Bedaquiline safety, efficacy, utilization and emergence of resistance following treatment of multidrug-resistant tuberculosis patients in South Africa: a retrospective cohort analysis.

BACKGROUND: This retrospective cohort study assessed benefits and risks of bedaquiline treatment in multidrug-resistant-tuberculosis (MDR-TB) combination therapy by evaluating safety, effectiveness, drug utilization and emergence of resistance to bedaquiline. METHODS: Data were extracted from a register of South African drug-resistant-tuberculosis (DR-TB) patients (Electronic DR-TB Register [EDRWeb]) for newly diagnosed patients with MDR-TB (including pre-extensively drug-resistant [XDR]-TB and XDR-TB and excluding rifampicin-mono-resistant [RR]-TB, as these patients are by definition not multidrug-resistant), receiving either a bedaquiline-containing or non-bedaquiline-containing regimen, at 14 sites in South Africa. Total duration of treatment and follow-up was up to 30 months, including 6 months' bedaquiline treatment. WHO treatment outcomes within 6 months after end-of-treatment were assessed in both patient groups. Longer term mortality (up to 30 months from treatment start) was evaluated through matching to the South African National Vital Statistics Register. Multivariable Cox proportional hazards analyses were used to predict association between receiving a bedaquiline-containing regimen and treatment outcome. RESULTS: Data were extracted from EDRWeb for 5981 MDR-TB patients (N = 3747 bedaquiline-treated; N = 2234 non-bedaquiline-treated) who initiated treatment between 2015 and 2017, of whom 40.7% versus 80.6% had MDR-TB. More bedaquiline-treated than non-bedaquiline-treated patients had pre-XDR-TB (27.7% versus 9.5%) and XDR-TB (31.5% versus 9.9%) per pre-2021 WHO definitions. Most patients with treatment duration data (94.3%) received bedaquiline for 6 months. Treatment success (per pre-2021 WHO definitions) was achieved in 66.9% of bedaquiline-treated and 49.4% of non-bedaquiline-treated patients. Death was reported in fewer bedaquiline-treated (15.4%) than non-bedaquiline-treated (25.6%) patients. Bedaquiline-treated patients had increased likelihood of treatment success and decreased risk of mortality versus non-bedaquiline-treated patients. In patients with evaluable drug susceptibility testing data, 3.5% of bedaquiline-susceptible isolates at baseline acquired phenotypic resistance. Few patients reported bedaquiline-related treatment-emergent adverse events (TEAEs) (1.8%), TEAE-related bedaquiline discontinuations (1.4%) and QTcF values > 500 ms (2.5%) during treatment. CONCLUSION: Data from this large cohort of South African patients with MDR-TB showed treatment with bedaquiline-containing regimens was associated with survival and effectiveness benefit compared with non-bedaquiline-containing regimens. No new safety signals were detected. These data are consistent with the positive risk-benefit profile of bedaquiline and warrant continued implementation in combination therapy for MDR-TB treatment.

Bedaquiline Drug Resistance Emergence Assessment in Multidrug-Resistant Tuberculosis (MDR-TB): a 5-Year Prospective In Vitro Surveillance Study of Bedaquiline and Other Second-Line Drug Susceptibility Testing in MDR-TB Isolates.

