3--hydroxy-5--(4-isobutylpiperazinyl)benzoxazinorifamycin and Disease-Models--Animal

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

Buruli ulcer (BU) is a skin disease caused by Mycobacterium ulcerans infection that requires long-term antibiotic treatment and/or surgical excision. In this study, we investigated the therapeutic efficacy of the rifamycin derivative, rifalazil (RLZ) (also known as KRM-1648), in an advanced M. ulcerans infection model. Six-week-old female BALB/c mice were infected with 3.25 x 104 colony-forming units (CFU) of M. ulcerans subcutaneously into the bilateral hind footpads. At 33 days post-infection, when the footpads exhibited significant redness and swelling, mice were treated orally with 5 or 10 mg/kg of RLZ for up to 15 weeks. Mice were followed for an additional 15 weeks following treatment cessation. Untreated mice exhibited a progressive increase in footpad redness, swelling, and erosion over time, and all untreated mice reached to endpoint within 5-8 weeks post-bacterial injection. In the RLZ-treated mice, footpad redness and swelling and general condition improved or completely healed, and no recurrence occurred following treatment cessation. After 3 weeks of treatment, the CFU counts from the footpads of recovered RLZ-treated mice showed a 104 decrease compared with those of untreated mice. We observed a further reduction in CFU counts to the detection limit following 6 to 15 weeks of treatment, which did not increase 15 weeks after discontinuing the treatment. Histopathologically, bacteria in the treated mice became fragmented one week after RLZ-treatment. At the final point of the experiment, all the treated mice (5mg/kg/day; n = 6, 10mg/kg/day; n = 7) survived and had no signs of M. ulcerans infection. These results indicate that the rifamycin analogue, RLZ, is efficacious in the treatment of an advanced M. ulcerans infection mouse model.

Topics: Animals; Anti-Bacterial Agents; Buruli Ulcer; Disease Models, Animal; Drug Therapy, Combination; Female; Mice; Mice, Inbred BALB C; Mycobacterium ulcerans; Rifampin; Rifamycins

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

The rifamycin rifalazil (RFZ), and derivatives (NCEs) were efficacious in a mouse model of Helicobacter pylori colonization. Select NCEs were more active in vitro and showed greater efficacy than RFZ. A systemic component contributes to efficacy.

Topics: Animals; Antibiotics, Antitubercular; Disease Models, Animal; Helicobacter Infections; Helicobacter pylori; Mice; Mice, Inbred C57BL; Microbial Sensitivity Tests; Rifamycins

Rifalazil (formerly known as KRM-1648) in combination with isoniazid has been found to be more active than rifampin/isoniazid. Administration of rifalazil/isoniazid for 12 weeks resulted in continued apparent sterilization of organs 6 months after cessation of therapy. In this study we evaluated the durability of rifalazil/isoniazid treatment. Female CD-1 mice were infected with Mycobacterium tuberculosis ATCC 35801 (strain Erdman). Rifalazil and isoniazid were given in combination for 6 and 12 weeks; no mycobacteria could be cultured from spleens and lungs at both the 6-week and 12-week time points. After completing treatment, groups of mice treated with rifalazil/isoniazid for 6 or 12 weeks were observed without any additional treatment. These observation groups were compared to groups of rifalazil/isoniazid-treated mice (6 and 12 weeks) given dexamethasone for 7 and 8 weeks, respectively. Modest regrowth was noted in the spleens and lungs of the group treated with rifalazil/isoniazid for 6 weeks. Regrowth in the 6-weeks group was enhanced slightly by treatment with dexamethasone. In contrast, no regrowth was noted in the 12-weeks rifalazil/isoniazid group, and treatment with dexamethasone did not result in any regrowth.

