AACR 2020: Combination Immunotherapy for Triple-Negative Breast Cancer
Posted: Tuesday, May 5, 2020
Based on data from the open-label phase II IMPRIME 1 clinical trial presented as part of the 2020 American Association for Cancer Research (AACR) Virtual Annual Meeting (Abstract CT073), the novel innate immune activator Imprime PGG increased the efficacy of the immune checkpoint inhibitor pembrolizumab in patients with metastatic triple-negative breast cancer. The combination treatment was also reported to be well tolerated.
“IMPRIME 1 provides clinical and molecular/cellular proof-of-concept data for the combination of Imprime and [pembrolizumab],” concluded Steven J. O’Day, MD, of the John Wayne Cancer Institute, Santa Monica, California, and colleagues.
The study included 44 patients who received 4 mg/kg of Imprime on days 1, 8, and 15 along with 200 mg of pembrolizumab on day 1 of 3-week cycles. The combination immunotherapy resulted in a median overall survival of 16.4 months, with a 12-month survival rate of 57.6% and an 18-month survival rate of 36.7%. The overall response rate was 15.9%, and the progressive disease rate was 40.9% versus a stable disease rate of 38.6%. The number of complete responses, partial responses, and stable disease instances totaled 54.5%, whereas those instances lasting at least 24 weeks totaled 25.0%. Grade 1 and 2 adverse events were the most common, with just 3 of 44 patients experiencing treatment-related grade 3 or 4 adverse events.
Because Imprime requires the presence of anti–beta glucan antibodies to activate innate immune cells, all patients had anti–beta glucan antibodies IgG of at least 20 mg/mL. Patients who had previously been treated with endocrine therapy experienced a pronounced clinical benefit, with innate immune activation and CD8 T-cell activation occurring within 3 weeks of treatment; this immune activation was associated with improved survival outcomes. Results from paired tumor biopsies revealed infiltration of tumor tissue by activated CD4 and CD8 T cells as well as myeloid cells.
Disclosure: For full disclosures of the study authors, visit abstractsonline.com.
