Widespread CD4+ T-cell reactivity to novel hTERT epitopes following vaccination of cancer patients with a single hTERT peptide GV1001

Clinical research progress of telomerase targeted cancer immunotherapy: a literature review

Background and Objective

Telomerase is activated or overexpressed in 85-90% of tumors, which maintains the length of telomere and has become an important anti-cancer target. Increasing clinical and preclinical data suggest that telomerase-targeted cancer immunotherapy could achieve effective killing of tumor cells in vivo. This article reviews the research progress of telomerase targeted cancer immunotherapy in clinical and pre-clinical trials, aiming to provide a reference for further clinical research and treatment of cancers.

Methods

We investigated the research progress of telomerase immunotherapy in the last 20 years from four electronic databases.

Key Content and Findings

Telomerase-targeted immunotherapies have been developed with the arising of a new era in immuno-oncology, including peptide vaccines, DNA vaccines, dendritic cells (DCs), adoptive cell transfer (ACT) therapies, antibodies, etc. Some of them have been approved for undergoing clinical trials by the Food and Drug Administration (FDA) for the treatment of various cancers, such as pancreatic cancer, non-small cell lung cancer, melanoma, leukaemia. Of all the treatment modalities, vaccines are the primary treatment methods, some of which have been even entered into phase III clinical trials. The main clinical application direction of telomerase vaccine is the combination with other drugs and treatment modalities, including combination with other vaccines targeting human telomerase reverse transcriptase (hTERT), traditional chemotherapy drugs and immunosuppressors. We also summarized the recent findings of immunotherapy targeting hTERT, focusing on various vaccines and the current status of associated clinical trials. We further discussed the advantages, disadvantages and potential developmental directions of various telomerase-targeted immunotherapies.

Conclusions

Telomerase-targeted cancer immunotherapy has promising prospects in improving patient survival expectancy. This review may provide data support and design ideas for all researchers and pharmaceutical enterprises in this field.

Investigating underlying molecular mechanisms, signaling pathways, emerging therapeutic approaches in pancreatic cancer

Pancreatic adenocarcinoma, a clinically challenging malignancy constitutes a significant contributor to cancer-related mortality, characterized by an inherently poor prognosis. This review aims to provide a comprehensive understanding of pancreatic adenocarcinoma by examining its multifaceted etiologies, including genetic mutations and environmental factors. The review explains the complex molecular mechanisms underlying its pathogenesis and summarizes current therapeutic strategies, including surgery, chemotherapy, and emerging modalities such as immunotherapy. Critical molecular pathways driving pancreatic cancer development, including KRAS, Notch, and Hedgehog, are discussed. Current therapeutic strategies, including surgery, chemotherapy, and radiation, are discussed, with an emphasis on their limitations, particularly in terms of postoperative relapse. Promising research areas, including liquid biopsies, personalized medicine, and gene editing, are explored, demonstrating the significant potential for enhancing diagnosis and treatment. While immunotherapy presents promising prospects, it faces challenges related to immune evasion mechanisms. Emerging research directions, encompassing liquid biopsies, personalized medicine, CRISPR/Cas9 genome editing, and computational intelligence applications, hold promise for refining diagnostic approaches and therapeutic interventions. By integrating insights from genetic, molecular, and clinical research, innovative strategies that improve patient outcomes can be developed. Ongoing research in these emerging fields holds significant promise for advancing the diagnosis and treatment of this formidable malignancy.

hTERT Peptide Fragment GV1001 Prevents the Development of Porphyromonas gingivalis-Induced Periodontal Disease and Systemic Disorders in ApoE-Deficient Mice

GV1001, an anticancer vaccine, exhibits other biological functions, including anti-inflammatory and antioxidant activity. It also suppresses the development of ligature-induced periodontitis in mice. Porphyromonas gingivalis (Pg), a major human oral bacterium implicated in the development of periodontitis, is associated with various systemic disorders, such as atherosclerosis and Alzheimer's disease (AD). This study aimed to explore the protective effects of GV1001 against Pg-induced periodontal disease, atherosclerosis, and AD-like conditions in Apolipoprotein (ApoE)-deficient mice. GV1001 effectively mitigated the development of Pg-induced periodontal disease, atherosclerosis, and AD-like conditions by counteracting Pg-induced local and systemic inflammation, partly by inhibiting the accumulation of Pg DNA aggregates, Pg lipopolysaccharides (LPS), and gingipains in the gingival tissue, arterial wall, and brain. GV1001 attenuated the development of atherosclerosis by inhibiting vascular inflammation, lipid deposition in the arterial wall, endothelial to mesenchymal cell transition (EndMT), the expression of Cluster of Differentiation 47 (CD47) from arterial smooth muscle cells, and the formation of foam cells in mice with Pg-induced periodontal disease. GV1001 also suppressed the accumulation of AD biomarkers in the brains of mice with periodontal disease. Overall, these findings suggest that GV1001 holds promise as a preventive agent in the development of atherosclerosis and AD-like conditions associated with periodontal disease.

Activated B-Cells enhance epitope spreading to support successful cancer immunotherapy

Immune checkpoint therapies (ICT) have transformed the treatment of cancer over the past decade. However, many patients do not respond or suffer relapses. Successful immunotherapy requires epitope spreading, but the slow or inefficient induction of functional antitumoral immunity delays the benefit to patients or causes resistances. Therefore, understanding the key mechanisms that support epitope spreading is essential to improve immunotherapy. In this review, we highlight the major role played by B-cells in breaking immune tolerance by epitope spreading. Activated B-cells are key Antigen-Presenting Cells (APC) that diversify the T-cell response against self-antigens, such as ribonucleoproteins, in autoimmunity but also during successful cancer immunotherapy. This has important implications for the design of future cancer vaccines.

Telomerase-related advances in hepatocellular carcinoma: A bibliometric and visual analysis

BACKGROUND

As a critical early event in hepatocellular carcinogenesis, telomerase activation might be a promising and critical biomarker for hepatocellular carcinoma (HCC) patients, and its function in the genesis and treatment of HCC has gained much attention over the past two decades.

AIM

To perform a bibliometric analysis to systematically assess the current state of research on HCC-related telomerase.

METHODS

The Web of Science Core Collection and PubMed were systematically searched to retrieve publications pertaining to HCC/telomerase limited to "articles" and "reviews" published in English. A total of 873 relevant publications related to HCC and telomerase were identified. We employed the Bibliometrix package in R to extract and analyze the fundamental information of the publications, such as the trends in the publications, citation counts, most prolific or influential writers, and most popular journals; to screen for keywords occurring at high frequency; and to draw collaboration and cluster analysis charts on the basis of coauthorship and co-occurrences. VOSviewer was utilized to compile and visualize the bibliometric data.

RESULTS

A surge of 51 publications on HCC/telomerase research occurred in 2016, the most productive year from 1996 to 2023, accompanied by the peak citation count recorded in 2016. Up to December 2023, 35226 citations were made to all publications, an average of 46.6 citations to each paper. The United States received the most citations (n = 13531), followed by China (n = 7427) and Japan (n = 5754). In terms of national cooperation, China presented the highest centrality, its strongest bonds being to the United States and Japan. Among the 20 academic institutions with the most publications, ten came from China and the rest of Asia, though the University of Paris Cité, Public Assistance-Hospitals of Paris, and the National Institute of Health and Medical Research (INSERM) were the most prolific. As for individual contributions, Hisatomi H, Kaneko S, and Ide T were the three most prolific authors. Kaneko S ranked first by H-index, G-index, and overall publication count, while Zucman-Rossi J ranked first in citation count. The five most popular journals were the World Journal of Gastroenterology, Hepatology, Journal of Hepatology, Oncotarget, and Oncogene, while Nature Genetics, Hepatology, and Nature Reviews Disease Primers had the most citations. We extracted 2293 keywords from the publications, 120 of which appeared more than ten times. The most frequent were HCC, telomerase and human telomerase reverse transcriptase (hTERT). Keywords such as mutational landscape, TERT promoter mutations, landscape, risk, and prognosis were among the most common issues in this field in the last three years and may be topics for research in the coming years.

