| 2021 | The Enzymes of the Rifamycin Antibiotic Resistome. | Acc Chem Res | Rifamycin antibiotics include the WHO essential medicines rifampin, rifabutin, and rifapentine. These are semisynthetic derivatives of the natural product Rifamycins, originally isolated from the soil bacterium . These antibiotics are primarily used to treat mycobacterial infections, including tuberculosis. Rifamycins act by binding to the β-subunit of bacterial RNA polymerase, inhibiting transcription, which results in cell death. These antibiotics consist of a naphthalene core spanned by a polyketide bridge. This structure presents a unique 3D configuration that engages RNA polymerase through a series of hydrogen bonds between hydroxyl groups linked to the naphthalene core and C21 and C23 of the bridge. This binding occurs not in the enzyme active site where template-directed RNA synthesis occurs but instead in the RNA exit tunnel, thereby blocking productive formation of full-length RNA. In their clinical use to treat tuberculosis, resistance to Rifamycin antibiotics arises principally from point mutations in RNA polymerase that decrease the antibiotic's affinity for the binding site in the RNA exit tunnel. In contrast, the Rifamycin resistome of environmental mycobacteria and actinomycetes is much richer and diverse. In these organisms, Rifamycin resistance includes many different enzymatic mechanisms that modify and alter the antibiotic directly, thereby inactivating it. These enzymes include ADP ribosyltransferases, glycosyltransferases, phosphotransferases, and monooxygenases.ADP ribosyltransferases catalyze group transfer of ADP ribose from the cofactor NAD, which is more commonly deployed for metabolic redox reactions. ADP ribose is transferred to the hydroxyl linked to C23 of the antibiotic, thereby sterically blocking productive interaction with RNA polymerase. Like ADP ribosyltransferases, Rifamycin glycosyl transferases also modify the hydroxyl of position C23 of Rifamycins, transferring a glucose moiety from the donor molecule UDP-glucose. Unlike other antibiotic resistance kinases that transfer the γ-phosphate of ATP to inactivate antibiotics such as aminoglycosides or macrolides, Rifamycin phosphotransferases are ATP-dependent dikinases. These enzymes transfer the β-phosphate of ATP to the C21 hydroxyl of the Rifamycin bridge. The result is modification of a critical RNA polymerase binding group that blocks productive complex formation. On the other hand, Rifamycin monooxygenases are FAD-dependent enzymes that hydroxylate the naphthoquinone core. The result of this modification is untethering of the chain from the naphthyl moiety, disrupting the essential 3D shape necessary for productive RNA polymerase binding and inhibition that leads to cell death.All of these enzymes have homologues in bacterial metabolism that either are their direct precursors or share common ancestors to the resistance enzyme. The diversity of these resistance mechanisms, often redundant in individual bacterial isolates, speaks to the importance of protecting RNA polymerase from these compounds and validates this enzyme as a critical antibiotic target. |
| 2021 | Activity of Rifamycin Derivatives against Nontuberculous Mycobacteria, including Macrolide-/Amikacin-Resistant Clinical Isolates. | Antimicrob Agents Chemother | We evaluated the activity of Rifamycin derivatives, including rifampin, rifapentine, rifaximin, and rifabutin, against clinical nontuberculous mycobacteria (NTM) isolates. Of the Rifamycin derivatives, rifabutin showed the lowest MICs against all NTM species, including complex, , and Rifabutin also had effective activity against macrolide- and aminoglycoside-resistant NTM isolates. Rifabutin could be worth considering as a therapeutic option for NTM disease, particularly drug-resistant disease. |
| 2021 | Decreased plasma rifapentine concentrations associated with AADAC single nucleotide polymorphism in adults with tuberculosis. | J Antimicrob Chemother | Rifapentine exposure is associated with bactericidal activity against Mycobacterium tuberculosis, but high interindividual variation in plasma concentrations is encountered.To investigate a genomic association with interindividual variation of rifapentine exposure, SNPs of six human genes involving Rifamycin metabolism (AADAC, CES2), drug transport (SLCO1B1, SLCO1B3) and gene regulation (HNF4A, PXR) were evaluated.We characterized these genes in 173 adult participants in treatment trials of the Tuberculosis Trials Consortium. Participants were stratified by self-identified race (black or non-black), and rifapentine AUC from 0 to 24 h (AUC0-24) was adjusted by analysis of covariance for SNPs, rifapentine dose, sex, food and HIV coinfection. This study was registered at ClinicalTrials.gov under identifier NCT01043575.The effect on rifapentine least squares mean AUC0-24 in black participants overall decreased by -10.2% for AADAC rs1803155 G versus A allele (Wald test: P = 0.03; false discovery rate, 0.10). Black participants with one G allele in AADAC rs1803155 were three times as likely to have below target bactericidal rifapentine exposure than black participants with the A allele (OR, 2.97; 95% CI: 1.16, 7.58). With two G alleles, the OR was greater. In non-black participants, AADAC rs1803155 SNP was not associated with rifapentine exposure. In both black and non-black participants, other evaluated genes were not associated with rifapentine exposure (P > 0.05; false discovery rate > 0.10).Rifapentine exposure in black participants varied with AADAC rs1803155 genotype and the G allele was more likely to be associated with below bactericidal target rifapentine exposure. Further pharmacogenomic study is needed to characterize the association of the AADAC rs1803155 with inadequate rifapentine exposure in different patient groups. |
| 2021 | Nevirapine pharmacokinetics in HIV-infected persons receiving rifapentine and isoniazid for TB prevention. | J Antimicrob Chemother | The use of Rifamycin antibiotics for TB prevention carries a risk of detrimental drug-drug interactions with concomitantly used ART.To evaluate the interaction of the antiretroviral drug nevirapine in combination with 4 weeks of daily rifapentine and isoniazid for TB prevention in people living with HIV.Participants were individuals enrolled in the BRIEF-TB study receiving nevirapine and randomized to the rifapentine/isoniazid arm of the study. Participants provided sparse pharmacokinetic (PK) sampling at baseline and weeks 2 and 4 for trough nevirapine determination. Nevirapine apparent oral clearance (CL/F) was estimated and the geometric mean ratio (GMR) of CL/F prior to and during rifapentine/isoniazid was calculated.Seventy-eight participants had evaluable PK data: 61 (78%) female, 51 (65%) black non-Hispanic and median (range) age of 40 (13-66) years. Median (IQR) nevirapine trough concentrations were: week 0, 7322 (5266-9302) ng/mL; week 2, 5537 (3552-8462) ng/mL; and week 4, 5388 (3516-8243) ng/mL. Sixty out of 78 participants (77%) had nevirapine concentrations ≥3000 ng/mL at both week 2 and 4. Median (IQR) nevirapine CL/F values were: week 0 pre-rifapentine/isoniazid, 2.03 (1.58-2.58) L/h; and during rifapentine/isoniazid, 2.62 (1.81-3.42) L/h. The GMR (90% CI) for nevirapine CL/F was 1.30 (1.26-1.33).The CL/F of nevirapine significantly increased with concomitant rifapentine/isoniazid. The decrease in nevirapine trough concentrations during rifapentine/isoniazid therapy suggests induction of nevirapine metabolism, consistent with known rifapentine effects. The magnitude of this drug-drug interaction suggests daily rifapentine/isoniazid for TB prevention should not be co-administered with nevirapine-containing ART. |
| 2020 | Hepatocytic transcriptional signatures predict comparative drug interaction potential of rifamycin antibiotics. | Sci Rep | Current strategies to treat tuberculosis (TB) and co-morbidities involve multidrug combination therapies. Rifamycin antibiotics are a key component of TB therapy and a common source of drug-drug interactions (DDIs) due to induction of drug metabolizing enzymes (DMEs). Management of Rifamycin DDIs are complex, particularly in patients with co-morbidities, and differences in DDI potential between Rifamycin antibiotics are not well established. DME profiles induced in response to tuberculosis antibiotics (rifampin, rifabutin and rifapentine) were compared in primary human hepatocytes. We identified Rifamycin induced DMEs, cytochrome P450 (CYP) 2C8/3A4/3A5, SULT2A, and UGT1A4/1A5 and predicted lower DDIs of rifapentine with 58 clinical drugs used to treat co-morbidities in TB patients. Transcriptional networks and upstream regulator analyses showed FOXA3, HNF4α, NR1I2, NR1I3, NR3C1 and RXRα as key transcriptional regulators of Rifamycin induced DMEs. Our study findings are an important resource to design effective medication regimens to treat common co-conditions in TB patients. |
| 2020 | High-dose rifapentine with or without moxifloxacin for shortening treatment of pulmonary tuberculosis: Study protocol for TBTC study 31/ACTG A5349 phase 3 clinical trial. | Contemp Clin Trials | Phase 2 clinical trials of tuberculosis treatment have shown that once-daily regimens in which rifampin is replaced by high dose rifapentine have potent antimicrobial activity that may be sufficient to shorten overall treatment duration. Herein we describe the design of an ongoing phase 3 clinical trial testing the hypothesis that once-daily regimens containing high dose rifapentine in combination with other anti-tuberculosis drugs administered for four months can achieve cure rates not worse than the conventional six-month treatment regimen.S31/A5349 is a multicenter randomized controlled phase 3 non-inferiority trial that compares two four-month regimens with the standard six-month regimen for treating drug-susceptible pulmonary tuberculosis in HIV-negative and HIV-positive patients. Both of the four-month regimens contain high-dose rifapentine instead of rifampin, with ethambutol replaced by moxifloxacin in one regimen. All drugs are administered seven days per week, and under direct observation at least five days per week. The primary outcome is tuberculosis disease-free survival at twelve months after study treatment assignment. A total of 2500 participants will be randomized; this gives 90% power to show non-inferiority with a 6.6% margin of non-inferiority.This phase 3 trial formally tests the hypothesis that augmentation of Rifamycin exposures can shorten tuberculosis treatment to four months. Trial design and standardized implementation optimize the likelihood of obtaining valid results. Results of this trial may have important implications for clinical management of tuberculosis at both individual and programmatic levels.NCT02410772. Registered 8 April 2015,https://www.clinicaltrials.gov/ct2/show/NCT02410772?term=02410772&rank=1. |
| 2019 | Shortening Buruli Ulcer Treatment with Combination Therapy Targeting the Respiratory Chain and Exploiting Mycobacterium ulcerans Gene Decay. | Antimicrob Agents Chemother | Buruli ulcer is treatable with antibiotics. An 8-week course of rifampin (RIF) and either streptomycin (STR) or clarithromycin (CLR) cures over 90% of patients. However, STR requires injections and may be toxic, and CLR shares an adverse drug-drug interaction with RIF and may be poorly tolerated. Studies in a mouse footpad infection model showed that increasing the dose of RIF or using the long-acting Rifamycin rifapentine (RPT), in combination with clofazimine (CFZ), a relatively well-tolerated antibiotic, can shorten treatment to 4 weeks. CFZ is reduced by a component of the electron transport chain (ETC) to produce reactive oxygen species toxic to bacteria. Synergistic activity of CFZ with other ETC-targeting drugs, the ATP synthase inhibitor bedaquiline (BDQ) and the : oxidase inhibitor Q203 (now named telacebec), was recently described against Recognizing that mutants lacking the alternative oxidase are hypersusceptible to Q203 and that is a natural oxidase-deficient mutant, we tested the susceptibility of to Q203 and evaluated the treatment-shortening potential of novel 3- and 4-drug regimens combining RPT, CFZ, Q203, and/or BDQ in a mouse footpad model. The MIC of Q203 was extremely low (0.000075 to 0.00015 μg/ml). Footpad swelling decreased more rapidly in mice treated with Q203-containing regimens than in mice treated with RIF and STR (RIF+STR) and RPT and CFZ (RPT+CFZ). Nearly all footpads were culture negative after only 2 weeks of treatment with regimens containing RPT, CFZ, and Q203. No relapse was detected after only 2 weeks of treatment in mice treated with any of the Q203-containing regimens. In contrast, 15% of mice receiving RIF+STR for 4 weeks relapsed. We conclude that it may be possible to cure patients with Buruli ulcer in 14 days or less using Q203-containing regimens rather than currently recommended 56-day regimens. |
