Biotech IR Blog by Our CEO and Founder, Laurence Watts.
January 14, 2026
Average Biotech Short Interest at Year End 2025
Following the success of our December 10, 2025, blog “What is the typical short interest in a U.S. public biotech,” which detailed average short interest among NBI constituent companies at YE’24 and 1H’25, we are following up with an update on the average short interest at YE’25.
A reminder of where we get short information from:
While long positions are disclosed via 13F reports, knowing who has taken a short position in a company’s stock is more difficult to ascertain.
This is because the information we have on short positions comes not from funds, but from the brokers they utilize in running their portfolios. FINRA Rule 4560 mandates that every member (i.e. every brokerage) must report total short positions (both customer and proprietary accounts) in all equities, in both the middle of and at the end of each month. FINRA then provides the data to exchanges like Nasdaq and the NYSE for public disclosure. Importantly, because only the total short position is revealed, there is no way to know precisely which fund, broker or individual has actually shorted a stock.
We are publishing our YE’25 blog now because the short information on Nasdaq-listed biotechs was made public on January 12, 2025 (approximately two weeks after year-end).
Methodology
Once again, we decided to look at short positions across “small,” “medium” and “large” Nasdaq-listed biotechs.
- We took the 262 constituents of the Nasdaq Biotechnology Index (NBI) as of December 31, 2025 (note there were only 247 when we reported YE’24 and 1H’25 numbers, but subsequently the NBI was reconstituted in December).
- Since the floor for NBI inclusion is a $200 million market cap, we excluded biotechs with lower market caps from our analysis.
- At the other end of the spectrum, we decided to exclude any biotech with a market cap of more than $10 billion.
- This left us with 93 “small” biotechs, 69 “medium” biotechs, and 60 “large” biotechs, as shown in the table below.
| Description | Market Cap Range | Number of Biotechs |
| < $200M | < $200M | 7 |
| Small Biotechs | $200M – $1B | 93 |
| Medium Biotechs | $1B – $2.5B | 69 |
| Large Biotechs | $2.5 – $10B | 60 |
| > $10B | > $10B | 33 |
Source: Nasdaq, New Street Investor Relations
The metric we once again looked at was Days to Cover. Days to Cover is the best metric for assessing short positions because it blends short interest with liquidity. Instead of just showing how many shares are shorted, it shows how hard it would be for shorts to exit, by dividing the absolute short interest by a stock’s average daily trading volume. High Days to Cover signals a crowded trade and a greater squeeze risk.
Average YE’25 Biotechnology Short Interests:
“Small” Biotechs ($200M – $1B), n=93
| Date | December 31, 2024 | June 30, 2025 | December 31, 2025 |
| Average Short Interest (Days to Cover) | 8.0 | 8.1 | 7.5 |
Source: Nasdaq, New Street Investor Relations
- At YE’25, the average (mean) short interest in a “small” biotech was 7.5 Days to Cover, down from 8.1 Days to Cover at 1H’25.
Most shorted – December 31, 2025
| Biotech | Ticker | Short Interest (Days to Cover) |
| Neurogene | NGNE | 18.1 |
| KalVista Pharmaceuticals | KALV | 18.1 |
| Atea Pharmaceuticals | AVIR | 16.4 |
| Aura Biosciences | AURA | 15.5 |
| Bicara Therapeutics | BCAX | 15.0 |
Source: Nasdaq, New Street Investor Relations
- Within “small” biotechs, Neurogene and KalVista were the most shorted stocks on December 31, 2025, each at 18.1 Days to Cover, with Atea Pharmaceuticals, Aura Biosciences and Bicara Therapeutics rounding out the top five.
