Translational Advances in Cancer Prevention Agent Development (TACPAD) Virtual Workshop on Immunomodulatory Agents: Report

The National Cancer Institute (NCI) Division of Cancer Prevention (DCP) convened the "Translational Advances in Cancer Prevention Agent Development (TACPAD) Workshop on Immunomodulatory Agents" as a virtual 2-day workshop on September 13 to 14, 2021. The main goals of this workshop were to foster the exchange of ideas and potentially new collaborative interactions among leading cancer immunoprevention researchers from basic and clinical research and highlight new and emerging trends in immunoprevention. The workshop included an overview of the mechanistic classes of immunomodulatory agents and three sessions covering the gamut from preclinical to clinical studies. The workshop convened individuals working in immunology and cancer prevention to discuss trends in discovery and development of immunomodulatory agents individually and in combination with other chemopreventive agents or vaccines.

Breast cancer vaccines for treatment and prevention

Breast cancer is immunogenic and a variety of vaccines have been designed to boost immunity directed against the disease. The components of a breast cancer vaccine, the antigen, the delivery system, and the adjuvant, can have a significant impact on vaccine immunogenicity. There have been numerous immunogenic proteins identified in all subtypes of breast cancer. The majority of these antigens are weakly immunogenic nonmutated tumor-associated proteins. Mutated proteins and neoantigen epitopes are found only in a small minority of patients and are enriched in the triple negative subtype. Several vaccines have advanced to large randomized Phase II or Phase III clinical trials. None of these trials met their primary endpoint of either progression-free or overall survival. Despite these set-backs investigators have learned important lessons regarding the clinical application of breast cancer vaccines from the type of immune response needed for tumor eradication, Type I T-cell immunity, to the patient populations most likely to benefit from vaccination. Many therapeutic breast cancer vaccines are now being tested in combination with other forms of immune therapy or chemotherapy and radiation. Breast cancer vaccines as single agents are now studied in the context of the prevention of relapse or development of disease. Newer approaches are designing vaccines to prevent breast cancer by intercepting high-risk lesions such as ductal carcinoma in situ to limit the progression of these tumors to invasive cancer. There are also several efforts to develop vaccines for the primary prevention of breast cancer by targeting antigens expressed during breast cancer initiation.

Pembrolizumab with low-dose carboplatin for recurrent platinum-resistant ovarian, fallopian tube, and primary peritoneal cancer: survival and immune correlates

Background

Anti-programmed death 1 (PD1)/programmed cell death ligand 1 (PD-L1) therapies have shown modest activity as monotherapy in recurrent ovarian cancer. Platinum chemotherapies induce T-cell proliferation and enhance tumor recognition. We assessed activity and safety of pembrolizumab with carboplatin in recurrent platinum-resistant ovarian cancer.

Patients and methods

This phase I/II, single-arm clinical trial studied concurrent carboplatin and pembrolizumab in recurrent platinum-resistant ovarian, fallopian tube, and primary peritoneal cancer. Primary platinum refractory patients were excluded. Patients were treated after progression on subsequent non-platinum systemic therapy after becoming platinum resistant or refractory. Pembrolizumab 200 mg was given on day 1 and carboplatin area under the curve 2 on days 8 and 15 of a 3-week cycle until progression. Imaging was assessed by blinded independent review. PD-L1 expression was assessed by immunohistochemistry. Flow cytometry on peripheral blood mononuclear cells was performed for CD3, CD4, CD8, PD1, CTLA4 and Ki67.

Results

The most common treatment-related adverse events were lymphopenia (18%) and anemia (9%) with most being grade 1 or 2 (93%). Of 29 patients treated, 23 patients were evaluable for best objective response: 10.3% (95% CI 2.2 to 27.4) had partial response (PR), 51.7% (95% CI 32.5 to 70.6) had stable disease (SD). 56.5% of patients had decreases in target lesions from baseline. All PD-L1-positive patients achieved PR (3/7, 42.8%) or SD (4/7, 57.2%). Median progression-free survival was 4.63 months (95% CI 4.3 to 4.96). Median OS was 11.3 months (95% CI 6.094 to 16.506). Peripheral CD8+PD1+Ki67+ T cells expanded after 3 (p=0.0015) and 5 (p=0.0023) cycles. CTLA4+PD1+CD8+ T cells decreased through the course of treatment up to the 12th cycle (p=0.004). When stratified by ratio of peripheral CD8+PD1+Ki67+ T cells to tumor burden at baseline, patients with a ratio ≥0.0375 who had a significantly longer median OS of 18.37 months compared with those with a ratio <0.0375 who had a median OS of 8.72 months (p=0.0099). No survival advantage was seen with stratification by tumor burden alone (p=0.24) or by CD8+PD1+Ki67+ T cells alone (p=0.53).

