Expanding Treatment Options for Breast Cancer: ADCs and Oral SERDs

Dr. Monty Pal and Dr. Hope Rugo discuss advances in antibody-drug conjugates for various breast cancer types as well as treatment strategies in the new era of oral SERDs for HR-positive breast cancer. TRANSCRIPT Dr. Monty Pal: Hello, and welcome to the ASCO Daily News Podcast. I'm your host, Dr. Monty Pal. I'm a medical oncologist and vice chair of academic affairs here at the City of Hope Comprehensive Cancer Center, Los Angeles. Today, I'm thrilled to be joined by Dr. Hope Rugo, an internationally renowned breast medical oncologist and my colleague here at City of Hope, where she leads the Women's Cancers Program and serves as division chief of breast medical oncology. Dr. Rugo is going to share with us exciting advances in antibody-drug conjugates (ADCs) that are expanding treatment options in various breast cancer types. She'll also address some of the complex questions arising in the new era of oral SERDs (selective estrogen receptor degraders) that are revolutionizing treatment in the hormone receptor-positive breast cancer space. Our full disclosures are available in the transcript of this episode. Dr. Rugo, welcome, and thanks so much for being on the podcast today. Dr. Hope Rugo: Thank you. Pleasure to be here. Dr. Monty Pal: So, I'm going to switch to first names if you don't mind. The first topic is actually a really exciting one, Hope, and this is antibody-drug conjugates. I don't know if I've ever shared this with you, but I actually started my training at UCLA, I was a med student and resident there, and it was in Dennis Slamon's lab. I worked very closely with Mark Pegram and a handful of others. This is right around the time I think a lot of HER2-directed therapies were really evolving initially in the clinics. Now we've got antibody-drug conjugates. Our audience is well-familiar with the mechanism there but tell us about how ADCs have really started to reshape therapy for HER2-positive breast cancer. Dr. Hope Rugo: Yeah, I mean, this is a really great place to start. I mean, we have had such major advances in breast cancer just this year, I think really changing the paradigm of treating patients. But HER2-positive disease, we've been used to having sequenced success of new agents. And I think the two biggest areas where we've made advances in HER2-positive disease, which were remarkably advanced this year in 2025, have been in antibody-drug conjugates with trastuzumab deruxtecan and with new oral tyrosine kinase inhibitors (TKIs) that have less of a target on EGFR and more on HER2, so they have an overall more tolerable toxicity profile and therefore a potentially better efficacy in the clinic. At least that's what we're seeing with these new strategies that we couldn't really pursue in the past because of toxicities of the oral TKIs. So, although our topic is ADCs, I'm going to include the TKI because it's so important in our thinking about treating HER2-positive disease. In the metastatic setting, we've seen these remarkable improvements in progression-free and overall survival in the second-line setting with T-DXd, or trastuzumab deruxtecan, compared to T-DM1. And then sequencing ADCs with giving T-DXd after T-DM1 was better than an oral tyrosine kinase or a trastuzumab combination with standard chemotherapy. That was DESTINY-Breast03 and DESTINY-Breast02. So, then we've had other trials since then, and T-DXd has moved into the early-stage setting, which I'll talk about in just a moment. But the next big trial for T-DXd in HER2-positive disease was moving it to the first-line setting to supplant what has become an established treatment for now quite a long time: the so-called CLEOPATRA regimen, which used the combined antibodies trastuzumab, pertuzumab with a taxane as first-line therapy. And then we've proceeded on with maintenance with ongoing HP for patients with responding or stable disease. And we'd seen long-term data showing, you know, at 8 years there was a group of patients whose cance