Background: Activated hepatic stellate cells (aHSCs) are the key cell population in the injured liver driving fibrogenesis. aHSCs express platelet-derived growth factor receptor beta (PDGFRß), which is absent from quiescent HSCs. PDGFRß is therefore an attractive target of PET tracers for imaging of fibrogenesis. Here, we present the pharmacological characterization of [⁶⁸Ga]Ga-DOTA-Cys-ATH001 in preparation for clinical translation and further confirm PDGFRß as a biomarker of activated HSCs in liver disease by single cell sequencing.

Methods: The expression of PDGFRß in subpopulations of HSCs was evaluated in scRNAseq datasets from both a mouse and human liver samples. DOTA-Cys-ATH001 was evaluated for affinity and mechanism of binding to PDGFRß. [⁶⁸Ga]Ga-DOTA-Cys-ATH001 was evaluated for binding in vitro in mouse and human liver biopsies. The in vivo stability, biodistribution, pharmacokinetics, dosimetry and microdosing toxicology were evaluated in rats and pigs.

Results: PDGFRß expression was specifically upregulated in activated HSCs. [⁶⁸Ga]Ga-DOTA-Cys-ATH001 could differentiate fibrotic liver from healthy liver. The binding co-localized with tissue areas positive for collagen deposition and PDGFRß immunostaining. Based on the microdosing toxicology study the no observed adverse effect level was at least 1000 µg/kg, suggesting that the intended clinical PET scan dose is safe for use. Dosimetry calculations of [⁶⁸Ga]Ga-DOTA-Cys-ATH001 predicted an effective dose in human amenable to repeated examinations.

Conclusions: The data presented here suggests that PDGFRβ PET imaging with [⁶⁸Ga]Ga-DOTA-Cys-ATH001 has potential for non-invasive detection of activated HSCs. Clinical translation of [⁶⁸Ga]Ga-DOTA-Cys-ATH001 is ongoing.