Arginine depletion potentiates standard-of-care chemo-immunotherapy in preclinical models of high-risk neuroblastoma

Background:
Dysregulated amino acid metabolism creates cancer-specific vulnerabilities. Neuroblastoma tumors have dysregulated arginine metabolism that renders them sensitive to systemic arginine deprivation. Arginase therapy has been proposed as a therapeutic approach for neuroblastoma treatment and has a favorable safety profile in pediatric cancer patients, however optimal therapeutic combinations remain unexplored.

Methods:
The anti-tumor effects of BCT-100, a pegylated human arginase, were studied in neuroblastoma cell models by metabolite profiling, proteomics, and viability, clonogenicity, and protein translation assays. BCT-100 efficacy was assessed in the Th-MYCN transgenic neuroblastoma mouse model and in neuroblastoma cell line and patient-derived xenograft models.

Results:
In vitro, depletion of arginine by BCT-100 arrested protein translation and cellular proliferation, with effects on clonogenicity enhanced in combination with standard-of-care chemotherapeutics SN-38/temozolomide and mafosfamide/topotecan. In vivo, BCT-100 treatment spared liver arginine while significantly depleting plasma and tumor arginine in Th-MYCN mice, and extended tumor latency (> 100 vs. 45.5 days) in mice pre-emptively treated at weaning. In mice with established tumors, BCT-100 prolonged tumor progression delay when combined with standard-of-care chemo- (> 90 vs. 25 days) or chemo-immuno-therapy (49.5 vs. 35.5 days). Tumor progression delay was also observed in cell line and patient-derived xenografts with BCT-100 treatment, including relapsed/refractory disease models. No increased toxicity was observed with the addition of BCT-100 to established therapies.

Conclusions:
The arginase BCT-100 profoundly disrupts neuroblastoma growth in vitro and in vivo, an effect enhanced in combination with standard-of-care chemo-immuno-therapy. Our data supports further assessment of arginine-depleting combination therapies as a new treatment strategy for neuroblastoma.