| 2019 | A Population Pharmacokinetic Analysis Shows that Arylacetamide Deacetylase (AADAC) Gene Polymorphism and HIV Infection Affect the Exposure of Rifapentine. | Antimicrob Agents Chemother | Rifapentine is a Rifamycin used to treat tuberculosis. As is the case for rifampin, plasma exposures of rifapentine are associated with the treatment response. While concomitant food intake and HIV infection explain part of the pharmacokinetic variability associated with rifapentine, few studies have evaluated the contribution of genetic polymorphisms. We evaluated the effects of functionally significant polymorphisms of the genes encoding OATP1B1, the pregnane X receptor (PXR), constitutive androstane (CAR), and arylacetamide deacetylase (AADAC) on rifapentine exposure. Two studies evaluating novel regimens among southern African patients with drug-susceptible pulmonary tuberculosis were included in this analysis. In the RIFAQUIN study, rifapentine was administered in the continuation phase of antituberculosis treatment in 1,200-mg-once-weekly or 900-mg-twice-weekly doses. In the Daily RPE study, 450 or 600 mg was given daily during the intensive phase of treatment. Nonlinear mixed-effects modeling was used to describe the pharmacokinetics of rifapentine and to identify significant covariates. A total of 1,144 drug concentration measurements from 326 patients were included in the analysis. Pharmacogenetic information was available for 162 patients. A one-compartment model with first-order elimination and transit compartment absorption described the data well. In a typical patient (body weight, 56 kg; fat-free mass, 45 kg), the values of clearance and volume of distribution were 1.33 liters/h and 25 liters, respectively. Patients carrying the AA variant (65.4%) of rs1803155 were found to have a 10.4% lower clearance. HIV-infected patients had a 21.9% lower bioavailability. Once-weekly doses of 1,200 mg were associated with a reduced clearance (13.2%) compared to that achieved with more frequently administered doses. Bioavailability was 23.3% lower among patients participating in the Daily RPE study than in those participating in the RIFAQUIN study. This is the first study to report the effect of rs1803155AA on rifapentine clearance. The observed increase in exposure is modest and unlikely to be of clinical relevance. The difference in bioavailability between the two studies is probably related to the differences in food intake concomitant with the dose. HIV-coinfected patients had lower rifapentine exposures. |
| 2019 | High-Dose Rifamycins Enable Shorter Oral Treatment in a Murine Model of Mycobacterium ulcerans Disease. | Antimicrob Agents Chemother | Buruli ulcer (BU), caused by , is a neglected tropical skin and soft tissue infection that is associated with disability and social stigma. The mainstay of BU treatment is an 8-week course of rifampin (RIF) at 10 mg/kg of body weight and 150 mg/kg streptomycin (STR). Recently, the injectable STR has been shown to be replaceable with oral clarithromycin (CLR) for smaller lesions for the last 4 weeks of treatment. A shorter, all-oral, highly efficient regimen for BU is needed, as the long treatment duration and indirect costs currently burden patients and health systems. Increasing the dose of RIF or replacing it with the more potent Rifamycin drug rifapentine (RPT) could provide such a regimen. Here, we performed a dose-ranging experiment of RIF and RPT in combination with CLR over 4 weeks of treatment in a mouse model of disease. A clear dose-dependent effect of RIF on both clinical and microbiological outcomes was found, with no ceiling effect observed with tested doses up to 40 mg/kg. RPT-containing regimens were more effective on All RPT-containing regimens achieved culture negativity after only 4 weeks, while only the regimen with the highest RIF dose (40 mg/kg) did so. We conclude that there is dose-dependent efficacy of both RIF and RPT and that a ceiling effect is not reached with the current standard regimen used in the clinic. A regimen based on higher Rifamycin doses than are currently being evaluated against tuberculosis in clinical trials could shorten and improve therapy of Buruli ulcer. |
| 2019 | Evolution of Rifampin Resistance in Escherichia coli and Mycobacterium smegmatis Due to Substandard Drugs. | Antimicrob Agents Chemother | Poor-quality medicines undermine the treatment of infectious diseases, such as tuberculosis, which require months of treatment with rifampin and other drugs. Rifampin resistance is a critical concern for tuberculosis treatment. While subtherapeutic doses of medicine are known to select for antibiotic resistance, the effect of drug degradation products on the evolution of resistance is unknown. Here, we demonstrate that substandard drugs that contain degraded active pharmaceutical ingredients select for gene alterations that confer resistance to standard drugs. We generated drug-resistant and strains by serially culturing bacteria in the presence of the rifampin degradation product rifampin quinone. We conducted Sanger sequencing to identify mutations in rifampin-resistant populations. Strains resistant to rifampin quinone developed cross-resistance to the standard drug rifampin, with some populations showing no growth inhibition at maximum concentrations of rifampin. Sequencing of the rifampin quinone-treated strains indicated that they acquired mutations in the DNA-dependent RNA polymerase B subunit. These mutations were localized in the rifampin resistance-determining region (RRDR), consistent with other reports of rifampin-resistant and mycobacteria. Rifampin quinone-treated mycobacteria also had cross-resistance to other Rifamycin class drugs, including rifabutin and rifapentine. Our results strongly suggest that substandard drugs not only hinder individual patient outcomes but also restrict future treatment options by actively contributing to the development of resistance to standard medicines. |
| 2018 | Pharmacokinetics of rifapentine and rifampin in a rabbit model of tuberculosis and correlation with clinical trial data. | Sci Transl Med | In clinical trials of two Rifamycin antibiotics (rifampin and rifapentine) for treating tuberculosis (TB), patients with cavitary lung lesions did not appear to derive benefit from rifapentine. Rifapentine was found not to outperform rifampin, despite a lower minimum inhibitory concentration against in mouse models of TB. To understand these findings, we have developed a rabbit model of TB that reliably develops lung cavities with features similar to those of patients with pulmonary cavitary TB. After single or multiple doses of rifampin or rifapentine that produced human-equivalent plasma exposures, rabbits were sacrificed at different time points after dosing. We measured site-of-disease drug pharmacokinetics and tissue drug distribution. We used pharmacokinetic-pharmacodynamic (PK/PD) modeling to estimate drug penetration into different types of tubercular lesions. Both drugs penetrated rabbit lung cellular lesions, as well as the fibrotic cavity wall of cavitary lesions (penetration coefficients ≥1 compared to plasma). For the necrotic liquefied material inside cavitary lesions known as caseum (which contains high numbers of bacteria), the penetration coefficient was 1.0 for rifampin but only 0.25 for rifapentine. When estimates of site-of-disease drug PK were substituted into clinical PK/PD models, the relationship between site-of-action exposure and sputum culture conversion was significant ( < 10). We propose that poor penetration of rifapentine into lung cavitary lesions explains, in part, why rifapentine doses required to improve treatment outcomes in two phase 2 clinical trials were four times higher in TB patients with large cavities compared to TB patients without cavitary lung disease. |
| 2017 | Clinical and pharmacological hallmarks of rifapentine's use in diabetes patients with active and latent tuberculosis: do we know enough? | Drug Des Devel Ther | Rifapentine is a Rifamycin derivate approved by the US Food and Drug Administration in 1998 for the treatment of active, drug-susceptible tuberculosis (TB). In 2014, rifapentine was approved for the treatment of latent TB infection in patients at high risk of progression to active disease and is currently under evaluation by the European Medicines Agency. Expanding indications of rifapentine largely affect diabetes patients, since about one-third of them harbor latent TB. Clinical consequences of rifapentine use in this population and potentially harmful interactions with hypoglycemic agents are widely underexplored and generally considered similar to the ones of rifampicin. Indeed, rifapentine too may decrease blood levels of many oral antidiabetics and compete with them for protein-binding sites and/or transporters. However, the two drugs differ in protein-binding degree, the magnitude of cytochrome P450 induction and auto-induction, the degree of renal elimination, and so on. Rifapentine seems to be more suitable for use in diabetes patients with renal impairment, owing to the fact that it does not cause renal toxicity, and it is eliminated via kidneys in smaller proportions than rifampicin. On the other hand, there are no data related to rifapentine use in patients >65 years, and hypoalbuminemia associated with diabetic kidney disease may affect a free fraction of rifapentine to a greater extent than that of rifampicin. Until more pharmacokinetic information and information on the safety of rifapentine use in diabetic patients and drug-drug interactions are available, diabetes in TB patients treated with rifapentine should be managed with insulin analogs, and glucose and rifapentine plasma levels should be closely monitored. |
| 2017 | Immunodeficiency and Intermittent Dosing Promote Acquired Rifamycin Monoresistance in Murine Tuberculosis. | Antimicrob Agents Chemother | More-permissive preclinical models may be useful in evaluating antituberculosis regimens for their propensity to select drug-resistant mutants. To evaluate whether acquired Rifamycin monoresistance could be recapitulated in mice and, if so, to evaluate the effects of immunodeficiency, intermittent dosing, and drug exposures, athymic nude and BALB/c mice were infected. Controls received daily rifapentine alone or 2 months of rifampin, isoniazid, pyrazinamide, and ethambutol, followed by 4 months of rifampin/isoniazid, either daily or twice weekly with one of two isoniazid doses. Test groups received the same intensive regimen followed by once-weekly rifapentine or isoniazid/rifapentine with rifapentine doses of 10, 15, or 20 mg/kg of body weight plus one of two isoniazid doses. All combination regimens rendered BALB/c mouse cultures negative but selected mutants resistant to isoniazid (8.5%, 12/140) or rifampin (3.5%, 5/140) in nude mice ( < 0.001). Intermittently dosed intensive-phase therapy selected isoniazid and rifampin resistance in 10% (8/80, < 0.001) and 20% (16/80, = 0.009) of nude mice, respectively, compared to 0% treated with a daily regimen. Once-weekly rifapentine-containing continuation-phase regimens selected rifampin-resistant mutants at a rate of 18.0% (18/100, = 0.035 compared to rifampin/isoniazid regimens). Higher isoniazid doses in the intermittent-treatment control regimen and higher rifapentine doses in once-weekly regimens were associated with less selection of isoniazid resistance. Acquired resistance, including Rifamycin monoresistance, was more likely to occur in nude mice despite administration of combination therapy. These results recapitulate clinical outcomes and indicate that nude mice may be useful for evaluating the ability of novel regimens to prevent the selection of resistance. |
| 2017 | Rifampin vs. rifapentine: what is the preferred rifamycin for tuberculosis? | Expert Rev Clin Pharmacol | One-third of the world's population is infected with Mycobacterium tuberculosis (M.tb.). Latent tuberculosis infection (LTBI) can progress to tuberculosis disease, the leading cause of death by infection. Rifamycin antibiotics, like rifampin and rifapentine, have unique sterilizing activity against M.tb. What are the advantages of each for LTBI or tuberculosis treatment? Areas covered: We review studies assessing the pharmacokinetics (PK), pharmacodynamics (PD), drug interaction risk, safety, and efficacy of rifampin and rifapentine and provide basis for comparing them. Expert commentary: Rifampin has shorter half-life, higher MIC against M.tb, lower protein binding, and better distribution into cavitary contents than rifapentine. Drug interactions for the two drugs maybe similar in magnitude. For LTBI, rifapentine is effective as convenient, once-weekly, 12-week course of treatment. Rifampin is also effective for LTBI, but must be given daily for four months, therefore, drug interactions are more problematic. For drug-sensitive tuberculosis disease, rifampin remains the standard of care. Safety profile of rifampin is better-described; adverse events differ somewhat for the two drugs. The registered once-weekly rifapentine regimen is inadequate, but higher doses of either drugs may shorten the treatment duration required for effective management of TB. Results of clinical trials evaluating high-dose Rifamycin regimens are eagerly awaited. |
