The GP2 peptide: a HER2/neu-based breast cancer vaccine

Preclinical studies suggest that GP2, a HER2/neu-derived peptide, is immunogenic. Subsequent phase I clinical trials demonstrated that GP2-based vaccines are safe and effective in stimulating peptide-specific immunity. A GP2 peptide vaccine is currently being evaluated in a phase II efficacy trial enrolling breast cancer patients. This article reviews initial studies characterizing GP2, clinical trials investigating GP2-based vaccines, and novel immunotherapy strategies incorporating GP2 in combination with other peptides or with the monoclonal antibody trastuzumab.

Clinical trial results of the HER-2/neu (E75) vaccine to prevent breast cancer recurrence in high-risk patients: from US Military Cancer Institute Clinical Trials Group Study I-01 and I-02

BACKGROUND

The authors conducted exploratory phase 1-2 clinical trials vaccinating breast cancer patients with E75, a human leukocyte antigen (HLA) A2/A3-restricted HER-2/neu (HER2) peptide, and granulocyte-macrophage colony-stimulating factor. The vaccine is given as adjuvant therapy to prevent disease recurrence. They previously reported that the vaccine is safe and effective in stimulating expansion of E75-specific cytotoxic T cells. Here, they report 24-month landmark analyses of disease-free survival (DFS).

METHODS

These dose escalation/schedule optimization trials enrolled lymph node-positive and high-risk lymph node-negative patients with HER2 (immunohistochemistry [IHC] 1-3(+) ) expressing tumors. HLA-A2/A3(+) patients were vaccinated; others were followed prospectively as controls for recurrence. DFS was analyzed by Kaplan-Meier curves; groups were compared using log-rank tests.

RESULTS

Of 195 enrolled patients, 182 were evaluable: 106 (58.2%) in the vaccinated group and 76 (41.8%) in the control group. The 24-month landmark analysis DFS was 94.3% in the vaccinated group and 86.8% in the control group (P = .08). Importantly, because of trial design, 65% of patients received a lower than optimal vaccine dose. In subset analyses, patients who benefited most from vaccination (vaccinated group vs control group) had lymph node-positive (DFS, 90.2% vs 79.1%; P = .13), HER2 IHC 1+-2+ (DFS, 94.0% vs 79.4%; P = .04), or grade 1 or 2 (DFS, 98.4% vs 86.0%; P = .01) tumors and were optimally dosed (DFS, 97.3% vs 86.8%; P = .08). A booster program has been initiated; no patients receiving booster inoculations have recurred.

CONCLUSIONS

The E75 vaccine has clinical efficacy that is more prominent in certain patients. A phase 3 trial enrolling lymph node-positive patients with HER2 low-expressing tumors is warranted.

AE37: a novel T-cell-eliciting vaccine for breast cancer

INTRODUCTION

Immunotherapy, including vaccines targeting the human EGFR2 (HER-2/neu) protein, is an active area of investigation in combatting breast cancer. Several vaccines are currently undergoing clinical trials, most of which are CD8(+) T-cell-eliciting vaccines. AE37 is a promising primarily CD4(+) T-cell-eliciting HER-2/neu breast cancer vaccine currently in clinical trials.

AREAS COVERED

This article reviews preclinical investigations as well as findings from completed and ongoing Phase I and Phase II clinical trials of the AE37 vaccine.

EXPERT OPINION

Clinical trials have shown the AE37 vaccine to be safe and capable of generating peptide-specific, durable immune responses. This has been shown in patients with any level of HER-2/neu expression. Early clinical findings suggest there may be benefit to AE37 vaccination in preventing breast cancer recurrence.

Comparison of different HER2/neu vaccines in adjuvant breast cancer trials: implications for dosing of peptide vaccines

We have performed multiple adjuvant clinical trials using immunogenic peptides from the HER2/neu protein (AE37/E75/GP2) plus (GM-CSF) given intradermally to breast cancer patients. Four trials were performed with similar dose-escalation design with increasing doses of peptide (AE37/E75/GP2) and varying amounts of GM-CSF. Dose reductions (DRs) were made for significant local and/or systemic toxicity by decreasing GM-CSF for subsequent inoculations. Ex vivo and in vivo immunologic responses were used to compare groups. Of 132 patients, 39 required DR (30 for robust local reactions [DR-L]). DR patients, particularly DR-L, had greater immune responses both ex vivo and in vivo. Postvaccine delayed-type hypersensitivity in DR-L patients compared with all others was larger for E75 (p = 0.001), AE37 (p = 0.077) and GP2 (p = 0.076). All three peptide vaccines were safe and well-tolerated. These findings have led to a clinically relevant optimal vaccine dosing strategy, which may be applicable to other peptide-based cancer vaccines.