Bedaquiline Drug Resistance Emergence Assessment in Multidrug-resistant tuberculosis (MDR-TB) (DREAM) was a 5-year (2015 to 2019) phenotypic drug resistance surveillance study across 11 countries. DREAM assessed the susceptibility of 5,036 MDR-TB isolates of bedaquiline treatment-naive patients to bedaquiline and other antituberculosis drugs by the 7H9 broth microdilution (BMD) and 7H10/7H11 agar dilution (AD) MIC methods. Bedaquiline AD MIC quality control (QC) range for the H37Rv reference strain was unchanged, but the BMD MIC QC range (0.015 to 0.12 µg/ml) was adjusted compared with ranges from a multilaboratory, multicountry reproducibility study conforming to Clinical and Laboratory Standards Institute Tier-2 criteria. Epidemiological cutoff values of 0.12 µg/ml by BMD and 0.25 µg/ml by AD were consistent with previous bedaquiline breakpoints. An area of technical uncertainty or intermediate category was set at 0.25 µg/ml and 0.5 µg/ml for BMD and AD, respectively. When applied to the 5,036 MDR-TB isolates, bedaquiline-susceptible, -intermediate, and -resistant rates were 97.9%, 1.5%, and 0.6%, respectively, for BMD and 98.8%, 0.8%, and 0.4% for AD. Resistance rates were the following: 35.1% ofloxacin, 34.2% levofloxacin, 33.3% moxifloxacin, 1.5% linezolid, and 2% clofazimine. Phenotypic cross-resistance between bedaquiline and clofazimine was 0.4% in MDR-TB and 1% in pre-extensively drug-resistant (pre-XDR-TB)/XDR-TB populations. Coresistance to bedaquiline and linezolid and clofazimine and linezolid were 0.1% and 0.3%, respectively, in MDR-TB and 0.2% and 0.4%, respectively, in pre-XDR-TB/XDR-TB populations. Resistance rates to bedaquiline appear to be low in the bedaquiline-treatment-naive population. No treatment-limiting patterns for cross-resistance and coresistance have been identified with key TB drugs to date.

A Multimethod, Multicountry Evaluation of Breakpoints for Bedaquiline Resistance Determination.

Criteria defining bedaquiline resistance for tuberculosis have been proposed addressing an emerging concern. We evaluated bedaquiline phenotypic drug susceptibility testing (pDST) criteria using drug-resistant tuberculosis clinical isolates tested at five reference laboratories. Isolates were tested at the proposed bedaquiline MGIT960 and 7H11 agar proportion (AP) critical concentrations and also at higher dilutions. The epidemiological cutoff value for the broth microdilution (BMD) plates (frozen and dry) was investigated. Sanger sequencing was performed (atpE and Rv0678 genes) for any isolate testing resistant. The composite reference standard (CRS) defined susceptibility or resistance as is if all pDST methods agreed. If the pDST result was discordant, sequencing results were used for final classification. Geographically diverse and bedaquiline-unexposed isolates were tested (n = 495). The epidemiological cutoff value for BMD was confirmed to be 0.12 µg/ml. The majority of isolates were determined to be susceptible by all methods (467/495; 94.3%), and 28 were determined to be resistant by at least one method; 4 of these were determined to be resistant by all methods. Of the 28 resistant isolates, 12 harbored Rv0678 mutations exclusively. Isolates with insertions/deletions were more likely to be determined to be resistant by more than one method (5/7) compared to isolates with a single nucleotide polymorphism (1/5). Applying the CRS to 24 discordant pDST, BMD dry correctly detected most (15/24; 63%), followed by MGIT960 and BMD frozen (13/24; 61%) and lastly AP (12/24; 50%). Applying the CRS, the prevalence of bedaquiline resistance was 2.2% and ranged from 1.4 to 3.4%, depending on the method used. All methods performed well for bedaquiline susceptibility determination; however, resistance detected should be investigated by a second, alternative method.

Validation of Bedaquiline Phenotypic Drug Susceptibility Testing Methods and Breakpoints: a Multilaboratory, Multicountry Study.

Drug-resistant tuberculosis persists as a major public health concern. Alongside efficacious treatments, validated and standardized drug susceptibility testing (DST) is required to improve patient care. This multicountry, multilaboratory external quality assessment (EQA) study aimed to validate the sensitivity, specificity, and reproducibility of provisional bedaquiline MIC breakpoints and World Health Organization interim critical concentrations (CCs) for categorizing clinical Mycobacterium tuberculosis isolates as susceptible/resistant to the drug. Three methods were used: Middlebrook 7H11 agar proportion (AP) assay, broth microdilution (BMD) assay, and mycobacterial growth indicator tube (MGIT) assay. Each of the five laboratories tested the 40-isolate (20 unique isolates, duplicated) EQA panel at three time points. The study validated the sensitivity and specificity of a bedaquiline MIC susceptibility breakpoint of 0.12 µg/ml for the BMD method and WHO interim CCs of 1 µg/ml for MGIT and 0.25 µg/ml for the 7H11 AP methods. Categorical agreements between observed and expected results and sensitivities/specificities for correctly identifying an isolate as susceptible/resistant were highest at the 0.25, 0.12, and 1 µg/ml bedaquiline concentrations for the AP method, BMD (frozen or dry plates), and MGIT960, respectively. At these concentrations, the very major error rates for erroneously categorizing an isolate as susceptible when it was resistant were the lowest and within CLSI guidelines. The most highly reproducible bedaquiline DST methods were MGIT960 and BMD using dry plates. These findings validate the use of standardized DST methodologies and interpretative criteria to facilitate routine phenotypic bedaquiline DST and to monitor the emergence of bedaquiline resistance.

