Humanized anti-interleukin-6 receptor monoclonal antibody induced apoptosis of fresh and cloned human myeloma cells in vitro.

We investigated the effect of anti-IL-6 receptor monoclonal antibody (hPM1) on the in vitro proliferation of cloned and freshly isolated myeloma cells from 20 patients with advanced stage multiple myeloma (MM). Humanized PM1 significantly inhibited the growth of a myeloma cell line in a dose-dependent manner and inhibited more than 30% of the proliferation of fresh myeloma cells in 10 of the 19 cases. Flow cytometric analysis using annexin V and 7AAD showed that hPM1 induced apoptosis of myeloma cells. These observations suggest the possibility of using hPM1 for treating some patients with MM whose growth depends on IL-6.