RESUMO
Prevention of infection and propagation of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a high priority in the Coronavirus Disease 2019 (COVID-19) pandemic. Here we describe S-nitrosylation of multiple proteins involved in SARS-CoV-2 infection, including angiotensin-converting enzyme 2 (ACE2), the receptor for viral entry. This reaction prevents binding of ACE2 to the SARS-CoV-2 spike protein, thereby inhibiting viral entry, infectivity and cytotoxicity. Aminoadamantane compounds also inhibit coronavirus ion channels formed by envelope (E) protein. Accordingly, we developed dual-mechanism aminoadamantane nitrate compounds that inhibit viral entry and, thus, the spread of infection by S-nitrosylating ACE2 via targeted delivery of the drug after E protein channel blockade. These non-toxic compounds are active in vitro and in vivo in the Syrian hamster COVID-19 model and, thus, provide a novel avenue to pursue therapy.
Assuntos
COVID-19 , Humanos , SARS-CoV-2/metabolismo , Enzima de Conversão de Angiotensina 2/metabolismo , Ligação Proteica , Peptidil Dipeptidase A/metabolismoRESUMO
Infection with Cryptosporidium spp. can cause severe diarrhea, leading to long-term adverse impacts and even death in malnourished children and immunocompromised patients. The only FDA-approved drug for treating cryptosporidiosis, nitazoxanide, has limited efficacy in the populations impacted the most by the diarrheal disease, and safe, effective treatment options are urgently needed. Initially identified by a large-scale phenotypic screening campaign, the antimycobacterial therapeutic clofazimine demonstrated great promise in both in vitro and in vivo preclinical models of Cryptosporidium infection. Unfortunately, a phase 2a clinical trial in HIV-infected adults with cryptosporidiosis did not identify any clofazimine treatment effect on Cryptosporidium infection burden or clinical outcomes. To explore whether clofazimine's lack of efficacy in the phase 2a trial may have been due to subtherapeutic clofazimine concentrations, a pharmacokinetic/pharmacodynamic modeling approach was undertaken to determine the relationship between clofazimine in vivo concentrations and treatment effects in multiple preclinical infection models. Exposure-response relationships were characterized using Emax and logistic models, which allowed predictions of efficacious clofazimine concentrations for the control and reduction of disease burden. After establishing exposure-response relationships for clofazimine treatment of Cryptosporidium infection in our preclinical model studies, it was unmistakable that the clofazimine levels observed in the phase 2a study participants were well below concentrations associated with anti-Cryptosporidium efficacy. Thus, despite a dosing regimen above the highest doses recommended for mycobacterial therapy, it is very likely the lack of treatment effect in the phase 2a trial was at least partially due to clofazimine concentrations below those required for efficacy against cryptosporidiosis. It is unlikely that clofazimine will provide a remedy for the large number of cryptosporidiosis patients currently without a viable treatment option unless alternative, safe clofazimine formulations with improved oral absorption are developed. (This study has been registered in ClinicalTrials.gov under identifier NCT03341767.).
Assuntos
Antiprotozoários , Criptosporidiose , Cryptosporidium , Adulto , Antiprotozoários/farmacologia , Antiprotozoários/uso terapêutico , Criança , Clofazimina/farmacologia , Clofazimina/uso terapêutico , Criptosporidiose/tratamento farmacológico , Diarreia/tratamento farmacológico , HumanosRESUMO
A variable region fusion strategy was used to generate an immunosuppressive antibody based on a novel "stalk-knob" structural motif in the ultralong complementary-determining region (CDR) of a bovine antibody. The potent Kv1.3 channel inhibitory peptides Moka1-toxin and Vm24-toxin were grafted into different CDRs of the humanized antibodies BVK and Synagis (Syn) using both ß-sheet and coiled-coil linkers. Structure-activity relationship efforts led to generation of the fusion protein Syn-Vm24-CDR3L, which demonstrated excellent selectivity and potency against effector human memory T cells (subnanomolar to picomolar EC50 values). This fusion antibody also had significantly improved plasma half-life and serum stability in rodents compared with the parent Vm24 peptide. Finally, this fusion protein showed potent in vivo efficacy in the delayed type hypersensitivity in rats. These results illustrate the utility of antibody CDR fusions as a general and effective strategy to generate long-acting functional antibodies, and may lead to a selective immunosuppressive antibody for the treatment of autoimmune diseases.
