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1.
Pharm Res ; 40(11): 2567-2584, 2023 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-37523014

RESUMO

PURPOSE: The differences between intestinal and systemic (hepatic and renal) P-glycoprotein (P-gp) and breast cancer resistance protein (BCRP) roles in drug disposition are difficult to define. Accordingly, we characterized Encequidar (ECD) as an intestinal P-gp and BCRP specific inhibitor to evaluate their role in drug disposition. METHODS: We assessed the in vitro and in vivo inhibition potential of ECD towards human and animal P-gp and BCRP. RESULTS: ECD is a potent inhibitor with a high degree of selectivity in inhibiting human P-gp (hP-gp) over human BCRP (hBCRP) (IC50s of 0.0058 ± 0.0006 vs. > 10 µM, respectively). In contrast, ECD is a potent inhibitor of rat and cynomolgus monkey BCRP (IC50 ranged from 0.059 to 0.18 µM). While the AUC of IV paclitaxel (PTX) was significantly increased by elacridar (ELD) (P < 0.05) but not ECD in rats (15 mg/kg; PO) (2.55- vs. 0.93-fold), that of PO PTX was significantly elevated to a similar extent between the inhibitors (39.5- vs. 33.5-fold). Similarly, the AUC of PO sulfasalazine (SFZ) was dramatically increased by ELD and ECD (16.6- vs. 3.04-fold) although that of IV SFZ was not significantly affected by ELD and ECD in rats (1.18- vs. 1.06-fold). Finally, a comparable ECD-induced increase of the AUC of PO talinolol in cynomolgus monkeys was observed compared with ELD (2.14- vs. 2.12-fold). CONCLUSIONS: ECD may allow an in-depth appraisal of the role of intestinal efflux transporter(s) in drug disposition in animals and humans through local intestinal drug interactions.


Assuntos
Transportadores de Cassetes de Ligação de ATP , Proteínas de Neoplasias , Humanos , Ratos , Animais , Transportadores de Cassetes de Ligação de ATP/metabolismo , Membro 2 da Subfamília G de Transportadores de Cassetes de Ligação de ATP/metabolismo , Macaca fascicularis/metabolismo , Proteínas de Neoplasias/metabolismo , Paclitaxel , Interações Medicamentosas
2.
J Med Chem ; 64(3): 1454-1480, 2021 02 11.
Artigo em Inglês | MEDLINE | ID: mdl-33492963

RESUMO

Sphingosine-1-phosphate (S1P) binds to a family of sphingosine-1-phosphate G-protein-coupled receptors (S1P1-5). The interaction of S1P with these S1P receptors has a fundamental role in many physiological processes in the vascular and immune systems. Agonist-induced functional antagonism of S1P1 has been shown to result in lymphopenia. As a result, agonists of this type hold promise as therapeutics for autoimmune disorders. The previously disclosed differentiated S1P1 modulator BMS-986104 (1) exhibited improved preclinical cardiovascular and pulmonary safety profiles as compared to earlier full agonists of S1P1; however, it demonstrated a long pharmacokinetic half-life (T1/2 18 days) in the clinic and limited formation of the desired active phosphate metabolite. Optimization of this series through incorporation of olefins, ethers, thioethers, and glycols into the alkyl side chain afforded an opportunity to reduce the projected human T1/2 and improve the formation of the active phosphate metabolite while maintaining efficacy as well as the improved safety profile. These efforts led to the discovery of 12 and 24, each of which are highly potent, biased agonists of S1P1. These compounds not only exhibited shorter in vivo T1/2 in multiple species but are also projected to have significantly shorter T1/2 values in humans when compared to our first clinical candidate. In models of arthritis, treatment with 12 and 24 demonstrated robust efficacy.


