An orally administered enzyme therapeutic for homocystinuria that suppresses homocysteine by metabolizing methionine in the gastrointestinal tract.

Classical homocystinuria (HCU) is a rare inborn error of amino acid metabolism characterized by accumulation of homocysteine, an intermediate product of methionine metabolism, leading to significant systemic toxicities, particularly within the vascular, skeletal, and ocular systems. Most patients require lifelong dietary therapy with severe restriction of natural protein to minimize methionine intake, and many patients still struggle to maintain healthy homocysteine levels. Since eliminating methionine from the diet reduces homocysteine levels, we hypothesized that an enzyme that can degrade methionine within the gastrointestinal (GI) tract could help HCU patients maintain healthy levels while easing natural protein restrictions. We describe the preclinical development of CDX-6512, a methionine gamma lyase (MGL) enzyme that was engineered for stability and activity within the GI tract for oral administration to locally degrade methionine. CDX-6512 is stable to low pH and intestinal proteases, enabling it to survive the harsh GI environment without enteric coating and to degrade methionine freed from dietary protein within the small intestine. Administering CDX-6512 to healthy non-human primates following a high protein meal led to a dose-dependent suppression of plasma methionine. In Tg-I278T Cbs-/- mice, an animal model that recapitulates aspects of HCU disease including highly elevated serum homocysteine levels, oral dosing of CDX-6512 after a high protein meal led to suppression in serum levels of both methionine and homocysteine. When animals received a daily dose of CDX-6512 with a high protein meal for two weeks, the Tg-I278T Cbs-/- mice maintained baseline homocysteine levels, whereas homocysteine levels in untreated animals increased by 39%. These preclinical data demonstrate the potential of CDX-6512 as an oral enzyme therapy for HCU.

Direct Tie2 Agonists Stabilize Vasculature for the Treatment of Diabetic Macular Edema.

Purpose: Diabetic macular edema (DME) is the leading cause of vision loss and blindness among working-age adults. Although current intravitreal anti-vascular endothelial growth factor (VEGF) therapies improve vision for many patients with DME, approximately half do not achieve the visual acuity required to drive. We therefore sought additional approaches to resolve edema and improve vision for these patients. Methods: We explored direct agonists of Tie2, a receptor known to stabilize vasculature and prevent leakage. We identified a multivalent PEG-Fab conjugate, Tie2.1-hexamer, that oligomerizes Tie2 and drives receptor activation and characterized its activities in vitro and in vivo. Results: Tie2.1-hexamer normalized and stabilized intercellular junctions of stressed endothelial cell monolayers in vitro, suppressed vascular leak in mice under conditions where anti-VEGF alone was ineffective, and demonstrated extended ocular exposure and robust pharmacodynamic responses in non-human primates. Conclusions: Tie2.1-hexamer directly activates the Tie2 pathway, reduces vascular leak, and is persistent within the vitreal humor. Translational Relevance: Our study presents a promising potential therapeutic for the treatment of DME.

An Allosteric Anti-tryptase Antibody for the Treatment of Mast Cell-Mediated Severe Asthma.

Severe asthma patients with low type 2 inflammation derive less clinical benefit from therapies targeting type 2 cytokines and represent an unmet need. We show that mast cell tryptase is elevated in severe asthma patients independent of type 2 biomarker status. Active ß-tryptase allele count correlates with blood tryptase levels, and asthma patients carrying more active alleles benefit less from anti-IgE treatment. We generated a noncompetitive inhibitory antibody against human ß-tryptase, which dissociates active tetramers into inactive monomers. A 2.15 Å crystal structure of a ß-tryptase/antibody complex coupled with biochemical studies reveal the molecular basis for allosteric destabilization of small and large interfaces required for tetramerization. This anti-tryptase antibody potently blocks tryptase enzymatic activity in a humanized mouse model, reducing IgE-mediated systemic anaphylaxis, and inhibits airway tryptase in Ascaris-sensitized cynomolgus monkeys with favorable pharmacokinetics. These data provide a foundation for developing anti-tryptase as a clinical therapy for severe asthma.