Epidemiological cut-offs for Sensititre susceptibility testing of Mycobacterium tuberculosis: interpretive criteria cross validated with whole genome sequencing.

Universal drug susceptibility testing (DST) is an important requirement of the End TB Strategy. The Sensititre broth micro-dilution assay (BMD) tests multiple drugs quantitatively. We defined interpretive criteria for this assay and analysed genotypic-phenotypic relationships. 385 Mycobacterium tuberculosis clinical isolates were processed for BMD and whole genome sequencing. The epidemiological cut-off value 99% (ECV99) amongst genotypically wild type (gWT) strains defined susceptibility. Minimum inhibitory concentration distributions of the resistance-associated variants (RAVs) for each drug were analysed. Susceptibility (µg/mL) criteria were determined as follows: rifampicin (≤0.125), isoniazid (≤0.25), ethambutol (≤2.0), moxifloxacin (≤0.5), levofloxacin (≤1.0), amikacin (≤2.0), kanamycin (≤8.0), capreomycin (≤4.0), clofazimine (≤0.25) and linezolid (≤2.0). Most drugs showed clear separation between gWT and RAV. Isoniazid showed a tri-modal pattern with 14/17 strains at ECV99 harbouring a fabG1 c. -15C > T RAV. Ethambutol RAVs at embB codons 306, 405 and 497 were responsible for resistance and showed differential distributions. Moxifloxacin RAVs (gyrA codon 90) were a dilution or two higher than the ECV99 while gyrB RAVs were uncommon and showed drug specific resistance propensity. Interpretive criteria established were robust facilitating progress towards universal DST and individualised precision medicine. This study demonstrates the value of quantitative DST to accurately interpret mutation data.

Defining Bedaquiline Susceptibility, Resistance, Cross-Resistance and Associated Genetic Determinants: A Retrospective Cohort Study.

BACKGROUND: Bedaquiline (BDQ) is a novel agent approved for use in combination treatment of multi-drug resistant tuberculosis (MDR-TB). We sought to determine BDQ epidemiological cut-off values (ECVs), define and assess interpretive criteria against putative resistance associated variants (RAVs), microbiological outcomes and cross resistance with clofazimine (CFZ). METHODS: A retrospective cohort study was conducted. Minimal inhibitory concentrations (MIC) to BDQ were determined using 7H9 broth microdilution (BMD) and MGIT960. RAVs were genetically characterised using whole genome sequencing. BDQ ECVs were determined using ECOFFinder and compared with 6-month culture conversion status and CFZ MICs. FINDINGS: A total of 391 isolates were analysed. Susceptible and intermediate categories were determined to have MICs of ≤0.125µg/ml and 0.25µg/ml using BMD and ≤1µg/ml and 2µg/ml using MGIT960 respectively. Microbiological failures occurred among BDQ exposed patients with a non-susceptible BDQ MIC, an Rv0678 mutation and ≤2 active drug classes. The Rv0678 RAVs were not the dominant mechanism of CFZ resistance and cross resistance was limited to isolates with an Rv0678 mutation. INTERPRETATION: Criteria for BDQ susceptibility are defined and will facilitate improved early detection of resistance. Cross- resistance between BDQ and CFZ is an emerging concern but in this study was primarily among those with an Rv0678 mutation.

A Multilaboratory, Multicountry Study To Determine MIC Quality Control Ranges for Phenotypic Drug Susceptibility Testing of Selected First-Line Antituberculosis Drugs, Second-Line Injectables, Fluoroquinolones, Clofazimine, and Linezolid.

