Assessment of Safety and Prophylactic Efficacy of the EpiVacCorona Peptide Vaccine for COVID-19 Prevention (Phase III).

The State Research Center of Virology and Biotechnology "VECTOR" of the Federal Service for the Oversight of Consumer Protection and Welfare (Rospotrebnadzor) has developed the peptide-based EpiVacCorona vaccine, which is the first synthetic peptide-based antiviral vaccine for mass immunization in international vaccinology. An early clinical trial (Phase I-II) demonstrated that the EpiVacCorona vaccine is a safe product. The "Multicenter double-blind, placebo-controlled, comparative, randomized trial to assess the tolerability, safety, immunogenicity and prophylactic efficacy of the EpiVacCorona COVID-19 vaccine based on peptide antigens in 3000 volunteers aged 18 years and older" was performed regarding vaccine safety. The key objectives of the study were to evaluate the safety and prophylactic efficacy of the two-dose EpiVacCorona vaccine administered via the intramuscular route. The results of the clinical study (Phase III) demonstrated the safety of the EpiVacCorona vaccine. Vaccine administration was accompanied by mild local reactions in ≤27% of cases and mild systemic reactions in ≤14% of cases. The prophylactic efficacy of the EpiVacCorona COVID-19 vaccine after the completion of the vaccination series was 82.5% (CI95 = 75.3-87.6%). The high safety and efficacy of the vaccine give grounds for recommending this vaccine for regular seasonal prevention of COVID-19 as a safe and effective medicinal product.

Precise Epitope Organization with Self‐adjuvant Framework Nucleic Acid for Efficient COVID‐19 Peptide Vaccine Construction

Peptide vaccines have advantages in easy fabrication and high safety, but their effectiveness is hampered by the poor immunogenicity of the epitopes themselves. Herein, we constructed a series of framework nucleic acids (FNAs) with regulated rigidity and size to precisely organize epitopes in order to reveal the influence of epitope spacing and carrier rigidity on the efficiency of peptide vaccines. We found that assembling epitopes on rigid tetrahedral FNAs (tFNAs) with the appropriate size could efficiently enhance their immunogenicity. Further, by integrating epitopes from SARS‐CoV‐2 on preferred tFNAs, we constructed a COVID‐19 peptide vaccine which could induce high titers of IgG against the receptor binding domain (RBD) of SARS‐CoV‐2 spike protein and increase the ratio of memory B and T cells in mice. Considering the good biocompatibility of tFNAs, our research provides a new idea for developing efficient peptide vaccines against viruses and possibly other diseases.

Development of a New Epitope Immunogenic Structure Based on the Coronavirus Membrane Glycoprotein M Using Immunoinformatics Tools

Backgrounds: Although conventional therapies have played an essential role in the treatment of many diseases, emerging diseases require new treatment methods with less complications. Therefore, it is important to develop an effective vaccine for infections caused by the coronavirus to prevent mortality and create immunity the community. Material(s) and Method(s): In this research bioinformatics tools were used to design a vaccine against the M membrane protein of SARS-CoV-2. A total of 27 epitopes confined to B cells and MHC I and II alleles were structurally constructed in M protein for immune stimulation and antibody recognition which were used in the construction of a chimeric peptide vaccine. Finding(s): The vaccine was predicted to be a stable, antigenic, and non-allergenic compound. TRL5/vaccine complex analysis and docking simulation indicated a sufficiently stable binding with appropriated receptor activation. The immune response simulation following hypothetical immunization indicated the potential of this vaccine to stimulate the production of active and memory B cells, CD8 + T and, CD4 + T cells, and effective immunological responses induced by Th2 and Th1. Conclusion(s): The analysis of in-silico processes showed that the vaccine structure induced high antigenicity and good cellular immunity in the host body and stimulates various immune receptors such as TLR5, MHC I, and MHC II. Vaccine function was also associated with an increase in IgM and IgG antibodies and a set of Th1 and Th2 cytokines. But the final confirmation of the effectiveness of the designed vaccine requires clinical processes.Copyright © 2022, TMU Press.

A novel mutation-proof, next-generation vaccine to fight against upcoming SARS-CoV-2 variants and subvariants, designed through AI enabled approaches and tools, along with the machine learning based immune simulation: A vaccine breakthrough.

