Population pharmacokinetics of intravenous Erwinia asparaginase in pediatric acute lymphoblastic leukemia patients

Pharmacokinetics of PEGasparaginase in Infants with Acute Lymphoblastic Leukemia

BACKGROUND

PEGasparaginase is known to be a critical drug for treating pediatric acute lymphoblastic leukemia (ALL), however, there is insufficient evidence to determine the optimal dose for infants who are less than one year of age at diagnosis. This international study was conducted to identify the pharmacokinetics of PEGasparaginase in infants with newly diagnosed ALL and gather insight into the clearance and dosing of this population.

METHODS

Infants with ALL who received treatment with PEGasparaginase were included in our population pharmacokinetic assessment employing non-linear mixed effects modelling (NONMEM).

RESULTS

68 infants with ALL, with a total of 388 asparaginase activity samples, were included. PEGasparaginase doses ranging from 400 to 3,663 IU/m2 were administered either intravenously or intramuscularly. A one-compartment model with time-dependent clearance, modeled using a transit model, provided the best fit to the data. Body weight was significantly correlated with clearance and volume of distribution. The final model estimated a half-life of 11.7 days just after administration, which decreased to 1.8 days 14 days after administration. Clearance was 19.5% lower during the post-induction treatment phase compared to induction.

CONCLUSION

The pharmacokinetics of PEGasparaginase in infants diagnosed under one year of age with ALL is comparable to that of older children (1-18 years). We recommend a PEGasparaginase dosing at 1,500 IU/m2 for infants without dose adaptations according to age, and implementing therapeutic drug monitoring as standard practice.

Rituximab administration in pediatric patients with newly diagnosed acute lymphoblastic leukemia

Polyethylene glycol (PEG)-asparaginase (pegaspargase) is a key agent in chemotherapy for acute lymphoblastic leukemia (ALL), but recipients frequently experience allergic reactions. We hypothesized that by decreasing antibody-producing CD20-positive B cells, rituximab may reduce these reactions. Children and adolescents (aged 1-18 years) with newly diagnosed B-ALL treated on the St. Jude Total XVII study were randomized to induction therapy with or without rituximab on day 3 (cohort 1) or on days 6 and 24 (cohort 2). Patient clinical demographics, CD20 expression, minimal residual disease (MRD), rituximab reactions, pegaspargase allergy, anti-pegaspargase antibodies, and pancreatitis were evaluated. Thirty-five patients received rituximab and 37 did not. Among the 35 recipients, 16 (45.7%) experienced a grade 2 or higher reaction to rituximab. There were no differences between recipients and non-recipients in the incidence of pegaspargase reactions (P  >  0.999), anti-pegaspargase antibodies (P  =  0.327), or pancreatitis (P  =  0.480). CD20 expression on day 8 was significantly lower in rituximab recipients (P  <  0.001), but there were no differences in MRD levels on day 8, 15, or at the end of induction. Rituximab administration during induction in pediatric patients with B-ALL was associated with a high incidence of infusion reactions with no significant decrease in pegaspargase allergies, anti-pegaspargase antibodies, or MRD.

Multiple Asparaginase Infusions Cause Increasingly Severe Acute Hyperammonemia

Adverse reactions during and shortly after infusing asparaginase for the treatment of acute lymphoblastic leukemia can increase in severity with later doses, limiting further use and increasing relapse risk. Although asparaginase is associated with hyperammonemia, the magnitude of the increase in serum ammonia immediately after the infusion and in response to multiple infusions has not been examined. The concurrence of hyperammonemia and infusion reactions was studied using weaned juvenile pigs that received 12 infusions of Erwinia asparaginase (Erwinase; 1250 U/kg) over 28 days, with two 5-day recovery periods without asparaginase after the eighth and eleventh doses. Infusion reactions and prolonged hyperammonemia (>50 µM ammonia 48 h after the infusion) began after the fourth dose and increased with later doses. Dense sampling for 60 min revealed an acute phase of hyperammonemia that peaked within 20 min after starting the first infusion (298 + 62 µM) and lasted less than 1 h, without apparent symptoms. A pronounced acute hyperammonemia after the final infusion (1260 + 250 µM) coincided with severe symptoms and one mortality during the infusion. The previously unrecognized acute phase of hyperammonemia associated with asparaginase infusion coincides with infusion reactions. The juvenile pig is a translational animal model for understanding the causes of acute and chronic hyperammonemia, differentiating from hypersensitivity reactions, and for improving infusion protocols to reduce acute hyperammonemia and to allow the continued use of asparaginase.

