Nucleosides, Nucleotides & Nucleic Acids, 2022
We report the synthesis and cytotoxicity in MCF-7 and MDA-MB-231 breast cancer cells of novel 1,2,3- and 1,2,4-triazolyl analogs of ribavirin. We modified ribavirin’s carboxamide moiety to test the effects of lipophilic groups. 1-β-D-Ribofuranosyl-1H-1,2,3-triazoles were prepared using Click Chemistry, whereas an unprecedented application of a prior 1,2,4-triazole ring synthesis was used for 1-β-D-ribofuranosyl-1H-1,2,4-triazole analogs. Though cytotoxicity was mediocre and there was no correlation with lipophilicity, we discovered that a structurally similar concentrative nucleoside transporter 2 (CNT2) inhibitor was modestly cytotoxic (MCF-7 IC50 of 42 µM). These syntheses could be used to efficiently investigate variation in the nucleobase.
The L‐type amino acid transporter 1 (LAT1, SLC7A5) imports dietary amino acids and amino acid drugs (e.g. L‐DOPA) into the brain, and it plays a role in cancer metabolism. Though there have been numerous reports of LAT1‐targeted amino acid‐drug conjugates (prodrugs), identifying the structural determinants to enhance substrate activity has been challenging. In this work, we investigated the position and orientation of a carbonyl group in linking hydrophobic moieties including the anti‐inflammatory drug ketoprofen to L‐tyrosine and L‐phenylalanine. We found that esters of meta‐carboxyl L‐phenylalanine had better LAT1 transport rates than the corresponding acylated L‐tyrosine analogs. However, as the size of the hydrophobic moiety increased, we observed a decrease in LAT1 transport rate with a concomitant increase in potency of inhibition. Our results have important implications for designing amino acid prodrugs that target LAT1 at the blood‐brain barrier (BBB) or on cancer cells.
A series of 1,2,3-triazole analogs of the amino acids L-histidine and L-tryptophan were modeled, synthesized and tested for L-type amino acid transporter 1 (LAT1; SLC7A5) activity to guide the design of amino acid-drug conjugates (prodrugs). These triazoles were conveniently prepared by the highly convergent Huisgen 1,3-dipolar cycloaddition (Click Chemistry). Despite comparable predicted binding modes, triazoles generally demonstrated reduced cell uptake and LAT1 binding potency relative to their natural amino acid counterparts. The structure-activity relationship (SAR) data for these triazoles has important ramifications for treating cancer and brain disorders using amino acid prodrugs or LAT1 inhibitors.
Journal of Medicinal Chemistry 2018, 61, 7358-73.
The L-type amino acid transporter 1 (LAT1, SLC7A5) transports essential amino acids across the blood–brain barrier (BBB) and into cancer cells. To utilize LAT1 for drug delivery, potent amino acid promoieties are desired, as prodrugs must compete with millimolar concentrations of endogenous amino acids. To better understand ligand–transporter interactions that could improve potency, we developed structural LAT1 models to guide the design of substituted analogues of phenylalanine and histidine. Furthermore, we evaluated the structure–activity relationship (SAR) for both enantiomers of naturally occurring LAT1 substrates. Analogues were tested in cis-inhibition and trans-stimulation cell assays to determine potency and uptake rate. Surprisingly, LAT1 can transport amino acid-like substrates with wide-ranging polarities including those containing ionizable substituents. Additionally, the rate of LAT1 transport was generally nonstereoselective even though enantiomers likely exhibit different binding modes. Our findings have broad implications to the development of new treatments for brain disorders and cancer.