Novel (R)-6,6a,7,8,9,10-hexahydro-5H-pyrazino[1,2-a][1,n]naphthyridines as potent and selective agonists of the 5-HT2C receptor

A series of novel (R)-6,6a,7,8,9,10-hexahydro-5H-pyrazino[1,2-a][1,n]naphthyridines were identified as potent and selective agonists of the 5-HT_2C receptor. Optimizations performed on a previously reported series of racemic tetrahydroquinoline-based tricyclic amines, delivered an advanced drug lead, (R)-4-(3,3,3-trifluoropropyl)-6,6a,7,8,9,10-hexahydro-5H-pyrazino[1,2-a][1,8]naphthyridine, which displayed excellent in vitro and in vivo pharmacological profiles.

Discovery of APD334: Design of a Clinical Stage Functional Antagonist of the Sphingosine-1-phosphate-1 Receptor

APD334 was discovered as part of our internal effort to identify potent, centrally available, functional antagonists of the S1P1 receptor for use as next generation therapeutics for treating multiple sclerosis (MS) and other autoimmune diseases. APD334 is a potent functional antagonist of S1P1 and has a favorable PK/PD profile, producing robust lymphocyte lowering at relatively low plasma concentrations in several preclinical species. This new agent was efficacious in a mouse experimental autoimmune encephalomyelitis (EAE) model of MS and a rat collagen induced arthritis (CIA) model and was found to have appreciable central exposure.

(7-Benzyloxy-2,3-dihydro-1H-pyrrolo[1,2-a]indol-1-yl)acetic Acids as S1P1 Functional Antagonists

S1P1 is a validated target for treatment of autoimmune disease, and functional antagonists with superior safety and pharmacokinetic properties are being sought as second generation therapeutics. We describe the discovery and optimization of (7-benzyloxy-2,3-dihydro-1H-pyrrolo[1,2-a]indol-1-yl)acetic acids as potent, centrally available, direct acting S1P1 functional antagonists, with favorable pharmacokinetic and safety properties.

Discovery of 1a,2,5,5a-tetrahydro-1H-2,3-diaza-cyclopropa[a]pentalen-4-carboxamides as potent and selective CB2 receptor agonists

The design and synthesis of novel 1a,2,5,5a-tetrahydro-1H-2,3-diaza-cyclopropa[a]pentalen-4-carboxamide CB2 selective ligands for the potential treatment of pain is described. Compound (R,R)-25 has good balance between CB2 agonist potency and selectivity over CB1, and possesses overall favorable pharmaceutical properties. It also demonstrated robust in vivo efficacy mediated via CB2 activation in the rodent models of inflammatory and osteoarthritis pain after oral administration.

Kinetics of 5-HT2B receptor signaling: profound agonist-dependent effects on signaling onset and duration

The kinetics of drug-receptor interactions can profoundly influence in vivo and in vitro pharmacology. In vitro, the potencies of slowly associating agonists may be underestimated in assays capturing transient signaling events. When divergent receptor-mediated signaling pathways are evaluated using combinations of equilibrium and transient assays, potency differences driven by kinetics may be erroneously interpreted as biased signaling. In vivo, drugs with slow dissociation rates may display prolonged physiologic effects inconsistent with their pharmacokinetic profiles. We evaluated a panel of 5-hydroxytryptamine2B (5-HT2B) receptor agonists in kinetic radioligand binding assays and in transient, calcium flux assays, and inositol phosphate accumulation assays; two functional readouts emanating from Gαq-mediated activation of phospholipase C. In binding studies, ergot derivatives demonstrated slow receptor association and dissociation rates, resulting in significantly reduced potency in calcium assays relative to inositol phosphate accumulation assays. Ergot potencies for activation of extracellular signal-regulated kinases 1 and 2 were also highly time-dependent. A number of ergots produced wash-resistant 5-HT2B signaling that persisted for many hours without appreciable loss of potency, which was not explained simply by slow receptor-dissociation kinetics. Mechanistic studies indicated that persistent signaling originated from internalized or sequestered receptors. This study provides a mechanistic basis for the long durations of action in vivo and wash-resistant effects in ex vivo tissue models often observed for ergots. The 5-HT2B agonist activity of a number of ergot-derived therapeutics has been implicated in development of cardiac valvulopathy in man. The novel, sustained nature of ergot signaling reported here may represent an additional mechanism contributing to the valvulopathic potential of these compounds.

