The invention relates to the field of medicine and pharmaceuticals and particularly to a novel dosage form of an antitumour preparation, which ensures the hydrolytic and physical stability of said preparation, as well as to a method for producing a dosage form of this type. The present stable dosage form is a lyophilisate comprising an etidronate-cytarabine conjugate or a pharmaceutically acceptable salt thereof, and a stabiliser which is a divalent metal salt, in a molar ratio of stabiliser to conjugate of 1:1 to 20:1. A dosage form of this type ensures the hydrolytic and physical stability of the conjugate during long-term storage, and the stability of solutions of the conjugate for parenteral administration during clinical use of same.
