United States-based Pfizer has commenced a phase 2b/3 clinical trial of PF-06651600, an oral JAK3 inhibitor, intended to treat patients with moderate to severe alopecia areata, it was reported on Friday.

The product has achieved the primary efficacy endpoint in a Phase 2a study, which indicated that it improved hair regrowth on the scalp relative to baseline at week 24 as measured by the Severity of Alopecia Tool score. The investigational candidate also reached all secondary endpoints in the study, in addition to meeting the primary efficacy endpoint. PF-06651600 is also being evaluated for rheumatoid arthritis, Crohn's disease and ulcerative colitis.

The company will enrol up to 660 patients in the double-blind, placebo-controlled and dose-ranging phase 2b/3 clinical trial to evaluate the safety and effectiveness of PF-06651600 in adults and adolescents aged 12 years and older with 50% or greater scalp hair loss.