Abstract LB-414: Comparison of in vitro and in vivo immunologic responses in a prospective, randomized, single-blinded phase II trial evaluating the HER-2/neu peptide vaccines GP2 and AE37 in breast cancer patients

BACKGROUND: We are conducting a prospective, randomized, single-blinded phase II trial evaluating the HER-2/neu peptide vaccines AE37 and GP2 in the adjuvant setting to prevent breast cancer recurrence. AE37 is the Ii-Key hybrid of the HER-2/neu peptide AE36 (HER-2/neu aa:776–790) and is capable of stimulating CD4+ helper T-cells with anti-tumor activity. GP2 is an HLA-A2+ -restricted immunogenic peptide from the HER-2/neu protein (HER-2/neu aa: 654–662) which is capable of stimulating CD8+ cytotoxic T-lymphocytes with the ability to recognize and destroy HER-2/neu-expressing tumor cells. Here we present data comparing the immunological profiles between these CD4 and CD8 eliciting vaccines

METHODS: Node positive or high-risk node negative breast cancer patients with any level of HER-2/neu expression rendered disease-free by standard treatments were enrolled. Patients were HLA-typed at enrollment. HLA-A2+ patients were placed in the GP2 arm and randomized to either GP2 + GM-CSF (immunoadjuvant) or GM-CSF alone. HLA-A2− patients were placed in the AE37 arm and randomized to either AE37 + GM-CSF or GM-CSF alone. Vaccinations were given in six monthly intradermal inoculations. In vitro (3H-thymidine proliferation for AE37, HLA-A2:immunoglobulin dimer for GP2) and in vivo (delayed-type hypersensitivity (DTH)) immune responses were measured before (R0), mid-series (R3), upon completion (R6), and at six (RC6) and twelve (RC12) months after completion of the vaccine series.

RESULTS: We have enrolled 247 patients (AE37=171, 87 vaccine and 84 control) (GP2=76, 41 vaccine and 35 control). Proliferative responses to both AE37 and AE36 were increased from baseline in the vaccine group at all time points (AE37: R0=0.98, R3=3.29, R6=3.38, RC6=3.64, RC12=3.68, p<0.001; AE36: R0=0.95, R3=1.92, R6=2.12, RC6=2.18, RC12=1.80, p<0.001) while they did not change for the control group. The population of circulating GP2-specific CD8+ T-cells measured in the dimer assay increased from baseline in the vaccine group at all time points (R0=1.00, R3=1.61, R6=1.85, RC6=1.95, RC12=1.93, p<0.05) with no change in the control group. DTH responses increased in both AE37 and GP2 vaccinated patients from pre- to post-vaccination (AE37: 2.7 vs 30.2 mm, p<0.001; AE36: 2.2 vs 16.3 mm, p<0.001; GP2: 3.5 vs 29.4 mm, p<0.001) while there was no significant change in the control group.

CONCLUSIONS: In a novel prospective, randomized, single-blinded phase II vaccine trial of the AE37 and GP2 peptide vaccines with a GM-CSF only control group, breast cancer patients vaccinated with either a CD4 or CD8 eliciting peptide vaccine exhibit high levels of HER-2/neu-specific in vitro and in vivo immune responses.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr LB-414. doi:10.1158/1538-7445.AM2011-LB-414

Folate receptor α: a storied past and promising future in immunotherapy

Folate receptor alpha (FR α) is a membrane-bound transport protein with several features which make it an attractive target for cancer immunotherapy. FR α is largely shielded from the immune system in normal tissue but exposed while expressed on a variety of malignancies; it is functionally active in cancer pathogenesis; and it is immunogenic. A variety of different immunotherapeutic methods targeting FR α are being explored to treat cancer. Passive immunotherapy includes monoclonal antibodies, antibodies modified to deliver treatments, and modified T cell therapy. Active immunotherapy has focused on using FR α to increase the immunogenicity of cancer or to generate active FR α-directed immunity through a range of vaccination techniques. We will review the rationale behind targeting immunotherapy to FR α and cover the various techniques designed to do this. Folate receptor alpha (FRα) is a unique tumor-associated antigen (TAA) with many characteristics that make it an attractive target for immunotherapy in cancer. Many different immunotherapeutic modalities utilizing FRα are being explored to treat cancer. The research is in various stages: some are just beyond conception, others have been tried and abandoned, and others still are progressing through human clinical trials. This review will cover immunotherapeutic methods, both active and passive, that target FRα.