| The Possible Innovative Use of Bifidobacterium longum W11 in Association With Rifaximin: A New Horizon for Combined Approach? | J Clin Gastroenterol | The aim of the study was to unequivocally demonstrate the nontransmissibility of the genes mediating the resistance of the strain Bifidobacterium longum W11 (LMG P-21586) to rifaximin.Most antibiotic treatments can induce unfavorable side effects such as antibiotic-associated diarrhea, which is largely attributable to the disruption of the intestinal microbiota. The parallel intake of probiotic bacteria might reduce these events, even if with generally very poor results. In this regard, the use of antibiotic-resistant beneficial bacteria could represent a worthy strategy.Rifaximin was tested in parallel with rifampicin, rifapentine, and rifabutin, all Rifamycin derivates, using 5 different concentrations. Susceptibility tests were performed by the disc diffusion method of Kirby-Bauer, and inhibition zones were measured after incubation at 37°C. B. longum BL03 was used as comparison. The B. longum W11 genome was sequenced on Illumina MiSeq with a 250 PE reads module. After mapping the reads with the reference bacterial genome, the alignment data were processed using FreeBayes software.B. longum BL03 was inhibited by all antibiotics even at the lowest concentration. In contrast, the W11 strain was inhibited by rifampicin, rifabutin, and rifaximin only at the highest concentration (512 μg/mL). The genomic analysis showed a mutation into the chromosomal DNA. No transposable elements were found, and the genetic locus was not flanked by close mobile genetic elements.B. longum W11 could be used in combined therapy with rifaximin, thus opening new focused frontiers in the probiotic era while preserving the necessary safety of use for consumers. |
| 2016 | Physiologically Based Pharmacokinetic Model of Rifapentine and 25-Desacetyl Rifapentine Disposition in Humans. | Antimicrob Agents Chemother | Rifapentine (RPT) is a Rifamycin antimycobacterial and, as part of a combination therapy, is indicated for the treatment of pulmonary tuberculosis (TB) caused by Mycobacterium tuberculosis Although the results from a number of studies indicate that rifapentine has the potential to shorten treatment duration and enhance completion rates compared to other Rifamycin agents utilized in antituberculosis drug regimens (i.e., regimens 1 to 4), its optimal dose and exposure in humans are unknown. To help inform such an optimization, a physiologically based pharmacokinetic (PBPK) model was developed to predict time course, tissue-specific concentrations of RPT and its active metabolite, 25-desacetyl rifapentine (dRPT), in humans after specified administration schedules for RPT. Starting with the development and verification of a PBPK model for rats, the model was extrapolated and then tested using human pharmacokinetic data. Testing and verification of the models included comparisons of predictions to experimental data in several rat tissues and time course RPT and dRPT plasma concentrations in humans from several single- and repeated-dosing studies. Finally, the model was used to predict RPT concentrations in the lung during the intensive and continuation phases of a current recommended TB treatment regimen. Based on these results, it is anticipated that the PBPK model developed in this study will be useful in evaluating dosing regimens for RPT and for characterizing tissue-level doses that could be predictors of problems related to efficacy or safety. |
| 2016 | In Vitro Evaluation of Inhalable Verapamil-Rifapentine Particles for Tuberculosis Therapy. | Mol Pharm | Recent studies have demonstrated that efflux pumps of Mycobacterium tuberculosis (M. tb) provide a crucial mechanism in the development of drug resistant to antimycobacterial drugs. Drugs that inhibit these efflux pumps, such as verapamil, have shown the potential in enhancing the treatment success. We therefore hypothesized that the combined inhaled administration of verapamil and a first-line Rifamycin antibiotic will further improve the treatment efficacy. An inhalable dry powder consisting of amorphous verapamil and crystalline rifapentine with l-leucine as an excipient was produced by spray drying. The in vitro aerosol characteristic of the powder, its microbiological activity and stability were assessed. When the powder was dispersed by an Osmohaler, the total fine particle fraction (FPFtotal, wt % of particles in aerosol <5 μm) of verapamil and rifapentine was 77.4 ± 1.1% and 71.5 ± 2.0%, respectively. The combination drug formulation showed a minimum inhibitory concentration (MIC90) similar to that of rifapentine alone when tested against both M. tb H37Ra and M. tb H37Rv strains. Importantly, the combination resulted in increased killing of M. tb H37Ra within the infected macrophage cells compared to either verapamil or rifapentine alone. In assessing cellular toxicity, the combination exhibited an acceptable half maximal inhibitory concentration (IC50) values (62.5 μg/mL) on both human monocytic (THP-1) and lung alveolar basal epithelial (A549) cell lines. Finally, the powder was stable after 3 months storage in 0% relative humidity at 20 ± 3 °C. |
| 2015 | Novel dosing strategies increase exposures of the potent antituberculosis drug rifapentine but are poorly tolerated in healthy volunteers. | Antimicrob Agents Chemother | Rifapentine is a potent antituberculosis drug currently in phase III trials. Bioavailability decreases with increasing dose, yet high daily exposures are likely needed to improve efficacy and shorten the tuberculosis treatment duration. Further, the limits of tolerability are poorly defined. The phase I multicenter trial in healthy adults described here investigated two strategies to increase rifapentine exposures: dividing the dose or giving the drug with a high-fat meal. In arm 1, rifapentine was administered at 10 mg/kg of body weight twice daily and 20 mg/kg once daily, each for 14 days, separated by a 28-day washout; the dosing sequence was randomized. In arm 2, 15 mg/kg rifapentine once daily was given with a high-fat versus a low-fat breakfast. Sampling for pharmacokinetic analysis was performed on days 1 and 14. Population pharmacokinetic analyses were performed. This trial was stopped early for poor tolerability and because of safety concerns. Of 44 subjects, 20 discontinued prematurely; 11 of these discontinued for protocol-defined toxicity (a grade 3 or higher adverse event or grade 2 or higher Rifamycin hypersensitivity). Taking rifapentine with a high-fat meal increased the median steady-state area under the concentration-time curve from time zero to 24 h (AUC0-24ss) by 31% (relative standard error, 6%) compared to that obtained when the drug was taken with a low-fat breakfast. Dividing the dose increased exposures substantially (e.g., 38% with 1,500 mg/day). AUC0-24ss was uniformly higher in our study than in recent tuberculosis treatment trials, in which toxicity was rare. In conclusion, two strategies to increase rifapentine exposures, dividing the dose or giving it with a high-fat breakfast, successfully increased exposures, but toxicity was common in healthy adults. The limits of tolerability in patients with tuberculosis remain to be defined. (AIDS Clinical Trials Group study A5311 has been registered at ClinicalTrials.gov under registration no. NCT01574638.). |
| 2015 | Rifampicin and rifapentine significantly reduce concentrations of bedaquiline, a new anti-TB drug. | J Antimicrob Chemother | Bedaquiline is the first drug of a new class approved for the treatment of TB in decades. Bedaquiline is metabolized by cytochrome P450 (CYP) 3A4 to a less-active M2 metabolite. Its terminal half-life is extremely long (5-6 months), complicating evaluations of drug-drug interactions. Rifampicin and rifapentine, two anti-TB drugs now being optimized to shorten TB treatment duration, are potent inducers of CYP3A4. This analysis aimed to predict the effect of repeated doses of rifampicin or rifapentine on the steady-state pharmacokinetics of bedaquiline and its M2 metabolite from single-dose data using a model-based approach.Pharmacokinetic data for bedaquiline and M2 were obtained from a Phase I study involving 32 individuals each receiving two doses of bedaquiline, alone or together with multiple-dose rifampicin or rifapentine. Sampling was performed over 14 days following each bedaquiline dose. Pharmacokinetic analyses were performed using non-linear mixed-effects modelling. Models were used to simulate potential dose adjustments.Rifamycin co-administration increased bedaquiline clearance substantially: 4.78-fold [relative standard error (RSE) 9.10%] with rifampicin and 3.96-fold (RSE 5.00%) with rifapentine. Induction of M2 clearance was equally strong. Average steady-state concentrations of bedaquiline and M2 are predicted to decrease by 79% and 75% when given with rifampicin or rifapentine, respectively. Simulations indicated that increasing the bedaquiline dosage to mitigate the interaction would yield elevated M2 concentrations during the first treatment weeks.Rifamycin antibiotics reduce bedaquiline concentrations substantially. In line with current treatment guidelines for drug-susceptible TB, concomitant use is not recommended, even with dose adjustment. |
| 2015 | Determination of the rifamycin antibiotics rifabutin, rifampin, rifapentine and their major metabolites in human plasma via simultaneous extraction coupled with LC/MS/MS. | J Pharm Biomed Anal | A novel assay using high pressure liquid chromatography (HPLC) coupled to mass spectrometer (MS) detection was developed and validated for the Rifamycin anti-tuberculosis antibiotics rifampicin (RIF), rifabutin (RBT), rifapentine (RPT) and their active desacetyl metabolites (dRIF, dRBT and dRPT, respectively) in human plasma. The assay uses 50 μL of human plasma with a quick and simple protein-precipitation extraction to achieve a dynamic range of 75-30,000 ng/mL for RIF, RBT and RPT and 37.5-15,000 ng/mL for dRIF, dRBT and dRPT, respectively. The average %CV and %deviation were less than 20% at the lower limit of quantitation and less than 15% over the range of the curve. The method was fully validated according to FDA criteria for bioanalytical assays and has successfully been used to support three large international tuberculosis trials. |
| 2014 | The Case for Using Higher Doses of First Line Anti-Tuberculosis Drugs to Optimize Efficacy. | Curr Pharm Des | Apart from new anti-tuberculosis drug development, another approach for tuberculosis (TB) treatment optimization is to derive maximum benefit from current agents. However, the dosage of current anti-TB drug regimens has never been optimized according to the exposure-effect relationships of each drug. The objective of this article is to review the latest pharmacokinetic, pharmacodynamic, experimental, and clinical data concerning the use of higher doses of first-line anti-TB drugs to improve the efficacy of pulmonary tuberculosis treatment. Exposure-effect relationships have been described for all first-line anti-TB agents. There is convincing evidence that patients would benefit from higher Rifamycin exposure. This could be achieved by using higher daily doses of rifampin, or more frequent dosing of rifapentine. The dose-dependent activity of pyrazinamide observed in hollow-fiber and animal models suggests that higher doses of pyrazimamide might be more efficacious, but the tolerability of such higher doses needs to be investigated in humans. It is likely that higher doses of ethambutol would be associated with higher antibacterial effect, but the dose-related ocular toxicity of the drug precludes such practice. For isoniazid, dose individualization is required to optimize patient care. The use of higher than standard doses of isoniazid in fast acetylators should result in greater early bactericidal activity. To conclude, the use of higher doses for some of the firstline anti-TB agents has definite potential for shortening or improving TB treatment. |
| 2014 | Quantification of rifapentine, a potent antituberculosis drug, from dried blood spot samples using liquid chromatographic-tandem mass spectrometric analysis. | Antimicrob Agents Chemother | The quantification of antituberculosis drug concentrations in multinational trials currently requires the collection of modest blood volumes, centrifugation, aliquoting of plasma, freezing, and keeping samples frozen during shipping. We prospectively enrolled healthy individuals into the Tuberculosis Trials Consortium Study 29B, a phase I dose escalation study of rifapentine, a Rifamycin under evaluation in tuberculosis treatment trials. We developed a liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for quantifying rifapentine in whole blood on dried blood spots (DBS) to facilitate pharmacokinetic/pharmacodynamic analyses in clinical trials. Paired plasma and whole-blood samples were collected by venipuncture, and whole blood was spotted on Whatman protein saver 903 cards. The methods were optimized for plasma and then validated for DBS. The analytical measuring range for quantification of rifapentine and its metabolite was 50 to 80,000 ng/ml in whole-blood DBS. The analyte was stable on the cards for 11 weeks with a desiccant at room temperature and protected from light. The method concordance for paired plasma and whole-blood DBS samples was determined after correcting for participant hematocrit or population-based estimates of bias from Bland-Altman plots. The application of either correction factor resulted in acceptable correlation between plasma and whole-blood DBS (Passing-Bablok regression corrected for hematocrit; y = 0.98x + 356). Concentrations of rifapentine may be determined from whole-blood DBS collected via venipuncture after normalization in order to account for the dilutional effects of red blood cells. Additional studies are focused on the application of this methodology to capillary blood collected by finger stick. The simplicity of processing, storage, shipping, and low blood volume makes whole-blood DBS attractive for rifapentine pharmacokinetic evaluations, especially in international and pediatric trials. |