Conclusions

Pembrolizumab with carboplatin was well-tolerated and active in recurrent platinum-resistant ovarian cancer. A ratio of peripheral T-cell exhaustion to radiographic tumor burden may identify patients more likely to benefit from this chemoimmunotherapy.

Trial registration number

NCT03029598.

Immunization with a Plasmid DNA Vaccine Encoding the N-Terminus of Insulin-like Growth Factor Binding Protein-2 in Advanced Ovarian Cancer Leads to High-level Type I Immune Responses

BACKGROUND

Cancer vaccines targeting nonmutated proteins elicit limited type I T-cell responses and can generate regulatory and type II T cells. Class II epitopes that selectively elicit type I or type II cytokines can be identified in nonmutated cancer-associated proteins. In mice, a T-helper I (Th1) selective insulin-like growth factor binding protein-2 (IGFBP-2) N-terminus vaccine generated high levels of IFNγ secreting T cells, no regulatory T cells, and significant antitumor activity. We conducted a phase I trial of T-helper 1 selective IGFBP-2 vaccination in patients with advanced ovarian cancer.

METHODS

Twenty-five patients were enrolled. The IGFBP-2 N-terminus plasmid-based vaccine was administered monthly for 3 months. Toxicity was graded by NCI criteria and antigen-specific T cells measured by IFNγ/IL10 ELISPOT. T-cell diversity and phenotype were assessed.

RESULTS

The vaccine was well tolerated, with 99% of adverse events graded 1 or 2, and generated high levels of IGFBP-2 IFNγ secreting T cells in 50% of patients. Both Tbet⁺ CD4 (P = 0.04) and CD8 (P = 0.007) T cells were significantly increased in immunized patients. There was no increase in GATA3⁺ CD4 or CD8, IGFBP-2 IL10 secreting T cells, or regulatory T cells. A significant increase in T-cell clonality occurred in immunized patients (P = 0.03, pre- vs. post-vaccine) and studies showed the majority of patients developed epitope spreading within IGFBP-2 and/or to other antigens. Vaccine nonresponders were more likely to have preexistent IGFBP-2 specific immunity and demonstrated defects in CD4 T cells, upregulation of PD-1, and downregulation of genes associated with T-cell activation, after immunization.

CONCLUSIONS

IGFBP-2 N-terminus Th1 selective vaccination safely induces type I T cells without evidence of regulatory responses.

Multi-Epitope-Based Vaccines for Colon Cancer Treatment and Prevention

Background

Overexpression of nonmutated proteins involved in oncogenesis is a mechanism by which such proteins become immunogenic. We questioned whether overexpressed colorectal cancer associated proteins found at higher incidence and associated with poor prognosis could be effective vaccine antigens. We explored whether vaccines targeting these proteins could inhibit the development of intestinal tumors in the azoxymethane (AOM)-induced colon model and APC Min mice.

Methods

Humoral immunity was evaluated by ELISA. Web-based algorithms identified putative Class II binding epitopes of the antigens. Peptide and protein specific T-cells were identified from human peripheral blood mononuclear cells using IFN-gamma ELISPOT. Peptides highly homologous between mouse and man were formulated into vaccines and tested for immunogenicity in mice and in vivo tumor challenge. Mice treated with AOM and APC Min transgenic mice were vaccinated and monitored for tumors.

Results

Serum IgG for CDC25B, COX2, RCAS1, and FASCIN1 was significantly elevated in colorectal cancer patient sera compared to volunteers (CDC25B p=0.002, COX-2 p=0.001, FASCIN1 and RCAS1 p<0.0001). Epitopes predicted to bind to human class II MHC were identified for each protein and T-cells specific for both the peptides and corresponding recombinant protein were generated from human lymphocytes validating these proteins as human antigens. Some peptides were highly homologous between mouse and humans and after immunization, mice developed both peptide and protein specific IFN-γ-secreting cell responses to CDC25B, COX2 and RCAS1, but not FASCIN1. FVB/nJ mice immunized with CDC25B or COX2 peptides showed significant inhibition of growth of the syngeneic MC38 tumor compared to control (p<0.0001). RCAS1 peptide vaccination showed no anti-tumor effect. In the prophylactic setting, after immunization with CDC25B or COX2 peptides mice treated with AOM developed significantly fewer tumors as compared to controls (p<0.0002) with 50% of mice remaining tumor free in each antigen group. APC Min mice immunized with CDC25B or COX2 peptides developed fewer small bowel tumors as compared to controls (p=0.01 and p=0.02 respectively).

