Daiichi, Merck's ADC outshines chemo in lung cancer trial

An antibody-drug conjugate developed by Daiichi Sankyo and Merck & Co. has achieved its primary objective in a Phase 3 clinical trial for lung cancer. The drug, patritumab deruxtecan, was shown to delay tumor progression more effectively than traditional chemotherapy in patients with a specific genetic mutation, according to a joint announcement by the companies on Tuesday.

The trial focused on individuals with non-small cell lung cancer (NSCLC) harboring a mutation in the EGFR gene. Participants in the study had previously experienced disease progression despite treatments targeting EGFR. Although the companies did not disclose detailed data from the trial, they emphasized that patritumab deruxtecan was tested against a combination of two chemotherapy drugs.

A year ago, Daiichi Sankyo had released promising data from a Phase 2 trial of the drug, which was compelling enough to warrant an application to the U.S. Food and Drug Administration (FDA) for accelerated approval. This data also led to a lucrative partnership with Merck, bringing in billions of dollars. However, the FDA ultimately rejected the application due to issues identified during an inspection of a manufacturing facility.

Daiichi and Merck's drug leverages an antibody to target a protein found on tumor cells, subsequently releasing a toxic chemical directly into the diseased cells. This approach is part of a broader class of treatments known as antibody-drug conjugates (ADCs). Initially, ADCs were primarily used for blood cancers, but their application has expanded to include solid tumors such as those found in the breast and bladder.

Daiichi Sankyo has played a significant role in advancing this field, particularly with its discovery of Enhertu, a breast cancer ADC that has become one of the most successful drugs in its class. Enhertu, co-marketed with AstraZeneca, generated $1.8 billion in revenue in the first half of this year alone.

The Japanese pharmaceutical company has developed a total of six ADCs featuring the deruxtecan chemotherapy agent. These include not only Enhertu but also other drugs in partnership with AstraZeneca and Merck, as well as one ADC developed independently by Daiichi. Merck itself has committed up to $22 billion in its deal with Daiichi, including $3 billion at the time of the agreement's signing last October. This partnership aligns with Merck's strategy to strengthen its drug pipeline, especially as it faces potential revenue declines later this decade with the expiration of key patents for its immunotherapy, Keytruda.

Patritumab deruxtecan is being tested for a type of lung cancer that is typically initially treated with EGFR-blocking small molecule drugs like AstraZeneca's Tagrisso. Over time, these cancers often become resistant to such treatments, leaving patients with limited and less effective options for further therapy. In the earlier Phase 2 trial, Daiichi reported that patients receiving patritumab deruxtecan had a median progression-free survival of six months. Additionally, about 30% of these patients experienced tumor shrinkage or complete disappearance.

In conclusion, the Phase 3 trial results mark a significant milestone for Daiichi Sankyo and Merck & Co. in their collaborative efforts to develop more effective treatments for lung cancer. While detailed data remains undisclosed, the success of patritumab deruxtecan in delaying tumor progression offers hope for patients with limited treatment options.