Assuntos
Compostos Bicíclicos com Pontes/síntese química , Compostos Bicíclicos com Pontes/farmacologia , Pró-Proteína Convertases/efeitos dos fármacos , Serina Endopeptidases/efeitos dos fármacos , Animais , Artrite Experimental/tratamento farmacológico , Doenças Autoimunes/tratamento farmacológico , Biotransformação , Compostos Bicíclicos com Pontes/efeitos adversos , Líquido da Lavagem Broncoalveolar , Quimiotaxia de Leucócito/efeitos dos fármacos , Avaliação Pré-Clínica de Medicamentos , Meia-Vida , Humanos , Pneumopatias/induzido quimicamente , Pneumopatias/patologia , Masculino , Miócitos Cardíacos/efeitos dos fármacos , Fosforilação , Ratos , Ratos Endogâmicos Lew , Relação Estrutura-Atividade
3.
ACS Med Chem Lett ; 11(9): 1766-1772, 2020 Sep 10.
Artigo em Inglês | MEDLINE | ID: mdl-32944145

RESUMO

Efforts aimed at increasing the in vivo potency and reducing the elimination half-life of 1 and 2 led to the identification of aryl ether and thioether-derived bicyclic S1P1 differentiated modulators 3-6. The effects of analogs 3-6 on lymphocyte reduction in the rat (desired pharmacology) along with pulmonary- and cardiovascular-related effects (undesired pharmacology) are described. Optimization of the overall properties in the aryl ether series yielded 3d, and the predicted margin of safety against the cardiovascular effects of 3d would be large enough for human studies. Importantly, compared to 1 and 2, compound 3d had a better profile in both potency (ED50 < 0.05 mg/kg) and predicted human half-life (t 1/2 ∼ 5 days).

5.
Front Pharmacol ; 10: 749, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31379564

RESUMO

Antibody-drug conjugates (ADCs) are composed of an antibody linked to cytotoxic anticancer payloads. ADCs recognize tumor-specific cell surface antigens and are internalized into lysosomes where proteolytic enzymes release the cytotoxic payloads. Efflux transporters on plasma membrane that play a significant role on multi-drug resistance in chemotherapy can be internalized on lysosomal membrane and sequester the cytotoxic payloads. In the present study, ATP binding cassette (ABC) efflux transporters including breast cancer resistance protein (BCRP), P-glycoprotein (P-gp-MDR1), multidrug resistance protein (MRP) 2, MRP3 and MRP4 in lysosomal, and plasma membrane of tumor cells were quantified by targeted quantitative proteomics. The cytotoxicity of brentuximab vedotin and its cytotoxic payload monomethyl auristatin E (MMAE) to the tumor cell lines in the presence and absence of elacridar (P-gp-MDR1 inhibitor) or chloroquine (lysosomotropic agent) were evaluated. MMAE is a substrate for P-gp-MDR1, as the apparent efflux ratio in MDR1 transfected MDCK cell monolayers was 44.5, and elacridar abolished the MMAE efflux. Cell lines that highly express P-gp-MDR1 show higher EC50s toward the cell killing effects of MMAE. Co-incubation with chloroquine or elacridar resulted in left shift of MMAE EC50 by 2.9-16-fold and 4.2-22-fold, respectively. Similarly co-incubation with chloroquine or elacridar or in combination of chloroquine and elacridar increased cytotoxic effects of brentuximab vedotin by 2.8- to 21.4-fold on KM-H2 cells that express a specific tumor antigen CD30 and P-gp-MDR1. These findings demonstrate important roles of P-gp-MDR1 on cytotoxic effects of brentuximab vedotin and its payload MMAE. Collectively, ABC transporter-mediated drug extrusion and/or sequestration needs to be early assessed for selection of optimal payloads and linkers when developing ADCs.

6.
J Med Chem ; 62(5): 2265-2285, 2019 03 14.
Artigo em Inglês | MEDLINE | ID: mdl-30785748

RESUMO

Recently, our research group reported the identification of BMS-986104 (2) as a differentiated S1P1 receptor modulator. In comparison to fingolimod (1), a full agonist of S1P1 currently marketed for the treatment of relapse remitting multiple sclerosis (RRMS), 2 offers several potential advantages having demonstrated improved safety multiples in preclinical evaluations against undesired pulmonary and cardiovascular effects. In clinical trials, 2 was found to exhibit a pharmacokinetic half-life ( T1/2) longer than that of 1, as well as a reduced formation of the phosphate metabolite that is required for activity against S1P1. Herein, we describe our efforts to discover highly potent, partial agonists of S1P1 with a shorter T1/2 and increased in vivo phosphate metabolite formation. These efforts culminated in the discovery of BMS-986166 (14a), which was advanced to human clinical evaluation. The pharmacokinetic/pharmacodynamic (PK/PD) relationship as well as pulmonary and cardiovascular safety assessments are discussed. Furthermore, efficacy of 14a in multiple preclinical models of autoimmune diseases are presented.


