A framework to guide dose & regimen strategy for clinical drug development.

Optimizing new drug therapies remains a challenge for clinical development, despite the use of ever more sophisticated quantitative methodologies. Although conceptually simple, the idea of finding the right treatment at the right dose for the right patient to ensure an appropriate balance of risks and benefits is challenging and requires a multidisciplinary approach. In this paper, we present a framework developed as a tool for organizing knowledge and facilitating collaboration in development teams.

An Open-Label Study of the Impact of Hepatic Impairment on the Pharmacokinetics and Safety of Single Oral and Intravenous Doses of Omadacycline.

Omadacycline is a once-daily oral or intravenous (i.v.) aminomethylcycline antibiotic approved in the United States for the treatment of community-acquired bacterial pneumonia (CABP) and acute bacterial skin and skin structure infections (ABSSSI) in adults. Omadacycline pharmacokinetics were characterized in 18 patients with hepatic impairment and 12 matched healthy subjects. Patients with hepatic impairment received i.v. omadacycline at 100 mg (mild hepatic impairment) or 50 mg (moderate and severe hepatic impairment) and oral omadacycline at 300 mg (mild hepatic impairment) or 150 mg (moderate hepatic impairment); oral omadacycline was not evaluated in those with severe hepatic impairment. Safety monitoring included the collection of adverse events (AEs), performance of laboratory tests, determination of vital signs, and performance of electrocardiograms. Omadacycline exposures were similar in patients with hepatic impairment and healthy subjects following i.v. or oral administration, with the geometric mean ratios for the area under the concentration-time curve and the maximum drug concentration ranging from 0.79 to 1.42. Omadacycline was safe and well tolerated. Overall, 13/30 (43.3%) participants experienced an AE; those occurring in more than 1 participant included headache (13.3%), nausea (6.7%), infusion-site pain (6.7%), contusion (6.7%), and dizziness (6.7%), with no differences based on the degree of hepatic impairment or the route of administration. Asymptomatic increases in heart rate were observed; none was considered an AE. These findings suggest that no omadacycline dose adjustment is warranted in patients with hepatic impairment.

The Safety and Antiviral Activity of BZF961 with or without Ritonavir in Patients Infected with Hepatitis C Virus: A Randomized, Multicenter Trial.

PURPOSE: Infection with hepatitis C virus is the leading cause of infectious disease mortality in the United States. BZF961 is a novel small molecule inhibitor of the hepatitis C virus NS3-4A protease. Here we present the results of a randomized, double-blinded, placebo-controlled, multicentered study in treatment-naïve patients with chronic hepatitis C virus genotype-1 infection. METHODS: Patients were enrolled sequentially in 2 parts and treated for 3days. BZF961 was administered as monotherapy (500mg BID for 3 days) or in combination with the cytochrome P450 3A4 inhibitor ritonavir to boost its exposure (BZF961 10, 20, or 50mg QD or BID). FINDINGS: BZF961 was safe and well tolerated in the patients studied with no serious adverse events. There were no appreciable differences in adverse events among patients who received BZF961, BZF961 with ritonavir, or placebo. There was a significant, clinically meaningful reduction in viral load from baseline in patients treated either with BZF961 500mg every 12hours alone or BZF961 50mg every 12hours in combination with ritonavir. Activity against the hepatitis C virus of the lower-dose regimens was apparent but more modest. There were no relevant changes from baseline viral loads in placebo-treated patients. IMPLICATIONS: Coadministration of ritonavir with BZF961 boosted BZF961 exposure (including Cmin, which is the clinically relevant parameter associated with antiviral activity) in a therapeutic range with less variability compared with BZF961 alone. For strategic reasons, BZF961 is no longer under development.

Challenges and Opportunities in the Development of Medical Therapies for Pediatric Populations and the Role of Extrapolation.

Extrapolation can be used to address challenges in pediatric drug development. This review describes how these challenges could be addressed by further evolution of quantitative frameworks (i.e., model-based/informed drug discovery and development) and regulatory science in support of pediatric drug development. Included are examples of diseases/indications where extrapolation has been used in different ways as a basis for identifying gaps in the framework and opportunities for continued advancement of pediatric drug development.

Clinical disposition, metabolism and in vitro drug-drug interaction properties of omadacycline.

1. Absorption, distribution, metabolism, transport and elimination properties of omadacycline, an aminomethylcycline antibiotic, were investigated in vitro and in a study in healthy male subjects. 2. Omadacycline was metabolically stable in human liver microsomes and hepatocytes and did not inhibit or induce any of the nine cytochrome P450 or five transporters tested. Omadacycline was a substrate of P-glycoprotein, but not of the other transporters. 3. Omadacycline metabolic stability was confirmed in six healthy male subjects who received a single 300 mg oral dose of [14C]-omadacycline (36.6 µCi). Absorption was rapid with peak radioactivity (∼610 ngEq/mL) between 1-4 h in plasma or blood. The AUClast of plasma radioactivity (only quantifiable to 8 h due to low radioactivity) was 3096 ngEq h/mL and apparent terminal half-life was 11.1 h. Unchanged omadacycline reached peak plasma concentrations (∼563 ng/mL) between 1-4 h. Apparent plasma half-life was 17.6 h with biphasic elimination. Plasma exposure (AUCinf) averaged 9418 ng h/mL, with high clearance (CL/F, 32.8 L/h) and volume of distribution (Vz/F 828 L). No plasma metabolites were observed. 4. Radioactivity recovery of the administered dose in excreta was complete (>95%); renal and fecal elimination were 14.4% and 81.1%, respectively. No metabolites were observed in urine or feces, only the omadacycline C4-epimer.