Use of booster inoculations to sustain the clinical effect of an adjuvant breast cancer vaccine: from US Military Cancer Institute Clinical Trials Group Study I-01 and I-02

BACKGROUND

The authors are conducting clinical trials of the HER-2/neu E75-peptide vaccine in clinically disease-free breast cancer (BC) patients. Their phase 1-2 trials revealed that the E75 + granulocyte-macrophage colony-stimulating factor (GM-CSF) vaccine is safe and effective in stimulating clonal expansion of E75-specific CD8(+) T cells. They assessed the need for and response to a booster after completion of primary vaccination series.

METHODS

BC patients enrolled in the E75 vaccine trials who were ≥6 months from completion of their primary vaccination series were offered boosters with E75 + GM-CSF. Patients were monitored for toxicity. E75-specific CD8(+) T cells were quantified using the human leukocyte antigen-A2:immunoglobulin G dimer before and after boosting.

RESULTS

Fifty-three patients received the vaccine booster. Median time from primary vaccination series was 9 months (range, 6-35 months), and median residual E75-specific immunity was 0.70% (range, 0-3.49%) CD8(+) lymphocytes. Elevated residual immunity (ERI) (CD8(+) E75-specific T cells >0.5%) was seen in 94.4% of patients at 6 months from primary vaccination series versus 48% of patients at >6 months (P = .002). The booster was well tolerated, with only grade 1 and 2 toxicity observed. Local reactions were more robust in patients receiving the booster at 6 months from primary vaccination series compared with those at >6 months (99.4 ± 6.1 mm vs 81.8 ± 4.1 mm, P = .01). In patients lacking ERI, 85% had increased ERI after vaccination (P = .0014).

CONCLUSIONS

The HER-2/neu E75 peptide vaccine E75 stimulates specific immunity in disease-free BC patients. However, immunity wanes with time. A vaccine booster is safe and effective in stimulating E75-specific immunity in those patients without ERI. These results suggest that the booster may be most effective at 6 months after completion of the primary vaccination series.

Use of GM-CSF as an adjuvant with cancer vaccines: beneficial or detrimental?

Granulocyte-macrophage colony-stimulating factor (GM-CSF) has been utilized in the clinical management of multiple disease processes. Most recently, GM-CSF has been incorporated into the treatment of malignancies as a sole therapy, as well as a vaccine adjuvant. While the benefits of GM-CSF in this arena have been promising, recent reports have suggested the potential for GM-CSF to induce immune suppression and, thus, negatively impact outcomes in the management of cancer patients. The purpose of this review is to critically evaluate these reports, while considering the most recent clinical data on immunotherapies. We aim to demonstrate the utility of this adjuvant, elucidate those instances in which GM-CSF may induce immune suppression and identify potential explanations for these recent findings.

Cancer Vaccine Development Program collaborations

Immunotherapy for cancer, which uses the body's immune system to fight the disease, is an increasingly active area of research. Successful therapies such as trastuzamab (Herceptin) for breast cancer and cytokine therapy for renal cell carcinoma and melanoma have validated the field as a viable area of investigation. However, the goal of developing an effective cancer vaccine has not yet been achieved. The military's Cancer Vaccine Development Program (CVDP) is collaborating with other military programs, along with civilian institutions, to advance scientific research surrounding cancer vaccines.

Abstract LB-329: Defining rgulatory T-cells as CD4+CD25hiCD127- or as CD4+CD25hiFoxP3+ in immune monitoring of cancer vaccine clinical trials

Background: Regulatory T cells (Treg) are widely accepted to play a key role in the immune tolerance and escape of cancer cells. Originally Tregs were identified as being CD4+ T cells expressing high levels of CD25 (IL2 receptor). The identification of the transcription factor FoxP3 resulted in defining Tregs as CD4CD25hiFoxP3+ T cells by staining permeablized cells. Recently Tregs have been identified as CD4CD25hi T cells with low levels of CD127 (IL7 receptor) expressing a CD4+CD25hiCD127- cell surface phenotype. In an ongoing clinical trial with a MHC class II HER2/neu pep tide vaccine we have evaluated these various definitions of Treg phenotypes for immunological monitoring.