Assuntos
Ensaios Clínicos como Assunto , Naftalenos/farmacologia , Receptores de Esfingosina-1-Fosfato/agonistas , Tetra-Hidronaftalenos/farmacologia , Animais , Líquido da Lavagem Broncoalveolar , Relação Dose-Resposta a Droga , Meia-Vida , Humanos , Naftalenos/química , Naftalenos/farmacocinética , Ratos , Ratos Endogâmicos Lew , Tetra-Hidronaftalenos/química , Tetra-Hidronaftalenos/farmacocinética
8.
AAPS J ; 19(6): 1878-1889, 2017 11.
Artigo em Inglês | MEDLINE | ID: mdl-29019117

RESUMO

In the present investigations, we evaluate in vitro hepatocyte uptake and partitioning for the prediction of in vivo clearance and liver partitioning. Monkeys were intravenously co-dosed with rosuvastatin and bosentan, substrates of the organic anion transporting polypeptides (OATPs), and metformin, a substrate of organic cation transporter 1 (OCT1). Serial plasma and liver samples were collected over time. Liver and plasma unbound fraction was determined using equilibrium dialysis. In vivo unbound partitioning (Kpu,u) for rosuvastatin, bosentan, and metformin, calculated from total concentrations in the liver and plasma, were 243, 553, and 15, respectively. A physiologically based pharmacokinetic monkey model that incorporates active and passive hepatic uptake was developed to fit plasma and liver concentrations. In addition, a two-compartment model was used to fit in vitro hepatic uptake curves in suspended monkey hepatocyte to determine active uptake, passive diffusion, and intracellular unbound fraction parameters. At steady-state in the model, in vitro Kpu,u was determined. The results demonstrated that in vitro values under-predicted in vivo active uptake for rosuvastatin, bosentan, and metformin by 6.7-, 28-, and 1.5-fold, respectively, while passive diffusion was over-predicted. In vivo Kpu,u values were under-predicted from in vitro data by 30-, 79-, and 3-fold. In conclusion, active uptake and liver partitioning in monkeys for OATP substrates were greatly under-predicted from in vitro hepatocyte uptake, while OCT-mediated uptake and partitioning scaled reasonably well from in vitro, demonstrating substrate- and transporter-dependent scaling factors. The combination of in vitro experimental and modeling approaches proved useful for assessing prediction of in vivo intracellular partitioning.


Assuntos
Fígado/metabolismo , Transportadores de Ânions Orgânicos/fisiologia , Transportador 1 de Cátions Orgânicos/fisiologia , Animais , Bosentana , Macaca fascicularis , Metformina/farmacocinética , Modelos Biológicos , Rosuvastatina Cálcica/farmacocinética , Sulfonamidas/farmacocinética
9.
Methods Mol Biol ; 1570: 315-338, 2017.
Artigo em Inglês | MEDLINE | ID: mdl-28238147

RESUMO

The patent landscape, like a garden, can tell you much about its designers and users; their motivations, biases, and general interests. While both patent landscapes and gardens may appear to the casual observer as refined and ordered, an in-depth exploration of the terrain is likely to reveal unforeseen challenges including, for example, alien species, thickets, and trolls. As this Chapter illustrates, patent landscapes are dynamic and have been forced to continually evolve in response to technological innovation. While emerging technologies, such as biotechnology and information communication technology have challenged the traditional patent landscape, resulting in the pruning of certain elements here and there, the overarching framework and design has largely remained intact. But will this always be the case? As the field of nanotechnology continues to evolve and mature, the aim of this Chapter is to map how the technology has evolved and grown within the confines of existing structures and underlying foundation of the patent landscape and the implications thereof for the technology, industry, and the public more generally. The Chapter concludes by asking the question whether the current patent landscape will be able to withstand the ubiquitous nature of the technology, or whether nanotechnology, in combination with other emerging technologies, will be a catalyst for governments and policy makers to completely redesign the patent landscape.