Topics: Animals; Antitubercular Agents; Colony Count, Microbial; Dexamethasone; Disease Models, Animal; Drug Therapy, Combination; Female; Glucocorticoids; Humans; Isoniazid; Lung; Mice; Mycobacterium tuberculosis; Rifamycins; Spleen; Treatment Outcome; Tuberculosis, Pulmonary

The newer rifamycin, rifalazil (RLZ) (previously known as KRM-1648), has been shown in prior experiments to be a highly potent drug against Mycobacterium tuberculosis. In this report, we studied the efficacy of RLZ in combination with pyrazinamide (PZA) and ethambutol (EMB) in a long-term in vivo experiment and compared their activity with the isoniazid (INH)-rifampin (RIF) combination which is presently used in the clinic. Combinations of RLZ with PZA alone or with both PZA and EMB were both found to have sterilizing activities comparable to that of the INH-RIF combination but significantly better activity with respect to relapse of infection. These results suggest that RLZ, or other agents with similar activity, could be combined with available agents to act as a potential alternative drug regimen to the currently used INH-RIF combination.

Topics: Animals; Antitubercular Agents; Colony-Forming Units Assay; Disease Models, Animal; Drug Therapy, Combination; Ethambutol; Female; Isoniazid; Mice; Pyrazinamide; Rifampin; Rifamycins; Tuberculosis

The Chinese traditional medicine mao-bushi-saishin-to (MBST), which has anti-inflammatory effects and has been used to treat the common cold and nasal allergy in Japan, was examined for its effects on the therapeutic activity of a new benzoxazinorifamycin, KRM-1648 (KRM), against Mycobacterium avium complex (MAC) infection in mice. In addition, we examined the effects of MBST on the anti-MAC activity of murine peritoneal macrophages (M phi s). First, MBST significantly increased the anti-MAC therapeutic activity of KRM when given to mice in combination with KRM, although MBST alone did not exhibit such effects. Second, MBST treatment of M phi s significantly enhanced the KRM-mediated killing of MAC bacteria residing in M phi s, although MBST alone did not potentiate the M phi anti-MAC activity. MBST-treated M phi s showed decreased levels of reactive nitrogen intermediate (RNI) release, suggesting that RNIs are not decisive in the expression of the anti-MAC activity of such M phi populations. MBST partially blocked the interleukin-10 (IL-10) production of MAC-infected M phi s without affecting their transforming growth factor beta (TGF-beta)-producing activity. Reverse transcription-PCR analysis of the lung tissues of MAC-infected mice at weeks 4 and 8 after infection revealed a marked increase in the levels of tumor necrosis factor alpha, gamma interferon (IFN-gamma), IL-10, and TGF-beta mRNAs. KRM treatment of infected mice tended to decrease the levels of the test cytokine mRNAs, except that it increased TGF-beta mRNA expression at week 4. MBST treatment did not affect the levels of any cytokine mRNAs at week 8, while it down-regulated cytokine mRNA expression at week 4. At week 8, treatment of mice with a combination of KRM and MBST caused a marked decrease in the levels of the test cytokines mRNAs, especially IL-10 and IFN-gamma mRNAs, although such effects were obscure at week 4. These findings suggest that down-regulation of the expression of IL-10 and TGF-beta is related to the combined therapeutic effects of KRM and MBST against MAC infection.

Topics: Animals; Anti-Bacterial Agents; Cytokines; Disease Models, Animal; Drug Synergism; Drugs, Chinese Herbal; Female; Free Radicals; Interleukin-10; Lung; Macrophages; Mice; Mice, Inbred BALB C; Mycobacterium avium-intracellulare Infection; Nitrogen; Rifamycins; RNA, Messenger; Transforming Growth Factor beta

We previously examined the effects of a Chinese medicine "Mao-Bushi-Saishin-To" (MBST) which has anti-inflammatory activity on the therapeutic efficacies of a benzoxazinorifamycin, KRM-1648 (KRM), against, Mycobacterium avium complex (MAC) infection induced in mice. MBST potentiated the therapeutic activity of KRM against MAC infection. In the present study, we examined the effects of another anti-inflammatory drug Glycyrrhizin, which is effective for chronic hepatitis, on the therapeutic efficacy of KRM against MAC infection induced in mice. First, KRM significantly inhibited the bacterial growth in the lungs and spleen of MAC-infected mice. Glycyrrhizin exhibited no therapeutic activity against MAC infection and did not affect the expression of the therapeutic efficacy of KRM. Secondly, treatment of murine peritoneal macrophages (M phi s) with Glycyrrhizin caused no significant changes in the M phi anti-MAC activity.