Discovery and characterization of potent and selective 4-oxo-4-(5-(5-phenyl-1,2,4-oxadiazol-3-yl)indolin-1-yl)butanoic acids as S1P₁ agonists

S1P(1) receptor driven lymphopenia has proven utility in the treatment of an array of autoimmune disease states. As a part of our efforts to develop potent and selective S1P(1) receptor agonists, we have identified a novel chemical series of 4-oxo-4-(5-(5-phenyl-1,2,4-oxadiazol-3-yl)indolin-1-yl)butanoic acid S1P(1) receptor agonists.

Myocardial expression, signaling, and function of GPR22: a protective role for an orphan G protein-coupled receptor

G protein-coupled receptors (GPCRs) play an essential role in the regulation of cardiovascular function. Therapeutic modulation of GPCRs has proven to be beneficial in the treatment of human heart disease. Myocardial “orphan” GPCRs, for which the natural ligand is unknown, represent potential novel therapeutic targets for the treatment of heart disease. Here, we describe the expression pattern, signaling pathways, and possible physiological role of the orphan GPR22. GPR22 mRNA analysis revealed a highly restricted expression pattern, with remarkably abundant and selective expression in the brain and heart of humans and rodents. In the heart, GPR22 mRNA was determined to be expressed in all chambers and was comparable with transcript levels of the β1-adrenergic receptor as assessed by Taqman PCR. GPR22 protein expression in cardiac myocytes and coronary arteries was demonstrated in the rat heart by immunohistochemistry. When transfected into HEK-293 cells, GPR22 coupled constitutively to Gi/Go, resulting in the inhibition of adenyl cyclase. No constitutive coupling to Gsor Gqwas observed. Myocardial mRNA expression of GPR22 was dramatically reduced following aortic banding in mice, suggesting a possible role in response to the stress associated with increased afterload. The absence of detectable GPR22 mRNA expression in the hearts of GPR22−/−mice had no apparent effect on normal heart structure or function; however, these mice displayed increased susceptibility to functional decompensation following aortic banding. Thus, we described, for the first time, the expression pattern and signaling for GPR22 and identified a protective role for GPR22 in response to hemodynamic stress resulting from increased afterload.

Four-dimensional multiphoton confocal microscopy: the new frontier in cellular imaging

This paper reviews new developments in microscopy that combine gene transfer technology, multiphoton confocal fluorescence microscopy, live cell imaging and digital imaging techniques that provide unique insights into the complex physiological processes involved in tissue function at the cellular and subcellular level. The evolution of this novel, new technology is discussed with particular attention to earlier achievements in noninvasive ocular surface imaging. The practical basis of confocal microscopy, multiphoton confocal fluorescence microscopy, and the vital fluorescent labeling of cells in living tissues are also discussed. Additionally, one application using retroviral gene transfer to express enhanced green fluorescent protein in living wound healing fibroblasts is presented as an example of how living biology can be studied in situ in four dimensions (x, y, z, time).

Humanized mice mount specific adaptive and innate immune responses to EBV and TSST-1

Here we show that transplantation of autologous human hematopoietic fetal liver CD34+ cells into NOD/SCID mice previously implanted with human fetal thymic and liver tissues results in long-term, systemic human T-cell homeostasis. In addition, these mice show systemic repopulation with human B cells, monocytes and macrophages, and dendritic cells (DCs). T cells in these mice generate human major histocompatibility complex class I- and class II-restricted adaptive immune responses to Epstein-Barr virus (EBV) infection and are activated by human DCs to mount a potent T-cell immune response to superantigens. Administration of the superantigen toxic shock syndrome toxin 1 (TSST-1) results in the specific systemic expansion of human Vbeta2+ T cells, release of human proinflammatory cytokines and localized, specific activation and maturation of human CD11c+ dendritic cells. This represents the first demonstration of long-term systemic human T-cell reconstitution in vivo allowing for the manifestation of the differential response by human DCs to TSST-1.

