Safety and Tolerability of Doripenem in Hospitalized Children With Complicated Intra-Abdominal Infection, Complicated Urinary Tract Infections and Pneumonia.

Three multicenter, randomized, controlled studies evaluated doripenem in children 3 months to <18 years of age, with complicated intra-abdominal or urinary tract infections and bacterial pneumonia.In the 66 patients treated with doripenem before early termination of the studies for nonsafety reasons, doripenem was safe and generally well tolerated. Low enrollment limited ability to assess benefits and risks of doripenem in children.

Open-Label Study To Evaluate the Single-Dose Pharmacokinetics, Safety, and Tolerability of Doripenem in Infants Less than 12 Weeks in Chronological Age.

Doripenem, a parenteral carbapenem with broad-spectrum activity against aerobic Gram-negative and Gram-positive and anaerobic pathogens, is currently approved for use in adults in the United States and European Union. Single-dose doripenem pharmacokinetics in 52 infants <12 weeks in chronological age were investigated in this phase 1 study. Hospitalized, medically stable infants <12 weeks in chronological age were stratified into 6 groups based on chronological and gestational age designed to reflect increasing renal maturation and decreasing volume of distribution (Vz) for ß-lactam antimicrobials during the first 3 months of life. Subjects received single-dose doripenem (5 mg/kg of body weight for <8 weeks and 8 mg/kg for ≥8 weeks in chronological age) administered intravenously over 1 h. Plasma samples were obtained immediately before the end of the infusion and 1.5, 3, and 7 h after the start of the infusion. Urine was obtained by indwelling catheter during the 8 h following infusion. Doripenem showed linear pharmacokinetics across the 6 age groups. Neonates (<4 weeks in chronological age) had increased mean exposure (area under the plasma concentration-time curve from time zero to infinite time [AUC∞], 45.7 versus 32.4 µg · h/ml), longer elimination half-life (2.98 versus 1.79 h), and lower clearance (2.03 versus 3.03 ml/min/kg) compared with infants >4 weeks. Mean Vz was highest in subjects with the earliest gestational age (<32 weeks): 0.564 liter/kg for neonates and 0.548 liter/kg for infants. Single-dose pharmacokinetics of doripenem administered as a 1-hour infusion in term and preterm infants <12 weeks in chronological age were similar to what has been observed in neonates and very young infants with other carbapenems. Single-dose doripenem was generally safe and well tolerated. (This study has been registered with ClinicalTrials.gov under registration no. NCT01381848 and with EudraCT under registration no. 2009-014387-20.).

A randomized trial of 7-day doripenem versus 10-day imipenem-cilastatin for ventilator-associated pneumonia.

INTRODUCTION: The aim of this study was to compare a 7-day course of doripenem to a 10-day course of imipenem-cilastatin for ventilator-associated pneumonia (VAP) due to Gram-negative bacteria. METHODS: This was a prospective, double-blinded, randomized trial comparing a fixed 7-day course of doripenem one gram as a four-hour infusion every eight hours with a fixed 10-day course of imipenem-cilastatin one gram as a one-hour infusion every eight hours (April 2008 through June 2011). RESULTS: The study was stopped prematurely at the recommendation of the Independent Data Monitoring Committee that was blinded to treatment arm assignment and performed a scheduled review of data which showed signals that were close to the pre-specified stopping limits. The final analyses included 274 randomized patients. The clinical cure rate at the end of therapy (EOT) in the microbiological intent-to-treat (MITT) population was numerically lower for patients in the doripenem arm compared to the imipenem-cilastatin arm (45.6% versus 56.8%; 95% CI, -26.3% to 3.8%). Similarly, the clinical cure rate at EOT was numerically lower for patients with Pseudomonas aeruginosa VAP, the most common Gram-negative pathogen, in the doripenem arm compared to the imipenem-cilastatin arm (41.2% versus 60.0%; 95% CI, -57.2 to 19.5). All cause 28-day mortality in the MITT group was numerically greater for patients in the doripenem arm compared to the imipenem-cilastatin arm (21.5% versus 14.8%; 95% CI, -5.0 to 18.5) and for patients with P. aeruginosa VAP (35.3% versus 0.0%; 95% CI, 12.6 to 58.0). CONCLUSIONS: Among patients with microbiologically confirmed late-onset VAP, a fixed 7-day course of doripenem was found to have non-significant higher rates of clinical failure and mortality compared to a fixed 10-day course of imipenem-cilastatin. Consideration should be given to treating patients with VAP for more than seven days to optimize clinical outcome. TRIAL REGISTRATION: ClinicalTrials.gov: NCT00589693.

Doripenem dosing recommendations for critically ill patients receiving continuous renal replacement therapy.

