RESUMO
In vivo receptor targeting with radiolabelled peptide-based probes is an attractive approach for the development of novel radiotracers for molecular imaging. This work presents the development and characterization of two novel neuropeptide Y analogues labelled with a positron emitter 68 Ga, for potential use in breast cancer imaging. Both analogues share the same amino acid sequence and were derivatized with NOTA through either a lysine linker (L1) or an acetylated lysine (L2). In both cases, a single product with radiochemical purity higher than 95% was obtained. The two complexes were hydrophilic, showed remarkable in vitro stability, good cellular uptake, binding affinity in the nanomolar range and high cellular internalization rate. Biodistribution studies revealed low blood uptake and elimination through the urinary tract. The addition of an acetyl group in the spacer increased the lipophilicity of C2 and modified the reactivity of the ε-amino group of the lysine which resulted in lower protein binding and lower percentage of injected dose in bladder and urine. The tumour versus muscle ratio was (3.8 ± 0.4) for 68 Ga-L1 and (4.7 ± 0.4) for 68 Ga-L2. These results encourage performing further studies in order to complete the evaluation of both tracers as potential radiopharmaceutical for breast cancer imaging.
Assuntos
Neoplasias da Mama/diagnóstico por imagem , Radioisótopos de Gálio/química , Neuropeptídeo Y/química , Compostos Radiofarmacêuticos/química , Aminas/química , Sequência de Aminoácidos , Animais , Transporte Biológico , Cinerradiografia , Feminino , Humanos , Lisina/química , Camundongos Nus , Neoplasias Experimentais , Neuropeptídeo Y/sangue , Neuropeptídeo Y/farmacocinética , Neuropeptídeo Y/urina , Ligação Proteica , Compostos Radiofarmacêuticos/sangue , Compostos Radiofarmacêuticos/farmacocinética , Compostos Radiofarmacêuticos/urina , Coloração e Rotulagem , Relação Estrutura-Atividade , Distribuição TecidualRESUMO
UNLABELLED: N,N-dimethyltryptamine (DMT), a strong psychodysleptic drug, has been found in higher plants, shamanic hallucinogenic beverages, and the urine of schizophrenic patients. The aim of this work was to gain better knowledge on the relationship between this drug and hallucinogenic processes by studying DMT behavior in comparison with tryptamine. METHODS: (131)I-labeled DMT and tryptamine were injected into rabbits. γ-Camera and biodistribution studies were performed. Brain uptake, plasma clearance, and renal excretion were assessed for each indolealkylamine. RESULTS: DMT and tryptamine showed different behavior when brain uptake, residence time, and excretion were compared. Labeled DMT entered the brain 10 s after injection, crossed the blood-brain barrier, and bound to receptors; then it was partially renally excreted. It was detected in urine within 24 h after injection and remained in the brain, even after urine excretion ceased; up to 0.1% of the injected dose was detected at 7 d after injection in the olfactory bulb. In contrast, tryptamine was rapidly taken up in the brain and fully excreted 10 min after injection. CONCLUSION: To our knowledge, this is the first demonstration that exogenous DMT remains in the brain for at least 7 d after injection. Although labeled DMT and tryptamine behave as agonists for at least 5-hydroxytryptamine 2A receptor, 5-hydroxytryptamine 2C receptor, trace amine-associated receptor, and σ-1 putative receptor targets, binding to the latter can explain the different behavior of labeled DMT and tryptamine in the brain. The persistence in the brain can be further explained on the basis that DMT and other N,N-dialkyltryptamines are transporter substrates for both the plasma membrane serotonin transporter and the vesicle monoamine transporter 2. Furthermore, storage in vesicles prevents DMT degradation by monoamine oxidase. At high concentrations, DMT is taken up by the serotonin transporter and further stored in vesicles by the vesicle monoamine transporter 2, to be released under appropriate stimuli. Moreover, the (131)I-labeling proved to be a useful tool to perform long-term in vivo studies.
