3--hydroxy-5--(4-isobutylpiperazinyl)benzoxazinorifamycin and Tuberculosis

Topics: Animals; Antibiotics, Antitubercular; Humans; Rifamycins; Treatment Outcome; Tuberculosis

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.

Topics: Animals; Anti-Bacterial Agents; Anti-Infective Agents; Antibiotics, Antitubercular; Drug Design; Fluoroquinolones; Humans; In Vitro Techniques; Macrolides; Mycobacterium; Mycobacterium avium Complex; Mycobacterium Infections; Mycobacterium tuberculosis; Rifamycins; Tuberculosis

Mycobacterium tuberculosis antigen 85 is induced in vitro by isoniazid (INH); its sustained induction in sputum during tuberculosis (TB) therapy predicts relapse. In this trial, rifampin or rifalazil inhibited the induction of sputum antigen 85 by INH in a dose-dependent fashion. This approach may facilitate the evaluation of new TB drugs.

Topics: Acyltransferases; Antibiotics, Antitubercular; Antigens, Bacterial; Antitubercular Agents; Biomarkers; Colony Count, Microbial; Humans; Isoniazid; Kinetics; Recurrence; Rifampin; Rifamycins; Sputum; Tuberculosis

Tuberculosis (TB) is one of the most significant world health problems, responsible for 1.5 M deaths in 2020, and yet, current treatments rely largely on 40 year old paradigms. Although the rifamycins (RIFs), best exemplified by the drug rifampin (RMP), represent a well-studied and therapeutically effective chemotype that targets the bacterial RNA polymerase (RNAP), these agents still suffer from serious drawbacks including the following: 3-9 month treatment times; cytochrome P450 (Cyp450) induction [particularly problematic for human immunodeficiency virus-

Topics: Adult; HIV Infections; Humans; Pregnane X Receptor; Rifampin; Rifamycins; Tuberculosis

Rifampin (RMP), a very potent inhibitor of the

Topics: Animals; DNA-Directed RNA Polymerases; Drug Resistance, Bacterial; Mice; Mycobacterium tuberculosis; Rifampin; Rifamycins; Tuberculosis

Previous experiments with rifalazil (RLZ) (also known as KRM-1648) in combination with isoniazid (INH) demonstrated its potential for short-course treatment of Mycobacterium tuberculosis infection. In this study we investigated the minimum RLZ-INH treatment time required to eradicate M. tuberculosis in a murine model. RLZ-INH treatment for 6 weeks or longer led to a nonculturable state. Groups of mice treated in parallel were killed following an observation period to evaluate regrowth. RLZ-INH treatment for a minimum of 10 weeks was necessary to maintain a nonculturable state through the observation period. Pyrazinamide (PZA) was added to this regimen to determine whether the treatment duration could be further reduced. In this model, the addition of PZA did not shorten the duration of RLZ-INH treatment required to eradicate M. tuberculosis from mice. The addition of PZA reduced the number of mice in which regrowth occurred, although the reduction was not statistically significant.

Topics: Animals; Antibiotics, Antitubercular; Mice; Rifamycins; Tuberculosis

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 antimicrobial activities of levofloxacin, clarithromycin and KRM-1648 against Mycobacterium tuberculosis (MTB) and Mycobacterium avium complex (MAC) residing in Mono Mac 6 human macrophage-like cells (MM6-Mphis) and A-549 human type II alveolar epithelial cells (A-549 cells) were studied. We measured the antimicrobial activity of test drugs in terms of effects on the behaviour of intracellular organisms during a 7-day cultivation of MTB- or MAC-infected cells in the medium containing the drugs at Cmax doses. Microbicidal action of levofloxacin against intracellular MTB within A-549 cells was markedly less than its activity against the same organisms in MM6-Mphis. The same effect was also noted for the action of KRM-1648 against MAC organisms but this did not occur with clarithromycin. The MIC of KRM-1648 for MAC multiplying within A-549 cells was 32 times larger than that for MAC residing in MM6-Mphis. These findings indicate that MTB and MAC organisms replicating in the type II lung epithelial cells resist the action of certain antimycobacterial agents such as quinolones and rifamycin derivatives but not when the organisms are contained in macrophages. It appears that the antimicrobial action of certain drugs against intracellular mycobacteria is differentially manifested depending on the types of host cells, i.e. professional phagocytes (MM6-Mphis) or non-professional phagocytes (A-549cells), in which the organisms are contained.

