Gaining ground on a cure through synergy: combining checkpoint inhibitors with cancer vaccines

INTRODUCTION

The approval of multiple checkpoint inhibitors (CPIs) for the treatment of advanced malignancies has sparked an explosion of research in the field of cancer immunotherapy. Despite the success of these medications, a large number of patients with advanced malignancy do not benefit from therapy. Early research indicates that a therapeutic combination of cancer vaccines with checkpoint inhibitors may lead to synergistic effects and higher response rates than monotherapy. Areas covered: This paper summarizes the previously completed and ongoing research on this exciting combination, including the use of the tumor lysate, particle-loaded dendritic cell (TLPLDC) vaccine combined with checkpoint inhibitors in advanced melanoma. Expert commentary: Increasing experience with CPIs has led to improved understanding of which patients may benefit and it is increasingly clear that the presence of a pre-existing immune response to the tumor, along with tumor-infiltrating lymphocytes, is key to the success of CPIs. One exciting possibility for the future is the addition of a cancer vaccine to CPI therapy, eliciting these crucial T cells, which can then be augmented and protected by the CPI. A number of current and future studies are addressing this very exciting combination therapy.

Primary analysis of a prospective, randomized, single-blinded phase II trial evaluating the HER2 peptide AE37 vaccine in breast cancer patients to prevent recurrence

BACKGROUND

AE37 is the Ii-Key hybrid of the MHC class II peptide, AE36 (HER2 aa:776-790). Phase I studies showed AE37 administered with granulocyte macrophage colony-stimulating factor (GM-CSF) to be safe and highly immunogenic. A prospective, randomized, multicenter phase II adjuvant trial was conducted to evaluate the vaccine's efficacy.

METHODS

Clinically disease-free node-positive and high-risk node-negative breast cancer patients with tumors expressing any degree of HER2 [immunohistochemistry (IHC) 1-3+] were enrolled. Patients were randomized to AE37 + GM-CSF versus GM-CSF alone. Toxicity was monitored. Clinical recurrences were documented and disease-free survival (DFS) analyzed.

RESULTS

The trial enrolled 298 patients; 153 received AE37 + GM-CSF and 145 received GM-CSF alone. The groups were well matched for clinicopathologic characteristics. Toxicities have been minimal. At the time of the primary analysis, the recurrence rate in the vaccinated group was 12.4% versus 13.8% in the control group [relative risk reduction 12%, HR 0.885, 95% confidence interval (CI) 0.472-1.659, P = 0.70]. The Kaplan-Meier estimated 5-year DFS rate was 80.8% in vaccinated versus 79.5% in control patients. In planned subset analyses of patients with IHC 1+/2+ HER2-expressing tumors, 5-year DFS was 77.2% in vaccinated patients (n = 76) versus 65.7% in control patients (n = 78) (P = 0.21). In patients with triple-negative breast cancer (HER2 IHC 1+/2+ and hormone receptor negative) DFS was 77.7% in vaccinated patients (n = 25) versus 49.0% in control patients (n = 25) (P = 0.12).

CONCLUSION

The overall intention-to-treat analysis demonstrates no benefit to vaccination. However, the results confirm that the vaccine is safe and suggest that vaccination may have clinical benefit in patients with low HER2-expressing tumors, specifically TNBC. Further evaluation in a randomized trial enrolling TNBC patients is warranted.

Primary analysis of the prospective, randomized, phase II trial of GP2+GM-CSF vaccine versus GM-CSF alone administered in the adjuvant setting to high-risk breast cancer patients

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Background: GP2 is a HER2 derived, HLA-A2+-restricted immunogenic peptide designed to stimulate CD8+T cells to recognize tumor cells with any level of HER2 expression (IHC 1-3+). Accrual to a prospective, randomized, multi-center, phase II trial of the GP2 vaccine for prevention of breast cancer recurrence has completed. Here, the planned primary analysis of disease-free survival (DFS) is presented. Methods: HLA-A2+ node positive or high-risk node negative breast cancer patients (pts) with any level of HER2 expression rendered disease-free by standard of care therapy (to include trastuzumab where appropriate) were randomized to receive GP2+GM-CSF (VG) or GM-CSF (CG) alone. Pts received 6 monthly inoculations (primary vaccine series = PVS) followed by 4 boosters administered every 6 months. The Kaplan Meier method was used for statistical analysis. The intention-to-treat (ITT) population is defined as the entire randomly assigned population. The per-treatment (PT) group excluded pts who recurred during the PVS or developed a second malignancy. A pre-specified subgroup analysis was performed based on HER2 expression level. HER2 overexpression (OE) is defined as IHC 3+or FISH >2.2. Results: With 89 VG and 91 CG pts enrolled and vaccinated, there are no differences between groups with respect to age, node positivity, tumor size, grade, ER/PR status, and HER2 expression (p>0.05). The vaccine has been well tolerated with toxicities comparable between the VG and CG. Only one grade 3 local and systemic toxicity reaction has been reported in the VG. At 34 (1-60) month median follow-up, DFS was compared in the ITT (85% VG v 81% CG, p = 0.57) and PT (94% VG v 85% CG, p = 0.17) populations. In OE patients (51 VG and 50 CG) DFS was 94% VG v 89% CG, p = 0.86 (ITT) and 100% VG v 89% CG, p = 0.08 (PT). Conclusions: GP2+GM-CSF is a novel vaccine that is safe and well tolerated. This phase II trial demonstrates potentially greater benefit in pts with HER2 OE tumors, in whom there have been no recurrences in the PT group. This may be due to synergism with trastuzumab therapy, thus justifying a phase III trial evaluating GP2 administered in the adjuvant setting to a HER2 OE population. Clinical trial information: NCT00524277.

