Despite efforts spanning four decades, the therapeutic potential of thyroid hormone receptor (TR) agonists as lipid-lowering and anti-obesity agents remains largely unexplored in humans because of dose-limiting cardiac effects and effects on the thyroid hormone axis (THA), muscle metabolism, and bone turnover. TR agonists selective for the TR␤ isoform exhibit modest cardiac sparing in rodents and primates but are unable to lower lipids without inducing TR␤-mediated suppression of the THA. Herein, we describe a cytochrome P450-activated prodrug of a phosphonatecontaining TR agonist that exhibits increased TR activation in the liver relative to extrahepatic tissues and an improved therapeutic

Despite major advances in the β-lactamase inhibitor field, certain enzymes remain refractory to inhibition by agents recently introduced. Most important among these are the class B (metallo) enzyme NDM-1 of Enterobacteriaceae and the class D (OXA) enzymes of Acinetobacter baumannii. Continuing the boronic acid program that led to vaborbactam, efforts were directed toward expanding the spectrum to allow treatment of a wider range of organisms. Through key structural modifications of a bicyclic lead, stepwise gains in spectrum of inhibition were achieved, ultimately resulting in QPX7728 (35). This compound displays a remarkably broad spectrum of inhibition, including class B and class D enzymes, and is little affected by porin modifications and efflux. Compound 35 is a promising agent for use in combination with a β-lactam antibiotic for the treatment of a wide range of multidrug resistant Gram-negative bacterial infections, by both intravenous and oral administration.

A new class of phosphate and phosphonate prodrugs, called HepDirect prodrugs, is described that combines properties of rapid liver cleavage with high plasma and tissue stability to achieve increased drug levels in the liver. The prodrugs are substituted cyclic 1,3-propanyl esters designed to undergo an oxidative cleavage reaction catalyzed by a cytochrome P(450) (CYP) expressed predominantly in the liver. Reported herein is the discovery of a prodrug series containing an aryl substituent at C4 and its use for the delivery of nucleoside-based drugs to the liver. Prodrugs of 5'-monophosphates of vidarabine, lamivudine (3TC), and cytarabine as well as the phosphonic acid adefovir were shown to cleave following exposure to liver homogenates and exhibit good stability in blood and other tissues. Prodrug cleavage required the presence of the aryl group in the cis-configuration, but was relatively independent of the nucleoside and absolute stereochemistry at C4. Mechanistic studies suggested that prodrug cleavage proceeded via an initial CYP3A-catalyzed oxidation to an intermediate ring-opened monoacid, which subsequently was converted to the phosph(on)ate and an aryl vinyl ketone by a beta-elimination reaction. Studies in primary rat hepatocytes and normal rats comparing 3TC and the corresponding HepDirect prodrug demonstrated the ability of these prodrugs to effectively bypass the rate-limiting nucleoside kinase step and produce higher levels of the biologically active nucleoside triphosphate.

AMP-activated protein kinase (AMPK) is a heterotrimeric kinase that regulates cellular energy metabolism by affecting energy-consuming pathways such as de novo lipid biosynthesis and glucose production as well as energy-producing pathways such as lipid oxidation and glucose uptake. Accordingly, compounds that activate AMPK represent potential drug candidates for the treatment of hyperlipidemia and type 2 diabetes. Screening of a proprietary library of AMP mimetics identified the phosphonic acid 2 that bears little structural resemblance to AMP but is capable of activating AMPK with high potency (EC50 = 6 nM vs AMP EC50 = 6 μM) and specificity. Phosphonate prodrugs of 2 inhibited de novo lipogenesis in cellular and animal models of hyperlipidemia.

Cytotoxic nucleosides have proven to be ineffective for the treatment of hepatocellular carcinoma (HCC) due, in part, to their inadequate conversion to their active nucleoside triphosphates (NTP) in the liver tumor and high conversion in other tissues. These characteristics lead to poor efficacy, high toxicity, and a drug class associated with an unacceptable therapeutic index. Cyclic 1-aryl-1,3-propanyl phosphate prodrugs selectively release the monophosphate of a nucleoside (NMP) into CYP3A4-expressing cells, such as hepatocytes, while leaving the prodrug intact in plasma and extrahepatic tissues. This prodrug strategy was applied to the monophosphate of the well-known cytotoxic nucleoside cytosine-1-beta-D-arabinofuranoside (cytarabine, araC). Compound 19S (MB07133), in mice, achieves good liver targeting compared to araC, generating >19-fold higher cytarabine triphosphate (araCTP) levels in the liver than levels of araC in the plasma and >12-fold higher araCTP levels in the liver than in the bone marrow, representing a >120-fold and >28-fold improvement, respectively, over araC administration.