Sergio Todde

Guidance on current good radiopharmacy practice (cGRPP) for the small-scale preparation of radiopharmaceuticals

This guidance is meant as a guidance to Part B of the EANM “Guidelines on Good Radiopharmacy Practice (GRPP)” issued by the Radiopharmacy Committee of the EANM (see www.eanm.org), covering the small-scale “in house” preparation of radiopharmaceuticals which are not kit procedures. The aim is to provide more detailed and practice-oriented guidance to those who are involved in the small-scale preparation of, for example, PET, therapeutic or other radiopharmaceuticals which are not intended for commercial purposes or distribution.

18F-FDG PET/CT can predict nodal metastases but not recurrence in early stage uterine cervical cancer

OBJECTIVES To evaluate the role of the metabolic characteristics of cervical tumor uptake as predictors of a) lymph node (LN) metastases, b) recurrence, in the preoperative staging of early-stage cervical cancer. METHODS 89 patients with FIGO stage IB1 and IIA<4 cm cervical cancer were imaged with FDG-PET/CT before radical hysterectomy and pelvic lymphadenectomy. PET/CT images were analyzed and correlated to histological findings. Maximum and mean standardized uptake value (SUVmax, SUVmean), metabolic tumor volume (MTV), total lesion glycolysis (TLG) of cervical lesions were calculated by an iterative adaptive algorithm. These parameters were correlated to the presence of: a) LN metastases, b) relapse after primary treatment. RESULTS Out of the 89 patients who underwent preoperative PET/CT scan for staging purpose, 16 were negative at cervical level: they were all pN0 and without recurrence during follow-up (mean 34.1±14.5 months). In 69 patients MTV and TLG were significantly higher (p=0.0006 and p=0.03) in pN1 patients in comparison to pN0 patients, while SUV values did not show significant differences between the two groups. No significant correlations were found between SUVmax, SUVmean, MTV, TLG and the evidence of relapse (mean follow-up 29.2±15.5 months). CONCLUSIONS In early-stage cervical cancer MTV and TLG correlate with the presence of nodal metastases, but their clinical impact on patients management has to be clarified. The absence of pathological cervical uptake could be a good prognostic factor, while SUVmax, SUVmean, MTV, TLG of the cervical uptake have not been found predictors of recurrence.

VEGF-Targeted Therapy Stably Modulates the Glycolytic Phenotype of Tumor Cells

Anti-VEGF therapy perturbs tumor metabolism, severely impairing oxygen, glucose, and ATP levels. In this study, we investigated the effects of anti-VEGF therapy in multiple experimental tumor models that differ in their glycolytic phenotypes to gain insights into optimal modulation of the metabolic features of this therapy. Prolonged treatments induced vascular regression and necrosis in tumor xenograft models, with highly glycolytic tumors becoming treatment resistant more rapidly than poorly glycolytic tumors. By PET imaging, prolonged treatments yielded an increase in both hypoxic and proliferative regions of tumors. A selection for highly glycolytic cells was noted and this metabolic shift was stable and associated with increased tumor aggressiveness and resistance to VEGF blockade in serially transplanted mice. Our results support the hypothesis that the highly glycolytic phenotype of tumor cells studied in xenograft models, either primary or secondary, is a cell-autonomous trait conferring resistance to VEGF blockade. The finding that metabolic traits of tumors can be selected by antiangiogenic therapy suggests insights into the evolutionary dynamics of tumor metabolism.

Automated production of copper radioisotopes and preparation of high specific activity [64Cu]Cu-ATSM for PET studies

(60)Cu and (64)Cu are useful radioisotopes for positron emission tomography (PET) radiopharmaceuticals and may be used for the preparation of promising agents for diagnosis and radiotherapy. In this study, the production and purification of (60/64)Cu starting from (60/64)Ni using a new automated system, namely Alceo, is described. A dynamic process for electrodeposition and dissolution of (60/64)Ni/(60/64)Cu was developed. Preliminary production yields of (60)Cu and (64)Cu were 400 and 300mCi, respectively. (64)Cu was used to radiolabel the hypoxia detection tracer ATSM with a specific activity of 2.2+/-1.3Ci/micromol.

Preparation of [11C] radioligands with high specific radioactivity on a commercial PET tracer synthesizer

High specific radioactivity is required for receptor studies with PET. Hereby we wish to report our experience using Nuclear Interface PET Tracer Synthesizer for preparation of Carbon-11 radioligands and modules modifications, which allowed to achieve high specific radioactivity.

