Introduction: Early detection of liver fibrosis and monitoring response to treatment crucial for the management of patients are currently not feasible in clinical practice. Platelet derived growth factor receptor beta (PDGER-beta) expression is regarded as a potential biomarker to determine the stages of fibrotic diseases including liver fibrosis. [Ga-68]Ga-BOT5035 comprising a bicyclic peptide was developed for specific targeting of ppGrR-beta overexpressed in pathological fibrosis. The realization of microdosing phase 0 study using [Ga-68]Ga-BOT5035 positron emission tomography required automated good manufacturing practice (GMP) compliant production of [Ga-68]Ga-BOT5035 presented herein. Moreover, the investigation of radiation dosimetry was conducted to ensure possibility of multiple annual examinations for disease monitoring in clinical setup.

Methods: The active pharmaceutical ingredient starting material BOT5035 (GMP grade) was provided by BiOrion Technologies BV. The Ga-68-labelling process was developed and automated using synthesis platform (ModularLab PharmTrace, Eckert & Ziegler), disposable cassettes for Ga-68-labelling, and pharmaceutical grade Ge-68/Ga-68 generator (GalliaPharm (R)) purchased from Eckert & Ziegler. Radiolysis sensitive BOT5035 required development and systematic optimization of the labelling synthesis parameters such as time, temperature, precursor concentration, radical scavenger, buffer concentration and pH. The validation process was conducted with regard to the product quality and quantity, as well as production reproducibility. Human organ equivalent doses and total body effective doses were calculated using Organ Level Internal Dose Assessment Code software (OLINDA/EXM 1.1), based on ex vivo organ distribution in Sprague-Dawley rats.

Results: The GMP compliant automated production of [Ga-68]Ga-BOT5035 with on-line documentation demonstrated high reproducibility. The time for the labelling synthesis and quality control was approximately 60 min. The non-decay corrected radiochemical yield and radiochemical purity of the radiopharmaceutical were 43.7 +/- 7.6% (n = 3, process validation) and 97.7 +/- 0.4% (n = 3, process validation), respectively. Predefined acceptance criteria were met for the sterility, endotoxins level, radionuclidic purity and residual solvent content. The stability at ambient temperature was controlled for 120 min with approved results. Ex vivo organ distribution data revealed fast blood clearance and washout from most of the organs. The dose-limiting organs were kidney and bone marrow. The total effective dose as limiting parameter would allow for up to 3-4 PET scans per annum.

Conclusion: The fully automated and GMP compliant production of [Ga-68]Ga-BOT5035 was developed and thoroughly validated. The radiopharmaceutical was approved by Swedish Medicinal Products Agency and the Ethical Review Authority for the Phase 0 clinical study of the quantitative imaging of liver fibrosis. Human dosimetry calculations extrapolated from animal experiment indicated possibility of 3-4 PET examinations per year.