CONCLUSION

Our bibliometric analysis provides a comprehensive overview of HCC/telomerase research and insights into promising upcoming research.

A phase 1 trial of human telomerase reverse transcriptase (hTERT) vaccination combined with therapeutic strategies to control immune-suppressor mechanisms

The presence of inhibitory immune cells and difficulty in generating activated effector T cells remain obstacles to development of effective cancer vaccines. We designed a vaccine regimen combining human telomerase reverse transcriptase (hTERT) peptides with concomitant therapies targeting regulatory T cells (Tregs) and cyclooxygenase-2 (COX2)-mediated immunosuppression. This Phase 1 trial combined an hTERT-derived 7-peptide library, selected to ensure presentation by both HLA class-I and class-II in 90% of patients, with oral low-dose cyclophosphamide (to modulate Tregs) and the COX2 inhibitor celecoxib. Adjuvants were Montanide and topical TLR-7 agonist, to optimise antigen presentation. The primary objective was determination of the safety and tolerability of this combination therapy, with anti-cancer activity, immune response and detection of antigen-specific T cells as additional endpoints. Twenty-nine patients with advanced solid tumours were treated. All were multiply-pretreated, and the majority had either colorectal or prostate cancer. The most common adverse events were injection-site reactions, fatigue and nausea. Median progression-free survival was 9 weeks, with no complete or partial responses, but 24% remained progression-free for ≥6 months. Immunophenotyping showed post-vaccination expansion of CD4+ and CD8+ T cells with effector phenotypes. The in vitro re-challenge of T cells with hTERT peptides, TCR sequencing, and TCR similarity index analysis demonstrated the expansion following vaccination of oligoclonal T cells with specificity for hTERT. However, a population of exhausted PD-1+ cytotoxic T cells was also expanded in vaccinated patients. This vaccine combination regimen was safe and associated with antigen-specific immunological responses. Clinical activity could be improved in future by combination with anti-PD1 checkpoint inhibition to address the emergence of an exhausted T cell population.

Bridging responses to a human telomerase reverse transcriptase-based peptide cancer vaccine candidate in a mechanism-based model

Therapeutic cancer vaccines are novel immuno-therapeutics, aiming to improve clinical outcomes with other immunotherapies. However, obstacles to their successful clinical development remain, which model-informed drug development approaches may address. UV1 is a telomerase based therapeutic cancer vaccine candidate being investigated in phase I clinical trials for multiple indications. We developed a mechanism-based model structure, using a nonlinear mixed-effects modeling techniques, based on longitudinal tumor sizes (sum of the longest diameters, SLD), UV1-specific immunological assessment (stimulation index, SI) and overall survival (OS) data obtained from a UV1 phase I trial including non-small cell lung cancer (NSCLC) patients and a phase I/IIa trial including malignant melanoma (MM) patients. The final structure comprised a mechanistic tumor growth dynamics (TGD) model, a model describing the probability of observing a UV1-specific immune response (SI ≥ 3) and a time-to-event model for OS. The mechanistic TGD model accounted for the interplay between the vaccine peptides, immune system and tumor. The model-predicted UV1-specific effector CD4+ T cells induced tumor shrinkage with half-lives of 103 and 154 days in NSCLC and MM patients, respectively. The probability of observing a UV1-specific immune response was mainly driven by the model-predicted UV1-specific effector and memory CD4+ T cells. A high baseline SLD and a high relative increase from nadir were identified as main predictors for a reduced OS in NSCLC and MM patients, respectively. Our model predictions highlighted that additional maintenance doses, i.e. UV1 administration for longer periods, may result in more sustained tumor size shrinkage.

Efficacy of GV1001 with gemcitabine/capecitabine in previously untreated patients with advanced pancreatic ductal adenocarcinoma having high serum eotaxin levels (KG4/2015): an open-label, randomised, Phase 3 trial

BACKGROUND

The TeloVac study indicated GV1001 did not improve the survival of advanced pancreatic ductal adenocarcinoma (PDAC). However, the cytokine examinations suggested that high serum eotaxin levels may predict responses to GV1001. This Phase III trial assessed the efficacy of GV1001 with gemcitabine/capecitabine for eotaxin-high patients with untreated advanced PDAC.

METHODS

Patients recruited from 16 hospitals received gemcitabine (1000 mg/m2, D 1, 8, and 15)/capecitabine (830 mg/m2 BID for 21 days) per month either with (GV1001 group) or without (control group) GV1001 (0.56 mg; D 1, 3, and 5, once on week 2-4, 6, then monthly thereafter) at random in a 1:1 ratio. The primary endpoint was overall survival (OS) and secondary end points included time to progression (TTP), objective response rate, and safety.

RESULTS

Total 148 patients were randomly assigned to the GV1001 (n = 75) and control groups (n = 73). The GV1001 group showed improved median OS (11.3 vs. 7.5 months, P = 0.021) and TTP (7.3 vs. 4.5 months, P = 0.021) compared to the control group. Grade >3 adverse events were reported in 77.3% and 73.1% in the GV1001 and control groups (P = 0.562), respectively.

CONCLUSIONS

GV1001 plus gemcitabine/capecitabine improved OS and TTP compared to gemcitabine/capecitabine alone in eotaxin-high patients with advanced PDAC.

CLINICAL TRIAL REGISTRATION

NCT02854072.

Retrospective Analysis of the Clinical Characteristics of Patients with Breast Cancer Treated with Telomerase Peptide Immunotherapy Combined with Cytotoxic Chemotherapy

Purpose

Telomerase activation, a critical step in cancer progression, occurs in approximately 95% of breast cancer cases. Telomerase is an attractive therapeutic target for breast cancer owing to its unique expression pattern. GV1001, a telomerase-derived peptide, is loaded onto human leukocyte antigen (HLA) class II antigen-presenting cells and binds to CD4+ T cell activating immune responses. This study aimed to evaluate the effectiveness and safety of co-administration of GV1001 and cytotoxic chemotherapy in patients with heavily-treated metastatic breast cancer.

Patients and methods

We analyzed 63 patients with breast cancer who received both GV1001 and cytotoxic chemotherapy. The GV 1001 administration methods involves 0.56 mg intradermal injection three times during the first week, one time at weeks 2, 3, 4, and 6, and then once every 28 days. The primary endpoint of this study was quality of life according to EORTC QLO-C30 and EQ-5D, while the secondary endpoint was the antitumor response according to RECIST 1.1, progression-free survival, overall survival, and toxicity profile.

Results

In 34 patients with HR+ breast cancer evaluable for tumor response, the disease control rate (DCR) and overall response rate (ORR) were 58.8% and 26.4%, respectively. The DCR and ORR were 66.6% and 28.5% in 21 patients with HER-2+ and 50% and 25% in patients with triple-negative breast cancer (TNBC), respectively. The median progression free survival was 10.4, 8.7, and 5.6 months in HR+, HER-2+, TNBC, respectively. The overall survival was 19.7, 13.2, and 9.4 months for patients with HR+, HER-2+, and TNBC, respectively. Most patients had an improved quality of life with statistically significant differences in some variables. The patients in this study experienced no additional toxicities other than the cytotoxic chemotherapy-associated side effects.

Conclusion

GV1001 is a relatively safe anticancer vaccine for patients with heavily-treated breast cancer and can to improve the quality of life.

Improving the efficacy of peptide vaccines in cancer immunotherapy

Peptide vaccines have shown great potential in cancer immunotherapy by targeting tumor antigens and activating the patient's immune system to mount a specific response against cancer cells. However, the efficacy of peptide vaccines in inducing a sustained immune response and achieving clinical benefit remains a major challenge. In this review, we discuss the current status of peptide vaccines in cancer immunotherapy and strategies to improve their efficacy. We summarize the recent advancements in the development of peptide vaccines in pre-clinical and clinical settings, including the use of novel adjuvants, neoantigens, nano-delivery systems, and combination therapies. We also highlight the importance of personalized cancer vaccines, which consider the unique genetic and immunological profiles of individual patients. We also discuss the strategies to enhance the immunogenicity of peptide vaccines such as multivalent peptides, conjugated peptides, fusion proteins, and self-assembled peptides. Although, peptide vaccines alone are weak immunogens, combining peptide vaccines with other immunotherapeutic approaches and developing novel approaches such as personalized vaccines can be promising methods to significantly enhance their efficacy and improve the clinical outcomes for cancer patients.

