Diminishing GSH-Adduct Formation of Tricyclic Diazepine-based Mutant IDH1 Inhibitors.

Mutant isocitrate dehydrogenase 1 (IDH1) has been identified as an attractive oncology target for which >70% of grade II and III gliomas and ∼10% of acute myeloid leukemia (AML) harbor somatic IDH1 mutations. These mutations confer a neomorphic gain of function, leading to the production of the oncometabolite (R)-2-hydroxyglutarate (2-HG). We identified and developed a potent, selective, and orally bioavailable brain-penetrant tricyclic diazepine scaffold that inhibits mutant IDH1. During the course of in vitro metabolism studies, GSH-adduct metabolites were observed. The hypothesis for GSH-adduct formation was driven by the electron-rich nature of the tricyclic core. Herein, we describe our efforts to reduce the electron-rich nature of the core. Ultimately, a strategy focused on core modifications to block metabolic hot spots coupled with substitution pattern changes (C8 N → C linked) led to the identification of new tricyclic analogues with minimal GSH-adduct formation across species while maintaining an overall balanced profile.

Phe19 modification of HDM2-p53 PPI inhibitors to alleviate CYP3A4 metabolism/mechanism-based inhibition liability.

The discovery of potent, bioavailable small molecule inhibitors of p53-HDM2 PPI led us to investigate subsequent modifications to address a CYP3A4 time-dependent inhibition liability. On the basis of the crystal structure of HDM2 in complex with 2, further functionalization of the solvent exposed area of the molecule that binds to Phe19 pocket were investigated as a strategy to modulate the molecule liphophilicity. Introduction of 2-oxo-nicotinic amide at Phe19 proved a viable strategy in obtaining inhibitors exempt from CYP3A4 time-dependent inhibition liability.

Discovery of MK-4688: an Efficient Inhibitor of the HDM2-p53 Protein-Protein Interaction.

Identification of low-dose, low-molecular-weight, drug-like inhibitors of protein-protein interactions (PPIs) is a challenging area of research. Despite the challenges, the therapeutic potential of PPI inhibition has driven significant efforts toward this goal. Adding to recent success in this area, we describe herein our efforts to optimize a novel purine carboxylic acid-derived inhibitor of the HDM2-p53 PPI into a series of low-projected dose inhibitors with overall favorable pharmacokinetic and physical properties. Ultimately, a strategy focused on leveraging known binding hot spots coupled with biostructural information to guide the design of conformationally constrained analogs and a focus on efficiency metrics led to the discovery of MK-4688 (compound 56), a highly potent, selective, and low-molecular-weight inhibitor suitable for clinical investigation.

Concise syntheses and HCV NS5B polymerase inhibition of (2'R)-3 and (2'S)-2'-ethynyluridine-10 and related nucleosides.

(2'R)-Ethynyl uridine 3, and its (2'S)-diastereomer 10, are synthesised in a divergent fashion from the inexpensive parent nucleoside. Both nucleoside analogues are obtained from a total of 5 simple synthetic steps and 3 trivial column chromatography purifications. To evaluate their effectiveness against HCV NS5B polymerase, the nucleosides were converted to their respective 5'-O-triphosphates. Subsequently, this lead to the discovery of the 2'-ß-ethynyl 18 and -propynyl 20 nucleotides having significantly improved potency over Sofosbuvir triphosphate 24.

Structure-activity relationship study of 4-substituted piperidines at Leu26 moiety of novel p53-hDM2 inhibitors.

Led by the structural information of the screening hit with mDM2 protein, a structure modification of Leu26 moiety of the novel p53-hDM2 inhibitors was conducted. A structure-activity relationship study of 4-substituted piperidines revealed compound 20t with good potencies and excellent CYP450 profiles.

2'-Modified Guanosine Analogs for the Treatment of HCV.

Novel 2'-modified guanosine nucleosides were synthesized from inexpensive starting materials in 7-10 steps via hydroazidation or hydrocyanation reactions of the corresponding 2'-olefin. The antiviral effectiveness of the guanosine nucleosides was evaluated by converting them to the corresponding 5'-O-triphosphates (compounds 38-44) and testing their biochemical inhibitory activity against the wild-type NS5B polymerase.