Topics: Anti-Bacterial Agents; Cell Line; Clarithromycin; Epithelial Cells; Humans; Levofloxacin; Macrophages; Microbial Sensitivity Tests; Mycobacterium avium Complex; Mycobacterium avium-intracellulare Infection; Mycobacterium tuberculosis; Ofloxacin; Pulmonary Alveoli; Rifamycins; Tuberculosis

The effects of half-sized secretory leukocyte protease inhibitor or diclofenac sodium administered alone or in combination with the benzoxazinorifamycin KRM-1648 on the therapeutic efficacy of KRM-1648 against Mycobacterium avium complex (MAC) in mice were studied. Neither of the two anti-inflammatory drugs affected the efficacy of KRM-1648, while they exerted significant modulating effects on tumor necrosis factor alpha production by MAC-infected macrophages.

Topics: Animals; Anti-Inflammatory Agents, Non-Steroidal; Antibiotics, Antitubercular; Cytokines; Diclofenac; Drug Therapy, Combination; Mice; Mice, Inbred BALB C; Mycobacterium avium Complex; Protease Inhibitors; Rifamycins; Tuberculosis

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

The in-vitro activities of KRM-1648, a new benzoxazinorifamycin, clarithromycin and levofloxacin against clinical isolates of Mycobacterium avium complex (MAC) were measured using various methods of assay and compared with their in-vivo therapeutic activities against MAC infection in mice. The MICs varied according to drug in the order KRM-1648 << clarithromycin < levofloxacin. However, KRM-1648 and clarithromycin but not levofloxacin had similar therapeutic outcomes in MAC-infected mice. KRM-1648 and clarithromycin given at clinical dosages caused 1 to 2 log unit reductions in bacterial loads in the lungs of host mice. The values of Cmax (lung)/MBC were more closely related to the therapeutic efficacy of these drugs in mice than were MICs and MBCs alone. Potent microbicidal activity was observed with KRM-1648 and clarithromycin but not with levofloxacin against extracellularly growing MAC (EG-MAC) in a liquid medium. These two agents caused more than 3 log unit killing of MAC during a 5 day incubation, when added at concentrations equivalent to Cmax (lung). The anti-EG-MAC bactericidal activity of these drugs was greater than their efficacy in mice in vivo. KRM-1648 and clarithromycin but not levofloxacin caused respectively 2 and 0.5 log unit killing of intracellularly growing MAC (IG-MAC) in murine peritoneal macrophages. The profiles of bacterial killing effects of these agents against IG-MAC accurately reflected their therapeutic effects in mice, although the in-vivo activity of KRM-1648 was still overestimated using even this parameter.

Topics: Animals; Anti-Bacterial Agents; Clarithromycin; Female; Levofloxacin; Lung; Macrophages, Peritoneal; Mice; Mice, Inbred BALB C; Microbial Sensitivity Tests; Mycobacterium avium; Ofloxacin; Phagocytosis; Rifamycins; Tuberculosis

This study aims to compare in vivo activity of benzoxazinorifamycin KRM-1648 (KRM) with those rifampicin (RFP) and rifabutin (RBT) against experimental murine tuberculosis.. Mice were infected with Mycobacterium tuberculosis or M. bovis by the intratracheal (i.t.) or intravenous (i.v.) routes, and treated for 10 days with various doses of each drug starting from the 9th or 11th day after the TB-infection.. (A) A rapid test for in vivo evaluation of three rifamycins was conducted by examining the survival days of treated mice infected with 106 cfu of M. bovis Ravenel. Mice treated with KRM exhibited 2.13.7 times longer survival times, in comparison with those treated with RFP or RBT. (B) In the i.t.-model of M. bovis Ravenel infection, three rifamycin derivatives gave "distinctive dose-response curves" in the correlation of dose sizes with the mean survival times or "log10CFU/lungs reductions". (C) In M. tuberculosis Kurono infection models, the ranking of the anti-TB activity of the three rifamycins in each organ was as follows: i.t.-and i.v.-lungs: KRM >> RFP not equal to RBT, i.v.-spleen: KRM not equal to RBT > RFP, i.v.-liver: KRM not equal to RBT > RFP. (D) Based on the results of "log10CFU reduction" in different organs in M. tuberculosis Kurono infection models, "characteristic in vivo activity patterns of each rifamycin" were obtained. (E) The therapeutic efficacy of KRM in lungs was greater than in spleen and liver with any dose. In contrast, RBT exhibited more remarkable in vivo activity in the spleen and liver than in lungs.. The prominent in vivo activity of KRM may allow small dose for effective therapy; 1/3 dose or less in comparison with those of RFP or RBT, or intermittent therapy of tuberculosis.

