Phase I/II Open Label Study of Belumosudil Mesylate Alone, and in Combination With Dexamethasone, in Patients With Relapsed/Refractory Multiple Myeloma

Inclusion Criteria: * Patients must have had a histologically or cytologically confirmed diagnosis of symptomatic multiple myeloma at the time of their initial diagnosis, which requires the presence of all three of the following criteria: * Clonal bone marrow plasma cells ≥10%, AND * A monoclonal protein in either the serum or urine (except in subjects with non-secretory myeloma), AND * Evidence of end-organ damage or a myeloma-defining event that can be attributed to the underlying plasma cell proliferative disorder (to include one or more of the following): * Hypercalcemia (corrected calcium \>2.75 mmol/L or 11.5 mg/dL); OR * Renal insufficiency attributable to myeloma (serum creatinine \> 1.9 mg/dL); OR * Anemia; normochromic, normocytic with a hemoglobin value ≥2 g/dL below the lower limit of normal, or a hemoglobin or \<10 g/dL; OR * Bone lytic lesions, severe osteopenia or pathologic fractures detected on a radiographic boney survey, OR * More than 1 myeloma-related lesion on advanced imaging, including either by magnetic resonance imaging (MRI), whole-body MRI (WB-MRI), positron emission tomography with embedded computed tomography (PET/CT), or whole-body low dose computed tomography (WB-LDCT); OR * Clonal bone marrow plasma cells ≥60%; OR * Involved/uninvolved serum free light chain ratio of 100 or more * Patients with a biopsy-proven plasmacytoma and either a serum or urine monoclonal protein will also be considered to have met the diagnostic cr…