Protein binding of 2-chloro 2'-deoxyadenosine (cladribine) in healthy subjects and in patients with leukaemia.

The plasma protein binding of 2-chloro-2'-deoxyadenosine (CdA) at 37 degrees C was studied by ultrafiltration in 5 healthy volunteers, in 11 patients with haematological malignancies and in purified protein preparations. In the patients, the binding of CdA to plasma proteins was 25.0% and in healthy subjects it was 21.1%. In a solution of human serum albumin (40 g.l-1), 24.3% CdA was bound, but less than 5% was bound in a solution of alpha 1-acid-glycoprotein (0.7 g.l-1). No dependence of binding on the concentration of CdA was found within a range 25-1000 nmol.l-1. In conclusion, due to its limited binding to plasma proteins, any change in the binding of CdA is unlikely to have a major influence on its pharmacological effect.