Emerging SARS-CoV-2 variants and subvariants are great concerns for their significant mutations, which are also responsible for vaccine escape. Therefore, the study was undertaken to develop a mutation-proof, next-generation vaccine to protect against all upcoming SARS-CoV-2 variants. We used advanced computational and bioinformatics approaches to develop a multi-epitopic vaccine, especially the AI model for mutation selection and machine learning (ML) strategies for immune simulation. AI enabled and the top-ranked antigenic selection approaches were used to select nine mutations from 835 RBD mutations. We selected twelve common antigenic B cell and T cell epitopes (CTL and HTL) containing the nine RBD mutations and joined them with the adjuvants, PADRE sequence, and suitable linkers. The constructs' binding affinity was confirmed through docking with TLR4/MD2 complex and showed significant binding free energy (-96.67 kcal mol-1) with positive binding affinity. Similarly, the calculated eigenvalue (2.428517e-05) from the NMA of the complex reveals proper molecular motion and superior residues' flexibility. Immune simulation shows that the candidate can induce a robust immune response. The designed mutation-proof, multi-epitopic vaccine could be a remarkable candidate for upcoming SARS-CoV-2 variants and subvariants. The study method might guide researchers in developing AI-ML and immunoinformatics-based vaccines for infectious disease.

Harnessing immunoinformatics for developing a multiple-epitope peptide-based vaccination approach against SARS-CoV-2 spike protein.

COVID-19 has spread to over 200 countries with variable severity and mortality rates. Computational analysis is a valuable tool for developing B-cell and T-cell epitope-based vaccines. In this study, by harnessing immunoinformatics tools, we designed a multiple-epitope vaccine to protect against COVID-19. The candidate epitopes were designed from highly conserved regions of the SARS-CoV-2 spike (S) glycoprotein. The consensus amino acids sequence of ten SARS-CoV-2 variants including Gamma, Beta, Epsilon, Delta, Alpha, Kappa, Iota, Lambda, Mu, and Omicron was involved. Applying the multiple sequence alignment plugin and the antigenic prediction tools of Geneious prime 2021, ten predicted variants were identified and consensus S-protein sequences were used to predict the antigenic part. According to ElliPro analysis of S-protein B-cell prediction, we explored 22 continuous linear epitopes with high scores ranging from 0.879 to 0.522. First, we reported five promising epitopes: BE1 1115-1192, BE2 481-563, BE3 287-313, BE4 62-75, and BE5 112-131 with antigenicity scores of 0.879, 0.86, 0.813, 0.779, and 0.765, respectively, while only nine discontinuous epitopes scored between 0.971 and 0.511. Next, we identified 194 Major Histocompatibility Complex (MHC) - I and 156 MHC - II epitopes with antigenic characteristics. These spike-specific peptide-epitopes with characteristically high immunogenic and antigenic scores have the potential as a SARS-CoV-2 multiple-epitope peptide-based vaccination strategy. Nevertheless, further experimental investigations are needed to test for the vaccine efficacy and efficiency.

An Integrated In Silico Approach to Develop Epitope-Based Peptide Vaccine Against SARS-CoV-2

Background: SARS-CoV-2 has been a topic of discussion ever since the beginning of 2020. Every country is trying all possible steps to combat the disease ranging from shutting the complete economy of the country to the repurposing of drugs and vaccine development. The rapid data analysis and widespread tools have made bioinformatics capable of giving new insights to deal with the current scenario more efficiently through an emerging field, vaccinomics. Objective(s): The present in silico study was attempted to identify peptide fragments from spike surface glycoprotein of SARS-CoV-2 that can be efficiently used for the development of an epi-tope-based vaccine designing approach. Method(s): The epitopes of B and T-cell are predicted using integrated computational tools. VaxiJen server, NetCTL, and IEDB tools were used to study, analyze, and predict potent T-cell epitopes, their subsequent MHC-I interactions, and B-cell epitopes. The 3D structure prediction of peptides and MHC-I alleles (HLA-C*03:03) was further made using AutoDock4.0. Result(s): Based on result interpretation, the peptide sequence from 1138-1145 amino acid and sequence WTAGAAAYY and YDPLQPEL were obtained as potential B-cell and T-cell epitopes, re-spectively. Conclusion(s): The peptide sequence WTAGAAAYY and the amino acid sequence from 1138-1145 of the spike protein of SARS-CoV-2 can be used as a probable B-cell epitope candidate. Also, the amino acid sequence YDPLQPEL can be used as a potent T-cell epitope. This in silico study will help us identify novel epitope-based peptide vaccine targets in the spike protein of SARS-CoV-2. Further, the in vitro and in vivo study needed to validate the findings.Copyright © 2022 Bentham Science Publishers.

