Preclinical assessment of the absorption, distribution, metabolism and excretion of GDC-0449 (2-chloro-N-(4-chloro-3-(pyridin-2-yl)phenyl)-4-(methylsulfonyl)benzamide), an orally bioavailable systemic Hedgehog signalling pathway inhibitor.

GDC-0449 (2-chloro-N-(4-chloro-3-(pyridin-2-yl)phenyl)-4-(methylsulfonyl)benzamide) is a potent, selective Hedgehog (Hh) signalling pathway inhibitor being developed for the treatment of various cancers. The in vivo clearance of GDC-0449 was estimated to be 23.0, 4.65, 0.338, and 19.3 ml min(-1) kg(-1) in mouse, rat, dog and monkeys, respectively. The volume of distribution ranged from 0.490 in rats to 1.68 l kg(-1) in mice. Oral bioavailability ranged from 13% in monkeys to 53% in dogs. Predicted human clearance using allometry was 0.096-0.649 ml min(-1) kg(-1) and the predicted volume of distribution was 0.766 l kg(-1). Protein binding was extensive with an unbound fraction less than or equal to 6%, and the blood-to-plasma partition ratio ranged from 0.6 to 0.8 in all species tested. GDC-0449 was metabolically stable in mouse, rat, dog and human hepatocytes and had a more rapid turnover in monkey hepatocytes. Proposed metabolites from exploratory metabolite identification in vitro (rat, dog and human liver microsomes) and in vivo (dog and rat urine) include three primary oxidative metabolites (M1-M3) and three sequential glucuronides (M4-M6). Oxidative metabolites identified in microsomes M1 and M3 were formed primarily by P4503A4/5 (M1) and P4502C9 (M3). GDC-0449 was not a potent inhibitor of P4501A2, P4502B6, P4502D6, and P4503A4/5 with IC50 estimates greater than 20 microM. K(i)'s estimated for P4502C8, P4502C9 and P4502C19 and were 6.0, 5.4 and 24 microM, respectively. An evaluation with Simcyp suggests that GDC-0449 has a low potential of inhibiting P4502C8 and P4502C9. Furthermore, GDC-0449 (15 microM) was not a potent P-glycoprotein/ABCB1 inhibitor in MDR1-MDCK cells. Overall, GDC-0449 has an attractive preclinical profile and is currently in Phase II clinical trials.

Disposition of GDC-0879, a B-RAF kinase inhibitor in preclinical species.

1. The pharmacokinetics and disposition of GDC-0879, a small molecule B-RAF kinase inhibitor, was characterized in mouse, rat, dog, and monkey. 2. In mouse and monkey, clearance (CL) of GDC-0879 was moderate (18.7-24.3 and 14.5 +/- 2.1 ml min(-1) kg(-1), respectively), low in dog (5.84 +/- 1.06 ml min(-1) kg(-1)) and high in rat (86.9 +/- 14.2 ml min(-1) kg(-1)). The volume of distribution across species ranged from 0.49 to 1.9 l kg(-1). Mean terminal half-life values ranged from 0.28 h in rats to 2.97 h in dogs. Absolute oral bioavailability ranged from 18% in dog to 65% in mouse. 3. Plasma protein binding of GDC-0879 in mouse, rat, dog, monkey, and humans ranged from 68.8% to 81.9%. 4. In dog, the major ketone metabolite (G-030748) of GDC-0879 appeared to be formation rate-limited. 5. Based on assessment in dogs, the absorption of GDC-0879 appeared to be sensitive to changes in gut pH, food and salt form (solubililty), with approximately three- to four-fold change in areas under the curve (AUCs) observed.