Immunostimulatory antigen binding molecules that specifically bind to bcma

An immunostimulatory antigen binding molecule that specifically binds to B cell maturation agent (BCMA), comprising

• (a) a Fab molecule comprising
• (i) a heavy chain variable region (VH BCMA) comprising a heavy chain complementary determining region CDR-H1 of SEQ ID NO:
• 1 (GYTFTNYWMH), a CDR-H2 of SEQ ID NO:
• 2 (IIHPNSGSTNYNEKFQG), and a CDR-H3 of SEQ ID NO:
• 3 (GIYDYPFAY), and
• (ii) a light chain variable region (VL BCMA) selected from the group consisting of
• (a) a VL comprising a light chain complementary determining region CDR-L1 of SEQ ID NO:
• 4 (RASESVSIHGTHLMH), a CDR-L2 of SEQ ID NO:
• 5 (AASSLQS) and a CDR-L3 of SEQ ID NO:
• 6 (QQSIEDPYT);
• and
• (b) a VL comprising a light chain complementary determining region CDR-L1 of SEQ ID NO:
• 4 (RASESVSIHGTHLMH), a CDR-L2 of SEQ ID NO:
• 7 (AASNLES) and a CDR-L3 of SEQ ID NO:
• 6 (QQSIEDPYT), and
• (c) a VL comprising a light chain complementary determining region CDR-L1 of SEQ ID NO:
• 4 (RASESVSIHGTHLMH), a CDR-L2 of SEQ ID NO:
• 8 (AASNLQS) and a CDR-L3 of SEQ ID NO:
• 6 (QQSIEDPYT),
• (b) a first and a second polypeptide that are linked to each other by a disulfide bond, wherein the antigen binding molecule is characterized in that the first polypeptide comprises two ectodomains of 4-1BBL each comprising the amino acid sequence of SEQ ID NO:9 or SEQ ID NO:10 that are connected to each other by a peptide linker, and in that the second polypeptide comprises one ectodomain of 4-1BBL comprising the amino acid sequence of SEQ ID NO:9 or SEQ ID NO:10, and
• (c) an IgG Fc domain.