Analogs of FTY720 inhibit TRPM7 but not S1PRs and exert multimodal anti-inflammatory effects.

TRPM7, a TRP channel with ion conductance and kinase activities, has emerged as an attractive drug target for immunomodulation. Reverse genetics and cell biological studies have already established a key role for TRPM7 in the inflammatory activation of macrophages. Advancing TRPM7 as a viable molecular target for immunomodulation requires selective TRPM7 inhibitors with in vivo tolerability and efficacy. Such inhibitors have the potential to interdict inflammatory cascades mediated by systemic and tissue-specialized macrophages. FTY720, an FDA-approved drug for multiple sclerosis inhibits TRPM7. However, FTY720 is a prodrug and its metabolite, FTY720-phosphate, is a potent agonist of sphingosine-1-phosphate (S1P) receptors. In this study, we test non-phosphorylatable FTY720 analogs, which are inert against S1PRs and well tolerated in vivo, for activity against TRPM7 and tissue bioavailability. Using patch clamp electrophysiology, we show that VPC01091.4 and AAL-149 block TRPM7 current at low micromolar concentrations. In culture, they act directly on macrophages to blunt LPS-induced inflammatory cytokine expression, though this likely occurrs through multiple molecular targets. We found that VPC01091.4 has significant and rapid accumulation in the brain and lungs, along with direct anti-inflammatory action on alveolar macrophages and microglia. Finally, using a mouse model of endotoxemia, we show VPC01091.4 to be an efficacious anti-inflammatory agent that arrests systemic inflammation in vivo. Together, these findings identify novel small molecule inhibitors that allow TRPM7 channel inhibition independent of S1P receptor targeting which demonstrate potent, polymodal anti-inflammatory activities ex vivo and in vivo.

Imidazole-based sphingosine-1-phosphate transporter Spns2 inhibitors.

Sphingosine-1-phosphate (S1P) is a chemotactic lipid that influences immune cell positioning. S1P concentration gradients are necessary for proper egress of lymphocytes from the thymus and secondary lymphoid tissues. This trafficking is interdicted by S1P receptor modulators, and it is expected that S1P transporter (Spns2) inhibitors, by reshaping S1P concentration gradients, will do the same. We previously reported SLF1081851 as a prototype Spns2 inhibitor, which provided a scaffold to investigate the importance of the oxadiazole core and the terminal amine. In this report, we disclose a structure-activity relationship study by incorporating imidazole as both a linker and surrogate for a positive charge in SLF1081851. In vitro inhibition of Spns2-dependent S1P transport in HeLa cells identified 7b as an inhibitor with an IC50 of 1.4 ± 0.3 µM. The SAR studies reported herein indicate that imidazolium can be a substitute for the terminal amine in SLF1081851 and that Spns2 inhibition is highly dependent on the lipid alkyl tail length.

Novel TRPM7 inhibitors with potent anti-inflammatory effects in vivo.

TRPM7, a TRP channel with ion conductance and kinase activities, has emerged as an attractive drug target for immunomodulation. Reverse genetics and cell biological studies have already established a key role for TRPM7 in the inflammatory activation of macrophages. Advancing TRPM7 as a viable molecular target for immunomodulation requires selective TRPM7 inhibitors with in vivo tolerability and efficacy. Such inhibitors have the potential to interdict inflammatory cascades mediated by systemic and tissue-specialized macrophages. FTY720, an FDA-approved drug for multiple sclerosis inhibits TRPM7. However, FTY720 is a prodrug and its metabolite, FTY720-phosphate, is a potent agonist of sphingosine 1-phosphate (S1P) receptors. In this study, we tested non-phosphorylatable FTY720 analogs, which are inert against S1PRs and well tolerated in vivo , for activity against TRPM7 and tissue bioavailability. Using patch clamp electrophysiology, we show that VPC01091.4 and AAL-149 block TRPM7 current at low micromolar concentrations. In culture, they act directly on macrophages to blunt LPS-induced inflammatory cytokine expression, an effect that is predominantly but not solely mediated by TRPM7. We found that VPC01091.4 has significant and rapid accumulation in the brain and lungs, along with direct anti-inflammatory action on alveolar macrophages and microglia. Finally, using a mouse model of endotoxemia, we show VPC01091.4 to be an efficacious anti-inflammatory agent that arrests systemic inflammation in vivo . Together, these findings identify novel small molecule inhibitors that allow TRPM7 channel inhibition independent of S1P receptor targeting. These inhibitors exhibit potent anti-inflammatory properties that are mediated by TRPM7 and likely other molecular targets that remain to be identified.