Conclusions

Immunization with CDC25B and COX2 epitopes consistently suppressed tumor development in each model evaluated. These data lay the foundation for the development of multi-antigen vaccines for the treatment and prevention of colorectal cancer.

Society for Immunotherapy of Cancer (SITC) clinical practice guideline on immunotherapy for the treatment of breast cancer

Breast cancer has historically been a disease for which immunotherapy was largely unavailable. Recently, the use of immune checkpoint inhibitors (ICIs) in combination with chemotherapy for the treatment of advanced/metastatic triple-negative breast cancer (TNBC) has demonstrated efficacy, including longer progression-free survival and increased overall survival in subsets of patients. Based on clinical benefit in randomized trials, ICIs in combination with chemotherapy for the treatment of some patients with advanced/metastatic TNBC have been approved by the United States (US) Food and Drug Administration (FDA), expanding options for patients. Ongoing questions remain, however, about the optimal chemotherapy backbone for immunotherapy, appropriate biomarker-based selection of patients for treatment, the optimal strategy for immunotherapy treatment in earlier stage disease, and potential use in histological subtypes other than TNBC. To provide guidance to the oncology community on these and other important concerns, the Society for Immunotherapy of Cancer (SITC) convened a multidisciplinary panel of experts to develop a clinical practice guideline (CPG). The expert panel drew upon the published literature as well as their clinical experience to develop recommendations for healthcare professionals on these important aspects of immunotherapeutic treatment for breast cancer, including diagnostic testing, treatment planning, immune-related adverse events (irAEs), and patient quality of life (QOL) considerations. The evidence-based and consensus-based recommendations in this CPG are intended to give guidance to cancer care providers treating patients with breast cancer.

A grant-based experiment to train clinical investigators: the AACR/ASCO methods in clinical cancer research workshop

To address the need for clinical investigators in oncology, AACR and ASCO established the Methods in Clinical Cancer Research Workshop (MCCRW). The workshop's objectives were to: (1) provide training in the methods, design, and conduct of clinical trials; (2) ensure that clinical trials met federal and international ethical guidelines; (3) evaluate the effectiveness of the workshop; and (4) create networking opportunities for young investigators with mentoring senior faculty. Educational methods included: (1) didactic lectures; (2) Small Group Discussion Sessions; (3) Protocol Development Groups; (4) one-on-one mentoring. Learning focused on the development of an IRB-ready protocol, which was submitted on the last day of the workshop. Evaluation methods included: (1) pre- and post-workshop tests; (2) students' workshop evaluations; (3) faculty's ratings of protocol development; (4) students' productivity in clinical research after the workshop; (5) an independent assessment of the workshop. From 1996-2014, 1932 students from diverse backgrounds attended the workshop. There was a significant improvement in the students' level of knowledge from the pre- to the post-workshop exams (p < 0.001). Across the classes, student evaluations were very favorable. At the end of the workshop, faculty rated 92-100% of the students' protocols as ready for IRB submission. Intermediate and long-term follow-ups indicated that more than 92% of students were actively involved in patientrelated research, and 66% had implemented five or more protocols. This NCI-sponsored MCCRW has had a major impact on the training of clinicians in their ability to design and implement clinical trials in cancer research.

Abstract 1556: Retinoid X receptor agonists enhances Th1 antigen-specific and polyfunctional T cells with the HER2-IGFBP2-IGF1R vaccine