| 2014 | An update on the use of rifapentine for tuberculosis therapy. | Expert Opin Drug Deliv | Tuberculosis (TB) remains rampant throughout the world, in large part due to the lengthy treatment times of current therapeutic options. Rifapentine, a Rifamycin antibiotic, is currently approved for intermittent dosing in the treatment of TB. Recent animal studies have shown that more frequent administration of rifapentine could shorten treatment times, for both latent and active TB infection. However, these results were not replicated in a subsequent human clinical trial.This review analyses the evidence for more frequent administration of rifapentine and the reasons for the apparent lack of efficacy in shortening treatment times in human patients. Inhaled delivery is discussed as a potential option to achieve the therapeutic effect of rifapentine by overcoming the barriers associated with oral administration of this drug. Avenues for developing an inhalable form of rifapentine are also presented.Rifapentine is a promising active pharmaceutical ingredient with potential to accelerate treatment of TB if delivered by inhaled administration. Progression of current fundamental work on inhaled anti-tubercular therapies to human clinical trials is essential for determining their role in future treatment regimens. While the ultimate goal for global TB control is a vaccine, a short and effective treatment option is equally crucial. |
| 2013 | Bactericidal activity does not predict sterilizing activity: the case of rifapentine in the murine model of Mycobacterium ulcerans disease. | PLoS Negl Trop Dis | Since 2004, treatment of Mycobacterium ulcerans disease, or Buruli ulcer, has shifted from surgery to daily treatment with streptomycin (STR) + rifampin (RIF) for 8 weeks. For shortening treatment duration, we tested the potential of daily rifapentine (RPT), a long-acting Rifamycin derivative, as a substitute for RIF.BALB/c mice were infected with M. ulcerans in the right hind footpad and treated either daily (7/7) with STR+RIF or five days/week (5/7) with STR+RIF or STR+RPT for 4 weeks, beginning 28 days after infection when CFU counts were 4.88±0.51. The relative efficacy of the drug treatments was compared by footpad CFU counts during treatment and median time to footpad swelling after treatment cessation as measure of sterilizing activity. All drug treatments were bactericidal. After 1 week of treatment, the decline in CFU counts was significantly greater in treated mice but not different between the three treated groups. After 2 weeks of treatment, the decline in CFU was greater in mice treated with STR+RPT 5/7 than in mice treated with STR+RIF 7/7 and STR+RIF 5/7. After 3 and 4 weeks of treatment, CFU counts were nil in mice treated with STR+RPT and reduced by more than 3 and 4 logs in mice treated with STR+RIF 5/7 and STR+RIF 7/7, respectively. In sharp contrast to the bactericidal activity, the sterilizing activity was not different between all drug regimens although it was in proportion to the treatment duration.The better bactericidal activity of daily STR+RIF and especially of STR+RPT did not translate into better prevention of relapse, possibly because relapse-freecure after treatment of Buruli ulcer is more related to the reversal of mycolactone-induced local immunodeficiency by drug treatment rather than to the bactericidal potency of drugs. |
| 2012 | Streptomycin-starved Mycobacterium tuberculosis 18b, a drug discovery tool for latent tuberculosis. | Antimicrob Agents Chemother | Mycobacterium tuberculosis 18b, a streptomycin (STR)-dependent mutant that enters a viable but nonreplicating state in the absence of STR, has been developed as a simple model for drug testing against dormant bacilli. Here, we further evaluated the STR-starved 18b (SS18b) model both in vitro and in vivo by comparing the behavior of 22 approved and experimental tuberculosis drugs. Using the resazurin reduction microplate assay (REMA), rifampin (RIF), rifapentine (RPT), TMC207, clofazimine (CFM), and linezolid (LIN) were found to be active against SS18b in vitro, and their bactericidal activity was confirmed by determining the number of CFU. A latent 18b infection was established in mice, and some of the above-mentioned drugs were used for treatment, either alone or in combination with RIF. RIF, RPT, TMC207, CFM, and pyrazinamide (PZA) were all active in vivo, while cell wall inhibitors were not. A comparative kinetic study of Rifamycin efficacy was then undertaken, and the results indicated that RPT clears latent 18b infection in mice faster than RIF. Intrigued by the opposing responses of live and dormant 18b cells to cell wall inhibitors, we conducted a systematic analysis of 14 such inhibitors using REMA. This uncovered an SS18b signature (CWPRED) that accurately predicted the activities of cell wall inhibitors and performed well in a blind study. CWPRED will be useful for establishing the mode of action of compounds with unknown targets, while the SS18b system should facilitate the discovery of drugs for treating latent tuberculosis. |
| 2012 | New drugs for the treatment of tuberculosis: hope and reality. | Int J Tuberc Lung Dis | The objective of this review is to report evidence about the efficacy and potential of currently licensed drugs and new molecules beyond pre-clinical development for improving the chemotherapy of tuberculosis (TB). Rifapentine, a Rifamycin with low minimum inhibitory concentration, long half-life and potent sterilizing activity in mice did not confirm its potential in a recent short-term clinical trial and is being extensively re-evaluated. Moxifloxacin, a fluoroquinolone, improved the activity of the standard drug regimen when substituted for ethambutol (EMB). It is being studied to shorten the duration of treatment for fully drug-susceptible TB (Remox study). Clofazimine, a fat-soluble dye with experimental activity against TB, but used only for leprosy in the last 50 years, requires further study because it has been included in a successful short 9-month combined drug regimen for the treatment of multidrug-resistant TB. The diarylquinoline TMC207 is the most promising among the new TB drugs because of its experimental and clinical rate of culture conversion. Also exciting, 200 mg daily doses in humans of the nitroimidazo-oxazine PA-824 and the nitro-dihydro-imidazooxazole OPC-67683 were safe and induced a bactericidal effect of respectively 0.098 ± 0.072 log(10) and 0.040 ± 0.056 log(10) per day. The new oxazolidinones PNU-100480 and AZD-5847 might be at least as active as linezolid and much less toxic. SQ109 is an EMB analogue that does not have cross-resistance with EMB and might have synergistic activity in combined regimens. Benzothiazinones and dinitrobenzamides show exciting in vitro anti-microbial activity and deserve careful attention. |
| 2012 | Dose-ranging comparison of rifampin and rifapentine in two pathologically distinct murine models of tuberculosis. | Antimicrob Agents Chemother | In previous experiments, replacing the 10-mg/kg of body weight daily dose of rifampin with 7.5 to 10 mg/kg of rifapentine in combinations containing isoniazid and pyrazinamide reduced the duration of treatment needed to cure tuberculosis in BALB/c mice by approximately 50% due to rifapentine's more potent activity and greater drug exposures obtained. In the present study, we performed dose-ranging comparisons of the bactericidal and sterilizing activities of rifampin and rifapentine, alone and in combination with isoniazid and pyrazinamide with or without ethambutol, in BALB/c mice and in C3HeB/FeJ mice, which develop necrotic lung granulomas after infection with Mycobacterium tuberculosis. Each Rifamycin demonstrated a significant increase in sterilizing activity with increasing dose. Rifapentine was roughly 4 times more potent in both mouse strains. These results reinforce the rationale for ongoing clinical trials to ascertain the highest well-tolerated doses of rifampin and rifapentine. This study also provides an important benchmark for the efficacy of the first-line regimen in C3HeB/FeJ mice, a strain in which the lung lesions observed after M. tuberculosis infection may better represent the pathology of human tuberculosis. |
| 2011 | Activities of rifampin, Rifapentine and clarithromycin alone and in combination against mycobacterium ulcerans disease in mice. | PLoS Negl Trop Dis | treatment of Mycobacterium ulcerans disease, or Buruli ulcer (BU), has shifted from surgery to treatment with streptomycin(STR)+rifampin(RIF) since 2004 based on studies in a mouse model and clinical trials. We tested two entirely oral regimens for BU treatment, rifampin(RIF)+clarithromycin(CLR) and rifapentine(RPT)+clarithromycin(CLR) in the mouse model.BALB/c mice were infected in the right hind footpad with M. ulcerans strain 1059 and treated daily (5 days/week) for 4 weeks, beginning 11 days after infection. Treatment groups included an untreated control, STR+RIF as a positive control, and test regimens of RIF, RPT, STR and CLR given alone and the RIF+CLR and RPT+CLR combinations. The relative efficacy of the drug treatments was compared on the basis of footpad CFU counts and median time to footpad swelling. Except for CLR, which was bacteriostatic, treatment with all other drugs reduced CFU counts by approximately 2 or 3 log(10). Median time to footpad swelling after infection was 5.5, 16, 17, 23.5 and 36.5 weeks in mice receiving no treatment, CLR alone, RIF+CLR, RIF alone, and STR alone, respectively. At the end of follow-up, 39 weeks after infection, only 48%, 26.4% and 16.3% of mice treated with RPT+CLR, RPT alone and STR+RIF had developed swollen footpads. An in vitro checkerboard assay showed the interaction of CLR and RIF to be indifferent. However, in mice, co-administration with CLR resulted in a roughly 25% decrease in the maximal serum concentration (Cmax) and area under the serum concentration-time curve (AUC) of each Rifamycin. Delaying the administration of CLR by one hour restored Cmax and AUC values of RIF to levels obtained with RIF alone.these results suggest that an entirely oral daily regimen of RPT+CLR may be at least as effective as the currently recommended combination of injected STR+oral RIF. |
| 2011 | Treatment of tuberculosis and optimal dosing schedules. | Thorax | Intermittent tuberculosis treatment regimens have been developed to facilitate treatment supervision. Their efficacy has been substantiated by clinical trials and tuberculosis control programmes, notwithstanding the lack of head-to-head comparison between daily and intermittent regimens. Recently, there has been opposing evidence from observational studies, pharmacokinetic-pharmacodynamic studies and animal models that intermittent treatment increases the risk of relapse, treatment failure or acquired Rifamycin resistance, especially among HIV-infected patients. Systematic reviews have been conflicting. PubMed, Ovid MEDLINE and EMBASE were systematically searched for publications in English to evaluate the evidence about dosing schedules and treatment efficacy. Levels of evidence and grades of recommendation were assigned largely according to clinical evidence with reference to the Scottish Intercollegiate Guidelines Network guideline development handbook. A total of 32 articles were included after excluding 331 ineligible articles, 42 non-analytical studies, 22 narrative reviews or expert opinions and 44 articles embedded in systematic reviews. These included 9 systematic reviews, 8 controlled studies, 9 pharmacokinetic-pharmacodynamic studies, 5 mouse studies and 1 article about guinea pig experiments. Findings suggest high levels of evidence for using daily dosing schedules, especially during the initial phase in the presence of cavitation, isoniazid resistance and advanced HIV co-infection, to reduce the risk of treatment failure, recurrence and acquired drug resistance including acquired Rifamycin resistance. This review justifies the use of daily schedules in standard tuberculosis treatment regimens (particularly in the initial phase), corroborates prevailing understanding of pharmacokinetics-pharmacodynamics and mycobacterial persisters, and supports exploration of rifapentine-containing regimens in higher dosages and frequency. |
| 2010 | Rip Van Winkle wakes up: development of tuberculosis treatment in the 21st century. | Clin Infect Dis | The increase in drug-resistant tuberculosis and the global pandemic of human immunodeficiency virus infection-related tuberculosis threaten global tuberculosis control. There are needs for improved therapy in all aspects of tuberculosis treatment: treatment of latent infection, active drug-susceptible disease, and particularly, drug-resistant disease. Fortunately, at this time of great need, the field of tuberculosis drug development has reemerged after >30 years of inactivity. I review the specific needs for new treatment regimens, the pathways of tuberculosis drug development, and the agents that are currently in clinical development. There is renewed interest in the Rifamycin class; studies in the mouse model suggest that higher doses of rifampin or rifapentine may markedly improve the treatment of drug-susceptible disease. Fluoroquinolones may allow shorter treatment durations for drug-susceptible disease, though initial phase 2B trials have shown inconsistent activity. Novel drugs, such as TMC207, OPC-67683, PA824, SQ109, and PNU-100480, may improve the treatment of drug-resistant and drug-susceptible tuberculosis. |
