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Not yet recruitingNCT07867262FrontROSEUpdated Oct 9, 2026

A Study to Evaluate the Effects of GDC-4198 in Combination With Letrozole, Fulvestrant, or Giredestrant in Participants With Locally Advanced or Metastatic Hormone Receptor-Positive, HER2-Negatve Breast Cancer

A Phase 1 interventional study of GDC-4198 and Fulvestrant in Advanced or Metastatic Breast Cancer, sponsored by Genentech, Inc.. Not yet recruiting. Open to participants aged 18 Years and older. Per ClinicalTrials.gov, last updated 2026-10-09.

Sponsored by Genentech, Inc. (part of Hoffmann-La Roche) · Phase 1, Interventional, and Treatment

Updated Oct 9, 2026Newly registeredGo to Updates ↓
Phase
Phase 1
Study type
Interventional
Enrollment
165
Allocation
Randomized
Ages
18 Years and older
Sex
All
01

Study summary

The study will evaluate the safety, pharmacokinetics, and preliminary activity of GDC-4198 when given in combination with endocrine therapy (ET) (letrozole, fulvestrant, or giredestrant) as first-line treatment to participants with locally advanced or metastatic Hormone receptor (HR)-positive, Human epidermal growth factor receptor-2 (HER2)-negative breast cancer

02

Conditions studied

  • Advanced or Metastatic Breast Cancer

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Keywords

  • HR+ positive
  • HER2 negative breast cancer
03

In context

Breast Neoplasms

12,815 studies on the registry are indexed under Breast Neoplasms; 2,920 are open to participants now.

This study's planned enrollment of 165 is above the median of 72 across 9,494 interventional studies indexed under Breast Neoplasms.

Browse Breast Neoplasms studies →

Lead sponsor

Genentech, Inc. is the lead sponsor of 517 studies on the registry; 22 are open to participants now.

Of its 95 completed or terminated interventional studies of FDA-regulated products, 52 (55%) have results posted.

First submitted after Genentech, Inc. became part of Hoffmann-La Roche.

Browse Genentech, Inc. studies →All Hoffmann-La Roche studies →

Counted across the registry records on this site, refreshed daily.

04

Who can participate

Ages eligible
18 Years and older
Sexes eligible
All
Accepts healthy volunteers
No

Go through the criteria one by one — yes, no or not sure — and take the list to your doctor or the study team. Kept in this browser only.

Inclusion criteria

  • Histologically or cytologically confirmed adenocarcinoma of the breast that is locally advanced or metastatic and HER2-negative disease.
  • Disease documented HER2-negative tumor according to American Society of Clinical Oncology/College of American Pathologists (ASCO/CAP) guidelines or documented ER-positive tumor according to ASCO/CAP guidelines.
  • Measurable and/or non-measurable disease per Response Evaluation Criteria in Solid Tumors, Version 1.1 (RECIST v1.1) (including bone-only disease).
  • For females \<= 60 years of age who are not in a postmenopausal state and males: initiation of treatment with luteinizing hormone-releasing hormone (LHRH) agonist therapy prior to initiation of study treatment according to clinical practice for the selected agent (preferably at least 14 days prior to initiation of study treatment), and agreement to continue LHRH agonist therapy for the duration of the study. LHRH agonist therapy may be discontinued in women > 60 years of age.
  • Eastern Cooperative Oncology Group (ECOG) Performance Status of 0 or 1.
  • Life expectancy >= 6 months.
  • Participants with Endocrine therapy (ET)-resistant disease and ET-sensitive disease as defined in the protocol.

Exclusion criteria

Exclusion Criteria:

  • Advanced, symptomatic, visceral spread at the time of study entry that is at risk of life-threating complications and for which treatment with cytotoxic chemotherapy is considered appropriate per local treatment guidelines.
  • Symptomatic, untreated, or actively progressing CNS metastases.
  • History of systemic anti-cancer therapy for unresectable locally advanced breast cancer or metastatic breast cancer.
  • Malabsorption condition or other gastrointestinal (GI) conditions/surgeries that the investigator assesses may significantly interfere with enteral absorption.
  • History of malignancy within 3 years prior to screening, except for cancer under investigation in this study and malignancies with a negligible risk of metastasis or death.
  • Known allergy or hypersensitivity to any component of the study treatments.
05

Study design

Phase
Phase 1
Primary purpose
Treatment
Allocation
Randomized
Intervention model
Sequential assignment
Masking
None (open label)
Enrollment
165 participants (estimated)

Study arms

  • Experimental
    GDC-4198 with fulvestrant

    During safety run-in stage, participants will receive GDC-4198, higher dose in combination with fulvestrant, as per a pre-defined dosing regimen during Cycle 1 (1 cycle=28 days). During expansion stage, participants will receive GDC-4198, either lower or higher dose in combination with fulvestrant, as per a pre-defined dosing regimen during each cycle until unacceptable toxicity or disease progression.

