Tafenoquina para tratamento de pacientes com malária por Plasmodium vivax / Tafenoquine for the treatment of patients with Plasmodium vivax malaria

CONITEC CONTEXTO: A malária é uma doença infecciosa parasitária aguda causada por protozoários do gênero Plasmodium, transmitidos ao homem pela picada da fêmea do mosquito Anopheles darlingi. O período de incubação da condição varia de 7 a 14 dias e a crise aguda é caracterizada por episódios de calafrios, febre e sudorese, geralmente acompanhados de cefaleia, mialgia, náuseas e vômitos. De acordo com o Relatório Mundial da Malária, 228 milhões de casos foram reportados, no ano de 2019, representando um grave problema de saúde pública para o mundo. No Brasil, a área endêmica compreende a região amazônica brasileira. Em 2019, foram notificadas no território nacional 157.454 casos de malária, uma redução de 19,1% em relação a 2018, quando foram registrados 194.572 casos da doença. Já a deficiência de glicose-6-fosfato desidrogenase (G6PD) é uma anomalia hereditária ligada ao cromossomo X, que acomete majoritariamente homens (hemizigóticos). Estima-se que afeta aproximadamente 400 milhões de pessoas em todo o mundo e a prevalência varia de 5% a 25% em áreas endêmicas, como África, Oriente Médio e Ásia. Essa enzima desempenha papel importante na sobrevivência dos eritrócitos: está envolvida na via da pentose fosfato (PPP) e fornece NADPH (nicotina adenina dinucleótido fosfato reduzido) e GSH (glutationa reduzida). GSH pode reagir com peróxido de hidrogênio (H2O2) e reduzir para H2O. Isso ajuda a proteger os eritrócitos de espécies reativas de oxigênio, que resultam em estresse oxidativo e consequentemente, hemólise. A principal preocupação de segurança com relação à tafenoquina é o alto risco de anemia hemolítica aguda (AHA) em pacientes com deficiência de G6PD (atividade da enzima < 30% do normal), que pode resultar em óbitos em indivíduos com menos de 10% da atividade enzimática normal. TECNOLOGIA: Tafenoquina (Kozenis®). PERGUNTAS DE PESQUISA: A tafenoquina 300 mg em dose única é eficaz e segura para cura radical (prevenção de recidiva) da malária por Plasmodium vivax? O teste quantitativo da atividade da enzima glicose-6-fosfato desidrogenase (G6PD) é sensível e específico na detecção da atividade da G6PD em pacientes com diagnóstico confirmado de malária por Plasmodium vivax? EVIDÊNCIAS CIENTÍFICAS: Foram incluídos dois estudos no corpo da evidência, duas revisões sistemáticas com meta-análise, de qualidade da evidência moderada a grave. No que tange às evidências que respondem à primeira pergunta de pesquisa, referente ao medicamento, para os desfechos avaliados nos grupos tafenoquina versus nenhum tratamento antihipinozoíto: tafenoquina reduziu a recidiva em comparação com não tratamento (RR 0,32, IC 95% 0,12 a 0,88); não houve mortes durante acompanhamento; não foram encontradas diferenças significativas entre tafenoquina e nenhum tratamento anti-hipnozoíto (RR 1,34, IC 95% 0,63 a 2,84) e não foram observadas diferença entre os grupos avaliados em relação ao número ou tipo de eventos adversos relatados com exceção de dor de cabeça. O grupo tratado com tafenoquina mais cloroquina demonstrou pouca ou nenhuma diferença na ocorrência geral de eventos adversos em comparação com cloroquina isolada (RR 0,96, IC 95% 0,81 a 1,13). Para o desfechos avaliados que compararam tafenoquina versus primaquina: não foi identificada diferença estatisticamente significativa na prevenção de recaídas entre os pacientes dos tratamentos (RR 1,04, IC 95% 0,8 a 1,34), assim, tafenoquina é possivelmente tão eficaz quanto primaquina; também não foi identificada diferença estatisticamente significativa entre os tratamentos em pacientes sem deficiência de G6PD; entre os EA mais comuns estão a queda no nível de hemoglobina e prolongamento QT assintomático (RR 1,41, IC 95% 0,70 a 2,83); para avaliação de qualquer evento adverso tafenoquina não apresentou diferença em todos os tipos de EA em comparação com