Least shorted – December 31, 2025
| Biotech | Ticker | Short Interest (Days to Cover) |
| Jyong Biotech | MENS | 1.0 |
| Vanda Pharmaceutical | VNDA | 1.0 |
| Kyverna Therapeutics | KYTX | 1.2 |
| Kamada Ltd. | KMDA | 1.4 |
| Vor Biopharma | VOR | 1.6 |
Source: Nasdaq, New Street Investor Relations
- At the other end of the spectrum, Jyong Biotech and Vanda Pharmaceuticals were the least shorted “small” biotechs at 1.0 Days to Cover, with Kyverna Therapeutics, Kamada and Vor Biopharma not far behind.
Medium Biotech ($1B – $2.5B), n=69
| Date | December 31, 2024 | June 30, 2025 | December 31, 2025 |
| Average Short Interest (Days to Cover) | 9.4 | 8.7 | 9.0 |
Source: Nasdaq, New Street Investor Relations
- At YE’25, the average (mean) short interest in a “medium” biotech was 9.0 Days to Cover versus 8.7 Days to Cover at mid-2025.
Most shorted – December 31, 2025
| Biotech | Ticker | Short Interest (Days to Cover) |
| Immunocore Holdings | IMCR | 36.6 |
| Syndax Pharmaceuticals | SNDX | 18.2 |
| Taysha Gene Therapeutics | TSHA | 17.6 |
| Novavax | NVAX | 17.0 |
| Grifols | GRFS | 15.5 |
Source: Nasdaq, New Street Investor Relations
- Within “medium” biotechs, Immunocore Holdings was the most shorted stock on December 31, 2025, at 36.6 Days to Cover, with Syndax, Taysha, Novavax and Grifols completing the top five.
| Least shorted – December 31, 2025 Biotech | Ticker | Short Interest (Days to Cover) |
| Ultragenyx Pharmaceuticals | RARE | 1.9 |
| Dynavax | DVAX | 1.9 |
| Pharvaris | PHVS | 2.9 |
| Phibro | PAHC | 3.4 |
| Alvotech | ALVO | 3.4 |
Source: Nasdaq, New Street Investor Relations
- Turning to the least shorted “medium” biotechs at the end of 2025, Ultragenyx Pharmaceuticals and Dynavax were the least shorted at 1.9 Days to Cover, followed by Pharvaris, Phibro and Alvotech.
Large Biotech ($2.5B – $10B), n=60
| Date | December 31, 2024 | June 30, 2025 | December 31, 2025 |
| Average Short Interest (Days to Cover) | 8.8 | 7.2 | 8.1 |
Source: Nasdaq, New Street Investor Relations
- Lastly, at YE’25, the average (mean) short interest in a “large” biotech was 8.1 Days to Cover versus 7.2 Days to Cover at mid-2025.
Most shorted – December 31, 2025
| Biotech | Ticker | Short Interest (Days to Cover) |
| Scholar Rock Holdings | SRRK | 16.1 |
| Beam Therapeutics | BEAM | 15.7 |
| CG Oncology | CGON | 14.5 |
| Alkermes | ALKS | 14.4 |
| Crinetics Pharmaceuticals | CRNX | 14.4 |
Source: Nasdaq, New Street Investor Relations
- Within “large” biotechs, Scholar Rock was the most shorted stock on December 31, 2025, at 16.1 Days to Cover, followed by Beam, CG Oncology, Alkermes and Crinetics.
Least shorted – December 31, 2025
| Biotech | Ticker | Short Interest (Days to Cover) |
| Amicus Therapeutics | FOLD | 1.0 |
| Abivax | ABVX | 1.7 |
| Indivior | INDV | 2.9 |
| Caris Life Sciences | CAI | 3.5 |
| Amneal Pharmaceuticals | AMRX | 3.7 |
Source: Nasdaq, New Street Investor Relations
- Turning to the least shorted “large” biotechs at the end of 2025, Amicus was the least shorted at 1.0 Days to Cover, followed by Abivax, Indivior, Caris, and Amneal.
Conclusions
- Overall, the average short interest across “small” (7.5), “medium” (9.0) and “large” (8.1) biotechs remained “around 8 Days to Cover” – the rule of thumb we noted in our last update.