Animal experiment:

As defined by the study, VRL1 is diluted in 0.9% NaCl to a concentration of 1.5 mg/mL, and given IV over 5 minutes. The intended treatment interval is 7 days for up to 4 treatments. After receiving 4 weekly doses, cats are eligible to continue VRL treatment every 2 weeks at the owner's expense.

Vinorelbine 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[1]. 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[2].

After vinorelbine treatment, the first neutropenicepisode occurred after the first (4 dogs), second (1), or sixth(1) vinorelbine treatment in the dogs[3]. Vinorelbine is tolerated at a weekly interval in tumor-bearing cats, with an MTD of 11.5 mg/m2[4].

References:
[1]. Ngan VK, et al. Mechanism of mitotic block and inhibition of cell proliferation by the semisynthetic Vinca alkaloids vinorelbine and its newer derivative vinflunine. Mol Pharmacol. 2001 Jul;60(1):225-32.
[2]. Liu XM, et al. Unique induction of p21(WAF1/CIP1)expression by vinorelbine in androgen-independent prostate cancer cells. Br J Cancer. 2003 Oct 20;89(8):1566-73.
[3]. Poirier VJ, et al. Toxicity, dosage, and efficacy of vinorelbine (Navelbine) in dogs with spontaneous neoplasia. J Vet Intern Med. 2004 Jul-Aug;18(4):536-9.
[4]. Pierro JA, et al. Phase I clinical trial of vinorelbine in tumor-bearing cats. J Vet Intern Med. 2013 Jul-Aug;27(4):943-8.