Clinical Activity of Combined Telomerase Vaccination and Pembrolizumab in Advanced Melanoma: Results from a Phase I Trial

PURPOSE

Cancer vaccines represent a novel treatment modality with a complementary mode of action addressing a crucial bottleneck for checkpoint inhibitor (CPI) efficacy. CPIs are expected to release brakes in T-cell responses elicited by vaccination, leading to more robust immune responses. Increased antitumor T-cell responses may confer increased antitumor activity in patients with less immunogenic tumors, a subgroup expected to achieve reduced benefit from CPIs alone. In this trial, a telomerase-based vaccine was combined with pembrolizumab to assess the safety and clinical activity in patients with melanoma.

PATIENTS AND METHODS

Thirty treatment-naïve patients with advanced melanoma were enrolled. Patients received intradermal injections of UV1 with adjuvant GM-CSF at two dose levels, and pembrolizumab according to the label. Blood samples were assessed for vaccine-induced T-cell responses, and tumor tissues were collected for translational analyses. The primary endpoint was safety, with secondary objectives including progression-free survival (PFS), overall survival (OS), and objective response rate (ORR).

RESULTS

The combination was considered safe and well-tolerated. Grade 3 adverse events were observed in 20% of patients, with no grade 4 or 5 adverse events reported. Vaccination-related adverse events were mostly mild injection site reactions. The median PFS was 18.9 months, and the 1- and 2-year OS rates were 86.7% and 73.3%, respectively. The ORR was 56.7%, with 33.3% achieving complete responses. Vaccine-induced immune responses were observed in evaluable patients, and inflammatory changes were detected in posttreatment biopsies.

CONCLUSIONS

Encouraging safety and preliminary efficacy were observed. Randomized phase II trials are currently ongoing.

Therapeutic cancer vaccination against telomerase: clinical developments in melanoma

PURPOSE OF REVIEW

Checkpoint inhibitors (CPIs) have revolutionized treatment outcomes for patients with malignant melanoma. Long-term follow-up shows that a substantial subset of patients who exhibit clinical responses achieve extended overall survival. Nevertheless, most patients do not achieve durable benefit from CPIs, and improvements are urgently needed. The clinical efficacy of CPIs depends on highly variable preexisting spontaneous T-cell immune responses. Cancer vaccines represent an independent treatment modality uniquely capable of expanding the repertoire of tumor-specific T cells in cancer patients and thus have the capacity to compensate for the variability in spontaneous T-cell responses. Vaccines are, therefore, considered attractive components in a CPI-combination strategy.

RECENT FINDINGS

Here we discuss recent results obtained through therapeutic vaccination against telomerase human telomerase reverse transcriptase (hTERT). Recent publications on translational research and clinical results from phase I trials indicate that vaccination against telomerase in combination with CPIs provides relevant immune responses, negligible added toxicity, and signals of clinical efficacy.

CONCLUSION

In the near future, randomized data from clinical trials involving therapeutic cancer vaccines and checkpoint inhibitors will be available. Positive readout may spark broad development and allow cancer vaccines to find their place in the clinic as an important component in multiple future CPI combinations.

Safety, Immunogenicity, and 1-Year Efficacy of Universal Cancer Peptide-Based Vaccine in Patients With Refractory Advanced Non-Small-Cell Lung Cancer: A Phase Ib/Phase IIa De-Escalation Study

PURPOSE

Universal cancer peptide-based vaccine (UCPVax) is a therapeutic vaccine composed of two highly selected helper peptides to induce CD4+ T helper-1 response directed against telomerase. This phase Ib/IIa trial was designed to test the safety, immunogenicity, and efficacy of a three-dose schedule in patients with metastatic non-small-cell lung cancer (NSCLC).

PATIENTS AND METHODS

Patients with refractory NSCLC were assigned to receive three vaccination doses of UCPVax (0.25 mg, 0.5 mg, and 1 mg) using a Bayesian-based phase Ib followed by phase IIa de-escalating design. The primary end points were dose-limiting toxicity and immune response after three first doses of vaccine. Secondary end points were overall survival (OS) and progression-free survival at 1 year.

RESULTS

A total of 59 patients received UCPVax; 95% had three prior lines of systemic therapy. No dose-limiting toxicity was observed in 15 patients treated in phase Ib. The maximum tolerated dose was 1 mg. Fifty-one patients were eligible for phase IIa. The third and sixth dose of UCPVax induced specific CD4+ T helper 1 response in 56% and 87.2% of patients, respectively, with no difference between three dose levels. Twenty-one (39%) patients achieved disease control (stable disease, n = 20; complete response, n = 1). The 1-year OS was 34.1% (95% CI, 23.1 to 50.4), and the median OS was 9.7 months, with no significant difference between dose levels. The 1-year progression-free survival and the median OS were 17.2% (95% CI, 7.8 to 38.3) and 11.6 months (95% CI, 9.7 to 16.7) in immune responders (P = .015) and 4.5% (95% CI, 0.7 to 30.8) and 5.6 months (95% CI, 2.5 to 10) in nonresponders (P = .005), respectively.

CONCLUSION

UCPVax was highly immunogenic and safe and provide interesting 1-year OS rate in heavily pretreated advanced NSCLC.

A novel telomerase-derived peptide GV1001-mediated inhibition of angiogenesis: Regulation of VEGF/VEGFR-2 signaling pathways

GV1001, a human telomerase reverse transcriptase catalytic subunit-derived 16-mer peptide, has been developed as a novel anticancer vaccine against various cancers including pancreatic cancer. In the current study, we demonstrate the regulatory roles and mechanisms of GV1001 in endothelial cell responses in vitro and microvessel sprouting ex vivo. GV1001 markedly inhibits vascular endothelial growth factor-A (VEGF-A)-stimulated endothelial cell permeability, proliferation, migration, invasion, tube formation as well as microvessel outgrowth from rat aortic rings. These anti-angiogenic effects of GV1001 were associated with the inhibition of VEGF-A/VEGFR-2 signaling pathways, redistribution of vascular endothelial-cadherin to cell-cell contacts, and down-regulation of VEGFR-2 and matrix metalloproteinase-2. Furthermore, GV1001 suppresses the proliferation and invasion of non-small cell lung cancer cells, and the release of VEGF from the cells, suggesting the regulatory role of GV1001 in tumor-derived angiogenesis as well as cancer cell growth and progression. Collectively, our study reports the pharmacological potential of GV1001 in the regulation of angiogenesis, and warrants further evaluation and development of GV1001 as a promising therapeutic agent for a variety of angiogenesis-related diseases including cancer.

A phase I/II escalation trial design T-RAD: Treatment of metastatic lung cancer with mRNA-engineered T cells expressing a T cell receptor targeting human telomerase reverse transcriptase (hTERT)

Background

Adoptive cellular therapy (ACT) with genetically modified T cells aims to redirect T cells against resistant cancers through introduction of a T cell receptor (TCR). The Radium-4 TCR was isolated from a responding patient in a cancer vaccination study and recognizes the enzymatic component of human Telomerase Reverse Transcriptase (hTERT) presented on MHC class II (HLA-DP04). hTERT is a constitutively overexpressed tumor-associated antigen present in most human cancers, including non-small-cell lung cancer (NSCLC), which is the second most common type of cancer worldwide. Treatment alternatives for relapsing NSCLC are limited and survival is poor. To improve patient outcome we designed a TCR-based ACT study targeting hTERT.

Methods

T-RAD is a phase I/II study to evaluate the safety and efficacy of Radium-4 mRNA electroporated autologous T cells in the treatment of metastatic NSCLC with no other treatment option. Transient TCR expression is applied for safety considerations. Participants receive two intravenous injections with escalating doses of redirected T cells weekly for 6 consecutive weeks. Primary objectives are safety and tolerability. Secondary objectives include progression-free survival, time to progression, overall survival, patient reported outcomes and overall radiological response.

