Aclaris’s alopecia Jak might not be worth its Salt

Another alopecia hopeful has tried to take on Pfizer and come off worse. Aclaris Therapeutics yesterday reported a mid-stage win with its oral Jak inhibitor ATI-501 – but the data did not convince the markets of the project’s commercial prospects. With the usual caveats about cross-trial comparisons, ATI-501 looks to have underperformed Pfizer’s PF-06651600 on the severity of alopecia tool (Salt) score; the big pharma has already started a phase II/III trial of its candidate. Aclaris execs said on a conference call yesterday that Pfizer still had to define the optimal regimen of PF-06651600, and that there was room for multiple players in alopecia, but investors sent Aclaris’s stock down 17% in premarket trading today. The smaller group’s topical Jak inhibitor, ATI-502, flunked its phase II study in alopecia last month; however, Aclaris execs said yesterday that the dose might have been too low and hinted that development might continue. Concert Pharmaceuticals discovered last year how tough it is to challenge Pfizer's Jak, falling after reporting data with CTP-543. The CTP-543 study had a different primary endpoint, the proportion of patients with a 50% or greater reduction in Salt.

This story has been corrected to show comparative endpoint data for the Aclaris and Pfizer projects.