While highly efficient in hematological malignancies, bispecific antibodies (bsAbs), alike the closely related CAR T cells, are as of yet not successful in solid tumors. Moreover, all presently available T cell-mobilizing strategies cause substantial side effects that endanger patients and limit applicable doses and thus efficacy. Here we report on the development of CC-1, a PSMAxCD3 bsAb that is constructed in a novel IgG-based format (IgGsc) and contains a proprietary PSMA binder with extended reactivity. CC-1 displays a prolonged serum half-life, especially when compared to the BiTE bsAb format. Extensive in vitro and in vivo characterization demonstrated the potency of CC-1 to induce T cell activity in a highly target cell-restricted manner, resulting in profound antitumor activity, which among others allowed for elimination of large established tumors in humanized mice (Zekri et al, EMBO 2020). Exclusively funded by public resources, we conducted GMP production of CC-1 and in November 2019 initiated a first in human trial enrolling castration resistant prostate carcinoma patients (NCT04104607). The trial consists of two parts: a dose escalation phase with intra-individual dose escalation until the target dose of 826µg to determine overall safety, tolerability as well as the maximum tolerated dose (MTD), and a dose expansion phase, where patients are treated on the MTD level to detect possible efficacy. In August 2021, recruitment in the dose escalation phase was completed and the target dose was reached without DLT upon treatment of the 9th patient. A total of 14 patients were treated, with the most frequently observed toxicity being cytokine release syndrome (CRS) in 79% of patients. CRS did not exceed grade 2 according to the Lee et al. grading system (Lee et al., 2014) and resolved in most cases without additional application of tocilizumab. Besides hypertension (observed in 50% of patients), no further CC-1 related toxicities (i.e., Xerostomia, or anaphylactic reaction) were observed. As expected, after prophylactic tocilizumab application decreased neutrophile counts and elevated liver enzymes were observed in 86% and 43% of patients, respectively. In terms of efficacy, a rapid and profound decline of elevated PSA levels was observed in all the heavily pre-treated patients, with up to 60% reduction compared to baseline. Three patients of the dose escalation phase received multiple treatment cycles at the highest dose level, based on clinical tolerability, documented induction of potent T cell activation as well as rapid and profound decline of elevated PSA levels. Taken together, CC-1 is a promising compound with a favorable toxicity profile and promising clinical activity. Recruitment in the dose expansion phase is ongoing with the respective data to be presented at the meeting. Citation Format: Jonas S. Heitmann, Juliane S. Walz, Martin Pflügler, Maddalena Marconato, Christian M. Tegeler, Julia Reusch, Jannik Labrenz, Richard Schlenk, Gundram Jung, Helmut Salih. CC-1, a bispecific PSMAxCD3 antibody for treatment of prostate carcinoma: Results of the ongoing phase I dose escalation trial [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 CT141.

T-cell recognition of HLA-presented antigens is central for the immunological surveillance of malignant disease and key for the development of novel T-cell-based immunotherapy approaches. In recent years, large-scale immunopeptidome studies identified naturally presented tumor-associated antigens for several malignancies. Regarding ovarian carcinoma (OvCa), Mucin-16 (MUC16) and Mesothelin (MSLN) were recently described as the top HLA class I- and HLA class II-presented tumor antigens, respectively. Here, we investigate the role and impact of immunopeptidome-presented tumor antigens on the clinical outcomes of 39 OvCa patients with a follow-up time of up to 50 months after surgery. Patients with a HLA-restricted presentation of high numbers of different MSLN-derived peptides on their tumors exhibited significantly prolonged progression-free (PFS) and overall survival (OS), whereas the presentation of MUC16-derived HLA class I-restricted peptides had no impact. Furthermore, a high HLA-DRB gene expression was associated with increased PFS and OS. In line , in silico prediction revealed that MSLN-derived HLA class II-presented peptides are predominantly presented on HLA-DR allotypes. In conclusion, the correlation of MSLN tumor antigen presentation and HLA-DRB gene expression with prolonged survival indicates a central role of CD4+ T-cell responses for tumor immune surveillance in OvCa, and highlights the importance of immunopeptidome-guided tumor antigen discovery.