Assuntos
Anticorpos Bloqueadores/farmacologia , Desenho de Fármacos , Imunossupressores/farmacologia , Canal de Potássio Kv1.3/antagonistas & inibidores , Sequência de Aminoácidos , Animais , Células CHO , Bovinos , Regiões Determinantes de Complementaridade/química , Cricetinae , Cricetulus , Células HEK293 , Humanos , Ativação Linfocitária/efeitos dos fármacos , Ratos , Proteínas Recombinantes de Fusão/química , Proteínas Recombinantes de Fusão/farmacologiaRESUMO
Effector memory T (Tem) cells are essential mediators of autoimmune disease and delayed-type hypersensitivity (DTH), a convenient model for two-photon imaging of Tem cell participation in an inflammatory response. Shortly (3 hr) after entry into antigen-primed ear tissue, Tem cells stably attached to antigen-bearing antigen-presenting cells (APCs). After 24 hr, enlarged Tem cells were highly motile along collagen fibers and continued to migrate rapidly for 18 hr. Tem cells rely on voltage-gated Kv1.3 potassium channels to regulate calcium signaling. ShK-186, a specific Kv1.3 blocker, inhibited DTH and suppressed Tem cell enlargement and motility in inflamed tissue but had no effect on homing to or motility in lymph nodes of naive and central memory T (Tcm) cells. ShK-186 effectively treated disease in a rat model of multiple sclerosis. These results demonstrate a requirement for Kv1.3 channels in Tem cells during an inflammatory immune response in peripheral tissues. Targeting Kv1.3 allows for effector memory responses to be suppressed while central memory responses remain intact.
Assuntos
Células Apresentadoras de Antígenos/imunologia , Hipersensibilidade Tardia/imunologia , Memória Imunológica , Canal de Potássio Kv1.3/antagonistas & inibidores , Bloqueadores dos Canais de Potássio/farmacologia , Linfócitos T/imunologia , Animais , Células Apresentadoras de Antígenos/metabolismo , Movimento Celular/efeitos dos fármacos , Infecções por Chlamydia/tratamento farmacológico , Infecções por Chlamydia/imunologia , Chlamydia trachomatis/imunologia , Colágeno , Encefalomielite Autoimune Experimental/tratamento farmacológico , Encefalomielite Autoimune Experimental/imunologia , Feminino , Hipersensibilidade Tardia/metabolismo , Memória Imunológica/efeitos dos fármacos , Canal de Potássio Kv1.3/metabolismo , Linfonodos/citologia , Linfonodos/imunologia , Ativação Linfocitária/efeitos dos fármacos , Orthomyxoviridae/imunologia , Infecções por Orthomyxoviridae/tratamento farmacológico , Infecções por Orthomyxoviridae/imunologia , Ovalbumina/imunologia , Bloqueadores dos Canais de Potássio/administração & dosagem , Bloqueadores dos Canais de Potássio/uso terapêutico , Proteínas/farmacologia , Ratos , Ratos Endogâmicos Lew , Receptores CCR7/imunologia , Linfócitos T/efeitos dos fármacos , Linfócitos T/metabolismoRESUMO
Chimeric antigen receptor (CAR)-engineered T cells (CAR-Ts) provide a potent antitumor response and have become a promising treatment option for cancer. However, despite their efficacy, CAR-T cells are associated with significant safety challenges related to the inability to control their activation and expansion and terminate their response. Herein, we demonstrate that a bifunctional small molecule "switch" consisting of folate conjugated to fluorescein isothiocyanate (folate-FITC) can redirect and regulate FITC-specific CAR-T cell activity toward folate receptor (FR)-overexpressing tumor cells. This system was shown to be highly cytotoxic to FR-positive cells with no activity against FR-negative cells, demonstrating the specificity of redirection by folate-FITC. Anti-FITC-CAR-T cell activation and proliferation was strictly dependent on the presence of both folate-FITC and FR-positive cells and was dose titratable with folate-FITC switch. This novel treatment paradigm may ultimately lead to increased safety for CAR-T cell immunotherapy.