Our objective was to establish reference MIC quality control (QC) ranges for drug susceptibility testing of antimycobacterials, including first-line agents, second-line injectables, fluoroquinolones, and World Health Organization category 5 drugs for multidrug-resistant tuberculosis using a 7H9 broth microdilution MIC method. A tier-2 reproducibility study was conducted in eight participating laboratories using Clinical Laboratory and Standards Institute (CLSI) guidelines. Three lots of custom-made frozen 96-well polystyrene microtiter plates were used and prepared with 2× prediluted drugs in 7H9 broth-oleic acid albumin dextrose catalase. The QC reference strain was Mycobacterium tuberculosis H37Rv. MIC frequency, mode, and geometric mean were calculated for each drug. QC ranges were derived based on predefined, strict CLSI criteria. Any data lying outside CLSI criteria resulted in exclusion of the entire laboratory data set. Data from one laboratory were excluded due to higher MIC values than other laboratories. QC ranges were established for 11 drugs: isoniazid (0.03 to 0.12 µg/ml), rifampin (0.03 to 0.25 µg/ml), ethambutol (0.25 to 2 µg/ml), levofloxacin (0.12 to 1 µg/ml), moxifloxacin (0.06 to 0.5 µg/ml), ofloxacin (0.25 to 2 µg/ml), amikacin (0.25 to 2 µg/ml), kanamycin (0.25 to 2 µg/ml), capreomycin (0.5 to 4 µg/ml), linezolid (0.25 to 2 µg/ml), and clofazimine (0.03 to 0.25 µg/ml). QC ranges could not be established for nicotinamide (pyrazinamide surrogate), prothionamide, or ethionamide, which were assay nonperformers. Using strict CLSI criteria, QC ranges against the M. tuberculosis H37Rv reference strain were established for the majority of commonly used antituberculosis drugs, with a convenient 7H9 broth microdilution MIC method suitable for use in resource-limited settings.

A Multilaboratory, Multicountry Study To Determine Bedaquiline MIC Quality Control Ranges for Phenotypic Drug Susceptibility Testing.

The aim of this study was to establish standardized drug susceptibility testing (DST) methodologies and reference MIC quality control (QC) ranges for bedaquiline, a diarylquinoline antimycobacterial, used in the treatment of adults with multidrug-resistant tuberculosis. Two tier-2 QC reproducibility studies of bedaquiline DST were conducted in eight laboratories using Clinical Laboratory and Standards Institute (CLSI) guidelines. Agar dilution and broth microdilution methods were evaluated. Mycobacterium tuberculosis H37Rv was used as the QC reference strain. Bedaquiline MIC frequency, mode, and geometric mean were calculated. When resulting data occurred outside predefined CLSI criteria, the entire laboratory data set was excluded. For the agar dilution MIC, a 4-dilution QC range (0.015 to 0.12 µg/ml) centered around the geometric mean included 95.8% (7H10 agar dilution; 204/213 observations with one data set excluded) or 95.9% (7H11 agar dilution; 232/242) of bedaquiline MICs. For the 7H9 broth microdilution MIC, a 3-dilution QC range (0.015 to 0.06 µg/ml) centered around the mode included 98.1% (207/211, with one data set excluded) of bedaquiline MICs. Microbiological equivalence was demonstrated for bedaquiline MICs determined using 7H10 agar and 7H11 agar but not for bedaquiline MICs determined using 7H9 broth and 7H10 agar or 7H9 broth and 7H11 agar. Bedaquiline DST methodologies and MIC QC ranges against the H37Rv M. tuberculosis reference strain have been established: 0.015 to 0.12 µg/ml for the 7H10 and 7H11 agar dilution MICs and 0.015 to 0.06 µg/ml for the 7H9 broth microdilution MIC. These methodologies and QC ranges will be submitted to CLSI and EUCAST to inform future research and provide guidance for routine clinical bedaquiline DST in laboratories worldwide.

Activity of doripenem versus comparators in subjects with baseline bacteraemia in six pooled phase 3 clinical trials.

An analysis of subjects with concurrent bacteraemia and either nosocomial pneumonia, complicated intra-abdominal infection or complicated urinary tract infection from six phase 3 clinical trials demonstrated similar cure rates and clearance of bacteraemia in patients treated with doripenem and comparator agents.

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.

In vitro Etest synergy of doripenem with amikacin, colistin, and levofloxacin against Pseudomonas aeruginosa with defined carbapenem resistance mechanisms as determined by the Etest method.

