Prothena (PRTA) Short Interest Ratio & Short Volume $6.55 -0.27 (-3.96%) Closing price 04:00 PM EasternExtended Trading$6.81 +0.26 (+3.97%) As of 07:07 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 Short Interest Stock AnalysisAnalyst ForecastsChartCompetitorsEarningsFinancialsHeadlinesInsider TradesOptions ChainOwnershipSEC FilingsShort InterestTrendsBuy This Stock Prothena Short Interest DataProthena (PRTA) has a short interest of 7.45 million shares. This marks a -5.93% decrease in short interest from the previous month. The short interest ratio (days to cover) is 9.9, indicating that it would take 9.9 days of the average trading volume of 596,198 shares to cover all short positions.Current Short Interest7,450,000 sharesPrevious Short Interest7,920,000 sharesChange Vs. Previous Month-5.93%Dollar Volume Sold Short$68.54 millionShort Interest Ratio9.9 Days to CoverLast Record DateApril 30, 2025Outstanding Shares53,827,000 sharesPercentage of Shares Shorted13.84%Today's Trading Volume933,156 sharesAverage Trading Volume596,198 sharesToday's Volume Vs. Average157% Short Selling Prothena? Sign up to receive the latest short interest report for Prothena and its competitors with MarketBeat's FREE newsletter. Email Address Skip Charts & View Short Interest HistoryShort Interest ChartDays to Cover ChartShort Percent of Float ChartPRTA Short Interest Over TimePRTA Days to Cover Over TimePRTA Percentage of Float Shorted Over Time Prothena Short Interest History Export to ExcelReport DateTotal Shares Sold ShortDollar Volume Sold ShortChange from Previous ReportPercentage of Float ShortedDays to CoverPrice on Report Date 4/30/20257,450,000 shares $68.54 million -5.9%N/A9.9 $9.20 4/15/20257,920,000 shares $75.95 million -5.5%18.6%17 $9.59 3/31/20258,380,000 shares $103.74 million -4.6%19.7%18.7 $12.38 3/15/20258,780,000 shares $120.64 million -3.8%20.7%17.9 $13.74 2/28/20259,130,000 shares $144.35 million +1.1%21.5%18.2 $15.81 2/15/20259,030,000 shares $127.96 million +1.5%21.3%18 $14.17 1/31/20258,900,000 shares $126.65 million -4.8%N/A17.2 $14.23 1/15/20259,350,000 shares $124.07 million +6.6%N/A17 $13.27 12/31/20248,770,000 shares $121.46 million -0.3%N/A15.8 $13.85 12/15/20248,800,000 shares $112.55 million +9.2%N/A14.4 $12.79 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. 11/30/20248,060,000 shares $130.65 million +2.3%N/A15.3 $16.21 11/15/20247,880,000 shares $110.40 million +4.7%N/A15.9 $14.01 10/31/20247,530,000 shares $128.01 million +10.9%N/A16.3 $17.00 10/15/20246,790,000 shares $114.89 million +28.1%N/A15.3 $16.92 9/30/20245,300,000 shares $88.67 million -7.3%N/A11.5 $16.73 9/15/20245,720,000 shares $126.47 million +2.3%N/A14.9 $22.11 8/31/20245,590,000 shares $124.49 million +3.9%N/A12.8 $22.27 8/15/20245,380,000 shares $112.28 million No ChangeN/A11.4 $20.87 7/31/20245,380,000 shares $125.25 million +12.8%N/A10.7 $23.28 7/15/20244,770,000 shares $107.75 million -6.5%N/A9.1 $22.59 6/30/20245,100,000 shares $105.26 million -23.4%N/A9.7 $20.64 6/15/20246,660,000 shares $135.93 million -0.8%N/A12.2 $20.41 5/31/20246,710,000 shares $139.64 million +3.1%N/A12.6 $20.81 5/15/20246,510,000 shares $145.76 million -3.6%N/A11.9 $22.39 4/30/20246,750,000 shares $137.30 million +1.8%N/A11.1 $20.34 4/15/20246,630,000 shares $145.79 million +2.5%N/A10.1 $21.99 3/31/20246,470,000 shares $160.26 million +3.5%N/A8.1 $24.77 3/15/20246,250,000 shares $162.94 million +3.0%N/A7.6 $26.07 2/29/20246,070,000 shares $167.47 million +4.5%N/A7 $27.59 2/15/20245,810,000 shares $165.70 million +1.0%N/A6.6 $28.52 1/31/20245,750,000 shares $163.24 million -8.2%N/A6.8 $28.39 1/15/20246,260,000 