Topics: Animals; Antibiotics, Antitubercular; Female; Mice; Mice, Inbred BALB C; Mycobacterium bovis; Rifabutin; Rifampin; Rifamycins; Tuberculosis

We examined the effects of such drugs having anti-inflammatory activity as half-sized secretory leukocyte protease inhibitor (1/2 SLPI) and Chinese traditional medicines, Yokuinin (YOK) and Mao-Bushi-Saishin-To (MBST), on therapeutic efficacies of benzoxazinorifamycin KRM-1648 against Mycobacterium avium complex (MAC) infection induced in mice, since it is possible that these agents inhibit the increase in tissue levels of immunosuppressive cytokines due to MAC infection. First, Zymosan A-induced murine peritoneal macrophages treated with either 1/2 SLPI, YOK or MBST at 37 degrees C for 2 days were infected with M. avium N-444 and further cultivated in the medium with or without addition of 1/2 SLPI, YOK or MBST at 37 degrees C for up to 7 days. Treatment of macrophages with these drugs caused some decrease in the intracellular growth of the organisms. Secondly, we evaluated effects of 1/2 SLPI, YOK and MBST on the therapeutic efficacy of benzoxazinorifamycin KRM-1648 against M. avium infection induced in mice. When MAC-infected mice were given KRM-1648 (20 mg/kg) alone, or in combination with 1/2 SLPI (100 mg/kg), YOK (50 mg/kg), or MBST (50 mg/kg), by gavage, except for 1/2 SLPI which was given via i.p. route, once a week, from day 1 for up to 8 weeks after infection, these drugs did not affect the expression of therapeutic activity of KRM-1648. When MAC-infected mice were given KRM-1648 alone (once a week), or in combination with YOK (five times per week) or MBST (five times per week), MBST increased the expression of therapeutic activity of KRM-1648. These findings indicate that suppression of inflammatory reactions using MBST is capable to improve the therapeutic efficacy of KRM-1648 in MAC infection. Moreover, these results also mean that combined use of these drugs in MAC patients receiving KRM-1648 therapy may not cause any disadvantages to the therapeutic efficacy of KRM-1648.

Topics: Animals; Anti-Bacterial Agents; Antibiotics, Antitubercular; Cells, Cultured; Drug Therapy, Combination; Drugs, Chinese Herbal; Macrophages, Peritoneal; Mice; Mycobacterium avium; Proteinase Inhibitory Proteins, Secretory; Proteins; Rifamycins; Secretory Leukocyte Peptidase Inhibitor; Tuberculosis

We compared the in-vitro antimycobacterial activities of rifabutin and KRM-1648, two rifamycin derivatives, with that of rifampicin against 163 strains of Mycobacterium tuberculosis. We also evaluated the correlation between the level of resistance to rifampicin, rifabutin and KRM-1648 and genetic alterations in the rpoB gene. All 82 strains susceptible to rifampicin or resistant to rifampicin with MICs < or = 16 mg/L were susceptible to rifabutin and KRM-1648 with MICs < or = 1 mg/L. Seventy-six of 81 strains resistant to rifampicin with MICs > or = 32 mg/L were resistant to both rifabutin and KRM-1648, but with lower MICs than those of rifampicin. KRM-1648 showed more potent antimycobacterial activity than rifabutin against organisms with low MICs (< or = 1 mg/L), while rifabutin was more active than KRM-1648 against organisms with high MICs (> or = 2 mg/L). A total of 96 genetic alterations around the 69 bp core region of the rpoB gene were detected in 92 strains. Alterations at codons 515, 521 and 533 in the rpoB gene did not influence the susceptibility to rifampicin, rifabutin and KRM-1648. Point mutations at codons 516 and 529, deletion at codon 518 and insertion at codon 514 influenced the susceptibility to rifampicin but not that to rifabutin or KRM-1648. With the exception of one strain, all alterations at codon 513 and 531 correlated with resistance to the three test drugs. The resistant phenotype of strains with an alteration at codon 526 depended on the type of amino acid substitution. Our results suggest that analysis of genetic alterations in the rpoB gene might be useful not only for predicting rifampicin susceptibility, but also for deciding when to use rifabutin for treating tuberculosis. Further studies may be required to determine the usefulness of KRM-1648.

