Discovery of Tetrahydropyrazolopyrimidine Carboxamide De-rivatives as Potent and Orally Active Novel Anti-Tubercular Agents

ABSTRACT: Tetrahydropyrazolopyrimidine scaffold was identified as a hit series from a Mycobacterium tuberculosis (Mtb) whole cell high through-put screening (HTS) campaign. A series of derivatives of this class were synthesized to evaluate their structure-activity relationship (SAR) and structure-property relationship (SPR). Compound 9 showed potent bactericidal effect and activity against multi-drug resistant tuberculosis (MDR TB) strains. Furthermore compound 9 had a promising in vivo DMPK profile in mouse and exhibited potent in vivo activity in a mouse efficacy model, achieving a reduction of 3.5 log CFU of Mtb after oral administration to infected mice once a day at 100 mg/kg for 28 days. Thus the compound 9 is a potential candidate for inclusion in combination therapies for both drug-sensitive and drug-resistant TB

Discovery of Dengue Virus NS4B Inhibitors

The four serotypes of dengue virus (DENV-1 to -4) represent the most prevalent mosquito-borne viral pathogens in humans. No clinically approved vaccine or antiviral is currently available for DENV. Here we report a spiropyrazolopyridone compound that potently inhibits DENV both in vitro and in vivo. The inhibitor was identified through screening of a 1.8-million-compound library by using a DENV-2 replicon assay. The compound selectively inhibits DENV-2 and -3 (50% effective concentration [EC50], 10 to 80 nM) but not DENV-1 and -4 (EC50, >20 μM). Resistance analysis showed that a mutation at amino acid 63 of DENV-2 NS4B (a nonenzymatic transmembrane protein and a component of the viral replication complex) could confer resistance to compound inhibition. Genetic studies demonstrate that variations at amino acid 63 of viral NS4B are responsible for the selective inhibition of DENV-2 and -3. Medicinal chemistry improved the physicochemical properties of the initial “hit” (compound 1), leading to compound 14a, which has good in vivo pharmacokinetics. Treatment of DENV-2-infected AG129 mice with compound 14a suppressed viremia, even when the treatment started after viral infection. The results have proven the concept that inhibitors of NS4B could potentially be developed for clinical treatment of DENV infection. Compound 14a represents a potential preclinical candidate for treatment of DENV-2- and -3-infected patients.Published versio

A Cyclic Phosphoramidate Prodrug of 2'-deoxy-2'-fluoro-2'-C-methylguanosine for the Treatment of Dengue Infection

Monophosphate prodrug analogs of 2'-deoxy-2'-fluoro-2'-C-methylguanosine have been reported as potent inhibitors of hepatitis C virus (HCV) RNA-dependent RNA polymerase. These prodrugs also display potent anti-dengue activities in cellular assays although their prodrug moieties were designed to produce high levels of triphosphate in the liver. Since peripheral blood mononuclear cells (PBMCs) are one of the major targets of dengue virus, different prodrug moieties were designed to effectively deliver 2'-deoxy-2'-fluoro-2'-C-methylguanosine monophosphate prodrugs and their corresponding triphosphates into PBMCs after oral administration. We identified a cyclic phosphoramidate prodrug 17 demonstrating a well-balanced anti-dengue cellular activity and in vitro stability profiles. We further determined the PBMCs concentration of active triphosphate needed to inhibit 50% virus replication (TP50). Compound 17 was assessed in AG129 mouse model and demonstrated 1.6- and 2.2-log viremia reduction at 100 and 300 mg/kg BID, respectively. At 100 mg/kg BID, the terminal triphosphate concentration in PBMCs reached above TP50, demonstrating TP50 as the target exposure for efficacy. In dogs, oral administration of 17 resulted in high PBMCs triphosphate level, exceeding TP50 at 10 mg/kg. Unfortunately, two-week dog toxicity studies at 30, 100, and 300 mg/kg/day showed that No Observed Adverse Effect Level (NOAEL) could not be achieved due to pulmonary inflammation and hemorrhage. The preclinical safety results suspended further development of 17 Nevertheless, present work has proven the concept that an efficacious monophosphate nucleoside prodrug could be developed for the potential treatment of dengue infection

Indolcarboxamide, a promising pre-clinical candidate for the treatment of multi drug resistant tuberculosis

To combat the drug resistance in tuberculosis, new chemotherapeutics active against multi-drug resistant Mycobacterium tuberculosis are urgently needed. We have identified and characterized the indolcarboxamides as a new class of anti-tubercular bactericidal agents. Genetics and lipid profiling studies identified the molecular target of indolcarboxamides as mmpL3, a transporter of TMM, a promiscuous target essential for mycobacterial cell wall biosynthesis. Two lead candidates NITD-304 and NITD-349 showed a significantly potent anti-TB activity against both drug sensitive and multi-drug resistant clinical Mtb isolates. Both compounds displayed favorable pharmacokinetic properties after oral administration in pre-clinical species. NITD-304 and NITD-349 showed no apparent inhibition of major CYP enzymes and are highly efficacious in both acute and chronic TB mouse efficacy models. Furthermore, we have assessed in vitro and in vivo safety profile of both candidates including two weeks exploratory rat toxicology studies. NITD-304 and NITD-349 show the adequate therapeutic index to justify further development for inclusion in the combination therapies for drug sensitive as well as drug resistant TB

Lead Optimization of Spiropyrazolopyridones: A New and Potent Class of Dengue Virus Inhibitors

Spiropyrazolopyridone <b>1</b> was identified, as a novel dengue virus (DENV) inhibitor, from a DENV serotype 2 (DENV-2) high-throughput phenotypic screen. As a general trend within this chemical class, chiral resolution of the racemate revealed that <i>R</i> enantiomer was significantly more potent than the <i>S</i>. Cell-based lead optimization of the spiropyrazolopyridones focusing on improving the physicochemical properties is described. As a result, an optimal compound <b>14a</b>, with balanced <i>in vitro</i> potency and pharmacokinetic profile, achieved about 1.9 log viremia reduction at 3 × 50 mg/kg (bid) or 3 × 100 mg/kg (QD) oral doses in the dengue <i>in vivo</i> mouse efficacy model