Altimmune just reported Q1 results, beat its EPS estimate, and simultaneously saw short sellers add aggressively — a setup that puts the stock in a genuinely unusual position heading into what comes next.
The short interest story is striking. Bears have rebuilt positions at speed. SI jumped from roughly 19% of the free float at the start of the week to nearly 22% by May 12 — a 16% increase in one week and a 31% rise over the past month. That puts short sellers' exposure at historically elevated levels for this name. The raw number of estimated shorted shares now sits near 36 million, close to the highest point in the 30-day window tracked by ORTEX. Despite the size of the short position, the borrowing environment is not signalling distress. Cost to borrow is modest at 0.45% annualised — barely changed from a month ago — and availability at 170% means lenders have roughly 1.7 shares still available for every one already borrowed. That is normal, not tight. Bears can still add relatively freely; there is no mechanical squeeze pressure from borrow constraints.
Options tell a different story. Positioning is conspicuously bullish. The put/call ratio has dropped to 0.077 — the lowest reading of the past year, and nearly 1.6 standard deviations below its 20-day average of 0.098. That means options traders are piling into calls and almost ignoring downside protection. The setup is the polar opposite of what the elevated short position implies. Two groups are reading the same stock in opposite directions, and Q1 results on May 13 — where ALT beat the EPS estimate by $0.07 (actual -$0.18 vs. expected -$0.25) — dropped squarely into the middle of that divergence.
The Street remains broadly constructive, even if the most recent formal analyst changes are now a few months old. The consensus holds at Buy, and the mean price target at roughly $17 sits well above the current $3.08 print — reflecting the binary, clinical-stage nature of the stock rather than a straightforward valuation gap. Bulls anchor on pemvidutide's dual-action mechanism in MASH, a roughly $340 million cash balance that extends runway through Phase 3, and the breakthrough therapy designation that accelerates regulatory dialogue. Bears point to the absence of any approved drug in the MASH space so far, an unproven commercialisation path, and dilution risk from future capital raises. The ORTEX short score at 75 places the stock in high-short-interest territory relative to its universe. The analyst recommendation divergence factor scores in the 92nd percentile — meaning the gap between the most optimistic and most pessimistic Street views is exceptionally wide.
Institutional activity around the May filing period adds another layer of texture. Deep Track Capital recently disclosed a 9.99% stake — a full new position per the filing. Viking Global and RA Capital also filed new positions around 3.5% and 3.3% respectively in late April, and BlackRock added over 3.3 million shares. That cluster of active healthcare-focused managers taking on or building meaningful stakes around current levels is notable in a stock where short sellers have simultaneously been adding. Insider behaviour reinforces the insider-versus-short tension: the CEO bought 35,000 shares across two purchases in March and April at prices between $3.14 and $3.54, and the CFO bought 15,000 shares over the same period. Neither transaction is large in dollar terms, but the pattern of executive buying at or near current price levels through a sustained period of short accumulation is a signal worth noting.
The most immediate catalyst has now passed — Q1 results printed today and beat. The next watch point is the EASL Congress 2026 presentation of IMPACT Phase 2b data in MASH, announced simultaneously with the earnings release. How the data lands there — and whether it shifts any of the institutional names who have been quietly building positions — is now the question that separates the two very different stories being told by short sellers and call buyers.
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