Radiosynthesis and Preclinical Evaluation of [99Mtc]tc-Hynic-anti-tigit for Immuno-SPECT Imaging

T-cell immunoreceptor with Ig and ITIM domains (TIGIT) is a newly identified immune checkpoint involved in tumor immune evasion; it represents a promising target for cancer immunotherapy. Noninvasive in vivo imaging of TIGIT expression may provide valuable insights into the tumor immune microenvironment and facilitate the evaluation of TIGIT-targeted therapies. In this study, tiragolumab (anti-TIGIT monoclonal antibody) was conjugated with HYNIC and radiolabeled with 99mTc using an EDDA/tricine coligand system under optimized mild conditions. Radiochemical purity and stability were assessed by ITLC and SEC-HPLC, while the chelator-to-antibody ratio (CAR) was determined using MALDI-TOF. In vitro binding was evaluated using saturation binding assays in TIGIT-expressing Jurkat cells, and the immunoreactivity was evaluated by Lindmo analysis. Biodistribution and small-animal SPECT imaging were conducted in a Jurkat tumor-bearing mouse model. The radioconjugate was obtained with a radiochemical yield of 64.2 ± 1.7