Human dendritic cell subsets in NOD/SCID mice engrafted with CD34+ hematopoietic progenitors

Distinct human dendritic cell (DC) subsets differentially control immunity. Thus, insights into their in vivo functions are important to understand the launching and modulation of immune responses. We show that nonobese diabetic/LtSz-scid/scid (NOD/SCID) mice engrafted with human CD34+ hematopoietic progenitors develop human myeloid and plasmacytoid DCs. The skin displays immature DCs expressing Langerin, while other tissues display interstitial DCs. Myeloid DCs from these mice induce proliferation of allogeneic CD4 T cells in vitro, and bone marrow human cells containing plasmacytoid DCs release interferon-alpha (IFN-alpha) upon influenza virus exposure. Injection of influenza virus into reconstituted mice triggers IFN-alpha release and maturation of mDCs. Thus, these mice may provide a model to study the pathophysiology of human DC subsets.

In vivo fluorescent labeling of corneal wound healing fibroblasts

Numerous studies have shown that fibroblasts play an important role in corneal wound healing, however, the dynamic cellular events underlying wound tissue organization and contraction remain unclear. The purpose of this study was to develop a system to enable live cell imaging of corneal wound healing fibroblasts in situ. To this end, concentrated preparations of an RD114 pseudotyped MLV-based vector expressing the enhanced green fluorescent protein (EGFP) were evaluated in vitro for gene transfer efficiency using cultured rabbit corneal keratocytes. Primary rabbit keratocytes were efficiently labeled in vitro (up to 50% EGFP(+)) at a low multiplicity of infection (MOI=10). To evaluate this gene transfer vector in vivo, rabbit corneal fibroblasts were transduced by direct application of vector supernatant to injured corneas following lamellar keratectomy. Fluorescent fibroblasts were then visualized in situ using epifluorescence microscopy and multiphoton confocal microscopy of excised fresh tissue at multiple time points from 14 days to four months following gene transfer. Fourteen days post-transduction, labeled fibroblasts expressing EGFP were readily detectable by fluorescence microscopy. Detectable fluorescence was noted up to eight weeks post-transduction. Labeled fibroblasts were detected in clusters located predominantly along the margin circumscribing the wound and to a lesser extent within the wound area. Cell growth in clusters was suggestive of the expansion of individual transduced clones. High-resolution imaging showed fluorescent fibroblasts to have a broad, flattened, dendritic morphology, distinct from the spindle shape of cultured fibroblasts. Utilizing multiphoton confocal microscopy, three-dimensional imaging of viable, labeled cells showed wound healing fibroblasts to be extensively interconnected and multi-layered within the corneal wound. These results demonstrate that rabbit corneal fibroblasts can be efficiently transduced in vitro and in vivo using RD114 pseudotyped MLV-based vectors and that these vectors direct long-term transgene expression without apparent toxicity, pathogenesis or perturbation of native fibroblast morphology. Our data further suggest that, in vivo, wound-healing fibroblasts have a defined life span within the wound.

Production of transgenic rats by lentiviral transduction of male germ-line stem cells

Primary cultures of rat spermatogenic cells that did not bind to collagen matrices were able to colonize and form mature spermatozoa when transferred to testes of recipient males. Up to 73% of the progeny from matings with recipient males were derived from the transferred spermatogenic cells. Subsequently, two populations of germ cells were obtained by selection on laminin matrices. Both populations expressed the spermatogenic cell marker, DAZL, but not the somatic cell marker, vimentin. The cells that bound to laminin represented approximately 5% of the total population and were greatly enriched in ability to colonize a recipient testis, suggesting an enrichment in germ-line stem cells. The colonization potential was maintained for at least 7 days in culture. These cells were subsequently transduced with a lentiviral enhanced GFP reporter vector and then transferred to WT recipient males. After mating, 26 of 44 pups were derived from the cultured donor germ cells, and 13 pups carried the lentiviral transgene. Based on Southern analysis, the transgene was integrated at a different genetic locus in each animal and was transmitted to approximately 50% of pups in the F(2) generation. Thus, by using these procedures, approximately 30% of pups in the F(1) generation inherited and stably transmitted a lentiviral transgene that integrated at various genomic sites.

