opc-67683 and Disease-Models--Animal

A recent landmark trial showed a 4-month regimen of rifapentine, pyrazinamide, moxifloxacin, and isoniazid (PZMH) to be noninferior to the 6-month standard of care. Here, two murine models of tuberculosis were used to test whether novel regimens replacing rifapentine and isoniazid with bedaquiline and another drug would maintain or increase the sterilizing activity of the regimen. In BALB/c mice, replacing rifapentine in the PZM backbone with bedaquiline (i.e., BZM) significantly reduced both lung CFU counts after 1 month and the proportion of mice relapsing within 3 months after completing 1.5 months of treatment. The addition of rifabutin to BZM (BZMRb) further increased the sterilizing activity. In the C3HeB/FeJ mouse model characterized by caseating lung lesions, treatment with BZMRb resulted in significantly fewer relapses than PZMH after 2 months of treatment. A regimen combining the new DprE1 inhibitor OPC-167832 and delamanid (BZOD) also had superior bactericidal and sterilizing activity compared to PZM in BALB/c mice and was similar in efficacy to PZMH in C3HeB/FeJ mice. Thus, BZM represents a promising backbone for treatment-shortening regimens. Given the prohibitive drug-drug interactions between bedaquiline and rifampin or rifapentine, the BZMRb regimen represents the best opportunity to combine, in one regimen, the treatment-shortening potential of the rifamycin class with that of BZM and deserves high priority for evaluation in clinical trials. Other 4-drug BZM-based regimens and BZOD represent promising opportunities for extending the spectrum of treatment-shortening regimens to rifamycin- and fluoroquinolone-resistant tuberculosis.

Topics: Animals; Antibiotics, Antitubercular; Antitubercular Agents; Diarylquinolines; Disease Models, Animal; Drug Administration Schedule; Drug Therapy, Combination; Isoniazid; Mice; Mice, Inbred BALB C; Moxifloxacin; Mycobacterium tuberculosis; Nitroimidazoles; Oxazoles; Pyrazinamide; Rifabutin; Tuberculosis

The treatment success rate of drug-resistant (DR) tuberculosis is alarmingly low. Therefore, more effective and less complex regimens are urgently required.. We compared the efficacy of an all oral DR tuberculosis drug regimen consisting of bedaquiline (25 mg/kg), delamanid (2.5 mg/kg), and linezolid (100 mg/kg) (BDL) on the mycobacterial load in the lungs and spleen of tuberculosis-infected mice during a treatment period of 24 weeks. This treatment was compared with the standard regimen of isoniazid, rifampicin, pyrazinamide, and ethambutol (HRZE). Relapse was assessed 12 weeks after treatment. Two logistic regression models were developed to compare the efficacy of both regimens.. Culture negativity in the lungs was achieved at 8 and 20 weeks of treatment with BDL and HRZE, respectively. After 14 weeks of treatment only 1 mouse had relapse in the BDL group, while in the HRZE group relapse was still observed at 24 weeks of treatment. Predictions from the final mathematical models showed that a 95% cure rate was reached after 20.5 and 28.5 weeks of treatment with BDL and HRZE, respectively.. The BDL regimen was observed to be more effective than HRZE and could be a valuable option for the treatment of DR tuberculosis.

Topics: Animals; Antitubercular Agents; Diarylquinolines; Disease Models, Animal; Drug Therapy, Combination; Linezolid; Mice; Mycobacterium tuberculosis; Nitroimidazoles; Oxazoles; Pyrazinamide; Recurrence; Tuberculosis

As part of a quest for backups to the antitubercular drug pretomanid (PA-824), we investigated the unexplored 6-nitro-2,3-dihydroimidazo[2,1-b][1,3]-thiazoles and related -oxazoles. The nitroimidazothiazoles were prepared in high yield from 2-bromo-4-nitroimidazole via heating with substituted thiiranes and diisopropylethylamine. Equivalent examples of these two structural classes provided broadly comparable MICs, with 2-methyl substitution and extended aryloxymethyl side chains preferred; albeit, S-oxidised thiazoles were ineffective for tuberculosis. Favourable microsomal stability data for a biaryl thiazole (45) led to its assessment in an acute Mycobacterium tuberculosis mouse model, alongside the corresponding oxazole (48), but the latter proved to be more efficacious. In vitro screening against kinetoplastid diseases revealed that nitroimidazothiazoles were inactive versus leishmaniasis but showed interesting activity, superior to that of the nitroimidazooxazoles, against Chagas disease. Overall, "thio-delamanid" (49) is regarded as the best lead.