Topics: Animals; Anti-Inflammatory Agents, Non-Steroidal; Antibiotics, Antitubercular; Disease Models, Animal; Drug Interactions; Drug Therapy, Combination; Female; Glycyrrhizic Acid; Macrophages, Peritoneal; Mice; Mice, Inbred BALB C; Mycobacterium avium Complex; Rifamycins; Tuberculosis

Besides direct bactericidal activity, long-term effectiveness is one of the most important features to consider when developing new drugs for chemotherapy. In this study, we evaluated the ability of rifapentine (RFP), in monotherapy and combination therapy, to completely eradicate a Mycobacterium tuberculosis infection and to prevent relapse posttreatment in a Swiss mouse model. The combination of RFP, isoniazid (INH), and pyrazinamide (PZA) administered daily resulted in an apparent clearance of M. tuberculosis organisms in the lungs and spleens of infected mice after 10 weeks of treatment. However, 3 months after the cessation of therapy, bacterial regrowth occurred in mice treated for a 12-week period, indicating a relapse of infection. In intermittent treatment regimens of RFP in combination with INH and PZA, sterilization was achieved when mice were treated two to five times per week for 9 weeks. Bacterial growth was still observed in the once-weekly treatment group. Our results show that mouse models can predict important parameters for new drugs. We stress the necessity for long-term posttreatment observation in animal models for the routine evaluation of new drugs for antituberculosis chemotherapy.

Topics: Animals; Antibiotics, Antitubercular; Antitubercular Agents; Disease Models, Animal; Drug Therapy, Combination; Evaluation Studies as Topic; Female; Isoniazid; Mice; Mycobacterium tuberculosis; Pyrazinamide; Rifampin; Rifamycins; Tuberculosis

In this study, profiles of infection due to Mycobacterium avium complex (MAC) in CB-17 SCID mice deficient in T and B cell functions were examined, when mice were given or not given a new benzoxazinorifamycin, KRM-1648 (KRM), during the course of infection. When mice were infected intravenously with MAC, the bacterial loads in their visceral organs were larger than those of their co-isogenic CB-17 counterparts. The incidence and the degree of gross lung lesions were less in SCID mice compared to CB-17 mice. Athymic BALB/c nude mice showed similar profiles of the infection. Beige mice showed more severe gross lesions and larger bacterial loads in the lungs than did SCID and athymic BALB/c nude mice. When MAC was infected subcutaneously into the hind footpads of mice, disseminated growth of organisms in the footpads, blood, and visceral organs was seen in SCID mice, but not in CB-17 or BALB/c mice. KRM exhibited the same level of therapeutic effect on SCID mice infected with MAC via the intravenous route in terms of inhibiting bacterial growth in the lungs and kidneys, as in cases of CB-17 and BALB/c mice with normal T-cell functions. In beige mice, the degree of growth inhibition of MAC due to KRM treatment was significantly greater than that achieved in SCID mice.

Topics: Animals; Antibiotics, Antitubercular; Bacteremia; Disease Models, Animal; Disease Progression; Lung; Mice; Mice, Inbred BALB C; Mice, Nude; Mice, SCID; Mycobacterium avium Complex; Mycobacterium avium-intracellulare Infection; Rifamycins; Species Specificity; Time Factors; Tuberculosis, Pulmonary

