Two ADCs Offer More Hope for Patients With Advanced TNBC

BERLIN — Patients with previously untreated locally recurrent inoperable or metastatic triple negative breast cancer (TNBC) who are not candidates for immunotherapy may experience improved survival outcomes with TROP2-directed antibody-drug conjugates (ADCs), suggested two trials presented at European Society for Medical Oncology (ESMO) Annual Meeting 2025 on October 19.

ASCENT-03 compared sacituzumab govitecan with standard of care chemotherapy, finding that the drug was associated with a 38% improvement in progression-free survival (PFS) in this patient population that has, traditionally, a poor prognosis. Overall survival data remain immature.

TROPION-Breast02 studied datopotamab deruxtecan (Dato-DXd) against investigator’s choice of chemotherapy. The PFS improvement with the ADC was 43%, while patients also experienced a 21% improvement in overall survival. In both cases, the safety profile of the experimental drugs was deemed to be manageable.

Discussant Ana C. Garrido-Castro, MD, director, Triple-Negative Breast Cancer Research, Dana-Farber Cancer Institute, Boston, who was not involved in either study, said that both sacituzumab govitecan and Dato-DXd showed a PFS benefit. The choice between them, leaving aside overall survival until the data are mature, will be largely based on factors such as the safety profile and the patient preference, she continued.

Sacituzumab govitecan is associated with an increase in neutropenia, nausea, and diarrhea, she pointed out, while Dato-DXd has increased rates of ocular surface toxicity, oral mucositis/stomatitis, and requires monitoring for interstitial lung disease.

Dato-DXd has a higher objective response rate than chemotherapy, unlike sacituzumab govitecan, but, crucially, requires one infusion vs 2 for sacituzumab govitecan per 21-day cycle, and has a shorter total infusion time.

There are nevertheless a number of unanswered questions about the drugs, including how the ADCs affect quality of life, and how common patient adherence to the recommended prophylaxis is. Patients with early relapse of < 12 months remain an “urgent unmet need,” Garrido-Castro said, and the role of immunotherapy rechallenge remains to be explored.

ADCs are also being tested in the neo-adjuvant TNBC setting, and the potential impact of that on the use of the drugs in the metastatic setting is currently unclear. In addition, there are questions around access to therapy.

“Ultimately, it will be very important to have a better understanding of the biomarkers of response and resistance and toxicity to these agents, and whether we should be sequencing antibody drug conjugates,” Garrido-Castro said. “All of this will help shape the next wave of treatment strategies for this patient population.”

She concluded: “Today, marks a paradigm shift of metastatic TNBC, in my opinion. ASCENT-03 and TROPION-Breast02 support TROP2 ADC therapy as the new preferred first-line regimen for this patient population.”

Method and Results of ASCENT-03

ASCENT-03 study presenter Javier C. Cortés, MD, PhD, International Breast Cancer Center, Pangaea Oncology, Quiron Group, Barcelona, Spain, said there is currently an unmet clinical need in the approximately 60% of patients with previously untreated metastatic TNBC who are not candidates for immune checkpoint inhibitors.

Median PFS in previous first-line studies was < 6 months with chemotherapy — the current standard of care — and Cortés said that around half of the patients who receive that in the first-line do not receive second-line therapy because of clinical deterioration or death.

“The sobering truth is that across studies in the US and Europe, approximately 25% to 30% of patients diagnosed with metastatic TNBC are no longer alive at 6 months from their metastatic diagnosis,” said Garrido-Castro. “So if there is a new drug that is able to significantly improve PFS with an acceptable toxicity profile, this should be sufficient to change the current standard of care in the first-line setting.”

As sacituzumab govitecan is already approved for second-line metastatic TNBC and for pretreated hormone receptor positive/HER2- metastatic breast cancer, the ASCENT-03 researchers studied the drug in patients with previously untreated locally advanced inoperable, or metastatic TNBC.

The patients were deemed not to be candidates for PD-L1 inhibitors through having PD-L1-negative tumors, by having PD-L1-positive tumors that had previously been treated with PD-L1 inhibitors in the curative setting, or by having a comorbidity that precluded PD-L1 inhibitor use.

The patients were required to have finished any prior treatment in the curative setting at least 6 months previously. Previously treated, stable central nervous system metastases were allowed.

They were randomized to sacituzumab govitecan or chemotherapy, comprising paclitaxel or nab-paclitaxel, or gemcitabine plus carboplatin, until progression, as verified by blinded independent central review (BICR), or unacceptable toxicity. Patients who progressed on chemotherapy were offered crossover to second-line sacituzumab govitecan.

In all, 558 patients were randomized. The median age was 56 years in the sacituzumab govitecan group vs 54 years in the chemotherapy group. The majority (64% in both groups) of patients were White individuals. The most common metastatic site was the lung (59% vs 61%), and 58% of patients in both groups had previously received a taxane.