Methods: Tregs were quantified in disease-free, high risk BCa patients enrolled in adjuvant peptide-based breast cancer vaccine trials. Peripheral blood mononuclear cells (PBMCs) were both permeabilized and stained with CD4, CD25, and FoxP3 monoclonal antibodies and surface stained with CD4, CD25, and CD127. Samples were then analyzed by flow cytometry. The means are compared with t-test and correlation is determined with Pearson's correlation coefficient.

Results: 196 PBMC samples from 72 patients were available for Treg quantification. There was a greater mean percentage of cells identified as Treg in permeabilized than nonpermeabilized cells by staining with CD4+CD25hi (5.9±0.1% vs 4.8 ±0.1%, p<0.01) and excellent correlation between the tests (r=0.78, p<0.01). There was a greater mean percentage of cells identified as Tregs by CD4+CD25hi than CD4+CD25hiFoxP3+ (5.9±0.1% vs 3.6±0.1%, p<0.01) with good correlation (r=0.68, p<0.01). There was a greater mean percentage of Tregs by CD4+CD25+ than CD4+CD25+CD127- (4.8±0.1 vs 4.0±0.1, p<0.01) with excellent correlation (r=0.89, p<0.01). There was a greater mean percentage of Tregs by CD4+CD25hiCD127- than Tregs by CD4+ CD25hiFoxP3+ although levels were similar (4.0±0.1 vs 3.6±0.1, p<0.01) and the two tests had good correlation (r=0.58, p<0.01).

Conclusion: There was good correlation between various methods of defining Tregs with and without cell membrane permeabilization. Defining Treg cells as either CD4+CD25hiFoxP3+ or CD4+CD25+CD127- appear to be more specific than defining Tregs as CD4+CD25hi alone. Furthermore, defining Treg populations by surface staining as CD4+CD25hiCD127- yields similar levels with good correlation as CD4+CD25hiFoxP3+ and may be the preferred method for immune monitoring.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr LB-329.

Results of the first phase 1 clinical trial of the HER-2/neu peptide (GP2) vaccine in disease-free breast cancer patients: United States Military Cancer Institute Clinical Trials Group Study I-04

BACKGROUND

HER-2/neu, overexpressed in breast cancer, is a source of immunogenic peptides that include GP2 and E75. Phase 2 testing of E75 as an adjuvant vaccine has suggested a clinical benefit. GP2, derived from the transmembrane portion of HER-2/neu, has differing binding characteristics and may be more immunogenic than E75. Results of the first phase 1 trial of GP2 peptide vaccine are presented.

METHODS

Disease-free, lymph node-negative, human leukocyte antigen (HLA)-A2(+) breast cancer patients were enrolled. This dose escalation trial included 4 groups to determine safety and optimal GP2 peptide/granulocyte-macrophage colony-stimulating factor (GM-CSF) dose. Toxicities were monitored. Immunologic response was assessed ex vivo via the HLA-A2:immunoglobulin dimer assay to detect GP2-specific CD8(+) T cells (and E75-specific CD8(+) T cells to assess epitope spreading) and in vivo via delayed type hypersensitivity (DTH) reaction (medians/ranges).

RESULTS

Eighteen patients were enrolled. All toxicities were grade < or =2. Eight (88.9%) of 9 patients in the first 3 dose groups required GM-CSF dose reductions for local reactions > or =100 mm or grade > or =2 systemic toxicity. GM-CSF dose was reduced to 125 microg for the final dose group. All patients responded immunologically ex vivo (GP2-specific CD8(+) T cells from prevaccination to maximum, 0.4% [0.0%-2.0%] to 1.1% [0.4%-3.6%], P < .001) and in vivo (GP2 pre- to postvaccination DTH, 0 mm [0.0-19.5 mm] to 27.5 mm [0.0-114.5 mm, P < .001). E75-specific CD8(+) T cells also increased in response to GP2 from prevaccination to maximum (0.8% [0.0%-2.41%] to 1.6% [0.86%-3.72%], P < .001).

CONCLUSIONS

The GP2 peptide vaccine appears safe and well tolerated with minimal local/systemic toxicity. GP2 elicited HER-2/neu-specific immune responses, including epitope spreading, in high-risk, lymph node-negative breast cancer patients. These findings support further investigation of the GP2 vaccine for the prevention of breast cancer recurrence.

