New Approach to Drug Discovery of a Safe Mitochondrial Uncoupler: OPC-163493.

We serendipitously found a mitochondrial uncoupler (mUncoupler), compound 1, in the process of screening for inhibitors of a gene product related to calorie restriction (CR) and longevity. Compound 1 has a unique 4-cyano-1,2,3-triazole structure which is different from any known mUncoupler and ameliorated HbA1c in Zucker diabetic fatty (ZDF) rats. However, its administration at high doses was not tolerated in an acute toxicity test in rats. We therefore tried to optimize cyanotriazole compound 1 and convert it into an agent that could be safely administered to patients with diabetes mellitus (DM) or metabolic disorders. Considering pharmacokinetic (PK) profiles, especially organ distribution targeting the liver and avoiding the brain, as well as acute toxicities and pharmacological effects of the derivatives, various conversions and substitutions at the 5-position on the cyanotriazole ring were carried out. These optimizing processes improved PK profiles and effectiveness, and acute toxicities became negligible even at high doses. We finally succeeded in developing an optimized compound, OPC-163493, as a liver-localized/targeted mUncoupler.

OPC-167832, a Novel Carbostyril Derivative with Potent Antituberculosis Activity as a DprE1 Inhibitor.

There is an urgent need for new, potent antituberculosis (anti-TB) drugs with novel mechanisms of action that can be included in new regimens to shorten the treatment period for TB. After screening a library of carbostyrils, we optimized 3,4-dihydrocarbostyril derivatives and identified OPC-167832 as having potent antituberculosis activity. The MICs of the compound for Mycobacterium tuberculosis ranged from 0.00024 to 0.002 µg/ml. It had bactericidal activity against both growing and intracellular bacilli, and the frequency of spontaneous resistance for M. tuberculosis H37Rv was less than 1.91 × 10-7 It did not show antagonistic effects with other anti-TB agents in an in vitro checkerboard assay. Whole-genome and targeted sequencing of isolates resistant to OPC-167832 identified decaprenylphosphoryl-ß-d-ribose 2'-oxidase (DprE1), an essential enzyme for cell wall biosynthesis, as the target of the compound, and further studies demonstrated inhibition of DprE1 enzymatic activity by OPC-167832. In a mouse model of chronic TB, OPC-167832 showed potent bactericidal activities starting at a dose of 0.625 mg/kg of body weight. Further, it exhibited significant combination effects in 2-drug combinations with delamanid, bedaquiline, or levofloxacin. Finally, 3- or 4-drug regimens comprised of delamanid and OPC-167832 as the core along with bedaquiline, moxifloxacin, or linezolid showed efficacy in reducing the bacterial burden and preventing relapse superior to that of the standard treatment regimen. In summary, these results suggest that OPC-167832 is a novel and potent anti-TB agent, and regimens containing OPC-167832 and new or repurposed anti-TB drugs may have the potential to shorten the duration of treatment for TB.

Antidiabetic and cardiovascular beneficial effects of a liver-localized mitochondrial uncoupler.

Inducing mitochondrial uncoupling (mUncoupling) is an attractive therapeutic strategy for treating metabolic diseases because it leads to calorie-wasting by reducing the efficiency of oxidative phosphorylation (OXPHOS) in mitochondria. Here we report a safe mUncoupler, OPC-163493, which has unique pharmacokinetic characteristics. OPC-163493 shows a good bioavailability upon oral administration and primarily distributed to specific organs: the liver and kidneys, avoiding systemic toxicities. It exhibits insulin-independent antidiabetic effects in multiple animal models of type I and type II diabetes and antisteatotic effects in fatty liver models. These beneficial effects can be explained by the improvement of glucose metabolism and enhancement of energy expenditure by OPC-163493 in the liver. Moreover, OPC-163493 treatment lowered blood pressure, extended survival, and improved renal function in the rat model of stroke/hypertension, possibly by enhancing NO bioavailability in blood vessels and reducing mitochondrial ROS production. OPC-163493 is a liver-localized/targeted mUncoupler that ameliorates various complications of diabetes.

Screening for novel antituberculosis agents that are effective against multidrug resistant tuberculosis.

The challenges in preventing and controlling tuberculosis are further complicated by the deadly rise of multi-drug-resistant tuberculosis (MDR-TB). Recognizing the seriousness of the situation, we initiated a program to screen new agents that would satisfy these unmet needs and have a favorable safety profile. Mycobacteria are well known for their lipid-rich properties. In Mycobacterium tuberculosis, mycolic acid in particular has been established the wall component related to the pathogenesis in the host. There are approximately 250 identified genes related to biosynthesis of the lipid turnover that contain InhA, the main target of isoniazid. Thus, the logical approach for developing a chemotherapy agent against tubercle bacilli included screening compounds that could inhibit the biosyntheses of mycolic acid and that had a novel chemical structure to ensure improved efficacy against MDR-TB. Some of the screening systems established for those purposes and some of the candidates are outlined.

Synthesis and antituberculosis activity of a novel series of optically active 6-nitro-2,3-dihydroimidazo[2,1-b]oxazoles.

In an effort to develop potent new antituberculosis agents that would be effective against both drug-susceptible and drug-resistant strains of Mycobacterium tuberculosis, we prepared a novel series of optically active 6-nitro-2,3-dihydroimidazo[2,1-b]oxazoles substituted at the 2-position with various phenoxymethyl groups and a methyl group and investigated the in vitro and in vivo activity of these compounds. Several of these derivatives showed potent in vitro and in vivo activity, and compound 19 (OPC-67683) in particular displayed excellent in vitro activity against both drug-susceptible and drug-resistant strains of M. tuberculosis H37Rv (MIC = 0.006 microg/mL) and dose-dependent and significant in vivo efficacy at lower oral doses than rifampicin in mouse models infected with M. tuberculosis Kurono. The synthesis and structure-activity relationships of these new compounds are presented.