From preclinical development to clinical application: Kit formulation for radiolabelling the minigastrin analogue CP04 with In-111 for a first-in-human clinical trial

Abstract

IntroductionA variety of radiolabelled minigastrin analogues targeting the cholecystokinin 2 (CCK2) receptor were developed and compared in a concerted preclinical testing to select the most promising radiotracer for diagnosis and treatment of medullary thyroid carcinoma (MTC). DOTA–DGlu–DGlu–DGlu–DGlu–DGlu–DGlu– Ala–Tyr–Gly–Trp–Met–Asp–Phe–NH2 (CP04) after labelling with 111In displayed excellent characteristics, such as high stability, receptor affinity, specific and persistent tumour uptake and low kidney retention in animal models. Therefore, it was selected for further clinical evaluation within the ERA-NET project GRAN-T-MTC. Here we report on the development of a pharmaceutical freeze-dried formulation of the precursor CP04 for a first multi-centre clinical trial with 111In-CP04 in MTC patients.Materials and methodsThe kit formulation was optimised by adjustment of buffer, additives and radiolabelling conditions. Three clinical grade batches of a final kit formulation with two different amounts of peptide (10 or 50 μg) were prepared and radiolabelled with 111In. Quality control and stability assays of both the kits and the resulting radiolabelled compound were performed by HPLC analysis.ResultsUse of ascorbic acid buffer (pH 4.5) allowed freeze-drying of the kit formulation with satisfactory pellet-formation. Addition of methionine and gentisic acid as well as careful selection of radiolabelling temperature was required to avoid extensive oxidation of the Met11-residue. Trace metal contamination, in particular Zn, was found to be a major challenge during the pharmaceutical filling process in particular for the 10 μg formulation. The final formulations contained 10 or 50 μg CP04, 25 mg ascorbic acid, 0.5 mg gentisic acid and 5 mg l-methionine. The radiolabelling performed by incubation of 200–250 MBq 111InCl3 at 90 °C for 15 min resulted in reproducible radiochemical purity (RCP) >94%. Kit-stability was proven for >6 months at +5 °C and at +25 °C. The radiolabelled product was stable for >4 h at +25 °C.ConclusionA kit formulation to prepare 111In-CP04 for clinical application was developed, showing high stability of the kit as well as high RCP of the final product.

Structural studies on radiopharmaceutical DOTA-minigastrin analogue (CP04) complexes and their interaction with CCK2 receptor

“…Its radiolabeled complexes have been studied with respect to stability [ 5 ], receptor binding, internalization [ 4 ], in vivo tumor targeting in animals [ 6 ], and kidney retention [ 7 ]. These encouraging results prompted further clinical evaluation of [ 111 In]In-CP04 within the ERA-NET project GRAN-T-MTC [ 8 , 9 ].

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Clinical translation of theranostic radiopharmaceuticals: Current regulatory status and recent examples

“…Data on the chemical and pharmaceutical development and characterization of a freeze‐dried kit formulation for radiolabelling of the radiopharmaceutical precursor CP04 with 111 In (chapter 2.1.P of the CTD) have been recently presented …”

“…Data on the chemical and pharmaceutical development and characterization of a freeze-dried kit formulation for radiolabelling of the radiopharmaceutical precursor CP04 with 111 In (chapter 2.1.P of the CTD) have been recently presented. 27 7.2 | Safety/efficacy data generated (pharmacology, toxicology) Safety and efficacy information was also required to generate a suitable IMPD file for 111 In-CP04 to submit the Clinical Trials. This included pharmacology, toxicology, and dosimetry data that had to be retrieved from preclinical studies in vitro and in suitable animal models, which were summarized recently.…”

Oxidation of methionine — is it limiting the diagnostic properties of 99mTc-labeled Exendin-4, a Glucagon-Like Peptide-1 receptor agonist?

“…The oxidized form of the peptide constitutes another impurity and worsens the overall radiochemical purity of the preparation. It is known from others experience that the application of an antioxidant such as selenomethionine, gentisic acid, ascorbic acid or L-methionine affects the inhibition of methionine oxidation in peptides [17,23,24]. Using this approach we were also able to improve the stability of HYNIC-Met 14 -Exendin-4 during storage of the dry kit by addition of L-methionine as an antioxidant to the dry kit formulation and also prevent the formation of the oxidized form in the final radioactive preparation.…”