Insights into the Novel Hydrolytic Mechanism of a Diethyl 2‑Phenyl-2-(2-arylacetoxy)methyl Malonate Ester-Based Microsomal Triglyceride Transfer Protein (MTP) Inhibitor

Inhibition of intestinal and hepatic microsomal triglyceride transfer protein (MTP) is a potential strategy for the treatment of dyslipidemia and related metabolic disorders. Inhibition of hepatic MTP, however, results in elevated liver transaminases and increased hepatic fat deposition consistent with hepatic steatosis. Diethyl 2-((2-(3-(dimethylcarbamoyl)-4-(4′-(trifluoromethyl)-[1,1′-biphenyl]-2-ylcarboxamido)­phenyl)­acetoxy)­methyl)-2-phenylmalonate (JTT-130) is an intestine-specific inhibitor of MTP and does not cause increases in transaminases in short-term clinical trials in patients with dyslipidemia. Selective inhibition of intestinal MTP is achieved via rapid hydrolysis of its ester linkage by liver-specific carboxylesterase(s), resulting in the formation of an inactive carboxylic acid metabolite <b>1</b>. In the course of discovery efforts around tissue-specific inhibitors of MTP, the mechanism of JTT-130 hydrolysis was examined in detail. Lack of ¹⁸O incorporation in <b>1</b> following the incubation of JTT-130 in human liver microsomes in the presence of H₂¹⁸O suggested that hydrolysis did not occur via a simple cleavage of the ester linkage. The characterization of atropic acid (2-phenylacrylic acid) as a metabolite was consistent with a hydrolytic pathway involving initial hydrolysis of one of the pendant malonate ethyl ester groups followed by decarboxylative fragmentation to <b>1</b> and the concomitant liberation of the potentially electrophilic acrylate species. Glutathione conjugates of atropic acid and its ethyl ester were also observed in microsomal incubations of JTT-130 that were supplemented with the thiol nucleophile. Additional support for the hydrolysis mechanism was obtained from analogous studies on diethyl 2-(2-(2-(3-(dimethylcarbamoyl)-4-(4′-trifluoromethyl)-[1,1′-biphenyl]-2-ylcarboxamido)­phenyl)­acetoxy)­ethyl)-2-phenylmalonate (<b>3</b>), which cannot participate in hydrolysis via the fragmentation pathway because of the additional methylene group. Unlike the case with JTT-130, ¹⁸O was readily incorporated into <b>1</b> during the enzymatic hydrolysis of <b>3</b>, suggestive of a mechanism involving direct hydrolytic cleavage of the ester group in <b>3</b>. Finally, 3-(ethylamino)-2-(ethylcarbamoyl)-3-oxo-2-phenylpropyl 2-(3-(dimethylcarbamoyl)-4-(4′-(trifluoromethyl)-[1,1′-biphenyl]-2-ylcarboxamido)­phenyl)­acetate (<b>4</b>), which possessed an <i>N</i>,<i>N</i>-diethyl-2-phenylmalonamide substituent (in lieu of the diethyl-2-phenylmalonate motif in JTT-130) proved to be resistant to the hydrolytic cleavage/decarboxylative fragmentation pathway that yielded <b>1</b>, a phenomenon that further confirmed our hypothesis. From a toxicological standpoint, it is noteworthy to point out that the liberation of the electrophilic acrylic acid species as a byproduct of JTT-130 hydrolysis is similar to the bioactivation mechanism established for felbamate, an anticonvulsant agent associated with idiosyncratic aplastic anemia and hepatotoxicity

Discovery of Orally Bioavailable Selective Inhibitors of the Sodium-Phosphate Cotransporter NaPi2a (SLC34A1)

Sodium-phosphate cotransporter 2a, or NaPi2a (SLC34A1), is a solute-carrier (SLC) transporter located in the kidney proximal tubule that reabsorbs glomerular-filtered phosphate. Inhibition of NaPi2a may enhance urinary phosphate excretion and correct maladaptive mineral and hormonal derangements associated with increased cardiovascular risk in chronic kidney disease–mineral and bone disorder (CKD-MBD). To date, only nonselective NaPi inhibitors have been described. Herein, we detail the discovery of the first series of selective NaPi2a inhibitors, resulting from optimization of a high-throughput screening hit. The oral PK profile of inhibitor PF-06869206 (<b>6f</b>) in rodents allows for the exploration of the pharmacology of selective NaPi2a inhibition

Discovery and Preclinical Characterization of 6‑Chloro-5-[4-(1-hydroxycyclobutyl)phenyl]‑1<i>H</i>‑indole-3-carboxylic Acid (PF-06409577), a Direct Activator of Adenosine Monophosphate-activated Protein Kinase (AMPK), for the Potential Treatment of Diabetic Nephropathy

Adenosine monophosphate-activated protein kinase (AMPK) is a protein kinase involved in maintaining energy homeostasis within cells. On the basis of human genetic association data, AMPK activators were pursued for the treatment of diabetic nephropathy. Identification of an indazole amide high throughput screening (HTS) hit followed by truncation to its minimal pharmacophore provided an indazole acid lead compound. Optimization of the core and aryl appendage improved oral absorption and culminated in the identification of indole acid, PF-06409577 (<b>7</b>). Compound <b>7</b> was advanced to first-in-human trials for the treatment of diabetic nephropathy

