Deposition of autoantibodies (α-BP180 and BP230) and complement along the 
dermal-epidermal-junction is a hallmark of bullous pemphigoid and was shown to 
be important for pathogenesis. Given the adverse effects of standard treatment 
(glucocorticoids, immunosuppressants), there is an unmet need for safe and 
effective therapies. In this phase 1 trial, we evaluated the safety and activity 
of BIVV009 (sutimlimab, previously TNT009), a targeted C1s inhibitor, in 10 
subjects with active or past bullous pemphigoid (NCT02502903). Four weekly 60 
mg/kg infusions of BIVV009 proved sufficient for inhibition of the classical 
complement pathway in all patients, as measured by CH50. C3c deposition along 
the dermal-epidermal junction was partially or completely abrogated in 4 of 5 
patients, where it was present at baseline. BIVV009 was found to be safe and 
tolerable in this elderly population, with only mild to moderate adverse events 
reported (e.g., headache, fatigue). One serious adverse event (i.e., fatal 
cardiac decompensation) occurred at the end of the post-treatment observation 
period in an 84-year-old patient with a history of diabetes and heart failure, 
but was deemed unlikely to be related to the study drug. This trial provides the 
first results with a complement-targeting therapy in bullous pemphigoid, to our 
knowledge, and supports further studies on BIVV009's efficacy and safety in this 
population.