Method and kit for labeling a biomolecule with one or more detectable labels, including a radiolabel

The current invention relates to a method for labeling an antibody or a fragment thereof with a detectable label, wherein at least one of said detectable labels is a radionuclide. The labeling occurs either in the presence of ethanol and vitamin C, wherein the concentration of ethanol in the labeling reaction is between 5% v/v and 15% v/v and the concentration of vitamin C in the labeling reaction is between 0.2 mg/ml and 2.5 mg/ml. Or the labeling occurs in the presence of ethanol and a derivative of vitamin C, wherein said derivative is an ascorbyl glucoside chosen from the list of 2-O-α-D-glucopyranosyl ascorbic acid, 2-O-β-D-glucopyranosyl ascorbic acid, 5-O-α-D-glucopyranosyl ascorbic acid, 6-O-α-D-glucopyranosyl ascorbic acid, 3-O-glycosyl-L-ascorbic acid, 6-O-acyl-2-O-α-D-glucopyranosyl ascorbic acid or a mixture thereof, wherein the concentration of ethanol in the labeling reaction is between 5% v/v and 15% v/v and the concentration of said derivative of vitamin C in the labeling reaction is between 5 mg/ml and 150 mg/ml. The current invention also relates to kits for labeling an antibody or antibody fragment with a radionuclide and specific uses of those kits.