Ex vivo ras peptide vaccination in patients with advanced pancreatic cancer: Results of a phase I/II study

Abstract

In a pilot phase 1/11 study we have tested synthetic ras peptides used as a cancer vaccine in 5 patients with advanced pancreatic carcinoma. The treatment principle used was based on loading professional antigen-presenting cells (APCs) from peripheral blood with a synthetic ras peptide corresponding to the ras mutation found in tumour tissue from the patient.Peptide loading was performed ex vivo and the next day APCs were re-injected into the patients after washing to remove unbound peptide. Patients were vaccinated in the first and second week and thereafter every 4-6 weeks. In 2 of the 5 patients treated, an immune response against the immunising ras peptide could be induced. None of the patients showed evidence of a T-cell response against any of the ras peptides before vaccination. The treatment was well tolerated and could be repeated multiple times in the same patient. Side effects were not observed even if an immunological response against the ras peptide was evident. We conclude that ras peptide vaccination according to the present protocol is safe and may result in a potentially beneficial immune response even in patients with advanced malignant disease.o 1996 Wiley-Liss, Inc.Pancreatic adenocarcinoma carries a poor prognosis. Most patients are biologically or technically inoperable when diagnosed. For these patients there is no effective radiation or chemotherapy option available, and median survival time is only 3 4 months (Warshaw and Fernandez-del Castillo, 1992). New treatment approaches of advanced pancreatic cancer are urgently needed. Ras genes carrying mutations at specific positions have been identified in up to 90% of pancreatic adenocarcinomas (Alrnoguera et al., 1988). The spectrum of mutations is limited and confined to position 12 of the m s oncogene in pancreatic adenocarcinoma (Capella et al., 1991). The human immune system has the potential to recognise cells expressing such rus mutations (Fossum et al., 1995).We have previously shown that different human lymphocyte antigen (HLA) molecules can bind ras peptides and present them to T cells, thereby initiating an immune response (Fossum et al., 1993;Gedde-Dahl et al., 1994b). T cells from both healthy individuals (Jung and Schluesener, 1991) and cancer patients (Gedde-Dahl et al., 199%;Fossum et al., 1994) specifically recognise mutant p21 ras and corresponding peptides. The effector cells involved in this recognition are T helper (CD4+) and cytotoxic (CD8+) T cells. Both of these T-cell subsets are able to specifically kill or inhibit growth of colon cancer cell lines presenting the corresponding ras mutation (Gedde-Dahl et al., Fossum et al., 1995). Together these findings demonstrate that the T-cell repertoire in both healthy individuals and cancer patients contain T cells capable of recognising the same seh of common mutant ras peptides. The purpose of vaccination is therefore to selectively expand these T cells in cancer patients.These observations formed the basis for the present pilot clinical study, where peptide loaded professi...

Characterisation of immune responses in pancreatic carcinoma patients after mutant p21 ras peptide vaccination

“…This presents the possibility that some T cells may be autoreactive and, therefore, potentially harmful. In our pilot clinical study (Gjertsen et al, 1996) this did not seem to be the case, since no side-effects or possible autoreactivity were observed in the patient having cross-reactive T cells. In a mouse model system, where CD8 + T cells specific for different ras epitopes were induced following immunisation with a ras-vaccinia virus construct, only T cells specific for mutant ras were able to lyse target cells harbouring a ras mutation (Skipper et al, 1993), indicating that endogenous expression of p21 ras by normal cells may only result in subthreshold amounts of ras peptide and is therefore insufficient for T-cell recognition.…”

“…The time span from onset of treatment until detection of responding T cells in peripheral blood was, however, approximately 40 days in both patients (Gjertsen et al, 1996). The responding T cells from donor 2 were characterised by cross-reactivity to all the homologous ras peptides tested encompassing position 12, including the nonmutated ras peptide (Figure 4).…”

“…In a pilot clinical study, we have vaccinated pancreatic carcinoma patients with synthetic ras peptide-pulsed autologous antigen-presenting cells (APCs), and thereby induced peptide specific T-cell responsiveness in vivo (Gjertsen et al, 1995(Gjertsen et al, , 1996. To characterise the specificity further, HLA restriction and functional properties of these in vivo activated T cells, TLCs were generated from one of the vaccinated patients.…”

Intradermal ras peptide vaccination with granulocyte-macrophage colony-stimulating factor as adjuvant: Clinical and immunological responses in patients with pancreatic adenocarcinoma

“…Similar immunotherapeutic strategies have been investigated in patients with advanced adenocarcinoma; thus, 2 phase I studies have demonstrated the feasibility of mutant ras peptide vaccination in patients with advanced cancer. 11,12,27 We demonstrated that vaccination with autologous APCs loaded with the relevant mutant ras peptide could induce peptide-specific T-cell responsiveness in vivo in 2/5 vaccinated pancreatic cancer patients. 11,27 The 2 responding patients showed a transient immune response that was detected only due to frequent monitoring of the T-cell response, indicating that the vaccination protocol was suboptimal.…”

Immunotherapy of the Pancreatic Cancer

“…Gjertsen used an intradermal vaccine of APCs loaded ex vivo with synthetic ras peptide corresponding to the mutation found in patients. In this phase I/II trial , two of five patients with advanced pancreatic cancer showed induced immune response (75) . In further phase I/II trial in 48 pancreatic cancer patients with different clinic stages, ras peptide in combination with GM-CSF could induce peptide-specific immunty in 58% patients.…”