for females ages 18 years and up (full criteria)
study started
estimated completion



This study is designed to evaluate the efficacy, safety, and pharmacokinetics of several immunotherapy-based combination treatments in participants with inoperable locally advanced or metastatic HR-positive, HER2-negative breast cancer who have progressed during or following treatment with a cyclin-dependent kinase (CDK) 4/6 inhibitor in the first- or second-line setting, such as palbociclib, ribociclib, or abemaciclib. The study will be performed in two stages. During Stage 1, participants will be randomized to fulvestrant (control) or an atezolizumab-containing doublet or triplet combination. Those who experience disease progression, loss of clinical benefit, or unacceptable toxicity may be eligible to receive a new triplet combination treatment in Stage 2 until loss of clinical benefit or unacceptable toxicity. New treatment arms may be added and/or existing treatment arms may be closed during the course of the study on the basis of ongoing clinical efficacy and safety as well as the current treatments available.

Official Title

A Phase Ib/II, Open-Label, Multicenter, Randomized Umbrella Study Evaluating the Efficacy and Safety of Multiple Immunotherapy-Based Treatment Combinations in Patients With Hormone Receptor-Positive HER2-Negative Breast Cancer (MORPHEUS-HR+ Breast Cancer)


Breast Neoplasms Tamoxifen Bevacizumab Atezolizumab Fulvestrant Exemestane Entinostat Antibodies Atezolizumab (MPDL3280A), an engineered anti-programmed death-ligand 1 (PD-L1) antibody Ipatasertib Abemaciclib


You can join if…

Open to females ages 18 years and up

for Both Stages:

  • Measurable disease per RECIST v1.1
  • Adequate hematologic and end organ function
  • Disease progression during or after first- or second-line hormonal therapy with CDK4/6 inhibitor

Inclusion Criteria for Stage 1:

  • Eastern Cooperative Oncology Group (ECOG) performance status 0-1
  • Metastatic or inoperable, locally advanced, histologically or cytologically confirmed invasive HR-positive HER2-negative breast cancer
  • Recommended for endocrine therapy, and cytotoxic chemotherapy not indicated at study entry
  • Recurrence or progression following most recent systemic breast cancer therapy
  • Disease progression during or after first- or second-line hormonal therapy for locally advanced or metastatic disease
  • Postmenopausal according to protocol-defined criteria
  • Life expectancy >3 months
  • Available tumor specimen for determination of PD-L1 status

Inclusion Criteria for Stage 2:

  • ECOG performance status of 0-2
  • Ability to initiate treatment within 3 months after disease progression or unacceptable toxicity on a Stage 1 regimen

You CAN'T join if...

for Both Stages:

  • Significant or uncontrolled comorbid disease as specified in the protocol
  • Uncontrolled tumor-related pain
  • Autoimmune disease except for stable/controlled hypothyroidism, Type 1 diabetes mellitus, or certain dermatologic conditions
  • Positive human immunodeficiency virus test
  • Active hepatitis B or C
  • Active tuberculosis
  • Severe infection within 4 weeks and/or antibiotics within 2 weeks prior to study treatment
  • Prior allogeneic stem cell or solid organ transplantation
  • History of malignancy other than breast cancer within 2 years prior to screening except those with negligible risk of metastasis/death
  • History of or known hypersensitivity to study drug or excipients
  • For patients entering Stage 2, recovery from all immunotherapy-related adverse events to Grade 1 or better or to baseline at the time of consent

Exclusion Criteria for Stage 1:

  • Prior fulvestrant or cytotoxic chemotherapy for metastatic breast cancer, or certain other agents as specified in the protocol
  • Unresolved AEs from prior anti-cancer therapy
  • Eligibility only for the control arm
  • Prior treatment with inhibitors as specified in the protocol

Exclusion Criteria for Stage 2:

  • Unacceptable toxicity with atezolizumab during Stage 1
  • Uncontrolled cardiovascular disease or coagulation disorder, including use of anticoagulants as specified in the protocol
  • Significant abdominal or intestinal manifestations within 6 months prior to treatment
  • Grade 2 or higher proteinuria


  • UCSF Helen Diller Family CCC accepting new patients
    San Francisco California 94158 United States
  • Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center accepting new patients
    Torrance California 90502 United States
  • Cedars-Sinai Medical Center completed
    Los Angeles California 90048 United States
  • Wellness Oncology and Hematology - Main Office accepting new patients
    West Hills California 91307 United States
  • Stanford Cancer Institute accepting new patients
    Stanford California 94305 United States


accepting new patients
Start Date
Completion Date
Hoffmann-La Roche
Phase 1/2 Breast Cancer Research Study
Study Type
Expecting 126 study participants
Last Updated