e19011 Background: Venetoclax (Ven) is a BCL-2 inhibitor approved in combination with hypomethylating agents (HMAs) in newly diagnosed AML patients who are not candidates for intensive induction based on impressive response rates (CR+CRi of 66.4%) and median overall survival (14.7 months) compared to HMA therapy alone (DiNardo CD, NEJM, 2020). Ven was also used in combination with 10 days of a HMA (Decitabine) in a phase II study. In the subgroup of patients with relapsed AML, some of which previously received HMA, the ORR, CR+CRi, and median OS were 62%, 42%, and 7.8 months respectively. (DiNardo CD, Lancet, 2020). To our knowledge there are no studies specifically looking at patients with AML receiving HMA + Ven with previous exposure to a HMA agent. Methods: We conducted a single center retrospective study of AML patients who received HMA + Ven therapy after previously receiving a HMA agent. Baseline demographic, clinical, laboratory, pathology, and outcomes data were collected by retrospective chart review. Response criteria was determined by 2017 ELN recommendations. Kaplan Meier was constructed to summarize time to event data. Results: A total of 17 patients were identified that met these criteria. 7 patients (41%) had progressed on prior HMA treatment, 11 patients (65%) received prior intensive chemotherapy, and 5 patients (29%) received previous Allogenic SCT prior to HMA+Ven therapy. 10 patients (59%) had either a TP53 mutation or 17p deletion and 11 patients (65%) had complex cytogenetics (≥ 3 cytogenetic abnormalities). Other patient characteristics are included in table below. For the entire cohort, the ORR (CR, CRi, PR) was 41% and the CR/CRi rate was 6%; The ORR in the following subgroups for previous HMA failure, TP53 mutation/17p deletion, and complex cytogenetics were 14%, 30%, and 36% respectively. The median Progression free survival and overall survival for the entire cohort was 2 months (1-4 months 95% CI) and 3 months (1-5 months, 95% CI) respectively. 15 patients (88%) were deceased and all deaths were attributed to AML (12/15) or infection (3/15). None of the patients went on to receive an Allogenic SCT. Conclusions: Although a limited sample size which includes many patients with a TP53/17p aberration, complex cytogenetics, Allogenic SCT relapse, and/or heavily pre-treated AML, this data describes poor outcomes in patients receiving HMA+Ven after previous HMA exposure. Patients with previous HMA failure in particular had a poor response rate. None of the patients received 10 day decitabine and it is unclear if this had any effect on the results. It would be beneficial to supplement this data with experience from multiple centers. Patient Characteristics (N = 17).[Table: see text]

e19008 Background: The combination of the Bcl-2 inhibitor, venetoclax, with hypomethylating agents (HMA) recently emerged as an efficacious treatment for older adults with acute myeloid leukemia (AML) who are not eligible for intensive induction therapy. In a phase III randomized controlled trial of HMA +/- venetoclax, DiNardo et al demonstrated impressive composite complete response rate and complete response with incomplete recovery (CR+CRi) of 66% in the venetoclax arm as compared to 28% in the placebo arm. Despite HMA/Venetoclax being lower intensity, 83% of patients developed grade 3 hematologic adverse events, and 42% of patients experienced febrile neutropenia in the venetoclax arm, as compared to 19% in the placebo arm. In the trial, venetoclax was given continually for 28 day cycles, with some patients receiving shortened durations of venetoclax (21 days) due to toxicity. To reduce toxicity, some institutions have further limited the duration of venetoclax in cycle 1. Here, we report response rates with attenuated durations of venetoclax with HMA. Methods: We conducted a retrospective study of AML patients who received venetoclax in combination with HMA, excluding those with prior chemotherapy for AML or MDS, or previous exposure to HMA or venetoclax. Demographic, cytogenetic, pathology, and outcome data were collected including bone marrow biopsy results at diagnosis and after cycle 1 (day +28) or cycle 2 (day +56). The primary outcome was composite response rate (CR+CRi) following cycle 1 or cycle 2 defined by 2017 ELN criteria. Results: 25 patients were identified with median age of 73 (range 63-82). 9 patients received 14 or less days of venetoclax (attenuated duration): < 8 days in 1 patient and 8-14 days in 8 patients. 16 patients received 21 days or more (standard duration): 21 days in 14 patients, and 28 days in 2 patients. Of the patients who received an attenuated duration, the median age was 74 (68-82), 22% had either a TP53 mutation or deletion, 56% had complex karyotype, and 44% had received prior cytotoxic chemotherapy. Of the patients who received standard duration therapy, the median age was 71 (63-81), 44% had either a TP53 mutation or deletion, 75% had complex karyotype, and 6% had received prior cytotoxic chemotherapy. The composite response rate was 78% in the attenuated duration group and 75% in the standard duration group (p > 0.99). Conclusions: Though a limited sample size, this data suggests high response rates can be observed with attenuated courses of venetoclax. With appropriately selected patients, the feasibility of attenuated venetoclax courses could be further explored in larger prospective studies.[Table: see text]