Assuntos
Engenharia Celular , Ácido Fólico/química , Ácido Fólico/metabolismo , Receptores de Antígenos de Linfócitos T/genética , Linfócitos T/citologia , Fluoresceína-5-Isotiocianato/química , Transportadores de Ácido Fólico/metabolismo , Células HEK293 , Humanos , Células KB , Linfócitos T/metabolismoRESUMO
Liver X receptor (LXR) agonists have been explored as potential treatments for atherosclerosis and other diseases based on their ability to induce reverse cholesterol transport and suppress inflammation. However, this therapeutic potential has been hindered by on-target adverse effects in the liver mediated by excessive lipogenesis. Herein, we report a novel site-specific antibody-drug conjugate (ADC) that selectively delivers a LXR agonist to monocytes/macrophages while sparing hepatocytes. The unnatural amino acid para-acetylphenylalanine (pAcF) was site-specifically incorporated into anti-CD11a IgG, which binds the α-chain component of the lymphocyte function-associated antigen 1 (LFA-1) expressed on nearly all monocytes and macrophages. An aminooxy-modified LXR agonist was conjugated to anti-CD11a IgG through a stable, cathepsin B cleavable oxime linkage to afford a chemically defined ADC. The anti-CD11a IgG-LXR agonist ADC induced LXR activation specifically in human THP-1 monocyte/macrophage cells in vitro (EC50-27 nM), but had no significant effect in hepatocytes, indicating that payload delivery is CD11a-mediated. Moreover, the ADC exhibited higher-fold activation compared to a conventional synthetic LXR agonist T0901317 (Tularik) (3-fold). This novel ADC represents a fundamentally different strategy that uses tissue targeting to overcome the limitations of LXR agonists for potential use in treating atherosclerosis.
Assuntos
Benzoatos/administração & dosagem , Benzilaminas/administração & dosagem , Antígeno CD11a/imunologia , Sistemas de Liberação de Medicamentos , Hidrocarbonetos Fluorados/administração & dosagem , Imunoconjugados/administração & dosagem , Receptores Nucleares Órfãos/agonistas , Sulfonamidas/administração & dosagem , Benzoatos/imunologia , Benzoatos/farmacocinética , Benzilaminas/imunologia , Benzilaminas/farmacocinética , Linhagem Celular , Células Hep G2 , Hepatócitos/efeitos dos fármacos , Hepatócitos/imunologia , Humanos , Hidrocarbonetos Fluorados/imunologia , Hidrocarbonetos Fluorados/farmacocinética , Imunoconjugados/imunologia , Imunoconjugados/farmacocinética , Imunoglobulina G/imunologia , Receptores X do Fígado , Macrófagos/efeitos dos fármacos , Macrófagos/imunologia , Monócitos/efeitos dos fármacos , Monócitos/imunologia , Sulfonamidas/imunologia , Sulfonamidas/farmacocinéticaRESUMO
In efforts towards eliminating malaria, a discovery program was initiated to identify a novel antimalarial using KAF156 as a starting point. Following the most recent TCP/TPP guidelines, we have identified mCMQ069 with a predicted single oral dose for treatment (â¼40-106 mg) and one-month chemoprevention (â¼96-216 mg). We have improved unbound MPC and predicted human clearance by 18-fold and 10-fold respectively when compared to KAF156.