Clinical and immunologic responses of HLA-A3+ breast cancer patients vaccinated with the HER2/neu-derived peptide vaccine, E75, in a phase I/II clinical trial

BACKGROUND

We have treated disease-free breast cancer patients with an HER2/neu-derived peptide, E75, as an adjuvant vaccine. E75 was originally described as HLA-A2-restricted and has been previously tested in this population. Based on computer modeling, E75 is predicted to bind to HLA-A3, and preclinical data support this. We conducted a clinical trial of E75 in HLA-A3(+), A2(-) (A3) patients.

STUDY DESIGN

Disease-free breast cancer patients were enrolled after standard therapy in phase I/II trials. A3 patients were enrolled in parallel with A2 patients and vaccinated with E75 and granulocyte-macrophage colony-stimulating factor immunoadjuvant. A2(-), A3(-) patients were followed as controls. Toxicities were graded. Immunologic responses were assessed by delayed-type hypersensitivity reactions and E75-specific interferon-gamma enzyme-linked immunosorbent spot assay. Clinical recurrences were documented.

RESULTS

Thirteen A3 patients completed the vaccine schedule. Clinicopathologic features were similar between A3, A2, and control patients, except for more HER2/neu-overexpressing tumors in the A2 group and more estrogen-receptor/progesterone-receptor-negative tumors in A2 and A3 groups. Toxicity profiles and postvaccination delayed-type hypersensitivity were similar in A3 and A2 patients. Enzyme-linked immunosorbent spot assay results varied, but A3 patients' median spots increased pre- to postvaccination (p = 0.2). Recurrences were lower in the A3 group (7.7%) at 30-month median follow-up compared with published recurrence in A2-vaccinated (8.3%) and control groups (14.8%) at 26-month median follow-up.

CONCLUSIONS

HLA restriction limits potential use of peptide-based cancer vaccines. This trial demonstrates that HLA-A3 patients respond similarly to E75 vaccination as HLA-A2 patients, suggesting the potential use of the E75 vaccine in up to 76% of the population.

The impact of HER2/neu expression level on response to the E75 vaccine: from U.S. Military Cancer Institute Clinical Trials Group Study I-01 and I-02

PURPOSE

HER2/neu, a source of immunogenic peptides, is expressed in >75% of breast cancer patients. We have conducted clinical trials with the HER2/neu E75 peptide vaccine in breast cancer patients with varying levels of HER2/neu expression. Vaccine response based on HER2/neu expression level was analyzed.

EXPERIMENTAL DESIGN

Patients were stratified by HER2/neu expression. Low expressors (n = 100) were defined as HER2/neu immunohistochemistry (IHC) 1(+) to 2(+) or fluorescence in situ hybridization < 2.0. Overexpressors (n = 51) were defined as IHC 3(+) or fluorescence in situ hybridization > or = 2.0. Additional analyses were done stratifying by IHC status (0-3(+)). Standard clinocopathlogic factors, immunologic response (in vivo delayed-type hypersensitivity reactions; ex vivo human leukocyte antigen A2:immunoglobulin G dimer assay), and clinical responses (recurrence; mortality) were assessed.

RESULTS

Low-expressor (control, 44; vaccinated, 56) versus overexpressor patients (control, 22; vaccinated, 29) were assessed. Low expressors, overexpressors, and most IHC-status vaccinated groups responded immunologically. Vaccinated low-expressor patients had larger maximum immunologic responses compared with overexpressor patients (P = 0.04), and vaccinated IHC 1(+) patients had increased long-term immune response (P = 0.08). More importantly, compared with controls, low-expressor patients had a mortality reduction (P = 0.08). The largest decrease in mortality was seen in IHC 1(+) patients (P = 0.05). In addition, a subset of overexpressor patients (n = 7) received trastuzumab before vaccination, and this combination seems safe and immunologically beneficial.

CONCLUSIONS

Most patients with various levels of HER2/neu expression responded immunologically and seemed to benefit from vaccination. The low expressors, specifically IHC 1(+) patients, had more robust immunologic responses and may derive the greatest clinical benefit from the E75 vaccine.