Current Use of Asparaginase in Acute Lymphoblastic Leukemia/Lymphoblastic Lymphoma

Pediatric Acute Lymphoblastic Leukemia (ALL) cure rates have improved exponentially over the past five decades with now over 90% of children achieving long-term survival. A direct contributor to this remarkable feat is the development and expanded understanding of combination chemotherapy. Asparaginase is the most recent addition to the ALL chemotherapy backbone and has now become a hallmark of therapy. It is generally accepted that the therapeutic effects of asparaginase is due to depletion of the essential amino acid asparagine, thus occupying a unique space within the therapeutic landscape of ALL. Pharmacokinetic and pharmacodynamic profiling have allowed a detailed and accessible insight into the biochemical effects of asparaginase resulting in regular clinical use of therapeutic drug monitoring (TDM). Asparaginase's derivation from bacteria, and in some cases conjugation with a polyethylene glycol (PEG) moiety, have contributed to a unique toxicity profile with hypersensitivity reactions being the most salient. Hypersensitivity, along with several other toxicities, has limited the use of asparaginase in some populations of ALL patients. Both TDM and toxicities have contributed to the variety of approaches to the incorporation of asparaginase into the treatment of ALL. Regardless of the approach to asparagine depletion, it has continually demonstrated to be among the most important components of ALL therapy. Despite regular use over the past 50 years, and its incorporation into the standard of care treatment for ALL, there remains much yet to be discovered and ample room for improvement within the utilization of asparaginase therapy.

How much asparaginase is needed for optimal outcome in childhood acute lymphoblastic leukaemia? A systematic review

This review focuses on asparaginase, a key component of childhood acute lymphoblastic leukaemia (ALL) treatment since the 1970s. This review evaluates how much asparaginase is needed for optimal outcome in childhood ALL. We provide an overview of asparaginase dose intensity, i.e. duration of total cumulative exposure in weeks and level of exposure reflected by dose and/or asparaginase activity level, and the corresponding outcome. We systematically searched papers published between January 1990 and March 2021 in the PubMed and MEDLINE databases and included 20 papers. The level and duration of exposure were based on the pharmacokinetic profile of the drug and the assumption that trough asparaginase activity levels of ≥100 IU/L should be achieved for complete l-asparagine depletion. The statistical meta-analysis of outcomes was not performed because different outcome measures were used. The level of exposure was not associated with the outcome as long as therapeutic asparaginase activity levels of ≥100 IU/L were reached. Conflicting results were found in the randomised controlled trials, but all truncation studies showed that the duration of exposure (expressed as weeks of l-asparagine depletion) does affect the outcome; however, no clear cutoff for optimal exposure duration was determined. Optimal exposure duration will also depend on immunophenotype, (cyto)genetic subgroups, risk group stratification and backbone therapy.

Population Pharmacokinetic Model Development and Simulation for Recombinant Erwinia Asparaginase Produced in Pseudomonas fluorescens (JZP-458)

