Pfizer: Arvinas And Pfizer Announce PROTAC® Protein Degrader ARV-471 Continues To Demonstrate Encouraging Clinical Benefit Rate In Patients With Locally Advanced Or Metastatic ER+/HER2- Breast Cancer

Arvinas, Inc. (Nasdaq: ARVN) and Pfizer Inc. (NYSE: PFE) today announced an update on Phase 1 dose escalation data of ARV-471, a novel PROTAC® estrogen receptor (ER) degrader, which is being co-developed for the treatment of patients with locally advanced or metastatic ER-positive/human epidermal growth factor receptor 2 (HER2)-negative breast cancer (ER+/HER2-). These data were presented as a virtual spotlight poster session at the 2021 San Antonio Breast Cancer Symposium (SABCS) and showed:

• ARV-471 demonstrated antitumor activity in CDK4/6 inhibitor-pretreated patients with a clinical benefit rate (CBR) of 40% in 47 evaluable patients. This heavily pretreated patient group had a median of four prior therapies.
• Three patients exhibited confirmed partial responses (PR) among the 38 patients with response evaluation criteria in solid tumors (RECIST) measurable lesions and at least one on-treatment tumor assessment.
• ARV-471 continues to demonstrate a favorable tolerability profile. Robust ER degradation was observed at all dose levels, reaching 89% reduction of ER.
Erika P. Hamilton, MD, Director of the Breast Cancer and Gynecologic Cancer Research Program and Principal Investigator, Sarah Cannon Research Institute, provided an overview of these data.

“These results continue to suggest that ARV-471 has the potential to become a first-in-category treatment, and a new standard of care, for ER+/HER2- breast cancer patients.” said John Houston, Ph.D., Chief Executive Officer at Arvinas. “The profile we see emerging for this drug candidate continues to validate our PROTAC® protein degrader platform, with ARV-471 showing clear signals of clinical benefit in a heavily pretreated patient population, including tumor shrinkage and good tolerability.”

These data support and further validate the evaluation of ARV-471 as a potential treatment for metastatic breast cancer that is ongoing in a Phase 1b combination study with IBRANCE® (palbociclib) and a Phase 2 monotherapy dose expansion study.

“We are excited by these results and believe ARV-471 is a promising ER-targeting investigational medicine,” said Chris Boshoff, M.D., Ph.D., Chief Development Officer, Oncology, Pfizer Global Product Development. “It is encouraging to see ARV-471 continuing to show durable efficacy and tolerability in heavily pre-treated patients with ER+ breast cancer who have limited treatment choices.”