Ascierto et al. J Transl Med (2021) 19:238 https://doi.org/10.1186/s12967-021-02895-2 Journal of Translational Medicine MEETING REPORT Open Access Perspectives in immunotherapy: meeting report from the immunotherapy bridge (December 2nd–3rd, 2020, Italy) Paolo A. Ascierto1* , Carlo Bifulco2, Fortunato Ciardiello3, Sandra Demaria4,5,6, Leisha A. Emens7,8, Robert Ferris8, Silvia C. Formenti9, Jerome Galon10,11,12, Samir N. Khleif13, Tomas Kirchhof14, Jennifer McQuade15, Kunle Odunsi16,17, Akash Patnaik18, Chrystal M. Paulos19, Janis M. Taube20, John Timmerman21, Bernard A. Fox22, Patrick Hwu23 and Igor Puzanov24 Abstract Improved understanding of tumor immunology has enabled the development of therapies that harness the immune system and prevent immune escape. Numerous clinical trials and real-world experience has provided evidence of the potential for long-term survival with immunotherapy in various types of malignancy. Recurring observations with immuno-oncology agents include their potential for clinical application across a broad patient population with diferent tumor types, conventional and unconventional response patterns, durable responses, and immune-related adverse events. Despite the substantial achievements to date, a signifcant proportion of patients still fail to beneft from current immunotherapy options, and ongoing research is focused on transforming non-responders to respond- ers through the development of novel treatments, new strategies to combination therapy, adjuvant and neoadjuvant approaches, and the identifcation of biomarkers of response. These topics were the focus of the virtual Immunother- apy Bridge (December 2nd–3rd, 2020), organized by the Fondazione Melanoma Onlus, Naples, Italy, in collaboration with the Society for Immunotherapy of Cancer and are summarised in this report. Keywords: Immunotherapy, Checkpoint inhibitors, Combination therapy, Biomarkers, Tumor microenvironment, Vaccine Introduction types of malignancy. Tese studies have highlighted Over recent years, a substantial research efort has several recurring observations with immuno-oncology improved our understanding of tumor immunology and agents, including their potential for clinical application enabled the development of novel treatments that har- across a broad patient population across tumor types, ness the immune system and prevent immune escape. both conventional and unconventional response patterns, Trough numerous clinical trials and real-world experi- durable responses, and immune-related adverse events. ence, evidence of the potential for long-term survival However, a signifcant proportion of patients are still with immunotherapy agents has accumulated in various failing to beneft from current immunotherapy options, and ongoing preclinical and clinical research is focused on transforming non-responders to responders, through *Correspondence: [email protected] the development of novel treatments, new approaches to 1 Department of Melanoma, Cancer Immunotherapy and Innovative Therapy, Istituto Nazionale Tumori IRCCS “Fondazione G. Pascale”, Naples, combination therapy, adjuvant and neoadjuvant cancer Italy immunotherapy, and the identifcation of biomarkers of Full list of author information is available at the end of the article response. © The Author(s) 2021. This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http:// creat iveco mmons. org/ licen ses/ by/4. 0/. The Creative Commons Public Domain Dedication waiver (http:// creat iveco mmons. org/ publi cdoma in/ zero/1. 0/) applies to the data made available in this article, unless otherwise stated in a credit line to the data. Ascierto et al. J Transl Med (2021) 19:238 Page 2 of 16 Biomarkers, drivers of immune response and trends in Further gains in multiplex IF accuracy and reproduc- immunotherapy were the focus of the virtual Immuno- ibility can be achieved through considered cell seg- therapy Bridge (December 2nd–3rd, 2020), organized by mentation and controlling for potential batch-to-batch the Fondazione Melanoma Onlus, Naples, Italy, in collab- variations. Cell segmentation is the process that image oration with the Society for Immunotherapy of Cancer. analysis algorithms use to identify the cell compartments of the membrane, cytoplasm, and nucleus. In immuno- SITC session—Biomarkers oncology, where immune cells and tumor cells are often Multiplex immunofuorescence assay development: in close proximity, errors in cells segmentation often current status and future directions result in the membrane expression of an immunoactive Technologies are now available that allow for the simul- marker being mistakenly attributed to a neighboring cell. taneous targeting of multiple proteins in formalin-fxed Additionally, cell size is often a key component in the parafn-embedded tissue samples, commonly referred image analysis algorithms, and many algorithms struggle to as multiplex immunohistochemistry (IHC) or immu- when there is a wide variation in cell sizes. We found that nofuorescence (IF). Tese approaches can distinguish when we were trying to identify larger cells (tumor cells between diferent cell types expressing the same protein and macrophages) at the same time as smaller cells (lym- and can characterize the density and spatial distribu- phocytes), the accurate segmentation of lymphocytes led tion of specifc cells within the tumor microenvironment to over-segmentation (and thus over-counting) of the (TME). IF also has the beneft of being able to character- tumor cells and macrophages. We found that this could ize a large dynamic range of expression on a cell-by-cell be corrected if the cells bearing each marker were seg- basis. mented individually, rather than attempting to simulta- Consideration needs to be given to assay validation, neously segment cells displaying all markers [3]. Another especially with the increasing ‘plex’ of assays. Multiplex important consideration is batch-to-batch staining vari- IF panel development is the consolidation of multiple ation, in particular when assessing intensity of expres- monoplex IF protocols into a single protocol. Robust sion. Tis can be controlled for by including a tissue in situ assessment of intensity of biomarker expression, microarray of control tissue with each batch, facilitating e.g., programmed death-1 (PD-1) and programmed correction of marker expression intensity across batches; death ligand-1 (PD-L1), in a reproducible manner is also for example, normalizing to tissue controls can reduce desirable. the coefcient of variation in PD-1/PD-L1 expression Best practice guidelines for multiplex IF assays have intensity between batches from 10–15% to ~ 5%. Care- been developed [1]. One key standard is that the multi- ful optimization of multiplex staining, cell segmentation, plex assay should be equivalent to the monoplex IF/IHC and correction for batch-to-batch variation allows for for each individual marker. Multiplex IF assays may show more accurate and robust assessments of marker inten- lower levels of marker detection than their individual sity in situ and associated immuno-oncology biomarker assay components due to steric hinderance between the development. multiple markers, signal interference between the fuors, or diferent reagent properties. For example, we found in Integrating multiomics in the practice of diagnostic the development of a multiplex IF assay that the IF was pathology less sensitive than chromogenic IHC for key markers Deep insights into the biology of cancer, combined with such as PD-L1. Additional amplifcation using an alterna- rapid advances in our understanding of the molecular tive horseradish peroxidase (HRP) polymer maximized biomarker landscape, are transforming the practice of sensitivity of the IF and resulted in comparable sensitiv- oncology and are enabling the growth of personalized ity to chromogenic IHC. Final panel validation showed treatment indications, as illustrated by the ever-growing that the combined multiplex IF panel was similar to the list of Food and Drug Administration (FDA) approved monoplex IF for each marker. Such optimized assays have targeted therapies and in immuno-oncology by the recent been shown to be reproducible in multi-institutional pan-cancer approval of pembrolizumab in patients with a studies [2]. For example, a six-plex multiplex IF assay was tumor mutational burden (TMB) ≥ 10 mut/Mb. Despite shown to have high inter-site concordance for percent this progress, we still struggle to consistently translate PD-L1 co-expression within diferent cell types. Proxim- this knowledge into clinical outcomes, as many patients ity of diferent cell types was also shown to be reproduc- often fail to receive appropriate therapies, with evidence ible with high inter-center concordance. Additional study coming from the non-small