Pharmacokinetics and Disposition of Momelotinib Revealed a Disproportionate Human Metabolite-Resolution for Clinical Development.

Momelotinib (MMB), a small-molecule inhibitor of Janus kinase (JAK)1/2 and of activin A receptor type 1 (ACVR1), is in clinical development for the treatment of myeloproliferative neoplasms. The pharmacokinetics and disposition of [14C]MMB were characterized in a single-dose, human mass-balance study. Metabolism and the pharmacologic activity of key metabolites were elucidated in multiple in vitro and in vivo experiments. MMB was rapidly absorbed following oral dosing with approximately 97% of the radioactivity recovered, primarily in feces with urine as a secondary route. Mean blood-to-plasma [14C] area under the plasma concentration-time curve ratio was 0.72, suggesting low association of MMB and metabolites with blood cells. [14C]MMB-derived radioactivity was detectable in blood for ≤48 hours, suggesting no irreversible binding of MMB or its metabolites. The major circulating human metabolite, M21 (a morpholino lactam), is a potent inhibitor of JAK1/2 and ACVR1 in vitro. Estimation of pharmacological activity index suggests M21 contributes significantly to the pharmacological activity of MMB for the inhibition of both JAK1/2 and ACVR1. M21 was observed in disproportionately higher amounts in human plasma than in rat or dog, the rodent and nonrodent species used for the general nonclinical safety assessment of this molecule. This discrepancy was resolved with additional nonclinical studies wherein the circulating metabolites and drug-drug interactions were further characterized. The human metabolism of MMB was mediated primarily by multiple cytochrome P450 enzymes, whereas M21 formation involved initial P450 oxidation of the morpholine ring followed by metabolism via aldehyde oxidase.

Use of Multiple Probes to Assess Transporter- and Cytochrome P450-Mediated Drug-Drug Interaction Potential of the Pangenotypic HCV NS5A Inhibitor Velpatasvir.

BACKGROUND AND OBJECTIVES: Velpatasvir (VEL; GS-5816) is a potent, pangenotypic hepatitis C virus (HCV), non-structural protein 5A inhibitor in clinical development for the treatment of chronic HCV infection. In vitro studies indicate that VEL may inhibit several drug transporters and be a substrate for enzyme/drug transport systems in vivo. The purpose of this study was to evaluate the potential of VEL as a perpetrator or victim of metabolic- and transporter-based drug-drug interactions using complementary probe drugs. METHODS: This Phase 1 study was a randomized, cross-over, open-label, single- and multiple-dose, five-cohort study. Serial blood samples were collected following oral administration of reference and test treatments. The primary pharmacokinetic parameters of each analyte were compared when administered alone or in combination. The 90% confidence intervals (CI) for the ratio of the geometric least-squares means of the test and reference treatments was calculated for each analyte and parameter of interest. RESULTS: This study demonstrated that VEL is a weak (P-gp, OATP) to moderate (breast cancer resistance protein) transport inhibitor. As a victim of interactions, VEL is moderately affected by potent inhibitors and to a greater extent, potent inducers of enzyme/drug transporter systems. CONCLUSIONS: The impact of specific transporters and overall contribution of drug transport vs. metabolizing enzymes on the disposition of VEL was characterized through the use of complementary probes, despite the lack of phenotypic specificity, and informs a broad range of drug-drug interaction recommendations.

Fosfomycin/tobramycin for inhalation in patients with cystic fibrosis with pseudomonas airway infection.

RATIONALE: Fosfomycin/tobramycin for inhalation (FTI), a unique, broad-spectrum antibiotic combination, may have therapeutic potential for patients with cystic fibrosis (CF). OBJECTIVES: To evaluate safety and efficacy of FTI (160/40 mg or 80/20 mg), administered twice daily for 28 days versus placebo, in patients greater than or equal to 18 years of age, with CF, chronic Pseudomonas aeruginosa (PA) airway infection, and FEV(1) greater than or equal to 25% and less than or equal to 75% predicted. METHODS: This double-blind, placebo-controlled, multicenter study assessed whether FTI/placebo maintained FEV(1) % predicted improvements achieved following a 28-day, open-label, run-in course of aztreonam for inhalation solution (AZLI). MEASUREMENTS AND MAIN RESULTS: A total of 119 patients were randomized to FTI (160/40 mg: n = 41; 80/20 mg: n = 38) or placebo (n = 40). Mean age was 32 years and mean FEV(1) was 49% predicted at screening. Relative improvements in FEV(1) % predicted achieved by the AZLI run-in were maintained in FTI groups compared with placebo (160/40 mg vs. placebo: 6.2% treatment difference favoring FTI, P = 0.002 [primary endpoint]; 80/20 mg vs. placebo: 7.5% treatment difference favoring FTI, P < 0.001). The treatment effect on mean PA sputum density was statistically significant for the FTI 80/20 mg group versus placebo (-1.04 log(10) PA colony-forming units/g sputum difference, favoring FTI; P = 0.01). Adverse events, primarily cough, were consistent with CF disease. Respiratory events, including dyspnea and wheezing, were less common with FTI 80/20 mg than FTI 160/40 mg. No clinically significant differences between groups were reported for laboratory values. CONCLUSIONS: FTI maintained the substantial improvements in FEV(1) % predicted achieved during the AZLI run-in and was well tolerated. FTI is a promising antipseudomonal therapy for patients with CF.