;.. '
`
`'
`~
`
`Retina.
`v. 30, no. 9 (Oct. 201 0)
`General Collection
`W1 RE2498
`2010-10-15 10:25:28
`
`PATHWAY-BASED THERAPIES FOR AGE-RELATED MACULAR
`DEGENERATION
`Zarbin, Rosenfeld
`"TREAT AND EXTEND" FOR TYPE 3 CHOROIDAL NEOVASCULARIZATION
`Engelbert, Zweifel, Freund
`FREQUENCY OF MACULAR HEMORRHAGES
`Barbazetto, Saroj, Shapiro, Wong, Freund
`INTRAVITREAL ANTI-VEGF HEMORRHAGIC COMPLICATIONS
`Mason, III, Frederick, Neimhin, White, Jr, Feist, Thomley, Albert, Jr
`WET AGE-RELATED MACULAR DEGENRATION: LESION CHANGES WITH
`RANIBIZUMAB
`Sadda, Stoller, Boyer, Btodi, Shapiro, Ianchuley
`RANIBIZUMAB FOR CHOROIDAL NEOVASCULARIZATION SECONDARY TO
`PUNCTATE INNER CHOROIDOPATHY
`Menezo, Cuthbertson, Downes
`BEVACIZUMAB DURING PREGNANCY
`Tarantola, Folk, Boldt, Mahajan
`AQUEOUS HUMOR IN DIABETIC MACULAR EDEMA
`Funk, Schmidinger, Maar, Bolz, Benesch, Zlabinger, Schmidt-Erfurth
`BEVACIZUMAB IN PIGMENT EPITHELIUM DETACHMENT AS A RESULT
`OF CHOROIDAL NEOVASCULARIZATION IN AGE-RELATED MACULAR
`DEGENERATION
`Acft, Hoeh, Ruppenstein, Kretz, Dithmar
`INTRAVITREAL BEVACIZUMAB FOR AGE-RELATED MACULAR
`DEGENERATION
`Tao, Jonas
`BEVACIZUMAB-RELATED INFLAMMATION
`Chong, Anand, Williams, Qureshi, Callanan
`DRUSEN IMAGING
`Spaide, Curcio
`HIGH-RESOLUTION OPTICAL COHERENCE TOMOGRAPHY IN ADULT
`VITELLIFORM MACULAR DYSTROPHY
`Finger, Charbellssa, Kellner, Schmitz-Valckenbetg, Fleckenstein, Scholl, Holz
`CYTOKINE LEVELS IN CENTRAL SEROUS CHORIORETINOPATHY
`Lim, Kim, Shin
`HYPOXIA-INDUCIBLE FACTOR-I a DIABETIC AND NONDIABETIC PATIENTS
`Lim, Spee, Hinton
`EVOLUTION OF AUTOFLUORESCENCE IN MULTIPLE EVANESCENT WHITE
`DOT SYNDROME
`dell'Omo, Mantovani, Wong, Konstantopoulou, Kulwant, Pavesio
`
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`jsocl Evaluation of Ultra Wide Angle "ora-ora" High Re fractive Index Self-Stabilizing
`Contact Lens for Vitreous Surgery . . ... . .. .. . . .. ... . . ................. . . . .. 1551
`Ravi K. Murthy, Vikram S. Bra" K. V Chalam
`
`CORRESPONDENCE . . ..... . . . .. . . ... . .. . . .. ..... . ... . . .... . .... . . . . ...... 1554
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`

`Review
`
`PATHWAY-BASED THERAPIES FOR AGE-
`RELATED MACULAR DEGENERATION
`
`An Integrated Survey of Emerging Treatment
`Alternatives
`
`MARCO A. ZARBIN, MD, PHD,* PHILIP J. ROSENFELD, MD, PHD†
`
`Purpose: To review treatments under development
`for age-related macular
`degeneration (AMD) in the context of current knowledge of AMD pathogenesis.
`Methods: Review of the scientific literature published in English.
`Results: Steps in AMD pathogenesis that appear to be good targets for drug
`development include 1) oxidative damage; 2)
`lipofuscin accumulation; 3) chronic
`inflammation; 4) mutations in the complement pathway; and 5) noncomplement
`mutations that
`influence chronic inflammation and/or oxidative damage (e.g.,
`mitochondria and extracellular matrix structure). Steps in neovascularization that
`can be targeted for drug development and combination therapy include 1) angiogenic
`factor production; 2) factor release; 3) binding of factors to extracellular receptors (and
`activation of intracellular signaling after receptor binding); 4) endothelial cell activation
`(and basement membrane degradation); 5) endothelial cell proliferation; 6) directed
`endothelial cell migration; 7) extracellular matrix remodeling; 8) tube formation; and 9)
`vascular stabilization.
