Rebecca A. Dent, MD, MSc

Invited discussant Rebecca A. Dent, MD, MSc, Senior Consultant, National Cancer Center Singapore, and Chairman of Medical Oncology at Duke-NUS Medical School, called the findings from these studies “very promising” and “provocative” but acknowledged that the small number of patients precludes drawing definitive conclusions. According to Dr. Dent, however, this research clearly justifies further development of HER3 as a biomarker.

“We all know that HER2 to HER3 is probably the most important messaging that happens, and that relationship is probably more complex than we ever imagined,” Dr. Dent explained. “It’s not simple, but what we have learned is that HER3-DXD [patritumab deruxtecan] induces clinically meaningful decreases in size, looking across all the tumor types.”

“We’ve been trying to convince the [U.S. Food and Drug Administration] for about 30 years that we need to do these separate studies in these different subtypes, but this drug seems to have activity across the different subtypes, and we have antitumor responses across a broad range of HER3 membrane expression,” Dr. Dent added.

Dr. Dent also acknowledged the importance of biomarker analysis in antibody-drug conjugate research, noting the challenge of measuring circulating tumor DNA (ctDNA) in relation to antibody-drug conjugates. According to Dr. Dent, there is a need for guidelines on the clinical use of ctDNA, as the rapid development of liquid biopsies makes it imperative for oncologists to stay updated and informed. 

DISCLOSURE: Dr. Dent reported financial relationships with AstraZeneca, Roche, Eisai, Eli Lilly, MSD, Novartis, and Pfizer.