A drug used in the treatment of cancerous diseases is comprised of amino acid solutions, mainly (a) a first solution A, containing L-cysteine, L-methionine and L-malic acid, b) a second solution B, containing L-histidine, L-phenylalanine, L-lysine and L-malic acid, C) a third solution C, containing L-tryptophan, L-valine, L-leucine, L-thrionine and L-ascorbic acid, d) and water as solvent. The use of L-malic acid and L-ascorbic acid as activators buffers and stabilizes the amino acids in their acid form. It is only under said stabilized form that the amino acids cause a modification of the blood pH value in the acidity range under 6.8. Growth stop and even regression of malignant tumours may thereby be achieved.
