HLA-associated multipeptide vaccination in biochemically relapsed prostate cancer patients

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Background: We conduct a phase I/II monocenter clinical trial using multi peptide vaccination in patients with hormone naive, biochemically relapsed prostate cancer. The synthetic peptides applied are MHC-class I (HLA-A2) and -class II binders for activating CD4+ and CD8+ T- effector cells in vivo. Study endpoints are side effects as well as PSA- and T-cell response. Methods: Patients (pts) with rising PSA after primary curative surgical treatment without metastatic imageable lesions receive 14 peptides emulsified in Montanide ISA51 subcutaneously, combined with one of four T-cell stimulatory adjuvants versus no adjuvant for 18 months (mo) or until progression. PSA doubling time (DT) and clinical performance are monitored. T-cell activity and specifity are assessed with Elispot assay, tetramer staining and intracellular cytokine stainings. Results: 25 out of 35 pts have terminated the study treatment so far. During the vaccination period, geometric mean PSA DT increased from 7.8 mo (range 1.5 - 44.8 mo, 25 pts) to 11.8 months (range 2.2 - 571.3 mo, 24pts) whereas 1 pt showed a decreasing PSA value. Overall 8/25 pts (32%) had a mean rise of PSA DT of 81.6 mo and four of them did not receive any further treatment and were evaluable for follow-up (FU) after peptide vaccination (FU median 16 mo, range 5–33). These four pts raised their mean geometric PSA DT from 8.2 mo prior study treatment to 51.9 mo at treatment end and 52.5 mo at end of FU. PSA progressed unchanged in 10 patients (40%) or increased intermittently only in 4 pts. Two pts had PSA decline or DT increase during FU but not during the treatment period. Four patients (16%) exhibited an allergic reaction CTCAE II°. All pts reacted to at least one of the tumor antigen-derived HLA-class I epitopes after the fourth vaccine injection and up to six peptides were recognized simultaneously by CD8+ T cells in some individuals. Conclusions: Multi peptide vaccination stabilized or slowed down PSA progress in 11 of 25 cases. Stimulation of specific T-cell response is observed. Rise of PSA DT delaying standard treatment up to 33 mo and thus, delaying disease specific mortality is feasible.

No significant financial relationships to disclose.

Correlation of T-cell response, clinical activity and regulatory T-cell levels in renal cell carcinoma patients treated with IMA901, a novel multi-peptide vaccine

3017

Background: Cancer vaccines have been able to induce T-cell responses in cancer patients but rarely demonstrated a correlation of immune responses with clinical benefit. Here, we present immunological results of a phase 1 study with IMA901, a therapeutic cancer vaccine based on multiple novel synthetic tumor-associated peptides (TUMAP) identified as being naturally presented in primary renal cell carcinoma (RCC) tissues. Methods: The HLA peptidome of 32 primary RCC samples was systematically investigated using a combination of mass spectrometry, gene expression profiling and in vitro human T-cell assays. 9 HLA-A*02- and 1 HLA-DR- restricted TUMAPs derived from 9 different tumor antigens were selected and designated IMA901. 28 HLA-A*02-positive stage III/IV RCC patients were enrolled in a single arm, multicenter study and received 8 vaccinations on days 1, 2, 3, 8, 15, 22, 36, and 64 each consisting of 4.5 mg IMA901 (including a HBV-derived viral marker peptide) and 75 μg GM-CSF as immune adjuvant. T-cell responses using IFN-γ ELISPOT and HLA multimer analysis and CD4+ Foxp3+ regulatory T cell (Treg) levels were measured in peripheral blood. Results: In vivo IMA901- induced specific T-cell responses were detected to the HBV marker peptide (52% of 27 evaluable patients), at least one TUMAP (74%) or multiple TUMAPs (30%). T-cell responses were detectable already at day 15, peaked subsequently and were sustainable until follow-up in the majority of patients. Most importantly, patients eliciting multiple responses to TUMAPs significantly showed a higher clinical benefit rate (SD+PR; p=0.018) and lower Treg levels at study onset (p=0.016). No correlation of HBV marker peptide responses with either clinical benefit or Treg levels was observed. Conclusions: IMA901 rapidly induced T-cell responses in a majority of advanced RCC patients. A clinical mode of action is strongly supported by the significant correlation of multiple T-cell responses with clinical benefit. CD4+ Foxp3+ Tregs seem to play an active role in limiting the broadness of T-cell responses. Furthermore, our data suggest that we can predict in vivo immunogenicity of cancer vaccine antigens by our in vitro drug discovery approach.