Chemoinformatics and bioinformatics by discrete mathematics and numbers: an adventure from small data to the realm of emerging big data

Currently, we are witnessing the emergence of big data in various fields including the biomedical and natural sciences. The size of chemoinformatics and bioinformatics databases is increasing every day. This gives us both challenges and opportunities. This chapter discusses the mathematical methods used in these fields both for the generation and analysis of such data. It is emphasized that proper use of robust statistical and machine learning methods in the analysis of the available big data may facilitate both hypothesis-driven and discovery-oriented research. © 2023 Elsevier Inc. All rights reserved.

Synthesis of Killer T Cell Epitopes for Peptide-Based Vaccine of SARS-CoV-2

COVID-19 is a current global pandemic, which has prompted many countries to develop ways to deal with it. Peptides have many medicinal and diagnostic benefits, so recently, many researchers have been developing peptide-based vaccines against COVID-19. In peptide-based vaccines, peptides act as specific antigens that will provide a faster immune response because they do not go through the process of cutting proteins in the Major Histocompatibility complex (MHC) antigen-presenting cells (APC) and can be directly presented outside the cells so that they can be recognized by the host killer T cells (CTL). Vaccine development can be accelerated with the help of immunoinformatics to predict specific epitopes to induce CTL. We have predicted the CTL epitope through the immunoinformatic method. This study aims to synthesize candidate CTL epitopes as a candidate for the SARS-CoV-2 vaccine using the SPPS method with the Fmoc/t-Bu strategy. In this study, two CTL epitopes were synthesized through a conventional solid-phase peptide synthesis (SPPS) method, and another CTL epitope was synthesized using a semi-automated peptide synthesizer. The SPPS method is faster because the purification is only carried out at the final stage, while the Fmoc/t-Bu strategy was applied because it provides a mild reaction condition. Both synthetic approaches were compared. The semi-automated peptide synthesizer made the synthesis faster and more efficient due to using an inert gas (N2) during the synthesis. The synthetic peptides were characterized by TOF-ESI-MS. The three peptides showed ion peaks at m/z 1137.5509 (M+H)+, 1064.3468 (M+H)+, and 916.5859 (M+H)+, indicating correct molecular ion peaks for EILDITPCSF, IPIGAGICASY, and FIAGLIAIV, respectively. © 2022 National Information and Documentation Center.

A Synthetic SARS-CoV-2-Derived T-Cell and B-Cell Peptide Cocktail Elicits Full Protection against Lethal Omicron BA.1 Infection in H11-K18-hACE2 Mice.

Emerging variants of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) have been developing the capacity for immune evasion and resistance to existing vaccines and drugs. To address this, development of vaccines against coronavirus disease 2019 (COVID-19) has focused on universality, strong T cell immunity, and rapid production. Synthetic peptide vaccines, which are inexpensive and quick to produce, show low toxicity, and can be selected from the conserved SARS-CoV-2 proteome, are promising candidates. In this study, we evaluated the effectiveness of a synthetic peptide cocktail containing three murine CD4+ T-cell epitopes from the SARS-CoV-2 nonspike proteome and one B-cell epitope from the Omicron BA.1 receptor-binding domain (RBD), along with aluminum phosphate (Al) adjuvant and 5' cytosine-phosphate-guanine 3' oligodeoxynucleotide (CpG-ODN) adjuvant in mice. The peptide cocktail induced good Th1-biased T-cell responses and effective neutralizing-antibody titers against the Omicron BA.1 variant. Additionally, H11-K18-hACE2 transgenic mice were fully protected against lethal challenge with the BA.1 strain, with a 100% survival rate and reduced pulmonary viral load and pathological lesions. Subcutaneous administration was found to be the superior route for synthetic peptide vaccine delivery. Our findings demonstrate the effectiveness of the peptide cocktail in mice, suggesting the feasibility of synthetic peptide vaccines for humans. IMPORTANCE Current vaccines based on production of neutralizing antibodies fail to prevent the infection and transmission of SARS-CoV-2 Omicron and its subvariants. Understanding the critical factors and avoiding the disadvantages of vaccine strategies are essential for developing a safe and effective COVID-19 vaccine, which would include a more effective and durable cellular response, minimal effects of viral mutations, rapid production against emerging variants, and good safety. Peptide-based vaccines are an excellent alternative because they are inexpensive, quick to produce, and very safe. In addition, human leukocyte antigen T-cell epitopes could be targeted at robust T-cell immunity and selected in the conserved region of the SARS-CoV-2 variants. Our study showed that a synthetic SARS-CoV-2-derived peptide cocktail induced full protection against lethal infection with Omicron BA.1 in H11-K18-hACE2 mice for the first time. This could have implications for the development of effective COVID-19 peptide vaccines for humans.

Precise Epitope Organization with Self-adjuvant Framework Nucleic Acid for Efficient COVID-19 Peptide Vaccine Construction.

