Improvement in oral bioavailability of 2,4-diaminopyrimidine c-Met inhibitors by incorporation of a 3-amidobenzazepin-2-one group.

The hepatocyte growth factor (HGF)-c-Met signaling axis is involved in the mediation of many biological activities, including angiogenesis, proliferation, cell survival, cell motility, and morphogenesis. Dysregulation of c-Met signaling (e.g., overexpression or increased activation) is associated with the proliferation and metastasis of a wide range of tumor types, including breast, liver, lung, colorectal, gastric, bladder, and prostate, among others. Inhibiting the HGF-c-Met pathway is predicted to lead to anti-tumor effects in many cancers. Elaboration of the SAR around a series of 2,4-diaminopyrimidines led to a number of c-Met inhibitors in which pharmaceutical properties were modulated by substituents appended on the C2-benzazepinone ring. In particular, certain-3-amidobenzazepin-2-one analogs had improved oral bioavailability and were evaluated in PK/PD and efficacy models. Lead compounds demonstrated tumor stasis with partial regressions when evaluated in a GTL-16 tumor xenograft mouse model.

2,4-Diaminopyrimidine inhibitors of c-Met kinase bearing benzoxazepine anilines.

Elaboration of the SAR around a series of 2,4-diaminopyrimidines led to a number of c-Met inhibitors in which kinase selectivity was modulated by substituents appended on the C4-aminobenzamide ring and the nature of the C2-aminoaryl ring. Further lead optimization of the C2-aminoaryl group led to benzoxazepine analogs whose pharmaceutical properties were modulated by the nature of the substituent on the benzoxazepine nitrogen. Tumor stasis (with partial regressions) were observed when an orally bioavailable analog was evaluated in a GTL-16 tumor xenograft mouse model. Subsequent PK/PD studies suggested that a metabolite contributed to the overall in vivo response.

Development of an in vivo preclinical screen model to estimate absorption and first-pass hepatic extraction of xenobiotics. II. Use of ketoconazole to identify P-glycoprotein/CYP3A-limited bioavailability in the monkey.

The effect of P-glycoprotein (Pgp) and/or CYP3A on the disposition of xenobiotics has been extensively investigated and is often of interest during drug discovery lead optimization. We have previously described a monkey pharmacokinetic screen to rapidly estimate absorption and first-pass extraction. In the present work, this monkey screen has been expanded to include an assessment of Pgp/CYP3A effects on absorption and first-pass extraction, using ketoconazole as a prototypic dual Pgp/CYP3A inhibitor. To generate a ketoconazole dosing regimen, the pharmacokinetics of ketoconazole were first determined in the monkey and were found to be consistent with that previously described in the rat, dog, and human. Dose-ranging experiments demonstrated that a single 10-mg/kg intraduodenal ketoconazole dose would provide an appropriate exposure; this dose was used throughout subsequent interaction experiments. Next, erythromycin and propranolol were explored as positive and negative control substrates for Pgp/CYP3A interactions, respectively. As anticipated, ketoconazole produced no change in the absorption or first-pass extraction of propranolol but resulted in a substantial increase in absorption and decrease in first-pass extraction of erythromycin. Finally, this ketoconazole-based monkey screen was deployed in a drug discovery setting, and examples of such use are presented. These experiments have allowed a more complete characterization of ketoconazole as a prototypic dual Pgp/CYP3A inhibitor and its use as a tool in a preclinical setting and further demonstrate the use of the monkey to investigate the role of Pgp/CYP3A in limiting the oral bioavailability of new drug candidates.