| 2010 | The near future: improving the activity of rifamycins and pyrazinamide. | Tuberculosis (Edinb) | While we wait for improved new anti-tuberculosis drugs, the main aim for improving current treatment should be to optimize the use of the two current drugs, rifampicin and the pro-drug pyrazinamide, which are responsible to a similar extent for the entire sterilizing activity of current therapy. The Rifamycin activity could be improved by increasing the dose size of rifampicin or by daily dosing with long acting rifapentine. Increasing the dose size of pyrazinamide is limited by toxicity but an alternative approach is to use inhalation with pyrazinoic acid, as an adjunct to standard oral therapy. This would acidify pulmonary lesions, thus increasing the bactericidal activity of the orally administered pyrazinamide. Because pyrazinoic acid is the active moiety, it should also increase overall pyrazinamide activity and, because most resistance arises in the pncA gene that converts pyrazinamide to pyrazinoic acid, it should act on most pyrazinamide resistant strains. Inhalation technology allows delivery of drug to lesions rapidly and without first pass toxicity. The properties of drug containing microparticles and nanoparticles during inhalation and storage are reviewed. Spray-dried larger Trojan particles in which the smaller encapsulated particles can reside should be able to improve localisation within alveoli and avoid some storage problems. |
| 2010 | Experimental and clinical studies on Rifacinna--the new effective antituberculous drug (review). | Recent Pat Antiinfect Drug Discov | A new Rifamycin derivative 3-(4-cinnamyl-piperazinyl iminomethyl) Rifamycin SV (T9) and its sodium salt (T11, Rifacinna((R))) were in vitro, in vivo, toxicologically and clinically investigated in comparison with rifampicin, rifapentine, rifabutin, rifalazil. Our experiments showed that Rifacinna exhibits excellent in vitro activity against Gram(+), Gram (-) aerobic, anaerobic pathogens and mycobacteria. Rifacinna is active against Staphylococcus, Streptococcus spp. including MRSA, with MIC90- 0.06-0.5 mg/L; against Gram(+), Gram (-) anaerobes with MIC90 0.5 - 1 mg/L; against Mycobacterium tuberculosis (MTB) with MIC90 0.062 mg/L; against MDR resistant MTB (25%-30 %) and Mycobacterium avium complex (MAC) strains with MICs 0.6-1.0 mg/L. It shows high intraphagocytic activity against MAC strains (0.06 0.125mg/L). Single daily dose 10 mg/kg provides complete erradication of mycobacteria in experimental generalized tuberculosis. Pharmacological studies established: excellent pharmacokinetic profile following single oral dose 10mg/kg Tmax 5-6 h, C(max) 5-9 mg/L, T1/2 33-34 h; low toxicity; no teratogenic and embryotoxic effects. The clinical study of Rifacinna shows higher therapeutic efficacy than Rifampicin in patients with infiltrative, disseminated and cavitary form of pulmonary tuberculosis, good tolerability and safety profile. Some of the recent patents related to the treatment of tuberculosis are discussed in this review article. |
| 2009 | Short-course therapy with daily rifapentine in a murine model of latent tuberculosis infection. | Am J Respir Crit Care Med | Regimens recommended to treat latent tuberculosis infection (LTBI) are 3 to 9 months long. A 2-month rifampin+pyrazinamide regimen is no longer recommended. Shorter regimens are highly desirable. Because substituting rifapentine for rifampin in the standard regimen for active tuberculosis halves the treatment duration needed to prevent relapse in mice, we hypothesized daily rifapentine-based regimens could shorten LTBI treatment to 2 months or less.To improve an existing model of LTBI chemotherapy and evaluate the efficacy of daily rifapentine-based regimens.Mice were immunized with a more immunogenic recombinant Bacille Calmette-Guérin strain (rBCG30) and received very low-dose aerosol infection with Mycobacterium tuberculosis to establish a stable lung bacterial burden below 10(4) CFU without drug treatment. Mice received a control (isoniazid alone, rifampin alone, rifampin+isoniazid, rifampin+pyrazinamide) or test (rifapentine alone, rifapentine+isoniazid, rifapentine+pyrazinamide, rifapentine+isoniazid+pyrazinamide) regimen for 8 weeks. Rifamycin doses were 10 mg/kg/d, analogous to the same human doses. Outcomes were biweekly lung CFU counts and relapse after 4 to 8 weeks of treatment.M. tuberculosis CFU counts remained stable around 3.65 log(10) in immunized, untreated mice. Isoniazid or rifampin left all or most mice culture-positive at week 8. Rifampin+isoniazid cured 0 and 53% of mice and rifampin+pyrazinamide cured 47 and 100% of mice in 4 and 8 weeks, respectively. Rifapentine-based regimens were more active than rifampin+isoniazid and indistinguishable from rifampin+pyrazinamide.In this improved murine model of LTBI chemotherapy with very low lung burden, existing regimens were well represented. Daily rifapentine-based regimens were at least as active as rifampin+pyrazinamide, suggesting they could effectively treat LTBI in 6 to 8 weeks. |
| 2009 | Rifapentine vs. rifampicin for the treatment of pulmonary tuberculosis: a systematic review. | Int J Tuberc Lung Dis | To evaluate the efficacy and safety of rifapentine (RPT) vs. rifampicin (RMP) for the treatment of pulmonary tuberculosis (PTB).Systematic review of randomised controlled trials (RCTs) that compared combination drug regimens containing RPT with those containing RMP for the treatment of drug-susceptible or previously untreated PTB.Nine RCTs were identified. Statistically significant differences were not found in the cure rates, severe adverse effects, severe hepatotoxicity or bacteriological relapse rates between the regimens containing once- or twice-weekly RPT and those containing daily RMP for human immunodeficiency virus (HIV) negative patients, but were found in the bacteriological relapse rates between regimens containing once-weekly or less frequent RPT and those containing twice- or thrice-weekly RMP: the pooled relative risks in the two subgroups were respectively 1.71 (95%CI 1.13-2.58, P = 0.01) and 2.44 (95%CI 1.15-5.18, P = 0.02). The trial for HIV-positive patients did not show significant differences in the sputum conversion rate, severe adverse effects or bacteriological relapse rate between the RPT- and RMP-containing regimens; four of the five relapses were associated with the RPT-containing regimen, but none of the three relapses with the RMP-containing regimen produced monoresistance to Rifamycin (RIF).Once- or twice-weekly RPT and daily RMP have similar efficacy and safety for the treatment of HIV-negative PTB, but once-weekly or less frequent use of RPT, in comparison with twice- or thrice-weekly RMP, increases the risk of bacteriological relapse. RPT might increase the risk of resistance to RIF in HIV-positive patients. |
| 2008 | Repeated administration of high-dose intermittent rifapentine reduces rifapentine and moxifloxacin plasma concentrations. | Antimicrob Agents Chemother | Moxifloxacin- and rifapentine-based regimens are under investigation for the treatment of tuberculosis. However, rifapentine may induce enzymes that metabolize moxifloxacin, resulting in decreased moxifloxacin concentrations. In this phase I, two-period, sequential-design study, 13 subjects received 400 mg moxifloxacin daily for 4 days followed by daily moxifloxacin coadministered with 900 mg rifapentine thrice weekly. Pharmacokinetic analyses were performed after the 4th and 19th doses of moxifloxacin and after the 1st and 7th doses of rifapentine. For moxifloxacin, the mean area under the concentration-time curve from 0 to 24 h (AUC(0-24)) decreased by 17.2% (P = 0.0006) when the drug was coadministered with rifapentine, and the mean half-life (t(1/2)) decreased from 11.1 to 8.9 h (P = 0.0033). For rifapentine, the mean AUC(0-48) after seven thrice-weekly doses decreased by 20.3% (P = 0.0035) compared to the AUC(0-48) after the first dose, and the mean t(1/2) decreased from 18.5 to 14.8 h (P = 0.0004). The AUC(0-48) for the 25-desacetyl-rifapentine metabolite diminished 21%. Two days after completing the study drugs, one subject developed a fever and hepatitis, and another developed a flu-like illness with a rash. In conclusion, rifapentine modestly reduced moxifloxacin concentrations. Changes consistent with rifapentine autoinduction of metabolism were seen. Adverse reactions in two subjects may have represented Rifamycin hypersensitivity syndrome, although some features were atypical. |
| 2007 | Daily dosing of rifapentine cures tuberculosis in three months or less in the murine model. | PLoS Med | Availability of an ultra-short-course drug regimen capable of curing patients with tuberculosis in 2 to 3 mo would significantly improve global control efforts. Because immediate prospects for novel treatment-shortening drugs remain uncertain, we examined whether better use of existing drugs could shorten the duration of treatment. Rifapentine is a long-lived Rifamycin derivative currently recommended only in once-weekly continuation-phase regimens. Moxifloxacin is an 8-methoxyfluoroquinolone currently used in second-line regimens.Using a well-established mouse model with a high bacterial burden and human-equivalent drug dosing, we compared the efficacy of rifapentine- and moxifloxacin-containing regimens with that of the standard daily short-course regimen based on rifampin, isoniazid, and pyrazinamide. Bactericidal activity was assessed by lung colony-forming unit counts, and sterilizing activity was assessed by the proportion of mice with culture-positive relapse after 2, 3, 4, and 6 mo of treatment. Here, we demonstrate that replacing rifampin with rifapentine and isoniazid with moxifloxacin dramatically increased the activity of the standard daily regimen. After just 2 mo of treatment, mice receiving rifapentine- and moxifloxacin-containing regimens were found to have negative lung cultures, while those given the standard regimen still harbored 3.17 log10 colony-forming units in the lungs (p < 0.01). No relapse was observed after just 3 mo of treatment with daily and thrice-weekly administered rifapentine- and moxifloxacin-containing regimens, whereas the standard daily regimen required 6 mo to prevent relapse in all mice.Rifapentine should no longer be viewed solely as a Rifamycin for once-weekly administration. Our results suggest that treatment regimens based on daily and thrice-weekly administration of rifapentine and moxifloxacin may permit shortening the current 6 mo duration of treatment to 3 mo or less. Such regimens warrant urgent clinical investigation. |
| 2006 | Pharmacokinetics of rifapentine in children. | Pediatr Infect Dis J | Rifapentine is a Rifamycin antibiotic approved for the treatment of pulmonary infections caused by Mycobacterium tuberculosis. Although the pharmacokinetics of rifapentine has been investigated in adolescents and adults, no studies have assessed the pharmacokinetics of this drug in children or infants.Twenty-four children (7.1 +/- 3.3 years; mean +/- 1 SD, 27.9 +/- 11.9 kg) were enrolled in this open label study. Children received a single oral dose (10 to <30 kg body weight received 150 mg; 30 to <60 kg body weight received 300 mg), followed by repeated blood sampling (n = 11) for 32 hours. Rifapentine and 25-desacetyl rifapentine were quantitated by a validated high-pressure liquid chromatography method. Pharmacokinetic parameters were determined using a model-independent approach.A significant difference in dose-normalized area under the curves (AUC0-n and AUC0-infinity) was observed between children receiving the 150 and 300 mg doses, which was accounted for by differences in age between the dosing arms. In separate analyses, including data from adults, further age-dependence in total body exposure (reflected by AUC) and elimination was observed. Adverse events associated with rifapentine were mild and included gastric distress (n = 1) and vomiting (n = 2).Given a comparable weight-normalized dose, rifapentine exposure estimates are lower in children than those reported in adults, suggesting that a larger weight-normalized (ie, mg/kg) dose of rifapentine is needed in children. |
| 2005 | Cross-resistance of Escherichia coli RNA polymerases conferring rifampin resistance to different antibiotics. | J Bacteriol | In this study we further defined the rifampin-binding sites in Escherichia coli RNA polymerase (RNAP) and determined the relationship between rifampin-binding sites and the binding sites of other antibiotics, including two Rifamycin derivatives, rifabutin and rifapentine, and streptolydigin and sorangicin A, which are unrelated to rifampin, using a purified in vitro system. We found that there is almost a complete correlation between resistance to rifampin (Rif(r)) and reduced rifampin binding to 12 RNAPs purified from different rpoB Rif(r) mutants and a complete cross-resistance among the different Rifamycin derivatives. Most Rif(r) RNAPs were sensitive to streptolydigin, although some exhibited weak resistance to this antibiotic. However, 5 out of the 12 Rif(r) RNAPs were partially resistant to sorangicin A, and one was completely cross-resistant to sorangicin A, indicating that the binding site(s) for these two antibiotics overlaps. Both rifampin and sorangicin A inhibited the transition step between transcription initiation and elongation; however, longer abortive initiation products were produced in the presence of the latter, indicating that the binding site for sorangicin A is within the rifampin-binding site. Competition experiments of different antibiotics with (3)H-labeled rifampin for binding to wild-type RNAP further confirmed that the binding sites for rifampin, rifabutin, rifapentine, and sorangicin A are shared, whereas the binding sites for rifampin and streptolydigin are distinct. Because Rif(r) mutations are highly conserved in eubacteria, our results indicate that this set of Rif(r) mutant RNAPs can be used to screen for new antibiotics that will inhibit the growth of Rif(r) pathogenic bacteria. |