Bexarotene and 9cUAB30 are highly selective oral retinoid X receptor (RXR) agonists with anti-proliferative activity in breast cancer. We have demonstrated that bexarotene enhances efficacy of a multi-antigen vaccine to prevent breast cancer in the TgMMTV-neu model and increases CD8 T-cell tumor infiltration. We further have shown that RXRα expression is in 24.9±13% of macrophages, 38.6 ±14% of plasmacytic dendritic cells (pDC), and 33.1 ± 16% of monocytic dendritic cells (mDC). Furthermore, the RXR agonists increased Th1 pDC and mDC. We therefore evaluated whether RXR agonists could enhance the vaccine antigen-specific immunogenicity and polyfunctional T cells in the transgenic mouse mammary tumor model TgMMTV-neu. Vaccination with the 150 µg HER2-IGFBP2-IGF1R vaccine and 5 ug GMCSF adjuvant every 2 weeks for four doses significantly increased antigen-specific IFN-γ T cells, but not antigen-specific IL10 T cells, as compared to control vaccination with empty vector. Interestingly, daily oral administration of 30 mg/kg bexarotene for 5 days prior to the HER2-IGFBP2-IGF1R vaccination series increased the IFN-γ immune responses to HER2, IGFBP2, and IGF1R by 1.2, 2.4 and 2.2 fold, respectively, as compared to the HER2-IGFBP2-IGF1R vaccine alone. Daily administration of a higher dose (200 mg/kg) 9cUAB30 for 5 days prior to the HER2-IGFBP2-IGF1R vaccination series increased the IFN-γ immune responses to HER2, IGFBP2, and IGF1R by 2.0, 2.3 and 1.7 fold, respectively, as compared to the HER2-IGFBP2-IGF1R vaccine alone. Control vaccination with either 9cUAB30 or bexarotene had no impact on antigen-specific IFN-γ T cell response. Type I DCs are important for producing polyfunctional CD4+ T cells that release not only IFN-γ but also TNF-α and IL-2. Polyfunctional T cells induce a longer lasting and more effective immune response in vaccines both for infectious diseases and cancer. We demonstrated the addition of bexarotene or 9cUAB30 increased antigen-specific polyfunctional T cells in the TgMMTV-neu (n=15 mice) transgenic mouse mammary tumor model while vaccination alone did not. There were an average of 1.3±0.2% antigen-specific CD4 polyfunctional T cells and 2.7±0.7 antigen-specific CD8 polyfunctional T cells with empty vector and vehicle control (sesame oil). HER2-IGFBP2-IGF1R vaccination following 30 mg/kg bexarotene treatment increased polyfunctional T cells to an average of 6.1±2.0% antigen-specific CD4 polyfunctional T cells (p=0.07) and 20.3±4.1% antigen-specific CD8 polyfunctional T cells (p=0.0003). HER2-IGBP2-IGF1R vaccination after 200 mg/kg 9cUAB30 increased antigen-specific polyfunctional T cells to 7.6±2.0% (p=0.01) and antigen-specific CD8 polyfunctional T cells to 17.6±4.1% (p=0.003). These data indicate that RXR agonists have an immunostimulatory role with multi-antigen cancer vaccines and may augment the anti-tumor activity of vaccines.

Citation Format: Sasha Elizabeth Stanton, Erin Rodmaker, Nicholas Drovetto, Lauren Corulli, Flonia Levy, Venkatram Atigadda, Clinton Grubbs, Romaine Fernando, Shizuko Sei, Mary L. Disis. Retinoid X receptor agonists enhances Th1 antigen-specific and polyfunctional T cells with the HER2-IGFBP2-IGF1R vaccine [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1556.

Final report and long-term outcomes: Phase I trial of a HER2 intracellular plasmid-based vaccine in HER2+ advanced stage breast cancer

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Background: Vaccination with the intracellular domain (ICD) of HER2 in pre-clinical models is both immunogenic and protective against the development of mammary tumors. This study (NCT00436254) was designed to examine the safety and optimal immunogenic dose of a DNA-based vaccine encoding the HER2 ICD in subjects with HER2+ breast cancer. Methods: Sixty-six patients with stage III or IV HER2 + breast cancer in remission or with stable bone only disease were enrolled into three vaccine arms: 1 (10mcg dose of plasmid), 2 (100mcg) and 3 (500mcg). Vaccines were administered i.d. monthly for three immunizations. Endpoints included safety and optimal dose. HER2 specific IFN-gamma immune responses were evaluated and DNA persistence at the vaccine site was assessed. Toxicity and clinical outcomes were followed for 10 years. Results: The majority of vaccine-related toxicity was grade 1 (89%) and grade 2 (11%) and was not significantly different between the three dose arms. All Arms developed HER2 ICD immunity after vaccination, however, patients in Arm 2 and Arm 3 had significantly better immune responses (of higher magnitude and at most time points) than patients in Arm 1 (p=0.003 and p<0.001, respectively) after adjusting for baseline factors. At 60 weeks, the number of patients who maintained the greatest fold-difference in HER2 ICD immune responses from their baseline was highest in Arm 2 (73%) when compared to Arm 1 (47%) and Arm 3 (45%). Associations between ICD responses and plasmid DNA persistence at the vaccine site were estimated via linear regression models. HER ICD immunity after the end of immunizations, relative to baseline, was significantly lower in patients with DNA persistence at week 16 compared to those without persistence (p=0.02). Patients at the highest dose demonstrated the greatest incidence of plasmid persistence (92%) as compared to 33% in Arm 1 and 10% in Arm 2. The median time of follow-up was 118.6 months (Arm 1), 99.7 months (Arm 2), and 73.5 months (Arm 3). The median OS and PFS has not been reached in any Arm and did not differ with respect to treatment arm (Log-rank p-value 0.36 for OS, and 0.63 for PFS). However, we observed a separation of Kaplan-Meier curves for OS from about 40 months and curves for PFS from about 30 months, and the separation maintained until the end of the study for Arm 2 versus Arm 1 and Arm 3. One patient in Arm 2 developed lymphocytic colitis 2.2 years from enrollment deemed possibly related to vaccination. Conclusions: An intermediate dose (100mcg) of vaccine was immunogenic and associated with persistence of immunity at 60 weeks. A randomized phase II trial of the HER2 ICD plasmid-based vaccine in the neoadjuvant setting is in development. Clinical trial information: NCT00436254.

