.25 million09/15/2025$8.21$8.16-0.61%$8.35$8.10713,676 shs$439.25 million09/12/2025$8.43$8.21-2.61%$8.49$8.20551,060 shs$441.94 million09/11/2025$8.31$8.43+1.44%$8.50$8.19711,834 shs$453.79 million09/10/2025$8.34$8.31-0.36%$8.47$8.20518,523 shs$447.33 million09/09/2025$8.49$8.34-1.77%$8.50$8.10916,153 shs$448.94 million09/08/2025$8.55$8.49-0.70%$8.62$8.30622,009 shs$457.02 million09/05/2025$8.21$8.55+4.14%$8.59$8.211.13 million shs$460.25 million Related Companies ANI Pharmaceuticals Stock Chart Adaptive Biotechnologies Stock Chart Dyne Therapeutics Stock Chart Vera Therapeutics Stock Chart Sarepta Therapeutics Stock Chart Apogee Therapeutics Stock Chart Intellia Therapeutics Stock Chart Harrow Stock Chart Aurinia Pharmaceuticals Stock Chart Immunocore 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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