Spero Therapeutics (SPRO) Short Interest Ratio & Short Volume $2.93 -0.09 (-2.98%) Closing price 06/23/2025 04:00 PM EasternExtended Trading$2.92 -0.01 (-0.17%) As of 07:30 AM 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 ForecastsChartCompetitorsEarningsHeadlinesInsider TradesOptions ChainOwnershipSEC FilingsShort InterestSustainabilityTrendsBuy This Stock Spero Therapeutics Short Interest DataSpero Therapeutics (SPRO) has a short interest of 3.48 million shares, representing 6.69% of the float (the number of shares available for trading by the public). This marks a 446.57% increase in short interest from the previous month. The short interest ratio (days to cover) is 0.9, indicating that it would take 0.9 days of the average trading volume of 1.17 million shares to cover all short positions.Current Short Interest3,480,000 sharesPrevious Short Interest636,700 sharesChange Vs. Previous Month+446.57%Dollar Volume Sold Short$8.98 millionShort Interest Ratio0.9 Days to CoverLast Record DateMay 31, 2025Outstanding Shares55,910,000 sharesShort Percent of Float6.69%Today's Trading Volume860,877 sharesAverage Trading Volume1,168,663 sharesToday's Volume Vs. Average74% Short Selling Spero Therapeutics? Sign up to receive the latest short interest report for Spero Therapeutics and its competitors with MarketBeat's FREE newsletter. Email Address Skip Charts & View Short Interest HistoryShort Interest ChartDays to Cover ChartShort Percent of Float ChartSPRO Short Interest Over TimeSPRO Days to Cover Over TimeSPRO Percentage of Float Shorted Over Time Spero Therapeutics Short Interest History Export to ExcelReport DateTotal Shares Sold ShortDollar Volume Sold ShortChange from Previous ReportPercentage of Float ShortedDays to CoverPrice on Report Date 5/31/20253,480,000 shares $8.98 million +446.6%6.7%0.9 $2.58 5/15/2025636,700 shares $414.62 thousand -1.3%1.2%5 $0.65 4/30/2025645,200 shares $424.54 thousand -19.5%N/A5 $0.66 4/15/2025801,300 shares $596.49 thousand +60.9%1.5%4.8 $0.74 3/31/2025498,100 shares $358.63 thousand +13.9%1.0%2.6 $0.72 3/15/2025437,300 shares $342.14 thousand +3.0%0.8%2.2 $0.78 2/28/2025424,700 shares $329.40 thousand -1.1%0.8%2 $0.78 2/15/2025429,600 shares $350.12 thousand +14.0%0.8%1.9 $0.82 1/31/2025376,800 shares $322.77 thousand +6.4%N/A1.5 $0.86 1/15/2025354,100 shares $317.70 thousand -14.2%N/A1.2 $0.90 Get the Latest News and Ratings for SPRO and Related StocksEnter your email address below to receive the latest news and analysts' ratings for Spero Therapeutics and its competitors with MarketBeat's FREE daily newsletter. 12/31/2024412,600 shares $424.98 thousand -8.6%N/A1.4 $1.03 12/15/2024451,200 shares $482.78 thousand -8.6%N/A1.7 $1.07 11/30/2024493,800 shares $562.93 thousand -9.7%N/A2 $1.14 11/15/2024546,800 shares $645.22 thousand -12.5%N/A2.3 $1.18 10/31/2024625,200 shares $769.00 thousand +61.5%N/A3 $1.23 10/15/2024387,100 shares $464.52 thousand +0.7%N/A3.2 $1.20 9/30/2024384,300 shares $514.96 thousand -0.2%N/A3 $1.34 9/15/2024385,200 shares $527.72 thousand -5.8%N/A3.4 $1.37 8/31/2024409,100 shares $560.47 thousand +8.6%N/A3.1 $1.37 8/15/2024376,700 shares $455.81 thousand +5.8%N/A2.9 $1.21 7/31/2024355,900 shares $501.82 thousand -8.8%N/A2.6 $1.41 7/15/2024390,300 shares $563.98 thousand -7.1%N/A2.7 $1.45 6/30/2024420,000 shares $546 thousand -3.3%N/A2.5 $1.30 6/15/2024434,200 shares $590.51 thousand -10.3%N/A2.3 $1.36 5/31/2024483,900 shares $687.14 thousand -2.1%N/A1.7 $1.42 5/15/2024494,200 shares $800.60 thousand +5.6%N/A1.6 $1.62 4/30/2024468,100 shares $664.70 thousand -8.8%N/A1.5 $1.42 4/15/2024513,200 