Plus Therapeutics enters the back half of May with its lending pool fully locked, borrowing costs at extreme levels, and a fresh earnings miss dragging the stock to a 14% weekly loss.
The clearest pressure point is the borrow market. Availability has collapsed to just 2% of short interest — meaning for every 50 shares already borrowed short, only one remains available to lend. That's not tight; it's functionally closed. The cost to borrow has surged to 180% annualised, more than doubling in a single week (+151%), after running below 40% as recently as May 6. Every share in the lending pool is now lent out, matching the 52-week peak in borrow exhaustion. This is the most constrained the borrow market has been all year, and it arrived alongside — not before — the stock's sharpest weekly decline.
Short interest itself tells a more nuanced story. At 18.5% of the free float by the latest ORTEX estimate, the position is significant by any measure. But the week-on-week change (+15%) is notable, while the 30-day picture looks dramatically different: short interest has fallen roughly 86% from the sharp spike registered in early April, when estimates briefly showed more than 8.5 million shares short before collapsing back to around 1.2 million. That April episode appears to have been a reporting artefact or a brief extreme, and the current level reflects the more settled range that has persisted since mid-April. The ORTEX short score of 85.7 — up from 81.3 just ten days ago — ranks this stock among the most heavily scrutinised in its peer group. With availability this tight, adding new short positions carries a steep and rising cost.
The catalyst is unmistakably Q1 earnings. PSTV reported on May 15, posting a GAAP EPS of -$1.05, missing consensus by $0.15. Revenue of $1.03M beat by $0.06M — a small bright spot. The stock fell nearly 9% on the day, following a prior-quarter Q1 report (March 12) that delivered an 18.75% single-day drop and a 21.6% five-day loss. The pattern is consistent: earnings are a negative catalyst. The company did note it added insurance coverage for 81 million patients, a clinical milestone that could matter for pipeline narrative but did not arrest the selling. Valuation multiples confirm a pre-revenue biotech: the P/E and EV/EBITDA are both deeply negative, and enterprise value is around $10.7 million against a market cap of approximately $36 million.
Institutional ownership is thin and concentrated. Heights Capital Management holds 7.2% of shares, far ahead of the next holder, Vanguard at 1.3%. The CEO Marc Hedrick received equity awards in April, as did CFO Andrew Sims — routine compensation grants at zero cost, signalling no open-market conviction. The only cash purchases in the recent record are small: the CFO bought $10,200 worth at $0.51 in November 2025, and an independent director paid $53,779 at roughly $0.49 in August 2025. Both were sub-$1 transactions; the stock has since rallied significantly and then partially retraced. Neither represents a material signal at current prices above $5.
Among correlated peers, the dispersion this week is wide. GDTC on Nasdaq surged 32% on the day and 49% on the week. ATRA gained 15% on the week. FBIO added just under 5% on the day. Against that backdrop, PSTV's 14% weekly decline stands out as stock-specific rather than sector-driven.
The next development to watch is whether the borrow crunch eases. With availability at 2% and cost to borrow at 180%, any short covering or new share issuance could materially shift the lending dynamics — the question is which force moves first.
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