Mark W. Embrey

Inhibition of HIV-1 Ribonuclease H by a Novel Diketo Acid, 4-[5-(Benzoylamino)thien-2-yl]-2,4-dioxobutanoic Acid

Human immunodeficiency virus-type 1 (HIV-1) reverse transcriptase (RT) coordinates DNA polymerization and ribonuclease H (RNase H) activities using two discrete active sites embedded within a single heterodimeric polyprotein. We have identified a novel thiophene diketo acid, 4-[5-(benzoylamino)thien-2-yl]-2,4-dioxobutanoic acid, that selectively inhibits polymerase-independent RNase H cleavage (IC50 = 3.2 μm) but has no effect on DNA polymerization (IC50 > 50 μm). The activity profile of the diketo acid is shown to be distinct from previously described compounds, including the polymerase inhibitor foscarnet and the putative RNase H inhibitor 4-chlorophenylhydrazone. Both foscarnet and the hydrazone inhibit RNase H cleavage and DNA polymerization activities of RT, yet neither inhibits the RNase H activity of RT containing a mutation in the polymerase active site (D185N) or an isolated HIV-1 RNase H domain chimera containing the α-C helix from Escherichia coli RNase HI, suggesting these compounds affect RNase H indirectly. In contrast, the diketo acid inhibits the RNase H activity of the isolated RNase H domain as well as full-length RT, and inhibition is not affected by the polymerase active site mutation. In isothermal titration calorimetry studies using the isolated RNase H domain, binding of the diketo acid is independent of nucleic acid but strictly requires Mn2+implying a direct interaction between the inhibitor and the RNase H active site. These studies demonstrate that inhibition of HIV-1 RNase H may occur by either direct or indirect mechanisms, and they provide a framework for identifying novel agents such as 4-[5-(benzoylamino)thien- 2-yl]-2,4-dioxobutanoic acid that specifically targets RNase H.

Discovery of a 3-(4-Pyrimidinyl) Indazole (MLi-2), an Orally Available and Selective Leucine-Rich Repeat Kinase 2 (LRRK2) Inhibitor that Reduces Brain Kinase Activity

Leucine-rich repeat kinase 2 (LRRK2) is a large, multidomain protein which contains a kinase domain and GTPase domain among other regions. Individuals possessing gain of function mutations in the kinase domain such as the most prevalent G2019S mutation have been associated with an increased risk for the development of Parkinsons disease (PD). Given this genetic validation for inhibition of LRRK2 kinase activity as a potential means of affecting disease progression, our team set out to develop LRRK2 inhibitors to test this hypothesis. A high throughput screen of our compound collection afforded a number of promising indazole leads which were truncated in order to identify a minimum pharmacophore. Further optimization of these indazoles led to the development of MLi-2 (1): a potent, highly selective, orally available, brain-penetrant inhibitor of LRRK2.

An efficient synthesis of γ-alkylated E-olefin dipeptide isosteres

Abstract An efficient synthetic sequence was developed for the preparation of γ-alkylated E-olefin isosteres of dipeptides.

Correction to Discovery of 2-Pyridinone Aminals: A Prodrug Strategy to Advance a Second Generation of HIV-1 Integrase Strand Transfer Inhibitors.

The search for new molecular constructs that resemble the critical two-metal binding pharmacophore required for HIV integrase strand transfer inhibition represents a vibrant area of research within drug discovery. Here we present the discovery of a new class of HIV integrase strand transfer inhibitors based on the 2-pyridinone core of MK-0536. These efforts led to the identification of two lead compounds with excellent antiviral activity and preclinical pharmacokinetic profiles to support a once-daily human dose prediction. Dose escalating PK studies in dog revealed significant issues with limited oral absorption and required an innovative prodrug strategy to enhance the high-dose plasma exposures of the parent molecules.

Discovery and optimization of 2-pyridinone aminal integrase strand transfer inhibitors for the treatment of HIV.

HIV integrase strand transfer inhibitors (InSTIs) represent an important class of antiviral therapeutics with proven efficacy and excellent tolerability for the treatment of HIV infections. In 2007, Raltegravir became the first marketed strand transfer inhibitor pioneering the way to a first-line therapy for treatment-naïve patients. Challenges with this class of therapeutics remain, including frequency of the dosing regimen and the genetic barrier to resistance. To address these issues, research towards next-generation integrase inhibitors has focused on imparting potency against RAL-resistent mutants and improving pharmacokinetic profiles. Herein, we detail medicinal chemistry efforts on a novel class of 2-pyridinone aminal InSTIs, inpsired by MK-0536, which led to the discovery of important lead molecules for our program. Systematic optimization carried out at the amide and aminal positions on the periphery of the core provided the necessary balance of antiviral activity and physiochemical properties. These efforts led to a novel aminal lead compound with the desired virological profile and preclinical pharmacokinetic profile to support a once-daily human dose prediction.

Synthesis of 3-Alkyl-6-bromo-4,5-E-hexenoate

Abstract Two complementary routes for the preparation of 3-alkyl-6-bromo-4,5-E-hexenoate are reported.