The investigational anti-body drug conjugate (ADC) datopotamab deruxtecan (Dato-DXd) was associated with both improved progression-free survival and better safety than standard chemotherapy for patients with metastatic HER-2 negative (HR+/HER2–)breast cancer resistant to endocrine therapy, data from the phase 3 TROPION-Breast01 trial showed.
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Sarat Chandarlapaty, MD, PhD, a breast oncologist at Memorial Sloan Kettering Cancer Center in New York, commented that while the trial data showed superior efficacy and safety with Dato-DXd, compared with standard chemotherapy, it's still unclear how it and other ADCs on the market and in the research pipeline may be used in therapy for this patient population.
"Would I rather prescribe Dato-DXd or more chemo after 1 to 2 lines of chemo in unselected HR-positive, HER2-negative breast cancer? The answer is Dato-DXd, but it leaves several unanswered questions for us," he said.
"First, we have two ADCs approved in HR-positive breast cancer: another TROP2 ADC sacituzumab [govitecan] and a HER2 ADC Enhertu (trastuzumab deruxtecan). Would I rather give Dato over one of these? I don't have an answer," he added.
In addition, it's unknown whether these drugs, which have the same topoisomerase-targeted payload, could be given in sequence, and there are as yet no clear answers as to whether patients might do better with Dato-DXd or with a PIK3ca inhibitor.
"I would say that the elephant in the room is really another question, and that is, 'Is Dato-DXd in this context delivering on the promise of an ADC?' " Dr. Chandarlapaty said.
"I think translational research is urgently needed if we're ultimately to deliver on the promise of these agents in the clinic," he concluded.