Assuntos
N,N-Dimetiltriptamina/farmacocinética , Compostos Radiofarmacêuticos/farmacocinética , Triptaminas/farmacocinética , Animais , Encéfalo/diagnóstico por imagem , Encéfalo/metabolismo , Marcação por Isótopo , Rim/metabolismo , Lipídeos/química , Espectroscopia de Ressonância Magnética , N,N-Dimetiltriptamina/síntese química , N,N-Dimetiltriptamina/urina , Bulbo Olfatório/diagnóstico por imagem , Tomografia por Emissão de Pósitrons , Coelhos , Cintilografia , Compostos Radiofarmacêuticos/síntese química , Compostos Radiofarmacêuticos/urina , Receptores de Serotonina/efeitos dos fármacos , Solubilidade , Distribuição Tecidual , Triptaminas/síntese química , Triptaminas/urinaRESUMO
Monoclonal Antibody (mAb) ior C5 is a murine IgG(1) that recognizes the tumor associated antigen (TAA) ior C2, a cell surface O-linked glycoprotein carbohydrate chain not present in most normal tissues and homogeneously expressed in the cytoplasm of normal colon epithelium and heterogeneously expressed in more than 83% of primary colorectal carcinomas. This study was designed to investigate the pharmacokinetics, biodistribution and the absorbed radiation doses of (99m)Tc-labeled mAb ior C5 antibody in colorectal tumor patients. Ten patients were administered 3 mg of anti-O-linked glycoprotein carbohydrate chain TAA ior C2 murine monoclonal antibody ior C5 radiolabeled with (99m)Tc activity of 1435.0 +/- 123 MBq by intravenous (i.v.) bolus infusion. Blood and urine samples were collected from 4 out of 10 patients at timed intervals from 10 min and up to 24 h after injection of the (99m)Tc-labeled mAb ior C5 for pharmacokinetic studies. Whole body images were taken in 5 out of 10 patients for quantitative normal organ biodistribution and dosimetry studies and planar anterior and posterior and SPECT images were taken in 5 out of 10 patients for tumor localization. Mean absorbed doses were estimated using the methods developed by the Medical Internal Radiation Dose (MIRD) committee. The effective dose equivalent (EDE) and effective dose (ED) were calculated as prescribed in International Commission on Radiological Protection (ICRP) publications 30 and 60. Plasma disappearance curves of (99m)Tc-labeled murine antibody ior C5 were best fit by a two-compartment model in all patients with (t(1/2alpha)) of 4.32 +/- 2.18 h and (t(1/2beta) of 32.6 +/- 3.82 h. Among the main target organs, accumulation of the radiolabeled antibody was found in liver (9.38 +/- 0.80%), heart (8.92 +/- 0.94%) and spleen (1.37 +/- 0.30%) at 5 min post-administration. These values were reduced at 24 h to (5.91 +/- 0.73%) and (0.62 +/- 0.22%), respectively, for the heart and spleen and increased to (9.78 +/- 1.99%) for liver. Estimates of radiation absorbed dose to normal organs in rad/mCi administered were: whole body, 0.0181 +/- 0.0017; heart wall, 0.0768 +/- 0.0090; kidneys, 0.0530 +/- 0.0260; liver, 0.0565 +/- 0.0109 and spleen, 0.0540 +/- 0.0128. The effective dose equivalent and effective dose estimates for adults were 0.0314 +/- 0.0031 and 0.0249 +/- 0.0027 rem/mCi administered. This feasibility study indicates that the O-linked glycoprotein carbohydrate chain TAA ior C2 is expressed in primary and metastatic colorectal carcinomas and shows very limited expression in normal adult tissues. The very good pattern of biodistribution of (99m)Tc-labeled mAb ior C5 in patients will allow imaging of colorectal carcinoma lesions.
Assuntos
Anticorpos Monoclonais/farmacocinética , Neoplasias Colorretais/diagnóstico , Complemento C5/farmacocinética , Dosagem Radioterapêutica , Tecnécio/farmacocinética , Distribuição Tecidual , Idoso , Animais , Anticorpos Monoclonais/administração & dosagem , Antígenos Glicosídicos Associados a Tumores/química , Antígenos Glicosídicos Associados a Tumores/genética , Complemento C5/administração & dosagem , Cuba , Estudos de Viabilidade , Feminino , Meia-Vida , Corpo Humano , Humanos , Injeções Intravenosas , Masculino , Camundongos , Pessoa de Meia-Idade , Compostos Radiofarmacêuticos/administração & dosagem , Compostos Radiofarmacêuticos/sangue , Compostos Radiofarmacêuticos/urina , Tecnécio/administração & dosagemRESUMO
In nuclear medicine radiation absorbed doses are important in the patient's risk/benefit evaluation and are estimated by means of biological and complex mathematical models. The biological model includes radiopharmacokinetic data obtained through blood and urine samples taken at given intervals. A useful mathematical model is the MIRD model and with the value for the time of residence tau the MIRDOSE3 computer program uses several anatomic models and calculates radiation absorbed dose for 25 organs. At the Radiopharmacy Unit of the Nuclear Medicine Department at INCMNSZ two new bone seeking radiopharmaceuticals, 99mTc-ABP and 188Re-ABP, have been designed, characterized and animal-tested. Radiopharmaceutical parameters and sequential scanning were obtained for diagnostic 99mTc-ABP in 10 normal subjects and the aim was to use % 24 hour urine elimination and % bone uptake to calculate radiation absorbed dose and extrapolate the values to 188Re-ABP as the basis for a therapeutic treatment. 99mTc-ABP was eliminated in women's urine 63.2 +/- 7.3%/activity and 70 +/- 11%/activity in men. In women 36.8 +/- 7.3% of the radiopharmaceutical remains on the bone surface and in men 30 +/- 11%. ROIs were drawn on the images and the time-integrated renal cpm/pixel/ROI gave a residence time tau = 0.52 h. Cumulative bone activity A calculated with A = 1.443 (T1/2) A0 was 2358 +/- 469 MBq h for women and 1923 +/- 707 MBq h for men. Residence time tau was 3.19 +/- 0.63 h in women and 2.6 +/- 0.95 h in men. Radiation absorbed dose for the whole body was 0.0020 +/- 0.0004 mGy/MBq for women and 0.0013 +/- 0.0005 mGy/MBq for men. For women's bone marrow it was 0.0063 +/- 0.0013 mGy/MBq and for men 0.0041 +/- 0.0015 mGy/MBq. 188Re-ABP behaves as 99mTc-ABP therefore, the effective dose given by 188Re, a beta emitter, would be for women 0.0936 mSv/MBq and for men 0.0608 mSv/MBq. These characteristics and the radionuclidic characteristics of 188Re indicate that 188Re-ABP might be a good bone metastases pain palliation radiopharmaceutical.
