Merck, Daiichi Sankyo Pull FDA Application For Lung Cancer Therapy: Retail Terms It A ‘Huge Flop’

The decision is based on results from a late-stage trial in which the drug failed to prolong patients' lives, the companies stated.
Medicine pill is seen with Merck logo displayed on a screen in the background in this illustration photo taken in Poland on November 5, 2021. (Photo by Jakub Porzycki/NurPhoto via Getty Images)
Medicine pill is seen with Merck logo displayed on a screen in the background in this illustration photo taken in Poland on November 5, 2021. (Photo by Jakub Porzycki/NurPhoto via Getty Images)
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Anan Ashraf·Stocktwits
Updated Jul 02, 2025 | 8:31 PM GMT-04
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Merck & Co Inc. (MRK) and Daiichi Sankyo on Thursday said that the companies have withdrawn their application to the U.S. Food and Drug Administration (FDA) seeking permission to commercialize Patritumab Deruxtecan for the treatment of adult patients with a particular type of lung cancer.

The decision is based on results from a late-stage trial in which the drug failed to prolong patients' lives, the companies said.

The companies had submitted the application for the treatment of adult patients with locally advanced or metastatic EGFR-mutated non-small cell lung cancer (NSCLC) previously treated with two or more systemic therapies. NSCLC accounts for about 87% of all lung cancers.

Patritumab Deruxtecan was discovered by Japan-based healthcare company Daiichi Sankyo and is being jointly developed by Daiichi Sankyo and Merck.

It is an antibody drug conjugate (ADC) or a cancer treatment that combines targeted therapy and chemotherapy. ADCs deliver very powerful chemotherapy drugs to specific cancerous cells, damaging or destroying cancerous cells without harming nearby healthy cells.

Daiichi Sankyo and Merck entered into a global development and commercialization agreement for three of the former’s ADC candidates in October 2023, including Patritumab Deruxtecan, Ifinatamab Deruxtecan, and Raludotatug Deruxtecan.

Under the $22 billion deal, Merck and Daiichi decided to jointly develop the ADC candidates worldwide except in Japan, where Daiichi maintained exclusive rights.

Ken Takeshita, global head of research and development at Daiichi Sankyo, said that the company is disappointed with the results of the recent trial but is conducting further analyses to identify patients that may benefit from Patritumab Deruxtecan.

The companies are currently studying the therapy across multiple types of cancers..

On Stocktwits, retail sentiment around Merck stayed unmoved within the ‘bearish’ territory over the past 24 hours while message volume remained at ‘low’ levels.

MRK's Sentiment Meter and Message Volume as of 12:18 p.m. ET on May 29, 2025 | Source: Stocktwits
MRK's Sentiment Meter and Message Volume as of 12:18 p.m. ET on May 29, 2025 | Source: Stocktwits

A Stocktwits user believes the news is “a huge flop” for Merck.

MRK stock is down by 23% this year and by about 40% over the past 12 months.

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