Development of Chemical Entities Endowed with Potent Fast-Killing Properties against Malaria Parasites.

One of the attractive properties of artemisinins is their extremely fast-killing capability, quickly relieving malaria symptoms. Nevertheless, the unique benefits of these medicines are now compromised by the prolonged parasite clearance times and the increasing frequency of treatment failures, attributed to the increased tolerance of to artemisinin. This emerging artemisinin resistance threatens to undermine the effectiveness of antimalarial combination therapies.

The Discovery of Novel Antimalarial Aminoxadiazoles as a Promising Nonendoperoxide Scaffold.

Since the appearance of resistance to the current front-line antimalarial treatments, ACTs (artemisinin combination therapies), the discovery of novel chemical entities to treat the disease is recognized as a major global health priority. From the GSK antimalarial set, we identified an aminoxadiazole with an antiparasitic profile comparable with artemisinin (1), with no cross-resistance in a resistant strains panel and a potential new mode of action. A medicinal chemistry program allowed delivery of compounds such as 19 with high solubility in aqueous media, an acceptable toxicological profile, and oral efficacy.

Identification of MK-5710 ((8aS)-8a-methyl-1,3-dioxo-2-[(1S,2R)-2-phenylcyclopropyl]-N-(1-phenyl-1H-pyrazol-5-yl)hexahydroimid azo[1,5-a]pyrazine-7(1H)-carboxamide), a potent smoothened antagonist for use in Hedgehog pathway dependent malignancies, part 1.

The Hedgehog (Hh-) signaling pathway is a key developmental pathway which controls patterning, growth and cell migration in most tissues, but evidence has accumulated showing that many human tumors aberrantly reactivate this pathway. Smoothened antagonists offer opportunities for the treatment of malignancies dependent on the Hh pathway, and the most advanced clinical candidates are demonstrating encourage initial results. A novel series of [6,5]-bicyclic tetrahydroimidazo[1,5-a]pyrazine-1,3(2H,5H)-dione smoothened antagonists has been identified, and the series has been extensively explored to ascertain the key detriments for activity, demonstrating that the trans-2-phenylcyclopropyl and hydantoin ring systems are critical for potency, while a variety of urea substituents can be tolerated.

Identification of MK-5710 ((8aS)-8a-methyl-1,3-dioxo-2-[(1S,2R)-2-phenylcyclo- propyl]-N-(1-phenyl-1H-pyrazol-5-yl)hexahydro-imidazo[1,5-a]pyrazine-7(1H)-carboxamide), a potent smoothened antagonist for use in Hedgehog pathway dependent malignancies, part 2.

The Hedgehog (Hh-) signaling pathway is a key developmental pathway which gets reactivated in many human tumors, and smoothened (Smo) antagonists are emerging as novel agents for the treatment of malignancies dependent on the Hh-pathway, with the most advanced compounds demonstrating encouraging results in initial clinical trials. A novel series of potent bicyclic hydantoin Smo antagonists was reported in the preceding article, these have been resolved, and optimized to identify potent homochiral derivatives with clean off-target profiles and good pharmacokinetic properties in preclinical species. While showing in vivo efficacy in mouse allograft models, unsubstituted bicyclic tetrahydroimidazo[1,5-a]pyrazine-1,3(2H,5H)-diones were shown to epimerize in plasma.

Optimization of thienopyrrole-based finger-loop inhibitors of the hepatitis C virus NS5B polymerase.

Infections caused by the hepatitis C virus (HCV) are a significant world health problem for which novel therapies are in urgent demand. The NS5B polymerase of HCV is responsible for the replication of viral RNA and has been a prime target in the search for novel treatment options. We had discovered allosteric finger-loop inhibitors based on a thieno[3,2-b]pyrrole scaffold as an alternative to the related indole inhibitors.

Inhibitors of hepatitis C virus NS3/4A: alpha-ketoamide based macrocyclic inhibitors.

A novel series of hepatitis C virus (HCV) NS3/4A protease inhibitors bearing a P2-P4 macrocycle and a P1-P1' alpha-ketoamide serine trap is reported. The NS3 protease, which is essential for viral replication, is considered one of the most attractive targets for developing novel anti-HCV therapies. The optimization of both the macrocycle and the warhead portions led to the discovery of compounds 8b and 8 g with a good activity both in the enzyme as well as in the cell based (replicon) assays with favorable PK profile in a preclinical species.