Advances in vinca-alkaloids: Navelbine.
Vinorelbine (Navelbine) is a new semisynthetic vinca alkaloid which chemically differs from vinblastine by substitutions on the catharantine moiety of the molecule. It has shown promising experimental antitumor activity against experimental murine tumors as well as continuous cell lines of human neoplastic origin and human tumor xenografts in nude mice. Acute subacute and chronic toxicity extensively studied in rodents, dogs and primate has shown that hematotoxicity was almost the sole side-effect; neurotoxicity appears very limited. Almost exclusive affinity of NVB for mitotic tubulin and tubulin associated protein accounts for this pattern of toxicity. Phase I and II studies have been conducted in humans. Dose limiting side-effect appears to be neutropenia: the drug is slightly emetogenic, induces little alopecia, almost no neurotoxicity, and no other toxicity. Although preliminary, results of phase II studies already suggest significant activity of NVB in non small lung cancer (33% response rate in 78 evaluable patients), advanced breast cancer (53% response rate in 33 pts without significant chemotherapy for the target progression) and Hodgkin's disease (90% response rate after 4 weekly courses in 31 pts). Thus extensive pharmacological studies and ongoing clinical studies confirm that chemical modifications of the catharantine moiety of vinca alcaloid can lead to active agents with broader spectrum of activity and easily manageable side effects.