Targeting the Mycobacterium ulcerans cytochrome bc1:aa3 for the treatment of Buruli ulcer

Mycobacterium ulcerans is the causative agent of Buruli ulcer, a neglected tropical skin disease that is most commonly found in children from West and Central Africa. Despite the severity of the infection, therapeutic options are limited to antibiotics with severe side effects. Here, we show that M. ulcerans is susceptible to the anti-tubercular drug Q203 and related compounds targeting the respiratory cytochrome bc; 1; :aa; 3; . While the cytochrome bc; 1; :aa; 3; is the primary terminal oxidase in Mycobacterium tuberculosis, the presence of an alternate bd-type terminal oxidase limits the bactericidal and sterilizing potency of Q203 against this bacterium. M. ulcerans strains found in Buruli ulcer patients from Africa and Australia lost all alternate terminal electron acceptors and rely exclusively on the cytochrome bc; 1; :aa; 3; to respire. As a result, Q203 is bactericidal at low dose against M. ulcerans replicating in vitro and in mice, making the drug a promising candidate for Buruli ulcer treatment

Bactericidal Activities of R207910 and Other Newer Antimicrobial Agents against Mycobacterium leprae in Mice

As measured by a proportional bactericidal technique in the mouse footpad system, the bactericidal activity against Mycobacterium leprae of R207910 was equal to that of rifapentine, rifampin, or moxifloxacin and significantly greater than those of minocycline, PA-824, and linezolid. These data suggest that R207910 may play an important role in treatment of leprosy

Bactericidal and Sterilizing Activities of Several Orally Administered Combined Regimens against Mycobacterium ulcerans in Mice ▿

Treatment with rifampin-clarithromycin or moxifloxacin-clarithromycin for 8 weeks displayed promising bactericidal activity against Mycobacterium ulcerans in mice; none of the mice treated with rifampin-clarithromycin relapsed, whereas 59% of those treated with moxifloxacin-clarithromycin relapsed after treatment was stopped. The bactericidal and sterilizing activities of the five-times-weekly (5/7) administration of 5 mg of rifapentine/kg of body weight, either alone or in combination, were virtually identical to those of the corresponding regimens with 10 mg of rifampin/kg of body weight; however, because of the long half-life of rifapentine, accumulation of the drug after 5/7 administration is a concern. The bactericidal activity of 20 mg/kg rifapentine in monotherapy or 20 mg/kg rifapentine in combination with 150 mg/kg streptomycin or 200 mg/kg moxifloxacin administered twice weekly was as effective as the corresponding regimens containing 10 mg/kg rifampin administered 5/7, suggesting that Buruli ulcer might be treated with intermittently administered rifapentine-containing combinations

Curing Mycobacterium ulcerans Infection in Mice with a Combination of Rifampin-Streptomycin or Rifampin-Amikacin

The curing activities of various durations of treatment with a combination of rifampin (RIF) and either streptomycin (STR) or amikacin (AMK) in murine Mycobacterium ulcerans infection were compared in two experiments. In the first experiment, treatment was begun 1 week after infection, when the inflammatory footpad lesion had not yet occurred (preventive model), and in the second experiment, treatment was begun 6 weeks after infection, when inflammatory footpad lesions were established (curative model). In the first experiment, 4 weeks of treatment with daily RIF-STR or RIF-AMK was able to postpone the occurrence of footpad lesion by 12 weeks (RIF-STR) or 17 weeks (RIF-AMK), thus demonstrating their promising bactericidal activities, but neither treatment was able to prevent the late occurrence of footpad lesions. In the second experiment, the overall cure rates, as assessed by the lack of rebound of inflammatory lesions or remultiplication of M. ulcerans, were only 62% after 2 weeks of treatment with RIF and an aminoglycoside and 85% after 4 weeks; but the cure rate reached 100% after 8 or 12 weeks of treatment. The cure rates were slightly higher with the AMK-containing combination than with the STR-containing combination, but the difference was at the limit of significance (P = 0.07). These results show that in the murine model of Buruli ulcer, 8 weeks is the optimal duration of treatment with a combination of RIF and an aminoglycoside

Sterilizing Activity of Fully Oral Intermittent Regimens against Mycobacterium Ulcerans Infection in Mice.

The treatment of Buruli ulcer (BU) that is caused by Mycobacterium ulcerans, is currently based on a daily administration of rifampin and streptomycin (RIF-STR). A fully oral intermittent regimen would greatly simplify its treatment on the field.The objective of this study was to assess the bactericidal and sterilizing activities of intermittent oral regimens in a murine model of established M. ulcerans infection. Regimens combining rifapentine (RFP 20 mg/kg) with either moxifloxacin (MXF 200 mg/kg), clarithromycin (CLR 100 mg/kg) or bedaquiline (BDQ 25 mg/kg) were administrated twice (2/7) or three (only for RFP-CLR 3/7) times weekly during 8 weeks. The bactericidal but also the sterilizing activities of these four intermittent oral regimens were at least as good as those obtained with control weekdays regimens, i.e. RFP-CLR 5/7 or RIF-STR 5/7. A single mouse from the RFP-MFX 2/7 group had culture-positive relapse at the end of the 28 weeks following treatment completion among the 157 mice treated with one of the four intermittent regimens (40 RFP-CLR 2/7, 39 RFP-CLR 3/7, 39 RFP-MXF 2/7, 39 RFP-BDQ 2/7).These results open the door for a fully intermittent oral drug regimen for BU treatment avoiding intramuscular injections and facilitating supervision by health care workers