Tetravalent biepitopic targeting enables intrinsic antibody agonism of tumor necrosis factor receptor superfamily members.

Agonism of members of the tumor necrosis factor receptor superfamily (TNFRSF) with monoclonal antibodies is of high therapeutic interest due to their role in immune regulation and cell proliferation. A major hurdle for pharmacologic activation of this receptor class is the requirement for high-order clustering, a mechanism that imposes a reliance in vivo on Fc receptor-mediated crosslinking. This extrinsic dependence represents a potential limitation of virtually the entire pipeline of agonist TNFRSF antibody drugs, of which none have thus far been approved or reached late-stage clinical trials. We show that tetravalent biepitopic targeting enables robust intrinsic antibody agonism for two members of this family, OX40 and DR5, that is superior to extrinsically crosslinked native parental antibodies. Tetravalent biepitopic anti-OX40 engagement co-stimulated OX40low cells, obviated the requirement for CD28 co-signal for T cell activation, and enabled superior pharmacodynamic activity relative to native IgG in a murine vaccination model. This work establishes a proof of concept for an engineering approach that addresses a major gap for the therapeutic activation of this important receptor class.

Therapeutic antibodies reveal Notch control of transdifferentiation in the adult lung.

Prevailing dogma holds that cell-cell communication through Notch ligands and receptors determines binary cell fate decisions during progenitor cell divisions, with differentiated lineages remaining fixed. Mucociliary clearance in mammalian respiratory airways depends on secretory cells (club and goblet) and ciliated cells to produce and transport mucus. During development or repair, the closely related Jagged ligands (JAG1 and JAG2) induce Notch signalling to determine the fate of these lineages as they descend from a common proliferating progenitor. In contrast to such situations in which cell fate decisions are made in rapidly dividing populations, cells of the homeostatic adult airway epithelium are long-lived, and little is known about the role of active Notch signalling under such conditions. To disrupt Jagged signalling acutely in adult mammals, here we generate antibody antagonists that selectively target each Jagged paralogue, and determine a crystal structure that explains selectivity. We show that acute Jagged blockade induces a rapid and near-complete loss of club cells, with a concomitant gain in ciliated cells, under homeostatic conditions without increased cell death or division. Fate analyses demonstrate a direct conversion of club cells to ciliated cells without proliferation, meeting a conservative definition of direct transdifferentiation. Jagged inhibition also reversed goblet cell metaplasia in a preclinical asthma model, providing a therapeutic foundation. Our discovery that Jagged antagonism relieves a blockade of cell-to-cell conversion unveils unexpected plasticity, and establishes a model for Notch regulation of transdifferentiation.

The trimeric serine protease HtrA1 forms a cage-like inhibition complex with an anti-HtrA1 antibody.

High temperature requirement A1 (HtrA1) is a trypsin-fold serine protease implicated in the progression of age-related macular degeneration (AMD). Our interest in an antibody therapy to neutralize HtrA1 faces the complication that the target adopts a trimeric arrangement, with three active sites in close proximity. In the present study, we describe antibody 94, obtained from a human antibody phage display library, which forms a distinct macromolecular complex with HtrA1 and inhibits the enzymatic activity of recombinant and native HtrA1 forms. Using biochemical methods and negative-staining EM we were able to elucidate the molecular composition of the IgG94 and Fab94 complexes and the associated inhibition mechanism. The 246-kDa complex between the HtrA1 catalytic domain trimer (HtrA1_Cat) and Fab94 had a propeller-like organization with one Fab bound peripherally to each protomer. Low-resolution EM structures and epitope mapping indicated that the antibody binds to the surface-exposed loops B and C of the catalytic domain, suggesting an allosteric inhibition mechanism. The HtrA1_Cat-IgG94 complex (636 kDa) is a cage-like structure with three centrally located IgG94 molecules co-ordinating two HtrA1_Cat trimers and the six active sites pointing into the cavity of the cage. In both complexes, all antigen-recognition regions (paratopes) are found to bind one HtrA1 protomer and all protomers are bound by a paratope, consistent with the complete inhibition of enzyme activity. Therefore, in addition to its potential therapeutic usefulness, antibody 94 establishes a new paradigm of multimeric serine protease inhibition.

