Apixaban Is Effective and Safe in Reducing Venous Thromboembolism (VTE) in Obese Patients with Newly Diagnosed Pediatric Acute Lymphoblastic Leukemia/Lymphoblastic Lymphoma (ALL/LL) a Sub-Study Analysis of the Prevapix-ALL/Children's Oncology Group ACCL1333 Trial

Abstract

Background: Pediatric patients with ALL/LL are at increased risk for VTE and obesity further increases VTE risk. Pediatric ALL/LL patients experiencing VTE have increased risk for mortality as compared to ALL/LL patients without VTE. Therefore, effective and safe pharmacologic VTE prevention options are urgently needed. The PREVAPIX-ALL trial was a multi-center, multinational, randomized, open-label, controlled trial assessing the safety and efficacy of primary prophylaxis using apixaban for the prevention of VTE in pediatric patients with ALL/LL. PREVAPIX-ALL was a collaboration between the Bristol Myers Squibb/Pfizer Alliance and the Children's Oncology Group. Patients with ALL/LL undergoing induction chemotherapy containing asparaginase therapy were randomized to either apixaban or standard of care (SOC - no anticoagulation). The objective of the current study was to separately analyze obese patients as a subgroup of the PREVAPIX-ALL trial. Aims: To assess the efficacy and safety of prophylactic apixaban vs. SOC for VTE prevention during induction chemotherapy in obese pediatric patients with ALL/LL. Methods: Obesity was defined as ≥ 95 th percentile for age and sex specific body mass index as per the Centers for Disease Control and Prevention childhood obesity definition. Patients newly diagnosed with ALL/LL, ages ≥ 1 to < 18 years, with a central venous line, and on induction chemotherapy with asparaginase were randomized to apixaban vs. SOC. Apixaban thromboprophylaxis was administered at a fixed dose per body weight until the end of induction when participants were screened for VTE. The primary efficacy outcome was a composite of symptomatic and asymptomatic VTE. The primary safety outcome was major bleeding, and the secondary safety outcome was a composite of major and clinically relevant non-major (CRNM) bleeding. Results: Out of 512 PREVAPIX-ALL participants, 498 (97.2%) were age 24 months or older with weight and height available. Of those, 82 were obese. Forty-two were randomized to apixaban and 40 were randomized to SOC (Table 1). For the primary efficacy outcome there was a statistically significant decrease in VTE events in the apixaban arm, 1/42 (2.4%) compared to the SOC arm 10/40 (25%) [RRR 91% (95% CI 3%, 99%) p 0.0067] (Table 2). No statistically significant difference was observed in bleeding between the two groups (Table 2). The mean apixaban exposure was similar among the obese and non-obese groups: obese apixaban mean exposure (SD) 23.4 days (5.55) and non-obese 23.5 days (6.44). No statistical difference was observed in the median steady-state area under the curve (AUC-TAU ng.h/mL) drug exposure between obese and non-obese categories stratified by age group on a linear scale: obese (n=38) 686.94 ng.h/mL (95% CI 397.8-1314.6) and non-obese (n=186) 663.50 ng.h/mL (95% CI 319.1-1090.9). Conclusion: Apixaban VTE prophylaxis in obese ALL/LL patients receiving asparaginase during induction chemotherapy resulted in a statistically significant 91% RRR in VTE compared to SOC. No statistical difference was observed in apixaban exposure days and AUC/TAU between obese and non-obese patients. Bleeding events were not increased in the apixaban arm as compared to SOC. Primary prophylaxis using apixaban safely reduces VTE in obese ALL/LL pediatric patients receiving induction chemotherapy containing asparaginase.