In this first Asian cooperative multicenter phase II study, previously untreated patients with MM (N = 44) received up to 6 cycles of 3-times-weekly low-dose Dex/Thal and 4 mg Zol (the dtZ regimen). Response was graded using Blad¨¦ criteria.
The average doses of Dex and Thal administered were 185.2 mg/month; and 87.5 mg/day, respectively. Thirty-nine (88.6 % ) patients demonstrated at least a partial response (PR), including 18.2 % very good partial response (VGPR), 15.9 % near complete response (nCR) and 18.2 % complete response (CR). Achievement of CR/nCR was related to significant (P < .05), rapid, and sustained inhibition of osteoclasts (OCs) and OC precursors (pOCs) by Zol. Sepsis was the most frequently reported serious toxicity, contributing to 3 of 4 deaths. Importantly, there was no peripheral neuropathy, osteonecrosis of the jaw, or nephrotoxicity.
We conclude that the dtZ regimen is an effective and well-tolerated regimen for Asian patients with newly diagnosed MM. The high rate of VGPR/nCR/CR suggests that Zol could have a clinically relevant anti-MM effect. Since infections are the most frequent adverse event, it is probably wise to further lower the dose of Dex in future studies.