Assuntos
Propriedade Intelectual , Nanotecnologia , Patentes como Assunto , Humanos , Invenções/economia , Invenções/ética , Invenções/legislação & jurisprudência , Nanotecnologia/economia , Nanotecnologia/ética , Nanotecnologia/legislação & jurisprudência , Patentes como Assunto/ética , Patentes como Assunto/legislação & jurisprudência
10.
Medchemcomm ; 8(4): 725-729, 2017 Apr 01.
Artigo em Inglês | MEDLINE | ID: mdl-30108791

RESUMO

Recently, our research group reported the identification of prodrug amino-alcohol 2 as a potent and efficacious S1P1 receptor modulator. This molecule is differentiated preclinically over the marketed drug fingolimod (Gilenya 1), whose active phosphate metabolite is an S1P1 full agonist, in terms of pulmonary and cardiovascular safety. S1P1 partial agonist 2, however, has a long half-life in rodents and was projected to have a long half-life in humans. The purpose of this communication is to disclose highly potent partial agonists of S1P1 with shorter half-lives relative to the clinical compound 2. PK/PD relationships as well as their preclinical pulmonary and cardiovascular safety assessment are discussed.

11.
J Med Chem ; 59(24): 11138-11147, 2016 12 22.
Artigo em Inglês | MEDLINE | ID: mdl-28002964

RESUMO

We describe a highly efficient route for the synthesis of 4a (BMS-986104). A key step in the synthesis is the asymmetric hydroboration of trisubstituted alkene 6. Particularly given the known difficulties involved in this type of transformation (6 → 7), the current methodology provides an efficient approach to prepare this class of compounds. In addition, we disclose the efficacy of 4a in a mouse EAE model, which is comparable to 4c (FTY720). Mechanistically, 4a exhibited excellent remyelinating effects on lysophosphatidylcholine (LPC) induced demyelination in a three-dimensional brain cell culture assay.


Assuntos
Encefalomielite Autoimune Experimental/tratamento farmacológico , Naftalenos/farmacologia , Receptores de Lisoesfingolipídeo/agonistas , Animais , Células Cultivadas , Modelos Animais de Doenças , Relação Dose-Resposta a Droga , Feminino , Células HEK293 , Humanos , Linfócitos/efeitos dos fármacos , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Endogâmicos C57BL , Estrutura Molecular , Naftalenos/síntese química , Naftalenos/química , Relação Estrutura-Atividade
12.
J Med Chem ; 59(21): 9837-9854, 2016 11 10.
Artigo em Inglês | MEDLINE | ID: mdl-27726358

RESUMO

Fingolimod (1) is the first approved oral therapy for the treatment of relapsing remitting multiple sclerosis. While the phosphorylated metabolite of fingolimod was found to be a nonselective S1P receptor agonist, agonism specifically of S1P1 is responsible for the peripheral blood lymphopenia believed to be key to its efficacy. Identification of modulators that maintain activity on S1P1 while sparing activity on other S1P receptors could offer equivalent efficacy with reduced liabilities. We disclose in this paper a ligand-based drug design approach that led to the discovery of a series of potent tricyclic agonists of S1P1 with selectivity over S1P3 and were efficacious in a pharmacodynamic model of suppression of circulating lymphocytes. Compound 10 had the desired pharmacokinetic (PK) and pharmacodynamic (PD) profile and demonstrated maximal efficacy when administered orally in a rat adjuvant arthritis model.


Assuntos
Desenho de Fármacos , Cloridrato de Fingolimode/farmacologia , Compostos Heterocíclicos com 3 Anéis/farmacologia , Receptores de Lisoesfingolipídeo/agonistas , Animais , Artrite Experimental/tratamento farmacológico , Artrite Experimental/imunologia , Cães , Relação Dose-Resposta a Droga , Cloridrato de Fingolimode/administração & dosagem , Cloridrato de Fingolimode/química , Adjuvante de Freund/administração & dosagem , Compostos Heterocíclicos com 3 Anéis/administração & dosagem , Compostos Heterocíclicos com 3 Anéis/química , Ligantes , Linfócitos/efeitos dos fármacos , Macaca fascicularis , Masculino , Camundongos , Estrutura Molecular , Mycobacterium/efeitos dos fármacos , Ratos , Ratos Endogâmicos Lew , Relação Estrutura-Atividade , Distribuição Tecidual
13.
J Med Chem ; 59(13): 6248-64, 2016 07 14.
Artigo em Inglês | MEDLINE | ID: mdl-27309907