shares $217.03 million +3.0%N/A7 $34.67 12/31/20236,080,000 shares $220.95 million +4.5%N/A6.8 $36.34 12/15/20235,820,000 shares $232.74 million -15.0%N/A7.6 $39.99 11/30/20236,850,000 shares $223.17 million +10.7%N/A10.1 $32.58 11/15/20236,190,000 shares $217.15 million -4.8%N/A9.6 $35.08 10/31/20236,500,000 shares $236.99 million +28.0%N/A10.6 $36.46 10/15/20235,080,000 shares $223.93 million +15.7%N/A10.4 $44.08 9/30/20234,390,000 shares $211.82 million +2.6%N/A10.7 $48.25 9/15/20234,280,000 shares $224.53 million +3.9%N/A11.2 $52.46Now I look stupid. Real stupid... (Ad)I thought what happened 25 years ago was a once- in-a-lifetime event… but how wrong I was. Because here we are, a quarter of a century later, almost to the exact day, and it’s happening again. Here’s the full story for you. 8/31/20234,120,000 shares $217.62 million +11.4%N/A10.6 $52.82 8/15/20233,700,000 shares $223.33 million +0.8%N/A9.4 $60.36 7/31/20233,670,000 shares $252.75 million +0.8%N/A9 $68.87 7/15/20233,640,000 shares $254.84 million +3.4%N/A8.3 $70.01 6/30/20233,520,000 shares $240.35 million -4.4%N/A7.9 $68.28 6/15/20233,680,000 shares $267.06 million +10.8%N/A7.8 $72.57 5/31/20233,320,000 shares $220.55 million +3.4%N/A7.1 $66.43 5/15/20233,210,000 shares $240.65 million -1.8%N/A6.7 $74.97 4/30/20233,270,000 shares $172.07 million No ChangeN/A6.9 $52.62 4/15/20233,270,000 shares $164.91 million -11.9%N/A7.5 $50.43 3/31/20233,710,000 shares $179.82 million +7.5%N/A8.3 $48.47 3/15/20233,450,000 shares $169.15 million +11.7%N/A6.9 $49.03 2/28/20233,090,000 shares $172.30 million +4.4%N/A5.9 $55.76 2/15/20232,960,000 shares $159.60 million +6.5%N/A5.6 $53.92 1/31/20232,780,000 shares $157.21 million -3.5%N/A5 $56.55 1/15/20232,880,000 shares $163.87 million +9.1%N/A5 $56.90 12/30/20222,640,000 shares $159.06 million +9.5%N/A4.4 $60.25 12/15/20222,410,000 shares $141.03 million +6.6%N/A2.9 $58.52 11/30/20222,260,000 shares $141.27 million +1.4%N/A2.7 $62.51 11/15/20222,230,000 shares $138.64 million -8.2%N/A2.7 $62.17 10/31/20222,430,000 shares $149.30 million -10.7%N/A3.1 $61.44 10/15/20222,720,000 shares $149.19 million -16.6%6.2%3.7 $54.85 9/30/20223,260,000 shares $197.65 million +32.5%7.4%4.8 $60.63 9/15/20222,460,000 shares $73.80 million -8.2%5.6%6.5 $30.00 8/31/20222,680,000 shares $73.89 million +2.3%6.1%7.5 $27.57 8/15/20222,620,000 shares $85.57 million -0.4%6.0%7.9 $32.66 7/31/20222,630,000 shares $81.69 million -12.9%6.0%6.9 $31.06 7/15/20223,020,000 shares $92.74 million -0.3%6.9%7.2 $30.71 6/30/20223,030,000 shares $82.26 million -8.7%6.9%7.1 $27.15 6/15/20223,320,000 shares $78.62 million -7.8%8.3%7.8 $23.68 5/31/20223,600,000 shares $98.03 million +4.4%N/A8.8 $27.23 5/15/20223,450,000 shares $90.74 million +31.2%N/A8 $26.30 4/30/20222,630,000 shares $76.69 million +1.5%N/A6.3 $29.16 4/15/20222,590,000 shares $93.63 million +0.8%N/A6.3 $36.15 3/31/20222,570,000 shares $93.98 million -8.2%N/A5.9 $36.57 3/15/20222,800,000 shares $93.32 million -7.9%N/A6.2 $33.33 2/28/20223,040,000 shares $105.18 million -6.2%N/A6.3 $34.60 2/15/20223,240,000 shares $121.40 million +12.5%N/A6.7 $37.47 1/31/20222,880,000 shares $98.15 million +14.3%N/A6.5 $34.08 1/15/20222,520,000 shares $99.62 million +2.0%N/A6 $39.53 12/31/20212,470,000 shares $122.02 million +13.8%N/A6.7 $49.40 12/15/20212,170,000 shares $98.00 million +14.2%N/A6.1 $45.16 11/30/20211,900,000 shares $95.29 million +11.8%N/A5.7 $50.15 11/15/20211,700,000 shares $97.22 million -9.6%N/A5 $57.19 10/29/20211,880,000 shares $104.06 million +27.0%N/A5.5 $55.35 10/15/20211,480,000 shares $93.92 million -0.7%N/A4.3 $63.46 9/30/20211,490,000 