T cell immunity is central for the control of viral infections. CoVac-1 is a peptide-based vaccine candidate, composed of SARS-CoV-2 T cell epitopes derived from various viral proteins1,2, combined with the Toll-like receptor 1/2 agonist XS15 emulsified in Montanide ISA51 VG, aiming to induce profound SARS-CoV-2 T cell immunity to combat COVID-19. Here we conducted a phase I open-label trial, recruiting 36 participants aged 18–80 years, who received a single subcutaneous CoVac-1 vaccination. The primary end point was safety analysed until day 56. Immunogenicity in terms of CoVac-1-induced T cell response was analysed as the main secondary end point until day 28 and in the follow-up until month 3. No serious adverse events and no grade 4 adverse events were observed. Expected local granuloma formation was observed in all study participants, whereas systemic reactogenicity was absent or mild. SARS-CoV-2-specific T cell responses targeting multiple vaccine peptides were induced in all study participants, mediated by multifunctional T helper 1 CD4+ and CD8+ T cells. CoVac-1-induced IFNγ T cell responses persisted in the follow-up analyses and surpassed those detected after SARS-CoV-2 infection as well as after vaccination with approved vaccines. Furthermore, vaccine-induced T cell responses were unaffected by current SARS-CoV-2 variants of concern. Together, CoVac-1 showed a favourable safety profile and induced broad, potent and variant of concern-independent T cell responses, supporting the presently ongoing evaluation in a phase II trial for patients with B cell or antibody deficiency.

The DNAJB1-PRKACA fusion transcript is the oncogenic driver in fibrolamellar hepatocellular carcinoma, a lethal disease lacking specific therapies. This study reports on the identification, characterization, and immunotherapeutic application of HLA-presented neoantigens specific for the DNAJB1-PRKACA fusion transcript in fibrolamellar hepatocellular carcinoma. DNAJB1-PRKACA-derived HLA class I and HLA class II ligands induce multifunctional cytotoxic CD8+ and T-helper 1 CD4+ T cells, and their cellular processing and presentation in DNAJB1-PRKACA expressing tumor cells is demonstrated by mass spectrometry-based immunopeptidome analysis. Single-cell RNA sequencing further identifies multiple T cell receptors from DNAJB1-PRKACA-specific T cells. Vaccination of a fibrolamellar hepatocellular carcinoma patient, suffering from recurrent short interval disease relapses, with DNAJB1-PRKACA-derived peptides under continued Poly (ADP-ribose) polymerase inhibitor therapy induces multifunctional CD4+ T cells, with an activated T-helper 1 phenotype and high T cell receptor clonality. Vaccine-induced DNAJB1-PRKACA-specific T cell responses persist over time and, in contrast to various previous treatments, are accompanied by durable relapse free survival of the patient for more than 21 months post vaccination. Our preclinical and clinical findings identify the DNAJB1-PRKACA protein as source for immunogenic neoepitopes and corresponding T cell receptors and provide efficacy in a single-patient study of T cell-based immunotherapy specifically targeting this oncogenic fusion.

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 HLA-independently 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 Montanide࣪ 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. Citation Format: Claudia Tandler, Jonas S. Heitmann, Maddalena Marconato, Yacine Maringer, Monika Denk, Marion Richter, Annika Nelde, Imma Fischer, Markus W. Löffler, Hans-Georg Rammensee, Helmut R. Salih, Juliane S. Walz. 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 treatment-related immunoglobulin deficiency [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr CT258.

Chronic lymphocytic leukemia (CLL) is the most common leukemia in adults. Despite the therapeutic success of novel small molecules (e.g. ibrutinib, idealisib and venetoclax), patients frequently experience disease relapse due to the persistence of minimal residual disease (MRD). Targeting the residual CLL cells by immunotherapy could further improve the depth and persistence of CLL remission. Here, we report on the preclinical development and clinical implementation of a phase I trial evaluating safety, immunogenicity and efficacy in terms of MRD response of a personalized multi-peptide vaccine adjuvanted with the novel toll-like receptor (TLR) 1/2 agonist XS15 emulsified in Montanide࣪ ISA51 VG (Rammensee et al. JIC 2019) in CLL patient receiving Bruton-Tyrosin-Kinase (BTK)-inhibitor based regimes (NCT04688385). So far, broad application of peptide vaccines in cancer patients is hampered by time- and cost-intensive design and the lack of neoepitopes from tumor-specific mutations, especially in low-mutational burden malignancies. To improve on these drawbacks, we developed an immunopeptidome-guided workflow for the design of tumor-associated off-the-shelf peptide warehouses for broadly applicable personalized therapeutics (Nelde et al., Front Immunol, 2021). For the trial reported here, comparative mass spectrometry-based immunopeptidome analyses of 61 CLL patient samples and a dataset of benign tissues samples (n = 351) enabled the identification of high-frequent non-mutated CLL-associated antigens for the most common HLA allotypes (HLA-A*02, -A*24, and -B*07). These antigens were proven to be recognized as T cell epitopes by pre-existing and de novo induced T cells in CLL patients and healthy volunteers, thereby enabling the selection of a 12-peptides panel comprising 9 HLA-class I (3 for each HLA allotype) and 3 HLA class II restricted high frequent CLL-exclusive T cell epitopes as warehouse for the personalized composition of study vaccine cocktails. Our meanwhile ongoing phase I trial recruits CLL patients eligible for treatment with BTK inhibitors. For those with matching HLA allotypes, a personalized peptide-cocktail is formulated comprising 6 CLL-associated peptides (3 HLA class I and 3 HLA class II peptides), selected from our warehouse based on individual immunopeptidome analysis, and 2 highly immunogenic HLA class II control peptides, one viral (human adenovirus C) and one tumor associated (Baculoviral IAP repeat-containing protein 5). Three doses of the vaccine are administered in a 4-weekly interval, after reduction of CLL-load by BTK inhibitors. So far, 10 CLL patients were included in the trial. The first vaccinations will be applied in November and December 2021 with first immunogenicity data expected in March 2022 and to be reported at the meeting. Citation Format: Maddalena Marconato, Annika Nelde, Yacine Maringer, Marcel Wacker, Marion Richter, Monika Denk, Helmut Salih, Jonas Heitmann, Juliane Sarah Walz. A Phase I trial of personalized multi-peptide vaccination in combination with the TLR1/2 ligand XS15 in CLL patients under Bruton-Tyrosin-Kinase-inhibitor based regimes - Preclinical development and study design [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3574.