Topics: Animals; Antitubercular Agents; Chagas Disease; Disease Models, Animal; Mice; Microbial Sensitivity Tests; Mycobacterium tuberculosis; Nitroimidazoles; Oxazoles; Structure-Activity Relationship; Thiazoles; Tuberculosis

There is an urgent requirement for safe, oral and cost-effective drugs for the treatment of visceral leishmaniasis (VL). We report that delamanid (OPC-67683), an approved drug for multi-drug resistant tuberculosis, is a potent inhibitor of Leishmania donovani both in vitro and in vivo. Twice-daily oral dosing of delamanid at 30 mg kg(-1) for 5 days resulted in sterile cures in a mouse model of VL. Treatment with lower doses revealed a U-shaped (hormetic) dose-response curve with greater parasite suppression at 1 mg kg(-1) than at 3 mg kg(-1) (5 or 10 day dosing). Dosing delamanid for 10 days confirmed the hormetic dose-response and improved the efficacy at all doses investigated. Mechanistic studies reveal that delamanid is rapidly metabolised by parasites via an enzyme, distinct from the nitroreductase that activates fexinidazole. Delamanid has the potential to be repurposed as a much-needed oral therapy for VL.

Topics: Administration, Oral; Animals; Antiprotozoal Agents; Antitubercular Agents; Biotransformation; Disease Models, Animal; Drug Administration Schedule; Drug Dosage Calculations; Drug Repositioning; Female; Hormesis; Leishmania donovani; Leishmaniasis, Visceral; Mice; Mice, Inbred BALB C; Nitroimidazoles; Oxazoles; Parasitic Sensitivity Tests; Treatment Outcome

Nitroimidazoles are a promising new class of antitubercular agents. The nitroimidazo-oxazole delamanid (OPC-67683, Deltyba) is in phase III trials for the treatment of multidrug-resistant tuberculosis, while the nitroimidazo-oxazine PA-824 is entering phase III for drug-sensitive and drug-resistant tuberculosis. TBA-354 (SN31354[(S)-2-nitro-6-((6-(4-trifluoromethoxy)phenyl)pyridine-3-yl)methoxy)-6,7-dihydro-5H-imidazo[2,1-b][1,3]oxazine]) is a pyridine-containing biaryl compound with exceptional efficacy against chronic murine tuberculosis and favorable bioavailability in preliminary rodent studies. It was selected as a potential next-generation antituberculosis nitroimidazole following an extensive medicinal chemistry effort. Here, we further evaluate the pharmacokinetic properties and activity of TBA-354 against Mycobacterium tuberculosis. TBA-354 is narrow spectrum and bactericidal in vitro against replicating and nonreplicating Mycobacterium tuberculosis, with potency similar to that of delamanid and greater than that of PA-824. The addition of serum protein or albumin does not significantly alter this activity. TBA-354 maintains activity against Mycobacterium tuberculosis H37Rv isogenic monoresistant strains and clinical drug-sensitive and drug-resistant isolates. Spontaneous resistant mutants appear at a frequency of 3 × 10(-7). In vitro studies and in vivo studies in mice confirm that TBA-354 has high bioavailability and a long elimination half-life. In vitro studies suggest a low risk of drug-drug interactions. Low-dose aerosol infection models of acute and chronic murine tuberculosis reveal time- and dose-dependent in vivo bactericidal activity that is at least as potent as that of delamanid and more potent than that of PA-824. Its superior potency and pharmacokinetic profile that predicts suitability for once-daily oral dosing suggest that TBA-354 be studied further for its potential as a next-generation nitroimidazole.