| 2005 | The early bactericidal activities of rifampin and rifapentine in pulmonary tuberculosis. | Am J Respir Crit Care Med | Comparison of the early bactericidal activity (EBA) of rifapentine and its pharmacokinetics with those of rifampin to determine the cause of poor clinical response and regrowth between doses, leading to Rifamycin monoresistance at relapse.Determination of the dose size of rifapentine that gives sufficient drug exposure to prevent regrowth.EBA study over initial 5 days of treatment of 123 patients, half at Durban and half at Cape Town, who received single rifapentine doses of 300, 600, 900, or 1,200 mg rifapentine or five daily doses of 150, 300, or 600 mg rifampin, with a pharmacokinetic study on 58 patients measuring standard parameters for each dose size of Rifamycin and their desacetyl metabolites.The EBAs for both Rifamycins were similar, with a linear relationship to log dose at lower doses and a curvilinear response at higher doses giving a plateau at 1,136 mg rifapentine. The area under the concentration-time curve (AUC) divided by the minimal inhibitory concentration (MIC) agreed well for both Rifamycins on the assumption that the only free 2% of free rifapentine and the 14% of free rifampin after plasma binding were active in the lesions.Only the free proportions of the Rifamycins were active in lesions. From consideration of the pulse size and the duration of the postantibiotic lag, a 1,200-mg dose of rifapentine seemed necessary to improve response and to prevent regrowth between doses, and hence Rifamycin monoresistance. |
| 2004 | In vitro and in vivo activities of new rifamycin derivatives against mycobacterial infections. | Curr Pharm Des | Several Rifamycin derivatives have been developed during the last 15 years for the treatment of mycobacterial infections. For tuberculosis, rifabutin (RFB) showed strong activity and seemed to be suitable when tuberculosis patients were also treated for their AIDS infection. Rifapentine (RPT) was evaluated in patients with or without AIDS for its intermittent use. It displayed promising activity but must be strengthened in situations, such as AIDS or patients without AIDS but with cavities. Rifalazil (RLZ) has been evaluated in mice but the dosages used were much higher than those tolerated by patients. Regarding Mycobacterium avium infections, RFB showed significant prophylactic activity in humans, RPT displayed some activity in mice and RLZ showed modest activity in mice. |
| 2003 | Low isoniazid concentrations and outcome of tuberculosis treatment with once-weekly isoniazid and rifapentine. | Am J Respir Crit Care Med | To understand why once-weekly isoniazid/rifapentine therapy for tuberculosis was less effective than twice-weekly isoniazid/rifampin, we studied human immunodeficiency virus-seronegative patients with either failure (n = 4), relapse (n = 35), or cure (n = 94), recruited from a comparative treatment trial. In multivariate analyses that were adjusted for severity of disease, low plasma concentrations of isoniazid were associated with failure/relapse with once-weekly isoniazid/rifapentine (median isoniazid area under the concentration-time curve for 12 hours after the dose [AUC(0-12)] was 36 microg x hour/ml in failure/relapse versus 56 microg x hour/ml in control cases p = 0.005), but not with twice-weekly isoniazid/rifampin. Furthermore, two patients who relapsed with Mycobacterium tuberculosis monoresistant to Rifamycin had very low concentrations of isoniazid. Finally, isoniazid acetylator status determined by N-acetyltransferase type 2 genotype was associated with outcome with once-weekly isoniazid/rifapentine (p = 0.03) but not twice-weekly isoniazid/rifampin. No Rifamycin pharmacokinetic parameter was consistently and significantly associated with outcome (p > 0.10). Because low isoniazid concentrations were associated with failure/relapse, a drug with consistently greater area under the concentration-time curve than isoniazid may be needed to achieve highly active once-weekly therapy with rifapentine. |
| 2002 | [Prospects for development of new antituberculous drugs]. | Kekkaku | Tuberculosis (TB) is a growing international health concern, since it is the leading infectious cause of death in the world today. Moreover, the resurgence of TB in industrialized countries and the worldwide increase in the prevalence of Mycobacterium avium complex (MAC) infections in immunocompromised hosts have prompted the quest for new antimycobacterial drugs. In particular, the appearance of multidrug-resistant (MDR) strains of M. tuberculosis, which exhibit in vitro resistance to at least two major antituberculous drug (usually INH and RFP) and cause intractable TB, has greatly contributed to the increased incidence of TB. Because of the global health problems of TB, the increasing rate of MDR-TB and the high rate of a co-infection with HIV, the development of potent new antituberculous drugs without cross-resistance with known antimycobacterial agents is urgently needed. In this article, I reviewed the following areas. First, I briefly reviewed some new findings (mainly reported after 2000) on the pharmacological status of Rifamycin derivatives (rifabutin, rifapentine, and rifalazil), fluoroquinolones (ciprofloxacin, ofloxacin, sparfloxacin, levofloxacin, gatifloxacin, sitafloxacin, moxifloxacin, and others), and new macrolides (clarithromycin, azithromycin, and roxithromycin). Second, I described other types of agents which are being developed as antimycobacterial drugs. Some of the agents discussed are already under preliminary clinical investigation, and others appear to be promising candidates for future development. In this review, the status of the development of new antimycobacterial, especially antituberculous agents including oxazolidinone (PNU-100480), 5'-nitroimidazole (CGI 17341), 2-pyridone (ABT-255), new riminophenazines, nitroimidazopyran (PA-824), new ketolides (ABT-773, telithromycin) and defensins (human neutrophil peptide-I), was examined. Third, the development of new antitubercular drugs was discussed according to the potential pharmacological target. New critical information on the whole genome of M. tuberculosis recently elucidated and increasing knowledge on various mycobacterial virulence genes will promote the progression in the identification of genes that code for new drug targets. Using such findings on mycobacterial genomes, drug development using quantitative structure-activity relationship may be possible in the near future. In this review, I described the screening of drugs that have an inhibitory activity against dTDP-rhamnose synthesis of M. tuberculosis, as a new drug target of the organism. In addition, I discussed the usefulness of antisense oligo DNAs specific to mycobacterial genes encoding certain metabolic enzymes or virulence factors that play roles in the bacterial escape from antimicrobial mechanisms of host macrophages. Fourth, I reviewed the drug vehicles which enable efficacious drug delivery to their target in vivo. The usefulness of poly (DL-lactide-co-glycolide) microsphere technology, which enables the encapsulated drugs to deliver the requested doses of them for prolonged time periods by a single shot without causing any toxicity and, moreover, enables the highly targeted delivery of the drugs to host macrophages, was discussed. Fifth, I described adjunctive immunotherapy for the management of patients with mycobacterial infections by giving certain immunomodulators in combination with antimycobacterial drugs. Adjuvant clinical trials using IL-2 or GM-CSF have been found to be efficacious to some extent in improving patients with tuberculosis or disseminated MAC infections. However, it seems that these immunopotentiating cytokines as well as IFN-gamma and IL-12 are not so promising for the therapeutic agents of mycobacterial infections because of the possible induction of immunosuppressive cytokines during adjuvant therapy and, in some cases, severe side-effect. Thus, the development of new classes of immuno-modulators other than cytokines, particularly those with no severe side-effect, is needed. This review dealt with ATP and its analogues which potentiate macrophage antimycobacterial activity via a purinergic P2X7 receptor. Finally, I described the roles of type II alveolar epithelial cells in the establishment of mycobacterial infections in the host lungs and the profiles of drug susceptibilities of M. tuberculosis and MAC organisms replicating within the type II pneumocytes. These findings are useful to precisely assess or predict the in vivo therapeutic activity of a given antimycobacterial drug from its in vitro activity. In this article, I have thoroughly reviewed the status of the development of new antimycobacterial drugs. There are a number of difficulties in the drug-design for the development of new drug formulations with increased potential for antimycobacterial effects, excellent pharmacokinetics, and tolerability. It should be emphasized that the most urgent goal of chemotherapy of tuberculosis and MAC infections, especially that associated with HIV infection, is to develop highly active, low-cost drugs which can be used not only in industrialized countries but also in developing countries, since the incidences of AIDS-associated intractable tuberculosis is rapidly increasing in the latter. |
| 2002 | Acquired rifamycin resistance in persons with advanced HIV disease being treated for active tuberculosis with intermittent rifamycin-based regimens. | MMWR Morb Mortal Wkly Rep | Rifamycin drugs (i.e., rifampin, rifabutin, and rifapentine) are essential for short-course chemotherapy in persons with active tuberculosis (TB). However, adverse drug-drug interactions complicate the concurrent use of Rifamycins and protease inhibitor drugs in persons with active TB who also are infected with human immunodeficiency virus (HIV-TB). CDC has recommended use of rifabutin in place of rifampin in multidrug regimens for the treatment of active TB in HIV-TB because rifabutin can be administered with antiretroviral treatment regimens that include protease inhibitors (1,2). These recommendations included twice-weekly intermittent therapy. Because intermittent rifabutin-based regimens had not been evaluated in clinical trials of HIV-TB, CDC's TB Trials Consortium (TBTC) initiated TBTC Study 23, a single-arm trial of twice-weekly rifabutin-based therapy for treatment of HIV-TB. |
| 2000 | Prospects for development of new antimycobacterial drugs. | J Infect Chemother | In this article, I have thoroughly reviewed the status of development of new antimycobacterial drugs, particularly fluoroquinolones (ciprofloxacin, ofloxacin, sparfloxacin, levofloxacin, gatifloxacin, sitafloxacin, and moxifloxacin), new macrolides (clarithromycin, azithromycin, and roxithromycin), Rifamycin derivatives (rifabutin, rifapentine, and KRM-1648), and others. The main purpose of this review was to describe the in-vitro and in-vivo activities of these drugs against Mycobacterium tuberculosis and Mycobacterium avium complex. In addition, the therapeutic efficacy of these drugs in the clinical treatment of mycobacterial infections has also been briefly mentioned. |
| 2001 | Newer drugs in leprosy. | Int J Lepr Other Mycobact Dis | During the last 15 years, new drugs active against Mycobacterium leprae have been identified. All of them belong to the fluoroquinolone, cycline and macrolide drug families. In the mouse model and in humans, minocycline, ofloxacin, and clarithromycin have demonstrated, individually or in combination, antileprosy activities much superior to those of the standard drugs dapsone and clofazimine. In humans, a single dose of the combination ofloxacin 400 mg + minocycline 100 mg was able to kill 68% to 98% of viable M. leprae and a single dose of ROM, a three-drug combination of rifampin 600 mg + ofloxacin 400 mg + minocycline 100 mg, was killing more than 99% of viable M. leprae. As a result of a double-blind, control, clinical trial, the Seventh Report of the WHO Expert Committee on Leprosy recommended in 1997 the use of single-dose ROM for the treatment of patients with single-lesion paucibacillary leprosy. Recently moxifloxacin, a new fluoroquinolone, and rifapentine, a long-lasting Rifamycin derivative, have demonstrated in the mouse model highly promising antileprosy activities, justifying their assessment in humans. |
