When to expect scalp hair regrowth during treatment of severe alopecia areata with baricitinib: insights from trajectories analyses of patients enrolled in two phase III trials

Abstract Background Baricitinib is approved for the treatment of adults with severe alopecia areata (AA). In the absence of robust data on the patterns of regrowth during treatment of severe AA, there is a gap in the knowledge regarding treatment expectations. Objectives To examine whether different clinical response subgroups could be identified in baricitinib-treated patients with severe AA and factors that contribute to these subgroups. Methods The BRAVE-AA1 and BRAVE-AA2 phase III trials enrolled patients with severe AA [Severity of Alopecia Tool (SALT) score ≥ 50 (≥ 50% scalp hair loss)]. Patients randomized to baricitinib 4 mg or 2 mg retained their treatment allocation for 52 weeks. Based on patterns identified through growth mixture modelling (GMM), patients were categorized into responder subgroups according to when they first achieved ≥ 30% improvement from baseline in SALT score (SALT30). For each responder subgroup, trajectories of response (i.e. achievement of a SALT score ≤ 20, SALT score ≤ 10 and ≥ 50% change from baseline in SALT score) and baseline disease characteristics are reported. Results Respectively, 515 and 340 patients were randomized to once-daily baricitinib 4 mg and 2 mg at baseline; 69% and 51%, respectively, achieved SALT30 at least once by week 52. Based on GMM findings, we identified three responder subgroups: early (SALT30 by week 12), gradual (SALT30 after week 12–week 36) and late (SALT30 after week 36–week 52). The proportions of early, gradual and late responders and nonresponders were, respectively, 33%, 28%, 8% and 31% among patients treated with baricitinib 4 mg, and 20%, 23%, 9% and 49%, respectively, among those treated with baricitinib 2 mg. Early responders had a shorter trajectory to maximal clinical outcomes (e.g. > 78% achieved a SALT score ≤ 20 by week 36) vs. gradual or late responders. Early responders were more frequent among patients with baseline severe AA (SALT score 50 to < 95) vs. very severe AA (SALT score 95–100). Overall, responders (early to late) were more frequent in patients with short (< 4 years) episodes of hair loss. Conclusions These analyses identified early, gradual and late responder subgroups for scalp hair regrowth in baricitinib-treated patients with severe AA, and that these subgroups are influenced by baseline characteristics. Findings from these analyses will help to inform treatment expectations for scalp hair regrowth.