shares $106.13 million +5.7%N/A4.1 $71.23 9/15/20211,410,000 shares $105.50 million +4.4%N/A3.3 $74.82 8/31/20211,350,000 shares $90.61 million -6.3%N/A2.8 $67.12 8/13/20211,440,000 shares $84.17 million -4.6%N/A3 $58.45Now I look stupid. Real stupid... (Ad)I thought what happened 25 years ago was a once- in-a-lifetime event… but how wrong I was. Because here we are, a quarter of a century later, almost to the exact day, and it’s happening again. Here’s the full story for you. 7/30/20211,510,000 shares $75.65 million +0.7%N/A3.1 $50.10 7/15/20211,500,000 shares $77.64 million -8.0%3.4%3.1 $51.76 6/30/20211,630,000 shares $83.80 million -23.8%3.7%3.5 $51.41 6/15/20212,140,000 shares $111.22 million +24.4%4.9%4.8 $51.97 5/28/20211,720,000 shares $50.17 million -3.9%3.9%4.3 $29.17 5/14/20211,790,000 shares $38.72 million -11.4%N/A4.9 $21.63 4/30/20212,020,000 shares $54.24 million -1.5%N/A4.5 $26.85 4/15/20212,050,000 shares $49.12 million +9.0%N/A4.2 $23.96 3/31/20211,880,000 shares $42.60 million +101.7%N/A3.9 $22.66 3/15/2021931,900 shares $21.47 million -4.9%N/A2 $23.04 2/26/2021979,700 shares $22.14 million +38.2%N/A2.3 $22.60 2/12/2021709,000 shares $11.13 million +5.1%N/A1.8 $15.70 1/29/2021674,400 shares $8.05 million +4.4%1.8%2.2 $11.93 1/15/2021646,200 shares $9.31 million -11.6%N/A2.6 $14.40 12/31/2020731,100 shares $9.05 million -49.2%N/A2.8 $12.38 12/15/20201,440,000 shares $18.33 million +12.5%N/A5.3 $12.73 11/30/20201,280,000 shares $14.45 million -2.3%N/A4.4 $11.29 11/15/20201,310,000 shares $16.11 million -6.4%N/A4.9 $12.30 10/30/20201,400,000 shares $15.76 million +7.7%N/A5.3 $11.26 10/15/20201,300,000 shares $14.60 million -3.0%N/A5.2 $11.23 9/30/20201,340,000 shares $13.39 million -17.8%N/A5.1 $9.99 9/15/20201,630,000 shares $19.33 million +10.1%N/A5.4 $11.86 8/31/20201,480,000 shares $19.18 million -3.3%N/A5.3 $12.96 8/14/20201,530,000 shares $18.85 million +15.9%N/A5.3 $12.32 7/31/20201,320,000 shares $16.16 million -5.0%N/A4.4 $12.24 7/15/20201,390,000 shares $17.44 million +4.5%N/A4.5 $12.55 6/30/20201,330,000 shares $13.91 million +30.4%N/A4.4 $10.46 6/15/20201,020,000 shares $9.86 million -6.4%N/A3.7 $9.67 5/29/20201,090,000 shares $12.11 million -14.8%N/A4 $11.11 PRTA Short Interest - Frequently Asked Questions What is Prothena's current short interest? Short interest is the volume of Prothena shares that have been sold short but have not yet been covered or closed out. As of April 30th, traders have sold 7,450,000 shares of PRTA short. Learn More on Prothena's current short interest. What is a good short interest ratio for Prothena? The short interest ratio, also known as the "days to cover ratio", is calculated by dividing the number of shares of a stock sold short divided by its average trading volume. A short interest ratio ranging between 1 and 4 generally indicates strong positive sentiment about a stock and a lack of short sellers. A short interest ratio of 10 or greater indicates strong pessimism about a stock. PRTA shares currently have a short interest ratio of 10.0. Learn More on Prothena's short interest ratio. Which institutional investors are shorting Prothena? As of the most recent reporting period, the following institutional investors, funds, and major shareholders have reported short positions of Prothena: Walleye Trading LLC, and Walleye Capital LLC. These positions are disclosed in Form 13F filings with the Securities and Exchange Commission. Is Prothena's short interest increasing or decreasing? Prothena saw a decrease in short interest in the month of April. As of April 30th, there was short interest totaling 7,450,000 shares, a