The applicability of Etest for synergy testing was evaluated in 100 carbapenem-nonsusceptible Pseudomonas aeruginosa isolates. Combinations of doripenem with amikacin, colistin, or levofloxacin were synergistic or additive against 67%, 31%, and 23% of isolates, respectively. The use of Etest was practical to evaluate the synergy of doripenem with other antipseudomonal agents.

Pharmacokinetic-pharmacodynamic-model-guided doripenem dosing in critically ill patients.

The growing number of infections caused by multidrug-resistant pathogens has prompted a more rational use of available antibiotics given the paucity of new, effective agents. Monte Carlo simulations were utilized to determine the appropriateness of several doripenem dosing regimens based on the probability of attaining the critical drug exposure metric of time that drug concentrations remain above the drug MIC (T>MIC) for 35% (and lower thresholds) of the dosing interval in >80 to 90% of the population (T>MIC 35% target). This exposure level generally correlates with in vivo efficacy for carbapenems. In patients with creatinine clearance of >50 ml/min, a 500-mg dose of doripenem infused over 1 h every 8 h is expected to be effective against bacilli with doripenem MICs of < or =1 microg/ml based on a T>MIC 35% target and MICs of < or =2 microg/ml based on lower targets. A longer, 4-hour infusion time improved target attainment in most cases, such that the T>MIC was adequate for pathogens with doripenem MICs as high as 4 microg/ml. Efficacy is expected for infections caused by pathogens with doripenem MICs of < or =2 microg/ml in patients with moderate renal impairment (creatinine clearance, 30 to 50 ml/min) who receive doripenem at 250 mg infused over 1 h every 8 h and in patients with severe impairment (creatinine clearance between 10 and 29 ml/min) who receive doripenem at 250 mg, infused over 1 h or 4 h, every 12 h. Results of pharmacokinetics/pharmacodynamics (PK/PD) modeling can guide dose optimization, thereby potentially increasing the clinical efficacy of doripenem against serious Gram-negative bacterial infections.

Worldwide experience with the use of doripenem against extended-spectrum-beta-lactamase-producing and ciprofloxacin-resistant Enterobacteriaceae: analysis of six phase 3 clinical studies.

The worldwide increase in fluoroquinolone-resistant and extended-spectrum beta-lactamase (ESBL)-producing Enterobacteriaceae pathogens has led to doripenem and other carbapenems assuming a greater role in the treatment of serious infections. We analyzed data from 6 phase 3 multinational doripenem clinical trials on ciprofloxacin-resistant Enterobacteriaceae isolates consisting of all genera (CIPRE) and ESBL-producing Enterobacteriaceae isolates consisting of Escherichia coli, Klebsiella spp., and Proteus spp. with ceftazidime MICs of >or=2 microg/ml (ESBLE) for prevalence by geographic region and disease type, in vitro activities of doripenem and comparator agents, and clinical or microbiologic outcomes in doripenem- and comparator-treated patients across disease types (complicated intra-abdominal infection [cIAI], complicated urinary tract infection [cUTI], and nosocomial pneumonia [NP]). Of 1,830 baseline Enterobacteriaceae isolates, 88 (4.8%) were ESBLE and 238 (13.0%) were CIPRE. The incidence of ESBLE was greatest in Europe (7.8%); that of CIPRE was higher in South America (15.9%) and Europe (14.4%). ESBLE incidence was highest in NP (12.9%) cases; that of CIPRE was higher in cUTI (18.3%) and NP (14.9%) cases. Against ESBLE and CIPRE, carbapenems appeared more active than other antibiotic classes. Among carbapenems, doripenem and meropenem were most potent. Doripenem had low MIC(90)s for CIPRE (0.5 microg/ml) and ESBLE (0.25 microg/ml). Doripenem and comparators were highly clinically effective in infections caused by Enterobacteriaceae, irrespective of their ESBL statuses. The overall cure rates were the same for doripenem (82%; 564/685) and the comparators (82%; 535/652) and similar for ESBLE (73% [16/22] versus 72% [21/29]) and CIPRE (68% [47/69] versus 52% [33/64]). These findings indicate that doripenem is an important therapeutic option for treating serious infections caused by ESBLE and CIPRE.