Final report of the phase I/II clinical trial of the E75 (nelipepimut-S) vaccine with booster inoculations to prevent disease recurrence in high-risk breast cancer patients

BACKGROUND

E75 (nelipepimut-S) is a human leukocyte antigen (HLA)-A2/A3-restricted immunogenic peptide derived from the HER2 protein. We have conducted phase I/II clinical trials vaccinating breast cancer patients with nelipepimut-S and granulocyte-macrophage colony-stimulating factor (GM-CSF) in the adjuvant setting to prevent disease recurrence. All patients have completed 60 months follow-up, and here, we report the final analyses.

PATIENTS AND METHODS

The studies were conducted as dose escalation/schedule optimization trials enrolling node-positive and high-risk node-negative patients with tumors expressing any degree of HER2 (immunohistochemistry 1-3+). HLA-A2/3+ patients were vaccinated; others were followed prospectively as controls. Local and systemic toxicity was monitored. Clinical recurrences were documented, and disease-free survival (DFS) was analyzed by Kaplan-Meier curves; groups were compared using log-rank tests.

RESULTS

Of 195 enrolled patients, 187 were assessable: 108 (57.8%) in the vaccinated group (VG) and 79 (42.2%) in the control group (CG). The groups were well matched for clinicopathologic characteristics. Toxicities were minimal. Five-year DFS was 89.7% in the VG versus 80.2% in the CG (P = 0.08). Due to trial design, 65% of patients received less than the optimal vaccine dose. Five-year DFS was 94.6% in optimally dosed patients (P = 0.05 versus the CG) and 87.1% in suboptimally dosed patients. A voluntary booster program was initiated, and among the 21 patients that were optimally boosted, there was only one recurrence (DFS = 95.2%).

CONCLUSION

The E75 vaccine is safe and appears to have clinical efficacy. A phase III trial evaluating the optimal dose and including booster inoculations has been initiated.

CLINICAL TRIALS

NCT00841399, NCT00584789.

Abstract P4-13-02: Preliminary results for the phase 1 trial of a dual HER2 peptide cancer vaccine in breast and ovarian cancer patients

BACKGROUND: HER2 is a commonly expressed tumor-associated antigen in breast (BrCa) and ovarian cancer (OvCa) and, therefore, an attractive target for immunotherapy. We have investigated HER2-derived peptides as vaccines mixed with GM-CSF to include GP2 (a HLA-A2 and HLA-A3 restricted, CD8+ eliciting epitope) and AE37 (a HLA unrestricted, MHC class II, CD4+ eliciting epitope). Both peptide vaccines (PV) have shown clinical promise individually. There is clear rationale for combining GP2 and AE37 to elicit a more robust immune response (IR) of both CD4+ and CD8+ T cells. Here, we summarize initial toxicity (tox) and in vivo IR data from a phase 1 trial of the combined PV.

METHODS: The trial is being performed as a five cohort, 3+3 dose-escalation, safety trial. Clinically disease-free, HLA-A2+ and A3+, BrCa and OvCa patients with tumors expressing any level of HER2 (IHC 1-3+) and who have completed standard-of-care therapy are accrued. In the first cohort, three patients received six, monthly intradermal inoculations (R1-R6) of 100mcg of AE37, 100mcg of GP2, and 125mcg of GM-CSF or 100:100:125. The second cohort received 250mcg of AE37, 100mcg of GP2, and 125mcg of GM-CSF or 250:100:125. Three additional cohorts were vaccinated: 250:250:125, 500:250:125, and 500:500:125. Toxicity was graded 48-72 hours post vaccination using NCI Toxicity Criteria v4.0. After each inoculation, local reactions (LR) are measured via the sensitive ballpoint pen method and reported as the orthogonal mean (OM). IR is assessed in vivo by delayed type hypersensitivity (DTH) reactions with separate intradermal inoculations of AE37, AE36, and GP2 antigens, measured both pre-vaccination (R0) and after the vaccine series (R6) via the sensitive ballpoint pen method, and reported as the OM. Means were compared using paired t-tests.

RESULTS: 28 patients enrolled; 8 withdrew consent, 1 recurred prior to completing R6, 3 had an intercurrent illness, 14 patients completed R1-R6, and the vaccine series is ongoing in 2 patients. Six patients did not receive any inoculations and, therefore, are not included in this safety analysis. In 22 patients, the vaccine was well tolerated (max local tox: 23% Grade (Gr) 1, 73% Gr 2, 4% Gr 3; max systemic tox: 14% Gr 0, 50% Gr 1, 36% Gr 2). No dose-limiting toxicity was observed. For the 14 patients who completed the VS, the median age was 51(35-83). Breast tumor size was 3.3±1.1cm and ovarian tumor size was 10.0±2.3cm. Compared to GP2 LR at R1 (15.5±4.1mm), LR increased at R2 (31.7±5.9mm), R3 (42.9±7.4mm), R4 (35.3±7.3mm), R5 (45.0±9.9mm), and R6 (25.9±6.7mm, p = 0.17). Compared to the AE37 LR at R1 (18.5±3.8mm), LR increased at R2 (37.3±6.7mm), R3 (36.4±4.6mm), R4 (42.2±5.9mm), R5 (46.0±8.9mm), and R6 (36.2±6.6mm). Unless stated, all LR p-values < 0.05. After the VS, AE37 DTH increased from 0.0±0.0mm to 19.6±6.7mm (p<0.01), AE36 DTH increased from 0.0±0.0mm to 10.3±3.9mm (p<0.01), and GP2 DTH reactions increased from 0.3±0.2mm to 4.1±2.0mm (p = 0.056).

