Fig. 3.

PCSK9 immunoprecipitation and Western blotting analysis of patient serum samples. In order to confirm the effect of fenofibrate treatment on serum PCSK9 levels, representative patient serum samples that still had adequate volume remaining were immunoprecipitated with the same anti-PCSK9 capture monoclonal antibody used in the ELISA. Afterward, immunoprecipitates were analyzed via Western blotting with HRP-labeled polyclonal anti-PCSK9 antibody. Both baseline and endpoint samples from representative placebo and fenofibrate treated patients were analyzed. The predominant band indicated with the arrow represents intact PCSK9 protein. The mobility of the band immediately below is consistent with the furin cleavage product of PCSK9 while the mobility of the band at the bottom of the blot is consistent with PCSK9 propeptide (29). Results were compared with those obtained using the PCSK9 ELISA described in Fig. 2A. Results obtained via immunoprecipitation and Western blotting compared well with those obtained by ELISA, confirming the effect of fenofibrate treatment on PCSK9 levels.