Peptide vaccines have advantages in easy fabrication and high safety, but their effectiveness is hampered by the poor immunogenicity of the epitopes themselves. Herein, we constructed a series of framework nucleic acids (FNAs) with regulated rigidity and size to precisely organize epitopes in order to reveal the influence of epitope spacing and carrier rigidity on the efficiency of peptide vaccines. We found that assembling epitopes on rigid tetrahedral FNAs (tFNAs) with the appropriate size could efficiently enhance their immunogenicity. Further, by integrating epitopes from SARS-CoV-2 on preferred tFNAs, we constructed a COVID-19 peptide vaccine which could induce high titers of IgG against the receptor binding domain (RBD) of SARS-CoV-2 spike protein and increase the ratio of memory B and T cells in mice. Considering the good biocompatibility of tFNAs, our research provides a new idea for developing efficient peptide vaccines against viruses and possibly other diseases.

Erratum: Enhanced cross-recognition of SARS-CoV-2 Omicron variant by peptide vaccine-induced antibodies.

[This corrects the article DOI: 10.3389/fimmu.2022.1044025.].

Recent trends in next generation immunoinformatics harnessed for universal coronavirus vaccine design.

The ongoing pandemic of coronavirus disease 2019 (COVID-19), caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has globally devastated public health, the economies of many countries and quality of life universally. The recent emergence of immune-escaped variants and scenario of vaccinated individuals being infected has raised the global concerns about the effectiveness of the current available vaccines in transmission control and disease prevention. Given the high rate mutation of SARS-CoV-2, an efficacious vaccine targeting against multiple variants that contains virus-specific epitopes is desperately needed. An immunoinformatics approach is gaining traction in vaccine design and development due to the significant reduction in time and cost of immunogenicity studies and increasing reliability of the generated results. It can underpin the development of novel therapeutic methods and accelerate the design and production of peptide vaccines for infectious diseases. Structural proteins, particularly spike protein (S), along with other proteins have been studied intensively as promising coronavirus vaccine targets. Numbers of promising online immunological databases, tools and web servers have widely been employed for the design and development of next generation COVID-19 vaccines. This review highlights the role of immunoinformatics in identifying immunogenic peptides as potential vaccine targets, involving databases, and prediction and characterization of epitopes which can be harnessed for designing future coronavirus vaccines.

A pan-variant mRNA-LNP T cell vaccine protects HLA transgenic mice from mortality after infection with SARS-CoV-2 Beta.

Licensed COVID-19 vaccines ameliorate viral infection by inducing production of neutralizing antibodies that bind the SARS-CoV-2 Spike protein and inhibit viral cellular entry. However, the clinical effectiveness of these vaccines is transitory as viral variants escape antibody neutralization. Effective vaccines that solely rely upon a T cell response to combat SARS-CoV-2 infection could be transformational because they can utilize highly conserved short pan-variant peptide epitopes, but a mRNA-LNP T cell vaccine has not been shown to provide effective anti-SARS-CoV-2 prophylaxis. Here we show a mRNA-LNP vaccine (MIT-T-COVID) based on highly conserved short peptide epitopes activates CD8+ and CD4+ T cell responses that attenuate morbidity and prevent mortality in HLA-A*02:01 transgenic mice infected with SARS-CoV-2 Beta (B.1.351). We found CD8+ T cells in mice immunized with MIT-T-COVID vaccine significantly increased from 1.1% to 24.0% of total pulmonary nucleated cells prior to and at 7 days post infection (dpi), respectively, indicating dynamic recruitment of circulating specific T cells into the infected lungs. Mice immunized with MIT-T-COVID had 2.8 (2 dpi) and 3.3 (7 dpi) times more lung infiltrating CD8+ T cells than unimmunized mice. Mice immunized with MIT-T-COVID had 17.4 times more lung infiltrating CD4+ T cells than unimmunized mice (7 dpi). The undetectable specific antibody response in MIT-T-COVID-immunized mice demonstrates specific T cell responses alone can effectively attenuate the pathogenesis of SARS-CoV-2 infection. Our results suggest further study is merited for pan-variant T cell vaccines, including for individuals that cannot produce neutralizing antibodies or to help mitigate Long COVID.

Enhanced cross-recognition of SARS-CoV-2 Omicron variant by peptide vaccine-induced antibodies.

