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.

Long-Term Outcomes of Once-Daily Accelerated Partial-Breast Irradiation With Tomotherapy: Results of a Phase 2 Trial.

PURPOSE: We report long-term outcomes of phase 2 trial on patients with invasive breast cancer treated with accelerated partial-breast irradiation (APBI) using tomotherapy after breast conservative surgery. METHODS AND MATERIALS: From December 2010 to December 2018, we treated 338 women with APBI-tomotherapy: 38.5 Gy in 10 once-daily fractions. Patients selected were age ≥50 years old, with ≤3 cm in size unifocal tumor and at least 2 mm of clear margins. Disease outcomes were analyzed by clinicopathologic characteristics, molecular phenotypes, and American Society for Radiation Oncology (ASTRO) 2017 updated consensus groupings. RESULTS: The median age was 65 years (range, 50-86). The invasive ductal (87.5%) and the luminal A-like molecular phenotype (70%) were the most common tumors. Overall 242 patients (71.6%) were considered "suitable" for enrollment in APBI according to the eligibility criteria of the ASTRO-2017 consensus statement. With a median follow-up of 76 months (range, 17-113), 2 patients (0.6%) had an invasive ipsilateral breast tumor recurrence (IBTR), and 2 patients (0.6%) had an axillary ipsilateral failure. The rate of local control in terms of free of IBTR was 99.4% and locoregional control (no recurrence in ipsilateral breast as well as in regional nodes) was 98.8%. Progression-free survival was 98.4% and 92% at 5 and 10 years, respectively. Acute and late skin toxicity, graded according to the Common Terminology Criteria for Adverse Events, were 7.7% (G1) and 0.6% (G2) and 4.4% (G1) and 1.1% (G2), respectively. There were no grade 3/4 toxicities, however. Very few patients (2%) or physicians (2%) assessed cosmetic outcome as fair or poor at the 2-year follow-up. CONCLUSIONS: This phase 2 trial on APBI-tomotherapy shows excellent long-term results. Once-daily fractionation schedule was well tolerated with a low rate of adverse events and worse cosmetic outcome. In this series, even among those deemed cautionary or unsuitable for APBI by ASTRO criteria, we demonstrated a low rate of IBTR.

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.

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.

Phosphorous acid analogs of novel P2-P4 macrocycles as inhibitors of HCV-NS3 protease.

HCV-NS3 protease is essential for viral replication and NS3 protease inhibitors have shown proof of concept in clinical trials. Novel P2-P4 macrocycle inhibitors of NS3/4A comprising a P1 C-terminal carboxylic acid have recently been disclosed. A series of analogs, in which the carboxylic residue is replaced by phosphorous acid functionalities were synthesized and found to be inhibitors of the NS3 protease. Among them the methylphosphinate analogue showed nanomolar level of enzyme inhibition and sub-micromolar potency in the replication assay.

Tetracyclic indole inhibitors of hepatitis C virus NS5B-polymerase.

We report the evolutionary path from an open-chain series to conformationally constrained tetracyclic indole inhibitors of HCV NS5B-polymerase, where the C2 aromatic is tethered to the indole nitrogen. SAR studies led to the discovery of zwitterionic compounds endowed with good intrinsic enzyme affinity and cell-based potency, as well as superior DMPK profiles to their acyclic counterparts, and ultimately to the identification of a pre-clinical candidate with an excellent predicted human pharmacokinetic profile.

Synthesis and antiviral properties of novel tetracyclic nucleoside inhibitors of hepatitis C NS5B polymerase.

As part of an ongoing medicinal chemistry effort to identify novel nucleoside inhibitors of HCV NS5B polymerase, we report the discovery of a novel series of 2'-C-Methyl-ribose nucleoside derivatives bearing a 7-aryl and 7-heteroaryl- substituted 7-deaza-adenine nucleobase. A reliable platform for the synthesis and simplified purification of the corresponding nucleoside triphosphates (NTPs) was established, enabling a solid understanding of the SAR relationship within the series. By this approach, we identified the novel analogs 13a and 13b that demonstrated micromolar levels of cellular activity, and the NTPs of which, 16a and 16b, are excellent inhibitors of NS5B with IC(50) = 0.1 µM, a level of intrinsic potency similar to that of previous and current clinical candidates.

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.

Development of carboxylic acid replacements in indole-N-acetamide inhibitors of hepatitis C virus NS5B polymerase.

Allosteric inhibition of the hepatitis C virus (HCV) NS5B RNA-dependent RNA polymerase enzyme has recently emerged as a viable strategy toward blocking replication of viral RNA in cell-based systems. We report here 2 series of indole-N-acetamides, bearing physicochemically diverse carboxylic acid replacements, which show potent affinity for the NS5B enzyme with reduced potential for formation of glucuronide conjugates. Preliminary optimization of these series furnished compounds that are potent in the blockade of subgenomic HCV RNA replication in HUH-7 cells.