Cancer Gene Therapy https://doi.org/10.1038/s41417-020-00248-7 REVIEW ARTICLE The future of microfluidics in immune checkpoint blockade Jonathan Briones 1 ● Wilfred Espulgar 1 ● Shohei Koyama 2 ● Hyota Takamatsu 2 ● Eiichi Tamiya 3,4 ● Masato Saito 1,3 Received: 2 June 2020 / Revised: 2 October 2020 / Accepted: 9 October 2020 © The Author(s) 2020. This article is published with open access Abstract Recent advances in microfluidic techniques have enabled researchers to study sensitivities to immune checkpoint therapy, to determine patients’ response to particular antibody treatment. Utilization of this technology is helpful in antibody discovery and in the design of personalized medicine. A variety of microfluidic approaches can provide several functions in processes such as immunologic, genomic, and/or transcriptomic analysis with the aim of improving the efficacy and coverage of immunotherapy, particularly immune checkpoint blockade (ICB). To achieve this requires researchers to overcome the challenges in the current state of the technology. This review looks into the advancements in microfluidic technologies applied to researches on immune checkpoint blockade treatment and its potential shift from proof-of-principle stage to clinical application. Introduction Cancer immunotherapy (CIT) is a promising anticancer treatment strategy with more efficient survival rate and lesser adverse effect than conventional treatments such as surgery, radiotherapy, chemotherapy, and molecular tar- geted therapy [1]. The increasing demand for immu- notherapeutics in clinical research as well as in hospital and clinics has fueled a market growth with a USD 242.86 billion forecast by 2026 [2]. The immune system has the ability to recognize and kill cancer cells without toxicity to normal and healthy ones [3]. This treatment approach dates back to the late 1800s but immunotherapy’s major break- throughs in understanding the mechanisms in full T-cell activation and tumor-induced immunosuppression came about in the last decade [1, 4]. At present, immunotherapy is an established strategy and has become a new standard of care in clinical treatments with unprecedented survival improvements to patients with advanced-stage tumors [5, 6]. Although significant responses have been recorded, not all patients benefit from the treatment approach because of the immune system’s diversity and dynamic nature, together with inter- and intratumor heterogeneity. Tumors can adapt, mutate, and escape immune surveillance [3]. The efficacy of immunotherapeutics in modulating cancer progression is still lacking for most human cancers [4]. The small number of success of CIT agents poses a challenge to clinicians and researchers [7–9]. For instance, only 12.46% of US patients were reported in 2018 to respond to checkpoint inhibitor drugs [10]. Overall, about 20–40% of cancer patients were found to respond to immunotherapy [11]. To further improve the treatment effectiveness and patient response rates, more specific biomarkers and immune checkpoint inhibitors are needed to be identified. This would require better predictive tools and assays for careful screening of responders to immunotherapy [1]. Microfluidic platforms have the capacity to address the needs and challenges facing CIT. These tools are capable of single-cell analysis, mimic tumor microenvironment (TME), and perform real-time measurement. Microfluidic technology provides high precision of liquid manipulation that conventional bench-top approaches cannot perform [12, 13]. Among other advantages include reduced size of operating systems, reagent consumption, waste production, and power requirement, while at the same time having more speed in analysis and flexibility in design. For example, a * Masato Saito saitomasato@ap.eng.osaka-u.ac.jp 1 Graduate School of Engineering, Osaka University, Suita, Osaka 565-0871, Japan 2 Graduate School of Medicine, Osaka University, Suita, Osaka 565-0871, Japan 3 AIST PhotoBIO-OIL, Osaka University, Suita, Osaka 565-0871, Japan 4 The Institute of Scientific and Industrial Research, Osaka University, Suita, Osaka 565-0871, Japan 1234567890();,: 1234567890();,: