Why do bispecific antibodies like teclistamab and glofitamab work in blood cancers, and how do they compare with CAR-T?

Bispecific antibodies (specifically T-cell engagers) have transformed the treatment of relapsed and refractory hematologic cancers.

---

1. Why They Work in Blood Cancers

Bispecific antibodies are engineered to bind two distinct targets simultaneously:

1. CD3 on the surface of the patient’s own cytotoxic T cells.
2. A tumor-specific antigen on the malignant blood cell:
   • Teclistamab: Targets BCMA (B-cell maturation antigen), universally expressed on plasma cells in multiple myeloma.
   • Glofitamab: Targets CD20, widely expressed on mature B cells and B-cell lymphomas (such as diffuse large B-cell lymphoma).

The Mechanism:

• Artificial Immunological Synapse: Normally, a T cell requires an antigen to be processed and presented via MHC (major histocompatibility complex) to trigger an attack. Bispecifics physically pull the T cell and cancer cell together, bypassing the need for MHC presentation or natural T-cell receptor specificity.
• Direct Cytotoxicity: Once bound, the T cell becomes activated, releasing perforins and granzymes that punch holes in the cancer cell membrane and trigger apoptosis (cell death).

Why Blood Cancers Are Ideal Targets:

• Clear lineage markers: Blood cells have reliable surface markers (like CD19, CD20, and BCMA) that are consistently expressed on cancer cells. While normal healthy B cells or plasma cells are also depleted, humans can tolerate this temporary depletion with supportive care (like IVIG).
• Anatomical accessibility: Circulating lymphocytes, bone marrow, and lymph nodes are easily accessible to infused proteins, allowing the antibodies and T cells to interact readily.

---

2. How They Compare to CAR-T Cell Therapy

Both modalities use the same underlying principle—redirecting T cells to kill cancer cells via specific surface antigens—but they implement it in fundamentally different ways.

Summary

• CAR-T is often favored for eligible patients who can safely wait for manufacturing, offering the potential for a single treatment and long, therapy-free remissions.
• Bispecifics provide a powerful, immediately available alternative—particularly valuable as an "off-the-shelf" option for aggressive disease, for patients who cannot travel to specialized cell therapy centers, or for those whose cancer has relapsed after CAR-T.