Current vaccines against SARS-CoV-2, based on the original Wuhan sequence, induce antibodies with different degrees of cross-recognition of new viral variants of concern. Despite potent responses generated in vaccinated and infected individuals, the Omicron (B.1.1.529) variant causes breakthrough infections, facilitating viral transmission. We previously reported a vaccine based on a cyclic peptide containing the 446-488 S1 sequence (446-488cc) of the SARS-CoV-2 spike (S) protein from Wuhan isolate. To provide the best immunity against Omicron, here we compared Omicron-specific immunity induced by a Wuhan-based 446-488cc peptide, by a Wuhan-based recombinant receptor-binding domain (RBD) vaccine and by a new 446-488cc peptide vaccine based on the Omicron sequence. Antibodies induced by Wuhan peptide 446-488cc in three murine strains not only recognized the Wuhan and Omicron 446-488 peptides similarly, but also Wuhan and Omicron RBD protein variants. By contrast, antibodies induced by the Wuhan recombinant RBD vaccine showed a much poorer cross-reactivity for the Omicron RBD despite similar recognition of Wuhan and Omicron peptide variants. Finally, although the Omicron-based 446-488cc peptide vaccine was poorly immunogenic in mice due to the loss of T cell epitopes, co-immunization with Omicron peptide 446-488cc and exogenous T cell epitopes induced strong cross-reactive antibodies that neutralized Omicron SARS-CoV-2 virus. Since mutations occurring within this sequence do not alter T cell epitopes in humans, these results indicate the robust immunogenicity of 446-488cc-based peptide vaccines that induce antibodies with a high cross-recognition capacity against Omicron, and suggest that this sequence could be included in future vaccines targeting the Omicron variant.

Intramuscular injection of a mixture of COVID-19 peptide vaccine and tetanus vaccine in horse induced neutralizing antibodies against authentic virus of SARS-CoV-2 Delta variant.

Peptide vaccine is not effective due to its low immunogenicity. To improve the efficacy of peptide vaccine against COVID-19, a novel method was developed by mixing a COVID-19 peptide vaccine with a tetanus vaccine. In this study, intramuscular injection of a mixture of COVID-19 peptide vaccine and tetanus vaccine twice, i.e., first dose on day 0 and second dose on day 21, induced neutralizing antibodies against authentic virus of SARS-CoV-2 Delta variant in a horse. Horse serum of day 35, i.e., two weeks after the second dose, neutralized authentic virus of SARS-CoV-2 Delta variant, equal to half effectiveness of human serum from vaccinees of Moderna COVID-19 vaccine. However, neither horse serum nor human serum neutralized Omicron variant authentic virus. No side effects were observed after each dose. This study indicates intramuscular injection of a mixture of COVID-19 peptide vaccine and tetanus vaccine may work in humans to improve peptide vaccine efficacy against SARS-CoV-2.

SARS-CoV-2 Vaccines: Types, Working Principle, and Its Impact on Thrombosis and Gastrointestinal Disorders.

In the current scenario of the coronavirus pandemic caused by Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2), considerable efforts have been made to control the pandemic by the development of a strong immune system through massive vaccination. Just after the discovery of the genetic sequences of SARS-CoV-2, the development of vaccines became the prime focus of scientists around the globe. About 200 SARS-CoV-2 candidate vaccines have already been entered into preclinical and clinical trials. Various traditional and novel approaches are being utilized as a broad range of platforms. Viral vector (replicating and non-replicating), nucleic acid (DNA and RNA), recombinant protein, virus-like particle, peptide, live attenuated virus, an inactivated virus approaches are the prominent attributes of the vaccine development. This review article includes the current knowledge about the platforms used for the development of different vaccines, their working principles, their efficacy, and the impacts of COVID-19 vaccines on thrombosis. We provide a detailed description of the vaccines that are already approved by administrative authorities. Moreover, various strategies utilized in the development of emerging vaccines that are in the trial phases along with their mode of delivery have been discussed along with their effect on thrombosis and gastrointestinal disorders.

Immunoinformatics-Based Identification of B and T Cell Epitopes in RNA-Dependent RNA Polymerase of SARS-CoV-2.

INTRODUCTION: The ongoing coronavirus disease 2019 (COVID-19), which emerged in December 2019, is a serious health concern throughout the world. Despite massive COVID-19 vaccination on a global scale, there is a rising need to develop more effective vaccines and drugs to curb the spread of coronavirus. METHODOLOGY: In this study, we screened the amino acid sequence of the RNA-dependent RNA polymerase (RdRp) of SARS-CoV-2 (the causative agent of COVID-19) for the identification of B and T cell epitopes using various immunoinformatic tools. These identified potent B and T cell epitopes with high antigenicity scores were linked together to design the multi-epitope vaccine construct. The physicochemical properties, overall quality, and stability of the designed vaccine construct were confirmed by suitable bioinformatic tools. RESULTS: After proper in silico prediction and screening, we identified 3 B cell, 18 CTL, and 10 HTL epitopes from the RdRp protein sequence. The screened epitopes were non-toxic, non-allergenic, and highly antigenic in nature as revealed by appropriate servers. Molecular docking revealed stable interactions of the designed multi-epitope vaccine with human TLR3. Moreover, in silico immune simulations showed a substantial immunogenic response of the designed vaccine. CONCLUSIONS: These findings suggest that our designed multi-epitope vaccine possessing intrinsic T cell and B cell epitopes with high antigenicity scores could be considered for the ongoing development of peptide-based novel vaccines against COVID-19. However, further in vitro and in vivo studies need to be performed to confirm our in silico observations.

