Q32 Bio (QTTB) Study result summary

Study design and patient population

• SIGNAL-AA Part B was an open-label, phase IIa trial in 33 patients with severe or very severe alopecia areata, including those with prior JAK inhibitor exposure, with a 36-week treatment period and a 16-week off-drug follow-up.

• Patients received a loading dose of 200 mg weekly for four weeks, then 200 mg every other week for 32 weeks, administered subcutaneously.

• The primary endpoint was mean percentage change from baseline in SALT score at week 36 in the mITT population; additional endpoints included SALT-20, SALT-30, and SALT-50 response rates.

• The mITT population had a mean age of 42, 76% female, mean baseline SALT score of 76.9, and 36-40% with prior JAK inhibitor exposure.

• Eight patients were excluded from mITT due to early discontinuation or unstable disease, none related to safety.

Efficacy results

• Bempikibart achieved a 35.3% mean reduction in SALT score at week 36 (mITT), with 40% of patients reaching SALT-20 and 30.3% in ITT; similar trends for SALT-30 and SALT-50 responses.

• Robust hair regrowth was observed in both severe (mean SALT reduction 37.8%) and very severe (27.4%) subgroups.

• Efficacy was consistent among patients with prior JAK inhibitor exposure, suggesting potential as both first-line and JAK off-ramp therapy.

• Durable or deepening responses were observed off-drug, with some patients maintaining or improving hair regrowth through 52 weeks.

• Additional analyses showed meaningful proportions of patients achieving 30% and 50% hair regrowth.

Safety and tolerability

• No Grade 3 or higher adverse events or new safety signals were observed; all adverse events were mild to moderate.

• Injection site reactions occurred in 36% of patients, were mild, resolved quickly, and incidence was only 4% per dose; upper respiratory tract infection (21%) and gastroenteritis (15%) were also reported.

• No discontinuations were related to safety; mean lymphocyte count reductions were consistent with mechanism and not linked to infection.

• The safety profile remained favorable with the loading dose regimen and negligible ADA impact.