TAS0313 Plus Pembrolizumab in Urothelial Carcinoma

A study evaluated the efficacy of a cancer peptide vaccine plus pembrolizumab for locally advanced or metastatic urothelial carcinoma (UC). The results were presented during the 2021 ASCO Annual Meeting.

“TAS0313 is a cancer vaccine cocktail comprising three long peptides with a total of 12 cytotoxic T lymphocyte epitope peptides,” the researchers explained in their abstract.

The phase I/II study included patients diagnosed with UC with at least one of the following HLA types: HLA-A*02:01, -A*02:06, -A*02:07, -A*11:01, -A*24:02, -A*31:01, or -A*33:03.

Cohort C1 included patients who received platinum-based chemotherapy and were naïve to immune checkpoint inhibitors (ICI), while cohort C2 included patients who progressed while on pembrolizumab. 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 or later, while pembrolizumab (200 mg) was intravenously administered on day 1 of cycle 1 or later until disease progression or unacceptable toxicity.

As of September 10, 2020, 36 patients in C1 and 10 in C2 had received the combination therapy. Median respective follow-up durations were 6.47 months and 6.95 months, and median treatment durations were 4.86 months and 2.56 months.

The overall response (OR) rate in C1 was 33.3%, and disease control rate (DCR) was 66.7%. Median progression-free survival was 5 months, median overall survival (OS) was not yet reached, and one-year OS rate was 74.3%. In C2, the best OR was stable disease, achieved by half of the cohort, for a 50% DCR. Both groups had IgG level increases following treatment.

The researchers said in their conclusion that “a large-scale randomized study is needed to clarify the benefits of TAS0313 combined with ICI in ICI-naïve pts.”