The U.S. Food and Drug Administration (FDA) has issued a Complete Response Letter (CRL) for the Biologics License Application (BLA) seeking accelerated approval of patritumab deruxtecan by Daiichi Sankyo and Merck for the treatment of EGFR-mutated non-small cell lung cancer (NSCLC). This letter was issued due to findings from an inspection of a third-party manufacturing facility. Importantly, the CRL did not highlight any issues with the efficacy or safety data submitted. Patritumab deruxtecan is a potential first-in-class HER3-directed antibody-drug conjugate (ADC) developed by Daiichi Sankyo and Merck.
Patritumab deruxtecan, developed by Daiichi Sankyo and Merck, aims to treat EGFR-mutated NSCLC patients who have undergone previous systemic therapies. The companies are working closely with the FDA and the third-party manufacturer to address the feedback. The BLA is based on results from the HERTHENA-Lung01 pivotal phase 2 trial, showing an objective response rate (ORR) of 29.8% in 225 patients with EGFR-mutated locally advanced or metastatic non-small cell lung cancer. The trial data also showed a median duration of response of 6.4 months.
The HERTHENA-Lung01 trial observed a consistent safety profile for patritumab deruxtecan. Treatment discontinuation due to adverse events occurred in 7.1% of patients, with grade 3 or higher treatment-emergent adverse events (TEAEs) in 64.9% of participants. Common TEAEs included thrombocytopenia, neutropenia, anemia, leukopenia, fatigue, hypokalemia, and asthenia. Twelve patients developed treatment-related interstitial lung disease (ILD), with one grade 5 ILD event reported.
Global Trials Highlight Patritumab Deruxtecan’s Potential for Lung Cancer Treatment
The trial was global, involving participants from Asia, Europe, North America, and Oceania. The primary endpoint was ORR assessed by blinded independent central review (BICR), with secondary endpoints including duration of response, progression-free survival, and overall survival. Patritumab deruxtecan’s development continues through multiple clinical trials to address the unmet needs of cancer patients. Daiichi Sankyo and Merck have a global collaboration to develop and commercialize patritumab deruxtecan, among other ADCs. This collaboration leverages Daiichi Sankyo’s proprietary DXd ADC Technology, which uses monoclonal antibodies to deliver cytotoxic payloads to cancer cells expressing specific antigens. The companies aim to bring innovative treatments to patients with limited options.
The FDA granted Breakthrough Therapy Designation to patritumab deruxtecan in December 2021 for treating patients with EGFR-mutated locally advanced or metastatic non-small cell lung cancer. The drug is being evaluated in several clinical trials, including HERTHENA-Lung02, a phase 3 trial comparing its efficacy against platinum-based chemotherapy. Other trials include phase 1 and phase 2 studies in combination with other therapies for various cancer types.
Approximately 226,000 lung cancer cases were diagnosed in the U.S. in 2022, with NSCLC making up about 81% of these cases. EGFR mutations occur in roughly 1 in 5 NSCLC patients in Western populations. Patritumab deruxtecan targets HER3, a receptor tyrosine kinase associated with poor treatment outcomes. HER3 expression is found in a significant proportion of EGFR-mutated non-small cell lung cancer tumors, particularly after EGFR TKI treatment.
Daiichi Sankyo and Merck Drive Innovation in EGFR-Mutated Lung Cancer Treatments
Daiichi Sankyo and Merck’s ongoing efforts aim to address the high unmet medical needs of patients with EGFR-mutated non-small cell lung cancer. The companies are committed to advancing breakthrough science and ensuring patients have access to innovative therapies. This collaboration highlights the importance of strategic partnerships in the biopharmaceutical industry to develop and deliver life-saving treatments.
The DXd ADC portfolio of Daiichi Sankyo includes six ADCs in clinical development for various cancers. These investigational medicines are designed to deliver targeted therapies to cancer cells, minimizing damage to healthy tissues. The portfolio includes ENHERTU, a HER2-directed ADC, and datopotamab deruxtecan, a TROP2-directed ADC, both developed in collaboration with AstraZeneca. The development of these ADCs demonstrates the potential of targeted therapies in improving cancer treatment outcomes.
The FDA’s CRL for patritumab deruxtecan underscores the challenges and complexities in bringing new therapies to market. However, Daiichi Sankyo and Merck remain dedicated to resolving the issues and providing patients with effective treatment options. The success of these efforts could set a new standard for HER3-directed therapies and advance the field of oncology.
Resource: Merck, June 26, 2024

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