Aclaris stock halves after phase 2a skin study misses goals

Aclaris Therapeutics’ immuno-inflammatory drug failed to improve abscesses in patients with a chronic, painful skin condition in a mid-stage trial, sending the biotech’s shares spiraling.

The initial topline results come from a phase 2a study assessing zunsemetinib, an oral MK2 inhibitor, in patients with moderate to severe hidradenitis suppurativa (HS), which causes abscesses and scarring of the skin. The 12-week, placebo-controlled study enrolled 95 patients.   

The drug didn’t hit its main efficacy goal, which was measured by change from baseline in the number of inflammatory nodules or abscesses for patients receiving zunsemetinib. The study also failed to reach secondary efficacy endpoints.

Aclaris blamed a higher placebo effect compared to other HS studies for the failure. The data, issued before market open today, prompted Aclaris' share price to plummet 54% from $12.78 at market close Friday to $5.84 as of 10:30 a.m. ET today.

Aclaris said the drug was generally well tolerated, with safety findings in line with earlier studies. The most common adverse events patients reported on zunsemetinib were dizziness at 16.7%, diarrhea at 12.5% and headache at 12.5%. Most cases were deemed mild or moderate in severity, the biotech said. There were 37 discontinuations, including 22 on zunsemetinib and 15 on placebo, with 15 citing adverse events—11 for the zunsemetinib arm and four on placebo. No serious adverse events associated with zunsemetinib were reported. 

“Despite not producing the efficacy results we had hoped for in this particularly challenging disease, we are encouraged by the consistent demonstration of zunsemetinib’s mechanism of action and the strengthening of our safety database,” Aclaris CEO Doug Manion, M.D., said in the release.

Manion added that the biotech is looking forward to an upcoming data readout from a phase 2b study of zunsemetinib in patients with moderate to severe rheumatoid arthritis. The biotech will push forward with the drug in that indication, as well as in psoriatic arthritis, which is also in phase 2 development.

The clinical-stage company also has candidates for eczema, T-cell mediated autoimmune diseases, inflammatory bowel disease and oncology indications in its pipeline.