Engraftment of NOD/SCID mice with human CD34(+) cells transduced by concentrated oncoretroviral vector particles pseudotyped with the feline endogenous retrovirus (RD114) envelope protein

Oncoretrovirus vectors pseudotyped with the feline endogenous retrovirus (RD114) envelope protein produced by the FLYRD18 packaging cell line have previously been shown to transduce human hematopoietic progenitor cells with a greater efficiency than similar amphotropic envelope-pseudotyped vectors. In this report, we describe the production and efficient concentration of RD114-pseudotyped murine leukemia virus (MLV)-based vectors. Following a single round of centrifugation, vector supernatants were concentrated approximately 200-fold with a 50 to 70% yield. Concentrated vector stocks transduced prestimulated human CD34(+) (hCD34(+)) cells with approximately 69% efficiency (n = 7, standard deviation = 4.4%) using a single addition of vector at a low multiplicity of infection (MOI = 5). Introduction of transduced hCD34(+) cells into irradiated NOD/SCID recipients resulted in multilineage engraftment with long-term transgene expression. These data demonstrate that RD114-pseudotyped MLV-based vectors can be efficiently concentrated to high titers and that hCD34(+) cells transduced with concentrated vector stocks retain in vivo repopulating potential. These results highlight the potential of RD114-pseudotyped oncoretrovirus vectors for future clinical implementation in hematopoietic stem cell gene transfer.

Pre-clinical evaluation of an in vitro selection protocol for the enrichment of transduced CD34+ cell-derived human dendritic cells

The efficient genetic modification of CD34+ cell-derived dendritic cells (DC) will provide a significant advancement towards the development of immunotherapy protocols for cancer, autoimmune disorders and infectious diseases. Recent reports have described the transduction of CD34+ cells via retrovirus- and lentivirus-based gene transfer vectors and subsequent differentiation into functional DC. Since there is significant apprehension regarding the clinical uses of HIV-based vectors, in this report, we compare a murine leukemia virus (MLV)- and a human immunodeficiency virus (HIV)-based bicistronic vector for gene transfer into human CD34+ cells and subsequent differentiation into mature DC. Each vector expressed both EGFP and the dominant selectable marker DHFR(L22Y) allowing for the enrichment of marked cells in the presence of the antifolate drug trimetrexate (TMTX). Both MLV-based and HIV-based vectors efficiently transduced cytokine mobilized human peripheral blood CD34+ cells. However, in vitro expansion and differentiation in the presence of GM-CSF, TNF-alpha, Flt-3L, SCF and IL-4 resulted in a reduction in the percentage of DC expressing the transgene. Selection with TMTX during differentiation increased the percentage of marked DC, resulting in up to 79% (MLV vector) and up to 94% (lentivirus-vector) transduced cells expressing EGFP without loss of DC phenotype. Thus, MLV-based vectors and in vitro selection of transduced human DC show great promise for immunotherapy protocols.

