Fuente: WIPO "tomato" Provided herein are antigen-binding proteins (ABPs) that selectively bind to M6PR and its isoforms and homologs, and compositions comprising the ABPs. Also provided herein are bispecific antigen-binding proteins (ABPs) that selectively bind to internalizing receptors, and a soluble target molecule or cell surface target molecule and its isoforms and homologs, and compositions comprising the ABPs.