Discussion

Treatment for metastatic NSCLC is scarce and new personalized treatment options are in high demand. hTERT is a tumor target applicable to numerous cancer types. This proof-of-concept study will explore for the first time the safety and efficacy of TCR mRNA electroporated autologous T cells targeting hTERT. The T-RAD study will thus evaluate an attractive candidate for future immunotherapy of solid tumors.

Targeting telomeres: advances in telomere maintenance mechanism-specific cancer therapies

Cancer cells establish replicative immortality by activating a telomere-maintenance mechanism (TMM), be it telomerase or the alternative lengthening of telomeres (ALT) pathway. Targeting telomere maintenance represents an intriguing opportunity to treat the vast majority of all cancer types. Whilst telomerase inhibitors have historically been heralded as promising anticancer agents, the reality has been more challenging, and there are currently no therapeutic options for cancer types that use ALT despite their aggressive nature and poor prognosis. In this Review, we discuss the mechanistic differences between telomere maintenance by telomerase and ALT, the current methods used to detect each mechanism, the utility of these tests for clinical diagnosis, and recent developments in the therapeutic strategies being employed to target both telomerase and ALT. We present notable developments in repurposing established therapeutic agents and new avenues that are emerging to target cancer types according to which TMM they employ. These opportunities extend beyond inhibition of telomere maintenance, by finding and exploiting inherent weaknesses in the telomeres themselves to trigger rapid cellular effects that lead to cell death.

The Era of Cytotoxic CD4 T Cells

In 1986, Mosmann and Coffman identified 2 functionally distinct subsets of activated CD4 T cells, Th1 and Th2 cells, being key in distinct T cell mediated responses. Over the past three decades, our understanding of CD4 T cell differentiation has expanded and the initial paradigm of a dichotomic CD4 T cell family has been revisited to accommodate a constantly growing number of functionally distinct CD4 T helper and regulatory subpopulations. Of note, CD4 T cells with cytotoxic functions have also been described, initially in viral infections, autoimmune disorders and more recently also in cancer settings. Here, we provide an historical overview on the discovery and characterization of cytotoxic CD4 T cells, followed by a description of their mechanisms of cytotoxicity. We emphasize the relevance of these cells in disease conditions, particularly in cancer, and we provide insights on how to exploit these cells in immunotherapy.

Durable and dynamic hTERT immune responses following vaccination with the long-peptide cancer vaccine UV1: long-term follow-up of three phase I clinical trials

BACKGROUND

Therapeutic cancer vaccines represent a promising approach to improve clinical outcomes with immune checkpoint inhibition. UV1 is a second generation telomerase-targeting therapeutic cancer vaccine being investigated across multiple indications. Although telomerase is a near-universal tumor target, different treatment combinations applied across indications may affect the induced immune response. Three phase I/IIa clinical trials covering malignant melanoma, non-small cell lung cancer, and prostate cancer have been completed, with patients in follow-up for up to 8 years.

METHODS

52 patients were enrolled across the three trials. UV1 was given as monotherapy in the lung cancer trial and concurrent with combined androgen blockade in the prostate cancer trial. In the melanoma study, patients initiated ipilimumab treatment 1 week after the first vaccine dose. Patients were followed for UV1-specific immune responses at frequent intervals during vaccination, and every 6 months for up to 8 years in a follow-up period. Phenotypic and functional characterizations were performed on patient-derived vaccine-specific T cell responses.

RESULTS

In total, 78.4% of treated patients mounted a measurable vaccine-induced T cell response in blood. The immune responses in the malignant melanoma trial, where UV1 was combined with ipilimumab, occurred more rapidly and frequently than in the lung and prostate cancer trials. In several patients, immune responses peaked years after their last vaccination. An in-depth characterization of the immune responses revealed polyfunctional CD4+ T cells producing interferon-γ and tumor necrosis factor-α on interaction with their antigen.

CONCLUSION

Long-term immunomonitoring of patients showed highly dynamic and persistent telomerase peptide-specific immune responses lasting up to 7.5 years after the initial vaccination, suggesting a plausible functional role of these T cells in long-term survivors. The superior immune response kinetics observed in the melanoma study substantiate the rationale for future combinatorial treatment strategies with UV1 vaccination and checkpoint inhibition for rapid and frequent induction of anti-telomerase immune responses in patients with cancer.

Peptide-based delivery of therapeutics in cancer treatment

Current delivery strategies for cancer therapeutics commonly cause significant systemic side effects due to required high doses of therapeutic, inefficient cellular uptake of drug, and poor cell selectivity. Peptide-based delivery systems have shown the ability to alleviate these issues and can significantly enhance therapeutic loading, delivery, and cancer targetability. Peptide systems can be tailor-made for specific cancer applications. This review describes three peptide classes, targeting, cell penetrating, and fusogenic peptides, as stand-alone nanoparticle systems, conjugations to nanoparticle systems, or as the therapeutic modality. Peptide nanoparticle design, characteristics, and applications are discussed as well as peptide applications in the clinical space.

Telomeres and Cancer

Telomeres cap the ends of eukaryotic chromosomes and are indispensable chromatin structures for genome protection and replication. Telomere length maintenance has been attributed to several functional modulators, including telomerase, the shelterin complex, and the CST complex, synergizing with DNA replication, repair, and the RNA metabolism pathway components. As dysfunctional telomere maintenance and telomerase activation are associated with several human diseases, including cancer, the molecular mechanisms behind telomere length regulation and protection need particular emphasis. Cancer cells exhibit telomerase activation, enabling replicative immortality. Telomerase reverse transcriptase (TERT) activation is involved in cancer development through diverse activities other than mediating telomere elongation. This review describes the telomere functions, the role of functional modulators, the implications in cancer development, and the future therapeutic opportunities.

Peptide vaccine targeting mutated GNAS: a potential novel treatment for pseudomyxoma peritonei

Background

Pseudomyxoma peritonei (PMP) is a rare, slow-growing abdominal cancer with no efficacious treatment options in non-resectable and recurrent cases. Otherwise, rare activating mutations in the GNAS oncogene are remarkably frequent in PMP and the mutated gene product, guanine nucleotide-binding protein α subunit (Gsα), is a potential tumor neoantigen, presenting an opportunity for targeting by a therapeutic cancer vaccine.

Methods

Tumor and blood samples were collected from 25 patients undergoing surgery for PMP (NCT02073500). GNAS mutation analysis was performed by next-generation targeted sequencing or digital droplet PCR. Responses to stimulation with Gsα mutated (point mutations R201H and R201C) 30 mer peptides were analyzed in peripheral blood T cells derived from patients with PMP and healthy donors. Fresh PMP tumor samples were analyzed by mass cytometry using a panel of 35 extracellular markers, and cellular subpopulations were clustered and visualized using the visual stochastic network embedding analysis tool.

Results

GNAS mutations were detected in 22/25 tumor samples (88%; R201H and R201C mutations detected in 16 and 6 cases, respectively). Strong T cell proliferation against Gsα mutated peptides was observed in 18/24 patients with PMP. Mass cytometry analysis of tumor revealed infiltration of CD3 +T cells in most samples, with variable CD4+:CD8 + ratios. A large proportion of T cells expressed immune checkpoint molecules, in particular programmed death receptor-1 and T cell immunoreceptor with Ig and ITIM, indicating that these T cells were antigen experienced.

Conclusion

These findings point to the existence of a pre-existing immunity in patients with PMP towards mutated Gsα, which has been insufficient to control tumor growth, possibly because of inhibition of antitumor T cells by upregulation of immune checkpoint molecules. The results form a rationale for exploring peptide vaccination with Gsα peptides in combination with immune checkpoint inhibiton as a possible curative treatment for PMP and other GNAS mutated cancers.

Telomerase as a Target for Therapeutic Cancer Vaccines and Considerations for Optimizing Their Clinical Potential

Telomerase-based therapeutic cancer vaccines (TCVs) have been under clinical investigation for the past two decades. Despite past failures, TCVs have gained renewed enthusiasm for their potential to improve the efficacy of checkpoint inhibition. Telomerase stands as an attractive target for TCVs due to its almost universal presence in cancer and its essential function promoting tumor growth. Herein, we review tumor telomerase biology that may affect the efficacy of therapeutic vaccination and provide insights on optimal vaccine design and treatment combinations. Tumor types possessing mechanisms of increased telomerase expression combined with an immune permissive tumor microenvironment are expected to increase the therapeutic potential of telomerase-targeting cancer vaccines. Regardless, rational treatment combinations, such as checkpoint inhibitors, are likely necessary to bring out the true clinical potential of TCVs.

