Hans E. Purkey

Discovery of a Potent and Selective BCL-XL Inhibitor with in Vivo Activity

A-1155463, a highly potent and selective BCL-XL inhibitor, was discovered through nuclear magnetic resonance (NMR) fragment screening and structure-based design. This compound is substantially more potent against BCL-XL-dependent cell lines relative to our recently reported inhibitor, WEHI-539, while possessing none of its inherent pharmaceutical liabilities. A-1155463 caused a mechanism-based and reversible thrombocytopenia in mice and inhibited H146 small cell lung cancer xenograft tumor growth in vivo following multiple doses. A-1155463 thus represents an excellent tool molecule for studying BCL-XL biology as well as a productive lead structure for further optimization.

Identification of substituted 2-thio-6-oxo-1,6-dihydropyrimidines as inhibitors of human lactate dehydrogenase.

A novel 2-thio-6-oxo-1,6-dihydropyrimidine-containing inhibitor of human lactate dehydrogenase (LDH) was identified by high-throughput screening (IC50=8.1 μM). Biochemical, surface plasmon resonance, and saturation transfer difference NMR experiments indicated that the compound specifically associated with human LDHA in a manner that required simultaneous binding of the NADH co-factor. Structural variation of the screening hit resulted in significant improvements in LDHA biochemical inhibition activity (best IC50=0.48 μM). A crystal structure of an optimized compound bound to human LDHA was obtained and explained many of the observed structure-activity relationships.

Identification of substituted 3-hydroxy-2-mercaptocyclohex-2-enones as potent inhibitors of human lactate dehydrogenase.

A novel class of 3-hydroxy-2-mercaptocyclohex-2-enone-containing inhibitors of human lactate dehydrogenase (LDH) was identified through a high-throughput screening approach. Biochemical and surface plasmon resonance experiments performed with a screening hit (LDHA IC50=1.7 μM) indicated that the compound specifically associated with human LDHA in a manner that required simultaneous binding of the NADH co-factor. Structural variation of this screening hit resulted in significant improvements in LDHA biochemical inhibition activity (best IC50=0.18 μM). Two crystal structures of optimized compounds bound to human LDHA were obtained and explained many of the observed structure-activity relationships. In addition, an optimized inhibitor exhibited good pharmacokinetic properties after oral administration to rats (F=45%).

Synthesis, characterization, and PK/PD studies of a series of spirocyclic pyranochromene BACE1 inhibitors.

The development of 1,3,4,4a,5,10a-hexahydropyrano[3,4-b]chromene analogs as BACE1 inhibitors is described. Introduction of the spirocyclic pyranochromene scaffold yielded several advantages over previous generation cores, including increased potency, reduced efflux, and reduced CYP2D6 inhibition. Compound 13 (BACE1 IC50=110 nM) demonstrated a reduction in CSF Aβ in wild type rats after a single dose.

Diethylaminosulfur Trifluoride-Mediated Intramolecular Cyclization of 2-hydroxycycloalkylureas to Fused Bicyclic Aminooxazoline Compounds and Evaluation of Their Biochemical Activity Against β-Secretase-1 (BACE-1)

Abstract A series of unique bicyclic aminooxazolines were synthesized and found to exhibit micromolar inhibition of β-secretase-1 (BACE-1). The aminooxazolines were procured by an intramolecular diethylaminosulfur trifluoride (DAST)-mediated ring closure of a benzylic urea onto a secondary alcohol.

4-Aminoindazolyl-dihydrofuro[3,4-d]pyrimidines as non-covalent inhibitors of mutant epidermal growth factor receptor tyrosine kinase.

The treatment of epidermal growth factor receptor (EGFR)-driven non-small cell lung cancers with the T790M resistance mutation remains a significant unmet medical need. We report the identification of 4-aminoindazolyl-dihydrofuro[3,4-d]pyrimidines as non-covalent inhibitors of EGFR, with excellent activity against the T790M resistance double mutants and initial single activating mutants. Using an optimization strategy focused on structure-based design and improving PK properties through metabolite identification, we obtained advanced leads with high oral exposure.

Abstract 1423: Resistance to LDHA inhibitors requires signaling through the AMPK/mTOR/S6K pathway leading to increased oxidative phosphorylation

Lactate Dehydrogenase A (LDHA) is an attractive candidate for targeting glycolysis-addicted tumors. However, due to the inherent plasticity of metabolic networks in cells, there is concern that the benefit of targeting LDHA may be transient and that resistance will quickly emerge. To identify predictive features of LHDA inhibitor sensitivity and to understand how cells adapt to long-term LHDA inhibition, we screened a large panel (∼500) of tumor cell lines with GNE-140, a newly developed LHDA inhibitor. We found that approximately 15% of lines were inherently sensitive to the LDHA inhibitor, with sensitivity correlating with increased expression of glycolysis genes and inversely correlating with expression of oxidative phosphorylation genes. Despite the metabolic plasticity of cells, the timing of acquired resistance to LDHA inhibitors was comparable with other targeted agents. Under long-term LDHAi treatment, glycolytic cells acquired resistance by increased oxidative phosporylation (OX-PHOS) in a mechanism dependent on the AMPK stress response pathway; targeting either AMPK, downstream kinases, or OX-PHOS using tool compounds synergized with and prevented acquired resistance to GNE-140. Taken together, our data suggests that targeting anaerobic glycolysis may benefit a subset of patients across indications and that combinations with agents that block AMPK signaling or the mitochondria will be effective at delaying tumor relapse. Citation Format: Aaron Boudreau, David Peterson, John Moffat, Bonnie Liu, Mandy Kwong, Min Gao, Hans Purkey, Thomas O9Brien, Georgia Hatzivassiliou, Anneleen Daemen, Marie Evangelista. Resistance to LDHA inhibitors requires signaling through the AMPK/mTOR/S6K pathway leading to increased oxidative phosphorylation. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1423. doi:10.1158/1538-7445.AM2014-1423