Poster De Conférence Année : 2026

Optimising 99mTc-HYNIC-PSMA labelling to achieve a homogeneous isoform profile: a step toward a standardised kit-based formulation

Résumé

Background and Importance: Prostate-specific membrane antigen (PSMA) is a transmembrane glycoprotein highly expressed in advanced prostate cancer. Radiolabelled PSMA ligands have become key molecular probes for diagnostic imaging. Among them, the technetium-99m-labelled iPSMA compound offers a cost-efficient SPECT alternative to PET tracers. However, the radiolabelling process can produce multiple chemical isoforms, depending on reaction parameters, potentially affecting product uniformity and clinical performance. Aim and Objectives: To identify radiolabelling conditions that consistently generate a single predominant 99mTc-iPSMA isoform with high radiochemical pu rity (RCP). Material and Methods: A total of 21 labelling protocols were systematically assessed in triplicate. Experimental variables included buffer composition, presence or absence of stannous chloride (SnCl2), use of transfer and co-ligands (tricine, EDDA, nicotinic acid), and addition of radiolysis stabilisers such as ascorbic acid or methionine. Reaction mixtures were analysed by radio-HPLC to quantify RCP and the relative proportion of each isoform. Results: Reactions performed without SnCl2 yielded very low RCP values (<5%), demonstrating its essential reducing role. Use of tricine alone or with antioxidant additives improved labelling efficiency but failed to generate a single species, with the main isoform accounting for only ~75% of total activity and unbound 99mTc remaining between 4-6%. Substitution of EDDA with alternative co-ligands, including nicotinic acid, systematically led to the formation of two isoforms in comparable proportions. Among all parameters tested, the buffer system was the most influential. The combination of 0.2 M sodium acetate buffer (pH 7) with EDDA, tricine, SnCl2, and iPSMA, followed by heating at 95 °C for 15 min, produced the best outcome, yielding an RCP >95% and a single dominant isoform (>92%). Similar results were obtained when the heating time was reduced to 7 min. Conclusion and Relevance: This study defines a robust and reproducible protocol for the preparation of 99mTc-iPSMA with high purity and isoform homogeneity. Optimised reaction conditions could be suitable for further development such as kitbased formulation and are currently being adapted for automated synthesis to facilitate clinical translation.

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Dates et versions

hal-05558648 , version 1 (18-03-2026)

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Jeanne Chillard, Léa Rubira, Marine M Cadet, Jade Torchio, Stéphane C Renaud, et al.. Optimising 99mTc-HYNIC-PSMA labelling to achieve a homogeneous isoform profile: a step toward a standardised kit-based formulation. EAHP Congress 2026,18-19-20 March 2026, Mar 2026, Barcelone, Spain. European Journal of Hospital Pharmacy, 33 (S1), pp.A35, 2026, ⟨10.1136/ejhpharm-2026-eahp.73⟩. ⟨hal-05558648⟩
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