Discovery of Novel, Orally Bioavailable Pyrimidine Ether-Based Inhibitors of ELOVL1

In our efforts to identify novel small molecule inhibitors for the treatment of adrenoleukodystrophy (ALD), we conducted a high-throughput radiometric screen for inhibitors of elongation of very long chain fatty acid 1 (ELOVL1) enzyme. We developed a series of highly potent, central nervous system (CNS)-penetrant pyrimidine ether-based compounds with favorable pharmacokinetics culminating in compound 22. Compound 22 is a selective inhibitor of ELOVL1, reducing C26:0 VLCFA synthesis in ALD patient fibroblasts and lymphocytes in vitro. Compound 22 reduced C26:0 lysophosphatidyl choline (LPC), a subtype of VLCFA, in the blood of ATP binding cassette transporter D1 (ABCD1) KO mice, a murine model of ALD to near wild-type levels. Compound 22 is a low-molecular-weight, potent ELOVL1 inhibitor that may serve as a useful tool for exploring therapeutic approaches to the treatment of ALD.

Abstract LB-B15: A novel PI3K gamma isoform selective small molecule kinase inhibitor demonstrates single agent anti-tumor activity and enhanced combination activity with checkpoint blockade in syngeneic mouse models of cancer

Immune checkpoint inhibitors have generated impressive clinical responses, however, a number of patients and cancer types remain resistant to checkpoint blockade. Immunosuppressive cells such as Tregs and MDSCs in the tumor microenvironment are hypothesized to mediate this resistance. The gamma (γ) isoform of PI3K has long been known to modulate myeloid and lymphocyte cell migration and function, including trafficking of monocytic and granulocytic cells into inflamed tissues such as tumors. Here we report the identification and characterization of BVD-723, a PI3Kγ selective small molecule kinase inhibitor which demonstrated single agent and enhanced combination anti-tumor activity[xx]with either an anti-PD-1 or anti-CTLA-4 antibody. In a mouse syngeneic colon cancer model,[xx]BVD-723 in combination with anti-PD-1 or anti-CTLA-4 resulted in complete regression[xx]of tumors in 35% (7/20) and 60% (12/20) of animals treated with each antibody respectively [versus 0% (0/20) and 5% (1/20) with either antibody alone]. Interestingly, the anti-tumor activity was coupled with a decrease in tumor infiltrating Tregs, granulocytic MDSCs, CD4+ T cells and an increase in the CD8+/Treg ratio, suggesting that inhibition of PI3Kγ by BVD-723 promotes immune-reactivation in the tumor microenvironment. Additionally, BVD-723 demonstrated potent synergy with an anti-PD-1 antibody in a syngeneic mouse model of lymphoma. Single agent BVD-723 activity was also observed in syngeneic mouse models of pancreas, colon, lymphoma and bladder cancers. Results from completed safety pharmacology, toxicology and in vivo efficacy studies support clinical evaluation of BVD-723[xx]as a monotherapy or in combination with the checkpoint inhibitors in cancer.[xx]

Citation Format: Saurabh Saha, Linping Zhang, Thomas Hoock, Alex Aronov, Sudipta Mahajan, Michael Boyd, Jon Come, Veronique Damagnez, Wojciech Dworakowski, Suvarna Khare-Pandit, Arnaud LeTiran, Cameron Moody, Harwin O'Dowd, Joseph Prezioso, Setu Roday, Xiaoyan M. Zhang. A novel PI3K gamma isoform selective small molecule kinase inhibitor demonstrates single agent anti-tumor activity and enhanced combination activity with checkpoint blockade in syngeneic mouse models of cancer. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2015 Nov 5-9; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2015;14(12 Suppl 2):Abstract nr LB-B15.

A Three-Hybrid Approach to Scanning the Proteome for Targets of Small Molecule Kinase Inhibitors

In this study, we explored the application of a yeast three-hybrid (Y3H)-based compound/protein display system to scanning the proteome for targets of kinase inhibitors. Various known cyclin-dependent kinase (CDK) inhibitors, including purine and indenopyrazole analogs, were displayed in the form of methotrexate-based hybrid ligands and deployed in cDNA library or yeast cell array-based screening formats. For all inhibitors, known cell cycle CDKs as well as novel candidate CDK-like and/or CDK-unrelated kinase targets could be identified, many of which were independently confirmed using secondary enzyme assays and affinity chromatography. The Y3H system described here may prove generally useful in the discovery of candidate drug targets.

Small-molecule immunostimulants. Synthesis and activity of 7,8-disubstituted guanosines and structurally related compounds

A series of 7,8-disubstituted guanosine derivatives was designed and prepared as potential B-cell-selective activators of the humoral immune response. These compounds were evaluated for their ability to act as B-cell mitogens and to augment the antibody response of B cells to sheep red blood cell (SRBC) challenge (adjuvanticity). In addition, they were tested for their ability to stimulate the natural killer (NK) cell response in murine in vitro cell assays. Certain of the compounds demonstrated in vivo activity when administered either intravenously, subcutaneously, or orally. Analogues with a medium-length alkyl chain (2-4 carbons, 5-7) on the 7-position of 7-alkyl-8-oxoguanosines were found to be particularly potent. Compounds bearing hydroxyalkyl, aminoalkyl, or substituted aminoalkyl substituents on this 7-position were weakly active. However, benzyl groups, including those substituted with heteroatoms (e.g., p-nitrobenzyl, 14), were active. Oxo, thioxo, and seleno groups on C-8 of the guanosine ring all imparted strong activity, whereas other larger substituents did not (e.g., N = CN). Stereochemical inversion of the 2'-hydroxyl on the ribose ring in this series, giving arabinose analogue 70, lessened activity. However, removal of the 2'-hydroxyl, either with (64) or without (73) removal of the 3'-hydroxyl, resulted in excellent activity and improved solubility; 64 also displayed good oral in vivo activity as well. A series of ketals involving the 2',3'-hydroxyls were prepared; certain of the nonpolar ketals (e.g., 48) were remarkably active, pointing to an ancillary hydrophobic binding region that can augment activity. 5'-Phosphate derivative 57 was fairly active, and acyclovir analogue 90 displayed good NK-selective activity: other N-9 sugar mimetics were also active (97-104), although this activity did not carry over into the human B-cell assay. A total of 80 compounds were prepared and evaluated for their immunostimulating activity. Within this group, compounds could be divided into those that were active in all three assays, those that displayed some measure of selectivity for the adjuvanticity assay, and those that preferentially activated NK responses. Because of its overall biological profile and ease of synthesis, 7-allyl-8-oxoguanosine (6; loxoribine, RWJ-21757) was chosen for further development. It is among the most potent compounds evaluated in the three biological assays.