Design and Synthesis of a New Soluble Natural β-Carboline Derivative for Preclinical Study by Intravenous Injection

Harmine is a natural β-carboline compound showing several biological activities, including antiproliferative properties, but this soluble natural molecule lacks selectivity. Harmine derivatives were reported to overcome this problem, but they are usually poorly soluble. Here, we designed and synthesized a new 2, 7, 9-trisubstituted molecule (1-methyl-7-(3-methylbutoxy)-9-propyl-2-[(pyridin-2-yl)methyl]-9H-pyrido[3,4-b]indol-2-ium bromide) with a solubility of 1.87 ± 0.07 mg/mL in a simulated injection vehicle. This compound is stable for at least 72 h in acidic and physiological conditions (pH 1.1 and 7.4) as well as in a simulated injection vehicle (physiological liquid + 0.1% Tween80®). Solubility in those media is 1.06 ± 0.08 mg/mL and 1.62 ± 0.13 mg/mL at pH 7.4 and 1. The synthesized molecule displays a significant activity on five different cancer cell lines (IC₅₀ range from 0.2 to 2 µM on A549, MDA-MB-231, PANC-1, T98G and Hs683 cell lines). This compound is also more active on cancer cells (MDA-MB-231) than on normal cells (MCF-10a) at IC₅₀ concentrations. Due to its high activity at low concentration, such solubility values should be sufficient for further in vivo antitumoral activity evaluation via intravenous injection.