Thymic stromal lymphopoietin receptor blockade reduces allergic inflammation in a cynomolgus monkey model of asthma.

BACKGROUND: Thymic stromal lymphopoietin (TSLP) pathway blockade is a potential strategy for asthma treatment because the main activities of TSLP are activation of myeloid dendritic cells (mDCs) and modulation of cytokine production by mast cells. TSLP-activated mDCs prime the differentiation of naive T cells into inflammatory TH2 cells. OBJECTIVE: We sought to investigate mechanisms underlying the development of allergic lung inflammation in cynomolgus monkeys using gene expression profiling and to assess the effect of thymic stromal lymphopoietin receptor (TSLPR) blockade in this model. METHODS: An mAb against human TSLPR was generated and confirmed to be cross-reactive to cynomolgus monkey. Animals were dosed weekly with either vehicle or anti-TSLPR mAb for 6 weeks, and their responses to allergen challenge at baseline, week 2, and week 6 were assessed. RESULTS: After 6 weeks of treatment, anti-TSLPR mAb-treated animals showed reduced bronchoalveolar lavage (BAL) fluid eosinophil counts, reduced airway resistance in response to allergen challenge, and reduced IL-13 cytokine levels in BAL fluid compared with values seen in vehicle-treated animals. Expression profiling of BAL fluid cells collected before and after challenge showed a group of genes upregulated by allergen challenge that strongly overlapped with 11 genes upregulated in dendritic cells (DCs) when in vitro stimulated by TSLP (TSLP-DC gene signature). The number of genes differentially expressed in response to challenge was reduced in antibody-treated animals after 6 weeks relative to vehicle-treated animals. Expression of the TSLP-DC gene signature was also significantly reduced in antibody-treated animals. CONCLUSION: These results demonstrate promising efficacy for TSLPR blockade in an allergic lung inflammation model in which TSLP activation of mDCs might play a key role.

Suppression of glomerulonephritis in lupus-prone NZB × NZW mice by RN486, a selective inhibitor of Bruton's tyrosine kinase.

OBJECTIVE: Bruton's tyrosine kinase (BTK) plays a critical role in B cell development and function. We recently described a selective BTK inhibitor, RN486, that blocks B cell receptor (BCR) and Fcγ receptor signaling and is efficacious in animal models of arthritis. The aim of this study was to examine the potential efficacy of BTK in systemic lupus erythematosus (SLE), using an NZB × NZW mouse model of spontaneous SLE. METHODS: Mice received RN486 or its vehicle (administered in chow) at a final concentration of 30 mg/kg for 8 weeks, starting at 32 weeks of age. RESULTS: The administration of RN486 completely stopped disease progression, as determined by histologic and functional analyses of glomerular nephritis. The efficacy was associated with striking inhibition of B cell activation, as demonstrated by a significant reduction in CD69 expression in response to BCR crosslinking. RN486 markedly reduced the secretion of IgG anti-double-stranded DNA (anti-dsDNA) secretion, as determined by enzyme-linked immunosorbent and enzyme-linked immunospot assays. Flow cytometric analysis demonstrated depletion of CD138(high) B220(low) plasma cells in the spleen. RN486 inhibited secretion of IgG anti-dsDNA but not IgM anti-dsDNA, suggesting that pharmacologic blockade of BTK resembles the reported transgenic expression of low levels of endogenous BTK in B cells. In addition, RN486 may also impact the effector function of autoantibodies, as evidenced by a significant reduction in immune complex-mediated activation of human monocytes in vitro and down-regulation of the expression of macrophage-related and interferon-inducible genes in both the kidneys and spleens of treated mice. CONCLUSION: Collectively, our data suggest that BTK inhibitors may simultaneously target autoantibody-producing and effector cells in SLE, thus constituting a promising therapeutic alternative for this disease.