Efficient, long-term transgene expression in Xenopus laevis dermal melanophores

Xenopus laevis dermal melanophores provide an excellent model system for the investigation of complex cellular processes. Specifically, the expression of exogenous genes in Xenopus melanophores is the basis of recombinant bioassays for the study of receptor-ligand interactions. However, due to their slow rate of cell division and to the relatively low efficiency of current transfection protocols, long-term expression of exogenous genes and the generation of stable melanophore cell lines remains problematic. In this report we demonstrate the efficient, long-term expression of two exogenous proteins, the enhanced green fluorescent protein (EGFP) and the human CD4 (hCD4) cell surface receptor, following stable introduction into Xenopus melanophores via an HIV-1 based vector. Transduction of melanophores with the EGFP expression vector resulted in up to 80% EGFP+ cells. After 1 year in continuous culture in the absence of antibiotic selection, more than 60% of the cells remained EGFP+. Furthermore, we demonstrate the expression of hCD4 melanophores for over 9 months in continuous culture in the absence of antibiotic selection. Our results indicate that lentivirus vectors provide an efficient means of introducing genetic information into Xenopus melanophores, resulting in sustained levels of gene expression. The significance of this gene transfer system for the study of cellular signal transduction pathways is discussed.

In vitro generation of Epstein-Barr virus-specific cytotoxic T cells in patients receiving haplo-identical allogeneic stem cell transplantation

Use of a partially mismatched related donor (PMRD) is an option for patients who require allogeneic transplantation but do not have a matched sibling or unrelated donor. Epstein-Barr virus (EBV)-induced lymphoma is a major cause of mortality after PMRD transplantation. In this study, we present a clinical grade culture system for donor-derived EBV-specific cytotoxic T cells (CTLs) that do not recognize haplo-identical recipient cells. The EBV-specific CTLs were tested for cytolytic specificity and other functional properties, including ability to transgress into tissues, propensity for apoptosis, degree of clonality, stability of dominant T-cell clones, and Tc and Th phenotypes. The EBV-specific CTLs were routinely expanded to greater than 80 x 10(6) over a period of 5 weeks, which is sufficient for clinical application. A CD8+ phenotype predominated, and the CTLs were highly specific for donor lymphoblastoid cell lines (LCLs) without killing of recipient targets or K562. Vbeta spectratyping showed an oligoclonal population that was stable on prolonged culture. The EBV-specific CTLs were activated (D-related human leukocyte antigen [HLA-DR+], L-selectin+/-) and of memory phenotype (CD45RO+). Expression of the integrin VLA-4 suggested that these CTLs could adhere to endothelium and migrate into tissues. The Bcl-2 message was upregulated, which may protect the CTLs from the apoptosis. The first demonstration of overexpression of bcl-2 in human memory CTLs. In addition, we show that lymphoblastoid cell lines used to generate CTLs are readily genetically modified with recombinant lentivirus, indicating that genetically engineered antigen presentation is feasible.

Long-term engraftment of nonobese diabetic/severe combined immunodeficient mice with human CD34+ cells transduced by a self-inactivating human immunodeficiency virus type 1 vector

Human hematopoietic cells with in vivo repopulating potential hold much promise as a target for corrective gene transfer for numerous inherited or acquired hematopoietic disorders. Here we demonstrate long-term hematopoietic reconstitution of nonobese diabetic/severe combined immunodeficient (NOD/SCID) mice with human CD34(+) cells transduced by an HIV-1-based self-inactivating (SIN) vector encoding the enhanced green fluorescent protein (EGFP). Human umbilical cord CD34(+) cells were transduced (up to 76%) at a low multiplicity of infection (MOI of 5) in the absence of cytokine prestimulation. Introduction of transduced hCD34(+) cells into irradiated recipients resulted in multilineage engraftment and stable transgene expression for 18 weeks posttransplantation. Bone marrow from transplanted mice contained up to 50% hCD45(+) cells and up to 63% hCD45(+)/EGFP(+) cells. Analysis of extramedullar splenic reconstitution showed up to 13% hCD45(+) cells and up to 41% hCD45(+)/EGFP(+) cells. Analysis of human progenitor cells isolated from bone marrow of recipient animals showed equivalent percentages of EGFP(+) colony-forming cells (CFCs) by fluorescence microscopy and by PCR analysis of provirus sequences, indicating minimal transgene silencing in vivo. These findings demonstrate the utility of lentivirus-based SIN vectors for hematopoietic stem cell gene transfer and provide strong support for their future clinical evaluation.

