On the automated radiosynthesis of pharmaceutical grade [68Ga]Ga-Pentixafor, its pre-clinical evaluation, clinical application and radiation dosimetry aspects

Abstract

The current study outlines a consistent and reproducible protocol for the routine clinical dose preparation of [⁶⁸Ga]Ga-Pentixafor using the Eckert and Ziegler 'Modular-Lab Standard' non-cassette based automated module, that can be effectively used in the hospital radiopharmacy unit of a high volume nuclear medicine centre. The pre-clinical studies (including in-vitro cell line studies, in-vivo PET/CT imaging and pre-clinical dosimetry) were conducted to show the promising potential of the product for clinical use in targeting CXCR4 tumor overexpression. PET/CT image of SCID mouse bearing lymphoma xenograft tumor, at 2 h post-injection, clearly delineated the tumor. The pre-clinical dosimetry results show the suitability of the product for clinical use in patients. [⁶⁸Ga]Ga-Pentixafor when administered to patients with primary aldosteronism exhibited distinct uptake in the adrenal nodules. The clinical PET/CT scan of the patients demonstrated the potential use of CXCR4 targeted imaging as a promising surgical decision-making tool for patients with primary aldosteronism.

Keywords: CXCR4 receptor; PET/CT; Preclinical dosimetry; [68Ga]Ga-Pentixafor.

Fig. 1

Eckert-Ziegler Modular Lab Standard schematic for the production of [⁶⁸Ga]Ga-Pentixafor.

Fig. 2

Radio TLC chromatogram of [⁶⁸Ga]Ga-Pentixafor in (a) 0.1 M Sodium Citrate Buffer (pH ~ 5.0) R_f = 0.05 and (b) 1 M CH₃COONH₄ (pH:3.5) /CH₃OH: 1/1 (v/v) R_f =0.70. (c) Radio-HPLC chromatogram of [⁶⁸Ga]Ga-Pentixafor (R_t: 11.92 min). (d) UV/VIS spectrum of [⁶⁸Ga]Ga-Pentixafor at 220 nm. (e) Radio-HPLC of [⁶⁸Ga]Ga-Pentixafor (R_t: 11.97 min) at 4 h post radiolabeling, without stabilizer, on storage, at room temperature 25^oC. (f) Radio-TLC of [⁶⁸Ga]Ga-Pentixafor in 0.1 M Sodium Citrate Buffer (R_f: 0.02) after 1 h incubation (in healthy human serum, at 37^oC) & on further storage up to 1 h at 25^oC.

Fig. 3

In-vitro cell binding assay result: Cell concentration (x10⁶/mL) versus Percentage cell binding (n = 3).

Fig. 4

(a) Biodistribution data in SCID mice bearing xenografted lymphoma tumor (n = 3). (b) PET/CT image of SCID mice bearing lymphoma tumor, injected with [⁶⁸Ga]Ga-Pentixafor and imaged 2 h post-injection. (c) Tumor-to-organ ratio of [⁶⁸Ga]Ga-Pentixafor in SCID mice 2 h post-injection.

Fig. 5

Number of nuclear transformations in the organ per unit administered activity (Kinetics value) of the PET tracer [⁶⁸Ga]Ga-Pentixafor, extrapolated to adult reference male (ICRP 89) from mice (n = 3), using OLINDA/EXM 2.0 software.

Fig. 6

(a) Transaxial CT of patient 1 and (b) [⁶⁸Ga]Ga-Pentixafor PET/CT showing intense tracer avid focus (SUVmax 9.37) corresponding to the CT depicted nodule in the medial limb of left adrenal (arrows).

Fig. 7

(a) MIP projection PET-CT image of patient 2 at one hour after i.v injection of 4.6 mCi of [⁶⁸Ga]Ga-Pentixafor. (b) PET-CT coronal fused image showing intense tracer uptake in the nodule at lateral limb of left adrenal gland (arrows). (c) Transaxial CT image. (d) [⁶⁸Ga]Ga-Pentixafor trans axial PET/CT fused image showing intense tracer uptake at the CT described nodule (SUVmax 11.0).

Fig. 8

(a) Trans axial CT image of patient 3 indicating distinct nodule in the left adrenal gland. (b) [⁶⁸Ga]Ga-Pentixafor trans axial PET/CT fused image showing intense tracer uptake in the left adrenal gland (arrows) (SUV max: 22.96). (c) PET/CT coronal fused image showing intense tracer uptake at the CT described nodule in the lateral limb of left adrenal gland. (d) MIP projection PET-CT image at one hour post injection of 5.0 mCi [⁶⁸Ga]Ga-Pentixafor.

Fig. 9

Influence of (a) Ligand amount on RCY & RCP and (b) radiocomplexation time and temperature on final RCY of [⁶⁸Ga]Ga-Pentixafor.