3--hydroxy-5--(4-isobutylpiperazinyl)benzoxazinorifamycin and Chlamydia-Infections

Rifalazil is a benzoxazinorifamycin which inhibits bacterial DNA-dependent RNA polymerase. The benzoxazine ring endows benzoxazinorifamycins with unique physical and chemical characteristics which favor the use of rifalazil and derivatives in treating diseases caused by the obligate intracellular pathogens of the genus chlamydia. Minimal inhibitory concentrations of benzoxazinorifamycins against chlamydia are in the pg/mL range. These compounds have potential as monotherapeutic agents to treat chlamydia-associated disease because they retain activity against chlamydia strains resistant to currently approved rifamycins such as rifampin. A pivotal clinical trial with rifalazil has been initiated for the treatment of peripheral arterial disease. The rationale for this innovative use of rifalazil, including the association of C. pneumoniae in atherosclerotic plaque formation, as well as rifalazil's potency and efficacy against chlamydia in both preclinical and clinical studies, is discussed. Other benzoxazino derivatives may have utility as stand-alone topical antibacterials or combination antibacterials to treat serious Gram-positive infections. None of the benzoxazinorifamycins examined to date induce the cytochrome P450 3A4 enzyme. This is in contrast to currently approved rifamycins which are strong inducers of P450 enzymes, resulting in drug-drug interactions that limit the clinical utility of this drug class.

Topics: Animals; Anti-Bacterial Agents; Atherosclerosis; Chlamydia Infections; Chlamydophila pneumoniae; Humans; Peripheral Vascular Diseases; Rifampin; Rifamycins

Rifalazil and other benzoxazinorifamycins (new chemical entities [NCEs]) are rifamycins that contain a distinct planar benzoxazine ring. Rifalazil has excellent antibacterial activity, high intracellular levels and high tissue penetration, which are attributes that favour its use in treating diseases caused by the obligate intracellular pathogens of the genus Chlamydia. Recent studies have shown that rifalazil has efficacy in the treatment of human sexually transmitted disease caused by Chlamydia trachomatis. The extraordinary potency of rifalazil and other NCEs, such as ABI-0043, extends to the related microorganism, C. pneumoniae, a respiratory pathogen that can disseminate and persist chronically in the vasculature, resulting in increased plaque formation in animal studies. A pivotal clinical trial with rifalazil has been initiated for the treatment of peripheral arterial disease. Other opportunities include gastric ulcer disease caused by Helicobacter pylori and antibiotic-associated colitis caused by infection with Clostridium difficile in the colon. The NCEs could prove to be valuable as follow-on compounds in these indications, as rifampin replacements in antibacterial combination therapy or as stand-alone topical antibacterials (e.g., to treat acne). Neither rifalazil nor NCEs appear to induce the cytochrome P450 3A4, an attribute of rifampin that can result in adverse events due to drug-drug interactions.

Topics: Animals; Anti-Bacterial Agents; Atherosclerosis; Chlamydia Infections; Chlamydia trachomatis; Chlamydophila pneumoniae; Chlamydophila psittaci; Coronary Artery Disease; Disease Models, Animal; Drug Administration Schedule; Drug Evaluation, Preclinical; Drug Resistance, Bacterial; Humans; Microbial Sensitivity Tests; Randomized Controlled Trials as Topic; Rifamycins

A randomized, double-blind study comparing single-dose chlamydia therapies of oral rifalazil (25 mg) and azithromycin (1 g) was conducted in 82 women with uncomplicated genital Chlamydia trachomatis infection. The microbiologic cure rate of C. trachomatis with rifalazil (n = 33) was 84.8% at the visit on day 22 to 26 (test-of-cure visit), versus 92.1% with azithromycin (n = 38), and the number of treatment failures in each group was 5 and 3, respectively. The difference in cure rate was -7.3%, with a lower limit of the 95% confidence interval (95% CI) of -22.5, and thus, noninferiority was not established at the prespecified margin (lower limit of CI of -15%). The overall treatment-emergent adverse event (TEAE) and treatment-related TEAE rates were lower in the rifalazil group (68% and 55%) than in the azithromycin group (71% and 62%), respectively. Subjects classified as treatment failures at day 22 to 26 had a lower mean plasma concentration of rifalazil at the visit on day 8 to 12 than those classified as treatment cures, but this difference was not significant; however, the levels were similar for both groups at the visit on day 22 to 26. A single 25-mg dose of rifalazil was well tolerated and eradicated C. trachomatis in most of these women with uncomplicated genital C. trachomatis infection. (The study was registered at clinicaltrials.gov under registration no. NCT01631201).