    Drug: GDC-4198 · Drug: Fulvestrant

  • Experimental
    GDC-4198 with letrozole

    During expansion stage, participants will receive GDC-4198, either lower or higher dose in combination with letrozole, as per a pre-defined dosing regimen during each cycle until unacceptable toxicity or disease progression.

    Drug: GDC-4198 · Drug: Letrozole

  • Experimental
    GDC-4198 with giredestrant

    During expansion stage, participants will receive GDC-4198, either lower or higher dose in combination with giredestrant, as per a pre-defined dosing regimen during each cycle until unacceptable toxicity or disease progression.

    Drug: GDC-4198 · Drug: Giredestrant

Interventions

  • DrugGDC-4198

    Participants will receive GDC-4198 as per the schedule described in the protocol.

    Also known as: RGT-419B, RO7840734

  • DrugFulvestrant

    Participants will receive fulvestrant as per the schedule described in the protocol.

  • DrugLetrozole

    Participants will receive letrozole as per the schedule described in the protocol.

  • DrugGiredestrant

    Participants will receive giredestrant as per the schedule described in the protocol.

    Also known as: GDC-9545, RO7197597

06

What researchers measure

Primary outcomes

  1. Incidence and Severity of Adverse Events (AEs)

    Time frame: Approximately 30 months

Secondary outcomes

  1. Plasma Concentration of GDC-4198

    Time frame: Approximately 30 months

  2. Objective Response Rate (ORR)

    Time frame: Approximately 30 months

  3. Clinical Benefit Rate (CBR)

    Time frame: Approximately 30 months

07

Study locations

No study locations are listed for this record.

08

References and documents

Individual participant data

Plan to share: No

09

Timeline

1 registry update since Sep 25, 2026
ElapsedEstimatedEstimated, not yet reachedSimilar studies: half by the dot; the band is the middle halfHalf of similar studies reached it by the dot; the band is the middle half, from a quarter to three quarters

Start is estimated for Dec 2026; primary completion for Aug 2030, 44 months later.

Of 306 industry-sponsored phase 1 interventional studies under Breast Neoplasms, half reached primary completion within 42 months of starting (the median), counting those still running; a quarter within 22 and three quarters within 57. This study's planned 44 months is close to that.

Counting every sponsor, half of 645 studies reached it within 45 months; a quarter within 25 and three quarters within 66.

How these figures are worked out, and which studies are left out of them.

Registered
Oct 5, 2026
First posted
Oct 9, 2026
StartEst.
Dec 15, 2026
Primary completionEst.
Aug 15, 2030
CompletionEst.
Aug 15, 2030
Last update
Oct 9, 2026
What these dates mean
Start.
When the first participant enrolled; while estimated, when the study expects to open to recruitment.
Primary completion.
When the last participant was examined or treated to collect data for the study's main question, its primary outcome. A study that stopped early gives the date its data collection stopped.
Completion.
When the last participant's last visit took place, for every outcome, secondary ones and side effects included: the end of the study. Often later than primary completion, sometimes the same day.
Actual and Est.
Actual means the registry says the date has happened. Est. (estimated) is a date the sponsor plans or expects. It can still move, and the sponsor is expected to change it to actual once it has passed.
Registered
First appeared on the registry. No changes since
Oct 9, 2026
Show all 1 update
  1. Oct 9, 2026
    First appeared on the registry

From the registry record's own update history. This site started tracking changes on Sep 25, 2026; for anything earlier, see the record history on ClinicalTrials.gov ↗

10

Registry details

Key details

Study ID
NCT07867262
Lead sponsor
Genentech, Inc.
Responsible party
Sponsor
First posted
Oct 9, 2026
Start date
Dec 15, 2026 (estimated)
Primary completion
Aug 15, 2030 (estimated)
Completion
Aug 15, 2030 (estimated)
Last update
Oct 9, 2026

Study contacts

Reference Study ID Number: GO46022 https://forpatients.roche.com/ No attachments to email below.
Contact
global-roche-genentech-trials@gene.com
888-662-6728
Fastest response: use the inquiry form. https://www.gene.com/contact-us/submit-medical-inquiry
Contact
Clinical Trials
study director · Genentech, Inc.

Oversight

Data monitoring committee
No
FDA-regulated drug
Yes
FDA-regulated device
No
View the source record on ClinicalTrials.gov ↗

Not currently enrolling

This study is not yet recruiting, as verified in Oct 2026. You cannot join it, but the record below documents what was studied.

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Discussion

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Studies of the drugs tested here: Fulvestrant · Letrozole · Giredestrant

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