A phase Ib/II study of ivosidenib with venetoclax +/- azacitidine in IDH1-mutated myeloid malignancies.
Authors: Curtis Andrew Lachowiez, Gautam Borthakur, Sanam Loghavi, Zhihong Zeng, Tapan M. Kadia, Lucia Masarova, Koichi Takahashi, George Dono Tippett, Samantha Smith, Jacqueline Suen Garcia, Prithviraj Bose, Elias Jabbour, Farhad Ravandi, Naval Guastad Daver, Guillermo Garcia-Manero, Bilyana Stoilova, Paresh Vyas, Hagop M. Kantarjian, Marina Konopleva, Courtney Denton Dinardo
Journal: Journal of Clinical Oncology (2021)

7012 Background: Isocitrate dehydrogenase-1 ( IDH1 + ) mutations are present in 5-15% of myeloid malignancies, promoting leukemogenesis through production of the oncometabolite 2-hydroxyglutarate resulting in arrested myeloid differentiation. IDH1 + malignancies demonstrate increased reliance on the anti-apoptotic protein BCL-2, enhancing susceptibility to the BCL-2 inhibitor venetoclax (VEN). We report an interim safety and efficacy analysis of the IDH1 inhibitor ivosidenib (IVO; 500 mg PO daily D15-continuous) combined with VEN (D1-14) +/- azacitidine (AZA; 75mg/m 2 D1-7 every 28 days). Methods: Eligible patients age ≥18 with IDH1 + MDS, newly diagnosed AML (ND: treatment naïve [TN] or secondary/treated secondary AML [sAML]), or relapsed/refractory (R/R) AML enrolled into three dose levels (DL): DL1 (IVO+VEN 400 mg), DL2 (IVO+VEN 800 mg), DL3 (IVO+VEN 400 mg+AZA). Primary objectives included safety and tolerability, and IWG defined overall response (ORR: CR+CRi+CRh+PR+MLFS). Prior receipt of IVO or VEN was exclusionary. Results: 25 evaluable patients (DL1: 6, DL2: 6, DL3: 13) enrolled with a median follow-up of 16.1 months. Median age was 67 (range: 44-84). 84% (N=21) of patients had AML (ND: N=13 [TN: 8, sAML: 5], R/R: N=8), while 16% (N=4) had MDS. ELN risk was intermediate and adverse in 16% (N=4) and 56% (N=14). Median IDH1 VAF at enrollment was 22.7% (range: 5.1%-47.8%). Two patients had received a prior IDH1 inhibitor. The ORR was 92% (DL1: 67%, DL2: 100%, DL3: 100%). Composite CR (CRc: CR+CRi+CRh) was 84% (DL1: 67%, DL2: 100%, DL3: 85%) including 92% (TN: 100%, sAML: 80%), 63%, and 100% of patients with ND-AML, R/R-AML, or MDS. Median number of cycles received was 4 (DL1: 8.5, DL2: 6, DL3: 4) with ongoing responses in 62% (DL1: 33%, DL2: 50%, DL3: 82%) at 1-year. 8 patients transitioned to SCT (DL1: 0, DL2: 2, DL3: 6), and 8 patients remain on study (DL1: 2, DL2: 1, DL3: 5). 1-year OS was 68% for the entire study population (DL1: 50%, DL2: 67%, DL3: 78%), 71% in ND-AML (TN: 86%, sAML: 60%), 50% in R/R-AML, and 100% in MDS. Measurable residual disease negative CRc by multiparameter flow cytometry was attained in 60% (ND-AML: 67%, R/R-AML: 60%, MDS: 33%) correlating with improved OS (median OS: NR vs. 8.5 months, p-value: 0.038). Common grade 3/4 adverse events included febrile neutropenia (28%) and pneumonia (24%). Tumor lysis and differentiation syndrome occurred in two and four patients; all cases resolved with medical management. Conclusions: IVO+VEN +/- AZA is an effective treatment regimen in patients with IDH1 + myeloid malignancies. The combination therapy is associated with an acceptable and expected toxicity profile with notable efficacy and high rates of MRD-negative CRc in AML. Enrollment into the study continues. Clinical trial information: NCT03471260. [Table: see text]