Regeneron stock stays in focus as CIDEB data support pipeline

Regeneron reported on Sunday, November 8, that a single dose of its investigational CIDEBsiRNA produced sustained reductions in liver fat in adults with metabolic dysfunction-associated steatotic liver disease. The company said the first-in-human results were presented at the AASLD The Liver Meeting 2026 and published simultaneously in The New England Journal of Medicine. Regeneron stock traded at 876.20 euros on Lang & Schwarz at 14:02 CET on Thursday, November 12.

The company evaluated a single subcutaneous dose at four dose levels in a Phase 1/2 trial involving 30 CIDEBsiRNA recipients and 10 placebo recipients. Safety and tolerability were the primary objectives, while liver fat and liver-injury markers were secondary measures.

Durable liver-fat reduction

Regeneron said liver fat fell by 58% to 80% at week 36 among treated participants, measured by magnetic resonance imaging-proton density fat fraction. The reduction had reached 49% to 72% at week six and deepened over the subsequent follow-up period. The placebo group recorded a mean reduction of 2.9% at week 36.

Liver fat fell below 5% in 62% of CIDEBsiRNA recipients at week 36, compared with none of the placebo recipients. Regeneron also said 93% of treated participants with week-36 data achieved at least a 30% reduction in liver fat, a threshold associated with histological MASH resolution. Mean alanine aminotransferase levels declined across all doses, while aspartate aminotransferase changes moved in the same direction.

The findings strengthen the clinical rationale for a liver-targeted RNA interference approach based on genetic insights from the Regeneron Genetics Center. The company said effects lasting through week 36 support the potential for twice-yearly dosing, although the evidence remains early and the trial was not designed to establish regulatory efficacy.

Development risk remains substantial

Regeneron said overall adverse-event rates were generally similar between the treatment and placebo groups, with events generally mild or moderate. One severe, serious hyperglycemia event in a treated participant was not attributed to the study drug and was later linked to adult-onset type 1 diabetes, according to the company. No trial participant discontinued treatment, and no nausea or vomiting events were reported in the CIDEBsiRNA groups.

Longer-term safety and histologic outcomes are being evaluated in recruiting Phase 2a, Phase 2b and Phase 3 studies. That next stage will test whether the reduction in liver fat translates into durable effects on liver injury, disease progression and tissue-level outcomes. The company stated that CIDEBsiRNA remains investigational and has not been evaluated by any regulatory authority.

Regeneron scheduled a virtual Regeneron Roundtable for November 10 at 8:30 a.m. Eastern time to discuss its cardiometabolic and MASH pipeline. The company said a replay would be archived on its investor website for at least 30 days. The [Regeneron release](https://investor.regeneron.com/news-releases/news-release-details/cideb-sirna-normalizes-liver-fat-and-improves-liver-injury/ "Regeneron CIDEBsiRNA release" rel='nofollow noopener noreferrer' target='_blank' style='color:inherit;text-decoration:underline;text-decoration-style:dotted;text-decoration-color:#9ca3af;text-underline-offset:2px;'>company announcement also identifies Alnylam as its collaboration partner for the program.

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