JZP‐458 is a recombinant Erwinia asparaginase produced using a novel Pseudomonas fluorescens expression platform that yields an enzyme expected to lack immunologic cross‐reactivity to Escherichia coli–derived asparaginases. It is being developed as part of a multiagent chemotherapeutic regimen to treat acute lymphoblastic leukemia or lymphoblastic lymphoma patients who develop E coli–derived asparaginase hypersensitivity. A population pharmacokinetic (PopPK) model was developed for JZP‐458 using serum asparaginase activity (SAA) data from a phase 1, single‐dose study (JZP458‐101) in healthy adults. Effects of intrinsic covariates (body weight, body surface area, age, sex, and race) on JZP‐458 PK were evaluated. The model included SAA data from 24 healthy adult participants from the phase 1 study who received JZP‐458: intramuscular (IM) data at 12.5 mg/m² (N = 6) and 25 mg/m² (N = 6), and intravenous (IV) data at 25 mg/m² (N = 6) and 37.5 mg/m² (N = 6). Model simulations of adult and pediatric SAA profiles were performed to explore the likelihood of achieving a therapeutic target nadir SAA (NSAA) level ≥0.1 IU/mL based on different administration strategies. PopPK modeling and simulation suggest JZP‐458 is expected to achieve 72‐hour NSAA levels ≥0.1 IU/mL in 100% of adult or pediatric populations receiving IM administration at 25 mg/m², and in 80.9% of adult and 94.5% of pediatric populations receiving IV administration at 37.5 mg/m² on a Monday/Wednesday/Friday (M/W/F) dosing schedule. Based on these results, the recommended starting dose for the phase 2/3 pivotal study is 25 mg/m² IM or 37.5 mg/m² IV on a M/W/F dosing schedule in pediatric and adult patients.

Adequate asparaginase is important to prevent central nervous system and testicular relapse of pediatric Philadelphia chromosome-negative B-cell acute lymphoblastic leukemia

Asparaginase (Asp) is one of the most important drugs for treating acute lymphoblastic leukemia (ALL). However, off-protocol Asp administration (OPAA) or hypersensitivity may disturb its pharmacokinetic profile. In this retrospective study, we sought to determine whether OPAA and hypersensitivity to Escherichia coli asparaginase (E coli Asp) impaired extramedullary relapse prevention in a pediatric ALL cohort treated according to SCMC-ALL-2005 protocol from 2005 to 2014 at the Shanghai Children's Medical Center (SCMC). In total, 676 patients were enrolled in this study, including 369 with OPAA and 60 exhibiting hypersensitivity to E coli Asp. At the end of the most recent follow-up, 58 patients had extramedullary relapse. The 5-year cumulative extramedullary relapse incidence in patients with OPAA was 11.01%, whereas that in patients without OPAA was 5.28% (P = .0036). Moreover, the 5-year cumulative extramedullary relapse incidence in patients that exhibited hypersensitivity to E coli Asp was 16.48%, whereas that in patients without hypersensitivity was 7.59% (P = .0195). Concerning the relapse site, OPAA not only increased central nervous system (CNS) relapse but testicular relapse as well. Based on Fine and Gray multivariate analysis, OPAA and hypersensitivity to Asp were independent risk factors for extramedullary relapse. In conclusion, to prevent extramedullary relapse of ALL, adequate duration to administrate Asp was more important than the total dosage, and more attention should be paid to Asp inadequate due to hypersensitivity.

Individualized dosing guidelines for PEGasparaginase and factors influencing the clearance: a population pharmacokinetic model

Considerable inter- and intra-patient variability exist in serum activity levels of PEGasparaginase, essential for pediatric acute lymphoblastic leukemia treatment. A population pharmacokinetic (popPK) model was developed, identifying patient characteristics explaining these variabilities. Patients (n=92) were treated according to the DCOG ALL-11 protocol, using therapeutic drug monitoring to individualize the PEGasparaginase doses. Non-linear mixed effects modeling (NONMEM) was used to analyze the popPK evaluating several covariates. The final model was validated using an independent database (n=28). Guidelines for starting doses and dose adjustments were developed. A one-compartment model with time-dependent clearance adequately described the popPK. Normalization of clearance and volume of distribution by body surface are (BSA) reduced inter-individual variability. Clearance was 0.084 L/day/m2 for 12.7 days, increasing with 0.082 L/day/m2/day thereafter. Clearance was 38% higher during an infection, and 11-19% higher during induction treatment than intensification and maintenance (p<0.001). Targeting an asparaginase activity level of 100 IU/L, a loading dose of 800 IU/m2 (induction) and 600 IU/m2 (intensification) is advised. In conclusion, variability of PEGasparaginase activity levels can be explained by BSA, treatment phase and the occurrence of an infection. With this popPK model, PEGasparaginase treatment can be individualized further, taking into account these covariates and the dosing guidelines provided.

