An in vivo genome-wide CRISPR screen identifies the RNA-binding protein Staufen2 as a key regulator of myeloid leukemia.

Aggressive myeloid leukemias such as blast crisis chronic myeloid leukemia and acute myeloid leukemia remain highly lethal. Here we report a genome-wide in vivo CRISPR screen to identify new dependencies in this disease. Among these, RNA-binding proteins (RBPs) in general, and the double-stranded RBP Staufen2 (Stau2) in particular, emerged as critical regulators of myeloid leukemia. In a newly developed knockout mouse, loss of Stau2 led to a profound decrease in leukemia growth and improved survival in mouse models of the disease. Further, Stau2 was required for growth of primary human blast crisis chronic myeloid leukemia and acute myeloid leukemia. Finally, integrated analysis of CRISPR, eCLIP and RNA-sequencing identified Stau2 as a regulator of chromatin-binding factors, driving global alterations in histone methylation. Collectively, these data show that in vivo CRISPR screening is an effective tool for defining new regulators of myeloid leukemia progression and identify the double-stranded RBP Stau2 as a critical dependency of myeloid malignancies.

Phase II, multicenter, randomized trial of CPX-351 (cytarabine:daunorubicin) liposome injection versus intensive salvage therapy in adults with first relapse AML.

BACKGROUND: CPX-351 is a liposome-encapsulated fixed-molar-ratio formulation of cytarabine and daunorubicin that exploits molar ratio-dependent drug-drug synergy to enhance antileukemic efficacy. METHODS: This phase II study randomized 125 patients 2:1 to CPX-351 or investigators' choice of first salvage chemotherapy. Patients with acute myeloid leukemia (AML) in first relapse after initial Complete Remission (CR) lasting ≥1 month were stratified per the European Prognostic Index (EPI) into favorable, intermediate, and poor-risk groups based on duration of first CR, cytogenetics, age, and transplant history. Control salvage treatment was usually based on cytarabine and anthracycline, often with 1 or more additional agents. Survival at 1 year was the primary efficacy end point. RESULTS: Patient characteristics were well balanced between the 2 study arms. Improvements in efficacy outcomes were observed following CPX-351, but did not meet prospectively defined statistical criteria for 1-year survival improvement in the overall population. Subset analyses of the EPI-defined poor-risk strata demonstrated higher response rates (39.3% vs 27.6%) and improvements in event-free survival (HR, 0.63; P = .08) and overall survival (HR, 0.55; P = .02). Also, 60-day mortality was lower in the CPX-351 study arm for poor-risk patients (16.1% vs 24.1%). CONCLUSIONS: Taken together, the data suggest possible improved outcomes in CPX-351-treated first relapse AML patients with EPI-defined poor-risk disease.