shares $785.20 thousand -21.5%N/A1.6 $1.53 3/31/2024653,800 shares $1.12 million +6.5%N/A2.1 $1.72 3/15/2024613,900 shares $1.10 million +8.9%N/A2 $1.79 2/29/2024564,000 shares $930.60 thousand -8.9%N/A2.8 $1.65 2/15/2024619,000 shares $940.88 thousand -12.5%N/A3.2 $1.52 1/31/2024707,100 shares $1.07 million +4.0%N/A3.8 $1.52 1/15/2024680,200 shares $986.29 thousand -13.8%N/A4 $1.45 12/31/2023789,000 shares $1.16 million -19.2%N/A4.5 $1.47 12/15/2023976,500 shares $1.26 million -9.6%N/A6 $1.29 11/30/20231,080,000 shares $1.23 million -4.4%N/A6.2 $1.14 11/15/20231,130,000 shares $1.29 million -10.3%N/A4.7 $1.14 10/31/20231,260,000 shares $1.36 million -3.1%N/A4.8 $1.08 10/15/20231,300,000 shares $1.47 million -3.7%N/A4.1 $1.13379 passengers walked away from this (Ad)Elon Musk just wrote a $51 million check to back this material’s next phase… Because it’s not just saving lives in aviation — it’s solving the biggest flaw in AI. And only one U.S. company has the patent.Chris Rowe breaks the story in this urgent briefing: Watch before it disappears. 9/30/20231,350,000 shares $1.63 million -5.6%N/A4.2 $1.21 9/15/20231,430,000 shares $1.83 million +25.4%N/A4.3 $1.28 8/31/20231,140,000 shares $1.71 million No ChangeN/A3.2 $1.50 8/15/20231,140,000 shares $1.53 million -2.6%N/A3.8 $1.35 7/31/20231,170,000 shares $1.91 million No ChangeN/A3.9 $1.63 7/15/20231,170,000 shares $1.77 million -4.9%N/A4.2 $1.51 6/30/20231,230,000 shares $1.78 million +40.4%N/A4 $1.45 6/15/2023876,300 shares $1.38 million -0.6%N/A1.8 $1.57 5/31/2023881,800 shares $1.53 million -9.5%N/A1.7 $1.74 5/15/2023974,400 shares $1.82 million -32.8%N/A1.7 $1.87 4/30/20231,450,000 shares $2.57 million -21.6%N/A2.5 $1.77 4/15/20231,850,000 shares $3.18 million +17.1%N/A3.3 $1.72 3/31/20231,580,000 shares $2.29 million +67.6%N/A2.8 $1.45 3/15/2023942,700 shares $1.39 million +142.0%N/A2.1 $1.47 2/28/2023389,500 shares $576.46 thousand +35.5%N/A0.9 $1.48 2/15/2023287,400 shares $514.45 thousand -38.6%N/A0.7 $1.79 1/31/2023468,200 shares $866.17 thousand -29.9%N/A0.8 $1.85 1/15/2023667,900 shares $1.34 million -21.4%N/A1.1 $2.00 12/30/2022849,400 shares $1.47 million -14.6%N/A1.1 $1.73 12/15/2022994,200 shares $1.69 million -23.5%N/A0.4 $1.70 11/30/20221,300,000 shares $2.52 million -13.9%N/A0.2 $1.94 11/15/20221,510,000 shares $2.84 million +22.8%5.5%0.2 $1.88 10/31/20221,230,000 shares $2.41 million -15.8%4.5%0.2 $1.96 10/15/20221,460,000 shares $2.89 million -32.4%5.4%0.2 $1.98 9/30/20222,160,000 shares $4.32 million +177.9%8.0%0.3 $2.00 9/15/2022777,200 shares $753.88 thousand +182.0%2.9%0.1 $0.97 8/31/2022275,600 shares $222.38 thousand -32.9%1.0%0.1 $0.81 8/15/2022410,600 shares $371.06 thousand +1.1%1.5%1.3 $0.90 7/31/2022406,100 shares $297.35 thousand -27.2%1.6%1.1 $0.73 7/15/2022557,800 shares $440.66 thousand +34.9%2.3%0.8 $0.79 6/30/2022413,600 shares $306.48 thousand -70.9%1.7%0.6 $0.74 6/15/20221,420,000 shares $1.36 million -9.0%5.8%1.9 $0.96 5/31/20221,560,000 shares $1.84 million -5.5%6.4%2.3 $1.18 5/15/20221,650,000 shares $2.82 million -55.3%6.8%2.6 $1.71 4/30/20223,690,000 shares $17.93 million +6.7%14.6%6.3 $4.86 4/15/20223,460,000 shares $21.14 million +6.5%13.7%16.7 $6.11 3/31/20223,250,000 shares $28.28 million +4.2%13.1%16.5 $8.70 3/15/20223,120,000 shares $25.40 million +5.4%12.6%18.6 $8.14 2/28/20222,960,000 shares $28.42 million +5.7%11.9%20.8 $9.60 2/15/20222,800,000 shares $27.94 million +12.0%11.3%19.6 $9.98 1/31/20222,500,000 shares $29.68 million +4.6%10.1%18.6 $11.87 1/15/20222,390,000 shares $31.55 million +4.4%9.4%21.1 $13.20 12/31/20212,290,000 shares $36.66 million -1.7%9.0%23.2 $16.01 12/15/20212,330,000 shares $30.64 million -0.9%9.2%24.5 $13.15 11/30/20212,350,000 shares $33.49 million -2.5%9.3%23.9 $14.25 11/15/20212,410,000 shares $39.55 million -3.6%9.5%22.4 $16.41 10/29/20212,500,000 shares $43.90 million No Change9.9%21 $17.56 10/15/20212,500,000 shares $42.55 million -1.2%9.9%21.4 $17.02 9/30/20212,530,000 shares $46.58 million -1.9%10.0%20.4 $18.41 9/15/20212,580,000 shares $47.81 million -4.1%10.2%16.4 $18.53379 passengers walked away from this (Ad)Elon Musk just wrote a $51 million check to back this material’s next phase… Because it’s not just saving lives in aviation — it’s solving the biggest flaw in AI. And only one U.S. company has the patent.Chris Rowe breaks the story in this urgent briefing: Watch before it disappears. 8/31/20212,690,000 shares $51.78 million +1.9%10.9%15.8 $19.25 8/13/20212,640,000 shares $35.69 million No Change10.7%16.5 $13.52 7/30/20212,640,000 shares $35.22 million No Change11.6%17 $13.34 7/15/20212,640,000 shares $37.73 million +10.0%12.1%16.6 $14.29 6/30/20212,400,000 shares $33.50 million -23.1%9.9%14.5 $13.96 6/15/20213,120,000 shares $47.55 million -1.0%12.9%22.1 $15.24 5/28/20213,150,000 shares $45.68 million -3.4%13.0%20.3 $14.50 5/14/20213,260,000 shares $42.28 million -2.1%N/A19.9 $12.97 4/30/20213,330,000 shares $45.59 million -2.1%N/A17.5 $13.69 4/15/20213,400,000 shares $44.81 million +0.6%N/A14 $13.18 3/31/20213,380,000 shares $46.04 million +50.9%N/A12.9 $13.62 3/15/20212,240,000 shares $37.50 million +1.8%N/A6.7 $16.74 2/26/20212,200,000 shares $40.44 million -1.8%N/A6.6 $18.38 2/12/20212,240,000 shares $45.52 million -0.4%N/A6.6 $20.32 1/29/20212,250,000 shares $40.95 million +0.9%N/A6.4 $18.20 1/15/20212,230,000 shares $37.08 million -0.9%N/A7.3 $16.63 12/31/20202,250,000 shares $45.52 million +17.8%N/A7.3 $20.23 12/15/20201,910,000 shares $34.02 million -2.1%N/A6.2 $17.81 11/30/20201,950,000 shares $32.62 million +1.6%N/A5.9 $16.73 11/15/20201,920,000 shares $27.49 million +2.7%N/A5 $14.32 10/30/20201,870,000 shares $25.13 million +3.3%N/A5.1 $13.44 10/15/20201,810,000 shares $24.63 million +1.7%N/A5.2 $13.61 9/30/20201,780,000 shares $19.86 million -6.3%N/A5.4 $11.16 9/15/20201,900,000 shares $18.98 million +49.6%N/A6.4 $9.99 8/31/20201,270,000 shares $13.80 million +18.7%8.5%5.3 $10.87 8/14/20201,070,000 shares $13.38 million +2.9%7.2%6.7 $12.50 7/31/20201,040,000 shares $12.17 million +8.0%7.0%6.2 $11.70 7/15/2020963,100 shares $12.96 million +11.1%6.7%5 $13.46 6/30/2020866,900 shares $11.49 million +39.1%6.0%4.6 $13.25 SPRO Short Interest - Frequently Asked Questions What is Spero Therapeutics' current short interest? Short interest is the volume of Spero Therapeutics shares that have been sold short but have not yet been covered or closed out. As of May 31st, investors have sold 3,480,000 shares of SPRO short. 6.69% of Spero Therapeutics' shares are currently sold short. Learn More on Spero Therapeutics' current short interest. What is a good short interest ratio for Spero Therapeutics? 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. SPRO shares currently have a short interest ratio of 1.0. Learn More on Spero Therapeutics's short interest ratio. Which institutional investors are shorting Spero Therapeutics? As of the most recent reporting period, the following institutional investors, funds, and major shareholders have reported short positions of Spero Therapeutics: Simplex Trading LLC. These positions are disclosed in Form 13F filings with the Securities and Exchange Commission. What is a good short interest percentage for Spero Therapeutics? Companies that have a short interest as a percentage of float below 10% indicates positive investor sentiment and few short sellers. Stocks with a short interest percentage above 10% is considered high, suggesting some investors are pessimistic about the stock. Companies with a short interest percentage of 20% or more indicates widespread negative sentiment. 