The invention provides antibodies, antigen binding fragments thereof, chimeric antigen receptors (CARs), and engineered T cell receptors, polynucleotides encoding the same, and in vitro cells comprising the same. The polynucleotides, polypeptides, and in vitro cells described herein can be used in an engineered CAR T cell therapy for the treatment of a patient suffering from a cancer. In one embodiment, the polynucleotides, polypeptides, and in vitro cells described herein can be used for the treatment of multiple myeloma.