Efficacy and Safety of KD025 in Subjects With cGVHD After At Least 2 Prior Lines of Systemic Therapy

Phase 2, open label, randomized, multicenter study in subjects with cGVHD who have previously been treated with at least 2 prior lines of systemic therapy. Approximately 166 subjects with active cGVHD will be randomized (1:1) to receive treatment with one of two belumosudil (formerly known as KD025) regimens: * Arm A: belumosudil 200 mg QD * Arm B: belumosudil 200 mg BID With Amendment 2, the sample size was increased from approximately 126 subjects, with additional subjects to be enrolled as follows: * 20 adolescents * 20 adults into a site-specific Companion Study to collect biospecimens These additional subjects will also be randomized (1:1) to Arm A or Arm B. Any adolescent taking a proton pump inhibitor (PPI) or a strong CYP3A4 inducer will begin Cycle 1 Day 1 at the escalated dose of belumosudil 200 mg BID. Randomization will be stratified according to prior cGVHD treatment with ibrutinib (Yes / No) and severe cGVHD at baseline (Yes / No). Subjects may receive treatment in 28-day treatment cycles until clinically significant progression of cGVHD. Subjects who have not achieved a response after 12 cycles of belumosudil should be withdrawn if in the Investigator's judgment there is no evidence of clinical benefit. Subjects will undergo evaluations as outlined in the Study Assessments table (Appendix A). The primary endpoint is the overall response rate (ORR) with responses as defined by the 2014 National Institute of Health (NIH) Consensus Development Project on clinical trials in cGVHD.