Sulfonatoproxylated cucurbit[7]urils as highly water-soluble and biocompatible excipients for solubilizing poorly soluble drugs and improving the bioavailability of indomethacin

The ongoing development of small molecule drugs underscores the urgent need for novel excipients to formulate poorly soluble drug candidates. Cucurbit[7]uril (CB[7]) possesses high binding affinities for a variety of molecular guests. However, its moderate water solubility limits broader application. Here we report the synthesis of three CB[7] derivatives M1-M3 by modifying an average of 4.2, 5.5, and 5.9 sulfonatopropoxy groups onto their “equator” carbons. Compared to CB[7], their water-solubility increased by at least 26.6-, 23.6-, and 19.2-fold, respectively, while the maximum tolerated doses (MTD) of M1 and M2 improved by 2.5- and 2.3-fold. Phase solubility diagram studies demonstrate that M1 and M2 significantly enhance the water-solubility of eighteen poorly soluble drugs. In vivo experiments in rat complete Freund's arthritis reveal that M1 not only improves the anti-inflammatory efficacy of indomethacin by up to 52 %, but also substantially reduces its side effect of gastric ulcer.