Topics: Amino Acid Sequence; Antibiotics, Antitubercular; Base Sequence; DNA-Directed RNA Polymerases; DNA, Bacterial; Drug Resistance, Microbial; Genes, Bacterial; Humans; Microbial Sensitivity Tests; Molecular Sequence Data; Mutation; Mycobacterium tuberculosis; Rifabutin; Rifampin; Rifamycins; Sequence Analysis, DNA; Tuberculosis

We evaluated the in vivo therapeutic activities of benzoxazinorifamycin KRM-1648, clarithromycin (CAM) and levofloxacin (LVFX) against Mycobacterium avium infection induced in mice. Mice infected intravenously with M. avium (1.4 x 10(7)) were given KRM-1648 (20 mg/kg), CAM (10 mg/kg), or LVFX (5 mg/kg) alone, or combination of KRM-1648 with diclofenac sodium (1.25 mg/kg) by gavage, once daily, five times per week, from day 1 for up to 8 weeks. The bacterial loads in the lungs and spleens were determined by counting colony forming units of the organisms in the tissue homogenates of the visceral organs using 7H11 agar plates. Both KRM-1648 and CAM caused significant levels of bacteriological response in mice treated with these drugs, while LVFX exerted no appreciable therapeutic effect. The therapeutic efficacies of test antimicrobials were in the order, KRM-1648 > CAM > > LVFX. The combined use of diclofenac sodium with KRM-1648 did not affect the expression of therapeutic activity of KRM-1648. This excludes the possibility that cyclooxygenase-dependent inflammatory reactions may be involved in the establishment of persistent bacterial growth of M. avium organisms at the sites of infection in mice. Furthermore, the present study showed that the parameters of in vitro antimicrobial activities of drugs such as MIC and MBC values are not useful in predicting their therapeutic outcome in M. avium-infected mice.

Topics: Animals; Anti-Bacterial Agents; Anti-Infective Agents; Anti-Inflammatory Agents, Non-Steroidal; Antibiotics, Antitubercular; Clarithromycin; Diclofenac; Drug Therapy, Combination; Female; Levofloxacin; Mice; Mice, Inbred BALB C; Mycobacterium avium; Ofloxacin; Rifamycins; Tuberculosis

To investigate the chemotherapeutic activity of benzoxazinorifamycin, KRM-1648, in comparison with rifabutin (RFB) and rifampin (RIF) against experimental tuberculosis.. C57BL/6 mice were infected with 10(5)-10(6) colony forming units (CFU) of either drug-susceptible virulent Mycobacterium tuberculosis (H37Rv) or multi-drug resistant (MDR) M. tuberculosis strain (2230) and were treated from the next day (early treatment) or after 2 weeks following infection (established infection) with 20 mg/kg dose of each drug or none (untreated control). The efficacy of chemotherapy was assessed based on prevention of mortality and on CFU levels in the lungs and spleens.. All three drugs prevented mortality for up to 28 weeks of observation, while all the untreated control mice died by 4 weeks. Analysis of CFUs revealed superior therapeutic activity of both KRM-1648 and RFB as compared to RIF against the drug-susceptible strain of M. tuberculosis under the early treatment protocol. Twelve weeks' treatment with KRM-1648 or RFB caused complete sterilization of the lungs. However, residual organisms started appearing in the spleens 6 weeks after cessation of treatment with RFB and 16 weeks after KRM-1648 treatment. In mice infected with a MDR strain of M. tuberculosis, which was susceptible in vitro to KRM-1648, the drug did not appear to have any activity. Since the MDR organisms did not multiply in vivo, and did not cause any mortality up to 28 weeks in the RIF-treated control mice, a state of semi-dormancy of the organisms which might prevail in vivo could be responsible for refractoriness to treatment with KRM-1648.. KRM-1648 showed an excellent chemotherapeutic activity, as compared to RFB and RIF, against drug-susceptible tuberculosis. However, all three analogues were ineffective against infection with multi-drug resistant strain of M. tuberculosis.