No significant financial relationships to disclose.

Identification of RGS5 as a tumor-associated antigen expressed in a broad range of human malignancies and recognized by antigen specific cytotoxic T cells

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Background: Identification of tumor-associated antigens (TAA) have resulted in the development of therapeutic vaccines for the treatment of cancer. We applied an integrated functional genomics approach to identify TAA in malignant tissues of patients with renal cell carcinoma (RCC). Methods: A comparative DNA chip analysis of tumor and the corresponding non-malignant tissue from patients with RCC followed by sequencing of peptides bound to the HLA-class I molecules by mass spectrometry was applied to identify novel TAA in RCC. To confirm the immunogenicity of identified epitopes cytotoxic T lymphocytes (CTL) were generated using dendritic cells (DC). Results: RGS5 was found to be overexpressed in 16 of 29 analyzed RCC (5.7–29.9 fold) as compared to non-malignant renal tissue. Two peptides derived from RGS5 binding to either HLA-A*02 or 03 were identified. RGS5 was previously shown to be expressed in pericytes and promote tumor angiogenesis. Using RT-PCR analysis we found that RGS5 is expressed on a broad variety of tumor cells including RCC, colorectal, breast and ovarian cancer, malignant melanoma and multiple myeloma as well as in acute and chronic leukemias making this protein an interesting candidate for the development of vaccination strategies to target the tumor cells and the tumor vessels. CTL that were induced using the RGS5 peptides lysed autologous DC pulsed with the cognate peptide or transfected with in vitro transcribed RGS5 RNA as well as HLA-matched tumor cell lines. The specificity and HLA restriction was confirmed using blocking monoclonal antibodies and in cold-target inhibition assays. We next utilized DC transfected with RGS5 RNA to generate specific CTL. Using this approach we confirmed the processing and presentation of the identified peptides by malignant cells. These CTL lysed tumor cells in antigen specific manner while sparing non-malignant cells. In an ongoing vaccine trial RGS5 peptides could safely be given to RCC patients resulting in the induction of peptide specific CTL responses. Conclusions: Our results demonstrate that RGS5 is a novel tumor rejection antigen expressed in a wide range of malignancies that can be applied to target malignant cells and tumor angiogenesis.

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SYFPEITHI: database for MHC ligands and peptide motifs

The first version of the major histocompatibility complex (MHC) databank SYFPEITHI: database for MHC ligands and peptide motifs, is now available to the general public. It contains a collection of MHC class I and class II ligands and peptide motifs of humans and other species, such as apes, cattle, chicken, and mouse, for example, and is continuously updated. All motifs currently available are accessible as individual entries. Searches for MHC alleles, MHC motifs, natural ligands, T-cell epitopes, source proteins/organisms and references are possible. Hyperlinks to the EMBL and PubMed databases are included. In addition, ligand predictions are available for a number of MHC allelic products. The database content is restricted to published data only.

Cross-priming of minor histocompatibility antigen-specific cytotoxic T cells upon immunization with the heat shock protein gp96

Vaccination of mice with heat shock proteins isolated from tumor cells induces immunity to subsequent challenge with those tumor cells the heat shock protein was isolated from but not with other tumor cells (Udono, H., and P.K. Srivastava. 1994. J. Immunol. 152:5398-5403). The specificity of this immune response is caused by tumor-derived peptides bound to the heat shock proteins (Udono., H., and P.K. Srivastava. 1993. J. Exp. Med. 178:1391-1396). Our experiments show that a single immunization with the heat shock protein gp96 isolated from beta-galactosidase (beta-gal) expressing P815 cells (of DBA/2 origin) induces cytotoxic T lymphocytes (CTLs) specific for beta-gal, in addition to minor H antigens expressed by these cells. CTLs can be induced in mice that are major histocompatibility complex (MHC) identical to the gp96 donor cells (H-2d) as well as in mice with a different MHC (H-2b). Thus gp96 is able to induce "cross priming" (Matzinger, P., and M.J. Bevan. 1977. Cell. Immunol. 33:92-100), indicating that gp96-associated peptides are not limited to the MHC class I ligands of the gp96 donor cell. Our data confirm the notion that samples of all cellular antigens presentable by MHC class I molecules are represented by peptides associated with gp96 molecules of that cell, even if the fitting MHC molecule is not expressed. In addition, we extend previous reports on the in vivo immunogenicity of peptides associated gp96 molecules to two new groups of antigens, minor H antigens, and proteins expressed in the cytosol.