RESUMO

Sphingosine-1-phosphate (S1P) is a bioactive sphingolipid metabolite that regulates a multitude of physiological processes such as lymphocyte trafficking, cardiac function, vascular development, and inflammation. Because of the ability of S1P1 receptor agonists to suppress lymphocyte egress, they have great potential as therapeutic agents in a variety of autoimmune diseases. In this article, the discovery of selective, direct acting S1P1 agonists utilizing an ethanolamine scaffold containing a terminal carboxylic acid is described. Potent S1P1 agonists such as compounds 18a and 19a which have greater than 1000-fold selectivity over S1P3 are described. These compounds efficiently reduce blood lymphocyte counts in rats through 24 h after single doses of 1 and 0.3 mpk, respectively. Pharmacodynamic properties of both compounds are discussed. Compound 19a was further studied in two preclinical models of disease, exhibiting good efficacy in both the rat adjuvant arthritis model (AA) and the mouse experimental autoimmune encephalomyelitis model (EAE).


Assuntos
Etanolamina/química , Etanolamina/farmacologia , Linfócitos/efeitos dos fármacos , Receptores de Lisoesfingolipídeo/agonistas , Animais , Artrite/tratamento farmacológico , Cães , Encefalomielite Autoimune Experimental/tratamento farmacológico , Etanolamina/farmacocinética , Etanolamina/uso terapêutico , Feminino , Haplorrinos , Humanos , Contagem de Linfócitos , Linfócitos/citologia , Masculino , Camundongos , Camundongos Endogâmicos C57BL , Ratos , Ratos Endogâmicos Lew , Receptores de Lisoesfingolipídeo/metabolismo , Relação Estrutura-Atividade
14.
Bioorg Med Chem Lett ; 26(10): 2470-2474, 2016 05 15.
Artigo em Inglês | MEDLINE | ID: mdl-27055941

RESUMO

The synthesis and structure-activity relationship (SAR) of a series of pyridyl-isoxazole based agonists of S1P1 are discussed. Compound 5b provided potent in vitro activity with selectivity, had an acceptable pharmacokinetic profile, and demonstrated efficacy in a dose dependent manner when administered orally in a rodent model of arthritis.


Assuntos
Artrite Experimental/tratamento farmacológico , Lisofosfolipídeos/agonistas , Esfingosina/análogos & derivados , Relação Estrutura-Atividade , Administração Oral , Animais , Técnicas de Química Sintética , Relação Dose-Resposta a Droga , Avaliação Pré-Clínica de Medicamentos/métodos , Humanos , Isoxazóis/química , Isoxazóis/farmacologia , Contagem de Linfócitos , Masculino , Ratos Endogâmicos Lew , Receptores de Lisoesfingolipídeo/agonistas , Esfingosina/agonistas
15.
ACS Med Chem Lett ; 7(3): 283-8, 2016 Mar 10.
Artigo em Inglês | MEDLINE | ID: mdl-26985316

RESUMO

Clinical validation of S1P receptor modulation therapy was achieved with the approval of fingolimod (Gilenya, 1) as the first oral therapy for relapsing remitting multiple sclerosis. However, 1 causes a dose-dependent reduction in the heart rate (bradycardia), which occurs within hours after first dose. We disclose the identification of clinical compound BMS-986104 (3d), a novel S1P1 receptor modulator, which demonstrates ligand-biased signaling and differentiates from 1 in terms of cardiovascular and pulmonary safety based on preclinical pharmacology while showing equivalent efficacy in a T-cell transfer colitis model.

16.
J Med Chem ; 59(6): 2820-40, 2016 Mar 24.
Artigo em Inglês | MEDLINE | ID: mdl-26924461

RESUMO

Sphingosine 1-phosphate (S1P) is the endogenous ligand for the sphingosine 1-phosphate receptors (S1P1-5) and evokes a variety of cellular responses through their stimulation. The interaction of S1P with the S1P receptors plays a fundamental physiological role in a number of processes including vascular development and stabilization, lymphocyte migration, and proliferation. Agonism of S1P1, in particular, has been shown to play a significant role in lymphocyte trafficking from the thymus and secondary lymphoid organs, resulting in immunosuppression. This article will detail the discovery and SAR of a potent and selective series of isoxazole based full agonists of S1P1. Isoxazole 6d demonstrated impressive efficacy when administered orally in a rat model of arthritis and in a mouse experimental autoimmune encephalomyelitis (EAE) model of multiple sclerosis.


