A phase 1 study of the amino acid modulator pegcrisantaspase and venetoclax for relapsed/refractory acute myeloid leukemia

• Pegcrisantaspase (PegC) significantly decreased plasma glutamine, and in combination with venetoclax (Ven), disrupted mRNA translation.

• VenPegC induced complete remission in heavily pretreated AML patients who had progressed on prior venetoclax.

Glutamine dependency has been shown to be a metabolic vulnerability in acute myeloid leukemia (AML). Prior studies using several in vivo AML models showed that depletion of plasma glutamine induced by the long-acting crisantaspase (pegcrisantaspase or PegC) was synergistic with the BCL-2 inhibitor venetoclax (Ven), resulting in significantly reduced leukemia burden and enhanced survival. Here, we report a phase 1 study (NCT04666649) of Ven and PegC combination (VenPegC) for treating adult patients with relapsed or refractory AML, including patients who had previously received Ven. The primary endpoints were incidence of regimen limiting toxicities (RLT) and maximum tolerated dose (MTD). Twenty-five patients received at least one PegC dose with Ven and 18 efficacy-evaluable patients completed at least one VenPegC cycle; 12 (67%) had previously received Ven. Hyperbilirubinemia was the RLT and occurred in 60% of patients treated with VenPegC; 20% had Grade ≥3 bilirubin elevations. MTD was determined to be Ven 400 mg daily with biweekly PegC 750 IU/m2. The most common treatment-related adverse events of any Grade in 25 patients who received VenPegC included antithrombin III decrease (52%), elevated transaminases (36-48%), fatigue (28%), and hypofibrinogenemia (24%). No thromboembolic or hemorrhagic adverse events or clinical pancreatitis were observed. The overall complete remission rate in efficacy-evaluable patients was 33%. Response correlated with alterations in proteins involved in mRNA translation. In patients with RUNX1 mutations, the composite complete rate was 100%.