Circulating regulatory (CD4+CD25+FOXP3+) T cells decrease in breast cancer patients after vaccination with an Ii-Key-modified class II HER2/neu peptide (AE37)

Abstract #3134

Background: CD4+CD25+FOXP3+ regulatory T cells (Tregs) have been implicated in the suppression of immune responses against various tumors. To monitor the potential induction of Tregs in breast cancer (BrCa) patients receiving a modified HLA Class II HER2/neu peptide (AE37) vaccine in a clinical trial, we have analyzed peripheral blood lymphocytes (PBL) from vaccinated patients for the presence of Tregs and correlated our findings with ex vivo immune assays and in vivo delayed type hypersensitivity (DTH) responses to the vaccine. Methods: Fifteen BrCa patients have completed 6 monthly injections of the AE37+GM-CSF vaccine in a dose escalation safety study. The AE37 peptide consists of a HER2/neu peptide (776-790) linked to the Ii-Key moiety of the HLA Class II-associated invariant chain, which enhances epitope interaction with the Class II molecule. PBL obtained pre- and post-vaccination were stained with anti-CD4/CD25 (n=15) and FOXP3 (n=9) antibodies (PCH101 and 236A/E7) and analyzed by flow cytometry. Cells were also stimulated ex vivo with AE37 peptide to measure IFN-γ ELISPOT, proliferation (3H-thymidine-cpm) and cytokine secretion (TGF-β). DTH responses to the AE37 peptide pre- and post-vaccination were also recorded. Results: The mean CD4+ and CD4+CD25+ T cell populations for all patients (n=15) did not change from pre- to post-vaccination (CD4+ = 52.3+3.3% vs. 50.5+3.9%, p=0.6; CD4+CD25+ = 1.9+0.2% vs. 2.4+0.5%, p=0.2). Tregs (CD4+CD25+FOXP3+) were reduced in all 9 patients tested pre- to post-vaccination for both FOXP3 antibodies (Ab) (FOXP3 Ab1 = 2.1+0.2% vs. 1.1+0.1%, p=0.002; FOXP3 Ab2 = 2.0+0.2% vs. 1.0+0.2%, p=0.0009). There was no difference in pre- to post-vaccination levels of TGF-β (2720+582 pg/ml vs. 3387+848 pg/ml; p=0.9). AE37-specific proliferative responses increased from pre- to post-vaccination (34+23cpm vs. 6427+1431 cpm; p&lt;0.001). ELISPOT demonstrated an increased response from pre- to long term (6-12mo.) post-vaccination (Median – 2 vs. 34 spots/106 cells; p=0.003). DTH responses increased in all patients from pre- to post-vaccination (3.6+1.4 mm vs. 56.0+9.4 mm; p&lt;0.0001), and there appeared to be an inverse relationship between the degree of Treg reduction and the size of DTH response to AE37 (R2=0.83).&#x2028; Discussion: The novel AE37 HER2/neu peptide vaccine does not result in increased levels of Tregs. Furthermore, the reduced levels of Tregs in vaccinated patients appear to be associated with more robust responses in ex vivo immune assays and in vivo DTH reactions suggesting that the AE37 vaccine may be clinically useful.

Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 3134.

Optimal method of dosing HER2/neu peptide vaccines: U.S. Military Cancer Institute Clinical Trials Group Study 1-01, 1-02, 1-03, and 1-04

Abstract #3139

Background: Our Cancer Vaccine Development Program has performed phase I and II clinical trials using immunogenic peptides from the HER2/neu protein. AE37 (aa:776-790+Ii-Key) is HLA promiscuous whereas E75 (aa:369-377) and GP2 (aa:654-662) are HLA-A2/A3+ restricted. The peptides are located on the intracellular, extracellular, and transmembrane portions of the HER2/neu protein. We evaluate patients who required dose reductions and compare them to those who did not in our three peptide vaccine trials to determine the immunologic and clinical relevance of different responses to the peptide vaccines. Methods: Three vaccine trials were performed separately with similar dose escalation design by varying the amount of AE37, GP2 or E75 peptide and GM-CSF adjuvant. Dose reductions (DR) were made in event of significant toxicity (&gt;100mm local or ≥grade 2 systemic) by decreasing GM-CSF (or peptide if no GM-CSF) by 50% for subsequent inoculations. We compared patients necessitating DR and those who did not. Immune response was measured ex vivo via 3H-thymidine proliferative assays or HLA-A2:Ig dimer assays and in vivo via DTH reactions pre- and post-vaccine. Recurrence and mortality data were available for E75 treated patients at 30-month median follow-up. Results: 132 patients underwent peptide vaccination and 39 patients required DR (Table 1).&#x2028; &#x2028; No patient had grade 3-5 local or systemic toxicities. DR patients, particularly those reduced for robust local reactions (DR-L), had greater immune responses ex vivo and in vivo. The post-vaccine DTH in DR-L patients compared to all other vaccinated patients was significantly larger in E75 (24.5±4.1mm vs. 12.7±1.3mm; p=0.001) and trended towards significant in AE37 (69.4±10.3mm vs. 35.8±14.9mm; p=0.08) and GP2 (48.9±14.1mm vs. 24.1±3.3mm; p=0.08). No recurrences or deaths were noted in the E75 DR patients; but for patients not requiring dose reductions there were 10 (12.5%) recurrences and 1 (1.25%) death.Discussion: All three peptide vaccines are safe and well-tolerated with minimal toxicity. The safety was partly due to reducing GM-CSF (or peptide if no GM-CSF) by 50% for patients with &gt;100mm local reactions or &gt;grade 2 systemic toxicity. DR patients, particularly DR-L patients, immunological responses were larger. This increased immune response (noted by DTH) suggests improved clinical response as there have been no recurrences or deaths among DR patients. Our analysis indicates that the optimal method of dosing HER2/neu peptide vaccines consists of constant peptide dose with a large enough dose of adjuvant to generate robust local reactions and that when local reactions are &gt;100mm performing DR of adjuvant by 50% for subsequent inoculations.

Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 3139.

Assessment of immunologic response and recurrence patterns among patients with clinical recurrence after vaccination with a preventive HER2/neu peptide vaccine: from US Military Cancer Institute Clinical Trials Group Study I-01 and I-02

BACKGROUND

E75, a HER2/neu immunogenic peptide, is expressed in breast cancer (BCa). We have performed clinical trials of E75 + GM-CSF vaccine in disease-free, node-positive and node-negative BCa patients at high recurrence risk and recurrences were noted in both control and vaccine groups.

METHODS

Among the 186 BCa patients enrolled, 177 completed the study. Patients were HLA typed; the HLA-A2(+)/A3(+) patients were vaccinated; HLA-A2(-)/A3(-) patients were followed as controls. Standard clinicopathological factors, immunologic response to the vaccine, and recurrences were collected and assessed.

RESULTS

The control group recurrence rate was 14.8 and 8.3% in the vaccinated group (P = 0.17). Comparing the 8 vaccinated recurrences (V-R) to the 88 vaccinated nonrecurrent patients (V-NR), the V-R group had higher nodal stage (> or = N2: 75 vs. 5%, P = 0.0001) and higher grade tumors (%grade 3: 88 vs. 31%, P = 0.003). The V-R group did not fail to respond immunologically as noted by equivalent dimer responses and post-DTH responses. Compared to control recurrent patients (C-R), V-R patients trended toward higher-grade tumors and hormone-receptor negativity. C-R patients had 50% bone-only recurrences, compared to V-R patients with no bone-only recurrences (P = 0.05). Lastly, V-R mortality rate was 12.5% compared with 41.7% for the C-R group (P = 0.3).

CONCLUSIONS

The vaccinated patients who recurred had more aggressive disease compared to V-NR patients. V-R patients had no difference in immune response to the vaccine either in vitro or in vivo. V-R patients, when compared to C-R patients, trended towards more aggressive disease, decreased recurrence rates, decreased mortality, and no bone-only recurrences.

The E75 HER2/neu peptide vaccine

E75 (HER2/neu 369-377) is an immunogenic peptide from the HER2/neu protein which is overexpressed in many breast cancer patients. A large amount of preclinical work and a small number of Phase I trials have been completed evaluating the vaccine potential of the E75 peptide mixed with an immunoadjuvant. Our group has performed two concurrent E75 + GM-CSF Phase II trials in node-positive and node-negative disease-free breast cancer patients. These trials, totaling 186 patients, were designed to assess the ability of the E75 vaccine to prevent disease recurrence in these high risk patients. In this review article, we discuss the safety of the vaccine, the immunologic response to the peptide, and most importantly, the potential clinical benefit of the vaccine. The recurrence rate, mortality associated with recurrence, and the distribution of recurrences are presented and discussed. Additionally, the lessons learned from these trials to include optimal dosing and the need for booster inoculations are addressed. We also present data exploring possible explanations and mechanisms behind the potential clinical utility of this simple single epitope vaccine. Finally, we present some of the future directions for our Cancer Vaccine Development Program assessing multi-epitope peptide vaccines and combination immunotherapies.

