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Fármacos utilizados em diagnóstico por tomografia por emissão de positrões (PET): situação atual e perspectivas futuras
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A tomografia por emissão de positrões (PET) é uma técnica não invasiva, que se baseia nos princípios da medicina nuclear e tem como fundamento a emissão de partículas β+. Durante décadas, tem-se atualizado, melhorando significativamente o diagnóstico, monitorização e terapia de diversas patologias.
Este trabalho aborda alguns dos radiofármacos utilizados em PET atualmente, e re-alça possibilidades de inovação que melhoram o desempenho no diagnóstico ou na terapêutica.
Um radiofármaco tem na sua constituição um fármaco compatível com o órgão ou tecido alvo a ser examinado, associado a um radionuclídeo como o 18F, 11C, 15O ou 13N que apresenta tempo de semi-vida (t1/2) curto e produzido num ciclotrão. Neste trabalho são abordados também radionuclídeos produzidos em geradores, o 68Ga, que apresenta um t1/2 maior e que revela características promissoras no respeitante ao diagnóstico de doenças como o cancro da próstata ou tumores neuroendócrinos.
O radiofármaco mais frequentemente utilizado é o 18F-FDG [2-desoxi-2-(18F) fluoro-D-glucose], um análogo da glucose, tendo uma vasta aplicação no diagnóstico de doenças do foro oncológico, em cardiologia ou em doenças neurológicas, baseando-se no aumento do metabolismo da glucose.
O radiofármaco 11C-metionina representa um bom indicador da presença de tumo-res, especialmente os cerebrais, baseando-se no aumento da síntese proteica.
Para deteção das recorrências do cancro da próstata, são utilizados os radiofárma-cos 11C-colina e o 18F-fluorocolina, mas o que apresenta uma maior especificidade no di-agnóstico, é o novo derivado de 68Ga: 68Ga-PSMA-11.
Os tumores neuroendócrinos são um desafio relativamente à deteção precoce, pelo que foram desenvolvidos radiofármacos derivados de 68Ga análogos aos recetores de so-matostatina, apresentando características promissoras tanto para o diagnóstico quanto para a terapêutica.
Têm surgido radiofármacos derivados do radionuclídeo 18F empregues na doença de Alzheimer tendo como alvo a deposição de placas β-amiloides; contudo, os novos ra-diofármacos orientados para a proteína tau representam uma ferramenta favorável no futuro do diagnóstico desta doença.
Em tempos de pandemia COVID-19, o uso da PET mostrou ser uma ferramenta adicional na deteção de situações inflamatórias, acreditando-se, por isso, que futuramente, esta técnica pode representar um método complementar no diagnóstico da infeção pelo vírus SARS-CoV-2.
Positron emission tomography (PET) is a non-invasive technique, which is based on the principles of nuclear medicine and is founded on the emission of β+ particles. For decades, it has been updated, significantly improving the diagnosis, monitoring and thera-py of various pathologies. This paper discusses some of the radiopharmaceuticals used in PET today and re-emphasizes possibilities for innovation that improve performance in diagnosis or therapeutics. A radiopharmaceutical has in its constitution a compatible drug with the target or-gan or tissue to be examined, associated with a radionuclide such as 18F, 11C, 15O or 13N that has a short half-life (t1/2) and produced in a cyclotron. This paper also discusses radi-onuclides produced in generators, 68Ga, which has a longer t1/2 and shows promising characteristics regarding the diagnosis of diseases such as prostate cancer or neuroendo-crine tumors. The most used radiopharmaceutical is 18F-FDG [2-deoxy-2-(18F) fluoro-D-glucose], a glucose analog, has a wide application in the diagnosis of oncological diseas-es, in cardiology or in neurological diseases, based on the increase of glucose metabolism. The radiopharmaceutical 11C-methionine represents a good indicator of the pres-ence of tumors, especially brain tumors, based on increased protein synthesis. For detection of prostate cancer recurrences, the radiopharmaceuticals 11C-choline and 11F-fluorocholine are used, but the one with the highest specificity in diagnosis is the new 68Ga derivative: 68Ga-PSMA-11. Neuroendocrine tumors are a challenge regarding early detection, so 68Ga-derived radiopharmaceuticals analogous to somatostatin receptors have been developed, showing promising features for both diagnosis and therapy. Radiopharmaceuticals derived from the 18F radionuclide used in Alzheimer's dis-ease targeting β-amyloid have emerged; however, new radiopharmaceuticals targeting the tau protein represent a favorable tool in the future diagnosis of this disease. In times of the COVID-19 pandemic, the use of PET has proven to be an addi-tional tool in the detection of inflammatory situations, and it is therefore believed that in the future, this technique may represent a complementary method in the diagnosis of SARS-CoV-2 infection.
Positron emission tomography (PET) is a non-invasive technique, which is based on the principles of nuclear medicine and is founded on the emission of β+ particles. For decades, it has been updated, significantly improving the diagnosis, monitoring and thera-py of various pathologies. This paper discusses some of the radiopharmaceuticals used in PET today and re-emphasizes possibilities for innovation that improve performance in diagnosis or therapeutics. A radiopharmaceutical has in its constitution a compatible drug with the target or-gan or tissue to be examined, associated with a radionuclide such as 18F, 11C, 15O or 13N that has a short half-life (t1/2) and produced in a cyclotron. This paper also discusses radi-onuclides produced in generators, 68Ga, which has a longer t1/2 and shows promising characteristics regarding the diagnosis of diseases such as prostate cancer or neuroendo-crine tumors. The most used radiopharmaceutical is 18F-FDG [2-deoxy-2-(18F) fluoro-D-glucose], a glucose analog, has a wide application in the diagnosis of oncological diseas-es, in cardiology or in neurological diseases, based on the increase of glucose metabolism. The radiopharmaceutical 11C-methionine represents a good indicator of the pres-ence of tumors, especially brain tumors, based on increased protein synthesis. For detection of prostate cancer recurrences, the radiopharmaceuticals 11C-choline and 11F-fluorocholine are used, but the one with the highest specificity in diagnosis is the new 68Ga derivative: 68Ga-PSMA-11. Neuroendocrine tumors are a challenge regarding early detection, so 68Ga-derived radiopharmaceuticals analogous to somatostatin receptors have been developed, showing promising features for both diagnosis and therapy. Radiopharmaceuticals derived from the 18F radionuclide used in Alzheimer's dis-ease targeting β-amyloid have emerged; however, new radiopharmaceuticals targeting the tau protein represent a favorable tool in the future diagnosis of this disease. In times of the COVID-19 pandemic, the use of PET has proven to be an addi-tional tool in the detection of inflammatory situations, and it is therefore believed that in the future, this technique may represent a complementary method in the diagnosis of SARS-CoV-2 infection.
Descrição
Trabalho Final de Mestrado Integrado, Ciências Farmacêuticas, 2021, Universidade de Lisboa, Faculdade de Farmácia.
Palavras-chave
PET Radionuclídeos Radiofármaco 18F-FDG Diagnóstico Mestrado integrado - 2021