High-Grade Pegylated Asparaginase-Related Hepatotoxicity Occurrence In a Pediatric-Inspired Adult Acute Lymphoblastic Leukemia Regimen Does Not Necessarily Predict Recurrent Hepatotoxicity In Subsequent Cycles

Cure rates of pediatric acute lymphoblastic leukemia (ALL) have markedly improved to approximately 80%, while in adult ALL the rates remain 40-50%. Pediatric ALL regimens contain higher doses of non-myelosuppressive chemotherapy, e.g., vincristine, corticosteroids, and, particularly, higher cumulative doses of asparaginase. Asparaginase use in adults was previously limited due to toxicity concerns. However, several recent studies, using pediatric regimens in adults, contain higher cumulative doses of asparaginase and are showing promising preliminary results. In these studies it was also noted that the long-acting pegaspargase (PEG-ASN) was much more commonly associated with hepatotoxicity in adults than in children. Although hepatotoxicity appears to be the commonest adverse effect of PEG-ASN in adults, it has not been well defined. We report the frequency and characteristics of PEG-ASN-related high-grade hepatotoxicity after multiple doses in adults treated by a pediatric regimen.

Between July 2004 and July 2009, 51 adults aged 18 to 57 years were enrolled on a phase II trial with a pediatric ALL regimen that included six planned PEG-ASN doses. PEG-ASN-related toxicities were carefully monitored on a weekly basis after each dose and reported using NCI CTCAE v3.0 for 185 doses delivered. The PEG-ASN dosing schedule was: two doses in induction phases I and II, and four during post-induction cycles (ASH Abstract 1495, 2012). Each PEG-ASN dose was 2000 IU/m²/dose IV, given at intervals of four weeks or greater. Pegaspargase was not discontinued and subsequent doses were not reduced after hepatotoxicity.

A total of 192 pegaspargase doses were delivered (3.8 doses/patient), with 23 patients receiving all six doses. Of the 28 patients who received fewer than six doses, only 10 (20%) discontinued due non-hepatic toxicity (pancreatitis, allergy, and DVT). Eight (16%) patients discontinued due to allogeneic HSCT while in CR1, while nine (18%) discontinued for other reasons (death post-induction, induction failure, and relapse). Grade 3/4 hyperbilirubinemia occurred in 16 patients (31%) and in 23 doses (12%); grade 3/4 transaminitis occurred in 33 patients (65%) and in 62 doses (34%). Patients with grade 3/4 hyperbilirubinemia tended to be older than those without hepatotoxicity (median age 39 vs 31 years), but all other baseline characteristics were similar.

Results of different parameters related to high-grade liver toxicity are detailed in Table 1. Patients with grade 3/4 hyperbilirubinemia and transaminitis received a mean of 4.0 and 4.3 PEG-ASN doses, while the mean number of PEG-ASN doses causing hyperbilirubinemia and transaminitis was only 1.4 and 1.9 doses per patient, respectively. Those without hepatotoxicity received 2.8 PEG-ASN doses per patient. Induction I had the highest incidence (20% of doses delivered) of grade 3/4 hyperbilirubinemia. High-grade transaminitis was spread more evenly among cycles. Grade 3/4 hepatotoxicity was long, with a median duration of 34 days to return to grade 1 for bilirubin and 38 days to return to grade 2 for transaminitis. Of the 16 patients with grade 3/4 hyperbilirubinemia, five did not receive a subsequent PEG-ASN dose for other reasons; of the 11 other patients who received subsequent doses, five (45%) did not re-experience the same toxicity. Of the 33 patients with grade 3/4 transaminitis, eight did not receive a subsequent PEG-ASN dose due to other reasons; of the 25 other patients who received subsequent doses, 10 (40%) did not have this toxicity recur.

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Our study shows in adults with ALL treated with multiple doses of PEG-ASN that: (1) high-grade hepatoxicity (grade 3/4 hyperbilirubinemia and transaminitis) is a common adverse effect of PEG-ASN; (2) recovery from hepatotoxicity is often long and can delay subsequent chemotherapy; (3) high-grade hepatotoxicity did not necessarily recur after subsequent doses and did not lead to PEG-ASN discontinuation; (4) the dose and schedule of other hepatically cleared or hepatotoxic drugs should be adjusted during periods of PEG-ASN-related hepatotoxicity.

In conclusion, although PEG-ASN at this dose and interval is associated in adults with a high rate of hepatotoxicity, it is tolerable and can be given again despite earlier PEG-ASN-related hepatotoxicity.

Douer:Sigma Tau Pharmaceuticals : Research Funding.