primaquina, incluindo anemia e queda do nível de hemoglobina (RR 1,01, IC 95% 0,89 a 1,14). Para avaliação da acurácia do teste quantitativo de G6PD, a sensibilidade combinada do teste foi de 0,96 (IC 95% 0,90 a 0,99) e a especificidade combinada foi de 0,95 (IC 95% 0,92 a 0,96), sendo que o desempenho combinado não variou significativamente, independentemente do tipo de amostra sanguínea. CONSIDERAÇÕES: Com nível de certeza moderado, a dose única de tafenoquina 300 mg não teve diferença significativa quando comparado com o tratamento de primaquina 15 mg/dia por 14 dias. Também não foi identificada diferença significativa em relação aos eventos adversos graves e gerais entre os outros grupos comparadores, com uma certeza de evidência moderada a alta. O perfil de segurança dos dois tratamentos foi semelhante e ambos causaram declínios no nível de hemoglobina, no entanto de fácil manejo, entre os pacientes com atividade normal da enzima G6PD. Também com nível de certeza da evidência moderado, o teste quantitativo de atividade da enzima G6PD performou valores de sensibilidade e especificidade maiores que 95%. As razões de verossimilhança positiva e negativa sugerem que o teste é adequado para confirmação da atividade da enzima, bem como auxilia na exclusão de casos em que há deficiência de G6PD em um limiar de 30% de atividade enzimática. RECOMENDAÇÃO PRELIMINAR DA CONITEC: Diante do exposto, a Conitec, em sua 94ª reunião ordinária, realizada no dia 04 de fevereiro de 2021, deliberou que a matéria fosse disponibilizada em consulta pública com recomendação preliminar favorável à incorporação, no SUS, da tafenoquina para o tratamento, ou cura radical, de malária causada pelo Plasmodium vivax em pacientes com 16 anos de idade ou mais e atividade enzimática maior que 70% de glicose-6-fosfato desidrogenase (G6PD), confirmada por meio de teste rápido validado. Os membros do plenário concordaram que, embora a evidência de eficácia disponível em literatura tenha sido avaliada de boa qualidade, esta apresenta dados modestos, se considerado o principal desfecho que avalia o desempenho da tafenoquina versus primaquina. Para tanto, faz-se necessária a obtenção de dados de efetividade que serão coletados após condução do estudo observacional TRuST, focalizado nas cidades de Manaus e Porto Velho. A matéria foi disponibilizada em consulta pública. CONSULTA PÚBLICA: A Consulta Pública nº 04/2021 foi realizada entre os dias 08/02/2021 a 1º/03/2021. Foram recebidas 87 contribuições, sendo 32 pelo formulário para contribuições técnico-científicas e 55 pelo formulário para contribuições sobre experiência ou opinião de pacientes, familiares, amigos ou cuidadores de pacientes, profissionais de saúde ou pessoas interessadas no tema. As contribuições recebidas foram majoritariamente a favor da recomendação preliminar da Conitec, de incorporação de uso das tecnologias no SUS. RECOMENDAÇÃO FINAL: Os membros do plenário presentes na 95ª reunião ordinária da Conitec, no dia 03 de março de 2021, deliberaram, por unanimidade, recomendar a incorporação da tafenoquina para o tratamento, ou cura radical, de malária causada pelo Plasmodium vivax em pacientes com 16 anos de idade ou mais e atividade enzimática de glicose-6- fosfato desidrogenase (G6PD) maior que 70%, confirmada por meio de teste rápido quantitativo de G6PD. A recomendação para incorporação do medicamento está condicionada à apresentação de dados de mundo real ao final do estudo de 12 meses. Cabe informar que não foram adicionadas na consulta pública referências que alterassem a análise da evidência apresentada no relatório preliminar. Foi assinado o Registro de Deliberação nº 591/2021. DECISÃO: Incorporar a tafenoquina para tratamento de pacientes com malária por Plasmodium vivax condicionada à apresentação de dados de mundo real ao final do estudo, do Sistema Único de Saúde - SUS, conforme Portaria nº 07, publicada no Diário Oficial da União nº 48, seção 1, página 170, em 12 de março de 2021.

