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Antiangiogenic therapy is a clinically validated modality in cancer treatment. To date, all approved antiangiogenic drugs primarily inhibit the VEGF pathway. Delta-like ligand 4 (DLL4) has been identified as a potential drug target in VEGF-independent angiogenesis and tumor-initiating cell (TIC) survival. A dual-specific biologic targeting both VEGF and DLL4 could be an attractive strategy to improve the effectiveness of anti-VEGF therapy. ABT-165 was uniquely engineered using a proprietary dual-variable domain immunoglobulin (DVD-Ig) technology based on its ability to bind and inhibit both DLL4 and VEGF. In vivo, ABT-165 induced significant tumor growth inhibition compared with either parental antibody treatment alone, due, in part, to the disruption of functional tumor vasculature. In combination with chemotherapy agents, ABT-165 also induced greater antitumor response and outperformed anti-VEGF treatment. ABT-165 displayed nonlinear pharmacokinetic profiles in cynomolgus monkeys, with an apparent terminal half-life > 5 days at a target saturation dose. In a GLP monkey toxicity study, ABT-165 was well-tolerated at doses up to 200 mg/kg with non-adverse treatment–related histopathology findings limited to the liver and thymus. In summary, ABT-165 represents a novel antiangiogenic strategy that potently inhibits both DLL4 and VEGF, demonstrating favorable in vivo efficacy, pharmacokinetic, and safety profiles in preclinical models. Given these preclinical attributes, ABT-165 has progressed to a phase I study. Mol Cancer Ther; 17(5); 1039–50. ©2018 AACR.

The ubiquitous NAD+ kinase (NADK) is the only known enzyme to catalyze formation of NADP+ from NAD+. The capacity to maintain an adequate supply of NADP(H) has important implications for development because of its requirement as a cofactor and electron donor in biosynthesis and detoxication reactions. Modulation of NADK may directly influence NADP(H) concentrations and cell sensitivity to embryotoxicants. Measurable activities of NADK were not detected in gestational day (GD) 10 rat conceptuses. By GD 11, specific activities of 1.8 and 7.0 pmol NADP+/min/microg protein were measured in embryos and visceral yolk sacs (VYSs), respectively. The VYS specific activities decreased thereafter to 0.5 pmol NADP+/min/microg protein by GD 18. Specific activities of NADK in placenta increased from 1.3 pmol NADP+/min/microg protein on GD 11 to 32.7 pmol NADP+/min/microg protein on GD 15. Specific activities in the liver increased from 1.7 pmol NADP+/min/microg protein on GD 15 to 51.1 pmol NADP+/min/microg protein on GD 21. NADK specific activities were also determined in other developmentally relevant tissues such as the heart and the brain. In the heart, NADK activity was at its lowest just before birth while in the brain it peaked at 5.4 pmol NADP+/min/microg protein just prior to birth. In the lung, activity increased from 0.9 pmol NADP+/min/microg protein on GD 17 to 5.9 pmol NADP+/min/microg protein on GD 21. However, activities dropped in the kidney from 2.0 pmol NADP+/min/microg protein on GD 17 to 1.1 pmol NADP+/min/microg protein on GD 21. These results demonstrate dramatic temporal and spatial variations in NADK activity. Tissue variations in NADK activities may reflect alterations in functional needs for cofactors during differentiation and a cooperation between tissues to optimize detoxification capacity. This is particularly important when chemical exposure during pregnancy disrupts pyridine nucleotide redox status and the conceptus must rely on NADK to provide additional NADP(H).

It is proposed that protection of the developing embryo from chemical and environmental insults that produces oxidative stress requires a proper glutathione (GSH) and pyridine nucleotide status in both the embryo and extra-embryonic membranes. Modulation of pyridine nucleotide flux [NAD(H) and NAD(P)H] in the visceral yolk sac (VYS) by the thiol oxidants diamide and tert-butyl hydroperoxide (tBH) was studied in real time using microfiberoptic sensors in GD 10 rat conceptuses. Consecutive 5-min exposures to 125- and 250-microM diamide resulted in a fluorescence decrease of 14 and 32 Arbitrary Fluorescence Units (AFU). An additional consecutive exposure to 500-microM diamide caused an attenuated decrease followed by a rebound increase of 22 AFU. Consecutive 5-min exposures to tBH at 250 and 500 microM produced fluorescence decreases similar to that of 500 microM diamide, but the decreases were attenuated at 1000 microM. However, there was variability in the rebound increase. A 5-min exposure to tBH (500 microM) alone caused a fluorescence decrease of 14 AFU followed by a rebound increase of 8 AFU. The rate of fluorescence decrease was attenuated by 50% with pretreatment with the glutathione reductase (GSSG-Rd) inhibitor, BCNU (1,3, bis(2 chloroethyl)-1-nitrosourea), indicating that the decrease in surface fluorescence was probably attributable to a decrease in NADPH. Decreases in fluorescence, observed from the surface of the VYS, correlated with decreases in GSH/GSSG ratios in the embryos and the VYS. After exposure to tBH, GSH levels in conceptuses decreased at the end of 5 and 15 min, with a corresponding increase in oxidized glutathione (GSSG) at the end of 3, 5, and 15 min. Our results demonstrate that the increased production of GSSG on exposure to thiol oxidants correlates with a decrease in the reduced pyridine nucleotide, implying the presence of an active GSSG-Rd pathway in the conceptus during organogenesis, and implicating an important role of the pyridine nucleotides in the restoration of GSH homeostasis in the developing rat conceptus during organogenesis.