Targeting KRAS mutations with HLA class II-restricted TCRs for the treatment of solid tumors

T-cell receptor (TCR) redirected T cells are considered as the next generation of care for the treatment of numerous solid tumors. KRAS mutations are driver neoantigens that are expressed in over 25% of all cancers and are thus regarded as ideal targets for Adoptive Cell Therapy (ACT). We have isolated four KRAS-specific TCRs from a long-term surviving pancreatic cancer patient vaccinated with a mix of mutated KRAS peptides. The sequence of these TCRs could be identified and expressed in primary cells. We demonstrated stable expression of all TCRs as well as target-specific functionality when expressing T cells were co-incubated with target cells presenting KRAS peptides. In addition, these TCRs were all partially co-receptor independent since they were functional in both CD4 and CD8 T cells, thus indicating high affinity. Interestingly, we observed that certain TCRs were able to recognize several KRAS mutations in complex with their cognate Human leukocyte antigen (HLA), suggesting that, here, the point mutations were less important for the HLA binding and TCR recognition, whereas others were single-mutation restricted. Finally, we demonstrated that these peptides were indeed processed and presented, since HLA-matched antigen presenting cells exogenously loaded with KRAS proteins were recognized by TCR-transduced T cells. Taken together, our data demonstrate that KRAS mutations are immunogenic for CD4 T cells and are interesting targets for TCR-based cancer immunotherapy.

Combining a Universal Telomerase Based Cancer Vaccine With Ipilimumab in Patients With Metastatic Melanoma - Five-Year Follow Up of a Phase I/IIa Trial

Background

Ipilimumab improves survival for patients with metastatic malignant melanoma. Combining a therapeutic cancer vaccine with ipilimumab may increase efficacy by providing enhanced anti-tumor immune responses. UV1 consists of three synthetic long peptides from human telomerase reverse transcriptase (hTERT). These peptides comprise epitopes recognized by T cells from cancer patients experiencing long-term survival following treatment with a first-generation hTERT vaccine, and generate long-lasting immune responses in cancer patients when used as monotherapy. The objective of this trial was to investigate the safety and efficacy of combining UV1 with ipilimumab in metastatic melanoma.

Patients and Methods

In this phase I/IIa, single center trial [NCT02275416], patients with metastatic melanoma received repeated UV1 vaccinations, with GM-CSF as an adjuvant, in combination with ipilimumab. Patients were evaluated for safety, efficacy and immune response. Immune responses against vaccine peptides were monitored in peripheral blood by measuring antigen-specific proliferation and IFN-γ production.

Results

Twelve patients were recruited. Adverse events were mainly diarrhea, injection site reaction, pruritus, rash, nausea and fatigue. Ten patients showed a Th1 immune response to UV1 peptides, occurring early and after few vaccinations. Three patients obtained a partial response and one patient a complete response. Overall survival was 50% at 5 years.

Conclusion

Treatment was well tolerated. The rapid expansion of UV1-specific Th1 cells in the majority of patients indicates synergy between UV1 vaccine and CTLA-4 blockade. This may have translated into clinical benefit, encouraging the combination of UV1 vaccination with standard of care treatment regimes containing ipilimumab/CTLA-4 blocking antibodies.

Telomerase-based Cancer Therapeutics: A Review on their Clinical Trials

Telomeres are protective chromosomal ends that shield the chromosomes from DNA damage, exonucleolytic degradation, recombination, and end-to-end fusion. Telomerase is a ribonucleoprotein that adds TTAGGG tandem repeats to the telomeric ends. It has been observed that 85 to 90% of human tumors express high levels of telomerase, playing a crucial role in the development of cancers. Interestingly, the telomerase activity is generally absent in normal somatic cells. This selective telomerase expression has driven scientists to develop novel anti-cancer therapeutics with high specificity and potency. Several advancements have been made in this area, which is reflected by the enormous success of the anticancer agent Imetelstat. Since the discovery of Imetelstat, several research groups have contributed to enrich the therapeutic arsenal against cancer. Such contributions include the application of new classes of small molecules, peptides, and hTERT-based immunotherapeutic agents (p540, GV1001, GRNVAC1 or combinations of these such as Vx-001). Many of these therapeutic tools are under different stages of clinical trials and have shown promising outcomes. In this review, we highlight the current status of telomerase-based cancer therapeutics and the outcome of these investigations.

Gene Augmentation and Editing to Improve TCR Engineered T Cell Therapy against Solid Tumors

Recent developments in gene engineering technologies have drastically improved the therapeutic treatment options for cancer patients. The use of effective chimeric antigen receptor T (CAR-T) cells and recombinant T cell receptor engineered T (rTCR-T) cells has entered the clinic for treatment of hematological malignancies with promising results. However, further fine-tuning, to improve functionality and safety, is necessary to apply these strategies for the treatment of solid tumors. The immunosuppressive microenvironment, the surrounding stroma, and the tumor heterogeneity often results in poor T cell reactivity, functionality, and a diminished infiltration rates, hampering the efficacy of the treatment. The focus of this review is on recent advances in rTCR-T cell therapy, to improve both functionality and safety, for potential treatment of solid tumors and provides an overview of ongoing clinical trials. Besides selection of the appropriate tumor associated antigen, efficient delivery of an optimized recombinant TCR transgene into the T cells, in combination with gene editing techniques eliminating the endogenous TCR expression and disrupting specific inhibitory pathways could improve adoptively transferred T cells. Armoring the rTCR-T cells with specific cytokines and/or chemokines and their receptors, or targeting the tumor stroma, can increase the infiltration rate of the immune cells within the solid tumors. On the other hand, clinical “off-tumor/on-target” toxicities are still a major potential risk and can lead to severe adverse events. Incorporation of safety switches in rTCR-T cells can guarantee additional safety. Recent clinical trials provide encouraging data and emphasize the relevance of gene therapy and gene editing tools for potential treatment of solid tumors.

Long-Term Outcomes of a Phase I Study With UV1, a Second Generation Telomerase Based Vaccine, in Patients With Advanced Non-Small Cell Lung Cancer

Human telomerase reverse transcriptase (hTERT) is a target antigen for cancer immunotherapy in patients with non-small cell lung cancer (NSCLC). We have tested a novel hTERT vaccine, UV1, designed to give high population coverage. UV1 is composed of three synthetic long peptides containing multiple epitopes identified by epitope spreading data from long-term survivors from previous hTERT vaccination trials. Eighteen non-HLA-typed patients with stage III/IV NSCLC with no evidence of progression after prior treatments, were enrolled in a phase I dose-escalation study of UV1 vaccination with GM-CSF as adjuvant, evaluating safety, immune response, and long-term clinical outcome. Treatment with UV1 was well tolerated with no serious adverse events observed. Seventeen patients were evaluable for tumor response; 15 patients had stable disease as best response. The median progression free survival (PFS) was 10.7 months, and the median overall survival (OS) was 28.2 months. The OS at 4 years was 39% (7/18). Five patients are alive (median survival 5.6 years), and none of these are known to have received checkpoint therapy after vaccination. UV1 induced specific T-cell responses in the majority (67%) of patients. Immune responses were dynamic and long lasting. Both immune response (IR) and OS were dose related. More patients in the highest UV1 dosage group (700 μg) developed IRs compared to the other groups, and the IRs were stronger and occurred earlier. Patients in this group had a 4-year OS of 83%. The safety and clinical outcome data favor 700 μg as the preferred UV1 dose in this patient population. These results provide a rationale for further clinical studies in NSCLC with UV1 vaccination in combination with immune checkpoint blockade.

Clinical Trial Registration

https://www.clinicaltrials.gov, identifier NCT0178909.

