Q32 Bio (QTTB) said late Tuesday that topline results from its SIGNAL-AA phase 2a "signal-finding" trial evaluating bempikibart (ADX-914) showed "encouraging" clinical activity in patients with alopecia areata.

The company's shares plunged more than 65% in Wednesday's premarket activity.

At week 24, patients showed a mean reduction in the Severity of Alopecia Tool score of 16% in the bempikibart group versus a 2% drop in the placebo group. At week 24, 9% of bempikibart patients achieved a SALT-20 compared with none in placebo.

The company said it plans to enroll additional patients in the study.

However, the company said its SIGNAL-AD phase 2a clinical trial in atopic dermatitis failed to meet the primary endpoint in Part B after demonstrating promising findings in Part A.

At week 14, data from Part B showed patients treated with bempikibart showed a 74% improvement in the average Eczema Area and Severity Index from baseline, compared with 76% for the placebo group.

"We are disappointed that the SIGNAL-AD trial did not achieve its primary endpoint," said Jodie Morrison, chief executive officer of Q32 Bio. "Based upon the findings, including the high placebo rate, we plan to conduct a review to better understand the results."