RESUMO
Recent malaria drug discovery approaches have been extensively focused on the development of oral, smallmolecule inhibitors for disease treatment whereas parenteral routes of administration have been avoided due to limitations in deploying a shelf-stable injectable even though it could be dosed less frequently. However, an updated target candidate profile from Medicines for Malaria Venture (MMV) and stakeholders have advocated for long-acting injectable chemopreventive agents as an important interventive tool to improve malaria prevention. Here, we present strategies for the development of a long-acting, intramuscular, injectable atovaquone prophylactic therapy. We have generated three prodrug approaches that are contrasted by their differential physiochemical properties and pharmacokinetic profiles: mCBK068, a docosahexaenoic acid ester of atovaquone formulated in sesame oil, mCKX352, a heptanoic acid ester of atovaquone formulated as a solution in sesame oil, and mCBE161, an acetic acid ester of atovaquone formulated as an aqueous suspension. As a result, from a single 20 mg/kg intramuscular injection, mCKX352 and mCBE161 maintain blood plasma exposure of atovaquone above the minimal efficacious concentration for >70 days and >30 days, respectively, in cynomolgus monkeys. The differences in plasma exposure are reflective of the prodrug strategy, which imparts altered chemical properties that ultimately influence aqueous solubility and depot release kinetics. On the strength of the pharmacokinetic and safety profiles, mCBE161 is being advanced as a first-in-class clinical candidate for first-in-human trials.
RESUMO
There remains a need to develop novel SARS-CoV-2 therapeutic options that improve upon existing therapies by an increased robustness of response, fewer safety liabilities, and global-ready accessibility. Functionally critical viral main protease (Mpro, 3CLpro) of SARS-CoV-2 is an attractive target due to its homology within the coronaviral family, and lack thereof toward human proteases. In this disclosure, we outline the advent of a novel SARS-CoV-2 3CLpro inhibitor, CMX990, bearing an unprecedented trifluoromethoxymethyl ketone warhead. Compared with the marketed drug nirmatrelvir (combination with ritonavir = Paxlovid), CMX990 has distinctly differentiated potency (â¼5× more potent in primary cells) and human in vitro clearance (>4× better microsomal clearance and >10× better hepatocyte clearance), with good in vitro-to-in vivo correlation. Based on its compelling preclinical profile and projected once or twice a day dosing supporting unboosted oral therapy in humans, CMX990 advanced to a Phase 1 clinical trial as an oral drug candidate for SARS-CoV-2.
Assuntos
COVID-19 , Humanos , SARS-CoV-2 , Diferenciação Celular , Revelação , Inibidores de Proteases/farmacologia , Inibidores de Proteases/uso terapêutico , Antivirais/farmacologiaRESUMO
(1) Background: Surgical phases form the basic building blocks for surgical skill assessment, feedback, and teaching. The phase duration itself and its correlation with clinical parameters at diagnosis have not yet been investigated. Novel commercial platforms provide phase indications but have not been assessed for accuracy yet. (2) Methods: We assessed 100 robot-assisted partial nephrectomy videos for phase durations based on previously defined proficiency metrics. We developed an annotation framework and subsequently compared our annotations to an existing commercial solution (Touch Surgery, Medtronic™). We subsequently explored clinical correlations between phase durations and parameters derived from diagnosis and treatment. (3) Results: An objective and uniform phase assessment requires precise definitions derived from an iterative revision process. A comparison to a commercial solution shows large differences in definitions across phases. BMI and the duration of renal tumor identification are positively correlated, as are tumor complexity and both tumor excision and renorrhaphy duration. (4) Conclusions: The surgical phase duration can be correlated with certain clinical outcomes. Further research should investigate whether the retrieved correlations are also clinically meaningful. This requires an increase in dataset sizes and facilitation through intelligent computer vision algorithms. Commercial platforms can facilitate this dataset expansion and help unlock the full potential, provided that the phase annotation details are disclosed.