Meta-analysis of doripenem vs comparators in patients with pseudomonas infections enrolled in four phase III efficacy and safety clinical trials.

OBJECTIVE: Pseudomonas aeruginosa is a difficult-to-treat bacterial pathogen often isolated from patients with serious nosocomial infections. The goal of this analysis is to present the clinical and microbiologic effectiveness of doripenem in the treatment of infections due to P. aeruginosa. RESEARCH DESIGN AND METHODS: A meta-analysis was conducted on the subset of subjects enrolled in four randomized phase III clinical trials of doripenem in subjects with complicated intra-abdominal infections (cIAI) and nosocomial pneumonia/ventilator-associated pneumonia (NP/VAP) due to P. aeruginosa. Clinical and microbiologic success was determined by infection and across the two infections. RESULTS: Clinical success rates for modified intent-to-treat (mITT) subjects with P. aeruginosa in the cIAI and NP/VAP groups were 78.7% (37/47) and 59.6% (31/52), respectively, following treatment with doripenem versus 74.3% (26/35) and 32.8% (19/58), respectively, for subjects in the comparator groups (p < 0.05 for difference in success rates across infection types). Microbiologic eradication rates also favored doripenem, although the differences did not achieve statistical significance. The weighted difference (doripenem minus comparator) for the mITT population in clinical success rates between doripenem and the comparator agents was 16.0% (95% CI: 3.1%, 29.0%) and for microbiologic eradication rates was 9.1% (95% CI: -4.2%, 22.3%). The proportion of subjects reporting one or more treatment-emergent adverse events or serious adverse events was similar for doripenem and the comparator agents. Fourteen doripenem and 14 comparator subjects died during the study. Limitations of this retrospective meta-analysis also include the qualitative heterogeneity of the data, and a selected, narrow population of moderately ill clinical trial subjects included in the analysis. Due to limitations, these data may not be generalizable to all populations and should be considered hypothesis generating. CONCLUSION: The weighted difference in clinical success rates for subjects with cIAI and NP/VAP infections caused by P. aeruginosa was in favor of doripenem, with the relative benefit of doripenem compared with the comparator agents similar across the two infections.

Efficacy and tolerability of IV doripenem versus meropenem in adults with complicated intra-abdominal infection: a phase III, prospective, multicenter, randomized, double-blind, noninferiority study.

BACKGROUND: Complicated intra-abdominal infections (cIAIs) require surgical intervention and empiric antibacterial therapy. Doripenem, a broad-spectrum carbapenem, provides coverage of key gram-negative and -positive aerobes and anaerobes encountered in cIAI. OBJECTIVE: This study was designed to compare the efficacy and safety profile of doripenem and meropenem in hospitalized adult patients with cIAI. METHODS: In this prospective, multicenter, doubleblind, noninferiority study, hospitalized adults with cIAI were randomly assigned to receive doripenem 500 mg IV q8h or meropenem 1 g IV q8h. After a minimum of 9 doses and adequate clinical improvement (relative to before the start of IV study drug, decreased body temperature and white blood cell count, improved or absent signs and symptoms of cIAI, and return of normal bowel function), patients could be switched to oral amoxicillin/clavulanate. Antibacterial therapy (IV plus subsequent oral) was given for a total of 5 to 14 days. The coprimary efficacy end points were the clinical cure rate (complete resolution or significant improvement of signs or symptoms of the index infection) in patients microbiologically evaluable (>or=1 baseline pathogen isolated from an intra-abdominal culture that was susceptible to both IV study drug therapies) at the test-of-cure (TOC) visit (21-60 days after the completion of study drug therapy) and the clinical cure rate in the microbiological modified intent-to-treat (mMITT) population (a bacterial pathogen identified at baseline, regardless of its susceptibility to the study drug). Noninferiority was concluded if the lower limit of the 2-sided 95% CI for the difference (doripenem minus meropenem) in the proportion of patients classified as clinical cures was >or=-15%. RESULTS: A total of 476 patients were enrolled. The microbiologically evaluable population (319 patients) was 62.7% male and 67.7% white, with a mean age and weight of 46.7 years and 77.2 kg, respectively. In this population, doripenem and meropenem were associated with clinical cure rates at the TOC visit of 85.9% and 85.3%, respectively. The corresponding treatment difference was 0.6% (95% CI, -7.7% to 9.0%); this difference was not statistically significant. Similarly, in the mMITT population (385 patients), the clinical cure rates were 77.9% and 78.9%, respectively, and the corresponding 1.0% treatment difference was not statistically significant (95% CI, -9.7% to 7.7%). Clinical cure rates were not significantly different between the 2 treatment arms in key subgroups (eg, age, sex, race, baseline Acute Physiology and Chronic Health Evaluation II score, primary infection site). Microbiological eradication rates for common pathogens isolated at study entry were not significantly different between the 2 treatment groups. Doripenem was well tolerated in the population studied. In the intent-to-treat population (471 patients), 83.0% and 78.0% of patients experienced >or=1 adverse event (AE) and 13.2% and 14.0% experienced >or=1 serious AE in the doripenem and meropenem treatment arms, respectively. In the doripenem and meropenem treatment arms, AEs resulted in study drug discontinuation in 5.1% and 2.1% of patients and death in 2.1% and 3.0% of patients, respectively. CONCLUSIONS: The present study found that doripenem (500 mg q8h) was effective in the treatment of cIAI, was therapeutically noninferior to meropenem (1 g q8h), with a safety profile not significantly different from that of meropenem in this selected population of patients with cIAI.

