FDA Rejects Merck-Daiichi’s HER3-Targeted ADC Due to Manufacturing Issues

1. FDA Rejection: The U.S. Food and Drug Administration (FDA) has rejected Merck and Daiichi Sankyo's HER3-targeted antibody-drug conjugate (ADC) patritumab deruxtecan due to manufacturing concerns at a third-party facility.
2. Treatment Indication: Patritumab deruxtecan was intended to treat locally advanced or metastatic non-small cell lung cancer (NSCLC) with EGFR mutations in patients who have received prior treatment.
3. Manufacturing Issues: The FDA's complete response letter (CRL) cited issues with the third-party manufacturing facility, but did not raise concerns about the drug's efficacy or safety data.
4. Partnership: Merck and Daiichi Sankyo have a substantial joint venture, valued at up to $22 billion, which includes the development and commercialization of patritumab deruxtecan and other ADCs.
5. ADC Technology: Patritumab deruxtecan utilizes Daiichi Sankyo's proprietary DXd ADC platform, which targets the HER3 protein and delivers a toxic payload to selectively eliminate tumor cells.
6. Clinical Trials: The drug showed a 29.8% objective response rate in the HERTHENA-Lung01 pivotal Phase II trial, with a median duration of response of 6.4 months.
7. Future Plans: Merck and Daiichi Sankyo will work closely with the FDA and the third-party manufacturer to address the manufacturing issues and bring the treatment to patients as soon as possible.