68 Ga-grazytracer PET for noninvasive assessment of response to immunotherapy in solid tumors and lymphomas: a phase 1/2 clinical trial.

To tackle the clinical challenge of noninvasively assessing immunotherapy efficacy in patients, here we used positron emission tomography (PET) with ⁶⁸ Ga-grazytracer, which targets granzyme B, a crucial effector molecule secreted by activated CD8 ⁺ T cells. In this phase 1/2 clinical trial (NCT05000372) involving a diverse cohort of 24 patients with solid tumors and lymphomas who received immunotherapies, including immune checkpoint inhibitors (either alone or with chemotherapies) and chimeric antigen receptor-T cell therapy, we examined the in vivo behaviors of ⁶⁸ Ga-grazytracer. Primary endpoints were safety, biodistribution, granzyme B specificity, and the predictive utility of ⁶⁸ Ga-grazytracer, while secondary endpoint was the relationship between ⁶⁸ Ga-grazytracer uptake and tumor immune phenotype. ⁶⁸ Ga-grazytracer exhibited a safe profile and specifically targeted granzyme B in patients. ⁶⁸ Ga-grazytracer PET showed superior predictive value for short-term prognosis and progression-free survival than those of conventional assessment criteria, including RECIST 1.1 and PERCIST. Moreover, the uptake of ⁶⁸ Ga-grazytracer in tumors was significantly higher in those with a "non-desert" immune phenotype than those with an immune "desert" phenotype, thereby meeting the primary and secondary endpoints of this trial. Collectively, we successfully visualized CD8 ⁺ T cell effector function in humans using ⁶⁸ Ga-grazytracer PET, offering insights for enhancing immunotherapy assessment, patient stratification and treatment planning.
(© 2024. The Author(s).)