Topics: Animals; Antibiotics, Antitubercular; Colony Count, Microbial; Female; Lung; Male; Mice; Mice, Inbred C57BL; Mycobacterium tuberculosis; Rifabutin; Rifampin; Rifamycins; Spleen; Tuberculosis; Tuberculosis, Multidrug-Resistant

The activity of KRM-1648, alone and in combination with isoniazid, was compared with those of isoniazid, rifampin, and the combination of rifampin plus isoniazid in a murine model of tuberculosis. Four-week-old female CD-1 mice were infected intravenously with approximately 10(7) viable Mycobacterium tuberculosis ATCC 35801 organisms. Treatment was started 1 week postinfection and was given by gavage 5 days per week. The duration of the treatment phase was 12 weeks, with groups of mice sacrificed at 2, 4, 6, 8, and 12 weeks. For the observation phase, additional groups of treated mice were sacrificed at 4, 8, 16, and 24 weeks after the cessation of treatment. Viable cell counts were determined from homogenates of the spleens and the right lungs. KRM-1648 was the most active single agent evaluated and resulted in no detectable CFUs in the spleens and lungs by the end of 6 weeks of treatment. Neither rifampin nor isoniazid reduced cell counts to undetectable levels, even after 12 weeks of treatment. The combination of KRM-1648 plus isoniazid was much more active than rifampin plus isoniazid. KRM-1648 plus isoniazid resulted in the apparent sterilization of organs at 6 months following the cessation of treatment. The promising activity of KRM-1648 may allow for ultrashort-course therapy of tuberculosis, i.e., treatment regimens of 4 months or less.

Topics: Animals; Antibiotics, Antitubercular; Colony Count, Microbial; Drug Therapy, Combination; Female; Isoniazid; Lung; Mice; Mycobacterium tuberculosis; Rifampin; Rifamycins; Spleen; Time Factors; Tuberculosis

The in vitro and in vivo activities of a new rifamycin derivative, KRM-1648, against Mycobacterium tuberculosis H37Rv were compared with those of rifampin. Bactericidal activity was evaluated by using a silicone-coated slide culture method. The MBC of KRM-1648 was 0.15 to 0.3 microgram/ml for 24 h of exposure, while that of rifampin was > 160 microgram/ml under the same conditions. Against experimental murine tuberculosis, KRM-1648 exhibited significant therapeutic effects, in terms of prolonged survival times for mice compared with those with rifampin treatment, even at lower doses, such as 1 and 3 mg/kg. At a dose of 3 mg/kg, KRM-1648 was at least as effective as rifampin at 10 mg/kg. The combination of KRM-1648 (3 mg/kg) plus isoniazid (3 mg/kg) plus ethambutol (10 mg/kg) exhibited much more activity than did rifampin (10 mg/kg) plus isoniazid (3 mg/kg) plus ethambutol (10 mg/kg). These findings suggest that KRM-1648 is a promising candidate for the treatment of tuberculosis.

Topics: Animals; Antibiotics, Antitubercular; Antitubercular Agents; Dose-Response Relationship, Drug; Drug Combinations; Ethambutol; Isoniazid; Male; Mice; Microbial Sensitivity Tests; Mycobacterium tuberculosis; Rifampin; Rifamycins; Tuberculosis

The in vivo activities of KRM-1648 alone or in combination with both ethambutol (EB) and kanamycin (KM) or clarithromycin (CAM) were tested against Mycobacterium intracellulare infections in beige mice. KRM-1648 was more active than rifampin (RFP) when each drug was used alone, and the efficacy of KRM-1648 was similar to those of both kanamycin and clarithromycin. The combination KRM-1648-KM-EB was strongly active and rapidly reduced the numbers of bacilli both in lungs and in spleens compared with RFP-KM-EB. The combination KRM-1648-CAM had greater therapeutic effects than RFP-CAM; this difference in efficacy was more pronounced for lungs than for spleens. These findings suggest that KRM-1648 is a promising candidate for combination therapy with other potent antimycobacterial drugs.

Topics: Animals; Anti-Bacterial Agents; Antibiotics, Antitubercular; Antitubercular Agents; Clarithromycin; Colony Count, Microbial; Drug Combinations; Drug Therapy, Combination; Ethambutol; Female; Kanamycin; Lung; Male; Mice; Mycobacterium avium Complex; Rifampin; Rifamycins; Spleen; Tuberculosis