Topics: Adult; Anti-Bacterial Agents; Azithromycin; Chlamydia Infections; Chlamydia trachomatis; Double-Blind Method; Endpoint Determination; Female; Genital Diseases, Female; Humans; Rifamycins; Treatment Outcome; Young Adult

A potentially strong association exists between Chlamydia pneumoniae and atherosclerosis, but the clinical benefits of antibiotic therapy have not been demonstrated. Preliminary studies of antibiotic therapy in peripheral artery disease have shown a decreased need for revascularization and improved walking ability. The objective of this phase-III trial was to assess the effect of a potent anti-Chlamydial agent, rifalazil, on peak walking time in patients with symptomatic peripheral artery disease.. Patients with intermittent claudication secondary to peripheral artery disease who were seropositive for C pneumoniae were randomized to 25 mg rifalazil once weekly for 8 weeks or matching placebo. Two hundred ninety-seven patients were enrolled from 3 countries and were followed up for 1 year. The mean+/-SD ankle brachial index at baseline was 0.63+/-0.16. The primary end point, change from baseline in log peak walking time on a graded treadmill, was assessed 180 days after randomization. Secondary end points included changes in claudication onset time and quality of life, assessed with the Walking Impairment Questionnaire and the Short Form Medical Outcomes 36. No benefit of rifalazil therapy was found in the primary or any secondary end point among this cohort of patients with peripheral artery disease. The group treated with rifalazil improved their peak walking times by 23% (95% confidence interval, 15 to 31) from baseline to day 180, whereas the placebo group improved by 18% (95% confidence interval, 11 to 26; P=0.38). Peak walking time, claudication onset time, Walking Impairment Questionnaire, and Short Form Medical Outcomes 36 showed no treatment-by-time interaction during the 360-day study period. Thirty-two adjudicated cardiovascular events occurred, 16 in each treatment group.. Rifalazil did not improve exercise performance or quality of life in patients with intermittent claudication. No safety concerns were identified. Given the very small effect size, it is unlikely that larger studies would demonstrate a symptomatic benefit of this therapy in peripheral artery disease.

Topics: Aged; Antibiotics, Antitubercular; Chlamydia Infections; Chlamydophila pneumoniae; Double-Blind Method; Endpoint Determination; Exercise Test; Female; Follow-Up Studies; Humans; Intermittent Claudication; Male; Middle Aged; Peripheral Vascular Diseases; Prospective Studies; Rifamycins

To determine the safety and effectiveness of single-dose rifalazil, a new rifamycin, for the treatment of nongonococcal urethritis (NGU).. Randomized, double-blind trial comparing rifalazil, 2.5, 12.5 or 25 mg, with 1.0 g azithromycin for the treatment of NGU. One hundred and seventy men were evaluated for Chlamydia trachomatis, Ureaplasma urealyticum, and Mycoplasma genitalium infection before therapy and 2- and 5-weeks posttreatment.. C. trachomatis, M. genitalium, and U. urealyticum were present in 42%, 24%, and 28% of subjects, respectively. Microbiologic eradication of C. trachomatis with rifalazil 25 mg at 2- and 5- weeks was 85% and 83%, respectively. Rifalazil was ineffective in eradicating M. genitalium and U. urealyticum. Overall clinical cure rates at 2- and 5-weeks were 86% (95% CI 67-96) and 59% (39-78) in the rifalazil-treated 25 mg group, and 77% (56-91) and 63% (41-81) in the azithromycin-treated group.. Rifalazil was well tolerated and eradicates C. trachomatis but not M. genitalium and U. ureaplasma in men with NGU.

