Tafasitamab is a targeted therapy for specific blood cancers, particularly diffuse large B-cell lymphoma (DLBCL). This medication is a monoclonal antibody, a laboratory-produced protein engineered to mimic natural immune system antibodies. Tafasitamab works by precisely identifying and engaging with cancer cells, offering a focused approach to treatment.
Understanding the Target CD19
B-cells are white blood cells that play a significant role in the body’s immune system, primarily by producing antibodies to fight infections. These cells develop from hematopoietic stem cells in the bone marrow and mature in the lymphatic system. On the surface of these B-cells, including cancerous B-cells found in DLBCL, there is a specific protein called CD19.
CD19 acts as a marker on the surface of B-cells throughout their development, from pre-B cells to mature B lymphocytes. This protein is widely expressed on B-cell malignancies, making it an attractive target for cancer therapies. CD19 is not found on hematopoietic stem cells or other healthy organs, minimizing toxicity to non-cancerous tissues during treatment.
How Tafasitamab Identifies Cancer Cells
Tafasitamab functions as an antibody, engineered to recognize and bind to the CD19 protein on cancerous B-cells. This binding is often described as a “lock and key” mechanism, where the antibody fits precisely into its target, CD19. The drug’s Fc region has been modified to enhance its affinity for certain receptors on immune cells.
This attachment of tafasitamab to CD19 is the initial step in its action against cancer cells. Once tafasitamab binds to the CD19 antigen, it marks the cancerous B-cell for destruction by the body’s immune system. This precise targeting ensures therapeutic activity is primarily directed towards malignant cells, limiting harm to healthy tissues.
How Tafasitamab Eliminates Cancer Cells
Once tafasitamab binds to the CD19 protein on cancer cells, it initiates several immune responses that lead to their elimination. One primary mechanism is Antibody-Dependent Cell-mediated Cytotoxicity (ADCC). In ADCC, tafasitamab flags cancer cells for destruction by recruiting natural killer (NK) cells and gamma delta T cells. These NK cells recognize the antibody-coated cancer cells and release perforin and granzymes, molecules that cause the cancer cell to self-destruct.
Another way tafasitamab eliminates cancer cells is through Antibody-Dependent Cellular Phagocytosis (ADCP). This process involves recruiting immune cells like macrophages, which engulf foreign particles and cellular debris. Tafasitamab facilitates this by binding to Fc receptors on macrophages, prompting them to internalize and digest the tagged cancer cells. The engulfed tumor cell then fuses with lysosomes containing digestive enzymes, leading to its death.
Beyond these immune-mediated actions, tafasitamab can also directly induce programmed cell death, known as apoptosis, in targeted B-cells. Binding of tafasitamab to CD19 can send signals that activate internal pathways within the cancer cell, disrupting its survival and causing it to self-destruct. These combined mechanisms work together to effectively reduce the population of malignant B-cells.
Tafasitamab in Cancer Treatment
Tafasitamab has been approved for adult patients with relapsed or refractory diffuse large B-cell lymphoma (DLBCL) who are not eligible for autologous stem cell transplantation. It is administered intravenously at a dose of 12 mg/kg, often in combination with lenalidomide, an immunomodulatory agent. This combination therapy has shown increased activity compared to tafasitamab or lenalidomide alone in preclinical studies.
The combination of tafasitamab and lenalidomide has demonstrated durable responses in patients with relapsed or refractory DLBCL. In clinical studies, patients received tafasitamab weekly for the first three cycles and then every other week, combined with lenalidomide for up to 12 cycles, followed by tafasitamab monotherapy. This regimen offers a therapeutic option for patients who have not responded to or have relapsed after previous treatments, including those not candidates for high-dose chemotherapy and stem cell transplantation.