Automated synthesis of <sup>68</sup>Ga-PSMA-11 using the Scintomics<sup>®</sup> GRP module applying acetate buffer as an alternative to HEPES — ASN Events
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  3. Automated synthesis of 68Ga-PSMA-11 using the Scintomics® GRP module applying acetate buffer as an alternative to HEPES

Automated synthesis of 68Ga-PSMA-11 using the Scintomics® GRP module applying acetate buffer as an alternative to HEPES (#93)

Rene Martin 1 , Sebastian Weidlich 1 , Sandra Huebner 1 , Oliver Neels 2 , Klaus Kopka 2 , Marco Mueller 1
  1. ABX advanced biochemical compounds GmbH, Radeberg, SAXONY, Germany
  2. Division of Radiopharmaceutical Chemistry, German Cancer Research Center, Heidelberg, Germany

Introduction

Prostate-specific membrane antigen (PSMA) is highly expressed in almost all prostate cancers and provides a target for diagnostic imaging of prostate cancer using PET/CT (1). The PSMA-targeting ligand Glu-NH-CO-NH-Lys-(Ahx)-HBED-CC (PSMA-11), which binds the motif glutamate-urea-lysine with the chelator HBED-CC in prostate cancer, has superior imaging properties and allows for highly specific complexation of the generator-based radioisotope Gallium-68 (68Ga) (2).

In collaboration with the German Cancer Research Center (DKFZ), we have developed an automated synthesis of 68Ga-PSMA-11 on Scintomics® GRP module, applying a dedicated acetate buffer alternative to HEPES buffer, since this compound is not registered in Ph. Eur. and has to be tested prior to release of the product.

Materials & Methods

The approach comprises elution of the generator (E&Z 68Ge/68Ga-Generator IGG101 GMP using 0,1 N HCl), a NaCl/HCl based 68Ga eluate pre-processing on a cation exchange cartridge, a straightforward labelling protocol, purification and formulation of the radiotracer. The labelling step utilizes a sodium acetate / acetic acid buffer instead of HEPES. Almost complete labelling is obtained after heating for 6 minutes at 50 °C. With 20 µg of PSMA-11, the radiolabelled product is obtained in >60% uncorrected yield after 25 min of synthesis time. The radiochemical purity is >98%, formation of Ga-colloid and remain of free Ga3+ is <1%, respectively. By using acetate buffer instead of HEPES the established Ph. Eur. spot test for HEPES is obsolete. The pH of the final solution is set with a Phosphate-buffered saline to be 7 to 7.5.

Results

We have developed a dedicated synthesis of Glu-NH-CO-NH-Lys-(Ahx)-[68Ga-HBEDD-CC], applying a convenient acetate buffer alternative to HEPES on a disposable kit system that delivers the 68Ga-tracer in high yield.

 

References

1) Ebenhahn, T, et al., [2015], Molecules 20: 14860-14878.                                                                                                                                 

2) Jadvar, H, [2015], J Nucl Med. 56: 1131-1132.