Targeting Telomerase with an HLA Class II-Restricted TCR for Cancer Immunotherapy

T cell receptor (TCR)-engineered T cell therapy is a promising cancer treatment approach. Human telomerase reverse transcriptase (hTERT) is overexpressed in the majority of tumors and a potential target for adoptive cell therapy. We isolated a novel hTERT-specific TCR sequence, named Radium-4, from a clinically responding pancreatic cancer patient vaccinated with a long hTERT peptide. Radium-4 TCR-redirected primary CD4⁺ and CD8⁺ T cells demonstrated in vitro efficacy, producing inflammatory cytokines and killing hTERT⁺ melanoma cells in both 2D and 3D settings, as well as malignant, patient-derived ascites cells. Importantly, T cells expressing Radium-4 TCR displayed no toxicity against bone marrow stem cells or mature hematopoietic cells. Notably, Radium-4 TCR⁺ T cells also significantly reduced tumor growth and improved survival in a xenograft mouse model. Since hTERT is a universal cancer antigen, and the very frequently expressed HLA class II molecules presenting the hTERT peptide to this TCR provide a very high (>75%) population coverage, this TCR represents an attractive candidate for immunotherapy of solid tumors.

Anti-cancer Immunotherapies Targeting Telomerase

Telomerase is a reverse transcriptase that maintains telomeres length, compensating for the attrition of chromosomal ends that occurs during each replication cycle. Telomerase is expressed in germ cells and stem cells, whereas it is virtually undetectable in adult somatic cells. On the other hand, telomerase is broadly expressed in the majority of human tumors playing a crucial role in the replicative behavior and immortality of cancer cells. Several studies have demonstrated that telomerase-derived peptides are able to bind to HLA (human leukocyte antigen) class I and class II molecules and effectively activate both CD8⁺ and CD4⁺ T cells subsets. Due to its broad and selective expression in cancer cells and its significant immunogenicity, telomerase is considered an ideal universal tumor-associated antigen, and consequently, a very attractive target for anti-cancer immunotherapy. To date, different telomerase targeting immunotherapies have been studied in pre-clinical and clinical settings, these approaches include peptide vaccination and cell-based vaccination. The objective of this review paper is to discuss the role of human telomerase in cancer immunotherapy analyzing recent developments and future perspectives in this field.

Role of Telomeres and Telomeric Proteins in Human Malignancies and Their Therapeutic Potential

Telomeres are the ends of linear chromosomes comprised of repetitive nucleotide sequences in humans. Telomeres preserve chromosomal stability and genomic integrity. Telomere length shortens with every cell division in somatic cells, eventually resulting in replicative senescence once telomere length becomes critically short. Telomere shortening can be overcome by telomerase enzyme activity that is undetectable in somatic cells, while being active in germline cells, stem cells, and immune cells. Telomeres are bound by a shelterin complex that regulates telomere lengthening as well as protects them from being identified as DNA damage sites. Telomeres are transcribed by RNA polymerase II, and generate a long noncoding RNA called telomeric repeat-containing RNA (TERRA), which plays a key role in regulating subtelomeric gene expression. Replicative immortality and genome instability are hallmarks of cancer and to attain them cancer cells exploit telomere maintenance and telomere protection mechanisms. Thus, understanding the role of telomeres and their associated proteins in cancer initiation, progression and treatment is very important. The present review highlights the critical role of various telomeric components with recently established functions in cancer. Further, current strategies to target various telomeric components including human telomerase reverse transcriptase (hTERT) as a therapeutic approach in human malignancies are discussed.

The Role of Antigen Spreading in the Efficacy of Immunotherapies

The introduction and the unexpected efficacy of checkpoint inhibitors (CPI) and more recently of chimeric antigen receptor T cells (CAR T-cells) in the treatment of malignant diseases boosted the efforts in the development and clinical application of immunotherapeutic approaches. However, the definition of predictive factors associated with clinical responses as well as the identification of underlying mechanisms that promote the therapeutic efficacy remain to be determined. Starting from the first immunotherapeutic trials, it became evident that vaccine-induced tumor-specific T cells or the adoptive transfer of ex vivo-expanded T lymphocytes can recognize and eliminate malignant cells leading to long-lasting remissions in some patients. In addition, a phenomenon called epitope spreading, which was observed in responding patients, seemed to increase the efficiency possibly representing an important predictive factor. This review will focus on experimental and clinical evidence for the induction of epitope spreading and its role in the maintenance of an efficient antitumor immune response in cancer immunotherapy.

Long-term surviving cancer patients as a source of therapeutic TCR

We have established a platform for the isolation of tumour-specific TCR from T cells of patients who experienced clinical benefit from cancer vaccination. In this review we will present the rationale behind this strategy and discuss the advantages of working with “natural” wild type TCRs. Indeed, the general trend in the field has been to use various modifications to enhance the affinity of such therapeutic TCRs. This was done to obtain stronger T cell responses, often at the cost of safety. We further describe antigen targets and recent in vitro and in vivo results obtained to validate them. We finally discuss the use of MHC class II-restricted TCR in immunotherapy. Typically cellular anti-tumour immune responses have been attributed to CD8 T cells; however, we isolated mainly CD4 T cells. Importantly, these MHC class II-restricted TCRs have the potential to induce broad, long lasting immune responses that enable cancer control. The use of CD4 T cell-derived TCRs for adoptive immunotherapy has so far been limited and we will here discuss their therapeutic potential.

A First-in-Human Phase I Study of INVAC-1, an Optimized Human Telomerase DNA Vaccine in Patients with Advanced Solid Tumors

PURPOSE

Human telomerase reverse transcriptase (hTERT) is highly expressed in >85% of human tumors and is thus considered as a good tumor-associated antigen candidate for vaccine development. We conducted a phase I study to investigate the safety, tolerability, clinical response, and immunogenicity of INVAC-1, a DNA plasmid encoding a modified hTERT protein in patients with relapsed or refractory solid tumors.

PATIENTS AND METHODS

INVAC-1 was either administered by intradermal route followed by electroporation or by Tropis, a needle-free injection system. Safety and tolerability were monitored by clinical and laboratory assessments. Progression-free survival and overall survival were reported using Kaplan-Meier survival analysis. Immunogenicity was studied by ELISpot, Luminex, and Flow Cytometry.

RESULTS

Twenty-six patients were treated with INVAC-1 administered at three dose levels (100, 400, and 800 μg). Vaccination was well tolerated and no dose-limiting toxicity was reported. One treatment-related grade 3 SAE was reported. Fifty-eight percent of patients experienced disease stabilization. PFS was 2.7 months, median OS was 15 months, and 1-year survival was reached for 65% of patients. INVAC-1 vaccination stimulated specific anti-hTERT CD4 T-cell response as well as cytotoxic CD8 T-cell response. No evidence of peripheral vaccine-induced immunosuppression was observed.

CONCLUSIONS

INVAC-1 vaccination was safe, well tolerated, and immunogenic when administered intradermally at the three tested doses in patients with relapsed or refractory cancers. Disease stabilization was observed for the majority of patients (58%) during the treatment period and beyond.See related commentary by Slingluff Jr, p. 529.

High-throughput Screening of Human Tumor Antigen-specific CD4 T Cells, Including Neoantigen-reactive T Cells

PURPOSE

Characterization of tumor antigen-specific CD4 T-cell responses in healthy donors and malignant melanoma patients using an in vitro amplified T-cell library screening procedure.

PATIENTS AND METHODS

A high-throughput, human leukocyte antigen (HLA)-independent approach was used to estimate at unprecedented high sensitivity level precursor frequencies of tumor antigen- and neoantigen-specific CD4 T cells in healthy donors and patients with cancer. Frequency estimation was combined with isolation and functional characterization of identified tumor-reactive CD4 T-cell clones.

RESULTS

In healthy donors, we report frequencies of naïve tumor-associated antigen (TAA)-specific CD4 T cells comparable with those of CD4 T cells specific for infectious agents (Tetanus toxoid). Interestingly, we also identified low, but consistent numbers of memory CD4 T cells specific for several TAAs. In patients with melanoma, low frequencies of circulating TAA-specific CD4 T cells were detected that increased after peptide-based immunotherapy. Such antitumor TAA-specific CD4 T-cell responses were also detectable within the tumor-infiltrated tissues. TAA-specific CD4 T cells in patients displayed a highly polyfunctional state, with partial skewing to Type-2 polarization. Finally, we report the applicability of this approach to the detection and amplification of neoantigen-specific CD4 T cells.