Assuntos
Isoxazóis/síntese química , Isoxazóis/farmacologia , Lisofosfolipídeos/agonistas , Esfingosina/análogos & derivados , Animais , Artrite Experimental/tratamento farmacológico , Células CHO , Movimento Celular/efeitos dos fármacos , Proliferação de Células/efeitos dos fármacos , Cricetinae , Cricetulus , Descoberta de Drogas , Encefalomielite Autoimune Experimental/tratamento farmacológico , Humanos , Imunossupressores/síntese química , Imunossupressores/farmacologia , Sistema Linfático/citologia , Sistema Linfático/efeitos dos fármacos , Linfócitos/efeitos dos fármacos , Camundongos , Camundongos Endogâmicos C57BL , Ratos , Ratos Endogâmicos Lew , Esfingosina/agonistas , Relação Estrutura-Atividade , Timo/citologia , Timo/efeitos dos fármacos
17.
J Biomol Screen ; 18(9): 1072-83, 2013 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-24062352

RESUMO

Transporter proteins are known to play a critical role in affecting the overall absorption, distribution, metabolism, and excretion characteristics of drug candidates. In addition to efflux transporters (P-gp, BCRP, MRP2, etc.) that limit absorption, there has been a renewed interest in influx transporters at the renal (OATs, OCTs) and hepatic (OATPs, BSEP, NTCP, etc.) organ level that can cause significant clinical drug-drug interactions (DDIs). Several of these transporters are also critical for hepatobiliary disposition of bilirubin and bile acid/salts, and their inhibition is directly implicated in hepatic toxicities. Regulatory agencies took action to address transporter-mediated DDI with the goal of ensuring drug safety in the clinic and on the market. To meet regulatory requirements, advanced bioassay technology and automation solutions were implemented for high-throughput transporter screening to provide structure-activity relationship within lead optimization. To enhance capacity, several functional assay formats were miniaturized to 384-well throughput including novel fluorescence-based uptake and efflux inhibition assays using high-content image analysis as well as cell-based radioactive uptake and vesicle-based efflux inhibition assays. This high-throughput capability enabled a paradigm shift from studying transporter-related issues in the development space to identifying and dialing out these concerns early on in discovery for enhanced mechanism-based efficacy while circumventing DDIs and transporter toxicities.


Assuntos
Descoberta de Drogas , Drogas em Investigação/farmacologia , Ensaios de Triagem em Larga Escala , Proteínas de Membrana Transportadoras/metabolismo , Transporte Biológico/efeitos dos fármacos , Sobrevivência Celular/efeitos dos fármacos , Relação Dose-Resposta a Droga , Aprovação de Drogas , Avaliação Pré-Clínica de Medicamentos , Interações Medicamentosas , Drogas em Investigação/química , Drogas em Investigação/metabolismo , Corantes Fluorescentes , Humanos , Rim/efeitos dos fármacos , Rim/metabolismo , Fígado/efeitos dos fármacos , Fígado/metabolismo , Proteínas de Membrana Transportadoras/química , Relação Estrutura-Atividade
18.
J Surg Case Rep ; 2011(6): 4, 2011 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-24949699

RESUMO

We report an interesting and rare case of a vesicocutaneous fistula, which was diagnosed only one year following radiotherapy. A 71 year old gentleman presented with a gangrenous swelling of his left thigh. A copius amount of urine was seen to be draining from the site after initial incision and drainage. Computed tomography with contrast confirmed the diagnosis of a vesicocutaneous fistula. Bilateral nephrostomies were inserted to aid spontaneous closure of the fistula. Previous case reports of vesicocutaneous fistulae involving radiotherapy have described the complication of a fistula occurring many years after the intervention.