Cortés reported that sacituzumab govitecan was associated with a “statistically significant and clinically meaningful” improvement in PFS by BICR, at a median of 9.7 months vs 6.9 months, or a hazard ratio (HR) of 0.62 (P < .0001). This benefit was seen across prespecified subgroups.

The objective response rate was almost identical between the two treatment groups, at 48% with sacituzumab govitecan vs 46% with chemotherapy, although the median duration of response was longer with the ADC, at 12.2 months vs 7.2 months.

Cortés showed the latest results on overall survival. This showed no significant difference between the two treatments, although he underlined that the data are not yet mature.

He also reported that the rates of grade ≥ 3 treatment-emergent adverse events (TEAEs) were similar in the two groups, at 66% with sacituzumab govitecan vs 62% with chemotherapy. However, the rates of TEAEs leading to treatment discontinuation (4% vs 12%) or dose reduction (37% vs 45%) were lower with the ADC.

Cortés concluded that the results suggest that sacituzumab govitecan “is a good option for patients with triple negative breast cancer when they develop metastasis and are unable to receive immune checkpoint inhibitors.”

TROPION-Breast02 Methods and Results

Presenting TROPION-Breast02, Rebecca A. Dent, MD, MSc, National Cancer Center Singapore and Duke-NUS Medical School, Singapore, explained that the trial looked at a patient population similar to that of ASCENT-03, here focusing instead on Dato-DXd.

Patients were included if they had histologically or cytologically documented locally recurrent inoperable or metastatic TNBC, no prior chemotherapy or targeted systemic therapy in this setting, and in whom immunotherapy was not an option.

They were randomized to Dato-DXd or the investigator’s choice of chemotherapy, with treatment continued until investigator-assessed progressive disease on RECIST v1.1, unacceptable toxicity, or another criterion for discontinuation was met.

In total, 642 patients were enrolled. The median age was 56 years for those in the Dato-DXd group and 57 years for those in chemotherapy group, and less than half (41% in the Dato-DXd group and 48% in the chemotherapy group) were White individuals. The number of metastatic sites was less than three in 64% and 67% of patients, respectively.

Dent showed that Dato-DXd was associated with a statistically significant and clinically meaningful improvement in BICR-assessed PFS, at a median of 10.8 months vs 5.6 months with chemotherapy, at a HR of 0.57 (P < .0001). The findings were replicated across the prespecified subgroups.

There was a marked overall survival benefit with Dato-DXd, at a median of 23.7 months vs 18.7 months, at a HR of 0.79 (P = .0291). Dent reported that, at 18 months, 61.2% of patients in the Dato-DXd group were still alive vs 51.3% in the chemotherapy group. Again, the benefit was seen across subgroups.

The confirmed objective response rate with Dato-DXd was far higher than that with chemotherapy, at 62.5% vs 29.3%, or an odds ratio of 4.24. The duration of response was also longer, at 12.3 months vs 7.1 months.

Rates of grade ≥ 3 adverse events were comparable, at 33% with Dato-DXd vs 29% with chemotherapy, although there were more events associated with dose reduction (27% vs 18%) and dose interruption (24% vs 19%) with the ADC.

“These results support Dato-DXd as the first new first-line standard of care for patients with locally recurrent inoperable or metastatic TNBC for whom immunotherapy is not an option,” Dent said.

“What’s important is the patients enrolled into this trial are clearly representative of real world patients that we are treating in our clinics every day. These patients are often excluded from our current clinical trials,” she said.

ASCENT-03 was funded by Gilead Sciences.

TROPION-Breast02 was funded by AstraZeneca.Cortés declared relationships with Roche, AstraZeneca, Seattle Genetics, Daiichi Sankyo, Lilly, Merck Sharpe & Dohme, Leuko, Bioasis, Clovis oncology, Boehringer Ingelheim, Ellipses, HiberCell, BioInvent, GEMoaB, Gilead, Menarini, Zymeworks, Reveal Genomics, Expres2ion Biotechnologies, Jazz Pharmaceuticals, AbbVie, Scorpion Therapeutics, Bridgebio, Biocon, Biontech, Circle Pharma, Delcath Systems, Hexagon Bio, Novartis, Eisai, Pfizer, Stemline Therapeutics, MAJ3 Capital, Leuko, Ariad Pharmaceuticals, Baxalta GmbH/Servier Affaires, Bayer healthcare, Guardant Health, and PIQUR Therapeutics.

Dent declared relationships with AstraZeneca, MSD, Pfizer, Eisai, Novartis, Daiichi Sankyo/AstraZeneca, Roche, and Gilead Sciences.

Garrido-Castro declared relationships with AstraZeneca, MSD, Pfizer, Eisai, Novartis, Daiichi Sankyo/AstraZeneca, Roche, Gilead Sciences, Pfizer, TD Cowen, and Roche/Genentech.

A version of this article first appeared on Medscape.com.