Pharmacokinetics of surotomycin from phase 1 single and multiple ascending dose studies in healthy volunteers

Background

Surotomycin, a novel, orally administered, cyclic, lipopeptide antibacterial in development for the treatment of Clostridium difficile-associated diarrhea, has demonstrated minimal intestinal absorption in animal models.

Methods

Safety, tolerability, and plasma pharmacokinetics of single and multiple ascending oral doses (SAD/MAD) of surotomycin in healthy volunteers were characterized in two randomized, double-blind, placebo-controlled, phase 1 studies.

Results

Participants were sequentially enrolled into one of four SAD (500, 1000, 2000, 4000 mg surotomycin) or three MAD (250, 500, 1000 mg surotomycin twice/day for 14 days) cohorts. Ten subjects were randomized 4:1 into each cohort to receive surotomycin or placebo. Surotomycin plasma concentrations rose as dose increased (maximum plasma concentration [C_max]: 10.5, 21.5, 66.6, and 86.7 ng/mL). Systemic levels were generally low, with peak median surotomycin plasma concentrations observed 6–12 h after the first dose. In the MAD study, surotomycin plasma concentrations were higher on day 14 (C_max: 25.5, 37.6, and 93.5 ng/mL) than on day 1 (C_max: 6.8, 11.0, and 21.1 ng/mL for increasing doses), indicating accumulation. In the SAD study, <0.01% of the administered dose was recovered in urine. Mean surotomycin stool concentration from the 1000 mg MAD cohort was 6394 μg/g on day 5. Both cohorts were well tolerated with all adverse events reported as mild to moderate.

Conclusion

Both SAD and MAD studies of surotomycin demonstrated minimal systemic exposure, with feces the primary route of elimination following oral administration; consistent with observations with similar compounds, such as fidaxomicin. Results of these phase 1 studies support the continued clinical development of surotomycin for the treatment of Clostridium difficile-associated diarrhea.

Trial registration

NCT02835118 and NCT02835105. Retrospectively registered, July 13 2016.

Population pharmacokinetics of ceftolozane/tazobactam in healthy volunteers, subjects with varying degrees of renal function and patients with bacterial infections

Ceftolozane/tazobactam is a novel antipseudomonal cephalosporin and β-lactamase inhibitor in clinical development for treatment of complicated urinary tract (cUTI) and intra-abdominal (cIAI) infections and nosocomial pneumonia. The population pharmacokinetics of ceftolozane/tazobactam were characterized in healthy volunteers, subjects with varying degrees of renal function, and patients with cIAI or cUTI. Serum concentration data from 376 adults who received ceftolozane/tazobactam in doses ranging from 500 to 3000 mg were analyzed to identify factors contributing to the pharmacokinetic variability. Ceftolozane/tazobactam pharmacokinetics were well described by a linear two-compartment model with first-order elimination and moderate between-subject variability in both clearance and volume of distribution (Vc). For both ceftolozane and tazobactam, clearance was highly correlated with renal function with creatinine clearance influencing exposure, and infection influencing Vc. Body weight was an additional covariate affecting the Vc of ceftolozane. Other covariates tested, such as age, body weight, sex, ethnicity, and presence of infection, had no clinically relevant effects on exposure. The final pharmacokinetic models adequately described the plasma concentrations of ceftolozane and tazobactam and form the basis for further modeling and simulation including evaluation of probability of target attainment in a diverse population with varying demographics, degrees of renal function, and infection status.

The effect of CYP3A inhibitors and inducers on the pharmacokinetics of telaprevir in healthy volunteers

AIM

To evaluate the effects of ketoconazole, rifampicin and efavirenz on the pharmacokinetics of telaprevir in healthy volunteers.

METHOD

Results from three clinical studies are described. (1) Volunteers received a single 750 mg dose telaprevir with and without a single 400 mg dose ketoconazole. (2) Volunteers received (a) 1250 mg telaprevir followed by three 750 mg doses given every 8 h and (b) four 1250 mg telaprevir doses given every 8 h, with a single 400 mg dose ketoconazole given with the fourth dose of telaprevir. (3) Volunteers received either a single 750 mg dose telaprevir with or without 600 mg once daily rifampicin, or 750 mg every 8 h telaprevir with and without 600 mg once daily efavirenz.

RESULTS

A single 400 mg dose of ketoconazole increased single dose telaprevir exposure: the geometric least-squares mean ratio (GLSMR, with 90% confidence limits) was 1.24 (1.10, 1.41) for C(max) and 1.62 (1.45, 1.81) for AUC(0,∞). However, after multiple doses of telaprevir, there was no discernible effect of ketoconazole on telaprevir exposure. Co-administration of rifampicin at steady-state markedly reduced single dose telaprevir exposure with GLSMRs of 0.14 (0.11, 0.18) for C(max) and 0.08 (0.07, 0.11) for AUC(0,∞), whereas efavirenz had a smaller effect on telaprevir exposure when both drugs were co-administered at steady-state, with GLSMRs of 0.91 (0.81, 1.02) for C(max) , 0.53 (0.44, 0.65) for C(min), and 0.74 (0.65, 0.84) for AUC(0,8 h).

CONCLUSION

CYP3A inducers, rifampicin and efavirenz, can reduce telaprevir exposure to varying degrees based on their potency. The effect of ketoconazole as an inhibitor of telaprevir metabolism is more pronounced after a single dose of telaprevir than after repeated administration.