CONCLUSIONS: Initial results from a phase I trial of a vaccine combining GP2 and AE37 peptides show that dual administration of the peptides is well tolerated at all tested dosing levels. Additionally, the combination is capable of stimulating strong peptide-specific in vivo immune responses. Continued testing of this vaccination strategy is underway.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P4-13-02.

Abstract P4-13-05: HLA-A2 is not a prognostic indicator in breast cancer: Implications for cancer vaccine trials

Introduction

Peptide-based cancer vaccines require presentation by a specific HLA molecule. HLA-A2 is the most common class I allele in the US (40-50% of the population) and, therefore, the most commonly targeted. Our group has been investigating HER2-derived peptide vaccines administered in the adjuvant setting to high risk breast cancer patients in order to prevent disease recurrence. This study was undertaken to compare known prognostic factors and disease-free survival (DFS) in control HLA-A2+ and HLA-A2- patients in order to better define these populations for future trial design.

Methods

Our group is currently enrolling patients in a phase II trial evaluating the HER2-derived peptide vaccines, AE37 (MHC Class II, HLA-non-restricted epitope) and GP2 (MHC Class I, HLA-A2+ restricted epitope). The studies are enrolling high-risk, disease-free breast cancer patients with any level of HER2 expression (IHC 1+, 2+ or 3+) after completion of standard of care therapy. Patients are HLA-typed. HLA-A2+ patients are randomized to GP2+GM-CSF or GM-CSF alone. HLA-A2- patients are randomized to AE37+GM-CSF or GM-CSF alone. Demographics between groups are compared using chi squared or fisher exact as appropriate. DFS is compared using log rank.

Results

Thus far, 407 patients have been enrolled to the study (181 HLA-A2+ and 226 HLA-A2-). Demographics are shown in Table 1.

Table 1. Demographics (all) A2+A2-pn181226 Age (median)51500.47Node Positive62%66%0.46Grade 354%54%0.99Tumor >/ = 2 cm59%64%0.23ER/PR Negative36%38%0.59HER2 Overexpression55%51%0.39Triple Negative13%15%0.52

There are no differences between groups with respect to age, node positivity, grade, tumor size, ER/PR status, HER2 over-expression, or triple negative breast cancer. Of those enrolled, 83 HLA-A2+ patients and 109 HLA-A2- patients have been randomized to the control groups. Within the control group, there are no differences between the HLA-A2+ and HLA-A2- patients regarding age, node positivity, grade, tumor size, ER/PR status, HER2 over-expression, or triple negative breast cancer (Table 2).

With a median follow-up of 30 months, DFS is similar between A2+ and A2- control patients (83% v. 80%, p = 0.93).

Conclusions

Baseline clinico-pathologic factors are similar between HLA-A2+ and HLA-A2- breast cancer patients with no correlations to known prognostic factors. Well-matched blinded control patients treated only with GM-CSF demonstrate no differences in DFS between HLA-A2+ and HLA-A2- patients. Therefore, it does not appear that HLA-A2 status is a prognostic factor in breast cancer, and HLA-A2+ and HLA-A2- patients should be comparable in peptide-based breast cancer vaccine trials.

Table 2. Demographics (Control Group Only) A2+A2-pn83109 Age (median)51510.75Node Positive65%64%0.99Grade 359%57%0.76Tumor >/ =59%71%0.08ER/PR Negative36%38%0.84HER2 Overexpression55%46%0.19Triple Negative11%16%0.34

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P4-13-05.

Abstract P2-14-01: Breast cancer patients with HER2 low-expression: An under-recognized group at significant risk for recurrence

Background:

HER2 over-expression is associated with more aggressive malignant disease. The introduction of trastuzumab and other HER2-directed therapies, however, has led to improved prognosis for patients (pts) with HER2 over-expressing (OE) tumors. Currently, no HER2-targeted therapies are available for patients with HER2 low-expressing (LE) (1+, 2+ by IHC) tumors. We are conducting a randomized, controlled Phase II trial of multiple peptide vaccines enrolling patients with any level of HER2 expression (1+, 2+ and 3+). Here, we report survival data based on levels of HER2 expression in our unvaccinated, control pts.

Methods:

After standard of care therapy, disease-free, high-risk BCa pts were randomized to receive either peptide+GM-CSF (Vaccine Group, VG) or GM-CSF alone (Control Group, CG) in six, monthly doses followed by four boosters every six months. Pts were prospectively followed for recurrence. Demographic information was available for all pts and was compared between groups using chi square or fisher exact tests. Disease-Free Survival (DFS) was compared using log rank.

Results:

To date, we have enrolled 196 pts in the CG. 96 pts had HER2 OE tumors, 100 had LE tumors. The only significant demographic difference between the CG OE and LE groups was more ER/PR positive patients in LE (LE 72% vs OE 51%, p = 0.008). 83% of CG OE pts received trastuzumab, 3% of CG LE pts received trastuzumab. At a median f/u of 30 mo, DFS was significantly higher for CG OE vs CG LE (92.5% v 65.5%, p = 0.001).