19.
J Phys Chem B ; 114(45): 14745-54, 2010 Nov 18.
Artigo em Inglês | MEDLINE | ID: mdl-20684534

RESUMO

Blue-light excitation of cryptochromes and homologues uniformly triggers electron transfer (ET) from the protein surface to the flavin adenine dinucleotide (FAD) cofactor. A cascade of three conserved tryptophan residues has been considered to be critically involved in this photoreaction. If the FAD is initially in its fully oxidized (diamagnetic) redox state, light-induced ET via the tryptophan triad generates a series of short-lived spin-correlated radical pairs comprising an FAD radical and a tryptophan radical. Coupled doublet-pair species of this type have been proposed as the basis, for example, of a biological magnetic compass in migratory birds, and were found critical for some cryptochrome functions in vivo. In this contribution, a cryptochrome-like protein (CRYD) derived from Xenopus laevis has been examined as a representative system. The terminal radical-pair state FAD(•)···W324(•) of X. laevis CRYD has been characterized in detail by time-resolved electron-paramagnetic resonance (TREPR) at X-band microwave frequency (9.68 GHz) and magnetic fields around 345 mT, and at Q-band (34.08 GHz) at around 1215 mT. Different precursor states, singlet versus triplet, of radical-pair formation have been considered in spectral simulations of the experimental electron-spin polarized TREPR signals. Conclusively, we present evidence for a singlet-state precursor of FAD(•)···W324(•) radical-pair generation because at both magnetic fields, where radical pairs were studied by TREPR, net-zero electron-spin polarization has been detected. Neither a spin-polarized triplet precursor nor a triplet at thermal equilibrium can explain such an electron-spin polarization. It turns out that a two-microwave-frequency TREPR approach is essential to draw conclusions on the nature of the precursor electronic states in light-induced spin-correlated radical pair formations.


Assuntos
Criptocromos/química , Criptocromos/metabolismo , Luz , Animais , Espectroscopia de Ressonância de Spin Eletrônica , Transporte de Elétrons/efeitos da radiação , Flavina-Adenina Dinucleotídeo/metabolismo , Radicais Livres/química , Radicais Livres/metabolismo , Modelos Moleculares , Conformação Proteica , Proteínas de Xenopus/química , Proteínas de Xenopus/metabolismo , Xenopus laevis
20.
J Pharm Sci ; 99(4): 2135-52, 2010 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-19780144

RESUMO

Optimizing pharmacokinetic properties to improve oral exposure is a common theme in modern drug discovery. In the present work, in vitro Caco-2 permeability and microsomal half-life screens were utilized in an effort to guide the structure-activity relationship in order to improve the pharmacokinetic properties of novel HIV-1 attachment inhibitors. The relevance of the in vitro screens to in vivo pharmacokinetic properties was first demonstrated with a number of program compounds at the early stage of lead optimization. The Caco-2 permeability, tested at 200 microM, was quantitatively predictive of in vivo oral absorption, with complete absorption occurring at a Caco-2 permeability of 100 nm/s or higher. The liver microsomal half-life screen, conducted at 1 microM substrate concentration, can readily differentiate low-, intermediate-, and high-clearance compounds in rats, with a nearly 1:1 correlation in 12 out of 13 program compounds tested. Among the >100 compounds evaluated, BMS-488043 emerged as a lead, exhibiting a Caco-2 permeability of 178 nm/s and a microsomal half-life predictive of a low clearance (4 mL/min/kg) in humans. These in vitro characteristics translated well to the in vivo setting. The oral bioavailability of BMS-488043 in rats, dogs, and monkeys was 90%, 57%, and 60%, respectively. The clearance was low in all three species tested, with a terminal half-life ranging from 2.4 to 4.7 h. Furthermore, the oral exposure of BMS-488043 was significantly improved (6- to 12-fold in rats and monkeys) compared to the prototype compound BMS-378806 that had a suboptimal Caco-2 permeability (51 nm/s) and microsomal half-life. More importantly, the improvements in preclinical pharmacokinetics translated well to humans, leading to a >15-fold increase in the human oral exposure of BMS-488043 than BMS-378806 and enabling a clinical proof-of-concept for this novel class of anti-HIV agents. The current studies demonstrated the valuable role of in vitro ADME screens in improving oral pharmacokinetics at the lead optimization stage.


Assuntos
Fármacos Anti-HIV/metabolismo , Fármacos Anti-HIV/farmacocinética , Permeabilidade da Membrana Celular , Inibidores da Fusão de HIV/metabolismo , Inibidores da Fusão de HIV/farmacocinética , Microssomos Hepáticos/metabolismo , Piperazinas/metabolismo , Piperazinas/farmacocinética , Administração Oral , Animais , Fármacos Anti-HIV/química , Células CACO-2 , Cães , Inibidores da Fusão de HIV/química , Meia-Vida , Haplorrinos , Humanos , Indóis , Masculino , Piperazinas/química , Ácido Pirúvico , Ratos , Ratos Sprague-Dawley , Relação Estrutura-Atividade
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