Randomized Study of Pegasparagase (SS-PEG) and Calaspargase Pegol (SC-PEG) in Pediatric Patients with Newly Diagnosed Acute Lymphoblastic Leukemia or Lymphoblastic Lymphoma: Results of DFCI ALL Consortium Protocol 11-001

Lewis B. Silverman, Traci M. Blonquist, Sarah K. Hunt, Samantha Kay-Green, Uma H. Athale, Luis A. Clavell, Peter D. Cole, Kara M. Kelly, Caroline Laverdiere, Jean-Marie Leclerc, Bruno Michon, Marshall A. Schorin, Maria Luisa Sulis, Jennifer J.G. Welch, Jeffrey G. Supko, Xiaoyong He, Sarah Hilderbrand, Andrew E. Place, Lynda M. Vrooman, Marian H. Harris, Kristen E. Stevenson, Donna S. Neuberg and Stephen E. Sallan


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Background: E.coli L-asparaginase (L-ASP) is an important component of treatment for childhood acute lymphoblastic leukemia (ALL), but the optimal preparation and dosing remain to be determined. Pegaspargase (SS-PEG) is a pegylated L-ASP formulation commonly used in frontline therapy. Calaspargase pegol (SC-PEG) is a novel formulation that uses the same ASP enzyme and PEG moiety as SS-PEG but a different linker molecule that is more hydrolytically stable, leading to a longer half-life. On Dana-Farber Cancer Institute (DFCI) ALL Consortium protocols, patients (pts) typically receive a single dose SS-PEG during induction, and then 15 doses every 2-weeks (wks) during post-induction in order to maintain therapeutic serum asparaginase activity (SAA), defined as ≥ 0.1 IU/mL, for 30 consecutive wks. We hypothesized that SC-PEG could be administered less frequently than SS-PEG during post-induction therapy with a similar SAA and toxicity profile.

Methods: Between 2012-2015, pts aged 1-21 years with newly diagnosed ALL or lymphoblastic lymphoma (LL) were eligible to enroll on DFCI ALL Consortium Protocol 11-001. Pts were randomized at study entry to receive either SS-PEG (N=120) or SC-PEG (N=119), each given intravenously (IV) at a dose of 2500 IU/m2. Both groups received a single dose during multi-agent remission induction. Post-induction, pts assigned to SS-PEG received 15 doses every 2-wks and those assigned to SC-PEG received 10 doses every 3-wks along with other risk-stratified chemotherapy. Serum samples were obtained 4, 11, 18 and 25 days after the induction dose to determine SAA and prior to each post-induction dose (2 wks after each SS-PEG and 3 wks after each SC-PEG dose) to determine nadir SAA (NSAA) by a validated biochemical assay. Pts were switched to Erwinia asparaginase for Grade 2 or higher allergy or for silent inactivation (defined as 2 consecutive non-detectable NSAA). Asparaginase was permanently discontinued for pancreatitis and held for thrombosis (but re-started once the clot improved). End-induction minimal residual disease (MRD) was assessed in ALL pts by IGH/TCRPCR assay, with low MRD defined as < 0.001.

Results: 239 eligible pts were enrolled (230 ALL and 9 LL). There were no significant differences in presenting characteristics between randomized arms. SAA during induction and NSAA during post-induction are displayed in Figure 1. SAA was similar for the two preparations at 4, 11 and 18 days after the induction dose, with SAA ≥ 0.1 IU/mL in ≥ 95% of pts at these time points on both arms. 25 days after the induction dose, SAA was higher with SC-PEG (median 0.298 IU/mL vs 0.056 for SS-PEG), with significantly more pts on SC-PEG arm with SAA ≥ 0.1 IU/mL (88% vs 15%, p<0.0001). Post-induction NSAA was similar between arms, with median NSAA ≥ 1.0 IU/mL (10-times higher than goal NSAA) at 7, 13, 19 and 25 wks after beginning the 30-wk post-induction asparaginase treatment. NSAA was ≥ 0.1 IU/mL in ≥ 98% of pts on both arms at each time point. Two pts on the SC-PEG arm (1.7%) and none on the SS-PEG arm met criteria for silent inactivation. There was no significant difference in rates of ASP-related allergy (p=1.00), pancreatitis (p=1.00), thrombosis (p=0.22) or infections (p=0.86) during induction or post-induction treatment (Table 1). Of 230 evaluable pts, 97% achieved CR, with no difference in proportion of pts with low end-induction MRD by randomized arm (91% SC-PEG vs 90% SS-PEG, p=1.00).

Conclusion: During remission induction, a single dose of SC-PEG (2500 IU/m2) leads to more sustained SAA without excess toxicity or significant difference in the proportion of pts with low end-induction MRD. During post-induction therapy, SC-PEG can be given less frequently (every 3-wks) than SS-PEG (every 2-wks) with similar NSAA and toxicity. The high NSAA observed during post-induction therapy with each preparation suggests that a longer dosing interval and/or reduced dose may be feasible while still maintaining NSAA ≥ 0.1 IU/mL. Longer follow-up is necessary to determine event-free survival by randomized arm.

Disclosures No relevant conflicts of interest to declare.

  • * Asterisk with author names denotes non-ASH members.

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