Doripenem dosing regimens for patients receiving continuous venovenous hemofiltration (CVVH) and continuous venovenous hemodiafiltration (CVVHDF) were devised based on an established efficacy criterion (free plasma doripenem concentrations above the minimum inhibitory concentration [fT > MIC] of 1 mg/L for ≥35% of the dosing interval) while maintaining exposure below that with the highest studied dose of 1000 mg infused over 1 hour every 8 hours in healthy subjects. Simulations were utilized to assure ≥90% probability of achieving the efficacy criterion with the recommended doripenem regimens. Inflated intersubject variability of 40% (coefficient of variation) was used for pharmacokinetic parameters (representative of clinical variation) and nonrenal clearance was doubled to account for potential changes with acute renal insufficiency. Results indicate that a reduction in doripenem dose will be needed for critically ill patients receiving CVVH or CVVHDF. This work was conducted to fulfill a health authority request and resulted in the addition of dosing recommendations to the Doribax Summary of Product Characteristics.

Pharmacokinetics of single-dose doripenem in adults with cystic fibrosis.

The pharmacokinetics of doripenem and doripenem-M-1 (inactive metabolite) were evaluated in an open-label, 2-period, single-sequence study in which single 1-g and 2-g doses of doripenem were administered intravenously over 4 hours to adult patients with cystic fibrosis (CF). The systemic exposure to doripenem and doripenem-M-1, as measured by observed apparent maximum plasma concentration (C(max)) and area under the plasma concentration-time curve (AUC), increased approximately proportionally to the increase in dose. Other pharmacokinetic parameters of doripenem and doripenem-M-1, including clearance, volume of distribution, and elimination half-life, were similar for the 1-g and 2-g doses. The results from this study were also compared with those from a previous study in adult healthy volunteers (HVs) without CF, from a previously conducted pharmacokinetic study, who received single doses of 500 mg and 1 g doripenem administered over 4 hours. The pharmacokinetics of doripenem in adult patients with CF are similar to those from adult HVs, noting some differences in the disposition when comparing body mass index-adjusted pharmacokinetic parameters.

Influence of continuous venovenous hemofiltration and continuous venovenous hemodiafiltration on the disposition of doripenem.

The pharmacokinetics, safety, and tolerability of a single 1-hour, 500-mg intravenous infusion of doripenem were assessed in dialysis-dependent subjects with stage 5 chronic kidney disease undergoing continuous renal replacement therapy (CRRT) via 12-hour continuous venovenous hemofiltration (CVVH) (n = 6) or continuous venovenous hemodiafiltration (CVVHDF) (n = 5). Healthy volunteers were also assessed (n = 12). Concentrations of doripenem and the primary metabolite doripenem-M-1 were measured in plasma and ultrafiltrate or ultrafiltrate/dialysate by a validated liquid chromatography-tandem mass spectrometry method. In dialysis-dependent subjects, levels of systemic exposure to doripenem and doripenem-M-1 were approximately 3- and 5-fold greater, respectively, than those in healthy subjects: for doripenem, 98 µg·h/ml for CVVH and 77 µg·h/ml for CVVHDF versus 32 µg·h/ml for healthy subjects, and for doripenem-M-1, 24 µg·h/ml for CVVH and 22 µg·h/ml for CVVHDF versus 4.7 µg·h/ml for healthy subjects. The mean sieving coefficients and saturation coefficients were >0.67 for both doripenem and doripenem-M-1. During CVVH and CVVHDF, respectively, the percentages of administered doripenem dose removed were 38% and 29%, and clearances of doripenem were 22 and 25 ml/min. Both CVVH and CVVHDF efficiently removed doripenem and doripenem-M-1. Despite significant removal of drug by CVVH and CVVHDF, a single 1-hour, 500-mg doripenem infusion produced significantly higher plasma concentrations of doripenem, higher systemic exposure (area under the plasma concentration-time curve from time zero to 12 h after the start of infusion [AUC(0-12)]), and longer half-life (t(1/2)) in subjects receiving CVVH or CVVHDF than in healthy volunteers. The recovery of drug in ultrafiltrate and ultrafiltrate/dialysate and the enhanced rate of reduction of plasma concentrations indicate that CVVH and CVVHDF significantly augmented residual total body clearance of doripenem in subjects receiving CRRT. Doripenem dosage regimens for patients receiving CRRT thus need to be adjusted.

Pharmacokinetics, safety, and tolerability of doripenem after 0.5-, 1-, and 4-hour infusions in healthy volunteers.

The pharmacokinetics, safety, and tolerability of doripenem in healthy subjects were evaluated in 2 studies. Study 1 was a double-blind, randomized, placebo-controlled dose-escalation study in which doripenem was administered for 7 days by infusion over 30 minutes (500 mg) or 1 hour (1000 mg). Study 2 was an open-label, randomized, 3-way crossover study in which each subject received a single dose of each of the following doripenem treatments on separate occasions: 500 mg infused over 1 hour, 500 mg infused over 4 hours, and 1000 mg infused over 4 hours. Doripenem exhibited linear pharmacokinetics with concordance between the studies for pharmacokinetic parameters. Doripenem did not accumulate with repeated dosing over 7 days. The area under the plasma concentration-time curve (AUC) for doripenem 500 mg infused over 1 hour versus 4 hours was bioequivalent, and the AUC and Cmax increased proportionally with dose for the 500- and 1000-mg doses administered over 4 hours. These results, along with the stability profile of doripenem, support its use as a prolonged infusion. All regimens of doripenem were safe and well tolerated.

