PFE - Arvinas falls 17% after early-stage data for Pfizer-partnered tumor therapy

Arvinas ( NASDAQ: ARVN ) shares reached the lowest level in more than two years on Monday after the company and its partner Pfizer ( NYSE: PFE ) announced data from the ongoing Phase 1/2 study for the protein degrader ARV-471 in combination with CDK4/6 inhibitor Ibrance (palbociclib).

The study is designed to evaluate the drug combo in estrogen receptor (ER) positive/human epidermal growth factor receptor 2 (HER2) negative (ER+/HER2-) breast cancer.

According to the companies, its ongoing Phase 1b portion indicated an increase in palbociclib exposure with ARV-471 compared to past pharmacokinetic data for palbociclib.

However, the incidence of grade 3/4 neutropenia, a known dose-related adverse reaction linked to palbociclib, stood at 76% in 200 mg ARV-471 and 125 mg palbociclib (n=21), with one patient discontinuing the treatment. The companies noted that neutropenia events were manageable with dose reductions for palbociclib.

Due to the recent data analysis, the companies plan to modify the VERITAC-3 Phase 3 study for the drug combo as first-line therapy in ER+/HER2- breast cancer. The trial is expected to begin enrollment in H1 2023, subject to the FDA's nod to the proposed change.

In November, Arvinas ( ARVN ) said the study could get underway in Q4 2022.

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