STABILIZATION SOLUTION OF PLATINUM (II) ANTITUMOR AGENT

PURPOSE: To obtain the subject low-toxic, chemically and physically stable solution comprising a malonato platinum(II) compound, 1,1- cyclobutanedicarboxylic acid, pH modifier and carrier, and useful for treating various kinds of human cancer. CONSTITUTION: This stabilized solution of platinum(II) antitumor agent stable both chemically and physically, is obtained by purging, with air or oxygen gas, a mixture of (A) a malonatoplatinum (II) compound (carboplatin or malonato homologue) at an antitumor-effective level, (B) a 1,1- cyclobutanedicarboxylic acid (or the corresponding malonato homologue) or its alkali metal salt at a level enough to stabilize the final solution, (C) a pH modifier enough to keep the final solution at about pH 4-7 (e.g. sodium hydroxide) and (D) a pharmaceutically permissible carrier (e.g. water) and then putting the resultant purged solution into a vessel so that at least 50 vol% thereof is not filled with the liquid but the solution is saturated with air or oxygen.