Studies for People with ER-Positive, HER2-Negative Advanced or Metastatic Breast Cancer (TACTIVE-U)

Treatment for ER-positive, HER2-negative metastatic breast cancer

Study Contact Information:

Pfizer Clinical Trial Contact Center

1-800-887-7002 (please reference the appropriate NCT number(s) from below when calling)

[email protected]

NCT Number:

Researchers at Pfizer and Arvinas are conducting the TACTIVE-U studies for people with ER-positive, HER2-negative advanced or metastatic breast cancer who have received at least one prior round of treatment and no more than two prior rounds of treatments for advanced or metastatic disease. One of these rounds of treatment must have included a CDK4/6 inhibitor (e.g., Kisqali, Verzenio, Ibrance).

The TACTIVE-U studies are looking at the safety of an oral study medicine, ARV-471 (also known as vepdegestrant), and how well it works when combined with other breast cancer medicines.

ARV-471 (vepdegestrant) is believed to work by targeting and degrading the estrogen receptor that is found in breast cancer cells. This prevents estrogen from connecting to the cancer cells, which may block estrogen’s effect on cancer cell growth.

More information about the TACTIVE-U studies can be found here:

What the Studies Involve

TACTIVE-U is open-label, so participants will know the medicines and the doses of the medicines they are receiving. Medicine doses may vary across participants in order to find the best dosing options for treating advanced or metastatic breast cancer.

There are no placebo (inactive medicine) groups in these studies

Any steps needed to screen, qualify or enroll

Type of treatment, dose, frequency, duration

All studies are researching ARV-471. ARV-471 is taken by mouth once a day at the same time in the morning with food.

The length of time you can expect to participate in any of these substudies depends upon a few things, including how you tolerate the medicine(s), how your cancer responds, and your personal choice.

Any additional screening, biopsies, appointments, monitoring

In all substudies, most study visits will include a physical examination, blood draws, heart monitoring, a discussion of how you are feeling, and other assessments and activities. Your tumor will be assessed every 8 weeks during the first year, and then every 12 weeks thereafter. This includes scans and measurement of skin/superficial lesions, if any. Bone scans will be carried out every 24 weeks.

Any additional follow ups or steps involved in participation and a timeline

Any compensation they may receive for treatment-related costs

Study Locations:

Lead Researchers/Study PIs and Affiliation:

Dr. Cynthia Ma, Washington University in St. Louis, St. Louis, MO

This Study is Open To:

People with the following may be eligible:

There are other requirements to join this study. The study doctor will help determine if this study is right for you.

This Study is Not Open To:

People with the following are not eligible:

There are other requirements to join this study. The study doctor will help determine if this study is right for you.


FORCE is a national nonprofit organization, established in 1999. Our mission is to improve the lives of individuals and families affected by adult hereditary cancers.