Antibody-Drug Conjugates (ADCs)
Sometimes called “smart chemo,” antibody-drug conjugates track down cancer cells and deliver small doses of powerful chemotherapy directly into them. Unlike chemotherapy, which causes harm to healthy and unhealthy cells, ADCs use targeted therapy to deliver the chemo directly to cancer cells, making the medicines less toxic to healthy cells.
Examples of ADCs
There are four antibody-drug conjugates used to treat breast cancer:
Other ADCs (used to treat other cancers) include Mylotarg (gemtuzumab ozogamicin), Adcetris (brentuximab vedotin), and Polivy (polatuzumab vedotin). Today, there are over a dozen cancer-targeted ADCs approved by the Food and Drug Administration.
How do antibody-drug conjugates work?
ADCs target specific proteins found on the surface of cancer cells. Once the medicine attaches to these proteins and enters the cell, it releases chemotherapy, which can destroy it.
To get more technical, ADCs contain:
a monoclonal antibody: a type of protein made in the lab that can bind to substances in the body, including cancer cells. Each monoclonal antibody is made so that it binds only to one substance.
chemotherapy: specific medications that have been proven to effectively kill specific cancer cells.
a linker: a protein that connects the antibody and chemotherapy.
Chemotherapy affects rapidly dividing cells, which includes some healthy cells (for example, skin cells) and unhealthy cells (for example, cancer cells). ADCs only target cancer cells, so the healthy cells around the cancer are less likely to be harmed.
How ADCs are used in breast cancer treatment
Antibody-drug conjugates are commonly used to treat:
HER2-positive metastatic breast cancer that has previously been treated with Herceptin and taxane chemotherapy
early-stage HER2-positive breast cancer after surgery if cancer was still present after neoadjuvant (before surgery) treatment with Herceptin and taxane chemotherapy
triple-negative breast cancer (TNBC) that has spread to body parts away from the breast (metastatic) or can’t be removed with surgery and has been treated with two or more other treatments
hormone receptor-positive, HER2-negative metastatic breast cancer or breast cancer that can’t be removed with surgery, and has been treated with hormonal therapy and two or more other treatments
metastatic HER2-positive breast cancer and has been treated with an anti-HER2 medicine and cannot be removed with surgery
metastatic hormone receptor-positive, HER2-low or -ultralow breast cancer and has been treated with hormonal therapy and cannot be removed with surgery
metastatic HER2-low breast cancer and has been treated with chemotherapy and cannot be removed with surgery
Other uses for ADCs
ADCs are also used to treat:
blood cancers like Hodgkin lymphoma
cervical cancer
lung cancer
ovarian cancer
urothelial cancer
Common side effects of ADCs
The common side effects of antibody-drug conjugates are similar to chemotherapy side effects:
Being treated with antibody-drug conjugates may increase your risk of several serious side effects:
Heart problems: ADCs may cause serious heart problems, including some that don’t have symptoms, such as reduced heart function, and some that do have symptoms, such as congestive heart failure. Symptoms to watch for include swelling of the ankles or legs, shortness of breath, cough, or weight gain of more than 5 pounds in less than 24 hours.
Lung problems: ADCs may cause inflammation of the lungs, which can be life-threatening. Symptoms include trouble breathing, cough, tiredness, and fluid in the lungs.
Liver problems: ADCs may cause severe liver problems, including liver failure. Symptoms include swelling or pain in the abdomen; a yellow tint in the eyes or skin (jaundice); swollen legs, feet, or ankles.
Severe neutropenia: Neutropenia means you have abnormally low levels of neutrophils, a type of white blood cell. People with neutropenia have a much higher risk of getting serious infections. Your doctor will monitor your neutrophil counts during treatment. If you develop neutropenia, you may be treated with a granulocyte-colony stimulating factor medicine such as Neupogen (chemical name: filgrastim), Neulasta (chemical name: pegfilgrastim), or Zarxio (chemical name: filgrastim-sndz). Some physicians prescribe these granulocyte-colony stimulating factors preventively, even if you have never developed neutropenia from ADCs.
Severe diarrhea: Severe diarrhea can cause dehydration, low blood pressure, and severe kidney problems. Tell your doctor about any diarrhea you have so it can be treated right away.
Though your care team will monitor you throughout your treatment, experiencing any of these adverse effects can negatively impact your quality of life. These toxicities are still being researched — doctors hope that they can find ways to alleviate or eliminate them.
If you’re experiencing severe side effects, tell your care team right away. And if you’re thinking about stopping ADC treatment, talk to your doctor. They’ll help you understand your options.
— Last updated on August 22, 2025 at 5:11 PM