FDA Responds to Daiichi Sankyo-MSD's BLA for NSCLC

The US Food and Drug Administration (FDA) has issued a complete response letter regarding Daiichi Sankyo and MSD's biologics licence application (BLA) for patritumab deruxtecan, also known as HER3-DXd. This application sought accelerated approval for the use of the antibody-drug conjugate in adults with locally advanced or metastatic non-small cell lung cancer (NSCLC) that has mutations in the epidermal growth factor receptor (EGFR) and who have previously undergone two or more systemic therapies.

The FDA's response was primarily concerned with inspection findings at a third-party manufacturing facility. Interestingly, the letter did not raise any issues about the efficacy or safety data of patritumab deruxtecan that was submitted.

Ken Takeshita, the global head of research and development at Daiichi Sankyo, emphasized their commitment to collaborating with both the FDA and the third-party manufacturer to address the concerns promptly. Their goal is to make the first HER3-targeted therapy available to patients who have previously been treated for EGFR-mutated NSCLC.

The application was supported by early results from the HERTHENA-Lung01 clinical trial, a multicentre, global, open-label, two-arm Phase II study. This trial assessed the safety and efficacy of the drug in 225 patients and demonstrated an objective response rate of 29.8%, which included one complete response and 66 partial responses. The median duration of the response was recorded at 6.4 months.

The safety profile of patritumab deruxtecan observed in this Phase II trial was consistent with earlier Phase I trials focused on NSCLC. Some of the most common severe treatment-emergent adverse events included thrombocytopenia, neutropenia, anemia, leukopenia, fatigue, hypokalemia, and asthenia.

Marjorie Green, head of global clinical development oncology and senior vice-president at Merck Research Laboratories, noted that patients with previously treated EGFR-mutated NSCLC frequently face recurrence and have limited treatment options. She reiterated the company's commitment to working with Daiichi Sankyo and the FDA to expedite the availability of patritumab deruxtecan for these patients.

In a related development, MSD signed a definitive agreement in January 2024 to acquire Harpoon Therapeutics for $680 million. This acquisition aims to strengthen MSD's portfolio in immunotherapy for cancer treatment.