Ultrasound Enhances ZD2767P–Carboxypeptidase G2 against Chemoresistant Ovarian Cancer Cells by Altering the Intracellular Pharmacokinetics of ZD2767D

Prodrug–carboxypeptidase G2 (e.g., ZD2767P+CPG2) can realize a targeted treatment where the specific advantage is a lack of CPG2 analogues in humans, but it is limited by low efficacy. Here ultrasound was employed to enhance ZD2767P+CPG2 (i.e., ZD2767P+CPG2+US) against chemoresistant human ovarian cancer cells. The release dynamics of ZD2767D (activated drug) by CPG2 were investigated. The in vitro efficacy was explored in SKOV3 and SKOV3/DDP (cisplatin-resistant subline) cells; spectrophotometry was established to quantify ZD2767P and ZD2767D, and then intracellular pharmacokinetics were evaluated. The in vivo efficacy was validated in both subcutaneous and orthotopic tumors. With insonation, the ZD2767D concentration was increased during an early period. Insonation synergized ZD2767P+CPG2 to enhance cell death and apoptosis, and efficacies in SKOV3 and SKOV3/DDP cells were similar. Intracellular pharmacokinetics of ZD2767D were nonproportional, and insonation increased the peak level, area under the level vs time curve, and mean residence time. In subcutaneous xenografts, ZD2767P+CPG2 and ZD2767P+CPG2+US resulted in volume-inhibitory rates of 20.4% and 26.5% in SKOV3 tumors and 36.8% and 81.6% in SKOV3/DDP tumors, respectively. In the orthotopic tumor model, the survival time in group ZD2767P+CPG2 or ZD2767P+CPG2+US was prolonged compared with group control, in SKOV3 (33.0 ± 3.5 or 39.2 ± 1.8 vs 25.0 ± 1.6 days, p < 0.0001) and SKOV3/DDP (16.2 ± 4.8 or 22.3 ± 7.3 vs 8.7 ± 3.9 days, p = 0.0015) tumors. These data indicated that ZD2767P+CPG2+US was effective against resistant ovarian cancer cells.