Teclistamab is not chemotherapy. It is a bispecific antibody, a type of immunotherapy that works by directing your own immune cells to attack cancer. While chemotherapy drugs like melphalan and cyclophosphamide kill rapidly dividing cells throughout the body, teclistamab acts as a molecular bridge, physically connecting your T cells to myeloma cells so the immune system can destroy them with precision.
How Teclistamab Works
Teclistamab has two binding ends. One end attaches to a protein called BCMA found on the surface of myeloma cells. The other end grabs onto CD3, a marker on T cells (a key type of immune cell). By latching onto both at the same time, teclistamab pulls T cells directly to myeloma cells and activates them to kill the cancer. Think of it as handing your immune cells a GPS that leads them straight to the tumor.
This is fundamentally different from how chemotherapy operates. Chemotherapy drugs are cytotoxic, meaning they poison cells that divide quickly. That broad approach damages healthy tissue along with cancer, which is why chemotherapy causes hair loss, nausea, and widespread immune suppression. Teclistamab skips that entirely. It doesn’t poison anything. It redirects immune activity that’s already present in your body. The tradeoff is that its effectiveness depends on having enough functional T cells in your bloodstream, and the killing effect can weaken if those T cells become exhausted or drug levels drop.
What Teclistamab Treats
Teclistamab (brand name Tecvayli) is approved for adults with relapsed or refractory multiple myeloma, a blood cancer that forms in the bone marrow. “Relapsed or refractory” means the cancer came back after treatment or stopped responding to it.
The FDA originally granted accelerated approval for teclistamab as a standalone treatment for patients who had tried at least four prior lines of therapy, including a proteasome inhibitor, an immunomodulatory agent, and an anti-CD38 monoclonal antibody. In March 2026, that accelerated approval converted to traditional (full) approval. At the same time, the FDA approved a new use: teclistamab in combination with daratumumab for patients who have received at least one prior line of therapy. That second approval opens the drug to patients much earlier in their treatment journey.
The NCCN guidelines for multiple myeloma classify teclistamab as targeted therapy and list bispecific antibodies alongside CAR T-cell therapy as options for relapsed or resistant disease. Bispecific antibodies generally aren’t available as a first treatment.
How Effective It Is
In the phase 1/2 MajesTEC-1 trial, which studied teclistamab as a single agent in heavily pretreated patients, the overall response rate was 63%. That means roughly six out of ten patients saw their cancer shrink meaningfully. Among those who responded, the median duration of response reached 24 months with long-term follow-up, a notable result for a population that had already failed multiple therapies.
How It’s Given
Teclistamab is a subcutaneous injection, given just under the skin rather than through a vein. Treatment begins with a step-up dosing schedule designed to ease the body into the drug and reduce the risk of serious immune reactions. On day one, you receive a very small dose. Three days later, you receive a larger dose. Three days after that, you receive the first full treatment dose. Once the step-up phase is complete, the full dose continues once weekly until the cancer progresses or side effects become unacceptable.
Because of the risk of serious reactions during those initial doses, patients are required to stay in the hospital for 48 hours after each step-up injection. Teclistamab is only available through a restricted program (called a REMS), which means the prescribing doctor and dispensing pharmacy both need special certification. You won’t pick this up at a retail pharmacy.
Side Effects to Expect
The side effect profile looks nothing like chemotherapy. You’re unlikely to lose your hair or experience the severe nausea associated with cytotoxic drugs. Instead, the primary risks stem from intense immune activation.
Cytokine Release Syndrome
Cytokine release syndrome (CRS) is the most common side effect, occurring in roughly 63% of patients. CRS happens when activated T cells flood the body with inflammatory signaling molecules. Symptoms can include fever, chills, low blood pressure, and difficulty breathing. The good news: most cases are mild to moderate. In one study, 50% of CRS events were grade 1 (the mildest) and 21% were grade 2. CRS almost always occurs during the step-up dosing phase, which is exactly why hospitalization is required during that period. The first step-up dose carries the highest risk. Once you’re past the ramp-up and on weekly dosing, new CRS events become uncommon.
Neurologic Side Effects
About 14% of patients experience some form of neurotoxicity, known in clinical settings as ICANS (immune effector cell-associated neurotoxicity syndrome). Severe cases (grade 3 or 4) are rare. Your medical team will monitor you closely for any neurologic changes during and after treatment.
Infections and Low Blood Counts
Teclistamab can suppress certain immune functions even as it activates T cells, leaving you more vulnerable to infections. Low neutrophil counts (a type of white blood cell) are also common. Your care team will check blood counts regularly throughout treatment and watch for signs of infection at every visit.
Why the Distinction From Chemotherapy Matters
Understanding that teclistamab is immunotherapy rather than chemotherapy changes what you should expect from treatment. You won’t face the same pattern of “chemo cycles” with recovery weeks in between. Instead, you’ll receive weekly injections on an ongoing basis. The early phase of treatment requires hospitalization and close monitoring, but once you’re established on the drug, visits become more routine. The side effects you need to watch for are immune-driven reactions, not the tissue damage that chemotherapy causes. If you’ve been through chemotherapy before, the day-to-day experience of teclistamab will feel quite different.