Topics: Animals; Antitubercular Agents; Caco-2 Cells; Cell Line, Tumor; Disease Models, Animal; Drug Interactions; Drug Resistance, Bacterial; Female; Humans; Mice; Mice, Inbred BALB C; Microbial Sensitivity Tests; Mycobacterium tuberculosis; Nitroimidazoles; Oxazines; Oxazoles; Tuberculosis

New regimens based on two or more novel agents are sought in order to shorten or simplify the treatment of both drug-susceptible and drug-resistant forms of tuberculosis. PA-824 is a nitroimidazo-oxazine now in phase II trials and has shown significant early bactericidal activity alone and in combination with the newly approved agent bedaquiline or with pyrazinamide with or without moxifloxacin. While the development of PA-824 continues, a potential next-generation derivative, TBA-354, has been discovered to have in vitro potency superior to that of PA-824 and greater metabolic stability than that of the other nitroimidazole derivative in clinical development, delamanid. In the present study, we compared the activities of PA-824 and TBA-354 as monotherapies in murine models of the initial intensive and continuation phases of treatment, as well as in combination with bedaquiline plus pyrazinamide, sutezolid, and/or clofazimine. The monotherapy studies demonstrated that TBA-354 is 5 to 10 times more potent than PA-824, but selected mutants are cross-resistant to PA-824 and delamanid. The combination studies revealed that TBA-354 is 2 to 4 times more potent than PA-824 when combined with bedaquiline, and when administered at a dose equivalent to that of PA-824, TBA-354 demonstrated superior sterilizing efficacy. Perhaps most importantly, the addition of either nitroimidazole significantly improved the sterilizing activities of bedaquiline and sutezolid, with or without pyrazinamide, confirming the value of each agent in this potentially universally active short-course regimen.

Topics: Animals; Antitubercular Agents; Clofazimine; Diarylquinolines; Disease Models, Animal; Drug Therapy, Combination; Female; Fluoroquinolones; Mice; Mice, Inbred BALB C; Microbial Sensitivity Tests; Moxifloxacin; Mycobacterium tuberculosis; Nitroimidazoles; Oxazines; Oxazoles; Pyrazinamide; Random Allocation; Tuberculosis

Novel extended side chain nitroimidazooxazine analogues featuring diverse linker groups between two aryl rings were studied as a potential strategy to improve solubility and oral activity against chronic infection by Mycobacterium tuberculosis. Both lipophilic and highly polar functionalities (e.g., carboxamide, alkylamine, piperazine, piperidine, but not sulfonamide) were well tolerated in vitro, and the hydrophilic linkers provided some solubility improvements, particularly in combination with pyridine rings. Most of the 18 compounds further assessed showed high microsomal stabilities, although in the acute infection mouse model, just one stilbene (6-fold) and two pyridine-containing acetylene derivatives (5-fold and >933-fold) gave in vivo efficacies notably superior to the clinical stage compound pretomanid (PA-824). The most efficacious analogue also displayed outstanding in vivo activity in the stringent chronic model (up to 24-fold better than the drug delamanid and 4-fold greater than our previous best phenylpyridine candidate), with favorable pharmacokinetics, including good oral bioavailability in the rat.

Topics: Administration, Oral; Animals; Antitubercular Agents; Biological Availability; Chemistry Techniques, Synthetic; Chronic Disease; Disease Models, Animal; Humans; Male; Mice, Inbred BALB C; Mice, Inbred Strains; Microbial Sensitivity Tests; Microsomes, Liver; Mycobacterium tuberculosis; Nitroimidazoles; Oxazoles; Rats, Sprague-Dawley; Structure-Activity Relationship; Tuberculosis

New heterocyclic analogues of the potent biphenyl class derived from antitubercular drug PA-824 were prepared, aiming to improve aqueous solubility but maintain high metabolic stability and efficacy. The strategy involved replacement of one or both phenyl groups by pyridine, pyridazine, pyrazine, or pyrimidine, in order to reduce lipophilicity. For para-linked biaryls, hydrophilicities (ClogP) correlated with measured solubilities, but highly soluble bipyridine analogues displayed weak antitubercular activities. A terminal pyridine or proximal heterocycle allowed retention of potency and provided solubility improvements, particularly at low pH, with examples from the latter classes displaying the better in vivo efficacies, high metabolic stabilities, and excellent pharmacokinetics. Five such compounds were >100-fold better than the parent drug in a mouse model of acute Mycobacterium tuberculosis infection, and two orally bioavailable pyridine analogues (3-4-fold more soluble than the parent at low pH) were superior to antitubercular drug OPC-67683 in a chronic infection model.

Topics: Animals; Antitubercular Agents; Disease Models, Animal; Magnetic Resonance Spectroscopy; Male; Mice; Mice, Inbred BALB C; Nitroimidazoles; Oxazines; Rats; Rats, Sprague-Dawley; Structure-Activity Relationship; Tuberculosis