Tumor-associated autoantibodies from mouse breast cancer models are found in serum of breast cancer patients

B cell responses to tumor antigens occur early in breast tumors and may identify immunogenic drivers of tumorigenesis. Sixty-two candidate antigens were identified prior to palpable tumor development in TgMMTV-neu and C3(1)Tag transgenic mouse mammary tumor models. Five antigens (VPS35, ARPC2, SERBP1, KRT8, and PDIA6) were selected because their decreased expression decreased survival in human HER2 positive and triple negative cell lines in a siRNA screen. Vaccination with antigen-specific epitopes, conserved between mouse and human, inhibited tumor growth in both transgenic mouse models. Increased IgG autoantibodies to the antigens were elevated in serum from women with ductal carcinoma in situ (DCIS) and invasive breast cancer (IBC). The autoantibodies differentiated women with DCIS from control with AUC 0.93 (95% CI 0.88-0.98, p < 0.0001). The tumor antigens identified early in the development of breast cancer in mouse mammary tumor models were conserved in human disease, and potentially identify early diagnostic markers in human breast tumors.

Differentiation and Regulation of TH Cells: A Balancing Act for Cancer Immunotherapy

Current success of immunotherapy in cancer has drawn attention to the subsets of T_H cells in the tumor which are critical for activation of anti-tumor response either directly by themselves or by stimulating cytotoxic T cell activity. However, presence of immunosuppressive pro-tumorigenic T_H subsets in the tumor milieu further contributes to the complexity of regulation of T_H cell-mediated immune response. In this review, we present an overview of the multifaceted positive and negative effects of T_H cells, with an emphasis on regulation of different T_H cell subtypes by various immune cells, and how a delicate balance of contradictory signals can influence overall success of cancer immunotherapy. We focus on the regulatory network that encompasses dendritic cell-induced activation of CD4⁺ T_H1 cells and subsequent priming of CD8⁺ cytotoxic T cells, along with intersecting anti-inflammatory and pro-tumorigenic T_H2 cell activity. We further discuss how other tumor infiltrating immune cells such as immunostimulatory T_H9 and T_fh cells, immunosuppressive T_reg cells, and the duality of T_H17 function contribute to tip the balance of anti- vs pro-tumorigenic T_H responses in the tumor. We highlight the developing knowledge of CD4⁺ T_H1 immune response against neoantigens/oncodrivers, impact of current immunotherapy strategies on CD4⁺ T_H1 immunity, and how opposing action of T_H cell subtypes can be explored further to amplify immunotherapy success in patients. Understanding the nuances of CD4⁺ T_H cells regulation and the molecular framework undergirding the balancing act between anti- vs pro-tumorigenic T_H subtypes is critical for rational designing of immunotherapies that can bypass therapeutic escape to maximize the potential of immunotherapy.

Meeting Report: Translational Advances in Cancer Prevention Agent Development Meeting

The Division of Cancer Prevention of the National Cancer Institute (NCI) and the Office of Disease Prevention of the National Institutes of Health co-sponsored the Translational Advances in Cancer Prevention Agent Development Meeting on August 27 to 28, 2020. The goals of this meeting were to foster the exchange of ideas and stimulate new collaborative interactions among leading cancer prevention researchers from basic and clinical research; highlight new and emerging trends in immunoprevention and chemoprevention as well as new information from clinical trials; and provide information to the extramural research community on the significant resources available from the NCI to promote prevention agent development and rapid translation to clinical trials. The meeting included two plenary talks and five sessions covering the range from pre-clinical studies with chemo/immunopreventive agents to ongoing cancer prevention clinical trials. In addition, two NCI informational sessions describing contract resources for the preclinical agent development and cooperative grants for the Cancer Prevention Clinical Trials Network were also presented.