RAS mutations in cutaneous squamous-cell carcinomas in patients treated with BRAF inhibitors.

BACKGROUND: Cutaneous squamous-cell carcinomas and keratoacanthomas are common findings in patients treated with BRAF inhibitors. METHODS: We performed a molecular analysis to identify oncogenic mutations (HRAS, KRAS, NRAS, CDKN2A, and TP53) in the lesions from patients treated with the BRAF inhibitor vemurafenib. An analysis of an independent validation set and functional studies with BRAF inhibitors in the presence of the prevalent RAS mutation was also performed. RESULTS: Among 21 tumor samples, 13 had RAS mutations (12 in HRAS). In a validation set of 14 samples, 8 had RAS mutations (4 in HRAS). Thus, 60% (21 of 35) of the specimens harbored RAS mutations, the most prevalent being HRAS Q61L. Increased proliferation of HRAS Q61L-mutant cell lines exposed to vemurafenib was associated with mitogen-activated protein kinase (MAPK)-pathway signaling and activation of ERK-mediated transcription. In a mouse model of HRAS Q61L-mediated skin carcinogenesis, the vemurafenib analogue PLX4720 was not an initiator or a promoter of carcinogenesis but accelerated growth of the lesions harboring HRAS mutations, and this growth was blocked by concomitant treatment with a MEK inhibitor. CONCLUSIONS: Mutations in RAS, particularly HRAS, are frequent in cutaneous squamous-cell carcinomas and keratoacanthomas that develop in patients treated with vemurafenib. The molecular mechanism is consistent with the paradoxical activation of MAPK signaling and leads to accelerated growth of these lesions. (Funded by Hoffmann-La Roche and others; ClinicalTrials.gov numbers, NCT00405587, NCT00949702, NCT01001299, and NCT01006980.).

The hepatitis C virus NS5A inhibitor (BMS-790052) alters the subcellular localization of the NS5A non-structural viral protein.

The hepatitis C virus (HCV) non-structural (NS) 5A protein plays an essential role in the replication of the viral RNA by the membrane-associated replication complex (RC). Recently, a putative NS5A inhibitor, BMS-790052, exhibited the highest potency of any known anti-HCV compound in inhibiting HCV replication in vitro and showed a promising clinical effect in HCV-infected patients. The precise mechanism of action for this new class of potential anti-HCV therapeutics, however, is still unclear. In order to gain further insight into its mode of action, we sought to test the hypothesis that the antiviral effect of BMS-790052 might be mediated by interfering with the functional assembly of the HCV RC. We observed that BMS-790052 indeed altered the subcellular localization and biochemical fractionation of NS5A. Taken together, our data suggest that NS5A inhibitors such as BMS-790052 can suppress viral genome replication by altering the proper localization of NS5A into functional RCs.

Exploration of piperidine-4-yl-aminopyrimidines as HIV-1 reverse transcriptase inhibitors. N-Phenyl derivatives with broad potency against resistant mutant viruses.

Further investigation of the recently reported piperidine-4-yl-aminopyrimidine class of non-nucleoside reverse transcriptase inhibitors (NNRTIs) has been carried out. Thus, preparation of a series of N-phenyl piperidine analogs resulted in the identification of 3-carboxamides as a particularly active series. Analogs such as 28 and 40 are very potent versus wild-type HIV-1 and a broad range of NNRTI-resistant mutant viruses. Synthesis, structure-activity relationship (SAR), clearance data, and crystallographic evidence for the binding motif are discussed.

The mRNA level of Charcot-Leyden crystal protein/galectin-10 is a marker for CRTH2 activation in human whole blood in vitro.