CONCLUSIONS

This simple, noninvasive, high-throughput screening of tumor- and neoantigen-specific CD4 T cells requires little biologic material, is HLA class II independent and allows the concomitant screening for a large number of tumor antigens of interest, including neoantigens. This approach will facilitate the immunomonitoring of preexisting and therapy-induced CD4 T-cell responses, and accelerate the development of CD4 T-cell-based therapies.

Stilbene Compounds Inhibit Tumor Growth by the Induction of Cellular Senescence and the Inhibition of Telomerase Activity

Cellular senescence is a state of cell cycle arrest characterized by a distinct morphology, gene expression pattern, and secretory phenotype. It can be triggered by multiple mechanisms, including those involved in telomere shortening, the accumulation of DNA damage, epigenetic pathways, and the senescence-associated secretory phenotype (SASP), and so on. In current cancer therapy, cellular senescence has emerged as a potent tumor suppression mechanism that restrains proliferation in cells at risk for malignant transformation. Therefore, compounds that stimulate the growth inhibition effects of senescence while limiting its detrimental effects are believed to have great clinical potential. In this review article, we first review the current knowledge of the pro- and antitumorigeneic functions of senescence and summarize the key roles of telomerase in the regulation of senescence in tumors. Second, we review the current literature regarding the anticancer effects of stilbene compounds that are mediated by the targeting of telomerase and cell senescence. Finally, we provide future perspectives on the clinical utilization of stilbene compounds, especially resveratrol and pterostilbene, as novel cancer therapeutic remedies. We conclude and propose that stilbene compounds may induce senescence and may potentially be used as the therapeutic or adjuvant agents for cancers with high telomerase activity.

Telomerase-Targeted Cancer Immunotherapy

Telomerase, an enzyme responsible for the synthesis of telomeres, is activated in many cancer cells and is involved in the maintenance of telomeres. The activity of telomerase allows cancer cells to replicate and proliferate in an uncontrolled manner, to infiltrate tissue, and to metastasize to distant organs. Studies to date have examined the mechanisms involved in the survival of cancer cells as targets for cancer therapeutics. These efforts led to the development of telomerase inhibitors as anticancer drugs, drugs targeting telomere DNA, viral vectors carrying a promoter for human telomerase reverse transcriptase (hTERT) genome, and immunotherapy targeting hTERT. Among these novel therapeutics, this review focuses on immunotherapy targeting hTERT and discusses the current evidence and future perspectives.

Transient redirection of T cells for adoptive cell therapy with telomerase-specific T helper cell receptors isolated from long term survivors after cancer vaccination

Adoptive cell therapy (ACT) with retargeted T cells has produced remarkable clinical responses against cancer, but also serious toxicity. Telomerase is overexpressed in most cancers, but also expressed in some normal cells, raising safety concerns. We hypothesize that ACT with T-helper cell receptors may overcome tumour tolerance, mobilize host immune cells and induce epitope spreading, with limited toxicity. From long term survivors after cancer vaccination, we have isolated telomerase-specific T cell receptors (TCRs) from T-helper cells. Herein, we report the development of transient retargeting of T cells with mRNA-based TCRs. This strategy allows for safer clinical testing and meaningful dose escalation. DP4 is the most common HLA molecule. We cloned two telomerase-specific, DP4-restricted TCRs into the mRNA expression vector pCIpA102, together with the sorter/marker/suicide gene RQR8. Donor T cells were electroporated with mRNA encoding TCR_RQR8. The results showed that both TCR_RQR8 constructs were expressed in >90% of T cells. The transfected T cells specifically recognized the relevant peptide, as well as naturally processed epitopes from a 177aa telomerase protein fragment, and remained functional for six days. A polyfunctional and Th1-like cytokine profile was observed. The TCRs were functional in both CD4+and CD8+recipient T cells, even though DP4-restricted. The findings demonstrate that the cloned TCRs confer recipient T cells with the desired telomerase-specificity and functionality. Preclinical experiments may provide limited information on the efficacy and toxicity of T-helper TCRs, as these mobilize the host immune system. We therefore intend to use the mRNA-based TCRs for a first-in-man trial.

The expression of MHC class II molecules on murine breast tumors delays T-cell exhaustion, expands the T-cell repertoire, and slows tumor growth

The expression of MHC class II molecules (MHCII) on tumor cells correlates with survival and responsiveness to immunotherapy. However, the mechanisms underlying these observations are poorly defined. Using a murine breast tumor line, we showed that MHCII-expressing tumors grew more slowly than controls and recruited more functional CD4⁺ and CD8⁺ T cells. In addition, MHCII-expressing tumors contained more TCR clonotypes expanded to a larger degree than control tumors. Functional CD8⁺ T cells in tumors depended on CD4⁺ T cells. However, both CD4⁺ and CD8⁺ T cells eventually became exhausted, even in MHCII-expressing tumors. Treatment with anti-CTLA4, but not anti-PD-1 or anti-TIM-3, promoted complete eradication of MHCII-expressing tumors. These results suggest tumor cell expression of MHCII facilitates the local activation of CD4⁺ T cells, indirectly helps the activation and expansion of CD8⁺ T cells, and, in combination with the appropriate checkpoint inhibitor, promotes tumor regression.

Correlates of immune and clinical activity of novel cancer vaccines

Cancer vaccines are solely meant to amplify the pool of type 1 cytokine oriented CD4+ and CD8+ T cells that recognize tumor antigen and ultimately foster control and destruction of a growing tumor. They are not designed to deal with all aspects of immune ignorance, exclusion, suppression and escape that are generally in place in patients with cancer and may prevent the T cells to enter the tumor or to exert their effector function. This simple fact prompted for a reappraisal of the many recent trials in which therapeutic cancer vaccines have been examined as monotherapy. In this review, I focus on trials examining therapeutic cancer vaccines at different stages of existing disease. The analysis of vaccine-induced immune responses and clinical activity of therapeutic cancer vaccines revealed four levels of evidence for vaccine efficacy. The lowest levels, reflect the many trials in which the strength of the tumor-reactive T cell response of vaccinated patients is associated with better clinical outcome or change in tumor marker. The highest levels indicate occasional regressions of tumors and metastases after vaccination or reflect a stronger clinical impact of vaccine in a randomized trial. A whole series of trials in which vaccine-induced tumor immunity correlates with the clinical impact of cancer vaccines in premalignant diseases, settings of low tumor burden or tumor regressions in patients with cancer, form an attest to the fact that cancer vaccines work. While the current number of true clinical responders in each cancer trial is too low for firm conclusions on immune correlates of clinical reactivity in cancer, extrapolation of the results from vaccinated patients with pre-cancers suggest a requirement of broad type 1 T cell reactivity.

Targeting Head and Neck Cancer by Vaccination

Head and neck cancer (HNC) is a heterogeneous group of squamous cell cancers that affect the oral cavity, pharynx, and larynx. Worldwide, it is the sixth most common cancer but in parts of Southern and South-East Asia, HNC is one of the most common cancers. A significant proportion of HNC is driven by human papillomavirus (HPV) infection, whereas HPV-independent HNC is associated with alcohol, smoking, and smokeless tobacco consumption. Here, we review the past and present experience of targeting HNC with vaccination focusing on HPV-derived antigens as well as non-viral antigens for HPV-negative HNC. Novel therapeutic approaches for HNC will focus not only on effective vaccine platforms but will also target the stroma-rich immunosuppressive microenvironment found in those tumours.

