BACKGROUND: Recently, the authors reported improved time to disease progression (TTP) with a combination of pegylated liposomal doxorubicin (PLD) and bortezomib compared with bortezomib alone in a phase 3 randomized trial in patients with recurrent/refractory multiple myeloma (MM). In the current analysis, they determined 1) the efficacy of PLD plus bortezomib versus bortezomib alone in patients with MM who had failed on prior thalidomide/lenalidomide (immunomodulatory drug [IMiD]) treatment and 2) the efficacy and safety profile of PLD plus bortezomib in IMiD-exposed and IMiD-naive patients. METHODS: This prespecified analysis included 646 patients who were randomized to receive either PLD with bortezomib (n=324; 194 IMiD-naive patients and 130 IMiD-exposed patients) or bortezomib alone (n=322; 184 IMiD-naive patients and 138 IMiD-exposed patients). The primary efficacy endpoint was TTP, and secondary endpoints included overall survival, response rate, and safety. RESULTS: The median TTP was significantly longer with PLD plus bortezomib compared with bortezomib alone in IMiD-exposed patients (270 days vs 205 days). No statistical difference was noted with respect to TTP between IMiD-naive (295 days) versus IMiD-exposed (270 days) subgroups who received PLD plus bortezomib. A sustained trend favoring combination therapy was observed in analyses of overall survival. In patients who achieved a response, the response duration was comparable for IMiD-naive patients and IMiD-exposed patients in the combination treatment group and lasted a median of 310 days and 319 days, respectively. The incidence of grade 3/4 adverse events was similar with PLD plus bortezomib regardless of prior IMiD exposure. CONCLUSIONS: A significantly prolonged TTP was observed with combined PLD plus bortezomib combination therapy compared with bortezomib alone despite prior IMiD exposure. For the combination treatment arm in the IMiD-naive and IMiD-exposed subgroups, TTP was comparable. Similarly, the safety profile of the PLD plus bortezomib combination was unaltered by prior IMiD exposure.