Conclusions:

In the cohort of control pts from our ongoing vaccine trial, conducted in an era when Tz has been standard of care therapy for patients with HER2 OE tumors, we have shown that HER2 LE pts are at higher risk of recurrence than OE pts, despite having more ER/PR positive. This calls for increased efforts to develop novel therapies for patients with HER2 LE disease. We have previously shown a trend towards increased DFS with the HER2 vaccines, AE37 (p = 0.13, median f/u 22 mo) and E75 (p = 0.16, median f/u 60mo) in HER2 LE pts, suggesting that these vaccines may represent one such novel therapeutic approach.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P2-14-01.

Risk factors for development of delayed urticarial reactions in the phase II trial of HER2 peptide vaccines plus GM-CSF versus GM-CSF alone in high-risk breast cancer patients to prevent recurrence

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Background: We are monitoring the incidence of delayed urticarial reactions (DURs) in our phase II trial evaluating adjuvant HER2-specific vaccines (AE37 and GP2) for the prevention of breast cancer recurrence. Here, we characterize DURs and analyze risk factors for their development. Methods: After completion of standard of care therapy, disease-free node-positive or high-risk node-negative patients (pts) were randomized to receive either a peptide+GM-CSF (VG) or GM-CSF (CG). Pts receive 6 monthly intradermal inoculations during the primary vaccine series (PVS) then four boosters (B) every 6 mos. Immune response is measured by delayed type hypersensitivity (DTH) pre- (R0) and post-PVS (R6) and local reaction (LR) at R1 – R6. Results: Twenty-four (6.1%) of 393 initiated patients report a DUR; 13 VG (vDUR), and 11 CG (cDUR); vDUR - 9 AE37, 4 GP2. Time to onset of symptoms is 9±5 days (d) and is similar in vDUR/cDUR (p = 0.27). DURs manifest as hives/pruritis in all patients. Average duration of symptoms is 32.6 d ± 8.8 d (no difference in vDUR/cDUR [p = 0.23]). Episodes have resolved with antihistamines or IV/oral steroids. Ten (4 cDUR, 6 vDUR) patients have had recurrent episodes that have resolved similarly. 75% of first episodes occur between R6-B3. For DUR patients v. those who have not had a DUR (noDUR), there are no differences in demographics. DTH response is similar in vDUR pts v. noDUR VG pts (R0- p = 0.34; R6- p=0.40). cDUR pts had a greater DTH response v. CG noDUR pts at R6 (13.2 v 4.7 mm, p=0.01). LRs are greater in DUR pts compared to noDUR pts after the second vaccination (R2 – 66.2 v 48.2 mm, p=0.02). LR for DUR pts decrease and are less than noDUR at R6 (45.4 v 57.4 mm, p=0.09). Relative risk for developing DUR for LR > 100 mm at R2 is 3.49 (1.58-7.68, 95% CI [p=0.004]). At 29.9 months median follow-up, there have been no recurrences in VG and CG DUR v. 75.9% DFS for noDUR (p=0.05). Conclusions: DURs occur infrequently and without long-term sequelae. Pts at risk for developing DUR are identified early in the vaccine series using LR. Robust immune response in DUR may explain the survival benefit demonstrated here. Clinical trial information: NCT00524277.

Time-dependent estimates of recurrence and survival in colon cancer: clinical decision support system tool development for adjuvant therapy and oncological outcome assessment

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Background: Unanswered questions remain regarding treatment efficacy in colon cancer (CC), especially those determining high-risk node-negative cohorts that may benefit from adjuvant therapy. We sought to evaluate the use of machine learning and classification modeling to estimate survival and recurrence in CC. Methods: We used the Department of Defense Automated Central Tumor Registry (ACTUR) to identify primary CC patients treated between January 1993 and December 2004. Cases with events or follow-up that passed quality control were stratified into one-, two-, three-, and five-year survival cohorts. ml-BBNs were trained using machine-learning algorithms and k-fold cross-validation, and receiver operating characteristic (ROC) curve analysis used for validation. Results: There were 5,301 cases stratified into cohorts. Survival cohort Areas-Under-the-Curve (AUCs) ranged from 0.85–0.90, positive-predictive-values (PPVs) for recurrence and mortality ranged from 78-84% and negative-predictive-values (NPVs) from 74-90%. Cross-validation showed that the ml-BBNs produce robust individual estimates of recurrence (p<0.001) and mortality (p<0.001) based on readily available clinical-pathological information in the context of adjuvant chemotherapy. Conclusions: Tumor registry data and machine-learned Bayesian Belief Networks produce robust classifiers. These Clinical Decision Support System tools yield clinically relevant estimates of outcomes that may assist clinicians in treatment planning.

