The trial is taking place at:

Hospital Nossa Senhora da Conceicao | Conceicao Hospital - Infectious Diseases Department

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A Study of Trastuzumab Emtansine in Combination With Atezolizumab or Placebo as a Treatment for Participants With Human Epidermal Growth Factor 2 (HER2)-Positive and Programmed Death-ligand 1 (PD-L1)-Positive Locally Advanced (LABC) or Metastatic Breast Cancer (MBC) (KATE3)

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Status and phase

Phase 3


Metastatic Breast Cancer


Drug: Atezolizumab
Other: Placebo
Drug: Trastuzumab Emtansine

Study type


Funder types



2020-002818-41 (EudraCT Number)

Details and patient eligibility


This study will evaluate the efficacy, safety and patient-reported outcomes of trastuzumab emtansine plus atezolizumab compared with trastuzumab emtansine plus placebo in participants with HER2-positive and PD-L1-positive LABC or MBC.Participants must have progressed either during or after prior trastuzumab- (+/- pertuzumab) and taxane-based therapy for LABC/MBC; or during (or within 6 months after completing) trastuzumab- (+/-pertuzumab) and taxane-based therapy in the neoadjuvant and/or adjuvant setting.


96 patients




18+ years old


No Healthy Volunteers

Inclusion criteria

  • HER2+ and PD-L1+ locally advanced (LABC) or metastatic breast cancer (MBC)
  • Progression must have occurred during most recent treatment for LABC/MBC or during, or within 6 months after completing, neoadjuvant and/or adjuvant therapy
  • Prior treatment with trastuzumab (+/- pertuzumab) and taxane in the neoadjuvant and/or adjuvant, locally advanced, or metastatic setting
  • No more than two prior lines of therapy in the metastatic setting
  • Measurable disease per RESIST version 1.1
  • Eastern Cooperative Oncology Group (ECOG) Performance Status of 0 or 1
  • Life expectancy >= 6 months
  • Adequate hematologic and end-organ function
  • For women of childbearing potential: agreement to remain abstinent or use contraception, and agreement to refrain from donating eggs
  • For men: agreement to remain abstinent or use contraceptive measures, and agreement to refrain from donating sperm

Exclusion criteria

  • Prior treatment with trastuzumab emtansine in metastatic setting
  • History of exposure to cumulative doses of anthracyclines
  • Symptomatic or actively progressing central nervous system (CNS) metastases; asymptomatic CNS lesions ≤ 2cm without clinical requirement for local intervention or asymptomatic patients with treated CNS lesions are eligible
  • Current Grade >= 3 peripheral neuropathy
  • Cardiopulmonary dysfunction
  • History of malignancy within 5 years prior to initiation of study treatment, with the exception of the cancer under investigation and malignancies with a negligible risk of metastasis or death
  • History of leptomeningeal disease
  • Active or history of autoimmune disease or immune deficiency
  • Active hepatitis B, hepatitis C and/or tuberculosis
  • Prior allogeneic stem cell or solid organ transplantation
  • Receipt of a live, attenuated vaccine within 4 weeks prior to initiation of study treatment, during treatment, or within 5 months following the last dose of study treatment
  • Pregnancy or lactation

Trial design

Primary purpose




Interventional model

Parallel Assignment


Double Blind

96 participants in 2 patient groups

Arm A: Trastuzumab Emtansine and Placebo
Active Comparator group
Placebo matched to atezolizumab followed by trastuzumab emtansine 3.6 milligrams per kilogram (mg/kg) intravenous (IV) infusion on Day 1 Cycle 1 and thereafter on Day 1 of each 21-day cycle until disease progression, unmanageable toxicity, or study termination by the sponsor.
Drug: Trastuzumab Emtansine
Other: Placebo
Arm B: Trastuzumab Emtansine and Atezolizumab
Experimental group
Atezolizumab 1200 mg IV infusion followed by trastuzumab emtansine 3.6 mg/kg IV infusion on Day 1 Cycle 1 and thereafter on Day 1 of each 21-day cycle until disease progression, unmanageable toxicity, or study termination by the Sponsor.
Drug: Trastuzumab Emtansine
Drug: Atezolizumab

Trial contacts and locations



Central trial contact

Reference Study ID Number: MO42319

Data sourced from

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