Alumis shares fell about 56% on Tuesday after the biotechnology company said its Phase 2b LUMUS study of envudeucitinib failed to show efficacy in patients with moderate-to-severe systemic lupus erythematosus (SLE).

At one point in the session, the stock dropped as much as 57.86%. The move came after the company reported that the trial, which enrolled 408 participants, did not meet its primary endpoint of improving disease activity at the 48-week mark using the British Isles Lupus Assessment Group-based Composite Lupus Assessment, or BICLA. Secondary endpoints in the overall study population also failed to reach statistical significance.

A prespecified subset analysis, however, showed that patients classified as IFNGS-high recorded meaningful improvement on both the primary measure and key secondary outcomes. Alumis said IFNGS-high patients represent the majority of moderate-to-severe SLE diagnoses, but the company added that this group was underrepresented in the trial population, which affected the overall result. That detail matters because lupus studies often hinge on whether a drug can show a clear signal in the subgroup most likely to respond, especially when the broader population is biologically mixed.

The company said envudeucitinib was generally well tolerated over the course of the study and that no unexpected safety concerns emerged. It also said pharmacodynamic analysis confirmed dose-dependent modulation of the interferon signaling pathway, with the 40 mg dose given twice daily producing the strongest suppression effect.

A post on X from Limitless Finance said: "ALUMIS $ALMS JUST COLLAPSED 55% AFTER ITS LUPUS CLINICAL TRIAL FAILED $ALMS erased $1.5B in valuation today after its 408-patient Phase 2b LUMUS trial missed its primary endpoint despite being described as ‘potentially pivotal.’ The drug showed promise in patients with…" The post included the link and was published on September 1, 2026.

Looking ahead, Alumis said it plans to speak with regulatory authorities about a potential Phase 3 trial focused specifically on lupus patients with high interferon gene signatures. The company said no targeted oral treatment options currently exist for SLE, which it views as a reason to keep advancing development in the indication. For investors and clinicians following the program, the next key milestone is whether regulators are open to a narrower study design based on the IFNGS-high signal rather than the overall trial miss.

At the same time, Alumis said its psoriasis program remains on track. The company continues to target a fourth-quarter 2026 New Drug Application submission for envudeucitinib in moderate-to-severe plaque psoriasis, supported by favorable results from its Phase 3 ONWARD program. That separate timeline gives the company another regulatory path to watch even as the lupus program resets.

Envudeucitinib is an oral allosteric inhibitor of tyrosine kinase 2, or TYK2, and works by modulating immune signaling pathways regulated by IL-23, IL-17, and Type I interferon. The mechanism is the same whether the drug is being evaluated for lupus or psoriasis.

Before Tuesday’s decline, Alumis had a market capitalization of about $2.99 billion. The stock had gained more than 123% year to date, average daily trading volume was about 1.29 million shares, and technical sentiment indicators had assigned the shares a Hold rating before the trial results were disclosed.