This is a multicenter, open label, dose escalation, Phase I / II study in subjects with relapsed and/or refractory MM. Up to 24 subjects to be enrolled in the Phase I to determine the RP2D. Up to 77 additional evaluable subjects to be enrolled in Phase II for a maximum up to 101 subjects treated in the study. Study centers in the USA and the UK will participate in Phase I and II. Centers in the Philippines will be participating in Phase II only. The planned enrollment period is 22 months and the planned study duration is 28 months.