High throughput testing of drug library substances and monoclonal antibodies for capacity to reduce formation of cystatin C dimers to identify candidates for treatment of hereditary cystatin C amyloid angiopathy.

OBJECTIVE To establish a high-throughput system for testing the ability of drugs or monoclonal antibodies to reduce the in vitro formation of cystatin C dimers to identify substances potentially useful for treatment of patients with hereditary cystatin C amyloid angiopathy (HCCAA). METHODS Various combinations of incubation temperature, time period, guanidinium chloride concentration and concentration of cystatin C monomers were tested in low-volume formats to induce dimer formation of recombinant cystatin C. The extent of dimerization was analysed by gel filtration chromatography and agarose gel electrophoresis. RESULTS A high-throughput system based upon agarose gel electrophoresis was developed and used to test 1040 drugs in a clinical drug library for their capacity to reduce cystatin C dimer formation in vitro. Seventeen substances reducing dimer formation by more than 30% were identified. A similar system for testing the capacity of monoclonal antibodies against cystatin C to reduce the in vitro formation of cystatin C dimers was also developed and used to test a panel of 12 monoclonal antibodies. Seven antibodies reducing dimer formation by more than 30% were identified and the two most potent, Cyst28 and HCC3, reduced dimerization by 75 and 60%, respectively. CONCLUSION We constructed a simple high-throughput system for testing the capacity of drugs and monoclonal antibodies to reduce the in vitro formation of cystatin C dimers and several candidates for treatment of HCCAA could be identified.