Arvinas (ARVN) and Pfizer Release Positive Phase 1b Trial Data

Arvinas, Inc. (NASDAQ: ARVN) and Pfizer Inc. (NYSE: PFE) have released updated clinical data from the phase 1b trial of vepdegestrant in combination with palbociclib (Ibrance®). The updated data, presented at the 2024 European Society for Medical Oncology (ESMO) Breast Cancer Annual Congress, revealed significant improvements in several key clinical metrics compared to the data presented at the San Antonio Breast Cancer Symposium (SABCS) in December 2023.

The clinical benefit rate (CBR) across all dose levels was reported at 63%, with a CBR of 72% in patients with mutant ESR1 and 53% in patients with wild-type ESR1. Furthermore, at the recommended phase 3 dose of 200 mg vepdegestrant in combination with palbociclib, the median progression-free survival (PFS) was 13.9 months, showing an increase from the previously reported 11.2 months. The objective response rate (ORR) in evaluable patients with measurable disease at baseline was 42%, with a median duration of response (DOR) in responders of 14.6 months.

Exploratory circulating tumor DNA (ctDNA) analyses revealed a marked reduction (median change, -98.9%) in tumor fraction after one treatment cycle, regardless of ESR1 mutant status, with sustained decreases in mutant ESR1 ctDNA levels through multiple treatment cycles.

The safety profile of vepdegestrant plus palbociclib remained consistent with previously reported data, with grade 3/4 treatment-related adverse events including neutropenia (91%) and decreased white blood cell count (15%). Notably, no grade 5 treatment-related adverse events or febrile neutropenia were reported. The majority of grade 4 neutropenia events occurred in the first cycle of treatment, and occurrences of grade 3/4 neutropenia decreased following palbociclib dose reductions.

Vepdegestrant is being co-developed by Arvinas and Pfizer and is being evaluated as a potential monotherapy in the second-line setting in the ongoing phase 3 VERITAC-2 trial and in the first-line setting in combination with palbociclib in the ongoing study lead-in cohort of the phase 3 VERITAC-3 trial.

The U.S. Food and Drug Administration (FDA) has granted vepdegestrant fast track designation as a monotherapy in the treatment of adults with ER+/HER2* locally advanced or metastatic breast cancer previously treated with endocrine-based therapy.

Today the company's shares have moved 2.6% to a price of $33.18. For the full picture, make sure to review Arvinas's 8-K report.

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