Assay of Sphingosine 1-phosphate Transporter Spinster Homolog 2 (Spns2) Inhibitors.

The sphingosine-1-phosphate (S1P) pathway remains an active area of research for drug discovery because S1P modulators are effective medicine for autoimmune diseases such as multiple sclerosis and ulcerative colitis. As such, other nodes in the pathway can be probed for alternative therapeutic candidates. As S1P elicits its function in an 'outside-in' fashion, targeting the transporter, Spns2, which is upstream of the receptors, is of great interest. To support our medicinal chemistry campaign to inhibit S1P transport, we developed a mammalian cell-based assay. In this protocol, Spns2 inhibition is assessed by treating HeLa, U-937, and THP-1 cells with inhibitors and S1P exported in the extracellular milieu is quantified by LC-MS/MS. Our studies demonstrated that the amount of S1P in the media in inversely proportional to inhibitor concentration. The details of our investigations are described herein.

2-Aminobenzoxazole Derivatives as Potent Inhibitors of the Sphingosine-1-Phosphate Transporter Spinster Homolog 2 (Spns2).

The S1P1 receptor is the target of four marketed drugs for the treatment of multiple sclerosis and ulcerative colitis. Targeting an S1P exporter, specifically Spns2, that is "upstream" of S1P receptor engagement is an alternate strategy that might recapitulate the efficacy of S1P receptor modulators without cardiac toxicity. We recently reported the first Spns2 inhibitor SLF1081851 (16d) that has modest potency with in vivo activity. To develop more potent compounds, we initiated a structure-activity relationship study that identified 2-aminobenzoxazole as a viable scaffold. Our studies revealed SLB1122168 (33p), which is a potent inhibitor (IC50 = 94 ± 6 nM) of Spns2-mediated S1P release. Administration of 33p to mice and rats resulted in a dose-dependent decrease in circulating lymphocytes, a pharmacodynamic indication of Spns2 inhibition. 33p provides a valuable tool compound to explore both the therapeutic potential of targeting Spns2 and the physiologic consequences of selective S1P export inhibition.

Sphingosine Kinase 2 Inhibitors: Rigid Aliphatic Tail Derivatives Deliver Potent and Selective Analogues.

Sphingosine 1-phosphate (S1P) is a pleiotropic signaling molecule that interacts with five native G-protein coupled receptors (S1P1-5) to regulate cell growth, survival, and proliferation. S1P has been implicated in a variety of pathologies including cancer, kidney fibrosis, and multiple sclerosis. As key mediators in the synthesis of S1P, sphingosine kinase (SphK) isoforms 1 and 2 have attracted attention as viable targets for pharmacologic intervention. In this report, we describe the design, synthesis, and biological evaluation of sphingosine kinase 2 (SphK2) inhibitors with a focus on systematically introducing rigid structures in the aliphatic lipid tail present in existing SphK2 inhibitors. Experimental as well as molecular modeling studies suggest that conformationally restricted "lipophilic tail" analogues bearing a bulky terminal moiety or an internal phenyl ring are useful to complement the "J"-shaped sphingosine binding pocket of SphK2. We identified 14c (SLP9101555) as a potent SphK2 inhibitor (K i = 90 nM) with 200-fold selectivity over SphK1. Molecular docking studies indicated key interactions: the cyclohexyl ring binding in the cleft deep in the pocket, a trifluoromethyl group fitting in a small side cavity, and a hydrogen bond between the guanidino group and Asp308 (amino acid numbering refers to human SphK2 (isoform c) orthologue). In vitro studies using U937 human histiocytic lymphoma cells showed marked decreases in extracellular S1P levels in response to our SphK2 inhibitors. Administration of 14c (dose: 5 mg/kg) to mice resulted in a sustained increase of circulating S1P levels, suggesting target engagement.

