Triple peptide vaccination as consolidation treatment in women affected by ovarian and breast cancer: clinical and immunological data of a phase I/II clinical trial

Vaccination with priming and expansion of tumourreacting T cells is an important therapeutic option to be usedin combination with novel checkpoint inhibitors to increasethe specificity of the T cell infiltrate and the efficacy of thetreatment. In this phase I/II study, 14 high-risk disease-freeovarian (OC) and breast cancer (BC) patients after completionof standard therapies were vaccinated with MUC1, ErbB2and carcinoembryonic antigen (CEA) HLA-A2+-restrictedpeptides and Montanide. Patients were subjected to 6 dosesof vaccine every two weeks and a recall dose after 3 months.ECOG grade 2 toxicity was observed at the injection site. Eightout of 14 patients showed specific CD8+ T cells to at least oneantigen. None of 4 patients vaccinated for compassionate useshowed a CD8 activation. An OC patient who suffered froma lymph nodal recurrence, showed specific anti-ErbB2 CD8+T cells in the bulky aortic lymph nodes suggesting homingof the activated T cells. Results confirm that peptide vaccinationstrategy is feasible, safe and well tolerated. In particularOC patients appear to show a higher response rate comparedto BC patients. Vaccination generates a long-lasting immuneresponse, which is strongly enhanced by recall administrations.The clinical outcome of patients enrolled in the trialappears favourable, having registered no deceased patientswith a minimum follow-up of 8 years. These promising data,in line with the results of similar studies, the high complianceof patients observed and the favourable toxicity profile, supportfuture trials of peptide vaccination in clinically disease-freepatients who have completed standard treatments.