Booster inoculations of the AE37 peptide vaccine enhance immunological responses in a phase II study

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Background: We are conducting a multicenter randomized phase II trial of AE37, the Ii-Key hybrid peptide of HER2 776-790 (AE36). The purpose of the study is to determine if the AE37 vaccine can prevent recurrence in disease-free conventionally treated node-positive (NP) and high-risk node-negative (NN) breast cancer patients at significant risk for recurrence. Since clinical efficacy is anticipated to occur as the result of long lasting memory immune responses induced by vaccination, repeated booster inoculations were scheduled as part of the trial. Here we present data on immune responses in patients who received boosters up to 24 months after completion of the primary vaccination series (PVS). Methods: The trial is enrolling NP or high-risk NN patients with any degree of HER2 expression (IHC 1-3+ or FISH > 1.2) rendered disease-free following standard of care therapy. The vaccine group (VG) received AE37+GM-CSF and control group (CG) GM-CSF alone in 6 monthly i.d. inoculations followed by boosters administered every 6 months x 4. Immunologic responses were assessed in vivo by dermal reactions at the inoculation site, and in vitro, against the AE36 peptide, with proliferation and IFN-γ ELISPOT assays. Results: 25 patients in the VG and 23 in the CG have completed their boosters. After the last booster (BRC24), 100%, 54% and 54% in the VG (vs. 9%, 18% and 27% in the CG) responded by dermal reaction, proliferation and IFN-γ ELISPOT, respectively. Mean dermal reactions (orthogonal mean in mm) in vaccinated patients was 25.9±3.13 at completion of the PVS (R6) and increased to 35.47±4.35 at BRC24 (p=0.01). VG patients increased their proliferation response (stimulation index, SI) to AE36 from 0.97±0.046 at baseline (R0) before vaccination to 2.27±0.57 at R6 (p=0.0003) which was maintained until BRC24 (SI 2.21±0,33, p<0.0001). The number of IFN-γ specific spots/106 PBMC increased from 26.88±12.36 at R0 to 40.35±17.02 (p=0.07) at R6, up to 62±16.82 (p=0.0076) at BRC24. Conclusions: Our data demonstrate that AE37 vaccine boosters enhance the immune responses against HER elicited during the PVS, thus sustaining long lasting immunity, a prerequisite for possible clinical efficacy which is currently being evaluated. Clinical trial information: NCT00524277.

Safety and efficacy of the HER2-derived GP2 peptide vaccine in combination with trastuzumab for breast cancer patients in the adjuvant setting

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Background: GP2 is a 9 amino acid HLA-A2/A3 restricted HER2-derived peptide. GP2 + GM-CSF has been shown to be safe and effective in eliciting anti-HER2 immune response in breast cancer patients. Preclinical data has demonstrated that pretreatment of cells with trastuzumab (Tz) enhances susceptibility to lysis by GP2-specific cytotoxic T lymphocytes (CTLs). We conducted a phase Ib study to evaluate the combination of the GP2 vaccine and Tz. Methods: HLA-A2/A3 + patients with HER2 overexpressing breast cancer receiving Tz as standard therapy were enrolled. The study was designed as a 3+3 dose escalation trial with an expansion cohort evaluating 4 dose levels of the vaccine administered as 6 inoculations given every 3 weeks in combination with Tz (6mg/kg). Toxicity was graded 48-72 hr post vaccination using NCI Toxicity Criteria. Ejection fraction (EF) was monitored every 3 mo. Immunologic response was assessed in vivo by injection site local reaction (LR) and in vitro by quantifying the number of GP2-specific CTLs by HLA-A2: IgG dimer assays and their functional activity by ELISPOT. Results: 19 patients enrolled (median age 47 yr, mean tumor size 3.4 cm, 74% were grade 3, 53% ER/PR+, 63% node positive, 74% received anthracycline based therapy). Maximum local toxicities were grade 1 (77% of patients) and grade 2 (6%), and maximum systemic toxicities were grade 1 (24%) and grade 2 (5%). There were no grade 3 or 4 local or systemic toxicities. There was no significant change in EF at 3 mo (57± 1%, p=0.23) or 6 mo (59±1%, p=0.8) compared to baseline (58±0.9%). Mean post-vaccine series LR was significantly larger than initial vaccination LR (68.2 ± 8.6 mm vs 28.0 ± 10.3 mm, p=0.0004). In vitro assays demonstrated an increase in the maximal number of post- versus pre-vaccination GP2-specific CTLs by dimer assay (1.45 ± 0.19 vs 0.96 ± 0.19%, p=0.06) and increased ELISPOT activity [median 86 range (3-194) vs 34 (range 0-295) spots/106 cells]. Conclusions: GP2 vaccine in combination with Tz is both safe and immunogenic in HER2-overexpressing breast cancer patients in the adjuvant setting. Toxicity was limited to mild local and systemic reactions. There were no dose limiting toxicities or cardiac events.

Randomized phase II clinical trial of the anti-HER2 (GP2) vaccine to prevent recurrence in high-risk breast cancer patients: A planned interim analysis