Monitoring circulating tumor cells in cancer vaccine trials

The presence of circulating tumor cells (CTC) from various cancers has provided a wealth of information and possibilities. As the role of CTC detection in the treatment assessment of metastatic breast cancer becomes standard, there is interest in applying this tool in cancer vaccine development and clinical trial monitoring. Since we lack a proven immunologic assay that correlates with clinical response, CTC detection, quantification and phenotypic characterization may be a useful surrogate for clinical outcome. The Cancer Vaccine Development Program is involved in the development of HER2/neu peptide based vaccine development for the prevention of recurrence in HER2/neu expressing cancers like breast cancer. The CellSearch System (Veridex, LLC Warren, NJ) has been used by our lab in conjunction with in vivo and/or in vitro immunologic measurements to define a monitoring tool that could predict clinical response. Once validated, this assay could significantly shorten clinical trials and lead to more efficient assessment of potentially promising cancer vaccines.

Results of the first phase I clinical trial of the novel II-key hybrid preventive HER-2/neu peptide (AE37) vaccine

PURPOSE

HER-2/neu is overexpressed in breast cancer and is the source of immunogenic peptides. CD4(+) T-helper peptides for HER-2/neu are being evaluated in vaccine trials. The addition of Ii-Key, a four-amino-acid LRMK modification, increases vaccine potency when compared with unmodified class II epitopes. We present the results of the first human phase I trial of the Ii-Key hybrid HER-2/neu peptide (AE37) vaccine in disease-free, node-negative breast cancer patients.

PATIENTS AND METHODS

The dose escalation trial included five dose groups, to determine safety and optimal dose of the hybrid peptide (100 microg, 500 microg, 1,000 microg) and granulocyte-macrophage colony-stimulating factor (GM-CSF; range, 0 to 250 microg). In the event of significant local toxicity, GM-CSF (or peptide in absence of GM-CSF) was reduced by 50%. Immunologic response was monitored by delayed-type hypersensitivity and [(3)H]thymidine proliferative assays for both the hybrid AE37 (LRMK-positive HER-2/neu:776-790) and AE36 (unmodified HER-2/neu:776-790).

RESULTS

All 15 patients completed the trial with no grade 3 to 5 toxicities. Dose reductions occurred in 47% of patients. In the second group (peptide, 500 microg; GM-CSF, 250 microg), all patients required dose reductions, prompting peptide-only inoculations in the third group. The vaccine induced dose-dependent immunologic responses in vitro and in vivo to AE37, as well as AE36.

CONCLUSION

The hybrid AE37 vaccine seems safe and well tolerated with minimal toxicity if properly dosed. AE37 is capable of eliciting HER-2/neu-specific immune responses, even without the use of an adjuvant. This trial represents the first human experience with the Ii-Key modification, and to our knowledge, AE37 is the first peptide vaccine to show potency in the absence of an immunoadjuvant.

Combined clinical trial results of a HER2/neu (E75) vaccine for the prevention of recurrence in high-risk breast cancer patients: U.S. Military Cancer Institute Clinical Trials Group Study I-01 and I-02

PURPOSE

E75 is an immunogenic peptide from the HER2/neu protein, which is overexpressed in many breast cancer patients. We have conducted two overlapping E75 vaccine trials to prevent recurrence in node-positive (NP) and node-negative (NN) breast cancer patients.

EXPERIMENTAL DESIGN

E75 (HER2/neu 369-377) + granulocyte macrophage colony-stimulating factor was given intradermally to previously treated, disease-free NP breast cancer patients in a dose escalation safety trial and to NN breast cancer patients in a dose optimization study. Local and systemic toxicity was monitored. Immunologic responses were assessed using in vitro assays and in vivo delayed-type hypersensitivity responses. Clinical recurrences were documented.

RESULTS

One hundred and eighty-six patients were enrolled in the two studies (NP, 95; NN, 91). Human leucocyte antigen A2 (HLA-A2) and HLA-A3 patients were vaccinated (n = 101), whereas all others (n = 85) were followed prospectively as controls. Toxicities were minimal, and a dose-dependent immunologic response to the vaccine was shown. Planned primary analysis revealed a recurrence rate of 5.6% in vaccinated patients compared with 14.2% in the controls (P = 0.04) at a median of 20 months follow-up. As vaccine-specific immunity waned over time, the difference in recurrence lost significance at 26 months median follow-up (8.3% versus 14.8%); however, a significant difference in the pattern of recurrence persisted.

CONCLUSIONS

E75 is safe and effective in raising a dose-dependent HER2/neu immunity in HLA-A2 and HLA-A3 NP and NN breast cancer patients. More importantly, E75 may reduce recurrences in disease-free, conventionally treated, high-risk breast cancer patients. These findings warrant a prospective, randomized phase III trial of the E75 vaccine with periodic booster to prevent breast cancer recurrences.