Evolution of the Synthesis of AMPK Activators for the Treatment of Diabetic Nephropathy: From Three Preclinical Candidates to the Investigational New Drug PF-06409577

Indole acids <b>1</b>, <b>2</b>, and <b>3</b> are potent 5′-adenosine monophosphate-activated protein kinase (AMPK) activators for the potential treatment of diabetic nephropathy. Compounds <b>1</b>–<b>3</b> were scaled to supply material for preclinical studies, and indole <b>3</b> was selected for advancement to first-in-human clinical trials and scaled to kilogram quantities. The progression of the synthesis strategy for these AMPK activators is described, as routes were selected for efficient structure–activity relationship generation and then improved for larger scales. The developed sequences employed practical isolations of intermediates and APIs, reproducible cross-coupling, hydrolysis, and other transformations, and enhanced safety and purity profiles and led to the production of 40–50 g of <b>1</b> and <b>2</b> and 2.4 kg of <b>3</b>. Multiple polymorphs of <b>3</b> were observed, and conditions for the reproducible formation of crystalline material suitable for clinical development were identified

Evolution of the Synthesis of AMPK Activators for the Treatment of Diabetic Nephropathy: From Three Preclinical Candidates to the Investigational New Drug PF-06409577

Indole acids <b>1</b>, <b>2</b>, and <b>3</b> are potent 5′-adenosine monophosphate-activated protein kinase (AMPK) activators for the potential treatment of diabetic nephropathy. Compounds <b>1</b>–<b>3</b> were scaled to supply material for preclinical studies, and indole <b>3</b> was selected for advancement to first-in-human clinical trials and scaled to kilogram quantities. The progression of the synthesis strategy for these AMPK activators is described, as routes were selected for efficient structure–activity relationship generation and then improved for larger scales. The developed sequences employed practical isolations of intermediates and APIs, reproducible cross-coupling, hydrolysis, and other transformations, and enhanced safety and purity profiles and led to the production of 40–50 g of <b>1</b> and <b>2</b> and 2.4 kg of <b>3</b>. Multiple polymorphs of <b>3</b> were observed, and conditions for the reproducible formation of crystalline material suitable for clinical development were identified

Discovery of Fragment-Derived Small Molecules for in Vivo Inhibition of Ketohexokinase (KHK)

Increased fructose consumption and its subsequent metabolism have been implicated in hepatic steatosis, dyslipidemia, obesity, and insulin resistance in humans. Since ketohexokinase (KHK) is the principal enzyme responsible for fructose metabolism, identification of a selective KHK inhibitor may help to further elucidate the effect of KHK inhibition on these metabolic disorders. Until now, studies on KHK inhibition with small molecules have been limited due to the lack of viable in vivo pharmacological tools. Herein we report the discovery of <b>12</b>, a selective KHK inhibitor with potency and properties suitable for evaluating KHK inhibition in rat models. Key structural features interacting with KHK were discovered through fragment-based screening and subsequent optimization using structure-based drug design, and parallel medicinal chemistry led to the identification of pyridine <b>12</b>

Optimization of Metabolic and Renal Clearance in a Series of Indole Acid Direct Activators of 5′-Adenosine Monophosphate-Activated Protein Kinase (AMPK)

Optimization of the pharmacokinetic (PK) properties of a series of activators of adenosine monophosphate-activated protein kinase (AMPK) is described. Derivatives of the previously described 5-aryl-indole-3-carboxylic acid clinical candidate (<b>1</b>) were examined with the goal of reducing glucuronidation rate and minimizing renal excretion. Compounds <b>10</b> (PF-06679142) and <b>14</b> (PF-06685249) exhibited robust activation of AMPK in rat kidneys as well as desirable oral absorption, low plasma clearance, and negligible renal clearance in preclinical species. A correlation of in vivo renal clearance in rats with in vitro uptake by human and rat renal organic anion transporters (human OAT/rat Oat) was identified. Variation of polar functional groups was critical to mitigate active renal clearance mediated by the Oat3 transporter. Modification of either the 6-chloroindole core to a 4,6-difluoroindole or the 5-phenyl substituent to a substituted 5-(3-pyridyl) group provided improved metabolic stability while minimizing propensity for active transport by OAT3

Optimization of Metabolic and Renal Clearance in a Series of Indole Acid Direct Activators of 5′-Adenosine Monophosphate-Activated Protein Kinase (AMPK)

Optimization of the pharmacokinetic (PK) properties of a series of activators of adenosine monophosphate-activated protein kinase (AMPK) is described. Derivatives of the previously described 5-aryl-indole-3-carboxylic acid clinical candidate (<b>1</b>) were examined with the goal of reducing glucuronidation rate and minimizing renal excretion. Compounds <b>10</b> (PF-06679142) and <b>14</b> (PF-06685249) exhibited robust activation of AMPK in rat kidneys as well as desirable oral absorption, low plasma clearance, and negligible renal clearance in preclinical species. A correlation of in vivo renal clearance in rats with in vitro uptake by human and rat renal organic anion transporters (human OAT/rat Oat) was identified. Variation of polar functional groups was critical to mitigate active renal clearance mediated by the Oat3 transporter. Modification of either the 6-chloroindole core to a 4,6-difluoroindole or the 5-phenyl substituent to a substituted 5-(3-pyridyl) group provided improved metabolic stability while minimizing propensity for active transport by OAT3