Thymocyte differentiation from lentivirus-marked CD34(+) cells in infant and adult human thymus

Changes in thymic function and immune system homeostasis associated with HIV infection or chemotherapy have significant effects on the ability of patients to maintain a complete T cell receptor repertoire. Therefore, the development of in vitro systems to evaluate thymic function in children and adults may aid in the understanding of thymopoiesis and the development of new therapies to improve thymic output. Here we use a lentivirus-based gene transfer system to mark CD34(+) cells with EGFP and follow their differentiation into CD4(+) and CD8(+) single positive thymocytes in human thymic organ cultures. Lentivirus-marked cells entered the thymus and were detected in both the cortex and medulla. Pretreatment of the thymus with 2-deoxyguanosine depleted resident thymocytes and significantly increased the percentage of EGFP(+) thymocytes. High frequency gene transfer into CD34(+) cells and maintained expression throughout differentiation allows for the in vitro assessment of thymic function. In thymuses ranging in age from fetal to adult we observed EGFP(+) thymocytes at all stages of development suggesting that thymuses of all ages are capable of accepting new T cell progenitors and contributing to the maintenance of T cell homeostasis.

In vitro selection of lentivirus vector-transduced human CD34+ cells

Human CD34(+) cells with in vivo repopulating potential hold much promise as a target for corrective gene transfer for numerous hematopoietic disorders. However, the efficient introduction of exogenous genes into this small, quiescent population of cells continues to present a significant challenge. To circumvent the need for high initial transduction efficiency of human hematopoietic cells, we investigated a dominant selection strategy using a variant of the DHFR gene (DHFR(L22Y)). For this purpose, we constructed a lentivirus-based bicistronic vector expressing EGFP and DHFR(L22Y). Here we demonstrate efficient in vitro selection and enrichment of lentivirus vector-transduced human CD34(+) hematopoietic cells from fetal liver, umbilical cord blood, bone marrow, and peripheral blood after cytokine mobilization. Growth of transduced human CD34(+) cells in semisolid culture under selective pressure resulted in enrichment of transduced progenitor cells to 99.5% (n = 14). Selection for DHFR(L22Y)(+) cells after expansion of transduced progenitors in liquid culture resulted in a 7- to 13-fold increase in the percentage of marked cells. Thus we have shown that transduced human hematopoietic cells may be effectively enriched in vitro by dominant selection, suggesting that development of such strategies holds promise for future in vivo application.

HIV-1 protease regulation: the role of the major homology region and adjacent C-terminal capsid sequences

The maturation of human immunodeficiency type-1 virions is accomplished through the proteolytic processing of Gag and GagPol precursor proteins by the viral protease (PR). Since virions must be assembled at the cell surface from uncleaved precursor molecules, intracellular activation of PR must be inhibited. We have previously developed a system where the intracellular activity of PR, associated with GagPol, was inhibited by the expression of Gag in trans. The disproportionate synthesis of Gag inhibits the activation of PR in the cytoplasm. Sequences capable of mediating this inhibition were localized to capsid. In this communication, the region of HIV-1 capsid capable of mediating inhibition was further defined and shown to require the major homology region of capsid within Gag.

Regulation of intracellular human immunodeficiency virus type-1 protease activity

The maturation of HIV-1 virions is accomplished through the proteolytic cleavage of Gag and GagPol precursor polyproteins by the viral-encoded protease (PR). Since virions are assembled from unprocessed polyproteins, the intracellular activation of PR must be limited. An experimental system was established that allows the investigation of the intracellular regulation of PR activity. By expressing Gag in trans with the GagPol precursor, downregulation of the intracellular PR activity associated with GagPol was demonstrated. Inhibition of PR activity was dependent upon the context of PR expression. Sequences capable of mediating this inhibition were localized to capsid. A mechanism through which Gag regulates PR activity is proposed whereby the disproportionate synthesis of Gag inhibits the activation of PR in the cytoplasm. Further elucidation of the mechanism of intracellular inhibition of PR activity may facilitate the development of novel PR inhibitors capable of inhibiting viral replication in vivo.