PRME Shorts Retreat — But the Borrow Market Stays Tight

Short sellers are cutting exposure in PRME. The retreat is sharp. The lending market tells a different story.

Shorts Pull Back Fast

Short interest in Prime Medicine fell 11.8% in a single day on September 24. It now stands at 17.6% of free float — the lowest level in two weeks. The week-on-week move is even larger: down 13.6%.

That is a meaningful unwind. Around 4.2 million shares of short exposure came off in one session.

Yet SI at 17.6% of float remains high by any measure. Shorts have trimmed. They have not gone away.

The Borrow Market Contradicts the Exit

Here is the tension: availability has tightened even as shorts reduce positions.

Availability sits at just 26.7% — roughly one share available for every four already borrowed. That is firmly in "tight" territory. A week ago it was 30.4%. A month ago, on September 7, it briefly compressed to 6.3% — near the 52-week floor of 3.35%.

Cost to borrow, at 0.88% annualised, remains low. That suggests the current tightness reflects genuine supply constraints rather than a panic scramble for borrows.

The ORTEX short score holds at 81.5. It has barely moved in two weeks. That level — in roughly the 97th percentile versus all names — signals persistent, deeply embedded bearish conviction even as headline SI pulls back.

Analysts and Institutions Push the Other Direction

The analyst picture is uniformly bullish. BMO Capital initiated with Outperform and a $9 target in August. HC Wainwright reiterates Buy at $8. Chardan Capital maintains Buy at $7. The mean price target sits at $7.11 — against a current price of $3.07. That implies roughly 130% upside on consensus.

BlackRock added 1.1 million shares as of August 31. ARK Investment Management added 3.1 million shares over the same period. State Street added 1.2 million.

Robert Nelsen holds a 13D activist position at 10.4% of class, as last disclosed in August 2025. Activist stakes are event-driven disclosures — positions are "as last disclosed" and may have changed.

Put/Call Ratio Ticks Up

The put/call ratio moved to 0.35 on September 24, a 1.4 standard deviation move above the 20-day mean of 0.33. It remains well below the 52-week high of 0.51. Options traders are modestly more cautious than the recent average. Not alarmed — just incrementally more hedged.

Next earnings: November 6.

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• SI % of Free Float: 17.6% (down from 20.0% a week ago)
• Availability: 26.7% — tight; 52-week low was 3.35%
• Cost to borrow: 0.88% — low
• ORTEX short score: 81.5 (near 2-week high; factor rank: 3rd percentile vs all stocks)
• Analyst mean target: $7.11 vs $3.07 close
• Notable buyers: ARK (+3.1M shares), State Street (+1.2M), BlackRock (+1.1M)
• Next earnings: November 6, 2026