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With the routine use of effective severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) vaccines, the number of life-threatening coronavirus disease 2019 (COVID-19) courses have largely been reduced. However, multiple COVID-19 convalescents, even after asymptomatic to moderate disease, suffer from post-COVID syndrome, with relevant limitations in daily life. The pathophysiologic mechanisms of post-COVID syndrome are still elusive, with dysregulation of the immune system suggested as a central mechanism. Here, we assessed COVID-19 post-infectious symptoms (5–6 months after PCR-confirmed acute infection) together with the humoral immune response against SARS-CoV-2 in non-hospitalized COVID-19 convalescents, early (5–6 weeks) and late (5–6 months) after their first positive SARS-CoV-2 PCR result. Convalescents reporting several post-infectious symptoms (>3) showed higher anti-spike and anti-nucleocapsid antibody levels 5–6 weeks after PCR-confirmed infection with the latter remained increased 5–6 months after positive PCR. Likewise, a higher post-infectious symptom score was associated with increased antibody levels. Of note, convalescents displaying neuro-psychiatric symptoms such as restlessness, palpitations, irritability, and headache, as well as general symptoms such as fatigue/reduced power had higher SARS-CoV-2-specific antibody levels compared with asymptomatic cases. The increased humoral immune response in convalescents with post-COVID syndrome might be useful for the detection of individuals with an increased risk for post-COVID syndrome.

Ovarian carcinoma (OvCa) is the seventh most common malignancy in women and the eighth leading cause of cancer-related deaths worldwide. In a previous study, we characterized the antigenic landscape of ovarian carcinoma by mass spectrometry-based immunopeptidomics and identified novel OvCa-associated tumor antigens, including Mucin-16 (MUC-16) and Mesothelin (MSLN) with the aim to develop novel T cell-based immunotherapies (Schuster et al. PNAS 2017). Here, we analyzed the immunopeptidomics data of this OvCa cohort in relation to clinical patient characteristics and disease outcome. Analysis included 43 OvCa patients with respective immunopeptidomics and RNA sequencing data, comprising immunopeptidome diversity, tumor antigen presentation and expression (MUC16, MSLN) as well as HLA mRNA expression.Analyzing HLA class I-restricted tumor antigen presentation in relation to clinical data, we could show that nodal-positive patients presented more frequently HLA-restricted peptides derived from the tumor antigen MUC16 (p = 0.0087) and showed significantly increased numbers of unique MUC16-derived HLA-presented peptides within the total immunopeptidome (p = 0.042) compared to nodal-negative patients. No significant difference in HLA class I immunopeptidome diversity, overall tumor antigen presentation, and expression was observed for histological subtypes, grading, or the prevalence of distant metastases. For HLA class II-restricted tumor antigen presentation and HLA expression in relation to clinical data, we observed a more diverse HLA class II immunopeptidome in terms of different HLA class II-presented peptides (p = 0.011) for patients with high tumor grading (G3) compared to low/intermediate (G1/G2) grading. In line, the tumors of these patients also presented an increased number of different MSLN-derived HLA class II-restricted peptides (p = 0.021). No significant difference in HLA class II immunopeptidome diversity, tumor antigen presentation and expression was seen for the prevalence of distant metastasis, histological subtypes, or nodal positivity.Of note, patients presenting MSLN-derived peptides in their immunopeptidome showed a significantly prolonged recurrence-free survival (RFS, p = 0.011). In addition, patients exhibiting a high expression of HLA-DR showed a significantly increased RFS (p = 0.018 for HLA-DRA, p = 0.0031 for HLA-DRB).In conclusion, this work provides first insights on the relation of immunopeptidomic characteristics, comprising HLA expression and tumor antigen presentation, with clinical characteristics and disease outcome of OvCa patients. The observed correlation of HLA-DR expression and HLA class II tumor antigen presentation with prolonged RFS indicates a central role of CD4+ T cell responses for anti-tumor immune surveillance in ovarian cancer. Citation Format: Christian M. Tegeler, Jonas S. Heitmann, Helmut R. Salih, Juliane S. Walz, Annika Nelde. Clinical implications of HLA expression and immunopeptidome-presented tumor antigens in ovarian carcinoma [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 1972.