Non-invasive visualization of liver fibrosis with [68Ga]Ga-DOTA-FAPI-04 PET from preclinical insights to clinical translation

Purpose The reversibility of early liver fibrosis highlights the need for improved early detection and monitoring techniques. Fibroblast activation protein (FAP) is a promising theranostics target significantly upregulated during fibrosis. This preclinical and preliminary clinical study investigated a FAP-targeted probe, gallium-68-labeled FAP inhibitor 04 ([ 68 Ga]Ga-DOTA-FAPI-04), for its capability to visualize liver fibrosis. Methods The preclinical study employed [ 68 Ga]Ga-DOTA-FAPI-04 micro-positron emission tomography (PET)/computed tomography (CT) on carbon tetrachloride-induced mice model (n = 34) and olive oil-treated control group (n = 26), followed by validation of the probe's biodistribution. Hepatic uptake was correlated with fibrosis and inflammation levels, quantified through histology and serum assays. FAP and α-smooth muscle actin expression were determined by immunohistochemistry, as well as immunofluorescence. The subsequent clinical trial enrolled 26 patients with suspected or confirmed liver fibrosis to undergo [ 68 Ga]Ga-DOTA-FAPI-04 PET/magnetic resonance imaging or PET/CT. Key endpoints included correlating [ 68 Ga]Ga-DOTA-FAPI-04 uptake with histological inflammation grades and fibrosis stages, and evaluating its diagnostic and differential efficacy compared to established serum markers and liver stiffness measurement (LSM). Results [ 68 Ga]Ga-DOTA-FAPI-04 mean uptake in mice livers was notably higher than in control mice, increasing from week 6 [0.70 ± 0.11 percentage injected dose per cubic centimeter (%ID/cc)], peaking at week 10 (0.97 ± 0.15%ID/cc) and slightly reducing at week 12 (0.89 ± 0.28%ID/cc). The hepatic biodistribution and FAP expression showed a consistent trend. In the patient cohort, hepatic [ 68 Ga]Ga-DOTA-FAPI-04 uptake presented moderate correlations with inflammation grades (r = 0.517 to 0.584, all P