Higher plasma asparaginase activity after intramuscular than intravenous Erwinia asparaginase

It is unclear if dosing intervals for Erwinase can be extended with intramuscular (i.m.) versus intravenous (i.v.) dosing. Children with acute lymphoblastic leukemia received Erwinase at 30 000-42 000 IU/m² i.v. or i.m. I.m. Erwinase (n = 22) achieved activity above 0.1 IU/mL for longer than i.v. Erwinase (n = 33) (3.4 vs 2.9 days, P = 0.0007). With 30 000 IU/m² Monday, Wednesday, Friday, more patients achieved adequate concentrations over the weekend with i.m. vs i.v. dosing (P = 5 × 10^-36 ). A schedule with i.v. doses on Monday and Wednesday and i.m. doses on Friday of 30 000 IU/m² maintained activity > 0.1 IU/mL over the weekend in 80% of patients.

Pharmacokinetics and population pharmacokinetics in pediatric oncology

Pharmacokinetic research has become increasingly important in pediatric oncology as it can have direct clinical implications and is a crucial component in individualized medicine. Population pharmacokinetics has become a popular method especially in children, due to the potential for sparse sampling, flexible sampling times, computing of heterogeneous data, and identification of variability sources. However, population pharmacokinetic reports can be complex and difficult to interpret. The aim of this article is to provide a basic explanation of population pharmacokinetics, using clinical examples from the field of pediatric oncology, to facilitate the translation of pharmacokinetic research into the daily clinic.

Individualized Asparaginase Dosing in Childhood Acute Lymphoblastic Leukemia

PURPOSE

In the DCOG ALL-11 protocol, polyethylene glycol-conjugated Escherichia coli asparaginase (PEGasparaginase) and Erwinia asparaginase treatment of pediatric acute lymphoblastic leukemia are individualized with therapeutic drug monitoring (TDM). The efficacy of TDM and its effect on asparaginase-associated toxicity are reported.

PATIENTS AND METHODS

After induction with 3 fixed intravenous doses of 1,500 IU/m² PEGasparaginase, medium-risk patients (n = 243) received 14 individualized doses that targeted trough levels of 100-250 IU/L, standard-risk patients (n = 108) received 1 individualized dose, and high-risk patients (n = 18) received 2-5 fixed administrations (1,500 IU/m²). After a neutralizing hypersensitivity reaction, patients were started with 20,000 IU/m² Erwinia asparaginase 3 times per week, and l-asparagine was measured to monitor asparaginase efficacy. Several asparaginase-associated toxicities were studied.

RESULTS

The final median PEGasparaginase dose was lowered to 450 IU/m². Overall, 97% of all trough levels of nonallergic patients were > 100 IU/L. Asparagine was < 0.5 μM in 96% and 67% of the PEGasparaginase and Erwinia asparaginase levels > 100 IU/L, respectively. Ten percent developed a neutralizing hypersensitivity reaction to PEGasparaginase, of which 40% were silent inactivations. The cumulative incidence of grade 3-4 pancreatitis, central neurotoxicity, and thromboses was 12%, 4%, and 6%, respectively, and not associated with asparaginase activity levels. During medium-risk intensification, 50% had increased ALT and 3% hyperbilirubinemia (both grade 3/4 and correlated with asparaginase activity levels), and 37% had grade 3/4 hypertriglyceridemia. Hypertriglyceridemia occurred less in intensification compared with ALL-10 (37% v 47%), which is similar to ALL-11 but with higher asparaginase levels during intensification.

CONCLUSION

TDM of asparaginase results in a significant reduction of the PEGasparaginase dose with adequate asparaginase activity levels and sufficient asparagine depletion. In addition, with TDM, silent inactivation and allergic-like reactions were identified. However, the effect of reduced asparaginase activity levels on toxicity is limited.