Selection of RARA-Positive Newly Diagnosed Unfit AML Patients with Elevated RARA Gene Expression Enriches for Features Associated with Primary Resistance to Venetoclax and Clinical Response to SY-1425, a Potent and Selective RARα Agonist, Plus Azacitidine

Introduction: Super-enhancer (SE) mapping in non-APL AML patient (pt) blasts identified RARα as a novel therapeutic target in approximately 30% of pts, who have elevated RARA gene expression. It was observed that the enhancer profile of this novel pt segment, where RARA expression was elevated, overlapped with the profile of mature monocytes (McKeown, 2017). Recently, several reports describe AML with monocytic features associated with resistance to venetoclax (Ven), a BCL-2 inhibitor that has emerged as a standard of care for treatment of pts with newly diagnosed (ND) unfit AML in combination with hypomethylating agents (HMAs) (Zhang, 2018; Kuusanmäki, 2019; Pei, 2020). Approximately one-third of pts do not respond to Ven plus HMAs including azacitidine (Aza) (DiNardo, 2019 and 2020), highlighting a continuing significant unmet need in ND unfit AML. SY-1425, a potent and selective RARα agonist, is in development for non-APL AML in combination with Aza and has demonstrated clinical activity with high rates of complete remission (CR) and deep CRs in RARA-positive (RARA+) ND unfit AML (DeBotton, 2019). Based on the overlap of monocytic features with RARA gene expression, we evaluated clinical samples of pts treated with SY-1425 plus Aza to correlate features of Ven resistance with the RARA biomarker and with clinical response to SY-1425 plus Aza.