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.

Cross-trial comparison of ATI-501 and PF-06651600
Project Company Study Placebo-adjusted absolute change from baseline in Salt at week 24
      400mg BID 600mg BID 800mg BID
ATI-501 Aclaris  AUAT-201 Oral, NCT03594227 11 points 15 points 18 points
      200mg once daily    
PF-06651600 Pfizer NCT02974868 33.6 points    
BID: Twice daily; Source: Company releases & presentations.


Jak inhibitors in clinical development for alopecia
Project Company Pharma class Trial ID Data due
Phase II/III
Olumiant Lilly Jak 1 & 2 inhibitor NCT03570749 Dec 2020
PF-06651600 Pfizer Jak 3 inhibitor NCT03732807 Mar 2021
Phase II
CTP-543 Concert  Jak 1 & 2 inhibitor NCT03137381 Interim data reported, 12mg dose data due Q3 2019
ATI-502 (topical) Aclaris/Rigel  Jak 1 & 3 inhibitor NCT03354637 Reported, failed
ATI-501 (oral) Aclaris/Rigel  Jak 1 & 3 inhibitor NCT03594227 Reported
Source: EvaluatePharma.

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

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