This study is focused on treating Advanced Breast Cancer that is ER-positive and HER2-negative. This means the cancer cells have receptors for estrogen, a female hormone, but do not have high amounts of a specific protein that helps cancer grow. The goal of the study is to compare the effectiveness of two different treatment combinations. One group will receive palazestrant, also known as OP-1250, along with ribociclib and a gonadotropin releasing hormone analogue, which is a medication used to lower hormone levels. The other group will receive letrozole and ribociclib, along with a placebo.
Participants in the study will take these medications over a period of time to see how they affect the growth of the cancer. The study looks at progression-free survival, which is the length of time during and after treatment that a person lives with the disease without it getting worse. Other factors being observed include overall survival, which is the total length of time a person remains alive, and how well the tumor responds to the medication. The study also monitors how well the body tolerates the drugs and how they impact daily life through patient questionnaires.
Who Can Join the Study?
You must be an adult, meaning an adult female or male.
You must have ER+ (estrogen receptor-positive) and HER2- (human epidermal growth factor receptor 2-negative) breast cancer that is either locally advanced (meaning it has spread to nearby tissues) or metastatic (meaning it has spread to other parts of the body) and cannot be completely cured by current treatments.
The cancer must be evaluable, which means it can be measured using specific medical rules (called RECIST 1.1) or it is located only in the bones.
The cancer must be de novo (newly diagnosed at an advanced stage) or it must have returned (recurrence) at least 12 months after you finished adjuvant endocrine therapy (hormone treatment given after primary treatment to prevent cancer from coming back).
You must have an ECOG performance status of 0 or 1, which is a scale used by doctors to measure how well you can perform daily activities and your overall level of functioning.
You must have adequate hematologic, hepatic, and renal functions, which means your blood counts, liver health, and kidney health must be at safe and normal levels.
Female participants can be in any stage of menopause (the time in a woman’s life when menstruation stops).
Male participants and females who have not yet gone through menopause must be willing to take a GnRH agonist, which is a type of medication used to lower hormone levels.
Who Cannot Join the Study?
The cancer has returned while receiving adjuvant endocrine therapy, which is hormone treatment given after primary treatment to prevent the cancer from coming back.
The patient is currently taking or has previously taken systemic anti-cancer therapy, which means medicines that travel through the entire body to fight cancer, specifically for ER+, HER2- advanced breast cancer.
The patient has previously used medications called fulvestrant, elacestrant, or any experimental hormone treatments.
The patient has a history of allergic reactions to the medications used in this study.
The patient has any medical reasons why they should not take letrozole or ribociclib.
The patient has cancer that has spread to the central nervous system (the brain and spinal cord) and is causing symptoms, such as carcinomatous meningitis (cancer spreading to the protective layers covering the brain and spinal cord), leptomeningeal disease (cancer in the fluid surrounding the brain and spine), or spinal cord compression (the tumor pressing on the spinal cord) that needs urgent care.
Ribociclib is an oral medication used as part of the treatment to help slow the growth of cancer cells in patients with advanced breast cancer.
Palazestrant is an oral medication being tested in this study to help block the hormones that allow certain types of breast cancer cells to grow.
Letrozole is an oral medication used as a comparison treatment to help lower the amount of estrogen in the body, which can help stop the growth of some breast cancers.
ER+, HER2- Advanced Breast Cancer – This is a type of breast cancer where the cells have receptors for estrogen and the disease has reached an advanced stage. The cancer cells grow and spread because they use estrogen to fuel their development. In this specific form, the cells do not have high levels of a protein called HER2. As the disease progresses, the cancer cells can move from the original site in the breast to other parts of the body. The growth is driven by the presence of specific hormone receptors on the surface of the cancer cells.
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