Enfortumab Vedotin Antibody-Drug Conjugate Targeting Nectin-4 Is a Highly Potent Therapeutic Agent in Multiple Preclinical Cancer Models.

The identification of optimal target antigens on tumor cells is central to the advancement of new antibody-based cancer therapies. We performed suppression subtractive hybridization and identified nectin-4 (PVRL4), a type I transmembrane protein and member of a family of related immunoglobulin-like adhesion molecules, as a potential target in epithelial cancers. We conducted immunohistochemical analysis of 2,394 patient specimens from bladder, breast, lung, pancreatic, ovarian, head/neck, and esophageal tumors and found that 69% of all specimens stained positive for nectin-4. Moderate to strong staining was especially observed in 60% of bladder and 53% of breast tumor specimens, whereas the expression of nectin-4 in normal tissue was more limited. We generated a novel antibody-drug conjugate (ADC) enfortumab vedotin comprising the human anti-nectin-4 antibody conjugated to the highly potent microtubule-disrupting agent MMAE. Hybridoma (AGS-22M6E) and CHO (ASG-22CE) versions of enfortumab vedotin (also known as ASG-22ME) ADC were able to bind to cell surface-expressed nectin-4 with high affinity and induced cell death in vitro in a dose-dependent manner. Treatment of mouse xenograft models of human breast, bladder, pancreatic, and lung cancers with enfortumab vedotin significantly inhibited the growth of all four tumor types and resulted in tumor regression of breast and bladder xenografts. Overall, these findings validate nectin-4 as an attractive therapeutic target in multiple solid tumors and support further clinical development, investigation, and application of nectin-4-targeting ADCs. Cancer Res; 76(10); 3003-13. ©2016 AACR.

Validation of an ocular microdialysis technique in rabbits with permanently implanted vitreous probes: systemic and intravitreal pharmacokinetics of fluorescein.

The purpose of this work is to validate a novel ocular microdialysis sampling technique in rabbits with permanently implanted vitreous probes. This objective is achieved by studying the vitreous pharmacokinetics of fluorescein following systemic and intravitreal administration. The rabbits were divided into two groups (groups I and II) based on whether or not they were allowed a recovery period following surgical implantation of probes. The integrity of the blood-retinal barrier was determined by the vitreal protein concentrations and the fluorescein permeability index. Vitreal protein concentrations returned to baseline 48 h after probe implantation and therefore experiments were conducted 72 h post-implantation of probes in rabbits where recovery period was allowed. The permeability indices for fluorescein after systemic administration in group I (without recovery period) and group II (with recovery period) indicated that the integrity of the blood-retinal barrier was maintained and were found out to be 0.55 +/- 0.27 and 0.71 +/- 0.38%, respectively, for the vitreous chamber. Following microdialysis probe implantation in the group II rabbits, the blood-retinal barrier integrity was not compromised. A novel microdialysis technique in rabbits with permanently implanted probes for studying the pharmacokinetics of posterior segment has been developed and characterized.

In vivo antiviral efficacy of a dipeptide acyclovir prodrug, val-val-acyclovir, against HSV-1 epithelial and stromal keratitis in the rabbit eye model.

PURPOSE: A dipeptide prodrug of the antiviral nucleoside acyclovir (ACV), val-val-ACV (VVACV), was evaluated in vivo as a potential drug candidate for improving antiviral efficacy against herpetic epithelial and stromal keratitis. METHODS: The effect of 1% VVACV on epithelial keratitis induced by inoculation of HSV-1 strain McKrae (25 microL of 10(5) plaque-forming units [PFU]) in the scarified rabbit cornea and stromal keratitis induced by intrastromal injection of HSV-1 strain RE (10 microL of 10(5) PFU) was compared with that of 1% trifluorothymidine (TFT) and balanced salt solution as the vehicle control. Both eyes of 10 rabbits were used in each treatment group. Lesions were evaluated by slit lamp examinations over a 2-week period after infection. Aqueous humor samples and corneas were analyzed for drug concentrations at the end of each experiment. Cytotoxicity of VVACV in comparison with val-acyclovir (VACV), ACV, and TFT was evaluated in cellular proliferation assays. RESULTS: The dipeptide prodrug VVACV demonstrated excellent activity against HSV-1 in the rabbit epithelial and stromal keratitis models: 1% VVACV was as effective as 1% TFT. The prodrug was also less cytotoxic than TFT, which is the only effective drug currently licensed and routinely used for topical treatment of ocular herpes infections in the United States. CONCLUSIONS: The less cytotoxic and highly water-soluble prodrug VVACV, which showed excellent in vivo activity against HSV-1 in rabbit epithelial and stromal keratitis, is a promising drug candidate for treatment of ocular HSV infections.