Expanded Access Program: Evaluating Safety of Erythrocytes Encapsulating L-Asparaginase in Combination with Polychemotherapy in Patients Under 55 Years Old with Acute Lymphoblastic Leukaemia (ALL) at Risk to Receive Other Formulations of Asparaginase

Introduction

Asparaginase is an important part of the treatment of acute lymphoblastic leukemia (ALL). Hypersensitivity is found in 16.8% of patients treated with pegylated asparaginase (PEG-asp). Hypersensitivity is the most common cause of truncated asparaginase therapy which has been associated with decreased event free survival.

Asparaginase (ASNase) encapsulated in erythrocytes (eryaspase) is an alternative formulation of ASNase aiming to prolong the half-life of ASNase and to reduce toxicity e.g. hypersensitivity, since the erythrocyte membrane protects asparaginase against elimination and prevents activation of the immune system.

In the NOR-GRASPALL 2016 trial eryaspase consistently demonstrated prolonged ASNase activity in patients who developed hypersensitivity reactions to PEG-asp. Treatment with eryaspase was well tolerated when combined with multiagent chemotherapy.

The objective of this expanded access program was to explore the tolerability of eryaspase (150 U/Kg) combined with polychemotherapy in patients under 55 years of age with ALL, unable or at risk to receive any other available ASNase formulation. Patients in this study had developed hypersensitivities to prior E-Coli- and Erwinia-derived asparaginase therapies.

Methods

This was a non-randomized, multicentre, open label, Phase 1 study to assess the limiting toxicities, global safety and biological efficacy of eryaspase in combination with chemotherapy regimens. Patients were under 55 years of age with ALL de novo or in relapse or refractory; eligible for a chemotherapy treatment including ASNase; known contraindication and/or at risk of toxicity from other ASNase formulations.

Eryaspase (150 U/Kg) was given as a replacement therapy for the remaining intended courses of asparaginase therapy. The number of courses was not defined and depended on therapeutic treatment chosen by the Investigator and the patient's response and tolerance.

The primary endpoint was the exploration of the toxicity of eryaspase defined as the number and percent of patients presenting at least one limiting toxicity (LT) of eryaspase in combination with chemotherapy. Major secondary endpoints included: adverse events (AEs), pharmacokinetics (PK), pharmacodynamics (PD) and complete remission (CR) status at end of induction and survival status up to 12 months after inclusion.

Results

Eighteen patients enrolled of which seven (38.8%) patients experienced a total of 24 AE limiting toxicities, which were primarily bone marrow failure, and were indicative of the underlying ALL disease process and of the concomitant chemotherapy-related myelosuppression.

All patients experienced at least one AE and Treatment Emergent (TEAE) and most (11 [61.1%] patients) experienced at least one SAE. A total of 17 (94.4%) patients experienced a TEAE of Grade 3 or above. No TEAEs led to withdrawal or dose reduction of eryaspase.

Sparse whole blood ASNase concentrations following 150 U/Kg were within the range of concentrations expected for this dose level. At 14 days following the first infusion, the range of whole blood ASNase was 111 to 1160 U/Kg, which would be equivalent to the trough (nadir) for infusions every 2 weeks.

Mean and median plasma asparagine (ASN) concentrations over time demonstrated a reduction by approximately 50% at 3 days post eryaspase infusion, followed by a slow return toward baseline before the next infusion of eryaspase.

Seventeen (94.4%) patients achieved CR at least once overall. Fourteen (77.8%) patients were alive at the end of the study. Survival rate was 88.9% at 6 months and 77.8% at 12 and 18 months.

Conclusion

The AE profile of eryaspase was consistent with other studies and was as expected for this cohort of patients. Serious AEs were generally consistent with those that would be expected in this study population.

A total of 17 patients in the study achieved a CR at least once overall and 14 were still alive at the end of the study.

This study evaluated additional asparaginase therapy in double (and even triple) allergic patient population, who have received prior E-Coli- or Erwinia-derived asparaginase therapy. All patients achieved target asparaginase activity. Therefore, eryaspase provides an additional option for patients for whom further ASNase treatment is contraindicated due to toxicity and/or immunization.