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Background: A prospective, randomized, multi-center, placebo-controlled, single-blinded, phase II trial was designed to evaluate the safety and clinical efficacy of GP2, a HER2-derived peptide vaccine, in breast cancer patients. Methods: Clinically disease-free, node-positive or high-risk node-negative patients (pts) with any level of HER2 expression were enrolled after standard of care therapy. HLA-A2+ pts were randomized to receive GP2 + GM-CSF (VG) or GM-CSF alone (CG). HLA A2- controls from a parallel arm of the study were also eligible for evaluation, the extended CG (ECG). Pts receive 6 monthly intradermal inoculations (R0-R6) during the primary vaccine series followed by four boosters every 6 mos. Immune responses (IR) were measured by delayed type hypersensitivity (DTH) at R0 and R6. This planned interim analysis was performed at 24 months median follow-up. Results: We have currently enrolled 172 pts (46, VG; 43, CG; 83 extended CG). There are no differences between groups with respect to age, rate of node positivity, tumor grade, tumor size, ER/PR status, and HER2 over-expression (all p > 0.05). Maximum local toxicity (tox) was similar between the two groups (grade (Gr) 1 and 2: VG 93%, CG 98%; Gr 3: VG 2%, CG 1%). Maximum systemic tox was also similar between the groups (Gr 1 and 2: VG 91%, CG 85%). No Gr 3 systemic tox has been reported. The most frequent systemic reactions are fatigue, headache, and myalgias. IR to GP2 has been robust. DTH is increased from R0 to R6 in the VG (3.0±0.98 to 21.5±4.04 mm, p < 0.01) vs. the smaller increase in CG (2.6±0.89 to 6.0±1.6 mm, p = 0.01). VG DTH at R6 is significantly higher than the CG (21.5 vs 6.0 mm, p < 0.01). The recurrence rate (RR) is decreased in the VG vs CG (4.3% vs. 11.6%, p = 0.41) and VG vs ECG (4.3% vs 9.5%, p = 0.41). In pts with HER2-overexpressing (IHC3+ or FISH+) tumors, the RR is decreased in the VG (0% vs 5% CG, p = 0.28). For TNBC (HER2 low, ER/PR-) pts, the RR is reduced in the VG vs ECG (0% vs 10.6%, p = 0.251). Conclusions: The GP2 vaccine is safe and the minimal toxicity is comparable between the VG and CG, suggesting that it is due to GM-CSF. Robust in vivo immune response has correlated with a >50% reduction in breast cancer recurrences in the VG. Clinical trial information: NCT00524277.

Biomarker correlation to clinical response in phase I/II trials of the adjuvant breast cancer vaccine neuvax (nelipepimut-S or E75)

TPS3126

Background: We completed phase I/II clinical trials with NeuVax (nelipepimut-S), a HLA-A2/A3-restricted, HER2-derived peptide vaccine. The vaccine was administered in the adjuvant setting to prevent recurrence in breast cancer patients rendered disease-free with standard-of-care therapy. Here, we examine the relationship between in vitro immunologic response (IR) and clinical recurrence (CR) after 5-year follow-up. Methods: The phase I/II trials were performed as dose-escalation/schedule-optimization trials enrolling node positive and high-risk, node-negative patients (pts) with tumors expressing any level of HER2 (IHC 1+,2+,or 3+). HLA-A2/A3+ pts were enrolled in the vaccine group (VG) while HLA-A2/A3- pts were followed prospectively as an untreated control group (CG). The VG was given 4-6 monthly intradermal inoculations of nelipepimut-S+GMCSF (immunoadjuvant) during the primary vaccine series (PVS). In vitro IR was assessed for E75-specific, cytotoxic T lymphocyte clonal expansion by HLA-A2:IgG dimer assay and expressed as mean dimer index (mdi) at baseline, after PVS (R6), and six months after the PVS. HER2 under-expression was defined as an IHC 1/2, and a FISH < 2.2. VG and CG pts were followed for CR over 60 months. P-values were calculated using the Fisher’s exact test. Results: Of the 195 pts enrolled, 8 withdrew, leaving 187 evaluable pts; 108 in the VG and 79 in the CG. R6 dimer assays were available for 86 pts in the VG. The mean R6 dimer in the VG is 0.63 mdi+.08. Of the 30 pts with an R6 dimer above the mean, only one recurred, compared to eight of the 56 below the mean (p=.09). The difference between baseline and maximum mdi was available in 56 HER2 under-expressing VG pts. Of the 26 pts above the mean difference (1.08 mdi +.17), one recurred, compared to six CR in the 30 pts below the mean (p=.06). There were no CR in pts with HER2 under expression with a mean difference ranked in the top third. Conclusions: In prospective, completed phase I/II trials of NeuVax (nelipepimut-S), patients who exhibit robust in vitro IR have lower recurrence rates. This finding suggests that nelipepimut-specific CTL clonal expansion is a valid biomarker for CR in pts treated with NeuVax. Clinical trial information: NCT00841399.

Abstract P5-16-05: The combination of trastuzumab and HER2-directed peptide vaccines is safe in HER2-expressing breast cancer patients

Background: Cardiotoxicity is the most concerning toxicity associated with the commonly used HER2-directed immunotherapy, trastuzumab (Tz). In general, a significant decline of left ventricular ejection fraction (EF) in asymptomatic patients is accepted as a decrease of at least 10% or an absolute value of below 50%. We are currently conducting multiple trials of HER2-directed peptide vaccines, often given either concurrently or in close temporal proximity to Tz. This has raised the issue that combining therapies could increase the risk of cardio-toxicity. Here, we present safety data from multiple trials in which the combination of these HER2-directed therapies was administered.

Methods: Phase I and II trials were conducted in disease-free breast cancer patients after completion of chemotherapy when indicated. Patients (pts) who were determined by treating oncologists to qualify for Tz received this therapy per standard-of-care. These pts were enrolled onto HER2-directed peptide vaccine trials per each trial's inclusion criteria, with vaccinated (VG) pts receiving peptide + GM-CSF and control (CG) pts receiving GM-CSF alone. All patients were monitored for local and systemic toxicity to peptide inoculations (graded by the NCI's Common Terminology Criteria for Adverse Events). In addition, patients who received Tz had EF tracked through either echocardiogram or MUGA according to local standard of practice. Our database was queried for patients who received Tz and peptide, and had documented measures of EF pre-vaccine (Pre), during vaccine (D) and post-vaccine (Post). These pts were then placed in two groups based on the timing of Tz and vaccine therapy: concurrent(C) group and sequential(S) group. Mean EF at each time point was compared using a t-test.