Levels of primaquine and carboxyprimaquine in patients with malaria vivax from the Brazilian Amazon basin.

In the last two years, a substantial increase in the number of malaria vivax cases has occurred in the Brazilian Amazon basin. The adequate exposure of hypnozoites to primaquine is a matter of interest as these dormant forms are responsible for the maintenance or even the increase of malaria burden in endemic areas. The aim of this study was to estimate the levels of primaquine and carboxyprimaquine in whole blood samples of patients with P. vivax treated with chloroquine and an abbreviated regimen of primaquine (0.5 mg/kg/d for 7 days), with adequate clinical and parasitological outcomes after 180 days of follow-up. A total of 40 male patients met the criteria for inclusion in the study. Primaquine and carboxyprimaquine were measured by high-performance liquid chromatography. The levels of primaquine in whole blood samples ranged from 40-238 ng/mL, 42-196 ng/mL and 42-150 ng/mL on days 1, 3 and 7. The levels of carboxyprimaquine in whole blood samples ranged from 87-234 ng/mL, 96-252 ng/mL and 74-448 ng/mL on days 1, 3 and 7. These data provide a reliable estimation of exposure of the infecting parasite to primaquine. Based on the regional pattern of relapse, the estimated blood levels of primaquine can be considered effective against hypnozoites of the local circulating strains of P. vivax.

Novel antimalarial chloroquine- and primaquine-quinoxaline 1,4-di-N-oxide hybrids: Design, synthesis, Plasmodium life cycle stage profile, and preliminary toxicity studies.

Emergence of drug resistance and targeting all stages of the parasite life cycle are currently the major challenges in antimalarial chemotherapy. Molecular hybridization combining two scaffolds in a single molecule is an innovative strategy for achieving these goals. In this work, a series of novel quinoxaline 1,4-di-N-oxide hybrids containing either chloroquine or primaquine pharmacophores was designed, synthesized and tested against both chloroquine sensitive and multidrug resistant strains of Plasmodium falciparum. Only chloroquine-based compounds exhibited potent blood stage activity with compounds 4b and 4e being the most active and selective hybrids at this parasite stage. Based on their intraerythrocytic activity and selectivity or their chemical nature, seven hybrids were then evaluated against the liver stage of Plasmodium yoelii, Plasmodium berghei and Plasmodium falciparum infections. Compound 4b was the only chloroquine-quinoxaline 1,4-di-N-oxide hybrid with a moderate liver activity, whereas compound 6a and 6b were identified as the most active primaquine-based hybrids against exoerythrocytic stages, displaying enhanced liver activity against P. yoelii and P. berghei, respectively, and better SI values than primaquine. Although both primaquine-quinoxaline 1,4-di-N-oxide hybrids slightly reduced the infection of mosquitoes, they inhibited sporogony of P. berghei and compound 6a showed 92% blocking of transmission. In vivo liver efficacy assays revealed that compound 6a showed causal prophylactic activity affording parasitaemia reduction of up to 95% on day 4. Absence of genotoxicity and in vivo acute toxicity were also determined. These results suggest the approach of primaquine-quinoxaline 1,4-di-N-oxide hybrids as new potential dual-acting antimalarials for further investigation.

Primaquine-thiazolidinones block malaria transmission and development of the liver exoerythrocytic forms.

BACKGROUND: Primaquine is an anti-malarial used to prevent Plasmodium vivax relapses and malaria transmission. However, PQ metabolites cause haemolysis in patients deficient in the enzyme glucose-6-phosphate dehydrogenase (G6PD). Fifteen PQ-thiazolidinone derivatives, synthesized through one-post reactions from primaquine, arenealdehydes and mercaptoacetic acid, were evaluated in parallel in several biological assays, including ability to block malaria transmission to mosquitoes. RESULTS: All primaquine derivatives (PQ-TZs) exhibited lower cell toxicity than primaquine; none caused haemolysis to normal or G6PD-deficient human erythrocytes in vitro. Sera from mice pretreated with the test compounds thus assumed to have drug metabolites, caused no in vitro haemolysis of human erythrocytes, whereas sera from mice pretreated with primaquine did cause haemolysis. The ability of the PQ-TZs to block malaria transmission was evaluated based on the oocyst production and percentage of mosquitoes infected after a blood meal in drug pre-treated animals with experimental malaria caused by either Plasmodium gallinaceum or Plasmodium berghei; four and five PQ-TZs significantly inhibited sporogony in avian and in rodent malaria, respectively. Selected PQ-TZs were tested for their inhibitory activity on P. berghei liver stage development, in mice and in vitro, one compound (4m) caused a 3-day delay in the malaria pre-patent period. CONCLUSIONS: The compound 4m was the most promising, blocking malaria transmissions and reducing the number of exoerythrocytic forms of P. berghei (EEFs) in hepatoma cells in vitro and in mice in vivo. The same compound also caused a 3-day delay in the malaria pre-patent period.

Structure-based de novo design, molecular docking and molecular dynamics of primaquine analogues acting as quinone reductase II inhibitors.

