Phase 3 Results

SideOut-BCA-003 / 35 patients / Complete

Utilizing Multiomic Profiling to Advanced Diagnostics to Identify CDK 4/6 Inhibitor Response Predictors and a Post-treatment Multiomic Signature for Patients with ER+/HER-2 Metastatic Breast Cancer

In the area of precision medicine, molecular information (e.g. changes at the DNA, RNA, and protein level) have become extremely important in selecting the therapeutic course of breast cancer patients. The ability to tailor a therapy to any given tumor is highly dependent upon the identification of molecular alterations that can predict a patient’s response to treatment. Identification of these markers can improve treatment efficacy and subsequently progression-free and overall survival.

Recently, a new therapeutic approach has been approved by the FDA for post-menopausal women affected by ER positive/HER2 negative metastatic breast cancers. This therapeutic approach combines conventional anti-estrogen hormonal therapy with compounds modulating the cyclin-dependent kinase 4 and 6 (cdk4/6) proteins. These proteins modulate a tumor cell’s ability to replicate and grow by regulating the cell cycle. Although this new treatment is highly beneficial as a whole, 20-30% of metastatic breast cancers patients have short term benefit from this treatment and they rapidly develop resistance. Despite several attempts to find molecular markers able to predict response to cdk4/6 inhibitors, diagnostic tests able of identifying women that are resistant to treatment are still unavailable. The Side out 3 trial proposes an innovative approach for understanding the molecular mechanisms that drive resistance to cdk4/6 inhibitors and identify molecular markers that can be used to predict response. The study goes beyond genomic characterization of individual tumors and proposes a protein-centered approach to build functional molecular profiles for patients that are sensitive and resistant to cdk4/6 inhibitors.

This is an open-label, multicenter study in open to patients with metastatic breast cancer who are candidates for standard first line treatment with the ckd 4/6 inhibitors palbociclib or ribociclib plus endocrine therapy. To be eligible, patients must have received no prior chemotherapeutic or hormonal regimen for metastatic disease. However, patients may still be considered eligible if they have already started treatment with endocrine therapy (an aromatase inhibitor or fulvestrant) plus palbociclib or ribociclib for no longer than 4 weeks prior to study enrollment, as long as they meet all other eligibility criteria. Eligible patients must have had a diagnostic biopsy of the metastatic lesion no more than 4 months prior to study enrollment and with sufficient tissue to complete the proposed biomarker analysis. Patients who develop disease progression within the first 12 months of starting palbociclib or ribociclib plus endocrine therapy will be eligible for an optional additional tissue biopsy at time of disease progression to repeat the analysis at time of disease progression and obtain real-time (10-14-day turn-around) multi-omic data produced under College of American Pathologist (CAP)/Clinical Laboratory Improvement Amendments (CLIA) development and/or compliant practices.


  • Upon completion of the trial.

Poster Presentations

  • Upon completion of the trial.

For more details about the trial or to learn about how to become a participant, contact Bryant Dunetz at [email protected] or 703-615-8740

Join our fight in the match against stage IV breast cancer.