Randomized, Open-Label Study of the Pharmacokinetics and Safety of Oral and Intravenous Administration of Omadacycline to Healthy Subjects.

Omadacycline is a first-in-class aminomethylcycline antibiotic with microbiological activity against Gram-positive and Gram-negative aerobes and anaerobes and atypical bacteria that is being developed for the treatment of acute bacterial skin and skin structure infections (ABSSSI) and community-acquired bacterial pneumonia (CABP). The bioavailability of a phase 3 tablet formulation relative to that obtained via intravenous (i.v.) administration (and of other oral formulations relative to that of the phase 3 tablet) was investigated in an open-label, randomized, four-period, crossover study with healthy subjects age 18 to 50 years. Subjects received omadacycline at 100 mg i.v., 300 mg orally as two different tablet formulations with different dissolution profiles, and 300 mg as an oral solution. Plasma omadacycline concentrations were determined using a validated liquid chromatography-tandem mass spectrometry (LC-MS/MS) method. Twenty of 24 subjects completed all treatment periods. The two tablet formulations produced equivalent total exposures. The phase 3 tablet produced an exposure equivalent to that of the 100-mg i.v. dose, with a geometric mean ratio (90% confidence intervals [CI]) for area under the concentration-time curve from 0 h to infinity [AUC∞]) of 1.00 (0.93, 1.07). The absolute bioavailability of the tablets was approximately 34.5%. Intersubject variability was consistent among the oral formulations (∼20 to 25%). Single oral and i.v. doses of omadacycline were well tolerated; three subjects experienced mild adverse events (dizziness, nausea, and vomiting) that resolved without intervention. A 300-mg dose of the tablet formulation of omadacycline intended for use in phase 3 studies produced a total exposure equivalent to that of a 100-mg i.v. dose.

The effects of CYP3A4 induction and inhibition on the pharmacokinetics of alisporivir in humans.

In vitro data suggest that alisporivir is a substrate and inhibitor of CYP3A4 and P-gp. Hence, the potential for drug-drug interactions when alisporivir is co-administered with CYP3A4 and/or P-gp inhibitors such as ketoconazole, azithromycin and CYP3A4 inducers such as rifampin were evaluated in three separate clinical studies. Co-administration with ketoconazole (a strong CYP3A4 inhibitor) increased the Cmax , AUC and terminal elimination half-life of alisporivir by approximately two-, eight- ,and threefold, respectively. Co-administration with azithromycin (a putative weak CYP3A4 inhibitor and substrate) had no impact on the Cmax and AUC of alisporivir. Rifampin (a CYP3A4 inducer) caused an approximate 90% reduction in alisporivir Cmax and AUC and a fourfold reduction in alisporivir terminal elimination half-life. Alisporivir as an inhibitor of CYP3A4 caused a 39% increase in azithromycin exposure. The results from these studies establish alisporivir as a sensitive CYP3A4 substrate in vivo. Consequently, co-administered potent CYP3A4 inhibitors and inducers are likely to cause clinically significant changes in the exposure to alisporivir.

Population pharmacokinetics of the active metabolite of leflunomide in pediatric subjects with polyarticular course juvenile rheumatoid arthritis.

Leflunomide is a pyrimidine synthesis inhibitor used in the treatment of rheumatoid arthritis. Data from two clinical studies were used to establish a population pharmacokinetic (PPK) model for the active metabolite (M1) of leflunomide in patients with juvenile rheumatoid arthritis (JRA) and determine appropriate pediatric doses. Seventy-three subjects 3-17 years of age provided 674 M1 concentrations. The PPK model was derived from nonlinear mixed-effects modeling and qualified by cross-study evaluation and predictive check. A one-compartment model with first-order input described M1 PPK well. Body weight (WT) correlated weakly with oral clearance (CL/F = 0.020.[WT/40](0.430)) and strongly with volume of distribution (V/F = 5.8.[WT/40](0.769)). Steady-state concentrations (C(ss)) of M1 in JRA were compared for a variety of leflunomide dose regimens using Monte-Carlo simulation. To achieve comparable C(ss) values in pediatric patients with JRA to that in adult patients, doses of leflunomide should be adjusted modestly: 10 mg/d for 10-20 kg, 15 mg/d for 20-40 kg, and 20 mg/d for > 40 kg.

The bioequivalence of telithromycin administered orally as crushed tablets versus tablets swallowed whole.

This open-label, randomized, crossover study was conducted to demonstrate bioequivalence for telithromycin administered as crushed or whole tablets. Single 800-mg telithromycin doses (2x400-mg tablets) were administered as crushed tablets mixed in 240 mL nutritional supplement drink followed by 120 mL water or as whole tablets swallowed with 240 mL water. Plasma telithromycin concentrations were measured by liquid chromatography/mass spectrometry; pharmacokinetic parameters were determined using noncompartmental methods. Average bioequivalence criteria were applied. Thirty-two subjects received telithromycin by both methods. The 90% confidence intervals for the geometric mean ratios of maximum plasma concentration and area under the plasma concentration-time curve to 24 hours were within the 0.80 to 1.25 range. Median tmax was 3.00 hours for both treatments. Both methods of administration were well tolerated. Crushing telithromycin tablets and administering them with a nutritional supplement drink is bioequivalent to ingesting whole tablets and could be a viable method of administration for patients unable to swallow tablets whole.