Monoclonal antibodies are laboratory-produced molecules that function like the antibodies naturally found in the human immune system. They are engineered to recognize and attach to specific targets, such as proteins on cancer cells or substances that contribute to cancer growth. This targeted approach allows them to distinguish between cancerous and healthy cells, offering a more precise treatment method compared to traditional chemotherapy, which affects rapidly dividing cells indiscriminately.
How Monoclonal Antibodies Work Against Cancer
Monoclonal antibodies combat cancer through various mechanisms. Some antibodies interfere with cancer cell growth signals by binding to receptors on the surface of cancer cells. This prevents the attachment of proteins that stimulate uncontrolled cell division and survival, effectively starving cancer cells of the signals they need to proliferate.
Other monoclonal antibodies flag cancer cells for destruction by the immune system. Once attached, they act as beacons, making it easier for immune cells like natural killer cells or macrophages to identify and eliminate the marked cancer cells. This process, known as antibody-dependent cellular cytotoxicity (ADCC), harnesses the body’s own defenses.
Some monoclonal antibodies deliver toxic substances directly to cancer cells. They carry chemotherapy drugs or radioactive particles. By binding specifically to cancer cells, these “armed” antibodies deliver their payload with precision, minimizing damage to surrounding healthy tissues. This targeted delivery helps reduce the severe side effects often associated with conventional treatments.
Monoclonal antibodies also enhance the immune system’s ability to fight cancer by blocking immune checkpoints. Cancer cells sometimes use proteins to “turn off” the immune response, hiding from attacking T-cells. Monoclonal antibodies can block these inhibitory signals, reactivating the immune system’s ability to recognize and destroy cancer cells.
Categories of Monoclonal Antibodies
FDA-approved monoclonal antibodies are categorized based on their structure and how they exert their therapeutic effects. Understanding these categories provides insight into their diverse applications in cancer treatment.
Naked Monoclonal Antibodies
Naked monoclonal antibodies have no attached drug or radioactive material. These antibodies work through direct mechanisms, such as blocking specific targets on cancer cells that promote growth or marking these cells for destruction by the body’s immune system. For instance, some naked antibodies block epidermal growth factor receptor (EGFR) on cancer cells, involved in cell growth and survival, and are used in treatments for colorectal or head and neck cancers. Others, like rituximab, target proteins such as CD20 on lymphoma cells, making them recognizable to the immune system for elimination.
Conjugated Monoclonal Antibodies
Conjugated monoclonal antibodies, also known as antibody-drug conjugates (ADCs), are antibodies chemically linked to a chemotherapy drug or a radioactive particle. These engineered molecules deliver their toxic payload directly to cancer cells by binding to specific antigens on their surface. This targeted delivery minimizes systemic exposure to the cytotoxic agent, reducing harm to healthy tissues and mitigating many severe side effects associated with traditional chemotherapy. An example includes ADCs used for certain types of leukemia, delivering a potent anti-microtubule agent directly to CD30-expressing cancer cells.
Bispecific Monoclonal Antibodies
Bispecific monoclonal antibodies are engineered to bind to two different targets simultaneously. Often, one binding site targets a protein on a cancer cell, while the other binds to a protein on an immune cell, such as a T-cell. This dual binding brings immune cells into close proximity with cancer cells, facilitating a direct attack and enhancing the immune response against the tumor. An example is blinatumomab, which targets both CD19 on malignant B cells and CD3 on T cells, promoting T-cell activation against acute lymphoblastic leukemia.
Administering Monoclonal Antibody Treatments
Monoclonal antibody treatments are administered intravenously (IV infusion), meaning the medication is delivered directly into a vein. This method ensures the antibodies circulate throughout the bloodstream to reach their intended targets. Patients receive these infusions in a clinic or hospital setting, where medical staff can closely monitor their response.
The schedule for monoclonal antibody treatments varies depending on the specific antibody, the type and stage of cancer, and the patient’s overall health. Treatments might be given weekly, bi-weekly, or monthly, and a course of therapy could last for several months or longer. Your healthcare team will determine the most appropriate schedule tailored to your individual treatment plan.
Patients receiving monoclonal antibody treatments may experience a range of side effects. Common immediate reactions during or shortly after infusion include fever, chills, fatigue, nausea, vomiting, diarrhea, skin rashes, and sometimes low blood pressure. These “infusion reactions” are manageable and are mitigated by administering premedications like antihistamines or corticosteroids before the infusion.
Beyond infusion reactions, other side effects can occur depending on the specific target of the antibody. For example, some antibodies may cause skin problems, such as rashes or sores, while others might lead to high blood pressure or, rarely, heart problems. Your healthcare provider will discuss the potential side effects associated with your particular treatment and how to manage them effectively.
Throughout treatment, patients are closely monitored for side effects and their response to therapy. This monitoring may involve regular physical examinations, blood tests, and imaging scans. It allows the medical team to adjust the treatment plan as needed, ensuring patient safety and optimizing therapeutic outcomes.