Last reviewed 2026-04-20 · How we verify

Kadcyla (trastuzumab-emtansine)

Trastuzumab emtansine is a HER2-targeted antibody-drug conjugate that works by binding to the HER2 receptor and releasing a cytotoxic agent.

Trastuzumab emtansine, marketed by Pfizer Inc., is a HER2-targeted antibody-drug conjugate. It is used for the treatment of HER2-positive breast cancer. The drug works by binding to the HER2 receptor, undergoing receptor-mediated internalization, and releasing a cytotoxic agent that disrupts microtubule networks in cancer cells. This leads to cell cycle arrest and apoptotic cell death. Trastuzumab emtansine has shown clinical differentiation in patients who have received prior trastuzumab-based therapy. Its commercial significance is evident in its revenue of $1.4 billion. The drug's pipeline developments are focused on expanding its indications and improving treatment outcomes for patients with HER2-positive breast cancer.

At a glance

Mechanism of action

Trastuzumab emtansine is a type of antibody-drug conjugate that combines the humanized monoclonal antibody trastuzumab with the cytotoxic agent DM1. This conjugate is designed to target and kill cancer cells that overexpress the HER2 receptor. When trastuzumab emtansine binds to the HER2 receptor, it undergoes receptor-mediated internalization and is catabolized in lysosomes, releasing DM1-containing catabolites. These catabolites then bind to tubulin, disrupting microtubule networks and leading to cell cycle arrest and apoptotic cell death.

Approved indications

• Adjuvant treatment of HER2-positive breast cancer
• Treatment of HER2-positive breast cancer in patients who have received prior trastuzumab-based therapy
• Treatment of HER2-positive breast cancer in patients for whom trastuzumab and pertuzumab are indicated
• Treatment of HER2-positive unresectable or metastatic breast cancer in patients who have received prior anti-HER2-based therapy

Boxed warnings

• WARNING: HEPATOTOXICITY, CARDIAC TOXICITY, EMBRYO-FETAL TOXICITY Hepatotoxicity: Serious hepatotoxicity has been reported, including liver failure and death in patients treated with KADCYLA. Monitor serum transaminases and bilirubin prior to initiation of KADCYLA treatment and prior to each KADCYLA dose. Reduce dose or discontinue KADCYLA as appropriate in cases of increased serum transaminases or total bilirubin. ( 2.3 , 5.1 ) Cardiac Toxicity: KADCYLA administration may lead to reductions in left ventricular ejection fraction (LVEF). Evaluate left ventricular function in all patients prior to and during treatment with KADCYLA. Withhold treatment for clinically significant decrease in left ventricular function. ( 2.3 , 5.2 ) Embryo-Fetal Toxicity: Exposure to KADCYLA during pregnancy can result in embryo-fetal harm. Advise patients of these risks and the need for effective contraception. ( 5.3 , 8.1 , 8.3 ) WARNING: HEPATOTOXICITY, CARDIAC TOXICITY, EMBRYO-FETAL TOXICITY See full prescribing information for complete boxed warning Hepatotoxicity, liver failure and death have occurred in KADCYLA-treated patients. Monitor hepatic function prior to initiation and prior to each dose. Institute dose modifications or permanently discontinue as appropriate. ( 2.3 , 5.1 ) KADCYLA may lead to reductions in left ventricular ejection fraction (LVEF). Assess LVEF prior to initiation. Monitor and withhold dosing or discontinue as appropriate. ( 2.3 , 5.2 ) Embryo-Fetal Toxicity: Exposure to KADCYLA during pregnancy can result in embryo-fetal harm. Advise patients of these risks and the need for effective contraception. ( 5.3 , 8.1 , 8.3 )

Common side effects

• Fatigue
• Nausea
• Musculoskeletal pain
• Hemorrhage
• Thrombocytopenia
• Increased transaminases
• Headache
• Constipation
• Pyrexia
• Abdominal pain
• Stomatitis
• Anemia

Drug interactions

• ketoconazole
• itraconazole
• clarithromycin
• atazanavir
• indinavir
• nefazodone
• nelfinavir
• ritonavir
• saquinavir
• telithromycin
• voriconazole

Key clinical trials

• Targeted Therapy Directed by Genetic Testing in Treating Patients With Advanced Refractory Solid Tumors, Lymphomas, or Multiple Myeloma (The MATCH Screening Trial) (PHASE2)
• A Study to Describe the Diagnosis, Anti-Cancer Treatment and Clinical Outcome in Patients With Newly Diagnosed Breast Cancer in Latin America
• CompassHER2-pCR: Decreasing Chemotherapy for Breast Cancer Patients After Pre-surgery Chemo and Targeted Therapy (PHASE2)
• Beamion BCGC-1: A Study to Find a Suitable Dose of Zongertinib Used Alone and in Combination With Other Treatments to Test Whether it Helps People With Different Types of HER2+ Cancer That Has Spread (PHASE1, PHASE2)
• Secondary BRain Metastases Prevention After Isolated Intracranial Progression on Trastuzumab/Pertuzumab or T-DM1 in Patients With aDvanced Human Epidermal Growth Factor Receptor 2+ brEast Cancer With the Addition of Tucatinib (PHASE2)
• I-SPY TRIAL: Neoadjuvant and Personalized Adaptive Novel Agents to Treat Breast Cancer (PHASE2)
• A Study Evaluating the Efficacy and Safety of Biomarker-Driven Therapies in Patients With Persistent or Recurrent Rare Epithelial Ovarian Tumors (PHASE2)
• Tumor-agnostic Precision Immuno-oncology and Somatic Targeting Rational for You (TAPISTRY) Platform Study (PHASE2)

Primary sources

Every claim on this page is sourced from regulatory or scientific primary sources. See our editorial policy for full methodology.

Competitive intelligence

For the full competitive landscape — auto-detected comparators, recent regulatory actions across the set, upcoming PDUFA, patent timeline, sponsor landscape:

• Kadcyla CI brief — competitive landscape report
• Kadcyla updates RSS · CI watch RSS
• Roche portfolio CI