Efficacy of vaccination with recombinant vaccinia and fowlpox vectors expressing NY-ESO-1 antigen in ovarian cancer and melanoma patients

Abstract

Recombinant poxviruses (vaccinia and fowlpox) expressing tumor-associated antigens are currently being evaluated in clinical trials as cancer vaccines to induce tumor-specific immune responses that will improve clinical outcome. To test whether a diversified prime and boost regimen targeting NY-ESO-1 will result in clinical benefit, we conducted two parallel phase II clinical trials of recombinant vaccinia-NY-ESO-1 (rV-NY-ESO-1), followed by booster vaccinations with recombinant fowlpox-NY-ESO-1 (rF-NY-ESO-1) in 25 melanoma and 22 epithelial ovarian cancer (EOC) patients with advanced disease who were at high risk for recurrence/progression. Integrated NY-ESO-1-specific antibody and CD4(+) and CD8(+) T cells were induced in a high proportion of melanoma and EOC patients. In melanoma patients, objective response rate [complete and partial response (CR+PR)] was 14%, mixed response was 5%, and disease stabilization was 52%, amounting to a clinical benefit rate (CBR) of 72% in melanoma patients. The median PFS in the melanoma patients was 9 mo (range, 0-84 mo) and the median OS was 48 mo (range, 3-106 mo). In EOC patients, the median PFS was 21 mo (95% CI, 16-29 mo), and median OS was 48 mo (CI, not estimable). CD8(+) T cells derived from vaccinated patients were shown to lyse NY-ESO-1-expressing tumor targets. These data provide preliminary evidence of clinically meaningful benefit for diversified prime and boost recombinant pox-viral-based vaccines in melanoma and ovarian cancer and support further evaluation of this approach in these patient populations.

Fig. 1.

NY-ESO-1-specific CD8 responses are induced by vaccination from baseline seronegative patients. (A) The frequency of NY-ESO-1-tetramer⁺ (HLA-A2 and B-35) cells at the indicated time points following vaccination in EOC patient no. 4. The number in right upper quadrant indicates percentage of tetramer⁺CD8⁺ cells following in vitro stimulation with cognate NY-ESO-1 peptides. (B) NY-ESO-1-specific (HLA-Cw3) CD8⁺ T-cell analysis in melanoma patient no. 21. (C) Effector function was determined by ELISPOT assays on day 12 after in vitro presensitization with NY-ESO-1 peptides. Numbers of NY-ESO-1-specific IFN-γ spots were shown against peptide-pulsed and -unpulsed autologous dendritic cells.

Fig. 2.

Vaccination enhances NY-ESO-1-specific CD8⁺ T-cell response in baseline seropositive patients. (A) Expansion of HLA-A2/ESOp157-165 tetramer⁺ cells in EOC patient no. 20 by vaccination. (B) Direct ex vivo HLA-Cw3/ESOp96-104 tetramer staining in melanoma patient no. 19. (C) NY-ESO-1-specific CD8⁺ T-cell responses against peptides p91-110, p119-143, and p157-165 were enhanced by vaccination as shown by ELISPOT assay after in vitro presensitization with NY-ESO-1 peptides.

Fig. 3.

Vaccine-induced CD8⁺ T cells are capable of recognizing NY-ESO-1+ tumor targets. (A) Tumor reactivity of CD8⁺ T cells in EOC patient no. 20 was assessed by ICS against HLA-A2⁺ melanoma lines; MZ-MEL-19 (ESO⁺) or SK-MEL-23 (ESO⁻). IFN-γ and CD107 expression were determined by gating on HLA-A2/ESOp157-165 tetramer⁺CD8⁺ cells. (B) Cytotoxicity of vaccine-induced CD8⁺ T-cells against HLA-matched NY-ESO-1⁺ tumor cell lines MZ-MEL-9 (Cw3⁺), NW-MEL-1789 (A2⁺), and SK-MEL-37 (A2⁺). NW-MEL-145 (A2⁺), and NW-MEL-12 (Cw3⁺) were NY-ESO-1-negative and used as control cell lines. CD8 T cells of melanoma patient nos. 17 and 5 were generated by using autologous tumor cell line for prestimulation; CD8 T cells of patient no. 21 were generated by prestimulation with NY-ESO-1 p91-110.

Fig. 4.

The relationship between NY-ESO-1-specific immune responses and clinical outcome in melanoma patients. (A) CD8⁺ T-cell response vs. PFS of melanoma patients. (B) CD8⁺ T-cell response vs. OS of melanoma patients. (C) Baseline seropositive patients with CD8⁺ T-cell reactivity demonstrated a significantly improved TTP (median, 19.5 mo) compared with other groups of patients.