Home › Trials › NCT05573555

Evaluating a new treatment for advanced or metastatic breast cancer

TACTIVE-U: AN INTERVENTIONAL SAFETY AND EFFICACY PHASE 1B/2, OPEN-LABEL UMBRELLA STUDY TO INVESTIGATE TOLERABILITY, PK, AND ANTITUMOR ACTIVITY OF VEPDEGESTRANT (ARV-471/PF-07850327), AN ORAL PROTEOLYSIS TARGETING CHIMERA, IN COMBINATION WITH OTHER ANTICANCER TREATMENTS IN PARTICIPANTS AGED 18 YEARS AND OVER WITH ER+ ADVANCED OR METASTATIC BREAST CANCER, SUB-STUDY B (ARV-471 IN COMBINATION WITH RIBOCICLIB)

Phase1; Phase2 Interventional Pfizer · NCT05573555

This study is testing a new medication called ARV-471 combined with ribociclib to see if it helps people with advanced breast cancer that hasn't responded to other treatments.

Quick facts

PhasePhase1; Phase2
Study typeInterventional
Enrollment47 (estimated)
Ages18 Years and up
SexAll
SponsorPfizer Industry-sponsored
Drugs / interventionsradiation
Locations45 sites (Palo Alto, California and 44 other locations)
Trial IDNCT05573555 on ClinicalTrials.gov

What this trial studies

This clinical trial aims to assess the safety and effectiveness of a medication called ARV-471 when combined with ribociclib in patients with advanced or metastatic breast cancer that is estrogen receptor positive and has not responded to previous treatments. Participants will take both medications orally once a day at home, and their experiences will be monitored to gather data on the treatment's impact. The study is part of a larger umbrella initiative, TACTIVE-U, which includes multiple sub-studies focusing on different combinations of therapies for breast cancer.

Who should consider this trial

Good fit: Ideal candidates are individuals with advanced or metastatic breast cancer that is estrogen receptor positive and has not responded to prior therapies.

Not a fit: Patients with life-threatening complications, significant lung function deterioration, or newly diagnosed symptomatic brain metastases may not benefit from this study.

Why it matters

Potential benefit: If successful, this treatment could provide a new effective option for patients with advanced or metastatic breast cancer who have limited treatment alternatives.

How similar studies have performed: Other studies have shown promise with similar approaches in treating advanced breast cancer, indicating potential for success in this trial.

Eligibility criteria

Show full inclusion / exclusion criteria 
Inclusion Criteria:

* histological or cytological diagnosis of ER+ and HER2- advanced/metastatic breast cancer that is not amendable to surgical resection with curative intent (≥1% ER+ stained cells on the most recent tumor biopsy).
* prior anticancer therapies: at least 1 and no more than 2 lines of prior therapies for advanced/metastatic disease; 1, and only 1, line of any CDK4/6 inhibitor-based regimen is required (in any setting eg adjuvant, metastatic)
* at least 1 measurable lesion as defined by RECIST v1.1.
* ECOG PS ≤1.

Exclusion Criteria:

* visceral crisis at risk of life-threatening complications in the short term
* known history of drug-induced pneumonitis or other significant symptomatic deterioration of lung functions.
* newly diagnosed brain metastases, or symptomatic CNS metastases, carcinomatous meningitis, or leptomeningeal disease. Participants with a history of CNS metastases or cord compression are eligible if they have been definitively treated, clinically stable and discontinued anti-seizure medications and corticosteroids for at least 14 days prior to enrollment in the of study.
* history of any other tumor malignancies within the past 3 years, except for the following: (1) adequately treated basal or squamous cell carcinoma of the skin; (2) curatively treated in situ carcinoma of the cervix.
* inflammatory breast cancer
* impaired cardiovascular function or clinically significant cardiovascular diseases
* concurrent administration of medications, food, or herb supplements that are strong inhibitors and strong/moderate inducers of CYP3A and drugs known to predispose to Torsade de Pointes or QT interval prolongation.
* renal impairment, not adequate liver function and/or bone marrow function
* known active infection

Where this trial is running

Palo Alto, California and 44 other locations

Study contacts

How to participate

  1. Review the eligibility criteria above with your treating physician.
  2. Visit the official trial page on ClinicalTrials.gov for the most current contact information and recruitment status.
  3. Contact the listed study coordinator or principal investigator to request pre-screening. Pre-screening is free and never obligates you to enroll.
View on ClinicalTrials.gov → Find more trials like this →
Conditions Breast CancerTACTIVE-UUmbrella studyPROTACmetastatic breast cancer
Last reviewed 2026-06-13 by the Find a Trial editorial team. Information on this page is for educational purposes and is not medical advice. Always consult qualified healthcare professionals about clinical trial participation.