`Conclusion: The era of pathway-based therapy for the early and late stages of AMD
`has begun. At each step in the pathway, a new treatment could be developed, but
`complete inhibition of disease progression will
`likely require a combination of the
`various treatments. Combination therapy will
`likely supplant monotherapy as the
`treatment of choice because the clinical benefits (visual acuity and frequency of
`treatment) will
`likely be superior
`to monotherapy in preventing the late-stage
`complications of AMD.
`RETINA 30:1350–1367, 2010
`
`A large number of treatments for exudative and
`
`nonexudative age-related macular degeneration
`(AMD) are in preclinical development or in early-
`stage clinical trials (Figure 1). In this review, six
`observations relevant to the pathogenesis of AMD will
`be described. Emerging and established AMD treat-
`ments will then be reviewed within the context of these
`pathogenic schemes. This information should be
`especially useful for the rational development of
`combination therapies.
`
`Pathogenesis of Age-Related
`Macular Degeneration
`
`Detailed consideration of the pathogenesis of AMD
`is beyond the scope of this perspective, but it has been
`discussed extensively elsewhere.1,2 Six concepts will
`be considered briefly.
`First, biochemical studies and histological studies of
`AMD have implicated oxidative damage as a possible
`cause of this disease. Eyes with geographic atrophy
`
`1350
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`PATHWAY-BASED THERAPIES FOR AMD  ZARBIN AND ROSENFELD
`
`1351
`
`Disease Study (AREDS) (http://clinicaltrials.gov/ct2/
`show/NCT00000145?term=Age-Related+Eye+Disease+
`Study+%28AREDS%29&rank=3) results is that an-
`tioxidant supplementation reduces the risk of visual
`loss associated with AMD among properly selected
`patients, especially for patients with the CFHTT
`genotype.10
`Second, excessive accumulation of lipofuscin in the
`RPE may play an important role in the pathogenesis
`AMD.11 In RPE cells, the main source of lipofuscin is
`probably the undegradable components of phagocytized
`outer segments.12 In vertebrate photoreceptors,
`light
`causes isomerization of visual pigment chromophore, 11-
`cis-retinylidene,
`to all-trans-retinylidene, followed by
`release of all-trans-retinal from the opsin binding pocket
`(Figure 2).13
`and its reduction to all-trans-retinol
`ABCA4, an adenosine triphosphate–binding cassette
`transporter present in the outer segment of rods and
`transports N-retinylidene-phosphatidylethanol-
`cones,
`amine from the outer segment disks to the photoreceptor
`cytoplasm.14,15 Retinol dehydrogenase 8 (in outer
`segments) and retinal dehydrogenase 12 (in inner seg-
`ments) reduces all-trans-retinal to all-trans-retinol.16,17
`Vitamin A (all-trans-retinol) diffuses to RPE where it
`is esterified by lecithin/retinol acyltransferase (LRAT)
`to all-trans-retinyl esters and is stored in retino-
`somes.18,19 All-trans-retinyl esters are isomerized to
`in a reaction involving RPE-65.20–22
`11-cis-retinol
`Next, 11-cis-retinol is oxidized to 11-cis-retinal,23,24
`which then diffuses across the extracellular space to
`photoreceptors and recombines with rod-and-cone
`opsin proteins to regenerate visual pigments. Within
`the outer segment disks, ethanolamine can combine
`with two retinaldehyde molecules to form N-retiny-
`lidene-N-retinylethanolamine (A2E); A2E is a major
`fluorophore in lipofuscin found in the RPE.25
`Third, AMD is associated with chronic inflammation
`in the region of the RPE, Bruch’s membrane, and
`choroid.26 Several lines of evidence demonstrate this
`fact. Drusen, for example, contain many components of
`the activated complement cascade.27–29 Anatomical
`studies demonstrate the presence of inflammatory cells
`in Bruch membrane.30 Bioactive fragments of C3 (C3a)
`and C5 (C5a) are present in the drusen of AMD eyes and
`induce vascular endothelial growth factor
`(VEGF)
`expression in RPE cells.31 The latter findings may
`explain why confluent soft drusen are a risk factor for
`CNVs in AMD eyes. The presence of proinflammatory
`molecules in drusen constitutes a stimulus for chronic
`inflammation in the RPE–Bruch membrane–chorioca-
`pillaris complex that may result in some features of late
`AMD. One interpretation of the AREDS is that zinc, one
`of the main therapeutic ingredients of this treatment, also
`affects the complement system, which in turn may slow
`
`Fig. 1. Rate of AMD treatment growth. The number of treatments for
`AMD in preclinical testing, early clinical testing, or clinical practice
`has undergone exponential growth during the past 5 years.
