Vinorelbine (ditartrate) is an anti-mitotic agent which inhibits the proliferation of Hela cells with IC50 of 1.25 nM.Vinorelbine (0.5-5 nM) inhibits cell proliferation by 50% (IC50) at concentrations of 1.25 nM. At concentration of 8 nM vinorelbine, no cells are in anaphase. Vinorelbine time-dependently induces the p53 and p21WAFI/CIP1 expression in androgen-dependent (AD) and- independent (AI) prostate cancer cell lines. Vinorelbine stimulates reporter genes in a concentration-dependent manner.After vinorelbine treatment, the first neutropenicepisode occurred after the first (4 dogs), second (1), or sixth(1) vinorelbine treatment in the dogs. Vinorelbine is tolerated at a weekly interval in tumor-bearing cats, with an MTD of 11.5 mg/m2.