TAS0313 is a cancer vaccine currently in clinical development in Japan for treatment of solid tumors. The vaccine contains 3 long peptides that target multiple cancer antigens harboring 12 cytotoxic T lymphocyte epitope peptides, which increases patient eligibility for vaccination by targeting multiple HLA types, explained Ryuji Matsumoto, MD (Department of Renal and Genitourinary Surgery, Hokkaido University, Sapporo, Japan). Vaccines containing long peptides are expected to be more effective than previously developed short-peptide vaccines, which did not produce significant responses in clinical studies, Safety, tolerability, and induction of immune responses with TAS0313 was previously confirmed in patients with advanced solid tumors in a phase 1 dose-finding study.
Dr Matsumoto described a multicenter phase 1/2 study to investigate TAS0313 combined with immune checkpoint inhibition (ICI) with pembrolizumab in patients with locally advanced or metastatic urothelial carcinoma.
Patients were enrolled into 2 groups: Cohort 1, ICI-naïve, with prior platinum-based therapy (36 patients, 86% male) and Cohort 2, prior treatment with pembrolizumab (10 patients, 60% male). All patients received 21-day cycles of TAS0313 9 mg subcutaneously on days 1, 8, and 15 of cycles
1 and 2 and day 1 of cycle 3 and later, while pembrolizumab 200 mg was administered intravenously on day 1 of cycle 1 or later, until disease progression or unacceptable toxicity.
In Cohort 1, median follow-up, duration was 6.47 months, and median treatment duration 4.86 months. Overall response (OR) rate was 33.3%, and the disease control rate (DCR) was 66.7%. Median progression-free survival (PFS) was 5 months, Median overall survival (OS) had not yet been reached; OS rate at one year was 74.3%. Complete response and partial response were each achieved by 16.7% of patients, with 33.3% having stable disease. The effect was limited in C2 (median follow-up 6.95 months, and median treatment duration 2.56 months), with stable disease as the best overall response, achieved by 5 patients.
Tumor infiltrating lymphocytes (TIL) and combined positive score (CPS) were identified as potential biomarkers to predict the clinical efficacy of this combination therapy. Therapy was safe and tolerable in these patients, with no increase in adverse drug reactions (ADRs) with addition of TAS0313 to pembrolizumab.
The most common ADRs were injection site reaction and pyrexia. No incidence of Grade ≥3 ADRs over 10% was recorded in Cohort 1 or 2.
Dr. Matsumoto and his colleagues believe that a large-scale randomized study is warranted “to clarify the benefits of TAS0313 combined with ICI in ICI-naïve patients.” TAS0313 is currently in phase 2 of development in Japan.
This study was supported by Taiho Pharmaceutical Co, Ltd.. See original ASCO abstract for disclosures.
Kondo S, Shimizu T, Koyama T, et al. First-in-human study of the cancer peptide vaccine TAS0313 in patients with advanced solid tumors. Cancer Sci. 2021;112(4):1514-1523. DOI: 10.1111/cas.14765.
Matsumoto R, Yonese J, Kawahara T, et al. Phase I/II study to evaluate the efficacy of TAS0313, a cancer peptide vaccine, combined with pembrolizumab for locally advanced or metastatic urothelial carcinoma. J Clin Onco. 2021;39(15):4522-4522. DOI:10.1200/ jco.2021.39.15_suppl.4522