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 (CysLT₁), which is increasingly recognized for its role in cancer progression. Overexpression of CysLT₁ 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 (GI₅₀ = 0.22 μM) and UO-31 renal cancer cells (GI₅₀ = 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 CysLT₁ inhibitors. This work adds value by providing a translational solution to a key limitation in CysLT₁-targeted cancer therapy, supporting further preclinical development of ace-quininib-HCl as a candidate for future clinical application.