Sustained and Prolonged Asparagine Depletion by Multiple Doses of Intravenous Pegylated Asparaginase in the Treatment of Adults with Newly Diagnosed Acute Lymphoblastic Leukemia.

The better outcome in pediatric ALL may not be solely related to the biology of the disease. Adult regimens are less intensive than used in children and include less, shorter or no use of asparaginase; the drug is often considered more toxic than in children. However, adequate serum asparagine depletion was shown to be associated with improved overall outcome. Further in several, multi-agent, large pediatric randomized trials, longer administration of asparaginase in the post remission phase and more sustained asparagine depletion resulted in better outcome. PEG-asparaginase (PEG-ASP) is a modified E.coli ASP, with less hypersensitivity reactions and longer half-life. In adults a single IV dose of PEG-ASP during induction produces long duration of asparagine depletion of up to 4 weeks, t½ = 7 days, with similar toxicity to equivalent multiple doses of E.coli ASP (Douer et al Blood 19:2744,2007). We now report the use of multiple doses of PEGASP, given during induction and throughout the post-remission phases in order to produce prolonged and sustained asparagine depletion in the context of an intensified pediatric protocol, in newly diagnosed, treatment naïve, adult ALL. Sustained asparaginase activity after the short acting E.coli ASP, can be impaired by development of neutralizing anti – asparaginase antibodies. We therefore measured the asparaginase enzymatic activity in a cohort of our patients who received PEG-ASP which in children was shown to be associated with less antibody formation (

Methods: The backbone of our protocol is an augmented BFM pediatric ALL regimen consisting of 8 cycles of multi-agent chemotherapy, followed by maintenance. PEG-ASP (2000 U/m²/dose) is given IV once on day 15 of the following cycles (total 6 doses): induction phase I (cycle 1), induction phase II (cycle 2), two cycles of consolidation (cycles 3 and 6), and two cycles of delayed re-induction (cycles 5 and 8). Since December 2006, Ph+ patients receive imatinib 600mg/daily. Asparaginase enzymatic activity was measured in samples obtained before and after PEG-ASP doses in cycles 1, 5 and 8.

Results: 41 patients, aged 19–57 (median 33) years, with precursor B cell – 36, T cell-5, Ph+ 9, were studied. Median WBC at diagnosis - 15,900/cumm (range 1,900–512,000). CR rate: 37 (95%) pts. all after induction phase I. To date 15 patients received all 6 doses of PEG-ASP, having completed all consolidation cycles. The other patients are still being treated. So far the number of PEG-ASP doses given is: 6(15pts), 3(6 pts), 2(7 pts), 1(13 pts) Fifteen patients could not continue the protocol for: allogeneic stem-cell transplantation (8), refusal (1), pancreatitis (5), grade 3 DVT(1). Two additional patients died in CR from neutropenic sepsis. Patients with elevated liver enzymes, high bilirubin, or hyperglycemia continued on the study. Total number of PEG-ASP doses was 135. No pt had an allergic reaction. The number of pts with grade 3/4 toxicities during PEG-ASP cycles were: elevated liver enzymes 24 (59%), hyperbilrubinema 8 (20%), hyperglycemia 12 (29 %), pancreatitis 6(15%), fatigue 4(10%), hypertriglyceridemia 3 (7%), catheter thrombosis- 4 (10%), neuropathy-1. All toxicities were reversible. With a median follow up of 18 months, EFS at 3 and 4 yrs is 68 % (Ph- patients 74%) and CIR is 23%. Asparaginase enzymatic activity after each dose was very long in a cohort of 19 pts with a population average of t½ = 10.99 days (peak concentration 0.88 IU/ml). All 74 specimens analyzed from this cohort of patients had significant asparaginase activity after each PEG-ASP dose, highly suggesting that none of the patients analyzed had developed neutralizing anti asparaginase antibodies. Additional patients with enzymatic measurements will be presented

Conclusions: Multiple doses of PEG-ASP IV in adults (ages 19–57 years) provide prolonged and sustained asparagine depletion and no apparent drug inactivating by antibody formation. In combination with an intensified BFM-based protocol this pediatriclike strategy is feasible, without allergic reactions, and with acceptable toxicity. Although the follow up is relatively short the EFS appears to be high. Such approach may benefit adults with ALL