Sphingosine 1-phosphate signaling in perivascular cells enhances inflammation and fibrosis in the kidney.

Chronic kidney disease (CKD), characterized by sustained inflammation and progressive fibrosis, is highly prevalent and can eventually progress to end-stage kidney disease. However, current treatments to slow CKD progression are limited. Sphingosine 1-phosphate (S1P), a product of sphingolipid catabolism, is a pleiotropic mediator involved in many cellular functions, and drugs targeting S1P signaling have previously been studied particularly for autoimmune diseases. The primary mechanism of most of these drugs is functional antagonism of S1P receptor-1 (S1P1) expressed on lymphocytes and the resultant immunosuppressive effect. Here, we documented the role of local S1P signaling in perivascular cells in the progression of kidney fibrosis using primary kidney perivascular cells and several conditional mouse models. S1P was predominantly produced by sphingosine kinase 2 in kidney perivascular cells and exported via spinster homolog 2 (Spns2). It bound to S1P1 expressed in perivascular cells to enhance production of proinflammatory cytokines/chemokines upon injury, leading to immune cell infiltration and subsequent fibrosis. A small-molecule Spns2 inhibitor blocked S1P transport, resulting in suppression of inflammatory signaling in human and mouse kidney perivascular cells in vitro and amelioration of kidney fibrosis in mice. Our study provides insight into the regulation of inflammation and fibrosis by S1P and demonstrates the potential of Spns2 inhibition as a treatment for CKD and potentially other inflammatory and fibrotic diseases that avoids the adverse events associated with systemic modulation of S1P receptors.

A Novel Sphingosine Kinase Inhibitor Suppresses Chikungunya Virus Infection.

Chikungunya virus (CHIKV) is a re-emerging arbovirus in the alphavirus genus. Upon infection, it can cause severe joint pain that can last years in some patients, significantly affecting their quality of life. Currently, there are no vaccines or anti-viral therapies available against CHIKV. Its spread to the Americas from the eastern continents has substantially increased the count of the infected by millions. Thus, there is an urgent need to identify therapeutic targets for CHIKV treatment. A potential point of intervention is the sphingosine-1-phosphate (S1P) pathway. Conversion of sphingosine to S1P is catalyzed by Sphingosine kinases (SKs), which we previously showed to be crucial pro-viral host factor during CHIKV infection. In this study, we screened inhibitors of SKs and identified a novel potent inhibitor of CHIKV infection-SLL3071511. We showed that the pre-treatment of cells with SLL3071511 in vitro effectively inhibited CHIKV infection with an EC50 value of 2.91 µM under both prophylactic and therapeutic modes, significantly decreasing the viral gene expression and release of viral particles. Our studies suggest that targeting SKs is a viable approach for controlling CHIKV replication.

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

Sphingosine 1-phosphate (S1P) is a pleiotropic signaling molecule that interacts with five G-protein-coupled receptors (S1P1-5) to regulate cellular signaling pathways. S1P export is facilitated by Mfsd2b and spinster homologue 2 (Spns2). While mouse genetic studies suggest that Spns2 functions to maintain lymph S1P, Spns2 inhibitors are necessary to understand its biology and to learn whether Spns2 is a viable drug target. Herein, we report a structure-activity relationship study that identified the first Spns2 inhibitor 16d (SLF1081851). In vitro studies in HeLa cells demonstrated that 16d inhibited S1P release with an IC50 of 1.93 µM. Administration of 16d to mice and rats drove significant decreases in circulating lymphocyte counts and plasma S1P concentrations, recapitulating the phenotype observed in mice made deficient in Spns2. Thus, 16d has the potential for development and use as a probe to investigate Spns2 biology and to determine the potential of Spns2 as a drug target.

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

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, and autoimmunity. 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 Ki 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 Ki = 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.

Lipophilic tail modifications of 2-(hydroxymethyl)pyrrolidine scaffold reveal dual sphingosine kinase 1 and 2 inhibitors.

