Probing the substitution pattern of indole-based scaffold reveals potent and selective sphingosine kinase 2 inhibitors

Abstract

Elevated levels of sphingosine 1-phosphate (S1P) and increased expression of sphingosine kinase isoforms (SphK1 and SphK2) have been implicated in a variety of disease states including cancer, inflammation, autoimmunity, among others. Consequently, the S1P signaling axis has become an attractive target for drug discovery. Selective inhibition of either SphK1 or SphK2 has been demonstrated to be effective in modulating S1P levels in animal models. While SphK1 inhibitors have received much attention, the development of potent and selective SphK2 inhibitors are emerging. Previously, our group reported a SphK2 naphthalene-based selective inhibitor, SLC5081308, which displays approximately 7-fold selectivity for hSphK2 over hSphK1 and has a SphK2 K i value of 1.0 μM. To improve SphK2 potency and selectivity, we designed, synthesized, and evaluated a series of indole-based compounds derived from SLC5081308. After investigating substitution patterns around the indole ring, we discovered that 1,5-disubstitution promoted optimal binding in the SphK2 substrate binding site and subsequent inhibition of enzymatic activity. Our studies led to the identification of SLC5101465 (6r, SphK2 K i = 90 nM, >110 fold selective for SphK2 over SphK1). Molecular modeling studies revealed key nonpolar interactions with Val308, Phe548, His556, and Cys533 and hydrogen bonds with both Asp211 and Asp308 as responsible for the high SphK2 inhibition and selectivity.

Discovery of In Vivo Active Sphingosine-1-phosphate Transporter (Spns2) Inhibitors

“…To discover Spns2 inhibitors, we screened an in-house library of sphingosine kinase (SphK) − inhibitors using a yeast (Saccharomyces cerevisiae) assay adapted from a previously reported SphK assay . Although the yeast-based assay ultimately proved problematic for screening (nonspecific cytotoxicity of test compounds), we were able to use the assay to identify one hit ( 11 , Figure ), which is a guanidine-containing oxadiazole derivative .…”

“…1 H NMR (500 MHz, CD 3 OD): δ 8.00−7.78 (m, 3H), 7.47 (d, J = 8.2 Hz, 2H), 7.17 (d, J = 8.2 Hz, 2H), 2.60 (t, J = 7.7 Hz, 2H), 1.61 (p, J = 7.4 Hz, 2H), 1.39−1.23 (m, 14H), 0.89 (t, J = 6.8 Hz, 3H). 13 (37). Synthesized according to General Procedure 7.…”

A Novel Sphingosine Kinase Inhibitor Suppresses Chikungunya Virus Infection

“…As we have previously determined sphingosine kinase importance during CHIKV infection, we investigated the effects of a library of sphingosine kinase inhibitors for their activity during CHIKV infection (Figure 1) [39,40,[42][43][44][45]. To assay for their activity against CHIKV, we pre-treated the HeLa cells with the compounds (20 µM) for one hour prior to infection with CHIKV (MOI = 1) for 24 h. We then used the immunofluorescence assay to detect the viral protein (nsP3) expression, followed by the measurement of nsP3 expression as a read-out of anti-CHIKV activity.…”