Abstract CT219: Clinical and immunological analysis in a phase II trial of the glypican-3 peptide vaccine for patients with ovarian clear cell carcinoma

Abstract

Abstract Compared with other epithelial ovarian carcinoma subtypes, ovarian clear cell carcinoma (OCCC) is associated with a poorer prognosis and increased chemoresistance. Therefore, new treatment modalities are urgently required for patients with OCCC refractory to chemotherapy. Glypican-3 (GPC3) is useful not only as a novel tumor marker, but also as an oncofetal antigen for immunotherapy. It is specifically overexpressed in hepatocellular carcinoma (HCC). Previous studies demonstrated that GPC3 was also overexpressed in several malignant tumors, including OCCC. We previously reported the safety of and immunological and clinical responses to a GPC3-derived peptide vaccine in a phase I clinical trial of patients with advanced HCC. Although the efficacy of the GPC3-derived peptide vaccine against HCC patients was evaluated, other GPC3-positive cancer patients have not yet been investigated. Therefore, we conducted a phase II trial to evaluate the clinical outcome of OCCC patients treated with a GPC3-derived peptide vaccine (UMIN-CTR: 000003696). In this study, we describe the effect of vaccination with the HLA-A24 or A2-restricted GPC3 peptide on patients with OCCC. The patients were divided into three groups such as adjuvant therapy group, combined therapy group (combined to second-line chemotherapy) and recurrence or advanced group (single of vaccine treatment). The dose of GPC3 peptide injected was 3 mg per body. Patients received the intradermal injection of GPC3 peptide emulsified with incomplete Freund's adjuvant. Vaccinations were carried out biweekly from the first until the 6th and repeated at 6-week intervals after the 7th. Immunological responses were analyzed by ex vivo IFN-γ enzyme-linked immunospot assay (ELISPOT). Seventy OCCC patients were entered into clinical trial until the end of October 2014. In adjuvant group, twenty-nine of thirty-five patients have no recurrence. Recurrence pattern of all 6 patients was peritoneal metastasis. Three of twenty-nine patients with refractory OCCC achieved a significant clinical response. Ex vivo IFN-γ ELISPOT analysis in most OCCC patients revealed vaccine-induced immune reactivity against the GPC3 peptide. Our current data provide preliminary evidence of clinically meaningful benefit for GPC3 peptide vaccines in OCCC and support further evaluation of this approach in these patient populations. Citation Format: Shiro Suzuki, Kiyosumi Shibata, Fumitaka Kikkawa, Tetsuya Nakatsura. Clinical and immunological analysis in a phase II trial of the glypican-3 peptide vaccine for patients with ovarian clear cell carcinoma. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr CT219. doi:10.1158/1538-7445.AM2015-CT219