Asymmetric synthesis and preliminary evaluation of (R)- and (S)-[11C]bisoprolol, a putative β1-selective adrenoceptor radioligand

(+/-)-1-[4-(2-Isopropoxyethoxymethyl)-phenoxy]-3-isopropylamino-2-propanol (bisoprolol) is a potent, clinically used beta(1)-adrenergic agent. (R)-(+) and (S)-(-) enantiomers of bisoprolol were labelled with carbon-11 (t(1/2)=20.4 min) as putative tracers for the non-invasive assessment of the beta(1)-adrenoceptor subtype in the human heart and brain with positron emission tomography (PET). The radiosynthesis consisted of reductive alkylation of des-iso-propyl precursor with [2-11C]acetone in the presence of sodium cyanoborohydride and acetic acid. The stereo-conservative synthesis of (R)-(+) and (S)-(-)-1-[4-(2-isopropoxyethoxymethyl)-phenoxy]-3-amino-2-propanol to be used as the precursors for the radiosynthesis of [11C]bisoprolol enantiomers was readily accomplished by the use of the corresponding chiral epoxide in three steps starting from the commercially available hydroxybenzyl alcohol. The final labelled product (either (+) or (-)-1-[4-(-isopropoxyethoxymethyl)-phenoxy]-3- [11C]isopropylamino-2-propanol) was obtained in 99% radiochemical purity in 30 min with 15+/-5% (EOS, non-decay corrected) radiochemical yield and 3.5+/-1 Ci/micromol specific radioactivity. Preliminary biological evaluation of the tracer in rats showed that about 30% of heart uptake of [11C](S)-bisoprolol is due to specific binding. The high non-specific uptake in lung might mask the heart uptake, thus precluding the use of [11C](S)-bisoprolol for heart and lung studies by PET. The remarkably high uptake of the tracer in rat brain areas rich of beta-adrenergic receptors such as pituitary (1.8+/-0.3% I.D. at 30 min) was blocked by pre-treatment with the beta-adrenergic antagonists propranolol (45%) and bisoprolol (51%, p<0.05). [11C](S)-bisoprolol deserves further evaluation in other animal models as a putative beta(1) selective radioligand for in vivo investigation of central adrenoceptors.

Automation of [11C]acyl chloride syntheses using commercially available 11C-modules.

In implementing published procedures for the incorporation of [11C]carbon dioxide on the immobilized Grignard reagents for the radiosynthesis of [11C]acyl chlorides, several modifications on a commercial PET tracer synthesizer module for 11C-methylations were made to obtain reliable and reproducible production processes for routine clinical applications. High yields of [carbonyl-11C]WAY-100635 and [11C]zofenoprilat were obtained via 11C-carboxylation using [carbonyl-11C]cyclohexanecarbonyl chloride and 2-methyl-[l-11C]acryloyl chloride prepared with the modified module.

High yield synthesis of [11C]-acetone through selective quenching of methyl lithium.

Carbon-11 labeled acetone is a useful radiosynthetic precursor. Previously, strict control of no-carrier-added stoichiometry was required to prepare it from reaction of CO2 and methyl lithium. However, excess methyl lithium may be selectively quenched to avoid reaction with nascent acetone to give tert-butanol. We report a simple pKa-based strategy to sequentially and selectively quench MeLi and acetone to give yields of up to 100% acetone even in the presence of a large excess of MeLi. The method gives good yields of acetone under conditions that previously precluded its synthesis.

EANM guideline for the preparation of an Investigational Medicinal Product Dossier (IMPD)

The preparation of an Investigational Medicinal Product Dossier (IMPD) for a radiopharmaceutical to be used in a clinical trial is a challenging proposition for radiopharmaceutical scientists working in small-scale radiopharmacies. In addition to the vast quantity of information to be assembled, the structure of a standard IMPD is not well suited to the special characteristics of radiopharmaceuticals. This guideline aims to take radiopharmaceutical scientists through the practicalities of preparing an IMPD, in particular giving advice where the standard format is not suitable. Examples of generic IMPDs for three classes of radiopharmaceuticals are given: a small molecule, a kit-based diagnostic test and a therapeutic radiopharmaceutical.

Synthesis and in vivo evaluation of [11C]CGP62349, a new GABAB receptor antagonist

Abstract This paper describes the radiosynthesis of [11C]CGP62349, a potential ligand to assess GABAB receptors in vivo. 11C was introduced by O-methylation of the corresponding des-methyl precursor, namely CGP67780. The final product was obtained with a reliable method in good yield. The radioligand was tested in monkey, revealing negligible blood-brain barrier penetration and brain uptake, thus prompting us to search for a new target structure with a better lipophilicity.