Discovery of Novel 3,3-Disubstituted Piperidines as Orally Bioavailable, Potent, and Efficacious HDM2-p53 Inhibitors.

A new subseries of substituted piperidines as p53-HDM2 inhibitors exemplified by 21 has been developed from the initial lead 1. Research focused on optimization of a crucial HDM2 Trp23-ligand interaction led to the identification of 2-(trifluoromethyl)thiophene as the preferred moiety. Further investigation of the Leu26 pocket resulted in potent, novel substituted piperidine inhibitors of the HDM2-p53 interaction that demonstrated tumor regression in several human cancer xenograft models in mice. The structure of HDM2 in complex with inhibitors 3, 10, and 21 is described.

Pivotal Role of an Aliphatic Side Chain in the Development of an HDM2 Inhibitor.

Introduction of an aliphatic side chain to a key position of a novel piperidine-based HDM2 inhibitor scaffold resulted in significant potency gains, enabling further series progression.

Core modification of substituted piperidines as novel inhibitors of HDM2-p53 protein-protein interaction.

The discovery of 3,3-disubstituted piperidine 1 as novel p53-HDM2 inhibitors prompted us to implement subsequent SAR follow up directed towards piperidine core modifications. Conformational restrictions and further functionalization of the piperidine core were investigated as a strategy to gain additional interactions with HDM2. Substitutions at positions 4, 5 and 6 of the piperidine ring were explored. Although some substitutions were tolerated, no significant improvement in potency was observed compared to 1. Incorporation of an allyl side chain at position 2 provided a drastic improvement in binding potency.

Cyclic sulfones as novel P3-caps for hepatitis C virus NS3/4A (HCV NS3/4A) protease inhibitors: synthesis and evaluation of inhibitors with improved potency and pharmacokinetic profiles.

HCV infection affects more than 170 million people worldwide and many of those patients will reach the end stage complications of the disease which include hepatocarcinoma and liver failure. The success rate for treatment of patients infected with genotype-1 is about 40%. Therefore, novel treatments are needed to combat the infection. The HCV NS3 protease inhibitor Boceprevir (1) was reported by our research group and efforts continue for the discovery of more potent compounds with improved pharmacokinetic profiles. A new series of HCV NS3 protease inhibitors having a cyclic sulfone P3-cap have been discovered. Compounds 43 and 44 showed K(i)* values in the single-digit nM range and their cellular potency was improved by 10-fold compared to 1. The pharmacokinetic profiles of 43 and 44 in rats and monkeys were also improved to achieve higher plasma levels after oral administration.

The introduction of P4 substituted 1-methylcyclohexyl groups into Boceprevir: a change in direction in the search for a second generation HCV NS3 protease inhibitor.

In the search for a second generation HCV protease inhibitor, molecular modeling studies of the X-ray crystal structure of Boceprevir1 bound to the NS3 protein suggest that expansion into the S4 pocket could provide additional hydrophobic Van der Waals interactions. Effective replacement of the P4 tert-butyl with a cyclohexylmethyl ligand led to inhibitor 2 with improved enzyme and replicon activities. Subsequent modeling and SAR studies led to the pyridine 38 and sulfone analogues 52 and 53 with vastly improved PK parameters in monkeys, forming a new foundation for further exploration.

Towards the second generation of Boceprevir: Dithianes as an alternative P2 substituent for 2,2-dimethyl cycloproyl proline in HCV NS3 protease inhibitors.

Hepatitis C (HCV) infection is a global health crisis leading to chronic liver disease. In our efforts towards a second generation HCV NS3 serine protease inhibitor with improved profile, we have undertaken SAR studies in various regions of Boceprevir including P2. Herein, we report the synthesis and structure-activity relationship studies of inhibitors with (S)-1,4-dithia-7-azaspiro[4.4]nonane-8-carboxylic acid 2 as P2 substituent replacing the (1R,2S,5S)-6,6-dimethyl 3-azabicyclo[3.1.0]hexane-2-carboxylic acid. The systematic investigation led to the discovery of highly potent inhibitor 25 (K(i)( *)=7nM, EC(90)=30nM) with improved rat exposure of 2.56microM h.