Primaquine is a traditional antimalarial drug with low parasitic resistance and generally good acceptance at higher doses, which has been used for over 60 years in malaria treatment. However, several limitations related to its hematotoxicity have been reported. It is believed that this toxicity comes from the hydroxylation of the C-5 and C-6 positions of its 8-aminoquinoline ring before binding to the molecular target: the quinone reductase II (NQO2) human protein. In this study we propose primaquine derivatives, with substitution at position C-6 of the 8-aminoquinoline ring, planned to have better binding to NQO2, compared to primaquine, but with a reduced toxicity related to the C-5 position being possible to be oxidized. On this sense the proposed analogues were suggested in order to reduce or inhibit hydroxylation and further oxidation to hemotoxic metabolites. Five C-6 substituted primaquine analogues were selected by de novo design and further submitted to docking and molecular dynamics simulations. Our results suggest that all analogues bind better to NQO2 than primaquine and may become better antimalarials. However, the analogues 3 and 4 are predicted to have a better activity/toxicity balance.

Evaluation of antimalarial activity and toxicity of a new primaquine prodrug.

Plasmodium vivax is the most prevalent of the five species causing malaria in humans. The current available treatment for P. vivax malaria is limited and unsatisfactory due to at least two drawbacks: the undesirable side effects of primaquine (PQ) and drug resistance to chloroquine. Phenylalanine-alanine-PQ (Phe-Ala-PQ) is a PQ prodrug with a more favorable pharmacokinetic profile compared to PQ. The toxicity of this prodrug was evaluated in in vitro assays using a human hepatoma cell line (HepG2), a monkey kidney cell line (BGM), and human red blood cells deficient in the enzyme glucose-6-phosphate-dehydrogenase (G6PD). In addition, in vivo toxicity assays were performed with rats that received multiple doses of Phe-Ala-PQ to evaluate biochemical, hematological, and histopathological parameters. The activity was assessed by the inhibition of the sporogonic cycle using a chicken malaria parasite. Phe-Ala-PQ blocked malaria transmission in Aedes mosquitoes. When compared with PQ, it was less cytotoxic to BGM and HepG2 cells and caused less hemolysis of G6PD-deficient red blood cells at similar concentrations. The prodrug caused less alteration in the biochemical parameters than did PQ. Histopathological analysis of the liver and kidney did show differences between the control and Phe-Ala-PQ-treated groups, but they were not statistically significant. Taken together, the results highlight the prodrug as a novel lead compound candidate for the treatment of P. vivax malaria and as a blocker of malaria transmission.

In vitro and in vivo evaluation of a primaquine prodrug without red blood cell membrane destabilization property.

Primaquine is an important therapeutic resource for malaria treatment and it has wide activity against several pathogens. The haematotoxicity of primaquine is the major problem for its therapeutic application. This effect is aggravated by repeated use at high doses and by the wide fluctuation of plasma levels after administration. The primaquine prodrug (Phe-Ala-PQ) was planned in order to modify the pharmacokinetics and toxicity of primaquine. The in vitro conversion of Phe-Ala-PQ to primaquine, and the primaquine pharmacokinetics were evaluated in four groups of rats: two groups that received a single dose of Phe-Ala-PQ, one by intravenous and the other by gavage route, and two other groups that received primaquine diphosphate, by intravenous and gavage routes. In addition, the erythrocyte osmotic fragility was compared in two groups of rats that received multiple doses of primaquine diphosphate or Phe-Ala-PQ, as a parameter of haematotoxicity. The in vitro conversion of Phe-Ala-PQ to primaquine by plasma enzyme action was observed. The pharmacokinetic profile of primaquine from Phe-Ala-PQ was more favourable due to the lower fluctuation of plasma concentrations. Haematotoxicity was not evidenced in the prodrug administration. The results reinforce the need for further studies with this prodrug, promising an alternative in the therapeutic use of primaquine.

Enantioselective analysis of primaquine and its metabolite carboxyprimaquine by capillary electrophoresis.

