A Study to Assess the Therapeutic Effect and Safety of Adjunctive AKST4290 in Subjects With Bullous Pemphigoid

Inclusion Criteria: * Clinical diagnosis of mild to moderate BP at screening. * Treatment naïve or initiation of whole-body high potency topical steroid treatment ≤ 7 days of screening (lesion-only treatment for any amount of time with any topical steroids prior to screening is allowed without restriction). * Provide a signed and dated informed consent form in accordance with local regulations and/or IRB/IEC guidelines. Exclusion Criteria: * Severe BP. * Initiation of gliptins and other treatments (e.g., etanercept, sulfasalazine, furosemide, penicillin) that can trigger BP if this treatment was started within 4 weeks prior to screening and is considered possibly related to the onset of BP. * Any concomitant medications in the last 3 months prior to screening and assessed by the investigator as possibly related to the development of BP. * Planned use of intravenous immunoglobulin or other concomitant treatments for BP (i.e., doxycycline, dapsone) during the study period. * Use of systemic immunosuppressants (i.e., mycophenolate, azathioprine, methotrexate) within 4 weeks prior to screening. * Treatment with rituximab within 1 year prior to screening. * Subjects taking warfarin. * Use of systemic steroids (\>10 mg prednisone or equivalent/day) within 14 days of first dose of study agent or known diseases (other than BP) that could require the use of systemic steroids within the study period. * Clinically relevant abnormal laboratory value at screening, including hematology, blood chemistry, or urinalysis (laboratory testing may be repeated once during the screening phase). * Participation in studies of investigational drugs must have been discontinued within 30 days or 5 half lives of the drug (whichever was longer) prior to screening.