| 2001 | Comparative pharmacokinetics and pharmacodynamics of the rifamycin antibacterials. | Clin Pharmacokinet | The Rifamycin antibacterials, rifampicin (rifampin), rifabutin and rifapentine, are uniquely potent in the treatment of patients with tuberculosis and chronic staphylococcal infections. Absorption is variably affected by food; the maximal concentration of rifampicin is decreased by food, whereas rifapentine absorption is increased in the presence of food. The Rifamycins are well-known inducers of enzyme systems involved in the metabolism of many drugs, most notably those metabolised by cytochrome P450 (CYP) 3A. The relative potency of the Rifamycins as CYP3A inducers is rifampin > rifapentine > rifabutin; rifabutin is also a CYP3A substrate. The antituberculosis activity of rifampicin is decreased by a modest dose reduction from 600 to 450mg. This somewhat surprising finding may be due to the binding of rifampicin to serum proteins, limiting free, active concentrations of the drug. However, increasing the administration interval (after the first 2 to 8 weeks of therapy) has little effect on the sterilising activity of rifampicin, suggesting that relatively brief exposures to a critical concentration of rifampicin are sufficient to kill intermittently metabolising mycobacterial populations. The high protein binding of rifapentine (97%) may explain the suboptimal efficacy of the currently recommended dose of this drug. The toxicity of rifampicin is related to dose and administration interval, with increasing rates of presumed hypersensitivity with higher doses combined with administration frequency of once weekly or less. Rifabutin toxicity is related to dose and concomitant use of CYP3A inhibitors. The Rifamycins illustrate the complexity of predicting the pharmacodynamics of treatment of an intracellular pathogen with the capacity for dormancy. |
| 1999 | Recent Developments in Epidemiology, Treatment, and Diagnosis of Tuberculosis. | Curr Infect Dis Rep | The resurgence in cases of active tuberculosis in North America in the past decade has prompted increases in funding for tuberculosis treatment, research, and education. As a result, the number of new cases of tuberculosis has declined and cases occur in smaller pockets of well-characterized populations, such as communities of foreign-born persons and socioeconomically disadvantaged groups. New strategies for the treatment of both active and latent tuberculosis may soon include the newly licensed, long-acting Rifamycin, rifapentine, but further studies are needed to determine optimal dosing regimens for this agent. Experts in tuberculosis and HIV infection have made headway in defining the optimal therapy for each current therapeutic option, and recently published guidelines are a useful document for clinicians. Rifabutin-based regimens are one approach toward achieving the optimal treatment of both diseases simultaneously. Finally, newly licensed molecular diagnostic tests for direct use on clinical specimens are intriguing, but their clinical utility remains to be defined. |
| 2000 | Prospects for development of new antimycobacterial drugs, with special reference to a new benzoxazinorifamycin, KRM-1648. | Arch Immunol Ther Exp (Warsz) | In this article, I have thoroughly reviewed the status of development of new antimycobacterial drugs, in particular, Rifamycin derivatives (rifabutin, rifapentine, and a new benzoxazinoRifamycin, KRM-1648), fluoroquinolones (ciprofloxacin, ofloxacin, sparfloxacin, levofloxacin, gatifloxacin, sitafloxacin, moxifloxacin, and others), new macrolides (clarithromycin, azithromycin, roxithromycin), and others. In this review, I have mainly described the in vitro and in vivo activities of these drugs against Mycobacterium tuberculosis and atypical mycobacteria, especially Mycobacterium avium complex. In addition, therapeutic efficacy of these drugs in cases of clinical treatment of mycobacterial infections have also been briefly mentioned. |
| 1999 | Analysis of rifapentine for preventive therapy in the Cornell mouse model of latent tuberculosis. | Antimicrob Agents Chemother | Rifapentine is a long-acting Rifamycin which may be useful for intermittent drug therapy against tuberculosis. In this study we measured the efficacies of rifapentine-containing intermittent drug regimens for preventive therapy using the Cornell mouse model of latent tuberculosis. We infected groups of mice intravenously with Mycobacterium tuberculosis and then treated them with isoniazid and pyrazinamide for 12 weeks according to the Cornell latency development protocol. After a 4-week interval of no treatment, experimental preventive therapy was administered by esophageal gavage for 12 or 18 weeks. After equilibration and dexamethasone amplification treatment, mouse organs were analyzed by quantitative colony counts to measure the effectiveness of therapy. Our results showed that once-weekly isoniazid plus rifapentine combination therapy for 18 weeks was an effective preventive regimen with sterilizing potency and bacillary load reduction comparable to those of daily isoniazid therapy for 18 weeks. Monotherapy with rifapentine weekly or fortnightly or with rifampin twice weekly for up to 18 weeks did not offer advantages in reducing bacillary load or in sterilizing organs compared to the effects of a placebo. These results with the Cornell mouse model indicate that once-weekly, short-course preventive therapy with isoniazid plus rifapentine is effective and may warrant investigation in humans with latent tuberculosis infection. |
| 1999 | Acquired rifamycin monoresistance in patients with HIV-related tuberculosis treated with once-weekly rifapentine and isoniazid. Tuberculosis Trials Consortium. | Lancet | Rifapentine is a cyclopentyl-substituted Rifamycin whose serum half-life is five times that of rifampin. The US Public Health Service Study 22 compared a once-weekly regimen of isoniazid and rifapentine with twice weekly isoniazid and rifampin in the continuation phase (the last 4 months) of treatment for pulmonary tuberculosis in HIV-seropositive and HIV-seronegative patients. This report concerns only the HIV-seropositive part of the trial, which has ended. The HIV-seronegative part will stop follow-up in 2001.Adults with culture-positive, drug-susceptible pulmonary tuberculosis who completed 2 months of four-drug (isoniazid, rifampin, pyrazinamide, ethambutol) treatment (induction phase) were randomly assigned 900 mg isoniazid and 600 mg rifapentine once weekly, or 900 mg isoniazid and 600 mg rifampin twice weekly. All therapy was directly observed. Statistical analysis used univariate, Kaplan-Meier, and logistic and proportional hazards regression methods.71 HIV-seropositive patients were enrolled: 61 completed therapy and were assessed for relapse. Five of 30 patients in the once-weekly isoniazid/rifapentine group relapsed, compared with three of 31 patients in the twice-weekly isoniazid/rifampin group (log rank chi2=0.69, p=0.41). However, four of five relapses in the once-weekly isoniazid/rifapentine group had monoresistance to Rifamycin, compared with none of three in the rifampin group (p=0.05). Patients who relapsed with Rifamycin monoresistance were younger (median age 29 vs 41 years), had lower baseline CD4 cell counts (median 16 vs 144 microL), and were more likely to have extrapulmonary involvement (75% vs 18%, p=0.03) and concomitant therapy with antifungal agents (75% vs 9%, p=0.006). No Rifamycin monoresistant relapse has occurred among 1004 HIV-seronegative patients enrolled to date.Relapse with Rifamycin monoresistant tuberculosis occurred among HIV-seropositive tuberculosis patients treated with a once-weekly isoniazid/rifapentine continuation-phase regimen. Until more effective regimens have been identified and assessed in clinical trials, HIV-seropositive people with tuberculosis should not be treated with a once-weekly isoniazid/rifapentine regimen. |
| 1999 | [Current status and perspectives on the development of rifamycin derivative antibiotics]. | Kekkaku | Rifampicin (RFP) was developed as one of the anti-tuberculosis drugs in 1966 and has been used for almost 30 years. Establishment of combination therapy using RFP has been contributing to the treatment/eradication of tuberculosis. A number of Rifamycin derivatives, as post RFPs, have been synthesized/developed over the the years. Chemical modification of Rifamycins has largely been concentrated on the moiety of naphthalene ring because modification of the ansa chain moiety reduces the activity. In 1992, rifabutin was approved as a preventive drug for MAC infection in AIDS patients in the United States and in European countries. It is noteworthy that rifapentine (RPT) was approved as an anti-tuberculosis drug in 1998 by FDA in the United States. A newly synthesized Rifamycin derivative (KRM-1648, rifalazil) possesses a potent activity against both M. Tuberculosis and MAC, and it is now under clinical trial for the treatment of Tuberculosis in the United States. KRM-1648 is metabolized to 30-hydroxy KRM and 25-deacetyl KRM in the body, and its 30-hydroxylation is caused by liver cytochrome P450 3A. It is well known that RFP, RFB and RPT induce liver cytochrome P450 in animals and human, and these accelerate the metabolism of concomitant drugs such as HIV protease inhibitors resulting in lowering their blood levels. While KRM-1648 did not induce liver P450 in animals, but it is not examined yet in human. Clinical study of DOT with intermittent therapy of RPT in combination with INH resulted in the preferable therapeutic effect comparable to the RFP therapy. Since KRM-1648 has a potent activity, a high tissue distribution and a long half-life, it may be also suitable for intermittent therapy. For the future novel anti-tuberculosis drugs and therapy for tuberculosis, it is prerequisite to develop new drugs with a preferable antimicrobial activity, to shorten further the treatment period, and to be effective against multi-drug resistant bacilli. It is expected that more effective novel Rifamycin derivatives can be developed with the above view points. |
| 1998 | Rifapentine. | Drugs | Rifapentine is a Rifamycin antibiotic with antimycobacterial activity. Rifapentine is generally more active against Mycobacterium tuberculosis than rifampicin (rifampin), although strains resistant to rifampicin are usually cross-resistant to rifapentine. Sputum culture conversion rates were slightly higher after 6 months of rifapentine- versus rifampicin-based therapy in patients with pulmonary tuberculosis in a Western study; however, relapse rates were higher in rifapentine recipients during follow-up. The excess relapses in the rifapentine group appeared to be related to poor compliance with nonRifamycin antituberculosis drugs during the intensive phase (first 2 months) of therapy. Rifapentine- and rifampicin-containing regimens produced similar sputum culture conversion rates with low rates of relapse in 2 randomised clinical trials in patients with smear-positive tuberculosis in China. In one trial, there was no difference in sputum culture conversion rates in patients treated with rifapentine once weekly or rifampicin twice weekly in combination with isoniazid and ethambutol during the continuation phase of treatment. Hyperuricaemia, which was reported only during the intensive phase, elevated ALT and AST levels and neutropenia were the most common treatment-related adverse events reported in patients receiving rifapentine- or rifampicin-containing regimens for tuberculosis in 1 Western study. |
| 1998 | Evaluation of once-weekly therapy for tuberculosis using isoniazid plus rifamycins in the mouse aerosol infection model. | Antimicrob Agents Chemother | Once-weekly therapy with combinations of isoniazid plus a Rifamycin was tested in the mouse low-dose aerosol infection model against two strains of Mycobacterium tuberculosis. Combinations of isoniazid and rifalizil and isoniazid and rifapentine were both highly effective. These animal model data thus support the evaluation of these regimens under clinical conditions. |
| 1997 | Primary human hepatocytes as a tool for the evaluation of structure-activity relationship in cytochrome P450 induction potential of xenobiotics: evaluation of rifampin, rifapentine and rifabutin. | Chem Biol Interact | In our laboratory, primary human hepatocytes are being investigated as an in vitro experimental system for the evaluation of pharmacokinetic drug-drug interactions. Our study here represents the first reported study that directly compares the cytochrome P450 isozyme 3A (CYP3A) induction potential of three antimicrobials derived from Rifamycin B, namely, rifampin, rifapentine and rifabutin. Two endpoints of CYP3A activity, testosterone 6 beta-hydroxylation and midazolam 1-hydroxylation have been used. Results obtained with hepatocytes from four different human donors show consistently that rifampin and rifapentine are potent inducers of CYP3A, while a significantly lower induction potential is observed for rifabutin. The relative induction potency of the three antimicrobials (rifampin > rifapentine >> rifabutin) is consistent with the available human in vivo data. For CYP1A measured as ethoxyresorufin O-deethylase activity, CYP2C8/9 measured as tolbutamide 4-hydroxylation activity, CYP2D6 measured as dextromethorphan O-demethylation, and AZT glucuronidation, there is either no effect or, where induction is found to be statistically significant in these other endpoints, the maximum induction values are consistently < 100% of the control. Our results suggest that CYP3A is the major CYP induced by these Rifamycin B derivatives. These studies illustrate the application of human hepatocytes in the evaluation of the structure-activity relationships in CYP induction for this class of chemicals and as an in vitro screen for drug-drug interaction potential via CYP induction. |