Orally Administered Combined Regimens for Treatment of Mycobacterium ulcerans Infection in Mice▿

Eight weeks of treatment with rifampin-streptomycin sterilizes Mycobacterium ulcerans infection in mice. Because the bactericidal activity against M. ulcerans of the combination rifampin-moxifloxacin, rifampin-clarithromycin, or moxifloxacin-clarithromycin was similar to that of rifampin-streptomycin, these combinations might be considered as alternative, orally administered combined regimens for treatment of Buruli ulcer in humans

Telacebec (Q203)-containing intermittent oral regimens sterilized mice infected with Mycobacterium ulcerans after only 16 doses

International audienceBuruli ulcer (BU), caused by Mycobacterium ulcerans, is currently treated with a daily combination of rifampin and either injectable streptomycin or oral clarithromycin. An intermittent oral regimen would facilitate treatment supervision. We first evaluated the bactericidal activity of newer antimicrobials against M. ulcerans using a BU animal model. The imidazopyridine amine telacebec (Q203) exhibited high bactericidal activity whereas tedizolid (an oxazolidinone closely related to linezolid), selamectin and ivermectin (two avermectine compounds) and the benzothiazinone PBTZ169 were not active. Consequently, telacebec was evaluated for its bactericidal and sterilizing activities in combined intermittent regimens. Telacebec given twice a week in combination with a long-half-life compound, either rifapentine or bedaquiline, sterilized mouse footpads in 8 weeks, i.e. after a total of only 16 doses, and prevented relapse during a period of 20 weeks after the end of treatment. These results are very promising for future intermittent oral regimens which would greatly simplify BU treatment in the field

Minimal effective dose of bedaquiline administered orally and activity of a long acting formulation of bedaquiline in the murine model of leprosy.

BackgroundBedaquiline (BDQ), by targeting the electron transport chain and having a long half-life, is a good candidate to simplify leprosy treatment. Our objectives were to (i) determine the minimal effective dose (MED) of BDQ administered orally, (ii) evaluate the benefit of combining two inhibitors of the respiratory chain, BDQ administered orally and clofazimine (CFZ)) and (iii) evaluate the benefit of an intramuscular injectable long-acting formulation of BDQ (intramuscular BDQ, BDQ-LA IM), in a murine model of leprosy.Methodology/principal findingsTo determine the MED of BDQ administered orally and the benefit of adding CFZ, 100 four-week-old female nude mice were inoculated in the footpads with 5x103 bacilli of M. leprae strain THAI53. Mice were randomly allocated into: 1 untreated group, 5 groups treated with BDQ administered orally (0.10 to 25 mg/kg), 3 groups treated with CFZ 20 mg/kg alone or combined with BDQ administered orally 0.10 or 0.33 mg/kg, and 1 group treated with rifampicin (RIF) 10 mg/kg. Mice were treated 5 days a week during 24 weeks. To evaluate the benefit of the BDQ-LA IM, 340 four-week-old female swiss mice were inoculated in the footpads with 5x103 to 5x101 bacilli (or 5x100 for the untreated control group) of M. leprae strain THAI53. Mice were randomly allocated into the following 11 groups treated with a single dose (SD) or 3 doses (3D) 24h after the inoculation: 1 untreated group, 2 treated with RIF 10 mg/kg SD or 3D, 8 treated with BDQ administered orally or BDQ-LA IM 2 or 20 mg/kg, SD or 3D. Twelve months later, mice were sacrificed and M. leprae bacilli enumerated in the footpad. All the footpads became negative with BDQ at 3.3 mg/kg. The MED of BDQ administered orally against M. leprae in this model is therefore 3.3 mg/kg. The combination of CFZ and BDQ 10-fold lower than this MED did not significantly increase the bactericidal activity of CFZ. The BDQ-LA IM displayed similar or lower bactericidal activity than the BDQ administered orally.ConclusionWe demonstrated that the MED of BDQ administered orally against M. leprae was 3.3 mg/kg in mice and BDQ did not add significantly to the efficacy of CFZ at the doses tested. BDQ-LA IM was similar or less active than BDQ administered orally at equivalent dosing and frequency but should be tested at higher dosing in order to reach equivalent exposure in further experiments

In Vitro and In Vivo Activities of Rifampin, Streptomycin, Amikacin, Moxifloxacin, R207910, Linezolid, and PA-824 against Mycobacterium ulcerans

Seven antimicrobials were tested in vitro against 29 clinical isolates of Mycobacterium ulcerans. R207910 demonstrated the lowest MIC(50) and MIC(90), followed by moxifloxacin (MXF), streptomycin (STR), rifampin (RIF), amikacin (AMK), linezolid (LZD), and PA-824. All but PA-824 demonstrated an MIC(90) significantly less than the clinically achievable peak serum level. Administered as monotherapy to mice, RIF, STR, AMK, MXF, R207910, and LZD demonstrated some degree of bactericidal activity, whereas PA-824 failed to prevent mortality and to reduce the mean number of CFU in the footpads. Because 4 or 8 weeks of treatment by the combinations RIF-MXF, RIF-R207910, and RIF-LZD displayed bactericidal effects similar to those of RIF-STR and RIF-AMK, these three combinations might be considered as orally administered combined regimens for treatment of Buruli ulcer. Taking into account the cost, potential toxicity, and availability, the combination RIF-MXF appears more feasible for application in the field; additional experiments with mice are warranted to define further its activity against M. ulcerans. In addition, a pilot clinical trial is proposed to test the efficacy of RIF-MXF for treatment of Buruli ulcer