Pegaspargase Re-Challenge after Grade 2 Hypersensitivity Reaction in Childhood Acute Lymphoblastic Leukemia: Results from DFCI 16-001

Introduction: Hypersensitivity reactions with asparaginase occur frequently in pediatric patients (pts) with acute lymphoblastic leukemia (ALL). The standard approach for pts with reaction to E.coli-derived asparaginase is to switch to Erwinia asparaginase, given concern that clinical reactions reflect presence of neutralizing antibodies; however, Erwinia requires more frequent dosing and is often unavailable. Therapeutic drug monitoring allows for discrimination between pts with pegaspargase hypersensitivity who have sub-therapeutic asparaginase activity and those still able to derive therapeutic benefit from pegaspargase. We prospectively piloted re-challenging pts with pegaspargase after initial Grade 2 hypersensitivity to this agent, with premedication at re-challenge and assessment of serum asparaginase activity (SAA).

Methods: Pts aged 1 to < 22 years with newly diagnosed ALL were eligible for DFCI 16-001. Pts received 1 dose of intravenous pegaspargase during Induction, and every 2 weeks for 15 total doses in Post-Induction phases, without routine premedication. Pts were monitored during/after pegaspargase for allergy, with CTCAE version 4.0 event grading. Those with ≥Grade 3 allergy discontinued pegaspargase and were switched to Erwinia. Those with Grade 2 allergic reaction were eligible for pegaspargase re-challenge with pre-medication (acetaminophen, diphenhydramine, and hydrocortisone, or per institutional standard) and slower infusion rate. If < 50% of the intended dose had been administered when reaction occurred, re-challenge was within 1-7 days of initial reaction. If ≥ 50% of the intended dose had been given, re-challenge was at next planned pegaspargase dose. SAA was measured 1-hour, 7-days, and 14-days after the re-challenge infusion (if dose completed). If 1-hour or 7-day level ≥ 0.1 IU/mL, and 14-day level ≥ 0.025 IU/mL, SAA was considered adequate, and the pt continued to receive pegaspargase with premedication. Pts with an inadequate SAA level, or with new ≥ Grade 2 allergic reaction with the re-challenge dose were considered to have failed re-challenge and were changed to Erwinia (or enrolled on a clinical trial of recombinant crisantaspase, an alternative Erwinia preparation).

Results: Between 3/2017- 7/2020, 317 eligible pts enrolled. Overall, 81 of 299 (27%) total evaluable pts experienced a first allergic reaction to pegaspargase, 68 pts with Grade 2 reaction, 13 with Grade ≥3. During Induction, 17 of 299 (6%) evaluable pts had allergic reaction to pegaspargase; all Grade 2. Of the 17 Grade 2 reactions, 13 pts (76%) underwent re-challenge in Induction, 9 (69%) re-challenges successful and 4 failed. Post-Induction, 64 of 241 evaluable pts (27%) had a first allergic reaction; 51 Grade 2 and 13 Grade ≥3. Thirty-six of 51 (71%) pts with Grade 2 allergy during Post-Induction underwent re-challenge, as did 1 additional pt with allergy during Induction who was re-challenged with first Post-Induction pegaspargase dose (per protocol guideline, due to receiving ≥50% of Induction dose). Among these re-challenges, 16 were successful, 21 failed. Overall, 25 of 50 (50%) pts who were re-challenged after Grade 2 reaction had a successful challenge and were able to continue pegaspargase. Among the 25 pts with failed re-challenge, 6 pts (24%) had inadequate SAA alone as cause of failure, 17 pts (68%) had an allergic reaction with the re-challenge dose, and 2 (8%) additional patients had both allergic reaction and documented inadequate SAA. Three pts who were successfully re-challenged had a subsequent allergic reaction to pegaspargase. Among the 22 pts who experienced another allergic reaction with pegaspargase (at re-challenge or subsequent dose), 19 pts (86%) experienced Grade 2, and 3 pts experienced Grade 3 reaction.

Conclusion: Fifty percent of pts with a Grade 2 reaction to pegaspargase were able to tolerate and achieve adequate SAA when re-challenged with premedication. For those who did react with or after re-challenge, reactions were not more severe. The re-challenge approach limits premedication exposure only to a minority of pts with a history of prior reaction and substantially decreases the number of pts needing to switch to Erwinia asparaginase, which can be challenging to deliver due to administration schedule and drug shortage.