The sphingosine 1-phosphate (S1P) signaling pathway is an attractive target for pharmacological manipulation due to its involvement in cancer progression and immune cell chemotaxis. The synthesis of S1P is catalyzed by the action of sphingosine kinase 1 or 2 (SphK1 or SphK2) on sphingosine and ATP. While potent and selective inhibitors of SphK1 or SphK2 have been reported, development of potent dual SphK1/SphK2 inhibitors are still needed. Towards this end, we report the structure-activity relationship profiling of 2-(hydroxymethyl)pyrrolidine-based inhibitors with 22d being the most potent dual SphK1/SphK2 inhibitor (SphK1 Ki = 0.679 µM, SphK2 Ki = 0.951 µM) reported in this series. 22d inhibited the growth of engineered Saccharomyces cerevisiae and decreased S1P levels in histiocytic lymphoma myeloid cell line (U937 cells), demonstrating inhibition of SphK1 and 2 in vitro. Molecular modeling studies of 22d docked inside the Sph binding pocket of both SphK1 and SphK2 indicate essential hydrogen bond between the 2-(hydroxymethyl)pyrrolidine head to interact with aspartic acid and serine residues near the ATP binding pocket, which provide the basis for dual inhibition. In addition, the dodecyl tail adopts a "J-shape" conformation found in crystal structure of sphingosine bound to SphK1. Collectively, these studies provide insight into the intermolecular interactions in the SphK1 and 2 active sites to achieve maximal dual inhibitory activity.

Mechanism of sphingosine 1-phosphate clearance from blood.

The interplay of sphingosine 1-phosphate (S1P) synthetic and degradative enzymes as well as S1P exporters creates concentration gradients that are a fundamental to S1P biology. Extracellular S1P levels, such as in blood and lymph, are high relative to cellular S1P. The blood-tissue S1P gradient maintains endothelial integrity while local S1P gradients influence immune cell positioning. Indeed, the importance of S1P gradients was recognized initially when the mechanism of action of an S1P receptor agonist used as a medicine for multiple sclerosis was revealed to be inhibition of T-lymphocytes' recognition of the high S1P in efferent lymph. Furthermore, the increase in erythrocyte S1P in response to hypoxia influences oxygen delivery during high altitude acclimatization. However, understanding of how S1P gradients are maintained is incomplete. For example, S1P is synthesized but is only slowly metabolized by blood yet circulating S1P turns over quickly by an unknown mechanism. Prompted by the counterintuitive observation that blood S1P increases markedly in response to inhibition S1P synthesis (by sphingosine kinase 2 (SphK2)), we studied mice wherein several tissues were made deficient in either SphK2 or S1P degrading enzymes. Our data reveal a mechanism whereby S1P is de-phosphorylated at the hepatocyte surface and the resulting sphingosine is sequestered by SphK phosphorylation and in turn degraded by intracellular S1P lyase. Thus, we identify the liver as the primary site of blood S1P clearance and provide an explanation for the role of SphK2 in this process. Our discovery suggests a general mechanism whereby S1P gradients are shaped.

Discovery of a Small Side Cavity in Sphingosine Kinase 2 that Enhances Inhibitor Potency and Selectivity.

The sphingosine-1-phosphate (S1P) signaling pathway is an attractive drug target due to its involvement in immune cell chemotaxis and vascular integrity. The formation of S1P is catalyzed by sphingosine kinase 1 or 2 (SphK1 or SphK2) from sphingosine (Sph) and ATP. Inhibition of SphK1 and SphK2 to attenuate levels of S1P has been reported to be efficacious in animal models of diseases such as cancer, sickle cell disease, and renal fibrosis. While inhibitors of both SphKs have been reported, improvements in potency and selectivity are still needed. Toward that end, we performed structure-activity relationship profiling of 8 (SLM6031434) and discovered a heretofore unrecognized side cavity that increased inhibitor potency toward SphK2. Interrogating this region revealed that relatively small hydrophobic moieties are preferred, with 10 being the most potent SphK2-selective inhibitor (Ki = 89 nM, 73-fold SphK2-selective) with validated in vivo activity.