decrease of 5.9% from the previous total of 7,920,000 shares. Changes in short volume can be used to identify positive and negative investor sentiment. Investors that short sell a stock are betting that its price will decline in the future. An increase in short sale volume suggests bearish (negative) sentiment among investors. A decrease on short sale volume suggests bullish (positive) sentiment. How does Prothena's short interest compare to its competitors? Here is how the short interest of companies in the industry of "pharmaceutical products" compare to Prothena: IDEAYA Biosciences, Inc. (13.45%), Edgewise Therapeutics, Inc. (17.92%), Immunocore Holdings plc (16.29%), Travere Therapeutics, Inc. (11.98%), Mesoblast Limited (2.10%), Structure Therapeutics Inc. (16.78%), Janux Therapeutics, Inc. (19.51%), Evotec SE (0.21%), ARS Pharmaceuticals, Inc. (29.82%), Adaptive Biotechnologies Co. (6.02%), Which stocks are the most shorted right now? As of the most recent reporting period, the following stocks had the largest short interest positions: Spotify Technology S.A. ($4.67 billion), Charter Communications, Inc. ($4.58 billion), Capital One Financial Co. ($4.47 billion), The Kroger Co. ($2.56 billion), Reddit, Inc. ($2.23 billion), Rivian Automotive, Inc. ($2.16 billion), Live Nation Entertainment, Inc. ($1.90 billion), SoFi Technologies, Inc. ($1.85 billion), Zscaler, Inc. ($1.75 billion), and Omnicom Group Inc. ($1.75 billion). View all of the most shorted stocks. What does it mean to sell short Prothena stock? Short selling PRTA is an investing strategy that aims to generate trading profit from Prothena as its price is falling. PRTA shares are trading down $0.05 today. To short a stock, an investor borrows shares, sells them and buys the shares back on the public market later to return it to the lender. Short sellers are betting that a stock will decline in price. If the stock does drop after selling, the short seller buys it back at a lower price and returns it to the lender. The difference between the sell price and the buy price is the trader's profit. How does a short squeeze work against Prothena? A short squeeze for Prothena occurs when it has a large amount of short interest and its stock increases in price. This forces short sellers to cover their short interest positions by buying actual shares of PRTA, which in turn drives the price of the stock up even further. How often is Prothena's short interest reported? Short interest is typically published by a stock exchange once per month. However, NASDAQ publishes a report for U.S. stocks, including PRTA, twice per month. The most recent reporting period available is April, 30 2025. More Short Interest Resources from MarketBeat Related Companies IDEAYA Biosciences Short Squeeze Edgewise Therapeutics Short Squeeze Immunocore Short Squeeze Travere Therapeutics Short Squeeze Mesoblast Short Squeeze Structure Therapeutics Short Squeeze Janux Therapeutics Short Squeeze Evotec Short Squeeze ARS Pharmaceuticals Short Squeeze Adaptive Biotechnologies Short Squeeze Short Interest Tools Stocks to Short Largest Short Interest Positions Short Interest Increases Short Interest Decreases Short Interest Reporting Dates This page (NASDAQ:PRTA) was last updated on 5/22/2025 by MarketBeat.com Staff From Our PartnersWatch This Robotics Demo Before July 23rdJeff Brown, the tech legend who picked shares of Nvidia in 2016 before they jumped by more than 22,000%... ...Brownstone Research | SponsoredWhite House to reset Social Security?Elon Musk's parting DOGE gift looks set to shock America... 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