Pfizer and Arvinas disclose mixed breast cancer survival findings for PROTAC degrader

Pfizer and Arvinas reported that their estrogen receptor degrader failed to meet positive results in a major stage of its first phase 3 trial. However, it highlighted success among certain patient groups to demonstrate potential regulatory approval.
The medical compound vepdegestrant functions as an oral PROteolysis TArgeting Chimera (PROTAC) ER degrader. The phase 3 study conducted a comparison of vepdegestrant versus AstraZeneca’s Faslodex hormone therapy within a patient population of 624 individuals with ER+/HER2- advanced or metastatic breast cancer who received CDK 4/6 inhibitors and endocrine therapy previously.
According to the clinical trial data, the main study goal focused on PFS together with death because of any cause. According to Fierce Biotech, the main assessment in the federal database takes place among patients with estrogen receptor 1 mutations who were selected based on a blinded independent central review. This information comes from a Pfizer spokesperson.
The companies report positive PFS results in patients who demonstrate an estrogen receptor 1 mutation because the preset target hazard ratio of 0.6 was surpassed. The positive aspect did not convince investors since Arvinas’ stock declined by 50% to $8.60 per share following its $17.56 closing price.

At the time of analysis, the required number of events for measuring overall survival had not passed the cutoff threshold, indicating the companies could not reveal survival statistics. According to the study, Vepdegestrant exhibited “good tolerance” while maintaining its established “safety profiles” from previous investigations.
The Phase 3 data release today lacked extensive details about the trials, even though companies stated this information would be unveiled at medical events this year that aim to support regulatory filing processes.
The phase 3 data evaluation milestone for PROTAC degraders marks an important achievement because vepdegestrant indicates promising clinical benefits to metastatic breast cancer patients with estrogen receptor 1 mutations in their tumors, according to Arvinas’ CEO John Houston
The clinical care of ER+/HER2- metastatic breast cancer patients require substantial attention because these patients experience poor response rates to advanced endocrine therapies and sparse therapeutic alternatives after disease progression occurs, according to Pfizer oncology unit’s doctor Megan O’Meara in her statement.
VERITAC-2 data indicates that vepdegestrant provides patients with tumors containing ESR1 mutations extended disease progression time compared to fulvestrant treatment according to O’Meara.
Today’s outcome demonstrates that vepdegestrant has promising potential for ESR1m patient market approvals without reaching exceptional levels, according to Evercore ISI analysts.

The data set Arvinas in a good position for combining their therapy with upcoming fulvestrant-based 2L+ combos yet eliminate their pathway to distinct differentiation from future next-gen SERDs,” the analysts stated before labeling the outcome as “obviously blended.”
Vepdegestrant initiates a mechanism that draws the ubiquitin proteasome system to break down the ER structure. Previous to 2021, Pfizer entered the market with their product, and this year both companies announced they will run a phase 3 trial combining vepdegestrant with Pfizer’s investigational CDK4 inhibitor atirmociclib.