Alexander J. Pickrell

Structure-guided design of substituted aza-benzimidazoles as potent hypoxia inducible factor-1α prolyl hydroxylase-2 inhibitors

We report the structure-based design and synthesis of a novel series of aza-benzimidazoles as PHD2 inhibitors. These efforts resulted in compound 22, which displayed highly potent inhibition of PHD2 function in vitro.

Discovery of a Potent, S1P3-Sparing Benzothiazole Agonist of Sphingosine-1-Phosphate Receptor 1 (S1P1).

Optimization of a benzofuranyl S1P1 agonist lead compound (3) led to the discovery of 1-(3-fluoro-4-(5-(2-fluorobenzyl)benzo[d]thiazol-2-yl)benzyl)azetidine-3-carboxylic acid (14), a potent S1P1 agonist with minimal activity at S1P3. Dosed orally at 0.3 mg/kg, 14 significantly reduced blood lymphocyte counts 24 h postdose and attenuated a delayed type hypersensitivity (DTH) response to antigen challenge.

4-Methoxy-N-[2-(trifluoromethyl)biphenyl-4-ylcarbamoyl]nicotinamide: A Potent and Selective Agonist of S1P1

The sphingosine-1-phosphate-1 receptor (S1P1) and its endogenous ligand sphingosine-1-phosphate (S1P) cooperatively regulate lymphocyte trafficking from the lymphatic system. Herein, we disclose 4-methoxy-N-[2-(trifluoromethyl)biphenyl-4-ylcarbamoyl]nicotinamide (8), an uncommon example of a synthetic S1P1 agonist lacking a polar headgroup, which is shown to effect dramatic reduction of circulating lymphocytes (POC = -78%) in rat 24 h after a single oral dose (1 mg/kg). The excellent potency that 8 exhibits toward S1P1 (EC50 = 0.035 μM, 96% efficacy) and the >100-fold selectivity that it displays against receptor subtypes S1P2-5 suggest that it may serve as a valuable tool to understand the clinical relevance of selective S1P1 agonism.

Optimization of a Potent, Orally Active S1P1 Agonist Containing a Quinolinone Core

The optimization of a series of S1P1 agonists with limited activity against S1P3 is reported. A polar headgroup was used to improve the physicochemical and pharmacokinetic parameters of lead quinolinone 6. When dosed orally at 1 and 3 mg/kg, the azahydroxymethyl analogue 22 achieved statistically significant lowering of circulating blood lymphocytes 24 h postdose. In rats, a dose-proportional increase in exposure was measured when 22 was dosed orally at 2 and 100 mg/kg.

Synthesis and preliminary biological evaluation of potent and selective 2-(3-alkoxy-1-azetidinyl) quinolines as novel PDE10A inhibitors with improved solubility.

We report the discovery of a novel series of 2-(3-alkoxy-1-azetidinyl) quinolines as potent and selective PDE10A inhibitors. Structure-activity studies improved the solubility (pH 7.4) and maintained high PDE10A activity compared to initial lead compound 3, with select compounds demonstrating good oral bioavailability. X-ray crystallographic studies revealed two distinct binding modes to the catalytic site of the PDE10A enzyme. An ex vivo receptor occupancy assay in rats demonstrated that this series of compounds covered the target within the striatum.

Quinolinone-based agonists of S1P1: Use of a N-scan SAR strategy to optimize in vitro and in vivo activity

We reveal how a N-scan SAR strategy (systematic substitution of each CH group with a N atom) was employed for quinolinone-based S1P(1) agonist 5 to modulate physicochemical properties and optimize in vitro and in vivo activity. The diaza-analog 17 displays improved potency (hS1P(1) RI; 17: EC(50)=0.020 μM, 120% efficacy; 5: EC(50)=0.070 μM, 110% efficacy) and selectivity (hS1P(3) Ca(2+) flux; 17: EC(50) >25 μM; 5: EC(50)=1.5 μM, 92% efficacy), as well as enhanced pharmacokinetics (17: CL=0.15 L/h/kg, V(dss)=5.1L/kg, T(1/2)=24h, %F=110; 5: CL=0.93L/h/kg, V(dss)=11L/kg, T(1/2)=15 h, %F=60) and pharmacodynamics (17: 1.0mg/kg po, 24h PLC POC=-67%; 5: 3mg/kg po, 24h PLC POC=-51%) in rat.

Isoform-selective thiazolo[5,4-b]pyridine S1P1 agonists possessing acyclic amino carboxylate head-groups.

Replacement of the azetidine carboxylate of an S1P(1) agonist development candidate, AMG 369, with a range of acyclic head-groups led to the identification of a novel, S1P(3)-sparing S1P(1) agonist, (-)-2-amino-4-(3-fluoro-4-(5-(1-phenylcyclopropyl)thiazolo[5,4-b]pyridin-2-yl)phenyl)-2-methylbutanoic acid (8c), which possessed good in vivo efficacy and pharmacokinetic properties. A 0.3mg/kg oral dose of 8c produced a statistically significant reduction in blood lymphocyte counts 24h post-dosing in female Lewis rats.

Abstract 711: Small molecule compounds that target cell division cycle 7 (Cdc7) kinase inhibit cell proliferation and tumor growth.

Cdc7 is an essential, serine/threonine protein kinase that activates the initiation of DNA synthesis at replication origins. Cdc7 also promotes cell cycle checkpoint activation in response to replication stress. As a key regulator of S phase entry and progression, Cdc7 kinase is a potential target for cancer therapy, with a distinct mechanism of action from known drugs that inhibit DNA replication. Following a high throughput screen for inhibitors of Cdc7 kinase activity, we investigated structure-activity relationships of azole-based compounds and optimized the compounds for potency and pharmacokinetic properties. Here we present the characterization of one of these compounds as a potent, selective, bioavailable Cdc7 kinase inhibitor. In cells, Cdc7 inhibition decreases MCM2 phosphorylation and DNA synthesis, causes DNA damage, and slows S phase progression. Cdc7 inhibition also induces chromosome missegregation leading to cell lethality in vitro and tumor growth inhibition in vivo. Cdc7 inhibition provides a new approach to target cancers, either as a single agent or in combination with chemotherapy. Citation Format: Julie Bailis, Li Fang, Jessica Orf, Scott Heller, Tammy Bush, Matthew Bourbeau, Sonia Escobar, Michael Frohn, Paul Harrington, Faye Hsieh, Alexander Pickrell, Kelvin Sham, Aaron Siegmund, Helming Tan, Leeanne Zalameda, John Allen, Dineli Wickramasinghe. Small molecule compounds that target cell division cycle 7 (Cdc7) kinase inhibit cell proliferation and tumor growth. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 711. doi:10.1158/1538-7445.AM2013-711