Aclaris Therapeutics Inc. (NASDAQ: ACRS) reported that its experimental drug ATI-2138 demonstrated hair regrowth in a mouse model of severe alopecia areata, a condition that causes hair loss.

The study, conducted by Dr. Angela Christiano at Columbia University, tested ATI-2138 against ritlecitinib in mice with alopecia universalis, the most severe form of alopecia areata. Mice received either control food or food containing 100 or 300 parts per million of ATI-2138, or 300 ppm of ritlecitinib.

At week 2, mice receiving 300 ppm ATI-2138 showed 37% hair regrowth compared to 25% for ritlecitinib at the same dose. By week 4, ATI-2138 achieved 87% hair regrowth versus 48% for ritlecitinib. At the study's end at week 6, ATI-2138 maintained 93% hair regrowth compared to 78% for ritlecitinib. Control mice showed no hair regrowth.

ATI-2138 is an oral investigational compound that inhibits both ITK and JAK3, proteins involved in immune system signaling. The drug targets T cell receptor signaling and cytokines that affect lymphocyte function.

"ATI-2138 is a potent and selective inhibitor of ITK and JAK3 with dual pharmacology that has been demonstrated to downregulate Th1, Th2, Th17, TCR (ITK) and fibrosis pathway markers, and reduce itch," said Dr. Roland Kolbeck, Aclaris' chief scientific officer.

The Wayne, Pennsylvania-based company stated it plans to initiate a Phase 2b trial in the first half of 2026. Aclaris is evaluating additional potential uses for ATI-2138 beyond alopecia areata.