ADCs for Breast Cancer: Clear Benefits, Manageable Risks

DESTINY-Breast02

New data from the phase 3 DESTINY-Breast02 study confirm a long-term survival benefit, as well as a favorable benefit/risk profile of trastuzumab deruxtecan in patients with HER2+ metastatic breast cancer previously treated with trastuzumab emtansine (T-DM1), reported Sung-Bae Kim, MD, PhD, with University of Ulsan College of Medicine, Seoul, Republic of Korea.

In the phase 3 randomized, multicenter, open-label clinical trial, study participants received either trastuzumab deruxtecan or physician’s choice of trastuzumab plus capecitabine or lapatinib or capecitabine. The primary results of the trial were published last year in The Lancet.

As previously reported by this news organization, after median follow-up of 21.5 months in the trastuzumab deruxtecan group and 18.6 months in the treatment of choice group, median progression-free survival was 17.8 months for trastuzumab deruxtecan vs 6.9 months for the physician’s choice group (HR, 0.36; P < .000001).

The latest data show that after a median follow-up of 30.2 months in the trastuzumab deruxtecan group and 20.5 months in the treatment of choice group, median progression-free survival was 16.7 months with trastuzumab deruxtecan vs 5.5 months with the treatment of choice — a 70% reduction in risk for progression (HR, 0.30), Dr. Kim said.

From time of randomization to progression to next line of therapy or death, median progression-free survival was 33.0 months with trastuzumab deruxtecan vs 15.0 with treatment of choice (HR, 0.42).

Median overall survival was 35.7 months with trastuzumab deruxtecan vs 25.0 months with the treatment of choice, with the risk for death reduced by 31% with trastuzumab deruxtecan (HR, 0.69).

The safety profile of trastuzumab deruxtecan continues to be “manageable, with no long-term toxicity observed with longer follow-up,” Dr. Kim told attendees. The most common treatment-emergent adverse events were nausea (73%), fatigue (62%), and vomiting (38%).

There were a total of 46 (11.4%) adjudicated drug-related interstitial lung disease/pneumonitis cases with trastuzumab deruxtecan. Most were grade 1 or 2. This risk did not increase with longer treatment duration; most events occurred within 12 months of starting treatment, Dr. Kim noted.

With longer follow-up, results of DESTINY-Breast02 “reinforce the substantial benefit” of trastuzumab deruxtecan over the treatment of physician’s choice in patients with HER2+ metastatic breast cancer previously treated with T-DM1, he concluded.

Pooled Data from TROPiCS-02 and EVER-132-002

Hope S. Rugo, MD, of the University of California San Francisco, and colleagues reported a meta-analysis of data from the phase 3 TROPiCS-02 and EVER-132-002 trials of the TROP2-directed ADC sacituzumab govitecan vs the treatment of physician’s choice in HR+/HER2− metastatic breast cancer.

In the pooled analysis, median overall survival was significantly longer with sacituzumab govitecan than with the treatment of physician’s choice in the overall population (16.2 vs 12.7 months) and in patients who received prior CDK4/6 inhibitor treatment (15.4 vs 11.5 months). Progression-free survival also favored sacituzumab govitecan.

These results are consistent with trial-level results from TROPICS-02 and EVER-132-002, reinforcing the efficacy benefits of sacituzumab govitecan over the treatment of physician’s choice, the study team said.

Evolving Landscape of ADCs in Breast Cancer

Giuseppe Curigliano, MD, PhD, with the University of Milan, Italy, who served as discussant for the TROPION-Breast01 safety analysis, noted that the clinical landscape of ADCs has “evolved over time.”

He added that despite having a similar target and similar payload, the anti-TROP2 ADCs in development for HR+/HER2− metastatic breast cancer — Dato-DXd, sacituzumab govitecan, and sacituzumab tirumotecan — appear to have different spectrums of toxicity.

Looking ahead, he said it will be important to determine whether toxicity of these agents can be predicted with a pharmacogenomic analysis and whether toxicity is related to the payload or to the linker antibody complex.

“The science and chemistry of ADCs has shown significant promise in terms of clinical activity, but we also need to better understand safety,” Dr. Curigliano told attendees.

“We need to pay attention to signals in the early phase trials of ADCs and be willing to adjust accordingly to maximize therapeutic benefit and minimize toxicity. Team science will be important in the future developmental ADCs,” he added.

TROPION-Breast01 was sponsored by AstraZeneca. DESTINY-Breast-02 was sponsored by Daiichi Sankyo. TROPiCS-02 and EVER-132-002 were supported by Gilead Sciences. Several trial investigators have disclosed various relationships with these and other pharmaceutical companies.

A version of this article appeared on Medscape.com.