Patient flow diagram. Of 63 patients enrolled in part A (daratumumab monotherapy), 2 patients were still on treatment at data cutoff, 14 patients were enrolled in part B (daratumumab + ATRA) phase 1, 36 patients were enrolled in part B phase 2, and 10 patients were not enrolled in part B because of ineligibility or withdrawal of informed consent. All 63 patients enrolled in part A were evaluated for safety and efficacy, all 14 patients enrolled in part B phase 1 were evaluated for the assessment of the RP2D, and all 44 patients treated at the RP2D in part B were evaluated for safety and efficacy.