Merck and Daiichi Sankyo Withdraw Lung Cancer Drug Application Amid Disappointing Survival Data

Merck & Co. and Daiichi Sankyo have voluntarily withdrawn their U.S. Food and Drug Administration (FDA) application for patritumab deruxtecan, an investigational antibody-drug conjugate (ADC) targeting HER3-positive non-small cell lung cancer (NSCLC) with EGFR mutations. The decision comes after the drug failed to significantly improve overall survival in a pivotal Phase III trial, dealing a blow to the companies' $22 billion alliance.

Setback for Promising ADC Therapy

Patritumab deruxtecan, also known as HER3-DXd, was being evaluated as a treatment for locally advanced or metastatic NSCLC in patients with EGFR mutations. The withdrawal follows a topline readout from the Phase III HERTHENA-Lung02 trial, which compared the ADC to doublet chemotherapy in nearly 280 patients.

While the trial met its primary efficacy endpoint of progression-free survival in September 2024, the latest data revealed that the drug did not significantly improve overall survival. This outcome, coupled with discussions with the FDA, prompted Merck and Daiichi Sankyo to pull their application.

Dr. Eliav Barr, Chief Medical Officer of Merck Research Laboratories, commented on the challenges faced: "This is a reminder of how challenging it can be to treat these patients with EGFR-mutated non-small cell lung cancer in the second and later line settings."

Impact on Merck's Strategic Pipeline

The withdrawal represents a significant setback for Merck, which has been actively seeking to diversify its portfolio beyond its blockbuster cancer immunotherapy, Keytruda. With Keytruda facing patent expiration later this decade, Merck has turned to ADCs as a potential avenue for growth.

The company's share price has fallen nearly 40% over the past 12 months, reflecting growing investor skepticism about its plans to offset future losses from Keytruda's patent expiration. The alliance with Daiichi Sankyo, potentially worth up to $22 billion, was seen as a key component of Merck's strategy to bolster its pipeline with promising ADC therapies.

Future Directions and Ongoing Development

Despite this setback, both Merck and Daiichi Sankyo remain committed to the broader development of patritumab deruxtecan. Ken Takeshita, Global Head of R&D at Daiichi Sankyo, stated, "We remain confident in the broad development of [our drug], which includes trials across 15 types of cancer."

The companies are now conducting further biomarker analyses to better identify lung cancer patients who might benefit from treatment. They plan to present the full study results from the HERTHENA-Lung02 trial at the upcoming American Society of Oncology Meeting.

As the pharmaceutical industry continues to grapple with the challenges of developing effective therapies for difficult-to-treat cancers, this withdrawal underscores the importance of overall survival data in determining the true clinical benefit of new oncology drugs.