Characterization of a water soluble quininib prodrug that blocks metabolic activity and proliferation of multiple cancer cell lines.

Quininib is a small molecule antagonist of cysteinyl leukotriene receptor 1 (CysLT), which is increasingly recognized for its role in cancer progression. Overexpression of CysLT has been documented in colorectal cancer, renal cell carcinoma, breast cancer, and uveal melanoma (UM). However, quininib's poor aqueous solubility presents a significant barrier to its clinical development. The aim of this study was to overcome this limitation by synthesizing and evaluating a novel ester analogue, ace-quininib, and its hydrochloride salt, ace-quininib-HCl, as more soluble, bioactive forms of quininib. The objectives were to 1) synthesize and characterize the analogues; 2) evaluate their anti-cancer activity in a panel of cell lines, including UM (OMM2.5) and metastatic pancreatic cancer (SUIT2-007); 3) assess their enzymatic conversion to quininib; 4) determine their aqueous solubility and in vivo suitability; and 5) evaluate preliminary toxicity in zebrafish larvae. Ace-quininib was rapidly converted to quininib in the presence of porcine liver esterase, confirming its function as a prodrug. It exhibited potent anti-cancer activity across the NCI-60 cell line panel, with the strongest effects observed in CCRF-CEM leukemia (GI = 0.22 μM) and UO-31 renal cancer cells (GI = 0.62 μM). Both ace-quininib and ace-quininib-HCl reduced metabolic activity in OMM2.5 and SUIT2-007 cells in a dose-dependent manner. Notably, ace-quininib-HCl also inhibited long-term colony formation in OMM2.5 cells. Solubility studies revealed that while quininib and ace-quininib remained water-insoluble, ace-quininib-HCl demonstrated excellent aqueous solubility (2.18 ± 0.18 mg/mL). Furthermore, both ace-quininib and quininib were well tolerated in zebrafish larvae, supporting their potential for in vivo application. The novelty of this study lies in the design of a previously unreported hydrochloride salt of an esterified quininib analogue with significantly enhanced solubility and preserved bioactivity. These results suggest that ace-quininib-HCl offers a viable strategy to improve the pharmacokinetic profile of CysLT inhibitors. This work adds value by providing a translational solution to a key limitation in CysLT-targeted cancer therapy, supporting further preclinical development of ace-quininib-HCl as a candidate for future clinical application.