Although the MICs of 3'-hydroxy-5'-(4-isobutyl-1-piperazinyl)benzoxazinorifamycin, or KRM-1648 (KRM), for Mycobacterium avium complex (MAC) were significantly lower than those of other drugs, its in vivo activity was very weak. Beginning 28 days after inoculation, beige mice that had been infected intravenously with 1.87 x 10(7) CFU of MAC 101 were administered KRM alone, clarithromycin (CLARI) alone, or CLARI plus KRM six times weekly for 16 weeks. In contrast to the mice treated with CLARI-containing regimens, the mortality and the mean spleen weights of mice treated with KRM alone (either 10 or 20 mg/kg of body weight per dose) did not differ significantly from those of untreated mice, their numbers of CFU were very much greater than pretreatment values, and multiplication of MAC was only slightly inhibited. Although monotherapy by KRM selected KRM-resistant mutants, the selection was very weak; the mean number of CFU and the frequency of KRM-resistant mutants increased by no more than 1 order of magnitude after 16 weeks of treatment with KRM at 20 mg/kg per dose. Selection of CLARI-resistant mutants was inhibited but not completely prevented by treatment of the mice with CLARI plus KRM. These results indicate that KRM displayed only a weak bacteriostatic effect against the isolate tested in the beige mouse model; its ability to enhance the antimicrobial effect of CLARI or to prevent emergence of CLARI-resistant mutants was very limited.

Topics: Animals; Anti-Bacterial Agents; Antibiotics, Antitubercular; Clarithromycin; Drug Combinations; Drug Resistance, Microbial; Drug Therapy, Combination; Female; Kanamycin; Lung; Male; Mice; Microbial Sensitivity Tests; Mycobacterium avium Complex; Rifamycins; Spleen; Tuberculosis

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 vitro and in vivo activities of a new benzoxazinorifamycin, KRM-1648 (KRM), against Mycobacterium tuberculosis were studied. The MIC at which 50% of the isolates are inhibited (MIC50) and the MIC90 of KRM for 30 fresh isolates of M. tuberculosis measured by the BACTEC 460 TB System were 0.016 and 2 micrograms/ml, respectively. These values were much lower than those for rifampin (RMP), which were 4 and >128 micrograms/ml, respectively, and considerably lower than those for rifabutin (RBT), which were 0.125 and 8 micrograms/ml, respectively. A correlational analysis of the MICs of these drugs for the clinical isolates revealed the presence of cross-resistance of the organisms to KRM and either RMP or RBT although the MICs of KRM were distributed over a much lower range than were those of the other two drugs. KRM and RMP at concentrations of 1 to 10 micrograms/ml almost completely inhibited the bacterial growth of RMP-sensitive strains (H37Rv, Kurono, and Fujii) of M. tuberculosis phagocytosed in macrophage-derived J774.1 cells. KRM was more active than RMP in inhibiting the growth of the RMP-resistant (MIC = 8 micrograms/ml) Kurata strain but failed to show such an effect against the RMP-resistant (MIC >128 micrograms/ml) Watanabe stain. When KRM was given to M. tuberculosis-infected mice at dosages of 5 to 20 mg/kg of body weight by gavage, one daily six times per week from day 1 after infection, it was much more efficacious than RMP against infections induced in mice by the RMP-sensitive Kurono strain, as measured by a reduction of rates of mortality, a reduction of the frequency and extent of gross lung lesions, histopathological changes in lung tissues, and a decrease in the bacterial loads in the lungs and spleens of infected mice. KRM also displayed significant therapeutic efficacy against infection induced by the RMP-resistant Kurata strain, while neither KRM nor RMP was efficacious against infection by the RMP-resistant Watanabe strain. In the case of infection with the Kurono strain, the efficacy of the drugs in prolonging the time of survival was in the order KRM, RBT, RMP. KRM was much more efficacious than RMP, when given at 1- to 4-week intervals. These findings suggest that KRM may be useful for the clinical treatment of tuberculosis contracted through RMP-sensitive strains, even when it is administered at long intervals.

Topics: Animals; Antibiotics, Antitubercular; Drug Resistance, Microbial; Female; Lung; Mice; Mice, Inbred BALB C; Microbial Sensitivity Tests; Mycobacterium tuberculosis; Rifampin; Rifamycins; Tuberculosis

