Multiple myeloma is incurable by standard approaches because of inevitable relapse and development of treatment resistance in all patients. In our prior work, we identified a panel of macropinocytosing human monoclonal antibodies against CD46, a negative regulator of the innate immune system, and constructed antibody-drug conjugates (ADCs). In this report, we show that an anti-CD46 ADC (CD46-ADC) potently inhibited proliferation in myeloma cell lines with little effect on normal cells. CD46-ADC also potently eliminated myeloma growth in orthometastatic xenograft models. In primary myeloma cells derived from bone marrow aspirates, CD46-ADC induced apoptosis and cell death, but did not affect the viability of nontumor mononuclear cells. It is of clinical interest that the
Daniel W. Sherbenou, Blake T. Aftab, Yang Su, Christopher R. Behrens, Arun Wiita, Aaron C. Logan, Diego Acosta-Alvear, Byron C. Hann, Peter Walter, Marc A. Shuman, Xiaobo Wu, John P. Atkinson, Jeffrey L. Wolf, Thomas G. Martin, Bin Liu
CD46 is highly expressed on MM cells and is further increased in the setting of BM microenvironment.