Byron Li
Novartis
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Featured researches published by Byron Li.
Investigative Ophthalmology & Visual Science | 2009
Stephanie C. Joachim; Franz H. Grus; Daniela Kraft; Kisha White-Farrar; George Barnes; Mike Barbeck; Shahram Ghanaati; Shutong Cao; Byron Li; M. B. Wax
PURPOSE Increased serum antibodies against heat shock protein 27 (HSP27) have been identified in patients with glaucoma. Immunization with HSP27 caused retinal ganglion cell (RGC) loss in animals. The authors analyzed whether HSP27 immunization not only causes RGC loss but also affects systemic antibody patterns. METHODS Rats were immunized with HSP27 and were surveyed for 4, 5, and 6 weeks (groups 1-3). Control animals were humanely killed after 6 weeks (group 4). Intraocular pressure was measured before and 2 and 4 weeks after immunization. Fundus images were taken at the same time. Retinal flatmounts were prepared, and Brn-3a labeled RGCs were counted. Serum was collected during the study to detect antibody patterns against retinal antigens through Western blot analysis and mass spectrometry techniques. Patterns were analyzed by multivariate statistical techniques, and biomarkers were identified with the use of mass spectrometry. RESULTS No significant changes in intraocular pressure were observed, and no fundus abnormalities were noted. The animals immunized with HSP27 showed lower RGC density than controls (P < 0.05). Two and 4 weeks after immunization, we detected a significant difference in antibody profiles between groups 1 and 4 (P < 0.05) and groups 3 and 4 (P < 0.05). Proteins with different antibody level expression after immunization included heat shock protein 90, alpha-enolase, and glyceraldehyde-3-phosphate dehydrogenase. CONCLUSIONS After immunization with HSP27, animals showed IOP-independent RGC loss and changes in serum antibody patterns. Thus, this model might be a beneficial approach to study the development and effects of anti-retinal antibodies and their involvement in RGC loss.
Survey of Ophthalmology | 2000
George Barnes; Byron Li; Tom Dean; Michael L. Chandler
OBJECTIVES Using a three-way crossover study design, we compared the effects of brinzolamide 2%, dorzolamide 2%, and placebo (vehicle) on microvascular optic nerve head (ONH) blood flow, intraocular pressure (IOP), blood pressure, heart rate, and acid-base balance in nine acepromazine-tranquilized Dutch-belted rabbits. METHODS Baseline measurements were taken before treatment and after drug-free washout periods of 7-14 days. Microvascular ONH blood flow was measured with a fundus camera-based laser Doppler flowmeter (LDF). Intraocular pressure was measured with a Tono-Pen XL. One drop of brinzolamide, dorzolamide, or vehicle was administered twice daily (9 A.M. and 5 P.M.) in right eyes only for 7 days. Experimental measurements were made 90 minutes after the 9 A.M. topical dose was administered on day 8. RESULTS ONH blood flow was significantly increased (P< or =0.05) in carbonic anhydrase inhibitor (CAI)-treated rabbits, as compared with vehicle-treated controls. The percent increase from baseline was 11.2+/-1.8% in brinzolamide-treated animals and 8.4+/-4.3% in dorzolamide-treated animals. Compared with controls, IOP in the brinzolamide- and dorzolamide-treated groups was significantly decreased (P< or =0.05). The changes in ONH blood flow and IOP were not significantly different between the CAI treatment groups. Small but significant changes in systemic blood gas tensions and pH were present in both CAI treatment groups, as compared with the vehicle group. Systemic blood pressure and heart rate were not significantly changed. CONCLUSIONS Topical ocular CAI treatment for 1 week with either brinzolamide or dorzolamide significantly reduced IOP and significantly increased ONH blood flow in tranquilized Dutch-belted rabbits, while eliciting minimal systemic acid-base balance disturbances.
European Journal of Pharmacology | 2016
Ganesh Prasanna; Byron Li; Muneto Mogi; Dennis S Rice
Intraocular pressure (IOP) lowering drugs that are approved for the treatment of glaucoma and ocular hypertension have limited activity on increasing aqueous humor movement through the trabecular meshwork and Schlemms canal (TM/SC). The TM/SC complex is considered the conventional outflow pathway and is a primary site of increased resistance to aqueous humor outflow in glaucoma. Novel mechanisms that enhance conventional outflow have shown promise in IOP reduction via modulation of several pathways including Rho kinase, nitric oxide/soluble guanylate cyclase/cGMP, adenosine A1, prostaglandin EP4/cAMP, and potassium channels. The clinical translatability of these pharmacological modulators based on pre-clinical efficacy models is currently being explored. In addition, identification of pathways from GWAS and other studies involving transgenic rodent models with elevated/reduced IOP phenotypes have begun to yield additional insights into IOP regulation and serve as a source for the next generation of IOP lowering targets. Lastly, improvements in drug delivery technologies to enable sustained IOP reduction are also discussed.
