“This is the first successful study of a breast cancer vaccine to date,” Christian F. Singer, MD, said during an interview. Dr. Singer, the lead author of the new study, presented the results during a poster session at the 2024 annual meeting of the American Society of Clinical Oncology (ASCO).
Previously known as both liposomal BLP25 and Stimuvax, tecemotide is an antigen-specific immunotherapy that targets the cancer therapy–resistant MUC-1 glycoprotein, which is overexpressed in over 90% of breast cancers. Tecemotide also has been shown to moderately improve overall survival rates in non–small cell lung cancer.
“We are not at all surprised by the results of this study in breast cancer,” Gregory T. Wurz, PhD, senior researcher at RCU Labs in Lincoln, California, said in an interview.
Dr. Wurz is coauthor of several studies on peptide vaccines, including a mouse model study of human MUC-1–expressing mammary tumors showing that tecemotide combined with letrozole had additive antitumor activity. Another paper he coauthored showed that ospemifene enhanced the immune response to tecemotide in both tumor-bearing and non–tumor-bearing mice. These findings, combined with other research, led to the creation of a patented method of combining therapies to enhance the efficacy of immunotherapy in the treatment of cancer and infectious diseases. Dr. Wurz was not involved in the new research that Dr. Singer presented at ASCO.
Study Methods and Results
Dr. Singer, head of obstetrics and gynecology at the Medical University of Vienna, Vienna, Austria, and coauthors randomized 400 patients with HER2-negative early breast cancer in a prospective, multicenter, two-arm, phase 2 ABCSG 34 trial to receive preoperative standard of care (SOC) neoadjuvant treatment with or without tecemotide.
Postmenopausal women with luminal A tumors were given 6 months of letrozole as SOC. Postmenopausal patients with triple-negative breast cancer, luminal B tumors, in whom chemotherapy was SOC, as well as all premenopausal study participants, were given four cycles of both epirubicin cyclophosphamide and docetaxel every 3 weeks.
The study’s primary endpoint was the residual cancer burden at the time of surgery.
Long-term outcomes were measured as part of a translational project, while distant relapse-free survival (DRFS) and overall survival (OS) were analyzed with Cox regression models. Long-term outcome data were available for 291 women, of whom 236 had received chemotherapy as SOC.
While tecemotide plus neoadjuvant SOC was not associated with a significant increase in residual cancer burden (RCB) at the time of surgery (36.4% vs 31.5%; P = .42; 40.5% vs 34.8%; P = .37 for the chemotherapy-only cohort), follow-up at 7 years showed 80.8% of patients who had received SOC plus tecemotide were still alive and free from metastasis.
In patients who had received SOC alone, the OS rate at 7 years with no metastasis was 64.7% (hazard ratio [HR] for DRFS, 0.53; 95% CI, 0.34-0.83; P = .005). The OS rate for the study group was 83.0% vs 68.2% in the non-tecemotide cohort (HR for OS, 0.53; 95% CI, 0.33-0.85; P = .008).
The lack of RCB signal at the endpoints, “tells us that pathologic complete response and residual cancer burden simply are not adequate endpoints for cancer vaccination studies and we need to find other predictive/prognostic markers, said Dr. Singer. “We are currently looking into this in exploratory studies.”
The chemotherapy plus tecemotide cohort had a notable outcome with a DRFS of 81.9% vs 65.0% in the SOC group (HR, 0.50; 95% CI, 0.31-0.83; P = .007), and an OS rate of 83.6% vs 67.8% (HR, 0.51; 95% CI, 0.30-0.88; P = .016).
Dr. Singer characterized the HRs as intriguing, saying that they “pave the way for new trials.”
