Pfizer Takes Aim at Keytruda in New Phase 3 Lung Cancer Study: What Investors Should Know

Pfizer Inc (PFE) announced an update on their ongoing clinical study.

Study Overview: Pfizer is running a large Phase 3 trial called “AN INTERVENTIONAL PHASE 3, DOUBLE-BLIND, RANDOMIZED STUDY TO EVALUATE EFFICACY AND SAFETY OF PF-08634404 IN COMBINATION WITH CHEMOTHERAPY VERSUS PEMBROLIZUMAB IN COMBINATION WITH CHEMOTHERAPY IN ADULT PARTICIPANTS WITH LOCALLY ADVANCED OR METASTATIC NON-SMALL CELL LUNG CANCER.” The goal is to see if its new cancer drug PF-08634404, when added to standard chemotherapy, can outperform Merck’s widely used pembrolizumab regimen in adults with advanced non-small cell lung cancer (NSCLC). This is a head-to-head test against a current standard of care and, if positive, could reshape a key segment of the lung cancer market.

Intervention/Treatment: The study compares two main treatments. The experimental arms use PF-08634404, given by IV, together with one of two chemotherapy regimens, followed by maintenance with PF-08634404 alone or with chemotherapy. The control arms use pembrolizumab, also by IV, with similar chemotherapy backbones, followed by pembrolizumab-based maintenance. Both approaches aim to slow or stop the growth of advanced NSCLC and extend survival in patients who cannot be cured with surgery or radiation.

Study Design: This is an interventional Phase 3 study with random assignment, meaning participants are placed into treatment groups by chance, like a coin flip. It uses a parallel design, so each participant stays on the same treatment path once assigned. The study is double-blind: neither patients nor doctors know whether PF-08634404 or pembrolizumab is being given, reducing bias. The main goal is treatment-focused, looking at how well each option controls the cancer and how safe it is over time.

Study Timeline: The trial was first submitted on 28 October 2025, marking the formal start of regulatory and site setup activity. Primary completion, when the main results on effectiveness are usually collected, is expected several years later, which will be the first key data point for investors. Final study completion will occur after longer follow-up, giving more detail on survival and safety. The record was last updated on 22 January 2026, confirming that the design and status are current and that the trial is actively moving forward in the recruiting phase.

Market Implications: For investors, this trial is notable because Pfizer is directly challenging pembrolizumab, a cornerstone therapy for NSCLC and a major revenue driver for Merck. A strong showing from PF-08634404 could open a large, durable revenue stream in first-line lung cancer, support a re-rating of Pfizer’s oncology portfolio, and improve sentiment after recent pressure on its COVID-related sales. For Merck, the study adds competitive risk to one of its flagship franchises, though results are still years away. The broader sector may see renewed attention on immuno-oncology combinations, with peers watching closely for signals that standard PD-1–based regimens can be displaced. In the near term, the update mainly underscores Pfizer’s commitment to high-value oncology assets, which can support long-term oriented investors but is unlikely to move the stock on its own before data readouts.

The study is currently ongoing and actively updated, with further operational and clinical details available on the ClinicalTrials.gov portal under the listed identifier.

To learn more about PFE’s potential, visit the Pfizer Inc drug pipeline page.