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Oral SERDs Provide New Options in HR-Positive Breast Cancer

— Aditya Bardia, MD, on what the EMERALD data mean for clinical practice

MedpageToday

The motto at the recent Miami Breast Cancer Conference was "hear it on Friday, use it on Monday," as experts contextualized what key data from the latest trial readouts mean for clinical practice.

A plenary session titled "Emerging Data on Oral Selective Estrogen Receptor Degraders [SERDs] and Other Novel Hormonal Therapies" was led by , of Massachusetts General Hospital in Boston. Bardia unpacked the data from the phase III EMERALD trial, which explored the oral SERD elacestrant versus standard of care for hormone receptive (HR)-positive/HER2-negative advanced or metastatic breast cancer.

In this exclusive ڴŮ video, Bardia discusses how the EMERALD trial is likely to stir a rethink of standard approaches to care, especially for patients harboring ESR1 mutations.

Following is a transcript of his remarks:

Hello, I'm Aditya Bardia, a breast medical oncologist at Massachusetts General Hospital. Today I'll be reviewing endocrine therapies with a focus on the latest data, particularly the EMERALD trial, which looked at an oral SERD elacestrant versus standard of care endocrine therapy for hormone receptive-positive metastatic breast cancer.

If you talk about hormone receptor-positive breast cancer, endocrine therapy is the mainstay of management. Currently, endocrine therapy with a CDK4/6 inhibitor is the recommended first-line treatment for hormone receptor-positive breast cancer, but patients eventually have disease progression. As per standard guidelines, sequential endocrine therapy is used before chemotherapy needs to be utilized.

The progression-free survival [PFS]/response rate with standard endocrine therapy like fulvestrant [Faslodex] is low, and clinically there's a need for better endocrine therapy options including oral options for patients with hormone receptor-positive breast cancer, because fulvestrant is given as an intramuscular shot.

So there are a number of oral SERDs in clinical development. And the idea is that there would be a better endocrine agent than fulvestrant and other therapies, and also an oral option. One of them is elacestrant. Elacestrant is a novel, oral SERD, which in phase I/II clinical trials demonstrated clinical activity, including pretreated patients in the metastatic breast cancer setting. So the EMERALD trial was designed to look at elacestrant versus standard of care endocrine therapy in the second-, third-line setting for patients with hormone receptor-positive metastatic breast cancer. It was a global phase III clinical trial.

In terms of the study results, the trial met its primary endpoint. It had a co-primary endpoint looking at progression-free survival in the overall population, as well as patients with ESR1 mutations as a co-primary endpoint. The trial demonstrated that patients who received elacestrant had superior progression-free survival as compared to the endocrine control group, and looking at patients with ESR1 mutations, again patients who received elacestrant had superior progression-free survival as compared to the endocrine monotherapy group.

If you look at the curves, there was an initial decline in the curve suggesting endocrine resistance, and then you could see a separation. So looking at PFS rate at 6 and 12 months is an important metric in this setting. The PFS rate at 12 months with elacestrant was 22.3%, as compared to 9.4% with standard endocrine therapy. Similarly, if you look at patients with ESR1 mutations, the PFS rate was 26.8% as compared to 8.2% with standard endocrine therapy. So overall a hazard ratio of 0.54 in patients with ESR1 mutations -- clear activity of elacestrant as compared to standard endocrine therapy in this group.

And then finally, in terms of side effects, the number one side effect seen with elacestrant was nausea. But other than that, the side effects were very similar. Because this is given as an oral agent there was no pain that can be associated with intramuscular elacestrant.

So the study provides scientific proof of principle that one endocrine agent could be better than standard endocrine therapies that we have available. And there's interest in looking at combination of endocrine therapy plus CDK4/6 inhibitors and other targeted agents in the first-line, and also in the adjuvant setting -- patients with early breast cancer -- looking at oral SERDs versus standard endocrine therapy. In terms of other agents besides elacestrant, amcenestrant is an oral SERD that's been investigated in the first-line setting, as well as early breast cancer. We recently heard a press release related to AMEERA-3 that the second-, third-line study comparing amcenestrant with a standard endocrine therapy was negative, but the drug is being evaluated in the first-line and early breast cancer setting. There's another oral SERD, giredestrant, again being evaluated in the first-line; second-, third-line study; as well as early breast cancer. And there are other drugs as well, such as camizestrant and rintodestrant.

So a number of oral SERDs in clinical development that potentially could provide additional options for our patients with hormone-receptive positive breast cancer. So very excited about development of these novel endocrine agents.

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    Greg Laub is the Senior Director of Video and currently leads the video and podcast production teams.