Spero Therapeutics (SPRO) Short Interest Ratio & Short Volume $2.20 +0.01 (+0.23%) As of 09:57 AM Eastern This is a fair market value price provided by Polygon.io. Learn more. Add Compare Share Share Short Interest Stock AnalysisAnalyst ForecastsChartCompetitorsEarningsFDA EventsHeadlinesInsider TradesOptions ChainOwnershipSEC FilingsShort InterestSustainabilityTrendsBuy This Stock Spero Therapeutics Short Interest DataSpero Therapeutics (SPRO) has a short interest of 549,500 shares. This marks a 19.82% increase in short interest from the previous month. The short interest ratio (days to cover) is 1.0, indicating that it would take 1.0 days of the average trading volume of 1.64 million shares to cover all short positions.Current Short Interest549,500 sharesPrevious Short Interest458,600 sharesChange Vs. Previous Month+19.82%Dollar Volume Sold Short$1.03 millionShort Interest Ratio1.0 Days to CoverLast Record DateSeptember 30, 2025Outstanding Shares56,280,000 sharesPercentage of Shares Shorted0.98%Today's Trading Volume28,463 sharesAverage Trading Volume1,638,997 sharesToday's Volume Vs. Average2% 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 Get Report 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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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 9/30/2025549,500 shares $1.03 million +19.8%N/A1 $1.88 9/15/2025458,600 shares $862.17 thousand -9.0%N/A0.7 $1.88 8/31/2025504,000 shares $1.04 million -45.6%0.9%0.5 $2.07 8/15/2025927,200 shares $1.77 million -32.8%N/A0.2 $1.91 7/31/20251,380,000 shares $3.20 million +13.1%2.6%0.3 $2.32 7/15/20251,220,000 shares $3.04 million -28.2%N/A0.3 $2.49 6/30/20251,700,000 shares $4.93 million +5.6%3.2%0.4 $2.90 6/15/20251,610,000 shares $4.56 million -53.7%3.0%0.4 $2.83 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 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. 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 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 $1.13 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 $18.53 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 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 closed out or covered. As of September 30th, traders have sold 549,500 shares of SPRO 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: Group One Trading LLC. These positions are disclosed in Form 13F filings with the Securities and Exchange Commission. Is Spero Therapeutics' short interest increasing or decreasing? Spero Therapeutics saw a increase in short interest during the month of September. As of September 30th, there was short interest totaling 549,500 shares, an increase of 19.8% from the previous total of 458,600 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? Here is how the short interest of companies in the industry of "pharmaceutical products" compare to Spero Therapeutics: Monopar Therapeutics Inc. (3.54%), Eton Pharmaceuticals, Inc. (14.75%), Fulcrum Therapeutics, Inc. (6.19%), Rapt Therapeutics (7.11%), enGene Holdings Inc. (0.17%), I-Mab Sponsored ADR (4.13%), Ocugen, Inc. (18.06%), Alumis Inc. (4.25%), DBV Technologies S.A. (0.09%), Cullinan Therapeutics, Inc. (16.81%), Which stocks are the most shorted right now? As of the most recent reporting period, the following stocks had the largest short interest positions: AppLovin Corporation ($15.71 billion), Robinhood Markets, Inc. ($7.56 billion), Reddit Inc. ($4.55 billion), Coinbase Global, Inc. ($4.53 billion), CoreWeave Inc. ($4.43 billion), Charter Communications, Inc. ($4.07 billion), Seagate Technology Holdings PLC ($3.94 billion), IonQ, Inc. ($3.78 billion), TC Energy Corporation ($3.13 billion), and Live Nation Entertainment, Inc. ($3.12 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 $0.05 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 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 September, 30 2025. More Short Interest Resources from MarketBeat Related Companies Monopar Therapeutics Short Interest Eton Pharmaceuticals Short Interest Fulcrum Therapeutics Short Interest Rapt Therapeutics Short Interest enGene Short Interest I-Mab Short Interest Ocugen Short Interest Alumis Short Interest DBV Technologies Short Interest Cullinan 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 10/24/2025 by MarketBeat.com Staff From Our PartnersNEW LAW: Congress Approves Setup For Digital Dollar?Trump Ally Says Congress Approved the Setup for a Digital Dollar 2.0 But according to Rep. Marjorie Taylor ...Goldco Precious Metals | SponsoredApple's secret partnerThe Tiny Company Apple Can’t Live Without A tiny company holds the key to Apple’s biggest breakthrough sinc...The Oxford Club | Sponsored3..2..1.. 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