Abstract B053: Integrated real-time PK/PD cytometry and long-term exploratory immune profiling using Cyto-Chex and TokuKit in global trials

Abstract Background Accurate PK/PD and exploratory cytometry is central to evaluating mechanism, response, biomarkers, and safety in immunotherapy trials. Live-blood cytometry requires processing within 24–72 hours of collection, yet 20–60% of global-trial samples miss this window, and even on-time samples undergo progressive degradation, altering cell counts and shifting immune population frequencies. This instability reduces confidence in cytometry data and limits the reliability and interpretation of PK/PD readouts across sites. Methods We developed a streamlined sample collection and processing workflow integrating Cyto-Chex® BCT for real-time PK/PD cytometry and TokuKit for long-term fixed-blood biobanking and exploratory profiling. Cyto-Chex samples were collected from healthy donors, shipped at ambient temperature, and processed on days 1, 2, 3, 4, and 7 after blood draw using a 15-marker TBNK spectral flow cytometry panel with TruCount beads on a Cytek Aurora. In parallel, aliquots from the same Cyto-Chex samples were transferred into TokuKit and stored at –80°C for high-dimensional cytometry on the Helios mass cytometer. Assay evaluation included (1) Cyto-Chex vs. fresh EDTA comparisons at 0 and 24 hours; (2) 1–7-day ambient stability with Cyto-Chex; (3) ≥1-month stability after TokuKit fixation; and (4) intra- and inter-run precision using both the TBNK panel and a 25+ marker cytometry panel. Results Cyto-Chex samples at 24 hours showed immune cell population frequencies within ±1% of fresh EDTA blood. Major T, B, NK, and myeloid populations remained stable through 7 days at ambient temperature with no significant drift in frequencies or absolute counts. After transfer into TokuKit, fixed whole blood stored at –80°C maintained stable frequencies of immune populations and subsets for ≥1 month using a 25+ marker cytometry panel. Intra- and inter-run precision studies demonstrated %CVs that achieved clinical-grade thresholds across both assays, confirming reproducibility of the workflow. Conclusions The integrated Cyto-Chex + TokuKit workflow enables real-time PK/PD cytometry and long-term high-dimensional profiling from a single blood draw, simplifying collection at clinical sites. Cyto-Chex stabilization supports ambient-temperature shipping to a centralized cytometry laboratory, reducing site-to-site variability and improving consistency of immune monitoring across global trials. Transfer into TokuKit enables long-term banking of fixed whole blood for exploratory biomarker and mechanism-of-action studies. Together, this workflow improves the feasibility and reliability of immune monitoring in multi-site immunotherapy trials. AI-assisted text drafting was used and reviewed by the authors. Citation Format: Sacha Martiny, Hannah Selken, Kristina Magee, Justin Jarrell, Ramji Srinivasan, Li-Chun Cheng. Integrated real-time PK/PD cytometry and long-term exploratory immune profiling using Cyto-Chex and TokuKit in global trials [abstract]. In: Proceedings of the AACR Immuno-Oncology Conference (AACR IO): Discovery and Innovation in Cancer Immunology: Revolutionizing Treatment through Immunotherapy; 2026 Feb 18-21; Los Angeles, CA. Philadelphia (PA): AACR; Cancer Immunol Res 2026;14(2 Suppl):Abstract nr B053.