A Phase II Study of Twice Daily Cytarabine and Fludarabine and Gentuzumab Ozogamycin (GO) In Patients (pts) with Acute Myeloid Leukemia (AML) and High-Risk Myelodysplastic Syndrome (MDS)

Treatment options for pts with refractory/relapsed (R/R) AML are limited. High dose cytarabine (A) containing regimens are still considered standard options for pts with AML relapsing after a first complete remission (CR) lasting more than 12 months. The combination of A with fludarabine (F) was found to be superior to A alone in this setting, particularly when administered twice daily (BID). In addition, gemtuzumab ozogamicin (GO) has been shown to be active in combination or as single agent in pts with R/R AML. Therefore, we conducted a phase II study assessing the efficacy and safety of BID FA-GO.

Pts with R/R AML, de novo AML patients unfit for other medical therapies, intermediate-2 and high-risk MDS, and chronic myeloid leukemia in myeloid blast crisis (CML-BC), with a performance status (PS) of 3 or less, as well as normal organ functions were eligible. Pts were scheduled to receive F 15 mg/m² IV q12 hrs day 1 to 5 as well as A at the dose of 0.5 g/m² IV over 2 hrs q12 hrs day 1 to 5. GO was administered at the dose of 3 mg/m² IV on day 1. Treatment course was shortened to 4 days in pts older than 65 years and to 3 days in pts with a PS of 3. Courses were repeated every 4 to 6 weeks for a maximum of 7 courses. Pts with CML were allowed to receive concomitant tyrosine kinase inhibitors.

Sixty-five evaluable pts were enrolled: 6 (9%) with de novo AML, 5 (8%) with AML in first relapse with a duration of 1st CR (CRD1) of ≥12 months, 21 (32%) with AML with CRD1 <12 months, 24 (37%) with AML in second relapse and beyond, 3 (5%) with MDS, and 6 (9%) with CML-BC. Median age was 60 years (range, 19 to 80); 58 pts (89%) had a PS ≥1. Cytogenetic analyses were abnormal in 63 % including chromosomes 5 and 7 abnormalities in 17%. The overall response (OR) rate was 31% including CR in 17 pts (26%) and CR without platelet recovery (CRp) in 3 (5%). The overall 4-week mortality rate was 8%. The OR rates for pts with de novo AML, relapsed AML with CRD1 ≥12 months, relapsed AML with CRD1< 12 months, and R/R AML beyond first salvage (S) were 43%, 60%, 35%, and 19%, respectively. The CR rates were 29%, 60%, 27%, and 19%, respectively. The 4-week mortality rates were 19% for pts with R/R AML beyond the first salvage and 0% for the rest (Table1). With a median follow-up of 8 months (range, 1 to 27), the 16-week event-free survival (EFS), overall survival (OS), and complete remission duration (CRD) rates were 25%, 61%, and 89%, respectively. The median EFS and OS for the responding pts were 27 weeks (4-31 weeks). When compared to historical match cohort pts treated at our institution, BID FA-GO was better, with an ORR rate of 60 % in pts with AML in first relapse with CRD1 ≥12 months compared to an expected rate of 50%, 19% in pts with relapsed AML with CRD1< 12 months compared to 11%, and 35% in pts with AML beyond the first salvage compared to 7% (Table 2). The treatment was well tolerated with only 3% of the pts experiencing grade 3 and 4 toxicities including mainly skin rash. The main toxicities were of gastro-intestinal origin and all were of grade 1 and 2. There was no case of veno-occlusive disease reported.

BID FA-GO appears to be active with an ORR of 31% in heavily pre- treated population. This combination appears to be safe as well with a low rate of 4-week-mortality of 5%. Ongoing studies are exploring the role of the new generation of nucleoside analogues in this setting.

Cortes: Pfizer: Consultancy, Research Funding.