CHICAGO – Administering CPX-351 prior to a three-drug regimen produced a high response rate in pediatric patients with acute myeloid leukemia (AML) in first relapse.
Jennifer Smith/MDedge News
Dr. Todd Cooper
In a phase 1/2 trial, CPX-351 followed by fludarabine, cytarabine, and filgrastim (FLAG) produced an overall response rate of 81%, and 70% of responders had their best response while receiving CPX-351.
“This is the best response rate published in North America for those [pediatric AML patients] in first relapse,” said Todd Cooper, DO, of Seattle Children’s Hospital in Washington.
Dr. Cooper presented results from the phase 1/2 AAML1421 trial (NCT02642965) at the annual meeting of the American Society of Clinical Oncology.
The primary objective of phase 1 was to determine the recommended phase 2 dose and toxicities of CPX-351, a liposomal preparation of cytarabine and daunorubicin. The primary objective of phase 2 was to assess the best response in patients who received CPX-351 in cycle 1 and FLAG in cycle 2.
The trial enrolled 38 AML patients, 6 in the dose-finding phase and 32 in the efficacy phase. The patients’ median age at study entry was 11.91 years (range, 1.81-21.5). Most patients (88.9%) had CNS 1 disease, and most (73.7%) had not received a transplant.
Half of patients had a first complete response (CR) that lasted 180 to 365 days, 13.2% had a first CR lasting less than 180 days, and 36.8% had a first CR lasting more than 1 year.
Dosing and toxicity
During the dose-finding portion of the study, the first dose level of CPX-351 was 135 units/m2 on days 1, 3, and 5. There was one dose-limiting toxicity — grade 3 decrease in ejection fraction — so 135 units/m2 was deemed the recommended phase 2 dose.
The most common grade 3 or higher adverse events observed with CPX-351 in cycle 1 were infections and infestations (47.4%), febrile neutropenia (44.7%), maculopapular rash (39.5%), and prolonged QT interval (18.4%).
The most common grade 3 or higher adverse events observed with FLAG in cycle 2 were febrile neutropenia (23.1%), prolonged QT interval (23.1%), and infections and infestations (19.2%).
Response and survival
There were 37 patients evaluable for response. The overall response rate was defined as CR plus CR without platelet recovery (CRp) plus CR with incomplete hematologic recovery (CRi).
The overall response rate was 81.1% (n = 30), which included 20 CRs (54.1%), 5 CRps (13.5%), and 5 CRis (13.5%). Five patients had a partial response (13.5%), and two patients had treatment failure (5.4%).
During CPX-351 treatment (n = 37), the CR rate was 37.8% (n = 14), the CRp rate was 5.4% (n = 2), and the CRi rate was 32.4% (n = 12).
During FLAG treatment (n = 27), the CR rate was 48.1% (n = 13), the CRp rate was 25.9% (n = 7), and the CRi rate was 7.4% (n = 2).
Of the 25 patients who achieved a CR or CRp at any time, 21 (84%) were minimal residual disease negative by flow cytometry. Twelve patients were minimal residual disease negative after cycle 1.
Most patients who achieved a CRi or better (83.3%) went on to hematopoietic stem cell transplant.
The 2-year overall survival was 47% for all patients and 60% for responders. None of the non-responders were still alive 2 years after therapy.
“The results certainly warrant a phase 3 study of CPX-351,” Dr. Cooper said. “In fact, it is the lead molecule that’s going to be incorporated into the next COG phase 3 study.”
AAML1421 was sponsored by the Children’s Oncology Group in collaboration with the National Cancer Institute. Dr. Cooper disclosed relationships with Juno Therapeutics and Celgene.
SOURCE: Cooper TM et al. ASCO 2019. Abstract 10003.