CRTH2 is one of the prostaglandin D2 receptors and plays a proinflammatory role in allergic diseases. Gene expression markers in whole blood induced by CRTH2 activation have not previously been reported. Using microarray analyses of 54 675 genes, we revealed modest gene expression changes in human whole blood stimulated in vitro by a selective CRTH2 agonist, DK-PGD2. Five genes were found to exhibit 1.5- to 2.6-fold changes in expression. The expression of Charcot-Leyden crystal protein/galectin-10 (CLC/Gal-10) in particular was consistently enhanced in human whole blood stimulated by DK-PGD2, as confirmed by quantitative real-time polymerase chain reaction analyses. DK-PGD(2)-induced increases in blood CLC/Gal-10 mRNA levels were largely attenuated by the CRTH2 antagonist CAY10471.Thus, the DK-PGD2-induced CLC/Gal-10 mRNA level can serve as a potential marker for monitoring pharmacodynamic effects of blood exposure to CRTH2 modulating agents.

Cyclic amide bioisosterism: strategic application to the design and synthesis of HCV NS5B polymerase inhibitors.

Conformational modeling has been successfully applied to the design of cyclic bioisosteres used to replace a conformationally rigid amide bond in a series of thiophene carboxylate inhibitors of HCV NS5B polymerase. Select compounds were equipotent with the original amide series. Single-point mutant binding studies, in combination with inhibition structure-activity relationships, suggest this new series interacts at the Thumb-II domain of NS5B. Inhibitor binding at the Thumb-II site was ultimately confirmed by solving a crystal structure of 8b complexed with NS5B.

Discovery of piperidin-4-yl-aminopyrimidines as HIV-1 reverse transcriptase inhibitors. N-benzyl derivatives with broad potency against resistant mutant viruses.

An analysis of the binding motifs of known HIV-1 non-nucleoside reverse transcriptase inhibitors has led to discovery of novel piperidine-linked aminopyrimidine derivatives with broad activity against wild-type as well as drug-resistant mutant viruses. Notably, the series retains potency against the K103N/Y181C and Y188L mutants, among others. Thus, the N-benzyl compound 5k has a particularly attractive profile. Synthesis and SAR are presented and discussed, as well as crystal structures relating to the binding motifs.

EGG-4 and EGG-5 Link Events of the Oocyte-to-Embryo Transition with Meiotic Progression in C. elegans.

The molecular underpinnings of the oocyte-to-embryo transition are poorly understood. Here we show that two protein tyrosine phosphatase-like (PTPL) family proteins, EGG-4 and EGG-5, are required for key events of the oocyte-to-embryo transition in Caenorhabditis elegans. The predicted EGG-4 and EGG-5 amino acid sequences are 99% identical and their functions are redundant. In embryos lacking EGG-4 and EGG-5, we observe defects in meiosis, polar body formation, the block to polyspermy, F-actin dynamics, and eggshell deposition. During oogenesis, EGG-4 and EGG-5 assemble at the oocyte cortex with the previously identified regulators or effectors of the oocyte-to-embryo transition EGG-3, CHS-1, and MBK-2 [1, 2]. All of these molecules share a complex interdependence with regards to their dynamics and subcellular localization. Shortly after fertilization, EGG-4 and EGG-5 are required to properly coordinate a redistribution of CHS-1 and EGG-3 away from the cortex during meiotic anaphase I. Therefore, EGG-4 and EGG-5 are not only required for critical events of the oocyte-to-embryo transition but also link the dynamics of the regulatory machinery with the advancing cell cycle.

Slow binding inhibition and mechanism of resistance of non-nucleoside polymerase inhibitors of hepatitis C virus.