Bladder cancer-associated cancer-testis antigen-derived long peptides encompassing both CTL and promiscuous HLA class II-restricted Th cell epitopes induced CD4+ T cells expressing converged T-cell receptor genes in vitro

DEP domain containing 1 (DEPDC1) and M-phase phosphoprotein 1 (MPHOSPH1) are human cancer testis antigens that are frequently overexpressed in urinary bladder cancer. In a phase I/II clinical trial, a DEPDC1- and MPHOSPH1-derived short peptide vaccine demonstrated promising efficacy in preventing bladder cancer recurrence. Here, we aimed to identify long peptides (LPs) derived from DEPDC1 and MPHOSPH1 that induced both T-helper (Th) cells and tumor-reactive cytotoxic T lymphocytes (CTLs). Stimulation of peripheral blood mononuclear cells (PBMCs) from healthy donors with the synthetic DEPDC1- and MPHOSPH1-LPs predicted to bind to promiscuous human leukocyte antigen (HLA) class II molecules by a computer algorithm induced specific CD4⁺ T cells as revealed by interferon-γ enzyme-linked immunospot assays. Three of six LPs encompassed HLA-A2- or -A24-restricted CTL epitopes or both, and all six LPs stimulated DEPDC1- or MPHOSPH1-specific Th cells restricted by promiscuous and frequently observed HLA class II molecules in the Japanese population. Some LPs are naturally processed from the proteins in DCs, and the capacity of these LPs to cross-prime CTLs was confirmed in vivo using HLA-A2 or -A24 transgenic mice. The LP-specific and HLA class II-restricted T-cell responses were also observed in PBMCs from patients with bladder cancer. Repeated stimulation of PBMCs with DEPDC1-LPs and MPHOSPH1-LPs yielded clonal Th cells expressing specific T-cell receptor (TCR)-α and β genes. These DEPDC1- or MPHOSPH1-derived LPs may have applications in immunotherapy in patients with bladder cancer, and the TCR genes identified may be useful for monitoring of Th cells specific to LPs in vivo.

Protective effects of GV1001 on myocardial ischemia‑reperfusion injury

The potential cardioprotective effects of the novel vaccine peptide GV1001 were evaluated in myocardial ischemia‑reperfusion injury induced rat models. GV1001 is a human telomerase reverse transcriptase derived peptide, which has been reported to possess both anti‑tumor and anti‑inflammatory effects. The normal saline (control group) and various concentrations (0.001‑10 mg/kg) of GV1001 were administered directly to the right ventricle anterior wall before induction of ischemia. The was induced by Tightening the snare around the left anterior descending coronary artery for 40 min, before releasing the snare for 10 min induced the myocardial ischemia‑reperfusion injury and was conducted in Sprague‑Dawley rats. The area at risk, histology, apoptotic cells, neutrophils and inflammatory cytokines were analyzed from the excised heart tissue following myocardial ischemia‑reperfusion injury. The area at risk was protected by concentrations of GV1001 equal to or higher than 0.01 mg/kg. At 0.1 mg/kg and higher concentrations of GV1001, the hemorrhage in the heart was attenuated, while severe congestion was reported in the control group. Apoptotic cells, myeloperoxidase activity and inflammatory cytokines [tumor necrosis factor (TNF)‑α and interleukin (IL)‑6] revealed decreased levels in a dose‑dependent manner with respect to GV1001 concentration. The group treated with 10 mg/kg GV1001 demonstrated 59.73% apoptotic cells (P<0.001), 48.14% neutrophil contents (P<0.001), 55.63% TNF‑α (P<0.01) and 42.35% IL‑6 (P<0.01) levels, compared with the control group. The novel vaccine peptide GV1001 provided protective effects on myocardial ischemia‑reperfusion injury and, therefore, it should be considered as an alternative potential anti‑inflammatory agent for myocardial ischemia‑reperfusion injury.

Viral based vaccine TG4010 induces broadening of specific immune response and improves outcome in advanced NSCLC

BACKGROUND

Advanced non-small cell lung cancer patients receiving TG4010, a therapeutic viral vaccine encoding human Mucin 1 and interleukin-2 in addition to standard chemotherapy, displayed longer overall survival in comparison to that of patients treated with standard chemotherapy alone. Our study intended to establish the association between overall survival and vaccine-induced T cell responses against tumor associated antigens (TAA) targeted by the vaccine.

METHOD

The TIME trial was a placebo-controlled, randomized phase II study aimed at assessing efficacy of TG4010 with chemotherapy in NSCLC. 78 patients from the TIME study carrying the HLA-A02*01 haplotype were analyzed using combinatorial encoding of MHC multimers to detect low frequencies of cellular immune responses to TG4010 and other unrelated TAA.

RESULTS

We report that improvement of survival under TG4010 treatment correlated with development of T cell responses against MUC1. Interestingly, responses against MUC1 were associated with broadening of CD8 responses against non-targeted TAA, thus demonstrating induction of epitope spreading.

CONCLUSION

Our results support the causality of specific T-cell response in improved survival in NSCLC. Additionally, vaccine induced epitope spreading to other TAA participates to the enrichment of the diversity of the anti-tumor response. Hence, TG4010 appears as a useful therapeutic option to maximize response rate and clinical benefit in association with other targeted immuno-modulators.

TRIAL REGISTRATION

Registered on ClinicalTrials.gov under identifier NCT01383148 on June 23rd, 2011.

Safety, immune and clinical responses in metastatic melanoma patients vaccinated with a long peptide derived from indoleamine 2,3-dioxygenase in combination with ipilimumab

BACKGROUND AIM

Indoleamine 2,3-dioxygenase (IDO) is an emerging new target in cancer therapy that can be targeted with active immunotherapy (e.g. through peptide vaccination). Furthermore, IDO has been identified as a key mechanism underlying resistance to treatment with the checkpoint blocking antibody ipilimumab (ipi).

METHODS

Ten patients with metastatic melanoma participated in a phase I first-in-human clinical study assessing safety of combining ipi with a 21-mer synthetic peptide vaccine from IDO denoted IDOlong. Secondary and tertiary end points included vaccine and clinical response.

RESULTS

Treatment was generally safe and well tolerated. Vaccine related adverse reactions included grade I and II erythema, oedema and pruritus at the vaccination site, which were manageable with mild topical corticosteroids. One patient developed presumed ipi-induced colitis. It initially responded to high-dose parenteral corticosteroids but later relapsed while the patient was admitted to a local hospital, where he died after receiving suboptimal therapy. Vaccine-specific T-cell responses were detectable ex vivo in three patients. At first evaluation, five of the 10 treated patients were in stable disease, one of whom had an unconfirmed partial response.

CONCLUSIONS

Treatment with IDOlong synthetic peptide vaccine in combination with ipi was generally safe and without augmented toxicity. The vaccine induced readily detectable T-cell responses in a subset of patients. Treatment showed signs of clinical activity, although not exceeding efficacy of ipi alone. Results should be confirmed in a larger study.

Phase I/IIa clinical trial of a novel hTERT peptide vaccine in men with metastatic hormone-naive prostate cancer

In newly diagnosed metastatic hormone-naive prostate cancer (mPC), telomerase-based immunotherapy with the novel hTERT peptide vaccine UV1 can induce immune responses with potential clinical benefit. This phase I dose escalation study of UV1 evaluated safety, immune response, effects on prostate-specific antigen (PSA) levels, and preliminary clinical outcome. Twenty-two patients with newly diagnosed metastatic hormone-naïve PC (mPC) were enrolled; all had started androgen deprivation therapy and had no visceral metastases. Bone metastases were present in 17 (77%) patients and 16 (73%) patients had affected lymph nodes. Three dose levels of UV1 were given as intradermal injections combined with GM-CSF (Leukine®). Twenty-one patients in the intention-to-treat population (95%) received conformal radiotherapy. Adverse events reported were predominantly grade 1, most frequently injection site pruritus (86.4%). Serious adverse events considered possibly related to UV1 and/or GM-CSF included anaphylactic reaction in two patients and thrombocytopenia in one patient. Immune responses against UV1 peptides were confirmed in 18/21 evaluable patients (85.7%), PSA declined to <0.5 ng/mL in 14 (64%) patients and in ten patients (45%) no evidence of persisting tumour was seen on MRI in the prostatic gland. At the end of the nine-month reporting period for the study, 17 patients had clinically stable disease. Treatment with UV1 and GM-CSF gave few adverse events and induced specific immune responses in a large proportion of patients unselected for HLA type. The intermediate dose of 0.3 mg UV1 resulted in the highest proportion of, and most rapid UV1-specific immune responses with an acceptable safety profile. These results warrant further clinical studies in mPC.