Alnylam Pharmaceuticals heads into its October 29 earnings report with short interest climbing steadily for the past month and the Street divided on where the stock goes next, while the company trades roughly a third below the average analyst target.
Short interest has rebuilt sharply in September. Positions are now 37% larger than they were a month ago, reaching 5.5% of the free float at around 7.3 million shares. The bulk of that increase arrived in a tight cluster: shorts added more than 1.5 million shares in the fortnight ending September 11, then continued adding through last week. Despite that accumulation, the borrow market is not stressed. Cost to borrow is just 0.44%, roughly where it has been all month. Availability is extraordinarily loose at over 1,600%, meaning there are more than sixteen shares available to lend for every one currently borrowed. Nothing in the lending market suggests a squeeze is imminent. Options positioning is similarly calm. The put/call ratio at 0.63 is fractionally below its 20-day average of 0.64, and the z-score of -0.87 indicates no unusual demand for downside protection ahead of results. Taken together, the positioning picture is one of measured scepticism, not aggressive short-side conviction.
The Street's case for and against the stock reflects a genuine disagreement about how much of the pipeline is priced in. Bulls point to a TTR franchise with an estimated 200,000 underdiagnosed U.S. ATTR-CM patients and more than 80% still untreated, alongside a hypertension candidate in ZENITH targeting a market where over 200 million adults across seven major markets carry the diagnosis. The bear case centres on execution risk in that same pipeline, particularly the unresolved questions around zilebesiran's REVERSIR data, and an outstanding U.S. Attorney's Office subpoena tied to government price reporting and distributor arrangements. The most recent bellwether move came this morning: JP Morgan's Jessica Fye cut her target modestly from $375 to $369 while holding an Overweight rating, a trimming rather than a change of view. Jefferies raised its target at the beginning of the month to $260, still sitting below the current $254 price, and remains at Hold. HC Wainwright has reiterated Buy at $455 twice this month. The consensus mean target is $371, implying roughly 46% upside from current levels, but that gap is narrowing as more post-earnings downgrades from August work their way through. Valuation gives the bulls some comfort: the PE has expanded modestly over the past month to 22x, and the EV/EBITDA of about 22x has actually compressed slightly over the same period.
That August earnings event is worth recalling before the October 29 print. The most recent full quarterly release on July 30 produced a one-day decline of 28% and a five-day loss of nearly 25%. The August 6 print was more modest, pulling back just over 4% on the day and then recovering to near flat over the week. The pattern tells a familiar biotech story: big swings, in both directions, are the norm around results. Factor scores add some context. Earnings momentum ranks well above the sector median over 30 days at the 71st percentile. But the EPS surprise score of 23 suggests actual beats have been rare. The EPS 12-month forward year-on-year improvement score, at the 29th percentile, points to limited near-term estimate inflation.
On alt data, CMS Medicaid reimbursement data through the first quarter of 2026 recorded $12.4 million in Medicaid dollars reimbursed to Alnylam drugs, up 39% on the same period a year earlier. Medicaid prescriptions came in at 224 units for the quarter, up 27% year-on-year. These are not leading indicators in the measured sense: none of Alnylam's four tracked datasets have been formally measured against its reported figures, so the Medicaid readings are background colour rather than a signal for the print. Still, the volume trend is consistent with the bull thesis on diagnosis and treatment expansion.
The key variable heading into October 29 is whether Alnylam can provide fresh clarity on zilebesiran's development path and the regulatory subpoena. Short sellers are rebuilding positions at an accelerating rate even as borrow remains cheap and the options market stays relaxed, a combination that suggests the shorts are making a fundamental rather than technical bet, and the size of the July earnings reaction is a reminder of how quickly that bet can be resolved in either direction.
See the live data behind this article on ORTEX.
Open ALNY on ORTEX →ORTEX Market Intelligence content is generated by AI from a snapshot of ORTEX's proprietary data. Content is informational only and does not constitute investment advice.