Discovery of potent sulfonamide P4-capped ketoamide second generation inhibitors of hepatitis C virus NS3 serine protease with favorable pharmacokinetic profiles in preclinical species.

Hepatitis is a disease characterized by inflammation of the liver, usually producing swelling and, in many cases, permanent damage to liver tissues. Viral hepatitis C (HCV), a small (+)-RNA virus, infects chronically 3% of the world's population. Boceprevir, SCH 503034, (1) our first generation HCV inhibitor, has already established proof-of- concept and is currently in late stage (phase III) clinical trials. In view of the positive data from our first generation compound, further work aimed at optimizing its overall profile was undertaken. Herein, we report that extension of our earlier inhibitor to the P(4) pocket by introducing a new sulfonamide moiety and optimization of the P1/P(1)' capping led to the discovery of a novel series of inhibitors of the HCV NS3 serine protease. Optimization of the P(1) residue significantly improved potency and selectivity. The combination of optimal moieties led to the discovery of compound 47 which, in addition to being a potent inhibitor of HCV subgenomic RNA replication, was also found to have good PK profile in rat, dog and monkey.

Discovery of Narlaprevir (SCH 900518): A Potent, Second Generation HCV NS3 Serine Protease Inhibitor.

Boceprevir (SCH 503034), 1, a novel HCV NS3 serine protease inhibitor discovered in our laboratories, is currently undergoing phase III clinical trials. Detailed investigations toward a second generation protease inhibitor culminated in the discovery of narlaprevir (SCH 900518), 37, with improved potency (∼10-fold over 1), pharmacokinetic profile and physicochemical characteristics, currently in phase II human trials. Exploration of synthetic sequence for preparation of 37 resulted in a route that required no silica gel purification for the entire synthesis.

P4 capped amides and lactams as HCV NS3 protease inhibitors with improved potency and DMPK profile.

SAR studies on the extension of P3 unit of Boceprevir (1, SCH 503034) with amides and lactams and their synthesis is described. Extensive SAR studies resulted in the identification of 36 bearing 4, 4-dimethyl lactam as the new P4 cap unit with improved potency (K(i)( *)=15nM, EC 90=70nM) and pharmacokinetic properties (Rat AUC (PO)=3.52microMh) compared to 1.

Discovery of novel P3 sulfonamide-capped inhibitors of HCV NS3 protease. Inhibitors with improved cellular potencies.

Hepatitis C Virus (HCV) infection is the major cause of chronic liver disease, leading to cirrhosis and hepatocellular carcinoma, which affects more than 200 million people worldwide. Currently the only therapeutic regimens are subcutaneous interferon-alpha or PEG-interferon alone or in combination with oral ribavirin. Although combination therapy is reasonably successful with the majority of genotypes, its efficacy against the predominant genotype (genotype 1) is moderate at best, with only approximately 50% of the patients showing sustained virological response. We recently disclosed the discovery of Boceprevir, SCH 503034 (1), which is a novel, potent, selective, orally bioavailable NS3 protease inhibitor that has been shown to be efficacious in humans and is currently undergoing clinical trials. As second generation compounds, we have further explored various novel structures with the aim of improving enzyme and cellular binding activities of 1. Herein, we disclose our efforts toward the identification of a novel P(3) sulfonamide-capped inhibitor that demonstrated improved binding and cellular activity compared to 1. X-ray structure of one of these inhibitors bound to the enzyme revealed a hydrogen bond of the P(3) sulfonamide group to Cys-159 which resulted in improved binding and cellular potency.

Toward the back-up of boceprevir (SCH 503034): discovery of new extended P4-capped ketoamide inhibitors of hepatitis C virus NS3 serine protease with improved potency and pharmacokinetic profiles.