Because of the recent AIDS endemic, there is a worldwide increase in intractable mycobacterial infections including extrapulmonary tuberculosis due to multidrug-resistant M. tuberculosis and disseminated M. avium complex (MAC) infections. Therefore, development of new anti-tuberculous drugs having an excellent antimycobacterial activity and protocols for clinical use of presently available antimicrobials are urgently desired. In this study, we performed in vitro and in vivo experiments to assess the chemotherapeutic efficacy of a newly synthesized benzoxazinorifamycin derivative, KRM-1648 (KRM), against experimental infections due to MAC and M. tuberculosis. In addition, we attempted to improve the therapeutic efficacy of the KRM against MAC infections by changing its administration protocols and timing or by combined use with other antimicrobials, including clarithromycin (CAM), clofazimine (CFZ), sparfloxacin (SPFX), streptomycin (SM), and ethambutol (EB). Furthermore, we examined therapeutic efficacy of KRM against rifampicin (RFP)-resistant M. tuberculosis in details. KRM showing much more potent in vitro activity against the MAC organisms compared to rifabutin (RBT) and RFP, also exerted markedly greater therapeutic efficacy against the MAC infections induced in mice or rabbits in terms of reducing the incidence and the extent of gross pulmonary lesions and the bacterial loads in the lungs and spleens. However, in the case of mouse experimental infections, regrowth of the organisms was initiated after week 4 to 6 even in the animals given KRM. Since KRM-resistant organisms could not be isolated from infected mice given continuous KRM administrations, some unknown mechanisms other than the acquisition of drug resistance by infected organisms may be important for the establishment of the regrowth of MAC organisms.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Animals; Antibiotics, Antitubercular; Antitubercular Agents; Drug Therapy, Combination; Mice; Microbial Sensitivity Tests; Mycobacterium avium; Mycobacterium tuberculosis; Rifamycins; Tuberculosis

The activity of KRM-1648 was evaluated in a murine model of tuberculosis. Approximately 10(7) viable Mycobacterium tuberculosis ATCC 35801 organisms were given intravenously to 4-week-old female outbred mice. Treatment was started 1 week postinfection and given by gavage for 4 weeks. Viable-cell counts were determined from homogenates of spleen and lung tissues. The activity of KRM-1648 was compared with those of rifampin and rifabutin at 20 mg/kg of body weight. KRM-1648 was more active than either rifampin or rifabutin against organisms in spleens and lungs. KRM-1648 alone and in combination with either isoniazid, ethambutol, pyrazinamide, or levofloxacin was evaluated. Other treatment groups received isoniazid, ethambutol, pyrazinamide, or levofloxacin as single agents. KRM-1648 was the most active single agent evaluated. KRM-1648-pyrazinamide and KRM-1648-isoniazid were the most active combinations. These combinations were more active than KRM-1648 alone. The promising activity of KRM-1648 in M. tuberculosis-infected mice suggests that it is a good candidate for clinical development as a new antituberculosis agent.

Topics: Animals; Antibiotics, Antitubercular; Drug Therapy, Combination; Female; Isoniazid; Mice; Pyrazinamide; Rifabutin; Rifampin; Rifamycins; Tuberculosis

Rifamycins are active against slowly growing mycobacteria, such as Mycobacterium tuberculosis and Mycobacterium kansasii, but the majority of rifamycins thus far investigated both in vitro and in vivo are inactive or have only modest activity against the Mycobacterium avium complex (MAC). We investigated the activity of three doses of the semisynthetic benzoxazinorifamycin KRM 1648, alone or in combination with ethambutol or clarithromycin, in beige mice challenged with the MAC strain 101. Our results show the following. (i) KRM 1648 was significantly effective against MAC infection as determined by the reduction of the number of bacteria in the blood, liver, and spleen when administered at doses of 20 and 40 mg/kg of body weight per day but not at 10 mg/kg/day, compared with untreated controls. (ii) KRM 1648 (40 mg/kg/day) administered in combination with ethambutol (100 mg/kg/day) resulted in significant reduction in bacteremia compared with values for untreated controls (P 0.001), KRM 1648 alone (P = 0.019), and ethambutol alone (P = 0.003). Furthermore, the combination of KRM 1648 and ethambutol was associated with a significant decrease of the number of bacteria in the spleen and the liver compared with values for both untreated controls and each drug alone (P < 0.001 for all comparisons). (iii) KRM 1648 (40 mg/kg/day) administered in combination with clarithromycin (200 mg/kg/day) resulted in a significant decrease of the number of bacteria in the blood and the spleen compared with the number for untreated controls (P < 0.001 for all comparisons). In our experience, using MAC 101 as the challenging organism, KRM 1648 is the first the number of bacteria in the blood and spleen compared with the number for untreated controls (P >0.001 for all comparions). In our experience, using MAC 101 as the challenging organism, KRM 1648 is the first rifamycin with significant activity in vivo against MAC infection in beige mice.