RESUMO
The Kv1.3 channel is a recognized target for pharmaceutical development to treat autoimmune diseases and organ rejection. ShK-186, a specific peptide inhibitor of Kv1.3, has shown promise in animal models of multiple sclerosis and rheumatoid arthritis. Here, we describe the pharmacokinetic-pharmacodynamic relationship for ShK-186 in rats and monkeys. The pharmacokinetic profile of ShK-186 was evaluated with a validated high-performance liquid chromatography-tandem mass spectrometry method to measure the peptide's concentration in plasma. These results were compared with single-photon emission computed tomography/computed tomography data collected with an ¹¹¹In-1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid-conjugate of ShK-186 to assess whole-blood pharmacokinetic parameters as well as the peptide's absorption, distribution, and excretion. Analysis of these data support a model wherein ShK-186 is absorbed slowly from the injection site, resulting in blood concentrations above the Kv1.3 channel-blocking IC50 value for up to 7 days in monkeys. Pharmacodynamic studies on human peripheral blood mononuclear cells showed that brief exposure to ShK-186 resulted in sustained suppression of cytokine responses and may contribute to prolonged drug effects. In delayed-type hypersensitivity, chronic relapsing-remitting experimental autoimmune encephalomyelitis, and pristane-induced arthritis rat models, a single dose of ShK-186 every 2 to 5 days was as effective as daily administration. ShK-186's slow distribution from the injection site and its long residence time on the Kv1.3 channel contribute to the prolonged therapeutic effect of ShK-186 in animal models of autoimmune disease.
Assuntos
Doenças Autoimunes/tratamento farmacológico , Canal de Potássio Kv1.3/antagonistas & inibidores , Proteínas/farmacologia , Linfócitos T/efeitos dos fármacos , Absorção/efeitos dos fármacos , Absorção/imunologia , Animais , Artrite/tratamento farmacológico , Artrite/imunologia , Artrite/metabolismo , Doenças Autoimunes/imunologia , Doenças Autoimunes/metabolismo , Citocinas/imunologia , Citocinas/metabolismo , Modelos Animais de Doenças , Relação Dose-Resposta a Droga , Encefalomielite Autoimune Experimental/tratamento farmacológico , Encefalomielite Autoimune Experimental/imunologia , Encefalomielite Autoimune Experimental/metabolismo , Feminino , Humanos , Concentração Inibidora 50 , Canal de Potássio Kv1.3/imunologia , Canal de Potássio Kv1.3/metabolismo , Leucócitos Mononucleares/efeitos dos fármacos , Leucócitos Mononucleares/imunologia , Leucócitos Mononucleares/metabolismo , Macaca fascicularis , Bloqueadores dos Canais de Potássio/imunologia , Bloqueadores dos Canais de Potássio/farmacocinética , Bloqueadores dos Canais de Potássio/farmacologia , Proteínas/farmacocinética , Ratos , Ratos Sprague-Dawley , Saimiri , Linfócitos T/imunologia , Linfócitos T/metabolismo , Distribuição Tecidual/efeitos dos fármacos , Distribuição Tecidual/imunologiaRESUMO
Prevention of infection and propagation of SARS-CoV-2 is of high priority in the COVID-19 pandemic. Here, we describe S-nitrosylation of multiple proteins involved in SARS-CoV-2 infection, including angiotensin converting enzyme 2 (ACE2), the receptor for viral entry. This reaction prevents binding of ACE2 to the SARS-CoV-2 Spike protein, thereby inhibiting viral entry, infectivity, and cytotoxicity. Aminoadamantane compounds also inhibit coronavirus ion channels formed by envelope (E) protein. Accordingly, we developed dual-mechanism aminoadamantane nitrate compounds that inhibit viral entry and thus spread of infection by S-nitrosylating ACE2 via targeted delivery of the drug after E-protein channel blockade. These non-toxic compounds are active in vitro and in vivo in the Syrian hamster COVID-19 model, and thus provide a novel avenue for therapy.
RESUMO
Peptide toxins found in a wide array of venoms block K(+) channels, causing profound physiological and pathological effects. Here we describe the first functional K(+) channel-blocking toxin domain in a mammalian protein. MMP23 (matrix metalloprotease 23) contains a domain (MMP23(TxD)) that is evolutionarily related to peptide toxins from sea anemones. MMP23(TxD) shows close structural similarity to the sea anemone toxins BgK and ShK. Moreover, this domain blocks K(+) channels in the nanomolar to low micromolar range (Kv1.6 > Kv1.3 > Kv1.1 = Kv3.2 > Kv1.4, in decreasing order of potency) while sparing other K(+) channels (Kv1.2, Kv1.5, Kv1.7, and KCa3.1). Full-length MMP23 suppresses K(+) channels by co-localizing with and trapping MMP23(TxD)-sensitive channels in the ER. Our results provide clues to the structure and function of the vast family of proteins that contain domains related to sea anemone toxins. Evolutionary pressure to maintain a channel-modulatory function may contribute to the conservation of this domain throughout the plant and animal kingdoms.
