Phase 2 Trial Update of CPX-351 for Acute Myeloid Leukemia

Celator Pharmaceuticals announced positive survival analyses from two completed Phase 2b trials of CPX-351 (cytarabine:daunorubicin) Liposome Injection in acute myeloid leukemia (AML). A subset analysis of data from a randomized Phase 2b study in AML patients in first-relapse showed that patients with an unfavorable risk profile had significantly improved survival after treatment with CPX-351 compared to standard salvage therapies. Results from a second randomized Phase 2b study in elderly patients with newly diagnosed AML suggested that survival in patients with CRi (complete response with incomplete recovery of neutrophils or platelets) was similar to CR (complete response with complete recovery of neutrophils and platelets), an effect usually not seen with standard treatment.

A randomized, open-label Phase 2b study treated 125 patients between the ages of 18 and 65 with first relapse AML at 35 sites in North America and Europe. Patients were stratified using the European Prognostic Index (EPI) and following a 2:1 randomization, patients received CPX-351 or a salvage therapy. In this subset analysis by prognostic group, a statistically significant difference was seen in overall survival (OS) in patients with unfavorable EPI risk scores with a hazard ratio=0.55, P=0.02, and a median OS of 6.6 months following CPX-351 compared to 4.2 months in the control group.

Another randomized, open-label Phase 2b study, comparing CPX-351 to standard of care conventional cytarabine (Bedford Laboratories) and Cerubidine (daunorubicin; Bedford Laboratories) (7+3 regimen) enrolled patients between the ages of 60–75 years with newly-diagnosed AML at 18 sites in the United States and Canada. Patients were stratified as high risk (age ≥70 or secondary AML or ≥3 chromosomal abnormalities) or standard risk (all other patients). CPX-351 produced equivalent rates of CR (48.2% vs. 48.8%) but substantial increases in the percentage of patients with CRi (17.6% vs. 2.4%). The current analysis compared outcomes between CR and CRi patients who received CPX-351 and found no significant difference in survival between the two response cohorts (hazard ratio = 0.71, P=0.50), despite the fact that a greater proportion of CRi patients had adverse cytogenetics and secondary AML and also had less post-remission treatment.

CPX-351 is a combination of two drugs with synergistic anti-tumor activity (cytarabine [an antimetabolite] and daunorubicin [an anthracycline]); these drugs are encapsulated in a liposome injection drug delivery vehicle in order to maintain the desired drug molar ratio following administration.

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