Correction: Mobilization studies in mice deficient in sphingosine kinase 2 support a crucial role of the plasma level of sphingosine-1-phosphate in the egress of hematopoietic stem progenitor cells.

[This corrects the article DOI: 10.18632/oncotarget.19514.].

Increasing circulating sphingosine-1-phosphate attenuates lung injury during ex vivo lung perfusion.

BACKGROUND: Sphingosine-1-phosphate regulates endothelial barrier integrity and promotes cell survival and proliferation. We hypothesized that upregulation of sphingosine-1-phosphate during ex vivo lung perfusion would attenuate acute lung injury and improve graft function. METHODS: C57BL/6 mice (n = 4-8/group) were euthanized, followed by 1 hour of warm ischemia and 1 hour of cold preservation in a model of donation after cardiac death. Subsequently, mice underwent 1 hour of ex vivo lung perfusion with 1 of 4 different perfusion solutions: Steen solution (Steen, control arm), Steen with added sphingosine-1-phosphate (Steen + sphingosine-1-phosphate), Steen plus a selective sphingosine kinase 2 inhibitor (Steen + sphingosine kinase inhibitor), or Steen plus both additives (Steen + sphingosine-1-phosphate + sphingosine kinase inhibitor). During ex vivo lung perfusion, lung compliance and pulmonary artery pressure were continuously measured. Pulmonary vascular permeability was assessed with injection of Evans Blue dye. RESULTS: The combination of 1 hour of warm ischemia, followed by 1 hour of cold ischemia created significant lung injury compared with lungs that were immediately harvested after circulatory death and put on ex vivo lung perfusion. Addition of sphingosine-1-phosphate or sphingosine kinase inhibitor alone did not significantly improve lung function during ex vivo lung perfusion compared with Steen without additives. However, group Steen + sphingosine-1-phosphate + sphingosine kinase inhibitor resulted in significantly increased compliance (110% ± 13.9% vs 57.7% ± 6.6%, P < .0001) and decreased pulmonary vascular permeability (33.1 ± 11.9 µg/g vs 75.8 ± 11.4 µg/g tissue, P = .04) compared with Steen alone. CONCLUSIONS: Targeted drug therapy with a combination of sphingosine-1-phosphate + sphingosine kinase inhibitor during ex vivo lung perfusion improves lung function in a murine donation after cardiac death model. Elevation of circulating sphingosine-1-phosphate via specific pharmacologic modalities during ex vivo lung perfusion may provide endothelial protection in marginal donor lungs leading to successful lung rehabilitation for transplantation.

Saccharomyces cerevisiae as a platform for assessing sphingolipid lipid kinase inhibitors.

Successful medicinal chemistry campaigns to discover and optimize sphingosine kinase inhibitors require a robust assay for screening chemical libraries and for determining rank order potencies. Existing assays for these enzymes are laborious, expensive and/or low throughput. The toxicity of excessive levels of phosphorylated sphingoid bases for the budding yeast, Saccharomyces cerevisiae, affords an assay wherein inhibitors added to the culture media rescue growth in a dose-dependent fashion. Herein, we describe our adaptation of a simple, inexpensive, and high throughput assay for assessing inhibitors of sphingosine kinase types 1 and 2 as well as ceramide kinase and for testing enzymatic activity of sphingosine kinase type 2 mutants. The assay was validated using recombinant enzymes and generally agrees with the rank order of potencies of existing inhibitors.

Photoacoustic microscopy reveals the hemodynamic basis of sphingosine 1-phosphate-induced neuroprotection against ischemic stroke.

