Sphingosine-1-phosphate (S1P) synthesized by sphingosine kinase (SPHK) is a signaling molecule, involved in cell proliferation, growth, differentiation, and survival. Indeed, a sharp increase of S1P is linked to a pathological outcome with inflammation, cancer metastasis, or angiogenesis, etc. In this regard, SPHK/S1P axis regulation has been a specific issue in the anticancer strategy to turn accumulated sphingosine (SPN) into cytotoxic ceramides (Cers). For these purposes, there have been numerous chemicals synthesized for SPHK inhibition. In this study, we investigated the comparative efficiency of dansylated PF-543 (DPF-543) on the Cers synthesis along with PF-543. DPF-543 deserved attention in strong cytotoxicity, due to the cytotoxic Cers accumulation by ceramide synthase (CerSs). DPF-543 exhibited dual actions on Cers synthesis by enhancing serine palmitoyltransferase (SPT) activity, and by inhibiting SPHKs, which eventually induced an unusual environment with a high amount of 3-ketosphinganine and sphinganine (SPA). SPA in turn was consumed to synthesize Cers via de novo pathway. Interestingly, PF-543 increased only the SPN level, but not for SPA. In addition, DPF-543 mildly activates acid sphingomyelinase (aSMase), which contributes a partial increase in Cers. Collectively, a dansyl-modified DPF-543 relatively enhanced Cers accumulation via de novo pathway which was not observed in PF-543. Our results demonstrated that the structural modification on SPHK inhibitors is still an attractive anticancer strategy by regulating sphingolipid metabolism.

This study intends to develop an essential simultaneous analysis method for the stability study of the combination drugs hydrochlorothiazide, (S)-amlodipine besylate, and olmesartan medoxomil and identify degradation products. A stress test of the combination drug was performed under thermal/humidity conditions to identify decomposition products expected to be generated under long-term storage conditions. Six unidentified degradation products were generated from (S)-amlodipine besylate and olmesartan medoxomil, except for those identified.Unspecified degradation products were identified by degradation prediction software with LC-MS/MS, and genotoxicity was predicted by toxicity prediction software. In silico toxicity, six degradation products were expected to be nonmutagenic. This study describes the development of an analytical method to predict degradation products and determine whether the degradation products are genotoxic. This process will be helpful in further forced degradation studies to predict the toxicity of potential impurities.