In the PROTECT study, plasma samples were collected and stored at baseline and then every cycle (every 3–4 weeks) while on treatment for up to 6 months. Patients were then clinically observed for the development of CVAE for an additional 12 months. The current study evaluated the baseline and post‐baseline plasma samples from 60 patients treated with a carfilzomib‐based regimen. Patients experiencing a CVAE during treatment had an additional plasma sample collected at the visit when CVAE was diagnosed as part of the PROTECT protocol, and these samples were analyzed as the post‐baseline samples. Since all the CVAE occurred within 6 months of initiation of carfilzomib therapy, for patients who did not experience CVAE during the study, the plasma samples at the 6‐month visits were analyzed as the post‐baseline samples.