Efficacy and safety of doripenem versus piperacillin/tazobactam in nosocomial pneumonia: a randomized, open-label, multicenter study.

OBJECTIVE: Doripenem is a new carbapenem that has broad-spectrum activity against bacterial pathogens commonly responsible for nosocomial pneumonia (NP). It has several advantages over currently available carbapenems and other classes of drugs used in this indication. This prospective, randomized, open-label, multicenter study was designed to establish whether doripenem was noninferior to piperacillin/tazobactam in NP. METHODS: Adults (n=448) with signs and symptoms of NP, including non-ventilated patients and those ventilated for <5 days, were stratified by ventilation mode, illness severity (Acute Physiology and Chronic Health Evaluation II score), and geographic region and then randomly allocated to treatment with doripenem 500 mg every 8 h by a 1-h intravenous (IV) infusion or piperacillin/tazobactam 4.5 g every 6 h by 30-min IV infusion. After receiving IV study drug for at least 72 h, eligible patients could be switched to oral levofloxacin 750 mg once daily. Antibiotic therapy was continued for a total of 7-14 days. The primary endpoint was the clinical cure rate, assessed 7-14 days after treatment completion, in clinically evaluable patients and in the clinical modified intent-to-treat population (cMITT). TRIAL REGISTRATION: ClinicalTrials.gov, NCT00211003. RESULTS: Doripenem was noninferior to piperacillin/tazobactam. Clinical cure rates in clinically evaluable patients (n=253) were 81.3% in the doripenem arm and 79.8% in the piperacillin/tazobactam arm (between-treatment difference: 1.5%; 95% confidence interval [CI], -9.1 to 12.1%) and in the cMITT population 69.5% and 64.1%, respectively, (between-treatment difference: 5.4%; 95% CI, -4.1 to 14.8%). Baseline resistance of Klebsiella pneumoniae and Pseudomonas aeruginosa to piperacillin/tazobactam was 44% and 26.9%, respectively; a doripenem minimum inhibitory concentration (MIC) >8 mug/mL occurred in 0% and 7.7%, respectively. Favorable microbiological outcome rates against Gram-negative pathogens were numerically higher with doripenem than with piperacillin/tazobactam, but the difference was not statistically significant. Both study drugs were generally well tolerated, as only 16.1% and 17.6% of patients receiving doripenem and piperacillin/tazobactam, respectively, had a drug-related adverse event. Study limitations included the open-label design, the low rate of monotherapy (adjunctive use of aminoglycoside was required when P. aeruginosa was suspected), and the exclusion of the most critically ill and immunocompromized patients. CONCLUSIONS: Doripenem was clinically and microbiologically effective in patents with NP, including those with early-onset ventilator-associated pneumonia, and was therapeutically noninferior to piperacillin/tazobactam.

Efficacy and safety of intravenous infusion of doripenem versus imipenem in ventilator-associated pneumonia: a multicenter, randomized study.

