In vivo antitumor activity of bis(4,7-dimethyl-1,10-phenanthroline) sulfatooxovanadium(IV) {METVAN [VO(SO₄)(Me₂-Phen)₂]}

The compound bis(4,7-dimethyl-1,10-phenanthroline) sulfatooxovanadium(IV) {METVAN [VO(SO₄)(Me₂Phen)₂]}, exhibits potent cytotoxicity against human cancer cells at low micromolar concentrations. At concentrations ≥1 μM, METVAN treatment was associated with a nearly complete loss of the adhesive, migratory, and invasive properties of the treated tumor cell populations. METVAN did not cause acute or subacute toxicity in mice at dose levels ranging from 12.5 mg/kg to 100 mg/kg. Therapeutic plasma concentrations ≥5 μM were rapidly achieved and maintained in mice for at least 24 h after i.p. bolus injection of a single 10 mg/kg nontoxic dose of METVAN. At this dose level, the maximum plasma METVAN concentration was 37.0 μM, which was achieved with a t_max of 21.4 min. Plasma samples (diluted 1:16) from METVAN-treated mice killed 85% of human breast cancer cells in vitro. METVAN was slowly eliminated with an apparent plasma t_1/2 of 17.5 h and systemic clearance of 42.1 ml/h/kg. In accordance with its potent in vitro activity and favorable in vivo pharmacokinetics, METVAN exhibited significant antitumor activity and delayed tumor progression in CB.17 severe combined immunodeficient (SCID) mouse xenograft models of human glioblastoma and breast cancer. In these experiments, METVAN was administered in daily injections of a single nontoxic 10 mg/kg i.p. dose on 5 consecutive days per week for 4 consecutive weeks beginning the day after the s.c. inoculation of U87 glioblastoma or MDA-MB-231 breast cancer cells. At 40 days after the inoculation of tumor cells, the U87 tumor xenografts in the vehicle-treated control SCID mice were much larger than those of the mice treated with METVAN (4560 ± 654 mm³ versus 1688 ± 571 mm³; P = 0.003). Similarly, the MDA-MB-231 tumors in SCID mice treated with METVAN were much smaller 40 days after tumor cell inoculation than those of the vehicle-treated control SCID mice (174 ± 29 mm³ versus 487 ± 82 mm³; P = 0.002). The favorable in vivo pharmacodynamic features and antitumor activity of METVAN warrants further development of this novel oxovanadium compound as a potential new anticancer agent.