Assuntos
Metaloendopeptidases/química , Canais de Potássio/química , Sequência de Aminoácidos , Animais , Células COS , Chlorocebus aethiops , Venenos de Cnidários/química , Evolução Molecular , Humanos , Dados de Sequência Molecular , Peptídeos/química , Filogenia , Estrutura Terciária de Proteína , Anêmonas-do-Mar/metabolismo , Homologia de Sequência de Aminoácidos , TransfecçãoRESUMO
The ongoing pandemic caused by the novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), necessitates strategies to identify prophylactic and therapeutic drug candidates for rapid clinical deployment. Here, we describe a screening pipeline for the discovery of efficacious SARS-CoV-2 inhibitors. We screen a best-in-class drug repurposing library, ReFRAME, against two high-throughput, high-content imaging infection assays: one using HeLa cells expressing SARS-CoV-2 receptor ACE2 and the other using lung epithelial Calu-3 cells. From nearly 12,000 compounds, we identify 49 (in HeLa-ACE2) and 41 (in Calu-3) compounds capable of selectively inhibiting SARS-CoV-2 replication. Notably, most screen hits are cell-line specific, likely due to different virus entry mechanisms or host cell-specific sensitivities to modulators. Among these promising hits, the antivirals nelfinavir and the parent of prodrug MK-4482 possess desirable in vitro activity, pharmacokinetic and human safety profiles, and both reduce SARS-CoV-2 replication in an orthogonal human differentiated primary cell model. Furthermore, MK-4482 effectively blocks SARS-CoV-2 infection in a hamster model. Overall, we identify direct-acting antivirals as the most promising compounds for drug repurposing, additional compounds that may have value in combination therapies, and tool compounds for identification of viral host cell targets.
Assuntos
Antivirais/farmacologia , Tratamento Farmacológico da COVID-19 , Reposicionamento de Medicamentos/métodos , Pandemias , SARS-CoV-2 , Animais , COVID-19/prevenção & controle , COVID-19/virologia , Linhagem Celular , Citidina/administração & dosagem , Citidina/análogos & derivados , Citidina/farmacologia , Bases de Dados de Produtos Farmacêuticos , Descoberta de Drogas/métodos , Avaliação Pré-Clínica de Medicamentos/métodos , Células HeLa , Ensaios de Triagem em Larga Escala/métodos , Humanos , Hidroxilaminas/administração & dosagem , Hidroxilaminas/farmacologia , Mesocricetus , Nelfinavir/farmacologia , SARS-CoV-2/efeitos dos fármacos , SARS-CoV-2/fisiologia , Replicação Viral/efeitos dos fármacosRESUMO
The quinazolines CBR417 and CBR490 were previously shown to be potent anti-wolbachials that deplete Wolbachia endosymbionts of filarial nematodes and present promising pre-clinical candidates for human filarial diseases such as onchocerciasis. In the present study we tested both candidates in two models of chronic filarial infection, namely the Litomosoides sigmodontis and Brugia pahangi jird model and assessed their long-term effect on Wolbachia depletion, microfilariae counts and filarial embryogenesis 16-18 weeks after treatment initiation (wpt). Once per day (QD) oral treatment with CBR417 (50 mg/kg) for 4 days or twice per day (BID) with CBR490 (25 mg/kg) for 7 days during patent L. sigmodontis infection reduced the Wolbachia load by >99% and completely cleared peripheral microfilaremia from 10-14 wpt. Similarly, 7 days of QD treatments (40 mg/kg) with CBR417 or CBR490 cleared >99% of Wolbachia from B. pahangi and reduced peritoneal microfilariae counts by 93% in the case of CBR417 treatment. Transmission electron microscopy analysis indicated intensive damage to the B. pahangi ovaries following CBR417 treatment and in accordance filarial embryogenesis was inhibited in both models after CBR417 or CBR490 treatment. Suboptimal treatment regimens of CBR417 or CBR490 did not lead to a maintained reduction of the microfilariae and Wolbachia load. In conclusion, CBR417 or CBR490 are pre-clinical candidates for filarial diseases, which achieve long-term clearance of Wolbachia endosymbionts of filarial nematodes, inhibit filarial embryogenesis and clear microfilaremia with treatments as short as 7 days.
