Long-term clinical and immunological effects of p53-SLP® vaccine in ovarian cancer patients

Abstract

Vaccine-induced p53-specific immune responses were previously reported to be associated with improved response to secondary chemotherapy in small cell lung cancer patients. We investigated longterm clinical and immunological effects of the p53-SLP® vaccine in recurrent ovarian cancer patients. Twenty patients were immunized with the p53-SLP® vaccine between July 2006 and August 2007.
Follow-up information on patients was obtained. Clinical responses to secondary chemotherapy after p53-SLP® immunizations was determined by computerized tomography and/or tumour marker levels (CA125). Disease-specific survival was compared with a matched historical control group. Immune responses were analysed by flow cytometry, proliferation assay, IFN-γ ELISPOT and/or cytokine bead array. Lymphocytes cultered from skin biopsy were analysed by flow cytometry and proliferation assay.
Of twenty patients treated with the p53-SLP® vaccine, seventeen were subsequently treated with chemotherapy. Eight of these volunteered another blood sample. No differences in clinical response rates to secondary chemotherapy or disease-specific survival were observed between immunized patients and historical controls (p=0.925, resp. p=0.601). P53-specific proliferative responses were observed in 5/8 patients and IFN-γ production in 2/7 patients. Lymphocytes cultured from a prior injection site showing inflammation during chemotherapy did not recognise p53-SLP®. Thus treatment with the p53- SLP® vaccine does not affect responses to secondary chemotherapy or survival, although p53-specific T-cells do survive chemotherapy.