MECHANISMS OF FORMATION OF HYBRID IMMUNITY IN PEOPLE WHO RECOVERED FROM COVID-19 AND WERE VACCINATED WITH SARS-CoV-2 PEPTIDE ANTIGENS

The relevance of the current epidemic situation of a new coronavirus infection is determined by new strains of the virus and the registration of cases of re-infection in COVID-19 survivors earlier. In this regard, the questions about the expediency and nature of vaccination of those who have been ill attract close attention, moreover it has affected the formation of the concept of “hybrid immunity”. The aim of this study was to analyze changes in the parameters of the immune system, reflecting their regulatory and functional potential, in response to the introduction of the peptide vaccine EpiVacCorona to persons who have suffered from the new coronavirus infection. To study the features of the formation of hybrid immunity, a retrospective analysis of the observation of 43 study participants was carried out. The inclusion criteria were data confirming COVID-19 in mild and moderate forms of the course in the period from six months to a year ago, a low level or absence of antibodies to the nucleocapsid protein SARS-CoV-2, a negative PCR result for the presence of the SARS-CoV-2 virus, the absence of comorbid pathology. The subpopulation composition, regulatory and functional potential of the immune system were determined by flow cytofluorimetry using a set of monoclonal antibodies corresponding to the goals. 21 days after the administration of a single dose of EpiVacCorona, antibodies to the vaccine peptide antigens were registered in all study participants at the highest coefficient of positivity values for the SARS-CoV-2-IgG-Vector test system used. In addition, there was a fourfold increase in the number of specific IgG to the N protein. A specific immune response to recombinant SARS-CoV-2 antigens was accompanied by a decrease in the circulation of the number of monocytes expressing TLR4, T helper cells expressing the interaction coreceptor with antigen-presenting cells, unconnected B memory with an increase in the number of B lymphocytes expressing the CD40 T-B coreceptor interaction molecule. The remaining differences in the functioning of the immune system identified in patients with COVID-19 before the vaccination in comparison with the control data have not changed. The differences consist in a decrease in the proportion of monocytes expressing HLA-DR, an increase in the expression of interaction molecules on T and B lymphocytes, an increase in the number of Treg, B1 cells, activated B lymphocytes with a decrease in the proportion of suppressor Breg and B memory. The totality of the presented data demonstrates that the COVID-19 infection that preceded vaccination in mild and moderate clinical course contributes to the formation of immunological memory, which made it possible to form a secondary immune response even to a single injection of peptide antigens of the virus.

Interim safety and immunogenicity results of a phase I trial evaluating the multi-peptide COVID-19 vaccine candidate CoVac-1 for induction of SARS-CoV-2 T cell immunity in cancer patients with disease- or treatmentrelated immunoglobulin deficiency