The binding affinity of four palm and thumb site representative non-nucleoside inhibitors (NNIs) of HCV polymerase NS5B to wild-type and resistant NS5B polymerase proteins was determined, and the influence of RNA binding on NNI binding affinity was investigated. NNIs with high binding affinity potently inhibited HCV RNA polymerase activity and replicon replication. Among the compounds tested, HCV-796 showed slow binding kinetics to NS5B. The binding affinity of HCV-796 to NS5B increased 27-fold over a 3-h incubation period with an equilibrium Kd of 71 +/- 2 nm. Slow binding kinetics of HCV-796 was driven by slow dissociation from NS5B with a k(off) of 4.9 +/- 0.5 x 10(-4) s(-1). NS5B bound a long, 378-nucleotide HCV RNA oligonucleotide with high affinity (Kd = 6.9 +/- 0.3 nm), whereas the binding affinity was significantly lower for a short, 21-nucleotide RNA (Kd = 155.1 +/- 16.2 nm). The formation of the NS5B-HCV RNA complex did not affect the slow binding kinetics profile and only slightly reduced NS5B binding affinity of HCV-796. The magnitude of reduction of NNI binding affinity for the NS5B proteins with various resistance mutations in the palm and thumb binding sites correlated well with resistance -fold shifts in NS5B polymerase activity and replicon assays. Co-crystal structures of NS5B-Con1 and NS5B-BK with HCV-796 revealed a deep hydrophobic binding pocket at the palm region of NS5B. HCV-796 interaction with the induced binding pocket on NS5B is consistent with slow binding kinetics and loss of binding affinity with mutations at amino acid position 316.

Diphenyl ether non-nucleoside reverse transcriptase inhibitors with excellent potency against resistant mutant viruses and promising pharmacokinetic properties.

Non-nucleoside reverse transcriptase inhibitors (NNRTIs) are part of the preferred treatment regimens for individuals infected with HIV. These NNRTI-based regimens are efficacious, but the most popular NNRTIs have a low genetic barrier to resistance and have been associated with adverse events. There is therefore still a need for efficacious antiviral medicines that facilitate patient adherence and allow durable suppression of viral replication. As part of an extensive program targeted toward the discovery of NNRTIs that have favorable pharmacokinetic properties, good potency against NNRTI-resistant viruses, and a high genetic barrier to drug resistance, we focused on the optimization of a series of diaryl ether NNRTIs. In the course of this effort, we employed molecular modeling to design a new set of NNRTIs that that are active against wild-type HIV and key NNRTI-resistant mutant viruses. The structure-activity relationships observed in this series of compounds provide insight into the structural features required for NNRTIs that inhibit the replication of a wide range of mutant viruses. Selected compounds have promising pharmacokinetic profiles.

Design of annulated pyrazoles as inhibitors of HIV-1 reverse transcriptase.

Non-nucleoside reverse transcriptase inhibitors (NNRTIs) are recommended components of preferred combination antiretroviral therapies used for the treatment of HIV. These regimens are extremely effective in suppressing virus replication. Structure-based optimization of diaryl ether inhibitors led to the discovery of a new series of pyrazolo[3,4-c]pyridazine NNRTIs that bind the reverse transcriptase enzyme of human immunodeficiency virus-1 (HIV-RT) in an expanded volume relative to most other inhibitors in this class.The binding mode maintains the beta13 and beta14 strands bearing Pro236 in a position similar to that in the unliganded reverse transcriptase structure, and the distribution of interactions creates the opportunity for substantial resilience to single point mutations. Several pyrazolopyridazine NNRTIs were found to be highly effective against wild-type and NNRTI-resistant viral strains in cell culture.

Genes required for the common miracle of fertilization in Caenorhabditis elegans.

Fertilization involves multiple layers of sperm-egg interactions that lead to gamete fusion and egg activation. There must be specific molecules required for these interactions. The challenge is to determine the identity of the genes encoding these molecules and how their protein products function. The nematode worm Caenorhabditis elegans has emerged as an efficient model system for gene discovery and understanding the molecular mechanisms of fertilization. The primary advantage of the C. elegans system is the ability to isolate and maintain mutants that affect sperm or eggs and no other cells. In this review we describe progress and challenges in the analysis of genes required for gamete interactions and egg activation in the worm.