Although various antimicrobial agents exhibit appreciable microbicidal activity in the early phase (weeks 2 t0 4) of Mycobacterium avium complex (MAC) infection induced in mice, progressive bacterial regrowth subsequently occurs. To clarify the reason for this pattern of changes, we studied changes in the levels of various cytokines in tissue at sites of infection (spleens and lungs) of MAC-infected mice which were or were not given a benzoxazinorifamycin, KRM-1648 (KRM). Levels of the proinflammatory cytokines tumor necrosis factor alpha (TNF-alpha) and gamma interferon (IFN-gamma) in tissues temporarily increased at around weeks 2 to 4 after infection, rapidly decreased thereafter, and returned to normal by week 8. Similar but somewhat delayed changes were noted for levels of interleukin 10 (IL-10) and transforming growth factor beta (TGF-beta), immunosuppressive cytokines with macrophage (M phi)-deactivating activity, in tissue, except that TGF-beta levels in the spleen remained high during weeks 4 to 8. KRM treatment blocked the increase in the levels of all of those cytokines in tissue in the early phase of infection, most strongly at week 4. IL-6 levels were beneath the limit of detection throughout the observation period. Bacterial loads in the visceral organs decreased during the first 2 weeks, and KRM treatment markedly promoted this decrease. However, regrowth of MAC organisms began at weeks 2 to 4 and continued thereafter, even in KRM-treated mice. Splenocytes and splenic M phi s of MAC-infected mice (week 2) produced and/or released into the culture fluid significant amounts of TNF-alpha (in a cell-bound form), IFN-gamma, and IL-10, but not TGF-beta, during 3 days of cultivation. A substantial amount of TGF-beta was produced during 2 weeks of cultivation of peritoneal M phi s. KRM itself did not significantly affect the IL-10- and TGF-beta-producing ability of cultured M phi s. These findings suggest that IL-10 and TGF-beta play important roles in the regrowth of MAC organisms seen during the course of KRM treatment.

Topics: Animals; Antibiotics, Antitubercular; Cytokines; Disease Models, Animal; Female; Interferon-gamma; Interleukin-10; Lung; Macrophages; Mice; Mice, Inbred BALB C; Mycobacterium avium Complex; Mycobacterium avium-intracellulare Infection; Rifamycins; Spleen; Transforming Growth Factor beta; Tumor Necrosis Factor-alpha

As a paradigm for chronic infectious diseases, tuberculosis exhibits a variety of clinical presentations, ranging from primary pulmonary tuberculosis to reactivation tuberculosis and cavitary disease. To date, the animal models used in evaluating chemotherapy of tuberculosis have been high-dose intravenous models that mimic the disseminated forms of the disease. In the present study, we have used a low-dose aerosol exposure model which we feel better reflects newly diagnosed tuberculosis in patients converting to tuberculin positivity. As appropriate examples of chemotherapy, four rifamycins (rifampin, rifabutin, rifapentine, and KRM-1648) were tested, first in an in vitro murine macrophage model and then in the low-dose aerosol infection model, for their activity against Mycobacterium tuberculosis. In both models, KRM-1648 had the highest level of activity of the four compounds. In the infected-lung model, rifabutin, rifapentine, and KRM-1648 all had sterilizing activity when given orally at 5 mg/kg of body weight per day. When given at 2.5 mg/kg/day, KRM-1648 had the highest level of activity of the four drugs, reducing the bacterial load by 2.7 logs over 35 days of therapy.

Topics: Aerosols; Animals; Antibiotics, Antitubercular; Disease Models, Animal; Female; Lung; Macrophages; Mice; Mice, Inbred C57BL; Mycobacterium tuberculosis; Rifamycins; Tuberculosis

The in vivo anti-Mycobacterium leprae activity of the newly synthesized benzoxazinorifamycin, KRM-1648, was studied. KRM-1648 was given orally to athymic nude mice, infected subcutaneously with M. leprae in the hindfoot pad, at doses between 0.001 and 0.01 mg of the drug/mouse/day six times per week, from day 31 to day 80. KRM-1648 administration markedly suppressed bacterial growth in the foot pads for 360 days. KRM-1648 given daily at the dose of 0.01 mg/mouse elicited a 2-4-log decrease in the number of acid-fast bacilli. The therapeutic effects of KRM-1648 were significantly higher than that of rifampin when both drugs were given in the same dosage. Moreover, when mice were fed a KRM-1648-containing diet (0.00004%-0.0004%), the drug displayed an even higher efficacy against M. leprae infection, causing an almost 4-log decrease in the number of leprosy bacilli in the infected foot pad compared to untreated controls.

Topics: Administration, Oral; Animals; Disease Models, Animal; Dose-Response Relationship, Drug; Female; Leprostatic Agents; Leprosy; Mice; Mice, Inbred BALB C; Mice, Nude; Mycobacterium leprae; Rifampin; Rifamycins