MedicalResearch.com Interview with: Presented by Dr. Maura N. Dickler MD Associate member of the Breast Medicine Service at Memorial Sloan Kettering Cancer Center and Weill Medical College of Cornell University in New York Medical Research: What is the background for this study? This year, breast cancer will claim the lives of nearly 40,000 women in the United States, and up to half of these women will have a disease that is driven by the estrogen receptor.

• Although medicines have been approved for the treatment of hormone receptor-positive breast cancer for decades, more treatment options are needed.
• Resistance to endocrine therapies causes morbidity and mortality for women with metastatic estrogen receptor-positive (ER+) breast cancer as many patients relapse or develop resistance to available hormonal agents via estrogen-dependent and estrogen-independent mechanisms.
• Dual-acting investigational Selective Estrogen Receptor Degrader (SERDs) could potentially lead to a new treatment option for people with hormone receptor-positive breast cancer and may help overcome resistance to current anti-hormonal medicines.
• GDC-0810 is a dual-acting investigational next-generation oral SERD that works in a number of ways to prevent estrogen fueling tumor growth. It is not only designed to target the estrogen receptor (ER) as an antagonist, but also to cause degradation of the ER protein. In preclinical studies, GDC-0810 was shown to induce tumor regressions in both tamoxifen sensitive and tamoxifen resistant tumor models in vivo.

Medical Research: What are the main findings?

• Clinical data from the dose-escalation portion of a Phase I/IIa study evaluating GDC-0810 appears to have an acceptable safety profile with encouraging anti-tumor activity in postmenopausal women with advanced breast cancer positive for the estrogen receptor (ER), all of whom were previously treated with standard endocrine therapy.
• Promising anti-tumor activity was observed in 38% of patients on study for six months or longer. At all doses tested, there was robust engagement of the estrogen receptor by GDC-0810 as demonstrated by fluoroestradiol (FES) PET scans.  Overall, the most common adverse events of any grade related to GDC-0810 were diarrhea, nausea and fatigue.

(more…)