Topics: Animals; Antibiotics, Antitubercular; Clarithromycin; Dose-Response Relationship, Drug; Drug Therapy, Combination; Ethambutol; Female; Mice; Mice, Inbred C57BL; Mycobacterium avium; Rifamycins; Tuberculosis

Therapeutic efficacy of KRM-1648 was studied in BALB/c mice infected with Mycobacterium intracellulare. Mice were infected intravenously with 1.0 x 10(7) CFU of the organisms/mouse and then given 0.2 mg or 0.4 mg of KRM-1648 emulsified in 2.5% gum arabic-0.2% Tween 80 by gavage, once daily, 6 days per week, from day 1 to the death of mice. The therapeutic efficacy of the drug was evaluated on the basis of survival times, incidence and degree of gross lung lesions and bacterial loads in the lungs and spleen. The lung lesions were not observed in any experimental groups at 4 weeks after the infection. At 8 weeks after the infection, the lung lesions were observed in all control mice, but 2 of 5 mice treated with 0.2 mg of KRM and 4 of 5 mice treated with 0.4 mg of KRM did not show any lung lesions, and the degree of the lesions was much milder in KRM-1648-treated mice than in the control mice. All mice of treated and untreated groups died, and median survival times were 141 days for the control mice, 216 days for mice treated with 0.2 mg of KRM-1648 and 220 days for mice treated with 0.4 mg of KRM-1648. At the death, lung lesions were observed in all mice. The CFUs of M. intracellulare in the lungs and spleen in mice treated with KRM-1648 were fewer than those in the control mice at 4 and 8 weeks after the infection.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Animals; Antibiotics, Antitubercular; Female; Mice; Mice, Inbred BALB C; Mycobacterium avium; Rifamycins; Tuberculosis

Therapeutic efficacy of a newly synthesized benzoxazinorifamycin, KRM-1648, administered at the different periods of infection in Mycobacterium intracellulare-infected mice was studied. Mice were infected intravenously with M. intracellulare (9.8 x 10(6) CFU/mouse) and then were given 0.4 mg of KRM-1648 emulsified in 2.5% gum arabic-0.2% Tween 80 by gavage, once daily six times per week, from day 1 to week 4, week 2 to week 6, week 4 to week 8, and week 8 to the end of experiment (week 12). Judgement of the therapeutic efficacy of the drug against the infection was done on the basis of incidence and degree of gross lung lesions, % organ weight (organ weight/body weight x 100), and bacterial loads in the lungs and spleen. The lung lesions were not observed in the control and KRM-treated mice at 4 weeks after infection (KRM treatment: day 1 to week 4). At 6 weeks after infection (KRM treatment: week 2 to week 6), the lung lesions were observed in all control mice, whereas 3 of the 5 mice given KRM-1648 did not show the lesions. At 8 weeks after infection (KRM treatment: week 4 to week 8), the lung lesions were observed in all control and KRM-1648-treated mice, but the degree of the lung lesions was much more slight in mice given KRM-1648 than in control mice. The incidence and the degree of the lung lesions at 12 weeks after infection (KRM treatment: week 8 to week 12) was not different in both groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Animals; Antibiotics, Antitubercular; Female; Mice; Mice, Inbred BALB C; Mycobacterium avium; Rifamycins; Time Factors; Tuberculosis

A study was performed on the therapeutic efficacy of KRM-1648 combined with LC9018 in beige mice infected with Mycobacterium intracellulare. Each mouse was intravenously infected with 3.9 x 10(6) CFU, and then given 0.2 mg of KRM-1648 emulsified in 2.5% gum arabic-0.2% Tween 80 by gavage once a day, six times per week, beginning 24 h after infection for up to eight weeks. A sc injection of 0.1 mg LC9018 in saline was given once or twice per week, beginning two weeks before infection to the end of experiment. An evaluation of the therapeutic efficacy of these drugs against the infection was performed on the basis of incidence and degree of gross lung lesions and bacterial loads in the lungs and spleen. Lung lesions were not observed in all experimental groups at four weeks after infection. However, at eight weeks after infection, although lung lesions were observed in all experimental groups, the degree of lesions was much milder in those mice receiving KRM-1648 than in the control mice. The degree of lesions in the mice receiving LC9018 was much the same as that in the control mice. Moreover, the degree of lung lesions in mice treated with KRM-1648 alone. The CFUs of organisms in the lungs and spleen of the mice treated with KRM-1648 were considerably lower than those of the control mice (P < 0.05), but the CFUs in the mice treated with KRM-1648 and LC9018 were nearly the same as those mice treated with KRM-1648.

Topics: Adjuvants, Immunologic; Animals; Antibiotics, Antitubercular; Drug Therapy, Combination; Female; Lacticaseibacillus casei; Mice; Mice, Inbred C57BL; Mycobacterium avium; Rifamycins; Tuberculosis