Camizestrant in combination with ribociclib as first-line treatment for advanced, hormone receptor-positive, and HER2-negative breast cancer

Breast cancer (mammary carcinoma) is a malignant disease of the breast tissue in which cells in the breast multiply uncontrollably. Treatment depends on various factors, including the patient’s overall health, the stage of the disease, and the biological characteristics of the tumor, such as the presence of hormone receptors (estrogen receptor-positive, progesterone receptor-positive) and HER2 status. Hormone receptor-positive breast cancer means that the cancer cells express estrogen receptors. The hormone estrogen can promote the growth of cancer cells via these receptors. The human epidermal growth factor receptor 2 (HER2) is a protein located on the surface of cells. HER2-negative means that the cancer cells express this protein only to a limited extent—that is, not in large quantities—on their surface. This study is investigating a combination of two active ingredients: Camizestrant belongs to the class of selective estrogen receptor degraders (SERDs). These active ingredients bind to the estrogen receptor, degrade it, and thereby block its activity, which prevents estrogen from promoting tumor growth. Ribociclib belongs to the class of cyclin-dependent kinase 4/6 inhibitors (CDK4/6 inhibitors). These drugs block the enzymes CDK4 and CDK6, which drive cell division during the cell cycle, and can thus inhibit the proliferation of cancer cells. Both drugs are taken once daily as a tablet.

The goal of this Phase 3 study is to investigate the efficacy, safety, and tolerability of the combination of camizestrant and ribociclib in patients. To this end, the study will examine, among other things, how many patients are still alive and have not required further cancer treatment two years after the start of treatment. This is a multicenter study that is not randomized and includes only one treatment group. This means there is no control group. All patients receive the same treatment. The study is open-label (not blinded), meaning that both the patients and the study physicians know which medications are being administered.

Eligible participants are adult patients aged 18 and older with hormone receptor-positive, HER2-negative breast cancer that is already advanced and can no longer be cured by surgery or radiation therapy. A prerequisite is that the advanced disease has not yet been treated with systemic cancer therapy. The disease may have been advanced from the outset (de novo Stage 4) or may have returned after previous treatment administered at an early stage (recurrence). In the case of such a recurrence, at least 12 months must have elapsed since the last dose of an adjuvant aromatase inhibitor—a form of antihormonal therapy—without the disease having progressed during this treatment. Women before or around menopause, as well as male patients, may participate only if they are additionally treated with monthly LHRH agonists (goserelin or leuprorelin).