Disposition, metabolism, and excretion of [14C]doripenem after a single 500-milligram intravenous infusion in healthy men.

In this open-label, single-center study, eight healthy men each received a single 500-mg dose of [(14)C]doripenem, containing 50 microCi of [(14)C]doripenem, administered as a 1-h intravenous infusion. The concentrations of unchanged doripenem and its primary metabolite (doripenem-M-1) resulting from beta-lactam ring opening were measured in plasma and urine by a validated liquid chromatography method coupled to a tandem mass spectrometry assay. Total radioactivity was measured in blood, plasma, urine, and feces by liquid scintillation counting. Further metabolite profiling was conducted on urine samples using liquid chromatography coupled to radiochemical detection and high-resolution mass spectrometry. Unchanged doripenem and doripenem-M-1 accounted for means of 80.7% and 12.7% of the area under the plasma total-radioactivity-versus-time curve (area under the concentration-time curve extrapolated to infinity) and exhibited elimination half-lives of 1.1 and 2.5 h, respectively. Total clearance of doripenem was 16 liters/h, and renal clearance was 12.5 liters/h. At 7 days after the single dose, 95.3% of total doripenem-related radioactivity was recovered in urine and 0.72% in feces. A total mean of 97.2% of the administered dose was excreted in the urine as unchanged doripenem (78.7% +/- 5.7%) and doripenem-M-1 (18.5% +/- 2.6%). Most of the urinary recovery occurred within 4 h of dosing. Three additional minor metabolites were identified in urine: the glycine and taurine conjugates of doripenem-M-1 and oxidized doripenem-M-1. These results show that doripenem is predominantly eliminated in urine as unchanged drug, with only a fraction metabolized to doripenem-M-1 and other minor metabolites.

The effect of food on the pharmacokinetics of a dual angiotensin-converting enzyme/neutral endopeptidase inhibitor, M100240.

M100240 is a thioester of MDL 100,173, a dual angiotensin-converting enzyme (ACE)/neutral endopeptidase (NEP) inhibitor. Clinical studies have shown that M100240 is capable of decreasing ACE activity and angiotensin II concentrations while increasing plasma renin activity and potentiating the effects of atrial natriuretic peptide. This may result in a unique treatment benefit in disease states characterized by intravascular volume or sodium overload or increased venous pressure. The pharmacokinetics of MDL 100,173 were evaluated in 30 healthy subjects in an open-label, randomized, 2-period crossover design. Subjects received a single oral dose of 50 mg of M100240 administered with a high-fat meal and separately under fasted conditions. Serial plasma concentrations of M100240 and MDL 100,173 were analyzed, and pharmacokinetic parameters were calculated with noncompartmental methods. The intrasubject percent coefficient of variation for MDL 100,173 C(max) and AUC(0-24h) were less than 20%, indicating that this agent is a moderately variable drug. Although AUC(0-24h) was within the protocol-defined range of 80% to 125%, the lower limit of the 90% confidence interval for C(max) fell outside of the 70% to 143% range. Absence of a food effect on the pharmacokinetic profile of 50 mg of M100240 could therefore not be demonstrated. This finding is not surprising based on the documented food effect with the sulfhydryl-containing ACE inhibitor, captopril. Clinical significance of this pharmacokinetic food effect is unlikely, as the magnitude of pharmacodynamic response is probably better correlated with AUC than a single-point determination of C(max). Single oral doses of 50 mg of M100240 were safe and well tolerated under fed and fasted conditions.

No clinically relevant CYP3A induction with the dual angiotensin-converting enzyme/neutral endopeptidase inhibitor, M100240.

M100240, an acetate thioester of MDL 100,173, is a dual angiotensin-converting enzyme/neutral endopeptidase inhibitor currently in Phase II development. M100240 and MDL 100,173 were evaluated in an in vitro cytochrome P450 human hepatocyte model for enzyme induction. Although a dose-dependent CYP3A induction was observed between 10 and 100 microM, at 1 microM-which approaches clinically relevant plasma concentrations in humans-there was no evidence of CYP3A induction. An in vitro reporter gene assay also demonstrated the CYP3A isozyme induction potential of M100240 and MDL 100,173 with an EC(50) approximately 1.5 microM. The present study evaluated the potential for CYP3A enzyme induction in healthy volunteers. In an open-label, single-sequence, replicate-design study using midazolam as a CYP3A probe in 13 healthy volunteers, we found no evidence of clinically relevant CYP3A induction after multiple-dose administration of 50 mg M100240 orally once daily for 15 days. Single and multiple doses of M100240 increased the midazolam AUC(0-24 h) about 1.6-fold compared to baseline, suggesting weak CYP3A inhibition. Concomitant administration of midazolam and M100240 was generally safe and well tolerated. Although in vitro CYP3A induction at exposures in excess of clinically relevant human plasma concentrations has been demonstrated, there is no clinical evidence of CYP3A induction with M100240 administration at proposed therapeutic doses.