Phase 1/2 study of CPX-351 for patients with Int-2 or high risk International Prognostic Scoring System myelodysplastic syndromes and chronic myelomonocytic leukaemia after failure to hypomethylating agents.

Failure after hypomethylating agents (HMAs) is associated with dismal outcomes in higher risk myelodysplastic syndromes (HR-MDS) or chronic myelomonocytic leukaemia (CMML). We aimed to evaluate the safety and preliminary activity of lower doses of CPX-351, a liposomal encapsulation of cytarabine and daunorubicin, in a single-centre, phase 1/2 study for patients with HR-MDS or CMML after HMA failure. Four doses of CPX-351 (10, 25, 50 and 75 units/m 2 ) administered on Days 1, 3 and 5 of induction and Days 1 and 3 of consolidation were evaluated. Between June 2019 and June 2023, 25 patients were enrolled (phase 1: n = 15; phase 2: n = 10) including 19 (76%) with HR-MDS and 6 (24%) with CMML. Most common grade 3-4 non-haematological treatment-emergent adverse events were febrile neutropenia (n = 12, 48%) and lung infection (n = 5, 20%). Three patients (age >75) experienced cardiac toxicity at the 75 units/m 2 dose. Further enrolment continued at 50 units/m 2 . Four- and 8-week mortality were 0% and 8% respectively. The overall response rate was 56% with median relapse-free and overall survivals of 9.2 (95% CI 3.2-15.1 months) and 8.7 months (95% CI 1.8-15.6 months) respectively. These data suggest that lower doses of CPX-351 are safe. Further studies are needed to evaluate its activity.