Individuals with impaired ability to mount a humoral immune response, either during natural infection or upon prophylactic vaccination, are at high risk for a severe course of COVID-19. Besides humoral immunity mediated by B cells, T cell immunity is key for the control of viral infections. We developed the peptide-based vaccine candidate CoVac-1, which primarily aims for the induction of SARS-CoV-2-specific T cells. CoVac-1 comprises six promiscuous HLA-DR-binding SARS-CoV-2-derived T cell epitopes from various viral proteins proven (i) to be frequently and HLAindependently recognized by T cells in COVID-19 convalescents, (ii) to be of pathophysiological relevance for T cell immunity to combat COVID-19, and (iii) to mediate long-term immunity after infection (Nelde et al. Nat Immunol 2021, Bilich et al. Sci Transl Med 2021). CoVac-1 vaccine peptides are adjuvanted with the novel toll-like receptor 1/2 agonist XS15 emulsified in Montanide ISA51 VG. In a first-in-human clinical trial in healthy adults (NCT04546841), CoVac-1 showed a favorable safety profile and induced profound and long-lasting T cell immunity after single dose administration in 100% of the study subjects, mediated by multifunctional T-helper 1 CD4+ and CD8+ T cells. CoVac-1-induced T cell responses surpassed those after SARS-CoV-2 infection as well as those after vaccination with approved vaccines and were unaffected by current SARS-CoV-2 variants of concern (Heitmann et al. Nature 2021). Here we present the interim safety and immunogenicity results of our Phase I/II trial evaluating CoVac-1 in patients with congenital or acquired B cell deficiency, mainly comprising leukemia and lymphoma patients (NCT04954469). 64% of study subjects had previously been vaccinated with approved vaccines without developing any humoral immune response. Alike in the healthy adults, CoVac-1 showed a good safety and tolerability profile without relevant systemic adverse events. CoVac-1-specific T cell responses could be documented in 93% of study subjects on day 28 after CoVac-1 application, with earliest responses evidenced at day 14 (71%). Vaccine-induced T cell responses were mediated by multifunctional T-helper 1 CD4+ T cells. Of note, CoVac-1 induced T cell responses in this highly immune compromised study population were similar to those occurring in healthy volunteers after natural infection or induced by approved vaccines. These results identify CoVac-1 as promising vaccine candidate for cancer and other immunocompromised patients with immunoglobulin deficiency. Recruitment of the Phase II part of the trial is ongoing with results expected for March 2022.

Primary analysis of MOUNTAINEER: A phase 2 study of tucatinib and trastuzumab for HER2-positive mCRC