Experimental Eye Research | 2014
Najam A. Sharif; Linya Li; Parvaneh Katoli; Shouxi Xu; James Veltman; Byron Li; Daniel Scott; Martin Wax; Juana Gallar; Carmen Acosta; Carlos Belmonte
We sought to characterize the ocular pharmacology, tolerability and intraocular pressure (IOP)-lowering efficacy of FR-190997, a non-peptidic bradykinin (BK) B2-receptor agonist. FR-190997 possessed a relatively high receptor binding affinity (Ki = 27 nM) and a high in vitro potency (EC50 = 18.3 ± 4.4 nM) for inositol-1-phosphate generation via human cloned B2-receptors expressed in host cells with mimimal activity at B1-receptors. It also mobilized intracellular Ca2+ in isolated human trabecular meshwork (h-TM), ciliary muscle (h-CM), and in immortalized non-pigmented ciliary epithelial (h-iNPE) cells (EC50s = 167-384 nM; Emax = 32-86% of BK-induced response). HOE-140, a selective B2-receptor antagonist, potently blocked the latter effects of FR-190997 (e.g., IC50 = 7.3 ± 0.6 nM in h-CM cells). FR-190997 also stimulated the release of prostaglandins (PGs) from h-TM and h-CM cells (EC50s = 60-84 nM; Emax = 29-44% relative to max. BK-induced effects). FR-190997 (0.3-300 μg t.o.) did not activate cat corneal polymodal nociceptors and did not cause ocular discomfort in Dutch-Belted rabbits, but it was not well tolerated in New Zealand albino rabbits and Hartley guinea pigs. A single topical ocular (t.o.) dose of 1% FR-190997 in Dutch-Belted rabbits and mixed breed cats did not lower IOP. However, FR-190997 efficaciously lowered IOP of conscious ocular hypertensive cynomolgus monkey eyes (e.g., 34.5 ± 7.5% decrease; 6 h post-dose of 30 μg t.o.; n = 8). Thus, FR-190997 is an unexampled efficacious ocular hypotensive B2-receptor non-peptide BK agonist that activates multiple signaling pathways to cause IOP reduction.
Investigative Ophthalmology & Visual Science | 2018
Ganesh Prasanna; Luciana Ferrara; Christopher Michael Adams; Takeru Ehara; Byron Li; Louis Yang; Chuanxi Xiang; Christopher Thow Hing Ng; Sean Kim; Christopher Towler; Todd Topley; Cale McAllister; Malay Ghosh; Ronald Newton; Rebecca C. Stacy; Dennis S Rice; Muneto Mogi
Purpose The nitric oxide/soluble guanylate cyclase/protein kinase G (NO/sGC/PKG) is known to be involved in the regulation of intraocular pressure (IOP) and may be dysregulated in glaucoma. The purpose is to demonstrate that the sGC activator MGV354 lowers IOP in a monkey model of glaucoma and could be considered as a possible new clinical drug candidate. Methods Changes to cGMP were assessed in primary human trabecular meshwork (hNTM) cells and binding studies were conducted using human sGC full-length protein. Ocular safety tolerability, exposure, and efficacy studies were conducted in rabbit and monkey models following topical ocular dosing of MGV354. Results sGC was highly expressed in the human and cynomolgus monkey outflow pathways. MGV354 had a 7-fold greater Bmax to oxidized sGC compared to that of reduced sGC and generated an 8- to 10-fold greater cGMP compared to that of a reduced condition in hTM cells. A single topical ocular dose with MGV354 caused a significant dose-dependent reduction of 20% to 40% (versus vehicle), lasting up to 6 hours in pigmented rabbits and 24 hours postdose in a cynomolgus monkey model of glaucoma. The MGV354-induced IOP lowering was sustained up to 7 days following once-daily dosing in a monkey model of glaucoma and was greater in magnitude compared to Travatan (travoprost)-induced IOP reduction. Mild to moderate ocular hyperemia was the main adverse effect noted. Conclusions MGV354 represents a novel class of sGC activators that can lower IOP in preclinical models of glaucoma. The potential for sGC activators to be used as effective IOP-lowering drugs in glaucoma patients could be further determined in clinical studies.
Journal of Medicinal Chemistry | 2018
Takeru Ehara; Christopher Michael Adams; Doug Bevan; Nan Ji; Erik Meredith; David Belanger; James J. Powers; Mitsunori Kato; Catherine Solovay; Donglei Liu; Michael Paul Capparelli; Philippe Bolduc; Jonathan E. Grob; Matthew H. Daniels; Luciana Ferrara; Louis Yang; Byron Li; Christopher Towler; Rebecca C. Stacy; Ganesh Prasanna; Muneto Mogi
Soluble guanylate cyclase (sGC), the endogenous receptor for nitric oxide (NO), has been implicated in several diseases associated with oxidative stress. In a pathological oxidative environment, the heme group of sGC can be oxidized becoming unresponsive to NO leading to a loss in the ability to catalyze the production of cGMP. Recently a dysfunctional sGC/NO/cGMP pathway has been implicated in contributing to elevated intraocular pressure associated with glaucoma. Herein we describe the discovery of molecules specifically designed for topical ocular administration, which can activate oxidized sGC restoring the ability to catalyze the production of cGMP. These efforts culminated in the identification of compound (+)-23, which robustly lowers intraocular pressure in a cynomolgus model of elevated intraocular pressure over 24 h after a single topical ocular drop and has been selected for clinical evaluation.
Investigative Ophthalmology & Visual Science | 2016
Byron Li; Shenouda Yacoub; Rad Daly; Sarah Webb; Travis Jernigan; Terri Krause; Ganesh Prasanna; Dennis S Rice
Investigative Ophthalmology & Visual Science | 2016
Shenouda Yacoub; Byron Li; Muneto Mogi; Dennis S Rice; Ganesh Prasanna
Investigative Ophthalmology & Visual Science | 2014
Byron Li; Shenouda Yacoub; Rad Daly; Sarah Webb; Brian Thomas; Quinn Sessums; Glen Jernigan; Terri Krause; Ganesh Prasanna; Dennis S Rice
Investigative Ophthalmology & Visual Science | 2013
Ganesh Prasanna; Naj Sharif; Byron Li; Mark Hellberg; Terri Krause; Shenouda Yacoub; Daniel Scott; Curtis R. Kelly; Iok-Hou Pang; Keith D. Combrink