Results: Overall, the peptide vaccines were well tolerated (max local tox: 1% Grade 0, 65% Gr 1, 33% Gr 2, 1% Gr 3; max systemic tox: 19% Gr 0, 63% Gr 1, 18% Gr 2, 0% Gr 3). These toxicities are likely secondary to the GM-CSF immunoadjuvant as control pts receiving GM-CSF alone have similar toxicity profiles (max local tox: 0% Gr 0, 76% Gr 1, 23% Gr 2, 1% Gr 3; max systemic tox: 20% Gr 0, 65% Gr 1, 15% Gr 2, 0% Gr 3). There have been no serious or non-serious cardiac-related adverse events in our trials. In total, 71 pts treated with Tz and enrolled in a vaccine trial had EF measurements available for analysis; 54 in the S group (35 VG, 19 CG) and 17 in the C group (10 VG, 7 CG). Overall, neither VG nor CG pts had significant changes in EF (VG Pre: 65±0.8%, D: 63±0.9%, Post: 64±0.3%; CG Pre: 63±1.2%, D: 64±1.8%, Post: 63±1.1%). Separating VG pts into C and S pts, there were again no significant changes in EF, (C Pre: 65±1.0%, D: 63±1.0%, Post: 63±1.4%; S Pre: 65±1.7%, D: 61±1.3%, Post: 65±1.8%).

Conclusions: HER2-directed peptide vaccines are safe and well tolerated. Initial data indicate that the combination of Tz and HER2-directed peptide vaccines, whether concurrent or sequential, does not cause significant cardiac toxicities as measured by changes in the EF during and after therapy. We will continue to track this safety data to confirm early findings as we pursue additional combination trials.

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P5-16-05.

Early efficacy analysis of the AE37 vaccine in patients with HER2 low-expressing and triple-negative breast cancer

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Background: Peptide vaccines comprised of HLA class II epitopes, which elicit CD4+ T cell responses, play a critical role in potentiating immune responses. We are conducting a randomized phase II trial of AE37, a hybrid peptide created by the addition of the Ii-Key moiety (LRMK) to the HER2 helper epitope, AE36 (HER2 aa776-790). Here, we present efficacy data focusing on outcomes in patients with low HER2 (IHC 1+ or 2+) expression and triple negative breast cancer (TNBC). Methods: The trial is enrolling node positive or high risk node negative breast cancer patients with any degree of HER2 expression (IHC 1+, 2+ or 3+ or FISH > 1.2) rendered disease-free following standard of care therapy. Patients are randomized to receive either AE37+GM-CSF or GM-CSF alone in 6 monthly intradermal inoculations followed by booster inoculations administered every 6 months. Results: The trial has enrolled 254 patients; 105 in the vaccine group (VG) and 149 in the control group (CG). After a median follow-up of 22.3 months, the disease-free survival (DFS) rate in the VG is 90.3% vs 81.1% in the CG (p=.46), a 49% risk reduction. Evaluating patients with low HER2 expression (IHC 1+ or 2+), there are 53 VG patients and 77 CG patients. The groups are well-matched with respect to the percentage of patients with high grade tumors, tumors > 2cm, the rate of node positivity and ER/PR status (all p>.5). The DFS rate in the VG of low HER2 expressers is 89.8% vs 68.2% in the CG (p=.12), a 68% risk reduction. When limiting analyses to patients with TNBC (ER/PR negative, HER2 1+ or 2+), there are 13 VG patients and 23 CG patients. The groups are again well-matched with the exception of control patients having a larger percentage of tumors > 2 cm (70% vs 31%; p=.02). The DFS rate in the VG of TNBC patients is 83.3% vs 47.6% in the CG (p=.23), a 68% risk reduction. Conclusions: Early analyses suggest clinical benefit to vaccination with AE37, particularly in patients with low HER2-expressing tumors. Importantly, the benefit appears to persist in TNBC patients. Patients will continue to be followed per protocol for 5 years; however, these data suggest that a subsequent phase III trial should evaluate the vaccine in patients with low HER2-expressing disease to include TNBC.

From bench to bedside: The use of the li-Key technology to improve helper peptides for clinical use in cancer vaccines

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Background: Work involving peptide vaccines has shown that peptides containing MHC Class II epitopes, which elicit CD4+ T cell responses, may play a role in potentiating an immune response. The Ii-Key peptide (amino acids 77-80 of the immune-regulatory Ii protein), when covalently linked to an MHC Class II epitope, can induce conformational change in the epitope binding groove, increasing CD4+ T cell stimulation up to 250 fold. Here we present an update of results from clinical trials evaluating this novel technology in an adjuvant breast cancer vaccine targeting HER2/neu. Methods: We reviewed our trials investigating AE37, a hybrid peptide created by the addition of the Ii-Key peptide (LRMK) to AE36 (GVGSPYVSRLLGICL), an MHC Class II-binding peptide from the intracellular domain of the HER2 protein. We have completed a phase I study and are currently conducting a randomized phase II trial of the AE37 peptide + GM-CSF in the adjuvant treatment of disease-free breast cancer patients with any level of HER2 expression (IHC 1-3+ or FISH>1.2). Results: Phase I data showed the vaccine to be safe and effective in raising anti-HER2 immunity. Importantly, even the cohort of patients given AE37 without GM-CSF showed significant increases in both in vivo and in vitro immune responses. To date, we have enrolled 201 patients to our phase II trial (Vaccine (VG)=103, Control (CG)=98). Toxicity has been minimal (99% of local and systemic toxicities grade ≤2). VG patients have shown significant increases in both in vivo and in vitro responses to both AE36 and AE37, with consistently stronger responses to the AE37 hybrid peptide than the native AE36. With a median f/u of 22 months, Kaplan Meier projections estimate recurrence rates of 10.3% in the VG compared to 18% in the CG; a 43% risk reduction. Conclusions: The AE37 peptide vaccine appears to be effective in eliciting a strong immune response and possibly preventing breast cancer recurrence. These results provide an important proof of concept and suggest that additional studies evaluating Ii-Key hybrid peptide vaccines are warranted, whether in the field of immunotherapy or more traditional vaccines.