Background: Despite the occurrence of HER2 amplification/overexpression (HER2+) in ~3% to 5% of all patients with metastatic colorectal cancer (mCRC) and up to ~10% of patients with RAS/BRAF wild-type mCRC, there are currently no FDA- or EMA-approved HER2-directed therapies for HER2+ mCRC. Patients with mCRC who progress on early lines of chemotherapy regimens receive limited clinical benefit from current standard-of-care treatments. Tucatinib is a highly selective, HER2-directed, tyrosine kinase inhibitor. The MOUNTAINEER trial (NCT03043313) was initiated to evaluate the efficacy and safety of the investigational combination of tucatinib with trastuzumab in patients with HER2+ mCRC. Here we present results from the primary analysis of MOUNTAINEER. Methods: MOUNTAINEER is a multi-center, open-label, randomised, phase 2 trial conducted in the US and Europe. Eligible patients had HER2+ (one or more local tests: 3+ immunohistochemistry, 2+ immunohistochemistry with amplification by in situ hybridization, or amplification by next‑generation sequencing of tumor tissue) and RAS wild-type mCRC with progression on or intolerance to fluoropyrimidine, oxaliplatin, irinotecan, and an anti-VEGF antibody. Measurable disease and an ECOG performance status of 0–2 were required. Previous HER2-directed therapies were not permitted. The trial initially consisted of a single cohort (Cohort A) to be treated with tucatinib (300 mg PO BID) and trastuzumab (8 mg/kg IV then 6 mg/kg IV every 3 weeks). The trial was expanded to include patients randomised 4:3 to receive tucatinib + trastuzumab (Cohort B) or tucatinib monotherapy (Cohort C). The primary endpoint is confirmed objective response rate (ORR) per RECIST 1.1 by blinded independent central review (BICR) in Cohorts A+B. Secondary endpoints include duration of response (DOR), progression-free survival (PFS), overall survival (OS), and safety and tolerability. Results: MOUNTAINEER enrolled 117 patients between 08Aug2017 and 22Sept2021. Data cutoff was 28Mar2022. The median age was 56.0 years (range, 24, 77), and baseline characteristics were balanced across cohorts. Eighty-six patients received at least 1 dose of study treatment in Cohorts A+B, and 30 patients received tucatinib monotherapy in Cohort C (total, 116). The overall median duration of follow-up was 16.3 months (IQR, 10.8, 28.2). In Cohorts A+B, the confirmed ORR by BICR was 38.1% (95% CI, 27.7, 49.3). The median DOR was 12.4 months (95% CI, 8.5, 20.5). The median PFS was 8.2 months (95% CI, 4.2, 10.3), and the median OS was 24.1 months (95% CI, 20.3, 36.7). The most common adverse events (AEs) in Cohorts A+B were diarrhoea (64.0%), fatigue (44.2%), nausea (34.9%), and infusion-related reaction (20.9%);the most common AE of grade ≥3 was hypertension (7.0%). Adverse events leading to tucatinib discontinuation in Cohorts A+B occurred in 5.8% of patients and included alanine amino transferase increase (2.3%), COVID-19 pneumonia (1.2%), cholangitis (1.2%), and fatigue (1.2%). No deaths resulted from AEs. Conclusions: In patients with chemotherapy-refractory HER2+ mCRC, tucatinib in combination with trastuzumab was well tolerated with clinically meaningful antitumor activity including durable responses and a median overall survival of 2 years. Tucatinib in combination with trastuzumab has the potential to become a new standard of care for patients with HER2+ mCRC. Clinical trial identification: NCT03043313. Editorial acknowledgement: The authors thank Joseph Giaconia of MMS Holdings, Michigan, USA for providing medical writing support/editorial support, which was funded by Seagen Inc., Bothell, WA, USA in accordance with Good Publication Practice (GPP3) guidelines. Legal entity responsible for the study: Seagen Inc. Funding: Seagen Inc. Disclosures: J. Strickler: Advisory / Consultancy: Seagen, Bayer, Pfizer;Research grant / Funding (institution): Amgen, Roche/Genentech, Seagen. A. Cercek: Advisory / Consultancy: Bayer, Merck, Seagen;Research grant / Funding (institution): Seagen, GSK, Rgenix. T. André: Honoraria (self : Amgen, Astra-Zeneca, Bristol-Myers Squibb, Gritstone Oncology, GlaxoSmithKline, Haliodx, Kaleido Biosciences, Merck & Co., Inc., Pierre Fabre, Sanofi, Servier, Merck & Co., Inc, Servier;Advisory / Consultancy: Astellas Pharma, BMS, Gritstone Oncology, Transgène, Roche/Ventana, Seagen, Merck & Co., Inc, Servier;Research grant / Funding (institution): BMS, Seagen, GSK;Travel / Accommodation / Expenses: BMS, Merck & Co., Inc. K. Ng: Advisory / Consultancy: Seattle Genetics, Bicara Therapeutics, GlaxoSmithKline;Research grant / Funding (institution): Pharmavite, Evergrande Group, Janssen. E. Van Cutsem: Advisory / Consultancy: AbbVie, Array, Astellas, AstraZeneca, Bayer, Beigene, Biocartis, Boehringer Ingelheim, Bristol-Myers Squibb, Celgene, Daiichi, Halozyme, GSK, Helsinn, Incyte, Ipsen, Janssen Research, Lilly, Merck Sharp & Dohme, Merck KGaA, Mirati, Novartis, Pierre Fabre, Roche, Seattle Genetics, Servier, Sirtex, Terumo, Taiho, TRIGR, Zymeworks;Research grant / Funding (institution): Amgen, Bayer, Boehringer Ingelheim, Bristol-Myers Squibb, Celgene, Ipsen, Lilly, Merck Sharp & Dohme, Merck KGaA, Novartis, Roche, Servier. C. Wu: Research grant / Funding (institution): Seagen. A. Paulson: Research grant / Funding (institution): Seattle Genetics. J. Hubbard: Research grant / Funding (institution): Seattle Genetics. H. Lenz: Honoraria (self): BMS, Bayer, Roche;Advisory / Consultancy: Bayer, Merck, Roche;Travel / Accommodation / Expenses: BMS, Bayer, Merck KG;Shareholder / Stockholder / Stock options: Fulgent. M. Stecher: Full / Part-time employment: SeaGen. W. Feng: Full / Part-time employment: Seagen. T. Bekaii-Saab: Honoraria (self): Royalties: Uptodate;Advisory / Consultancy: Consulting (to institution): Ipsen, Arcus, Pfizer, Seattle Genetics, Bayer, Genentech, Incyte, Eisai and Merck., Consulting (to self): Stemline, AbbVie, Boehringer Ingelheim, Janssen, Daichii Sankyo, Natera, TreosBio, Celularity, Exact Science, Sobi, Beigene, Kanaph, Astra Zeneca, Deciphera, MJH Life Sciences, Aptitude Health, Illumina and Foundation Medicine, IDMC/DSMB: Fibrogen, Suzhou Kintor, Astra Zeneca, Exelixis, Merck/Eisai, PanCan and 1Globe;Research grant / Funding (institution): Agios, Arys, Arcus, Atreca, Boston Biomedical, Bayer, Eisai, Celgene, Lilly, Ipsen, Clovis, Seattle Genetics, Genentech, Novartis, Mirati, Merus, Abgenomics, Incyte, Pfizer, BMS.;Licensing / Royalties: WO/2018/183488: HUMAN PD1 PEPTIDE VACCINES AND USES THEREOF – Licensed to Imugene, WO/2019/055687: METHODS AND COMPOSITIONS FOR THE TREATMENT OF CANCER CACHEXIA – Licensed to Recursion. All other authors have declared no conflicts of interest.