6.69% of Spero Therapeutics' floating shares are currently sold short. Is Spero Therapeutics' short interest increasing or decreasing? Spero Therapeutics saw a increase in short interest in the month of May. As of May 31st, there was short interest totaling 3,480,000 shares, an increase of 446.6% from the previous total of 636,700 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 Spero Therapeutics' short interest compare to its competitors? 6.69% of Spero Therapeutics' shares are currently sold short. Here is how the short interest of companies in the industry of "pharmaceutical products" compare to Spero Therapeutics: Nuvation Bio Inc. (18.67%), ChromaDex Co. (4.29%), Dianthus Therapeutics, Inc. (28.73%), Sana Biotechnology, Inc. (35.28%), Sage Therapeutics, Inc. (9.44%), Kura Oncology, Inc. (11.38%), Relay Therapeutics, Inc. (14.14%), Verve Therapeutics, Inc. (30.17%), Altimmune, Inc. (32.22%), Bicycle Therapeutics plc (5.46%), Which stocks are the most shorted right now? As of the most recent reporting period, the following stocks had the largest short interest positions: SPDR S&P 500 ETF Trust ($64.96 billion), Invesco QQQ ($27.88 billion), iShares Russell 2000 ETF ($19.94 billion), iShares 20+ Year Treasury Bond ETF ($9.69 billion), MicroStrategy Incorporated ($8.58 billion), SPDR S&P Biotech ETF ($5.72 billion), Invesco S&P 500 Equal Weight ETF ($5.45 billion), iShares iBoxx $ Investment Grade Corporate Bond ETF ($4.70 billion), Charter Communications, Inc. ($4.54 billion), and Industrial Select Sector SPDR Fund ($4.49 billion). View all of the most shorted stocks. What does it mean to sell short Spero Therapeutics stock? Short selling SPRO is an investing strategy that aims to generate trading profit from Spero Therapeutics as its price is falling. SPRO shares are trading down $0.09 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 Spero Therapeutics? A short squeeze for Spero Therapeutics occurs when it has a large amount of short interest and its stock appreciates in price. This forces short sellers to cover their short interest positions by buying actual shares of SPRO, which in turn drives the price of the stock up even further. How often is Spero Therapeutics' 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 SPRO, twice per month. The most recent reporting period available is May, 31 2025. More Short Interest Resources from MarketBeat Related Companies Nuvation Bio Short Interest ChromaDex Short Interest Dianthus Therapeutics Short Interest Sana Biotechnology Short Interest Sage Therapeutics Short Interest Kura Oncology Short Interest Relay Therapeutics Short Interest Verve Therapeutics Short Interest Altimmune Short Interest Bicycle Therapeutics Short Interest Short Interest Tools Stocks to Short Largest Short Interest Positions Short Interest Increases Short Interest Decreases Short Interest Reporting Dates This page (NASDAQ:SPRO) was last updated on 6/24/2025 by MarketBeat.com Staff From Our Partners379 passengers walked away from thisElon Musk just wrote a $51 million check to back this material’s next phase… Because it’s not just saving l...True Market Insiders | SponsoredWhen This Happens, You Don’t Wait. 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