OBJECTIVE: Doripenem is an investigational carbapenem with broad-spectrum activity against gram-negative and gram-positive pathogens, including multidrug-resistant strains, commonly responsible for ventilator-associated pneumonia (VAP). This large, phase III study compared doripenem with imipenem for the treatment of ventilator-associated pneumonia. DESIGN: Prospective, multicenter, parallel randomized, active-controlled, open-label study. SETTING: Intensive care units. PATIENTS: Adults (N = 531) who met clinical and radiologic criteria for ventilator-associated pneumonia. INTERVENTIONS: Patients were stratified by duration of mechanical ventilation (< 5 vs. > or = 5 days), severity of illness (Acute Physiology and Chronic Health Evaluation II score < or = 15 vs. > 15), and geographic region and then randomly assigned to doripenem 500 mg every 8 hrs via a 4-hr intravenous infusion or imipenem 500 mg every 6 hrs or 1000 mg every 8 hrs via 30- or 60-min intravenous infusions, respectively, for 7-14 days. MEASUREMENTS AND MAIN RESULTS: The primary efficacy end points were the clinical cure rates in the clinical modified intent-to-treat (cMITT) and clinically evaluable populations. Doripenem was noninferior to imipenem (lower boundary of 95% confidence interval around the difference between treatments > or = -20%). Clinical cure rates were 68.3% (doripenem) and 64.2% (imipenem) in the clinically evaluable and 59.0% (doripenem) and 57.8% (imipenem) in the cMITT populations. In patients with Pseudomonas aeruginosa, clinical cure was 80.0% (doripenem) and 42.9% (imipenem) (p not significant); microbiological cure was 65.0% (doripenem) and 37.5% (imipenem). Only 18% (5 of 28) of P. aeruginosa isolates had minimum inhibitory concentration > or = 8 microg/mL at baseline or following therapy in the doripenem arm compared with 64% (16 of 25) in the imipenem treatment group (p = .001). Clinical cure rate was higher with doripenem than imipenem at higher Acute Physiology and Chronic Health Evaluation II scores and older ages. Doripenem was generally well tolerated. CONCLUSIONS: In this large, phase III study of patients with ventilator-associated pneumonia, a 4-hr intravenous infusion of doripenem was clinically efficacious and therapeutically noninferior to imipenem.

A multivalent approach to drug discovery for novel antibiotics.

The design, synthesis and antibacterial activity of novel glycopeptide/beta-lactam heterodimers is reported. Employing a multivalent approach to drug discovery, vancomycin and cephalosporin synthons, A and B respectively, were chemically linked to yield heterodimer antibiotics. These novel compounds were designed to inhibit Gram-positive bacterial cell wall biosynthesis by simultaneously targeting the principal cellular targets of both glycopeptides and beta-lactams. The antibiotics 8a-f displayed remarkable potency against a wide range of Gram-positive organisms including methicillin-resistant Staphylococcus aureus (MRSA). Compound 8e demonstrated excellent bactericidal activity against MRSA (ATCC 33591) and initial evidence supports a multivalent mechanism of action for this important new class of antibiotic.

Exploring the positional attachment of glycopeptide/beta-lactam heterodimers.

Further investigations towards novel glycopeptide/beta-lactam heterodimers are reported. Employing a multivalent approach to drug discovery, vancomycin and cephalosporin synthons, 4, 2, 5 and 10, 18, 25 respectively, were chemically linked to yield heterodimer antibiotics. These novel compounds were designed to inhibit Gram-positive bacterial cell wall biosynthesis by simultaneously targeting the principal cellular targets of both glycopeptides and beta-lactams. The positional attachment of both the vancomycin and the cephalosporin central cores has been explored and the SAR is reported. This novel class of bifunctional antibiotics 28-36 all displayed remarkable potency against a wide range of Gram-positive organisms, including methicillin-resistant Staphylococcus aureus (MRSA). A subset of compounds, 29, 31 and 35 demonstrated excellent bactericidal activity against MRSA (ATCC 33591) and 31 and 35 also exhibited superb in vivo efficacy in a mouse model of MRSA infection. As a result of this work compound 35 was selected as a clinical candidate, TD-1792.