- For both Parts 1 and 2, receipt of HSCT within 60 days of the first dose of PLX3397 is an exclusion criterion. Patients on immunosuppressive therapy post HSCT, or with clinically significant graft-versus-host disease are excluded from Part 1. (Use of topical steroids for ongoing skin GVHD is permitted). Patients for Part 1 must have a wash-out period of ≥2 weeks or at least 4 half-lives from their last systemic immunosuppressive treatment for GVHD. Patients for Part 2 may be receiving systemic immunosuppressive treatment for management of GVHD at the time of screening and enrollment