Assuntos
Alendronato , Compostos de Organotecnécio , Doses de Radiação , Compostos Radiofarmacêuticos , Adulto , Alendronato/farmacocinética , Alendronato/urina , Algoritmos , Osso e Ossos/diagnóstico por imagem , Feminino , Humanos , Rim/diagnóstico por imagem , Masculino , Compostos de Organotecnécio/farmacocinética , Compostos de Organotecnécio/urina , Radiometria/métodos , Cintilografia , Compostos Radiofarmacêuticos/farmacocinética , Compostos Radiofarmacêuticos/urina , Distribuição TecidualRESUMO
Trinta e dois cäes submetidos a entubaçäo do ducto torácico e cateterismo bilateral dos ureteres, foram divididos em 3 grupos: A- 4 cäes inoculados com RISA 131 I ou EDTA 51 Cr por via intravenosa ou peri-prostática; B- controle de 8 cäes submetidos a irrigaçäo vesical e prostática com 8 litros de glicina a 1,2 por cento contendo os marcadores radioativos; C- 8 cäes manejados como em B mas sujeitos à RTU da próstata. Os cäes foram acompanhados por 5 horas. A absorçäo de líquido de irrigaçäo foi calculada pelos métodos volumétrico e radioisotópico. Em 5 horas, 97 por cento da RISA 131 I inoculada via intravenosa permanecia neste espaço enquanto apenas 4,6 por cento da injetada no espaço peri-prostático penetrou no compartimento vascular. Para o EDTA 51 Cr, 63,6 por cento da massa inoculada no espaço peri-prostático foi recuperada na urina após 5 horas. O método volumétrico mostrou absorçäo média de 22,7 ml no grupo B e 276 ml no C, e o radioisotópico de 6,3 ml e 165,4 ml, respectivamente. O modelo experimental tem similaridades com o ser humano
Assuntos
Animais , Cães , Absorção/fisiologia , Ácido Edético/farmacocinética , Compostos Radiofarmacêuticos/farmacocinética , Glicina/farmacocinética , Prostatectomia/efeitos adversos , Radioisótopos de Cromo/farmacocinética , Soroalbumina Radioiodada/farmacocinética , Compostos Radiofarmacêuticos/sangue , Compostos Radiofarmacêuticos/urina , Glicina/sangue , Glicina/urina , Radioisótopos de Cromo/sangue , Radioisótopos de Cromo/urina , Soroalbumina Radioiodada/sangue , Soroalbumina Radioiodada/urina , Sistema Linfático/fisiologia , Irrigação Terapêutica/efeitos adversosRESUMO
A study of 99mTc-adenosine-5'-diphosphate (99mTc-ADP) as a radiopharmaceutical for tumour diagnosis is presented. Two different labelling methods, using SnCl2 in alkaline solution and Zn as reducing agents, were developed. Reduction with Sn(II) alkaline solution was the selected method because a lower concentration of ADP (0.5 mg/mL) could be used and a higher radiochemical yield was achieved. A labelled molecule with a radiochemical purity higher than 95%, in vitro stability of at least 6 hours and an over all negative charge was obtained Biodistribution studies carried out in normal mice and rats revealed rapid urinary excretion and no specific accumulation of activity in any other particular organ. This behaviour was similar to that reported for 99mTc-adenosine-5'-triphosphate (99mTc-ATP). Rapid blood clearance, that could be fitted to a bicompartimental model, was also verified. No evidence of in vivo instability was observed. Studies in mice and rats bearing spontaneous mammary adenocarcinomas were performed and the results were compared to those from the 99mTc-ATP studies. Although the tumour models used were not the same, the incorporation of both labelled compounds was very similar. Radioactivity uptake in the tumour and the tumour-to-blood ratio were not notably high. However, a significant increment was observed in the tumour-to-muscle ratio (1.0 +/- 0.2 at 30 minutes to 2.7 +/- 0.4 at 240 minutes). Whole-body autoradiography enabled tumour visualization. Further investigations, including scintigraphic imaging, must be carried to complete the clinical evaluation of 99mTc-ADP as a tumour seeking agent.