An enantioselective capillary electrophoresis method for the simultaneous determination of primaquine (PQ) and carboxyprimaquine (CPQ) in rat liver mitochondrial fraction, suitable for in vitro metabolism studies is presented. The drug and metabolite were extracted by liquid-liquid extraction using ethyl ether. The enantiomers were resolved in a fused-silica capillary, 50 microm inside diameter (ID) and 24 cm of effective length, using an electrolyte solution consisting of a 20 mmol/L sodium phosphate solution, pH 3.0, and 10% w/v maltodextrin. Hydrodynamic sample injection was used with a 10 s injection time at 50 mbar pressure. The applied voltage was 22 kV and the capillary temperature was controlled at 20 degrees C. Detection was carried out at 264 nm. Under these conditions, the enantiomeric fractions of the drug and of its metabolite were analyzed within 6 min. The extraction procedure was efficient in removing endogenous interferents and low values (<10%) for the coefficients of variation and deviation from theoretical values were demonstrated for both within-day and between-day assays. The method described allows the determination of PQ and CPQ enantiomers as low as 100 and 40 ng/mL, respectively. After validation, the method was used for an in vitro metabolism study of PQ. The results showed that the enantiomer (-)-PQ was preferentially metabolized to (-)-CPQ.

Synthesis and in vitro evaluation of potential antichagasic dipeptide prodrugs of primaquine.

American trypanosomiasis (Chagas' disease) is an endemic parasitic disease afflicting more than 20 million people in Latin America. Currently, therapy is unsatisfactory and only two drugs are available. Primaquine, an antimalarial drug, has trypanocidal activity. Dipeptide derivatives of primaquine, Phe-Arg-PQ, Lys-Arg-PQ, and Phe-Ala-PQ, were synthesized. The choice of the peptides was based on the primary specificity of cruzipain, the major cysteine proteinase from T cruzi. The prodrugs obtained were tested on the LLC-MK2 cell culture infected with trypomastigotes forms of T. cruzi. Phe-Arg-PQ, Lys-Arg-PQ, and Phe-Ala-PQ were active in all stages.

Oxidative activity of primaquine metabolites on rat erythrocytes in vitro and in vivo.

The oxidative activities of primaquine [6-methoxy-8-(4-amino-1-methylbutylamino)quinoline] and its metabolites, the quinone-imine derivatives of 5-hydroxyprimaquine [5-hydroxy-6-methoxy-8-(4-amino-1-methylbutylamino)quinoline] and 5-hydroxydemethylprimaquine [5-hydroxy-6-demethyl-8-(4-amino-1-methylbutylamino)quinoline], 6-methoxy-8-amino quinoline and hydrogen peroxide, were studied on rat erythrocytes in vitro and in vivo. In both cases, the most effective metabolites in oxidizing hemoglobin and depleting non-protein sulfhydryl groups from erythrocytes were the quinone-imine derivatives of the ring-hydroxylated metabolites, 5-hydroxyprimaquine and 5-hydroxydemethyl-primaquine. The latter quinone-imines were shown by light absorption spectroscopy and oxygen consumption studies to be able to oxidize purified rat hemoglobin to methemoglobin but to be unable to react directly with reduced glutathione. In agreement with these results, no radical adduct was detected by electron paramagnetic resonance spectroscopy in incubations of rat erythrocytes with the quinone-imines and the spin-trap 5,5-dimethyl-1-pyrroline-N-oxide; metabolite-derived free radicals were detected instead. Taken together, the results suggest that 5-hydroxyprimaquine and 5-hydroxydemethylprimaquine are important metabolites in the expression of primaquine hemotoxicity, in contrast to 6-methoxy-8-aminoquinoline. Additionally, the results indicate that hydrogen peroxide is the ultimate oxidant formed from the ring-hydroxylated metabolites by redox-cycling of the corresponding quinone-imine derivatives both in vitro and in vivo.

ESR detection of free radical intermediates during autoxidation of 5-hydroxyprimaquine.

Autoxidation of 5-hydroxyprimaquine, a putative metabolite of the antimalarial primaquine, was studied by oxygen consumption and ESR spectroscopy. 5-Hydroxyprimaquine underwent fast autoxidation under mild conditions (pH 7.4-8.5, 25 degrees C, and presence of 1 mM diethylenetriamine pentaacetic acid); each mol of the drug consumed 0.75 mol of oxygen and formed 0.5 mol of hydrogen peroxide. Direct-ESR experiments demonstrated that 5-hydroxyprimaquine autoxidation was accompanied by generation of a drug-derived free radical that is oxygen sensitive. Generation of hydroxyl radical was also established by spin-trapping experiments in the presence of 5,5-dimethyl-1-pyrroline N-oxide. The effect of antioxidant enzymes on hydroxyl radical adduct yield and analysis of autoxidation stoichiometry suggest that the main route for hydroxyl radical generation is the iron-catalyzed reaction between the drug-derived free radical and hydrogen peroxide.