BIOV-111 a European Phase II Trial of Clofarabine (evoltra®) in Refractory and Relapsed Childhood Acute Lymphoblastic Leukemia.

BIOV-111 is a European phase II non-randomised, open-label study of a next generation purine nucleoside analogue, clofarabine (Evoltra®), in pediatric patients with relapsed/refractory ALL. We report on the efficacy and safety data. Eligible patients (pts) had either primary refractory (2 pts) or relapsed/refractory (51 pts with ≥ 2 prior lines of treatment) ALL. Clofarabine 52mg/m2 daily × 5 days was given every 28–42 days (1 course). The primary endpoint is overall response rate (ORR) defined as either a complete response (CR) or CR without platelet recovery (CRp) after 2 courses. Adverse events (AEs) were graded according to NCI CTC (v3). Plasma, urine and intracellular clofarabine pharmacokinetics were also investigated. To date, 96 courses have been administered to 53 pts from 25 centres. The median number of prior treatments was 2 (range 1–5) and 20 pts (38%) had been previously transplanted. 8/29 pts receiving ≥2 courses responded (1CR, 7CRp) giving an ORR of 28%. Responses were observed in 14/53 (26%) pts receiving at least one course of clofarabine (6CR, 7CRp, 1 PR ). Eight (57%) responders had a prior transplant and 1 of these patients was transplanted post clofarabine. One pt with a prior transplant remains in remission at 20+ months. Four pts (1CR, 3CRp) have proceeded to transplantation. Serious adverse events (n=103) included febrile neutropenia (51/103), seizures (4/103), streptococcal septicaemia (3/103), palmo-plantar erythrodysaesthesia (2/103) and bone pain (2/103). Three hepatic events occurred (raised bilirubin, raised ALT/AST), 1 renal failure and 1 cardiac failure. AEs occurred in 4 pts. The renal and cardiac failure AE occurred in a pt with known anthracycline cardiac myopathy and renal impairment at study entry. Median end of infusion plasma clofarabine concentration (n=25) on days 1 and 2 were 1.5 (0.5–3.2) uM vs 2.0 (0.1–5.1) uM respectively (p=0.01) and were not different in pts achieving a response. Urinary clofarabine recovery on days 1, 5 and 6 (drug -free) was 48±18 %, 46±12 % and 5±3 %. Clofarabine TP analyses are ongoing. Response rates in this ongoing BIOV-111 study are consistent with the pivotal clofarabine study (CLO-212) in relapsed/refractory pediatric ALL. Notably, BIOV-111 has a lower incidence of AEs, including hepatic and renal AEs; (4% and 1% respectively vs 10% and 8% in CLO-212), possibly attributable to fewer prior treatments compared to CLO-212 (median 2 vs 3 respectively). Clofarabine achieves a significant response rate in this heavily pre-treated patient population and durable responses have been observed which may confer a survival advantage with longer follow-up.