Altimmune enters the final stretch of September with a curious split: its short interest remains one of the heaviest in small-cap biotech, yet the bears have been quietly retreating all week while the stock quietly climbs.
The core tension here is scale vs. direction. Short interest is still enormous — nearly 47% of the free float, a level that would dominate the conversation for almost any other name. But it has fallen by nearly 7% over the past week, dropping from around 53.5 million shares short on September 15 to just under 48.9 million by September 22. The stock, meanwhile, has added 5.6% over the same stretch to close at $3.41. That combination — shorts covering, price rising — is the defining dynamic of the week.
The lending market reflects a stock where availability has improved sharply, though borrowing is not cheap-and-easy by any measure. Availability ended the week at around 122%, meaning shares to borrow now comfortably exceed those already borrowed — a notable loosening from the tighter 74% reading seen just the previous week. Cost to borrow has also eased, falling more than 22% week-on-week to roughly 0.49%, though that remains far below the stress levels that would signal a genuine squeeze. The ORTEX short score — which aggregates the bearish pressure signals — has ticked down to 78.7 from a recent high above 81, pointing to modest but real decompression. The 52-week peak for lending tightness, when availability compressed to its floor near 49%, looks increasingly distant from current conditions.
Where the street stands is equally interesting. Evercore ISI analyst Liisa Bayko trimmed her price target this morning, from $18 to $17, while maintaining an Outperform rating — the most recent of several downward target revisions since May. The consensus mean target is $17.11, implying more than 400% upside to the current price. That gap is not a sign of Street enthusiasm so much as a reminder of the binary structure of a clinical-stage biotech: Altimmune is either worth multiples of the current price if pemvidutide delivers in MASH, or it is worth very little. Bulls point to the dual-action mechanism, ~$340 million in cash supporting Phase 3 execution, and a breakthrough therapy designation. Bears flag the absence of any approved MASH drug anywhere, Phase 3 dilution risk, and a recent EPS miss. At a price-to-book near 1.9x, the market is paying modestly above asset value but still placing no premium for the pipeline — a rough summary of where institutional sentiment has settled.
The institutional register does carry one standout detail. Deep Track Capital filed a Schedule 13G in late April disclosing a 9.99% stake, and TCG Crossover Management appeared simultaneously with a 10 million share position. Viking Global and RA Capital also filed at the same threshold. These are serious healthcare-specialist investors — not retail flow. Their arrival in the register from Q2 of this year coincides with the period when SI began building, suggesting professional longs and professional shorts are both present in size, an almost theatrical setup for a small-cap biotech. Stakes are as-last-disclosed and holders dropping below 5% need not refile, so the current register may not fully reflect July and August positioning.
Insider signals add a modest corroborating note. CEO Jerome Durso bought 15,000 shares at $2.95 in mid-August — not a transformative purchase in dollar terms ($44,250), but a third open-market buy from the CEO since March, all without a 10b5-1 plan. The CFO has also bought three times across the same window. Small-scale, discretionary, repeated — that pattern is worth noting even if the sums are modest.
Earnings are scheduled for November 6. The most recent print in August produced a one-day decline of 4%, which then reversed into a 4% gain over the following five trading days. With shorts having pulled back meaningfully this week and specialist longs present in the register, the setup into that catalyst is the next thing worth watching — specifically whether short interest continues to compress or rebuilds as the event approaches.
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