Assuntos
Antibacterianos/uso terapêutico , Filariose/tratamento farmacológico , Oncocercose/tratamento farmacológico , Quinazolinas/uso terapêutico , Wolbachia/efeitos dos fármacos , Animais , Antibacterianos/administração & dosagem , Brugia pahangi/efeitos dos fármacos , Feminino , Filariose/microbiologia , Filarioidea/efeitos dos fármacos , Gerbillinae/microbiologia , Gerbillinae/parasitologia , Microfilárias/efeitos dos fármacos , Quinazolinas/administração & dosagem , Simbiose/efeitos dos fármacosRESUMO
OBJECTIVE: The goal of this study was to develop and validate a cytochrome P450 (CYP) 2D6 probe substrate with improved sensitivity to elucidate the relationship of CYP2D6 ribonucleic acid transcript levels, genotype, and enzyme activity in human liver biopsy samples. METHODS: CYP2D6 activity in tissue homogenates of liver biopsy specimens collected from control subjects (with no apparent liver disease), liver biopsy subjects, liver transplant subjects, and liver bank specimens was assessed with a calcimimetic, R-568, a high-clearance and specific substrate of CYP2D6. The livers were genotyped for the 6 most common CYP2D6 genetic variants (ie, *3, *4, *5, *6, *7, and *8). The 1.5-kilobase CYP2D6 messenger ribonucleic acid (referred to as full-length) transcripts were estimated with a semiquantitative reverse transcription-polymerase chain reaction assay. RESULTS: As a CYP2D6-specific catalytic probe, R-568 offers a 20-fold higher sensitivity compared with that of dextromethorphan. The improved assay sensitivity allowed evaluation of CYP2D6 enzyme activity in a few milligrams of tissue collected from biopsy specimens. The ratio of CYP2D6 enzyme activity to transcript remained relatively constant within each group of subjects, especially within the control group. However, mean activity to transcript varied greatly across the 4 groups of subjects. The liver samples in the control group showed significantly higher enzyme activity but a lower transcript level. CONCLUSIONS: A combination of genotyping and messenger ribonucleic acid level determination could allow a quantitative estimation of functional CYP2D6 activity in healthy human livers with a reasonable degree of confidence. Kinetic study with R-568 indicates that this compound is probably the most sensitive CYP2D6 probe substrate available.
Assuntos
Citocromo P-450 CYP2D6/genética , Genótipo , Fígado/química , Fígado/enzimologia , RNA Mensageiro/análise , Biópsia , Estudos de Casos e Controles , Técnicas de Cultura , Ativação Enzimática , Humanos , Fígado/patologia , Valor Preditivo dos Testes , Reação em Cadeia da Polimerase Via Transcriptase Reversa/métodos , Sensibilidade e Especificidade , Especificidade por SubstratoRESUMO
Electrophysiological and pharmacological studies coupled with molecular identification have revealed a unique network of ion channels--Kv1.3, KCa3.1, CRAC (Orai1 + Stim1), TRPM7, Cl(swell)--in lymphocytes that initiates and maintains the calcium signaling cascade required for activation. The expression pattern of these channels changes during lymphocyte activation and differentiation, allowing the functional network to adapt during an immune response. The Kv1.3 channel is of interest because it plays a critical role in subsets of T and B lymphocytes implicated in autoimmune disorders. The ShK toxin from the sea anemone Stichodactyla helianthus is a potent blocker of Kv1.3. ShK-186, a synthetic analog of ShK, is being developed as a therapeutic for autoimmune diseases, and is scheduled to begin first-in-man phase-1 trials in 2011. This review describes the journey that has led to the development of ShK-186.
