Synthesis and antiviral properties of novel 7-heterocyclic substituted 7-deaza-adenine nucleoside inhibitors of Hepatitis C NS5B polymerase.

Previous investigations in our laboratories resulted in the discovery of a novel series of potent nucleoside inhibitors of Hepatitis C virus (HCV) NS5B polymerase bearing tetracyclic 7-substituted 7-deaza-adenine nucleobases. The planarity of such modified systems was suggested to play a role in the high inhibitory potency observed. This paper describes how we envisaged to maintain the desired planarity of the modified nucleobase by means of an intra-molecular H-bond, engaging a H-bond donor atom on an appropriately substituted 7-heterocyclic residue with the adjacent amino group of the nucleobase. The success of this strategy is reflected by the identification of several novel potent nucleoside inhibitors of HCV NS5B bearing a 7-heterocyclic substituted 7-deaza-adenine nucleobase. Amongst these, the 1,2,4-oxadiazole analog 11 showed high antiviral potency against HCV replication in replicon cells and efficient conversion to the corresponding NTP in vivo, with high and sustained levels of NTP measured in rat liver following intravenous and oral administration.

Allosteric inhibitors of hepatitis C virus NS5B polymerase thumb domain site II: structure-based design and synthesis of new templates.

Chronic hepatitis C virus (HCV) infections are a significant medical problem worldwide. The NS5B Polymerase of HCV plays a central role in virus replication and is a prime target for the discovery of new treatment options. We recently disclosed 1H-benzo[de]isoquinoline-1,3(2H)-diones as allosteric inhibitors of NS5B Polymerase. Structural and SAR information guided us in the modification of the core structure leading to new templates with improved activity and toxicity/activity window.

Novel P2-P4 macrocyclic inhibitors of HCV NS3/4A protease by P3 succinamide fragment depeptidization strategy.

Hepatitis C represents a serious worldwide health-care problem. Recently, we have disclosed a novel class of P2-P4 macrocyclic inhibitors of NS3/4A protease containing a carbamate functionality as capping group at the P3 N-terminus. Herein we report our work aimed at further depeptidizing the P3 region by replacement of the urethane function with a succinamide motif. This peptidomimetic approach has led to the discovery of novel P2-P4 macrocyclic inhibitors of HCV NS3/4A protease with sub-nanomolar enzyme affinities. In addition to being potent inhibitors of HCV subgenomic replication, optimized analogues within this series have also presented attractive PK properties and showed promising liver levels in rat following oral administration.

Discovery of 2-{4-[(3S)-piperidin-3-yl]phenyl}-2H-indazole-7-carboxamide (MK-4827): a novel oral poly(ADP-ribose)polymerase (PARP) inhibitor efficacious in BRCA-1 and -2 mutant tumors.

We disclose the development of a novel series of 2-phenyl-2H-indazole-7-carboxamides as poly(ADP-ribose)polymerase (PARP) 1 and 2 inhibitors. This series was optimized to improve enzyme and cellular activity, and the resulting PARP inhibitors display antiproliferation activities against BRCA-1 and BRCA-2 deficient cancer cells, with high selectivity over BRCA proficient cells. Extrahepatic oxidation by CYP450 1A1 and 1A2 was identified as a metabolic concern, and strategies to improve pharmacokinetic properties are reported. These efforts culminated in the identification of 2-{4-[(3S)-piperidin-3-yl]phenyl}-2H-indazole-7-carboxamide 56 (MK-4827), which displays good pharmacokinetic properties and is currently in phase I clinical trials. This compound displays excellent PARP 1 and 2 inhibition with IC(50) = 3.8 and 2.1 nM, respectively, and in a whole cell assay, it inhibited PARP activity with EC(50) = 4 nM and inhibited proliferation of cancer cells with mutant BRCA-1 and BRCA-2 with CC(50) in the 10-100 nM range. Compound 56 was well tolerated in vivo and demonstrated efficacy as a single agent in a xenograft model of BRCA-1 deficient cancer.

Novel macrocyclic inhibitors of hepatitis C NS3/4A protease featuring a 2-amino-1,3-thiazole as a P4 carbamate replacement.

Our laboratories recently reported the discovery of P2-P4 macrocyclic inhibitors of HCV NS3/4A protease, characterized by high levels of potency and liver exposure. Within this novel class of inhibitors, we here describe the identification of a structurally diverse series of compounds featuring a 2-amino-1,3-thiazole as replacement of the carbamate in P4. Optimization studies focused on structural modifications in the P3, P2, and P1 regions of the macrocycle as well as on the linker chain and resulted in the discovery of several analogues characterized by excellent levels of enzyme and cellular activity. Among these, compound 59 displayed an attractive pharmacokinetic profile in preclinical species and showed sustained liver levels following oral administration in rats.

Inhibitors of the hepatitis C virus NS3 protease with basic amine functionality at the P3-amino acid N-terminus: discovery and optimization of a new series of P2-P4 macrocycles.

In a follow-up to our recent disclosure of P2-P4 macrocyclic inhibitors of the hepatitis C virus (HCV) NS3 protease (e.g., 1, Chart 1), we report a new but related compound series featuring a basic amine at the N-terminus of the P3-amino acid residue. Replacement of the electroneutral P3-amino acid capping group (which is a feature of almost all tripeptide-like inhibitors of NS3 reported to date) with a basic group is not only tolerated but can result in advantageous cell based potency. Optimization of this new class of P3-amine based inhibitors gave compounds such as 25 and 26 that combine excellent cell based activity with pharmacokinetic properties that are attractive for an antiviral targeting HCV.

Discovery and synthesis of HIV integrase inhibitors: development of potent and orally bioavailable N-methyl pyrimidones.

The human immunodeficiency virus type-1 (HIV-1) encodes three enzymes essential for viral replication: a reverse transcriptase, a protease, and an integrase. The latter is responsible for the integration of the viral genome into the human genome and, therefore, represents an attractive target for chemotherapeutic intervention against AIDS. A drug based on this mechanism has not yet been approved. Benzyl-dihydroxypyrimidine-carboxamides were discovered in our laboratories as a novel and metabolically stable class of agents that exhibits potent inhibition of the HIV integrase strand transfer step. Further efforts led to very potent compounds based on the structurally related N-Me pyrimidone scaffold. One of the more interesting compounds in this series is the 2-N-Me-morpholino derivative 27a, which shows a CIC95 of 65 nM in the cell in the presence of serum. The compound has favorable pharmacokinetic properties in three preclinical species and shows no liabilities in several counterscreening assays.

The monoethyl ester of meconic acid is an active site inhibitor of HCV NS5B RNA-dependent RNA polymerase.

Screening of the in-house sample collection for compounds with HCV NS5B RNA dependent RNA polymerase inhibition led to the identification of a new lead. Afterwards, we discovered that the screening lead, rather than containing the expected structure 1, was comprised of roughly a 1:1 mixture of meconic acid 2 and its monoethyl ester 3, with all inhibitory potency residing with 3. We propose that this compound shares critical common features for activity with alpha,gamma-diketoacids inhibitors previously discovered by our group. SAR around this molecule will be presented to provide an improved basis for structure-based ligand design.