Patients with RARA overexpression identified with peripheral blood–based clinical trial assay. The blood-based biomarker test (clinical trial assay) was performed at a central laboratory, using frozen peripheral blood mononuclear cells (PBMCs) prepared and shipped from the clinical sites. The assay measures relative RARA mRNA expression levels against a panel of control genes via quantitative reverse transcription polymerase chain reaction (RT-qPCR) in CD34⁺ and/or CD117⁺ blasts isolated from PBMCs and applies a predefined cutoff to determine whether any given patient sample is RARA-positive or RARA-negative (patients with RARA overexpression were characterized as RARA-positive and patients without RARA overexpression as RARA-negative). ∗Details of the sample collection, sample analysis, and biomarker outcome reporting process as described in Vigil et al, 2017;⁶ †Syros Pharmaceuticals, Inc data on file as of 27 May 2022 from studies SY-1425-201 (all cohorts) and SELECT-MDS-1 (#NCT04797780). CPT, cell preparation tube.