Assuntos
Doenças Autoimunes/tratamento farmacológico , Venenos de Cnidários/farmacologia , Fatores Imunológicos/farmacologia , Anêmonas-do-Mar , Sequência de Aminoácidos , Animais , Diferenciação Celular/efeitos dos fármacos , Venenos de Cnidários/farmacocinética , Efeitos Colaterais e Reações Adversas Relacionados a Medicamentos , Fatores Imunológicos/farmacocinética , Canais Iônicos/metabolismo , Ativação Linfocitária/efeitos dos fármacos , Dados de Sequência Molecular , Conformação ProteicaRESUMO
We discuss the potential use of inhibitors of Kv1.3 potassium channels in T lymphocytes as therapeutics for multiple sclerosis. Current treatment strategies target the immune system in a non-selective manner. The resulting general immunosuppression, toxic side-effects and increased risk of opportunistic infections create the need for more selective therapeutics. Autoreactive effector-memory T (T(EM)) cells, considered to be major mediators of autoimmunity, express large numbers of Kv1.3 channels. Selective blockers of Kv1.3 inhibit calcium signaling, cytokine production and proliferation of T(EM) cells in vitro, and T(EM) cell-motility in vivo. Kv1.3 blockers ameliorate disease in animal models of multiple sclerosis, rheumatoid arthritis, type 1 diabetes mellitus and contact dermatitis without compromising the protective immune response to acute infections. Kv1.3 blockers have a good safety profile in rodents and primates.
Assuntos
Sistemas de Liberação de Medicamentos/métodos , Canal de Potássio Kv1.3/antagonistas & inibidores , Canal de Potássio Kv1.3/metabolismo , Esclerose Múltipla/tratamento farmacológico , Esclerose Múltipla/metabolismo , Bloqueadores dos Canais de Potássio/administração & dosagem , Animais , Proliferação de Células/efeitos dos fármacos , Citocinas/antagonistas & inibidores , Citocinas/biossíntese , Sistemas de Liberação de Medicamentos/tendências , Humanos , Esclerose Múltipla/patologia , Linfócitos T/efeitos dos fármacos , Linfócitos T/metabolismo , Linfócitos T/patologiaRESUMO
The polypeptide toxin ShK is a potent blocker of Kv1.3 potassium channels, which are crucial in the activation of human effector memory T cells (T(EM)); selective blockers constitute valuable therapeutic leads for the treatment of autoimmune diseases mediated by T(EM) cells, such as multiple sclerosis, rheumatoid arthritis, and type-1 diabetes. The critical motif on the toxin for potassium channel blockade consists of neighboring lysine and tyrosine residues. Because this motif is sufficient for activity, an ShK analogue was designed based on D-amino acids. D-allo-ShK has a structure essentially identical with that of ShK and is resistant to proteolysis. It blocked Kv1.3 with K(d) 36 nm (2,800-fold lower affinity than ShK), was 2-fold selective for Kv1.3 over Kv1.1, and was inactive against other K(+) channels tested. D-allo-ShK inhibited human T(EM) cell proliferation at 100-fold higher concentration than ShK. Its circulating half-life was only slightly longer than that of ShK, implying that renal clearance is the major determinant of its plasma levels. D-allo-ShK did not bind to the closed state of the channel, unlike ShK. Models of D-allo-ShK bound to Kv1.3 show that it can block the pore as effectively as ShK but makes different interactions with the vestibule, some of which are less favorable than for native ShK. The finding that an all-D analogue of a polypeptide toxin retains biological activity and selectivity is highly unusual. Being resistant to proteolysis and nonantigenic, this analogue should be useful in K(+) channel studies; all-d analogues with improved Kv1.3 potency and specificity may have therapeutic advantages.