An assessment of disease features and immune response in breast cancer patients that did not recur after receiving HER2 peptide, AE37 vaccine in a randomized phase II trial

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Background: In a phase I trial of AE37, the Ii-Key hybrid of HER2 derived peptide AE36 (776-790), administered with immunoadjuvant GMCSF demonstrated the vaccine to be safe and capable of stimulating CD4+helper T cells with HER2 specific anti-tumor activity. Here we present analysis of immune markers and patient feature that may impact recurrence from an ongoing prospective, randomized, single-blinded Phase IIb trial of AE37+GMCSF v GMCSF alone in adjuvant high risk breast cancer (BC) patients. Methods: After completion of standard therapy; disease-free, node positive or high risk node negative BC patients (pts) were randomized to receive either AE37+GMCSF or GMCSF in 6 monthly intradermal inoculations. Immunologic responses were measured using [3H]-thymidine incorporation assay (in vitro), delayed-type hypersensitivity (DTH) reactions (in vivo) and T regulatory cells (Tregs). Among those vaccinated recurrent pts (VR) are compared to non recurrent (VNR) pts. Results: We have vaccinated 109 pts with 8.3% recurrence rate at 2 year median follow up. VR v VNR were younger (44 v 50 yo p=0.11), had higher grade (67% v 44% p=0.32), more ER/PR- (44% v 38% p=0.75), larger tumors (89% v 50% p=0.06), and node positive (89% v 70% p=0.37). No difference for HER2 status (IHC 3+, 44% v 49% p=0.64). Both VR and VNR responded to vaccine though the mean DTH and proliferative stimulation index was approximately 10% less in VR pts (18 v 20 p=0.73; 1.96 v 2.2 p=0.77 respectively). The most predictive measure was change in Tregs with VR pts less likely to decrease their Tregs levels (50% v 76% p=0.17) after vacination and more likely experience increased Tregs (17% v 8% p=0.48). A decrease in Tregs had an inverse trend towards recurrence (p=0.17). Conclusions: Preliminarily, it appears most pts immunologically respond to vaccine though slightly less for VR in most assays. The changes of Tregs appear to correlate best with disease recurrence. Whether this reflects an association with disease status or a failure of the vaccine is yet to be seen. These levels may become important in predicting risk for clinical recurrence in future vaccine trials.

Safety and long-term maintenance of anti-HER2 immunity following booster inoculations of the E75 breast cancer vaccine

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Background: We have completed accrual and are in the follow up portion of phase I/II clinical trials evaluating the E75 HER2 peptide vaccine. E75 has been proven safe, capable of stimulating HER2 immunity, and effective in decreasing breast cancer recurrence rates. During the conduct of this trial, it was noted that E75-specific immunity waned after the Primary Vaccine Series (PVS) which corresponded with late recurrences. To maintain long-term immunity, a voluntary booster program was started. Here we present analysis of the booster inoculations. Methods: The trial enrolled node-positive or high-risk, node-negative breast cancer patients (pts) with tumors expressing any level of HER2 (IHC 1-3+). HLA-A2/A3+ pts comprised the vaccine group (VG), HLA-A2/A3- pts were followed as the control group (CG). The VG received 4-6 monthly inoculations of E75+GM-CSF. Volunteer booster program pts (BG) received inoculations every 6 months after the PVS. Pts were monitored for toxicities, in vivo responses by local reactions (LR) and DTH, and in vitro responses measured by enumeration of E75 specific cytotoxic T lymphocytes. Results: 53 pts received at least 1 booster, 34 received 2, 24 three, 20 four, 12 five, and 8 at least 6. 24% of pts had no local toxicity, 73% Grade 1 (G1), 3% G2. 74% had no systemic toxicity, 35% G1, 1% G2. LRs increased significantly from the initial vaccine (R1) during PVS to each booster (B) (R1: 59.5±3.1 v B1: 89.2±3.3, p<0.001; v B2: 95.15±5, p<0.001; v B3: 86.63±5.5, p<0.001; v B4: 83.26±4.6, p=<0.001; v B5: 80.67±6.7, p=0.006; v B6: 78.75±9.4, p=0.04). Dimer values increased from the end of PVS to each post-booster value (pre B1:1.29±0.25 v post B1: 1.46±0.38; post B2: 1.41±0.4; post B3: 1.84±0.35; post B4: 2.23±0.4; post B5:1.94±0.31; post B6: 2.73±0.09, p=0.02). At median 60 months, the recurrence rate for BG was 3.8% vs 18.9% in the CG (p=0.01). Conclusions: Booster inoculations are well-tolerated and appear to assist in the maintenance of long term peptide-specific immunity. Boosted pts have improved recurrence rates. Based on the success of this program, we have incorporated the practice of booster inoculations in our current cancer vaccine trials.