These medications, which are designed to selectively deliver potent cytotoxic drugs to cancer cells expressing specific surface antigens such as human epidermal growth factor receptor 2 (HER2) and trophoblast cell surface antigen 2 (TROP2), can be highly effective but can also come with significant toxicities.
The latest data on several ADCs — their clinical benefit and safety — were the focus of three presentations here at the European Society for Medical Oncology (ESMO) Breast Cancer annual congress.
TROPION-Breast01
In her presentation, Komal Jhaveri, MD, of Memorial Sloan Kettering Cancer Center in New York City, reported additional safety analyses from the phase 3 TROPION-Breast01 trial looking at datopotamab deruxtecan (Dato-DXd) in patients with metastatic hormone receptor–positive (HR+)/HER2− breast cancer resistant to endocrine therapy.
Dato-DXd is an investigational ADC composed of a monoclonal antibody targeting TROP2, a transmembrane glycoprotein overexpressed in cancer cells, linked to the topoisomerase 1 inhibitor deruxtecan as the toxic payload.
As previously reported by this news organization, median progression-free survival was 6.9 months with Dato-DXd compared with 4.9 months for investigator’s choice of chemotherapy (eribulin mesylate, vinorelbine, gemcitabine, or capecitabine), which translated into a 37% (hazard ratio [HR], 0.63; P < .0001) reduction in risk for disease progression.
In addition, the rate of grade 3 or higher treatment-related adverse events with Dato-DXd was less than half that with standard chemotherapy and led to fewer dose interruptions or reductions, indicating that Dato-DXd is better tolerated.
Dr. Jhaveri focused on three treatment-related adverse events of special interest: Stomatitis/oral mucositis, ocular surface events, and adjudicated drug-related interstitial lung disease.
The rate of any grade oral mucositis with Dato-DXd was 56%, she reported. Most were grade 1 (25%) or grade 2 (23%), with only 7% grade 3. About 13% of patients had a dose reduction for oral mucositis, and only one (0.3%) patient discontinued treatment.
The median time to onset was 22 days, and median time to resolution (for events recovered/resolved at data cutoff) was 36 days.
“The study did provide toxicity management guidelines for patients who experienced stomatitis,” Dr. Jhaveri told attendees. The guidelines highly recommended daily use of a steroid-containing mouthwash as prophylaxis or, if that wasn’t available, an inert, bland mouth rinse.
“Prophylactic cryotherapy — ice chips or ice water held in the mouth throughout the infusion — was also suggested,” she said.
The overall rate of ocular surface events with Dato-DXd was 40%, with most grade 1 (32%) or grade 2 (7%), with only 0.8% grade 3. Rates of dose reduction/interruption (3.3%) and discontinuation (0.3%) were low. Most ocular events were either dry eye (22%) or keratitis (14%).
The incidence of ocular events in the chemotherapy group was 12%, higher than typically seen. The study mandated regular ocular assessments, and Jhaveri noted that it was possible that this contributed to the high rate of low-grade ocular events found in both arms.
Median time to onset of ocular events was 65 days, and median time to resolution was 67 days.
Toxicity management guidelines were also incorporated for ocular events, suggesting daily use of artificial tears and avoidance of contact lenses, Dr. Jhaveri said.
In the Dato-DXd group, there were 12 adjudicated cases (3.3%) of drug-related interstitial lung disease; most were grade 1 (1.4%) and grade 2 (1.1%).
“There was one patient who had a grade 5 event, which was characterized by the investigator as grade 3 pneumonitis, with death attributed to disease progression,” Dr. Jhaveri said. This was subsequently adjudicated to be a grade 5 drug-related death.
The median time to onset of interstitial lung disease was 84.5 days, and median time to resolution was 28 days.
Among other treatment-related adverse events of clinical interest, any grade nausea was the most common event with Dato-DXd, reported by 51% of patients, with only 1.4% grade 3 or higher.
“Prophylactic antiemetic agents are highly recommended prior to infusion of Dato-DXd and on subsequent days as needed,” Dr. Jhaveri said.
Any grade diarrhea was reported in 7.5%, with no grade 3+ diarrhea. Alopecia was reported in 36.4%, of which grade 1 was 21% and grade 2 was 15%.
Summing up, the researcher said the new safety data suggest that Dato-DXd offers “better tolerability” than standard chemotherapy. Coupled with the efficacy data, this further supports “Dato-DXd as a potential new therapeutic option for patients with previously treated, inoperable, or metastatic HR+/HER2− breast cancer.”