Vaccination against Oncoproteins of HPV16 for Noninvasive Vulvar/Vaginal Lesions: Lesion Clearance Is Related to the Strength of the T-Cell Response.

PURPOSE: Therapeutic vaccination with human papillomavirus type 16 (HPV16) E6 and E7 synthetic long peptides (SLP) is effective against HPV16-induced high-grade vulvar and vaginal intraepithelial neoplasia (VIN/VaIN). However, clinical nonresponders displayed weak CD8(+) T-cell reactivity. Here, we studied if imiquimod applied at the vaccine site could improve CD8(+) T-cell reactivity, clinical efficacy, and safety of HPV16-SLP (ISA101). EXPERIMENTAL DESIGN: A multicenter open-label, randomized controlled trial was conducted in patients with HPV16(+) high-grade VIN/VaIN. Patients received ISA101 vaccination with or without application of 5% imiquimod at the vaccine site. The primary objective was the induction of a directly ex vivo detectable HPV16-specific CD8(+) T-cell response. The secondary objectives were clinical responses (lesion size, histology, and virology) and their relation with the strength of vaccination-induced immune responses. RESULTS: Forty-three patients were assigned to either ISA101 with imiquimod (n = 21) or ISA101 only (n = 22). Imiquimod did not improve the outcomes of vaccination. However, vaccine-induced clinical responses were observed in 18 of 34 (53%; 95% CI, 35.1-70.2) patients at 3 months and in 15 of 29 (52%; 95% CI, 32.5-70.6) patients, 8 of whom displayed a complete histologic response, at 12 months after the last vaccination. All patients displayed vaccine-induced T-cell responses, which were significantly stronger in patients with complete responses. Importantly, viral clearance occurred in all but one of the patients with complete histologic clearance. CONCLUSIONS: This new study confirms that clinical efficacy of ISA101 vaccination is related to the strength of vaccine-induced HPV16-specific T-cell immunity and is an effective therapy for HPV16-induced high-grade VIN/VaIN. Clin Cancer Res; 22(10); 2342-50. ©2016 AACRSee related commentary by Karaki et al., p. 2317.

Potentiation of a p53-SLP vaccine by cyclophosphamide in ovarian cancer: a single-arm phase II study.

The purpose of the current phase II single-arm clinical trial was to evaluate whether pretreatment with low-dose cyclophosphamide improves immunogenicity of a p53-synthetic long peptide (SLP) vaccine in patients with recurrent ovarian cancer. Patients with ovarian cancer with elevated serum levels of CA-125 after primary treatment were immunized four times with the p53-SLP vaccine. Each immunization was preceded by administration of 300 mg/m2 intravenous cyclophosphamide as a means to affect regulatory T cells (Tregs). Vaccine-induced p53-specific interferon-gamma (IFN-γ)-producing T cells evaluated by IFN-γ ELISPOT were observed in 90% (9/10) and 87.5% (7/8) of evaluable patients after two and four immunizations, respectively. Proliferative p53-specific T cells, observed in 80.0% (8/10) and 62.5% (5/8) of patients, produced both T-helper 1 and T-helper-2 cytokines. Cyclophosphamide induced neither a quantitative reduction of Tregs determined by CD4+ FoxP3+ T cell levels nor a demonstrable qualitative difference in Treg function tested in vitro. Nonetheless, the number of vaccine-induced p53-specific IFN-γ-producing T cells was higher in our study compared to a study in which a similar patient group was treated with p53-SLP monotherapy (p≤0.012). Furthermore, the strong reduction in the number of circulating p53-specific T cells observed previously after four immunizations was currently absent. Stable disease was observed in 20.0% (2/10) of patients, and the remainder of patients (80.0%) showed clinical, biochemical and/or radiographic evidence of progressive disease. The outcome of this phase II trial warrants new studies on the use of low-dose cyclophosphamide to potentiate the immunogenicity of the p53-SLP vaccine or other antitumor vaccines.