Intrapulmonary penetration of ceftolozane/tazobactam and piperacillin/tazobactam in healthy adult subjects

OBJECTIVES

Appropriate antibiotic exposure at the site of infection is important for clinically effective therapy. This study compared the epithelial lining fluid (ELF) penetration of ceftolozane/tazobactam, which has potent in vitro activity against many Gram-negative pathogens causing nosocomial pneumonia, with that of piperacillin/tazobactam in healthy adult volunteers.

METHODS

In this Phase 1, open-label trial, 51 healthy adult subjects were randomized to receive three doses of either ceftolozane/tazobactam 1.5 g administered every 8 h via a 60 min infusion or piperacillin/tazobactam 4.5 g administered every 6 h via a 30 min infusion. Serial blood samples were obtained for determination of plasma drug concentrations. Bronchoscopy and bronchoalveolar lavage were performed at pre-specified timepoints in five subjects per timepoint in each treatment group to determine the ELF drug concentration. The penetration of individual analytes into the ELF was determined from the ratio of the area under the plasma concentration-time curve in ELF to that in plasma (AUC(ELF)/AUC(plasma)).

RESULTS

Plasma and ELF concentrations of ceftolozane, piperacillin and tazobactam increased rapidly, reaching maximal concentrations at the end of the infusion. Mean maximum concentration and AUC from time 0 to the end of the dosing interval (AUC(0-τ)) for ceftolozane in ELF were 21.8 mg/L and 75.1 mg·h/L, respectively. Corresponding values for piperacillin were 58.8 mg/L and 94.5 mg·h/L. The ELF/plasma AUC ratio for ceftolozane was 0.48 compared with 0.26 for piperacillin.

CONCLUSION

This study demonstrated that ceftolozane penetrated well into the ELF following parenteral administration of ceftolozane/tazobactam.

Merimepodib, pegylated interferon, and ribavirin in genotype 1 chronic hepatitis C pegylated interferon and ribavirin nonresponders

Merimepodib (MMPD) is an orally administered, inosine monophosphate dehydrogenase inhibitor that has shown antiviral activity in nonresponders with chronic hepatitis C (CHC) when combined with pegylated interferon alfa 2a (Peg-IFN-alfa-2a) and ribavirin (RBV). We conducted a randomized, double-blind, multicenter, phase 2b study to evaluate the antiviral activity, safety, and tolerability of MMPD in combination with Peg-IFN-alfa-2a and RBV in patients with genotype 1 CHC who were nonresponders to prior therapy with Peg-IFN and RBV. Patients received 50 mg MMPD, 100 mg MMPD, or placebo every 12 hours, in addition to Peg-IFN-alfa-2a and RBV, for 24 weeks. Patients with a 2-log or more decrease from baseline or undetectable hepatitis C virus (HCV) RNA levels at week 24 were then eligible to continue Peg-IFN-alfa-2a and RBV for a further 24 weeks, followed by 24 weeks of follow-up. The primary efficacy endpoint was sustained virological response (SVR) rate at week 72 in all randomized patients who received at least one dose of study drug and had a history of nonresponse to standard therapy. A total of 354 patients were randomized to treatment (117 to placebo; 119 to 50 mg MMPD; 118 to 100 mg MMPD), and 286 completed the core study. The proportion of patients who achieved SVR was similar among the treatment groups: 6% (6/107) for 50 mg MMPD, 4% (5/112) for 100 mg MMPD, and 5% (5/104) for placebo (P = 0.8431). Adverse-event profiles for the MMPD combination groups were similar to that for Peg-IFN-alfa and RBV alone. Nausea, arthralgia, cough, dyspnea, neutropenia, and anemia were more common in patients taking MMPD.

CONCLUSION

The addition of MMPD to Peg-IFN-alfa-2a and RBV combination therapy did not increase the proportion of nonresponder patients with genotype 1 CHC achieving an SVR.

Inhibitors of hepatitis C virus NS3.4A protease. Effect of P4 capping groups on inhibitory potency and pharmacokinetics

Reversible tetrapeptide-based compounds have been shown to effectively inhibit the hepatitis C virus NS3.4A protease. Inhibition of viral replicon RNA production in Huh-7 cells has also been demonstrated. We show herein that the inclusion of hydrogen bond donors on the P4 capping group of tetrapeptide-based inhibitors result in increased binding potency to the NS3.4A protease. The capping groups also impart significant effects on the pharmacokinetic profile of these inhibitors.

Preclinical profile of VX-950, a potent, selective, and orally bioavailable inhibitor of hepatitis C virus NS3-4A serine protease

VX-950 is a potent, selective, peptidomimetic inhibitor of the hepatitis C virus (HCV) NS3-4A serine protease, and it demonstrated excellent antiviral activity both in genotype 1b HCV replicon cells (50% inhibitory concentration [IC50] = 354 nM) and in human fetal hepatocytes infected with genotype 1a HCV-positive patient sera (IC50 = 280 nM). VX-950 forms a covalent but reversible complex with the genotype 1a HCV NS3-4A protease in a slow-on, slow-off process with a steady-state inhibition constant (K(i)*) of 7 nM. Dissociation of the covalent enzyme-inhibitor complex of VX-950 and genotype 1a HCV protease has a half-life of almost an hour. A >4-log10 reduction in the HCV RNA levels was observed after a 2-week incubation of replicon cells with VX-950, with no rebound of viral RNA observed after withdrawal of the inhibitor. In several animal species, VX-950 exhibits a favorable pharmacokinetic profile with high exposure in the liver. In a recently developed HCV protease mouse model, VX-950 showed excellent inhibition of HCV NS3-4A protease activity in the liver. Therefore, the overall preclinical profile of VX-950 supports its candidacy as a novel oral therapy against hepatitis C.