NZ 604034 Disclosed is a method for extracorporeal removal of a low molecular weight protein, or fragment or derivative thereof, having a megalin and/or cubilin binding motif, from a complex biological fluid, comprising performing the following steps to a sample of complex biological fluid containing a low molecular weight protein, or fragment or derivative thereof, having a binding affinity for megalin and/or cubilin: bringing said sample into contact with one or more of: a separation medium comprising: at least one megalin polypeptide and at least one cubilin polypeptide immobilised on a support； a medical device comprising said separation medium； and a dialysis device comprising said medical device, under conditions allowing binding of said low molecular weight protein, or fragment or derivative thereof, to said at least one megalin polypeptide and/or said at least one cubilin polypeptide, separating said sample from said support, such that at least part of the total amount of said low molecular weight protein, or fragment or derivative thereof, initially present in said sample is retained on the support, and recovering said sample containing a reduced amount of said low molecular weight protein, or fragment or derivative thereof.