Rationale: Emerging evidence has suggested that sphingosine 1-phosphate (S1P), a bioactive metabolite of sphingolipids, may play an important role in the pathophysiological processes of cerebral hypoxia and ischemia. However, the influence of S1P on cerebral hemodynamics and metabolism remains unclear. Material and Methods: Uniquely capable of high-resolution, label-free, and comprehensive imaging of hemodynamics and oxygen metabolism in the mouse brain without the influence of general anesthesia, our newly developed head-restrained multi-parametric photoacoustic microscopy (PAM) is well suited for this mechanistic study. Here, combining the cutting-edge PAM and a selective inhibitor of sphingosine kinase 2 (SphK2) that can increase the blood S1P level, we investigated the role of S1P in cerebral oxygen supply-demand and its neuroprotective effects on global brain hypoxia induced by nitrogen gas inhalation and focal brain ischemia induced by transient middle cerebral artery occlusion (tMCAO). Results: Inhibition of SphK2, which increased the blood S1P, resulted in the elevation of both arterial and venous sO2 in the hypoxic mouse brain, while the cerebral blood flow remained unchanged. As a result, it gradually and significantly reduced the metabolic rate of oxygen. Furthermore, pre-treatment of the mice subject to tMCAO with the SphK2 inhibitor led to decreased infarct volume, improved motor function, and reduced neurological deficit, compared to the control treatment with a less potent R-enantiomer. In contrast, post-treatment with the inhibitor showed no improvement in the stroke outcomes. The failure for the post-treatment to induce neuroprotection was likely due to the relatively slow hemodynamic responses to the SphK2 inhibitor-evoked S1P intervention, which did not take effect before the brain injury was induced. Conclusions: Our results reveal that elevated blood S1P significantly changes cerebral hemodynamics and oxygen metabolism under hypoxia but not normoxia. The improved blood oxygenation and reduced oxygen demand in the hypoxic brain may underlie the neuroprotective effect of S1P against ischemic stroke.

Mobilization studies in mice deficient in sphingosine kinase 2 support a crucial role of the plasma level of sphingosine-1-phosphate in the egress of hematopoietic stem progenitor cells.

Sphingosine-1-phosphate (S1P) is a bioactive lipid involved in cell signaling and, if released from cells, also plays a crucial role in regulating the trafficking of lympho-hematopoietic cells, including primitive hematopoietic stem/progenitor cells (HSPCs). It has been demonstrated that S1P chemoattracts HSPCs, and its level in peripheral blood creates a gradient directing egress of these cells during mobilization. In this paper we analyzed hematopoiesis in mice deficient in sphingosine kinase 2 (Sphk2-KO mice) and studied the effect of this mutation on plasma S1P levels. We found that Sphk2-KO mice have normal hematopoiesis, and, in contrast to Sphk1-KO mice, the circulating S1P level is highly elevated in these animals and correlates with the fact that HSPCs in Sphk2-KO animals, also in contrast to Sphk1-KO animals, show enhanced mobilization. These results were recapitulated in wild type (WT) animals employing an Sphk2 inhibitor. We also administered an inhibitor of the S1P-degrading enzyme S1P lyase, known as tetrahydroxybutylimidazole (THI), to WT mice and observed that this resulted in an increase in S1P level in PB and enhanced mobilization of HSPCs. In sum, our results support a crucial role for S1P gradients in blood plasma in the mobilization process and indicate that small-molecule inhibitors of Sphk2 and Sgpl1 could be employed as mobilization-facilitating compounds. At the same time, further studies are needed to explain the unexpected effect of Sphk2 inhibition on increasing S1P levels in plasma.

Transforming Sphingosine Kinase 1 Inhibitors into Dual and Sphingosine Kinase 2 Selective Inhibitors: Design, Synthesis, and in Vivo Activity.

Sphingosine 1-phosphate (S1P) is a pleiotropic signaling molecule that interacts with its five G-protein coupled receptors (S1P1-5) to regulate cell growth and survival and has been implicated in a variety of diseases including cancer and sickle cell disease. As the key mediators in the synthesis of S1P, sphingosine kinase (SphK) isoforms 1 and 2 have attracted attention as viable targets for pharmaceutical inhibition. In this article, we describe the design, synthesis, and biological evaluation of aminothiazole-based guanidine inhibitors of SphK. Surprisingly, combining features of reported SphK1 inhibitors generated SphK1/2 dual inhibitor 20l (SLC4011540) (hSphK1 Ki = 120 nM, hSphK2 Ki = 90 nM) and SphK2 inhibitor 20dd (SLC4101431) (Ki = 90 nM, 100-fold SphK2 selectivity). These compounds effectively decrease S1P levels in vitro. In vivo administration of 20dd validated that inhibition of SphK2 increases blood S1P levels.