| 1996 | Rifapentine is active in vitro and in vivo against Toxoplasma gondii. | Antimicrob Agents Chemother | Rifapentine, a derivative of Rifamycin, was examined for its in vitro and in vivo activities against the protozoan parasite Toxoplasma gondii. The drug inhibited the intracellular replication of parasites and was not cytotoxic for the host cells at inhibitory concentrations. Mice infected either intraperitoneally with tachyzoites of the RH strain or orally with tissue cysts of the C56 strain were protected against death by treatment with rifapentine. The degree of protection was similar to that induced by atovaquone and apparently higher than that induced by rifabutin. Rifapentine may be a useful drug for the treatment of toxoplasmosis in immunocompromised individuals. |
| 1995 | New drugs for tuberculosis. | Eur Respir J Suppl | Since the late 1960s, tuberculosis has been successfully cured with antibiotics. With the introduction of rifampin, "short course" regimens using isoniazid and rifampin together with either streptomycin, ethambutol or pyrazinamide, for 6-9 months, have been successfully adopted. The spread of drug resistant M. tuberculosis strains in large urban areas has made this armamentarium of drugs insufficient, calling for the development of new drugs. Among Rifamycin derivatives, rifabutin is more active than rifampin in vitro and in experimental animals, and allows sputum conversion rats of 95-100%. It is effective in treating multidrug-resistant tuberculosis. Rifapentine is more active than rifampin in vitro and has a longer half-life, but it is not active against rifampin-resistant strains. Fluoroquinolones concentrate within macrophages, are effective against M. tuberculosis and act synergistically with rifampin and isoniazid. Ofloxacin, ciprofloxacin, sparfloxacin and lomefloxacin have been evaluated as antimycobacterial agents, and no cross-resistance with major antituberculous drugs has been found. Several other drugs, including new inhibitors of beta-lactamase and new beta-lactamase-resistant antibiotics, the aminoglycoside antibiotic, paromomycin, and the new nitroimidazole, 2-ethyl-5-intro-2.3-dihydro imidazo-oxazole, have been found to be active in vitro against M. tuberculosis. |
| 1991 | In vivo activities of newer rifamycin analogs against Mycobacterium avium infection. | Antimicrob Agents Chemother | The comparative activities of newer Rifamycin analogs and the activity of rifabutin or rifapentine in combination with other antimycobacterial agents was evaluated in the beige (C57BL/6J; bgj/bgj) mouse model of disseminated Mycobacterium avium infection. Rifabutin and rifapentine at 20 mg/kg of body weight had comparable activities. P/DEA and CGP 7040 at 20 mg/kg were less active. The combination of ethambutol at 125 mg/kg and rifabutin at 20 mg/kg resulted in a slight increase in activity beyond that seen with rifabutin alone against organisms in the spleens. The combination of ethambutol and rifapentine at 20 mg/kg resulted in a modest increase in activity beyond that seen with rifapentine alone against organisms in the lungs. The combination of ethionamide at 125 mg/kg and rifapentine resulted in a decrease in activity compared with that for rifapentine alone. The combination of clofazimine at 20 mg/kg and rifapentine resulted in increased activity in the mouse model. The combination of clofazimine and rifapentine (or rifabutin) appears to be an attractive regimen that should be evaluated for the treatment of human infections due to M. avium complex. |
| 1991 | High-performance liquid chromatographic determination of rifapentine and its metabolite in human plasma by direct injection into a shielded hydrophobic phase column. | J Chromatogr | A simple high-performance liquid chromatographic method for determination of rifapentine, a cyclopentyl semisynthetic analogue of Rifamycin belonging to the class of piperazinyl hydrazone derivatives of 3-formylRifamycin SV, and its metabolite, 25-desacetylrifapentine, in human plasma was developed using direct injection of the sample onto a Supelco LC HISEP column. The mean recovery was 100.3% for rifapentine and 99.7% for the metabolite and the precision of the assays was 3% and 7%, respectively. The limit of determination was 0.2 micrograms/ml and the method was validated for concentrations up to 64 micrograms/ml for rifapentine and 32 micrograms/ml for the metabolite. The results correlated well with those of the microbiological assay with Sarcina lutea as test organism. |
| 1989 | The activity of rifampin and analogs against Staphylococcus epidermidis biofilms in a CAPD environment model. | Am J Nephrol | Rifampin has been noted to exhibit exceptional antimicrobial activity against Staphylococcus epidermidis biofilms as compared to commonly used antibiotics. To further explore this unique effect of rifampin, we evaluated the antimicrobial activity of three commercially available preparations of rifampin, two rifampin analogs (CGP29861 and rifapentine) and the parent compound Rifamycin SV. These were tested against standardized S. epidermidis biofilms in various milieus. All six members of the Rifamycin group tested demonstrated marked antimicrobial activity but with minor foci of resisters when tested in a peptone water environment. The microscopy of the exposed biofilms showed profound lysis and morphological distortion of the remaining cells. The synergistic elimination of the foci of resistance was achieved in an environment of fresh peritoneal dialysis (PD) solution or by the addition of vancomycin. Neither vancomycin nor fresh PD solution demonstrated significant antimicrobial activity when tested alone with biofilm preparations. Spent PD fluid markedly antagonized the activity of the Rifamycins with the exception of the rifampin analogs, an effect primarily of pH. The synergistic effect of vancomycin with the Rifamycins was not affected either by protein content or pH, leaving the antagonistic properties of spent PD fluid unexplained. The variable activity of the different members of the Rifamycin group underlines the importance of structural differences in determining their interaction with bacterial biofilms. Further precision of the nature of these structural interactions is seen to have considerable potential for therapeutic advancement of catheter-associated sepsis. |
| 1987 | In vitro and ex vivo influence of rifamycins on human phagocytes. | Chemioterapia | We studied the effects of Rifamycin SV, rifampicin and rifapentine on human phagocyte functions. Rifamycins inhibited in vitro neutrophil chemotaxis in the range of their therapeutic levels, and they significantly affected the survival of a Rifamycin-sensitive strain of Staphylococcus aureus inside human monocytes. Both effects were related to the intraphagocytic penetration of these antibiotics. For the ex vivo studies, 600 mg of rifampicin were orally administered to five subjects with defective S. aureus killing. A significant reduction of neutrophil chemotaxis and increased activity against S. aureus were shown 150 and 210 min after administration of the drug. |
| 1987 | In vitro observations on the suitability of new rifamycins for the intermittent chemotherapy of tuberculosis. | Tubercle | The bactericidal activity of six new Rifamycin derivatives--rifabutin (RBU), FCE 22250 (F22), rifapentine (RPE), CGP 29861 (C29), CGP 7040 (C70) and CGP 27557 (C27) and rifampicin (RMP)--have been measured against log phase and, as a better test of sterilising activity, against stationary phase cultures of Mycobacterium tuberculosis, H37Rv. The order of activity of 1.0 and 0.2 mg/l Rifamycin against log phase cultures was RMP greater than RPE & C27 greater than RBU & C29 greater than C70. The order of activity of 1.0 and 0.4 mg/l, adjusted for stability of the Rifamycin, against stationary phase cultures was F22 & RMP greater than RBU greater than RPE greater than C27 & C29 greater than C70. Viable counts were done during and after pulsed exposures of 6, 24 or 96 h to C29 and RMP. The curves were similar though C29 was less bactericidal and the lag period before recovery was 1-2 days longer. F22, having high bactericidal activity against stationary organisms and a long half-life, was considered likely to be the most effective sterilising drug. |
| 1987 | In vitro activity of new rifamycins against rifampicin-resistant M. tuberculosis and MAIS-complex mycobacteria. | Tubercle | Comparisons were made of the in vitro activity of rifampicin, and the Rifamycin derivatives, rifapentine, rifabutin, CGP 29861, CGP 7040 and CGP 27557, against rifampicin-sensitive and rifampicin-resistant strains of Mycobacterium tuberculosis and against the Mycobacterium avium/intracellulare/scrofulaceum (MAIS) complex. The new Rifamycins had MICs four to eight times lower than those of rifampicin against sensitive M. tuberculosis strains. Of the 35 rifampicin-resistant strains of M. tuberculosis, 31% were sensitive to rifabutin but only 3-11% to the other Rifamycins. The proportions of the MAIS strains found to be sensitive were 35% for rifampicin, 50-60% for CGP 27557, rifapentine and rifabutin and 85-92% for CGP 29861 and CGP 7040. |
| 1985 | In vitro activities of rifapentine and rifampin, alone and in combination with six other antibiotics, against methicillin-susceptible and methicillin-resistant staphylococci of different species. | Antimicrob Agents Chemother | The antistaphylococcal activity of rifapentine, a new Rifamycin SV derivative, was evaluated in vitro and compared with that of rifampin. A total of 313 staphylococcal strains freshly isolated from clinical material and including representatives of all currently recognized Staphylococcus species of human origin were used. The susceptibility to methicillin of all the test strains was determined preliminarily. Despite minor differences with some species, the MICs of rifapentine were found to be substantially similar to those of rifampin. Methicillin-resistant strains of all species were most resistant to rifapentine and rifampin than were their methicillin-susceptible counterparts. For most strains tested, the MBCs of both Rifamycins exceeded by twofold the respective MICs. Both the checkerboard dilution and time-kill methods were used to determine the interactions of rifapentine or rifampin with six different antibiotics: cefamandole, vancomycin, teicoplanin, gentamicin, erythromycin, and fusidic acid. No significant differences between the two Rifamycins in the combinations were observed against either methicillin-susceptible or methicillin-resistant strains. Minor differences were noted depending on the second antibiotic tested or the staphylococcal species examined. Antagonism was never observed, and indifference was the prevalent response. Cases of synergism were observed occasionally with the checkerboard method and slightly more often with the time-kill method. |
| 1984 | Pharmacokinetics of rifapentine, a new long lasting rifamycin, in the rat, the mouse and the rabbit. | J Antibiot (Tokyo) | A study on the pharmacokinetics of rifapentine, a new long-lasting Rifamycin, has been carried out in the rat, the mouse and the rabbit. The investigation was made using either radioactive or unlabelled rifapentine and both the total 14C and the unchanged compound were assayed. In the rat, the overall evidence obtained was: the oral absorption of rifapentine into central compartment, due to its poor water solubility, appears to be dose-dependent with a satisfactory oral absorption (84%) after a dose of 3 mg/kg, lower (65%) after 10 mg/kg; the antibiotic undergoes rapid liver uptake while it diffuses into the tissue compartment more slowly, with particular affinity for the adrenals, pancreas and kidneys; concentrations higher than in plasma were also measured in the lungs; elimination of rifapentine from the blood and tissue compartments suggests a non linear capacity-limited kinetics where the terminal elimination phase has monoexponential course. Terminal plasma half-life ranged between 14 and 18 hours; the compound is eliminated mainly via the bile with the feces (92% of dose). In mice rifapentine shows a kinetic profile resembling that obtained in rats, whereas in rabbits is metabolized and/or eliminated much more rapidly with a half-life of only 1.8 hours. |
| 1984 | Comparative uptake of rifampicin and rifapentine (DL473) by human neutrophils. | J Antimicrob Chemother | Rifapentine, a new cyclopentyl Rifamycin, was weight for weight less active than rifampicin against Staphylococcus aureus. It was, however, equally effective at reducing the survival of Staph. aureus within human neutrophils even at concentrations below the conventionally determined MIC. The intracellular survival of antibiotic-resistant Staph. aureus was affected by neither agent. The bactericidal activity of neutrophil sonicates after exposure to both antibiotics showed that rifapentine was concentrated three-fold more than rifampicin. Uptake was temperature dependent and rapidly reached a plateau within 10 min. Uptake of rifampicin was unaffected by pH whereas that of rifapentine was reduced when the pH was lowered from 7.3 to 5. Studies with the metabolic inhibitors, sodium cyanide and potassium fluoride, suggested a minor role for both oxidative and glycolytic metabolism in this process. However, neither inhibitor had any demonstrable effect on the intracellular killing of Staph. aureus by either rifapentine or rifampicin. |