ADCs in Breast Cancer: Sequencing, Resistance, and Managing Toxicity ASCO Daily News

Drs. Hope Rugo and Sara Tolaney discuss the promise of antibody-drug conjugates (ADCs) in the treatment of breast cancer, highlighting key trials that shed light on matching the right ADC to the right patient in the right setting. They also explore how combinations and sequencing of ADCs can augment their efficacy, the mechanisms of resistance, and the future potential of biomarkers to predict patient response.
TRANSCRIPT
Dr. Hope Rugo: Hello, I'm Dr. Hope Rugo, your guest host of the ASCO Daily News Podcast today. I'm a professor of medicine and director of breast oncology and clinical trials education at the University of California, San Francisco's Comprehensive Cancer Center.
Antibody-drug conjugates, or ADCs, are rapidly changing the treatment landscape for patients with breast cancer. ADCs consist of antibodies that target tumor-specific antigens on the cell surface, chemical linkers, and cytotoxic payloads that can act powerfully to kill cancer cells. On today's episode, we'll be discussing advances in research to match the right ADC to the right patients and in the right setting. We'll also talk about the next steps, assessing how combinations and sequencing of ADCs can augment their efficacy, improve options for patients, and identify biomarkers in the future to predict how patients will respond so that we can match the right treatment to the right patient and their tumor. We need to gain a better understanding of the mechanisms of resistance that occur upfront as well as under the pressure of treatment. 
Joining me for this important discussion is Dr. Sara Tolaney. Dr. Tolaney is an associate professor of medicine at Harvard Medical School, associate director of the Susan Smith Center for Women's Cancer, and chief of the Division of Breast Oncology at the Dana-Farber Cancer Institute in Boston. 
You'll find our full disclosures in the transcript of this episode and disclosures of all guests on the podcast are available at asco.org/DNpod.
Dr. Tolaney, we're delighted to have you on the podcast today. Thanks for being here.
Dr. Sara Tolaney: Thank you so much for having me. I'm looking forward to the discussion.
Dr. Hope Rugo: Great! So, we'll move forward, and because we're friends and colleagues, I'm going to refer to you as Sara, and I'm Hope, since we’ll dispense with formalities in our discussion. 
A lot of the talks that we give about ADCs start out with “a revolution in breast cancer therapy.” And indeed, this is a really exciting time with ADCs as treatment for breast cancer, and we're rapidly moving these agents into earlier disease settings. Can you tell us a little bit about the possibilities and challenges of using ADCs for the treatment of breast cancer today?
Dr. Sara Tolaney: It's interesting that you say antibody-drug conjugates as revolutionizing outcomes of breast cancer, which I think is true. But on the flip side, I think it's also bringing up a lot of questions about how to use them, when to use them, and how to manage side effects. So there are a lot of good strengths for these antibody-drug conjugates, but a lot of unknowns that we're still trying to figure out. We had an older antibody-drug conjugate T-DM1 that we were all very familiar with that for years had been a treatment that we used very commonly in metastatic disease and now even use in early breast cancer, and I think has changed outcomes for patients. But over time, we've been able to develop newer antibody-drug conjugates as the technology has really evolved so that these agents now are able to deliver a lot of chemotherapy into a cancer cell. We're seeing very high drug-to-antibody ratios, and we're also seeing that these drugs can function via bystander effect, whereas T-DM1, for example, was not able to do that. But our newer ADCs, like sacituzumab govitecan or trastuzumab deruxtecan, are agents that do allow chemotherapy to get into that cancer cell, but also to get into neighboring cells. 
And I think