Topics: Adult; Anti-Bacterial Agents; Azithromycin; Chlamydia Infections; Chlamydia trachomatis; Double-Blind Method; Drug Administration Schedule; Humans; Male; Mycoplasma genitalium; Mycoplasma Infections; Rifamycins; Sexually Transmitted Diseases, Bacterial; Treatment Outcome; Ureaplasma Infections; Ureaplasma urealyticum; Urethritis

The efficacy of rifalazil and other benzoxazinorifamycins was tested in a mouse model of lung infection against Chlamydia pneumoniae. Rifalazil and six related new chemical entities all showed efficacy after one dose per day for 3 days at either 3 or 1 mg/kg of body weight.

Topics: Animals; Anti-Bacterial Agents; Chlamydia Infections; Chlamydophila pneumoniae; Disease Models, Animal; Lung; Male; Mice; Microbial Sensitivity Tests; Rifamycins

Chlamydia species are widely disseminated obligate intracellular pathogens that primarily cause urogenital, ocular, and respiratory infections. In these studies, we show that exposing mammalian cells to antibacterial agents prior to Chlamydia inoculation protects the host cells against subsequent challenge by chlamydiae (the protective effect [PE]). Rifalazil exhibited a considerably stronger PE than did azithromycin, rifampin, doxycycline, and ofloxacin. Specifically, 0.002 microg/ml rifalazil incubated for 1 day with a monolayer of McCoy cells was sufficient to protect against a challenge 2 days later with Chlamydia trachomatis serovar D (UW-3). The PE was observed with five different mammalian cell lines and with a variety of C. trachomatis and Chlamydia pneumoniae isolates. The duration of the PE was 6 to 12 days for rifalazil (depending on the cell line), a maximum of 3 days for azithromycin, and less than a day for the other drugs tested. For rifalazil, the PE was shown to be mediated by inhibition of the chlamydial RNA polymerase since mutants with altered RNA polymerases had correspondingly altered PEs. These results suggest that rifalazil may be unique in its ability to prevent infection with obligate intracellular pathogens for a considerable time after treatment. This characteristic may be of particular public health value in reducing reinfection with chlamydiae.

Topics: Anti-Bacterial Agents; Cell Line; Chlamydia; Chlamydia Infections; Humans; Microbial Sensitivity Tests; Recurrence; Rifamycins; Time Factors

Rifalazil, a semisynthetic rifamycin, was shown previously to have exceptional potency against Chlamydia trachomatis (MIC of 0.00025 microg/ml). We therefore tested 250 additional rifamycin derivatives and identified 12 with activities that are eightfold more potent than that of rifalazil. These compounds also showed exceptional activities against rifampin-resistant strains that carry missense mutations in the rpoB gene. The antimicrobial potency and intracellular penetration of these agents suggest their potential in treatment of chlamydial infections.

Topics: Anti-Bacterial Agents; Chlamydia Infections; Chlamydia trachomatis; Humans; Mutation, Missense; Rifamycins

ABI-1648 (rifalazil) is a semisynthetic rifamycin with potent bactericidal activity against intracellular respiratory bacteria, including Mycobacterium tuberculosis, and a long half-life (approximately 60 h) and thus can be administered once weekly. We therefore tested the in vitro activities of ABI-1648, its derivatives ABI-1657 and ABI-1131, azithromycin, and levofloxacin against 10 strains of Chlamydia trachomatis and 10 recent clinical isolates of Chlamydia pneumoniae. The MICs at which 90% of the isolates were inhibited and the minimal bactericidal concentration at which 90% of the isolates were killed for ABI-1648, ABI-1657, and ABI-1131 were 0.0025 micro g/ml for C. trachomatis and 0.00125 to 0.0025 micro g/ml for C. pneumoniae. ABI-1648, ABI-1657, and ABI-1131 were 10- to 1,000-fold more active than azithromycin and levofloxacin.

Topics: Anti-Bacterial Agents; Anti-Infective Agents; Antibiotics, Antitubercular; Azithromycin; Chlamydia Infections; Chlamydia trachomatis; Chlamydophila pneumoniae; Humans; Levofloxacin; Microbial Sensitivity Tests; Ofloxacin; Rifamycins