In vivo study of Carfilzomib-Induced Neuropathy

Chemotherapy-induced peripheral neuropathy (CIPN) is a common side effect of cancer treatment with chemotherapeutic agents. 20S proteasome inhibitors such as Bortezomib (BTZ) and Carfilzomib (CFZ) have been approved for treatment of multiple myeloma and other liquid tumors, also include CIPN among their side effects. To date, no effective treatment for this condition has been developed. Observations in patients treated with these drugs showed that BTZ induces a worse neuropathic phenotype when compared with ones treated with CFZ. While the strong BTZ induced neuropathic symptoms have been replicated in a preclinical setting, there is still no preclinical animal model of CFZ-induced neuropathy. Our aim is to investigate the behavioral and morphological differences between BTZ and CFZ in terms of nerve damage and fiber loss. Therefore, we first selected a CFZ dose able to guarantee a level of anti-neoplastic activity comparable to that of BTZ in terms of proteasome inhibition as well as good tolerability for the model animals. Then, we treated the animals via intravenous administration of 0.8 mg/kg 2qwx4 of BTZ and 2 mg/kg 2qwx4 of CFZ. Here, we evaluated general toxicity over time as well as the insurgence of neuropathy and neuropathic pain using conduction velocity analyses, dynamic Von Frey tests, and evaluation of intraepidermal fibers density (IENF): all these tests show clear neuropathy developing as early as 2 weeks after the beginning of treatment with BTZ, whereas mice treated with CFZ show only mild symptoms throughout. We next sought to dissect any difference in the morphological and morphometrical features in peripheral nerves between the two treatments. We observed a clear degeneration and loss of axonal fibers in both the caudal and sciatic nerves of BTZ-treated animals, that is already evident at half-treatment (2 weeks), whereas the impact on the CFZ-treated cohort is much less severe and becomes significant only at the end of treatment (4 weeks). Taken together, these results show a clear difference in the neurotoxic symptoms between the two drugs, which reflects in the morphological and functional discrepancies. Therefore, these models are able to reproduce the clinical aspects of CIPN and pave the way for the investigation of the molecular mechanisms that underlie these differences. This work is supported by Fondazione Cariplo, grant #2019-1482.