Spero Therapeutics (SPRO) Short Interest
Nasdaq • SPRO • US84833T1034
1.02Last close
Market Closed
As of Oct 27, 2026, ORTEX estimated 1.9% of free float sold short, 1.8 days to cover, cost to borrow 0.48%. Sign up for live short interest data.
About this data: SPRO short interest, cost to borrow and days to cover
This page tracks how heavily Spero Therapeutics (Nasdaq:SPRO) is being shorted: ORTEX's daily short interest estimate, the cost to borrow the shares, utilization of the lendable supply and days to cover, next to the official exchange-reported figure.
- Short interest
- The number of shares that have been sold short and not yet bought back, usually shown as a percentage of free float (the shares available to trade). ORTEX estimates it every day from securities-lending data, instead of waiting for exchange reports that are published only twice a month and about two weeks late.
- Cost to borrow
- The annualised fee a short seller pays to borrow the shares, as a percentage of the position's value. A rising cost to borrow means lendable shares are getting scarce and holding the short is getting more expensive.
- Utilization
- The share of the lendable supply of a stock that is currently on loan. Close to 100% means almost no shares are left to borrow.
- Days to cover
- Short interest divided by average daily trading volume: roughly how many days of normal trading it would take for every short seller to buy back their shares.
- Exchange-reported short interest
- The official figure published by the exchange or regulator (in the US, FINRA twice a month). It is accurate but delayed, which is the gap the ORTEX daily and intraday estimates fill.
Source: ORTEX. Some figures are limited on the free view; live data and full history are part of ORTEX Advanced.
SPRO key data
Spero Therapeutics (Nasdaq: SPRO) has a market capitalization of $59.4M. Last close $1.02 (as of 2026-11-12); 52-week range $0.96 to $3.08. ORTEX data as of 2026-10-27: short interest was 1.86% of free float, 1.8 days to cover and the average cost to borrow was 0.48%. Sign up for live short interest data.