Novel Salts of Sunitinib an Anticancer Drug with Improved Solubility

Abstract

Polymorph, co-crystal and salt screening experiments were carried out to identify novel solid forms with the improved physicochemical properties, particularly water solubility in the present case. Co-crystal formation was evaluated with urea and nicotinamide. These coformers do not have any ionic groups that favor the formation of salts. Sunitinib malate salt is being currently sold in the market. It is poorly soluble in water. Salt screening experiments were conducted with adipic acid, glutaric acid, nicotinic acid, 4-hydroxy benzoic acid and saccharin. The salts with 1:1 ratios were obtained with these acids, except for adipic acid, which yielded a 2:1 solid form. The solubility of these salts in deionized water was found to be 6 to 10 times greater than that of the marketed salt (sunitinib malate). Reversible Z-E isomerization was also well thought-out especially in presence of light and the isomerization was checked by HPLC. Formation of undesired E-isomer was additionally confirmed by 1H NMR. This observation has implications in the solubility study of sunitinib salt samples using HPLC method.