ABSTRACT
(20S)-7-(2-isopropylamino)ethylcamptothecin.HCl (CKD-602), a new camptothecin (CPT) anticancer agent, is a pale yellowish crystalline compound. DSC thermogram exhibited a melt endotherm near 270 degrees C, and CKD-602 was found to be slightly hygroscopic. The solubility of CKD-602 in deionized water was 8.22 mg/ml, and two pK(a) values were measured to be 2.32 and 9.15, respectively. A pH-dependent partition coefficient behavior in octanol-buffer was observed. CKD-602 in solid state was stable over the range of temperature and humidity, but decomposed slightly by light. The hydrolysis of CKD-602 occurred reversibly and rapidly in aqueous buffer solutions. The conversion rate constants (k(f): from the lactone to the carboxylate and k(r): from the carboxylate to the lactone) and the final equilibrium ratio (K(eq)) between two species were dependent on the pH of aqueous solutions.