Hepatitis C is the most prevalent liver disease. Viral hepatitis C (HCV), a small (+)-RNA virus, infects chronically an estimated 300 million people worldwide. Results of Phase I clinical studies with our first generation HCV inhibitor Boceprevir, SCH 503034 (1), presented at the 56th Annual Meeting of the American Association for the Study of Liver Diseases (AASLD) were encouraging, and thus, additional human clinical studies are underway. In view of the positive data from our first generation compound, further work aimed at optimizing its overall profile was undertaken. Herein, we report that extension of our earlier inhibitor to the P(4) pocket and optimization of the P(1)' capping led to the discovery of new ketoamide inhibitors of the HCV NS3 serine protease with improved in vitro potency. In addition to being potent inhibitors of HCV subgenomic RNA replication, some of the new P(4)-capped inhibitors were also found to have improved PK profile.

Toward second generation hepatitis C virus NS3 serine protease inhibitors: discovery of novel P4 modified analogues with improved potency and pharmacokinetic profile.

Hepatitis C virus (HCV) infection is a global health crisis leading to liver cirrhosis, hepatocellular carcinoma, and liver failure in humans. Recently, we disclosed the discovery of Boceprevir, SCH 503034 (1), a novel, potent, selective, orally bioavailable NS3 protease inhibitor that is currently undergoing phase III clinical trials. Our efforts toward a second generation HCV NS3 serine protease inhibitor were directed at improving the overall profile of the inhibitor. This article will elaborate on our studies leading to the discovery of new P4 modified inhibitors with enhanced potency and improved oral bioavailability. Thus, introduction of ether and carbamate-derived P4 moieties resulted in improving the replicon potency significantly. Incorporation of the P' secondary amide residue afforded significant improvement in pharmacokinetic properties. Combining the preferred moieties, identified from comprehensive SAR studies, resulted in inhibitors that displayed superior potency and very good oral as well as target organ exposure in rats.

Second-generation highly potent and selective inhibitors of the hepatitis C virus NS3 serine protease.

The hepatitis C virus (HCV) infection is a leading cause of chronic liver disease. The moderate efficacy along with side effects of the current pegylated interferon and ribavirin combination therapy underscores the need for more effective and safer new treatment. In an effort to improve upon our current clinical candidate, Boceprevir (SCH 503034), extensive SAR studies were performed on the P3 capping moieties. This led to the discovery of tert-leucinol derived cyclic imides as a potent series of novel P3 capping groups. Thus, the introduction of these imide caps improved the cell-based replicon EC(90) by more than 10-fold. A number of imides with various substitutions, ring sizes, bicyclic systems, and heterocyclic rings were explored. The 4,4-dimethyl substituted glutarimide emerged as the best cap as exemplified in compound 21 (K(i)* = 4 nM, EC(90) = 40 nM). Systematic optimization of different positions (P', P3, and P1) of the inhibitor resulted in the identification of the lead compound 46, which had an excellent potency (K(i)* = 4 nM, EC(90) = 30 nM) and good pharmacokinetic profile (22% and 35% bioavailability in rats and dogs, respectively). X-ray structure of inhibitor 46 bound to the enzyme revealed that there was an additional hydrogen bonding interaction between one of the imide carbonyls and Cys159.

Design, synthesis, and evaluation of oxygen-containing macrocyclic peptidomimetics as inhibitors of HCV NS3 protease.

HCV infection is considered a silent epidemic because most people infected do not develop acute symptoms. Instead, the disease progresses to a chronic state leading to cirrhosis and hepatocarcinoma. Novel therapies are needed to combat this major health threat. The HCV NS3 serine protease has been the target of continuous investigation because of its pivotal role in viral replication. Herein, we present the P1-P3 macrocyclization approach followed for identification of HCV NS3 inhibitors as potential backup candidates to our first generation drug candidate, Sch 503034 (1). Different P1-P3 linkers were investigated to identify novel macrocyclic scaffolds. SAR exploration of P3-caps in the macrocyclic cores allowed the identification of l-serine derived macrocycle 32 (Ki* = 3 nM, EC90 = 30 nM) and allo-threonine derived macrocycle 36 (Ki* = 3 nM, EC90 = 30 nM) as potent HCV NS3 protease inhibitors.