`
`(GA) exhibit DNA strand breaks and lipoperoxida-
`tion.3 Antioxidant changes in the retinal pigment
`epithelium (RPE) of AMD eyes indicate that the RPE
`cells are under oxidative stress (e.g., increased levels
`of heme oxygenase-1 and heme oxygenase-2 and Cu-Zn
`superoxide dismutase).4 Advanced glycation end
`products occur in soft drusen, basal laminar and basal
`linear deposits, and the cytoplasm of RPE cells asso-
`ciated with choroidal neovascularization (CNV).5,6
`Carboxymethyl lysine is present in drusen and CNV5,7
`as are carboxyethyl pyrrole protein adducts.5 Addi-
`tionally, Fe2+—which is an essential element for
`enzymes involved in the phototransduction cascade,
`outer segment disk membrane synthesis, and conver-
`sion of all-trans-retinyl ester
`to 11-cis-retinol
`in
`RPE—also catalyzes the conversion of hydrogen per-
`oxide to hydroxyl radicals and is known to accumulate
`in Bruch’s membrane in AMD eyes.8,9 Epidemiologic
`studies indicate that one of the main risk factors for
`AMD is smoking, which is known to cause oxidative
`damage. One interpretation of the Age-Related Eye
`
`From the *Institute of Ophthalmology and Visual Science,
`University of Medicine and Dentistry of New Jersey, New Jersey
`Medical School, Newark, New Jersey; and †Bascom Palmer Eye
`Institute, University of Miami, Miller School of Medicine, Miami,
`Florida.
`M. A. Zarbin received grant support from the Lincy Foundation,
`Foundation Fighting Blindness, National Eye Institute, Advanced
`Cell Technology, Research to Prevent Blindness, Janice Mitchell
`Vassar and Ashby John Mitchell Fellowship, Joseph J. and
`Marguerite DiSepio Retina Research Fund, the New Jersey Lions
`Eye Research Foundation, and the Eye Institute of New Jersey. P. J.
`Rosenfeld received grant support from National Eye Institute,
`Alexion Pharmaceuticals, Othera Pharmaceuticals, Carl Zeiss
`Meditec, Potentia Pharmaceuticals, and CoMentis.
`M. A. Zarbin is a consultant to Novartis, Genentech, Wyeth/
`Pfizer, Lilly, and Bausch and Lomb. P. J. Rosenfeld is serving on
`the study advisory boards of Othera Pharmaceuticals, GlaxoS-
`mithKline, Sanofi-Aventis, Oraya, Potentia Pharmaceuticals, and
`Bristol-Myers Squibb.
`Institute of
`Reprint
`requests: Marco Zarbin, MD, PhD,
`Ophthalmology and Visual Science, New Jersey Medical School,
`Doctors Office Center, Room 6156, 90 Bergen Street, Newark, NJ
`07103; e-mail: zarbin@umdnj.edu
`
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`1352 RETINA, THE JOURNAL OF RETINAL AND VITREOUS DISEASES  2010  VOLUME 30  NUMBER 9
`
`Fig. 2. The visual cycle. Re-
`produced with
`permission
`from http://lpi.oregonstate.edu/
`infocenter/vitamins/vitaminA/
`visualcycle.html. Courtesy of
`Jane Higdon, Linus Pauling
`Institute, Oregon State Uni-
`versity, copyright 2010.
`
`disease progression. Zinc inhibits C3 convertase
`activity,32 and levels of C3a des Arg, which is a cleavage
`product of C3a and reflects complement activation, are
`higher in patients with AMD (including patients with
`early as well as late AMD) versus controls.33 We are not
`aware of published data demonstrating that zinc
`supplements lower C3a des Arg levels in AMD patients.
`Fourth, drusen, GA, and CNV are associated with
`mutations in components of the complement pathway,
`which is part of the innate immune system (Figure 3).
`Protective and risk-enhancing mutations in compo-
`nents of the complement pathways have been reported
`and include the following loci: complement factor H
`(CFH), complement component 2 (C2), factor B
`(CFB), complement component 3 (C3), and factor I
`(CFI).27,35–47
`Fifth, oxidative damage can compromise regulation
`of the complement system by RPE cells. Thurman and
`Holers48 noted that the alternative complement pathway
`is continuously activated in the fluid phase, and tissue
`surfaces require continuous complement inhibition to
`prevent spontaneous autologous cell injury. Sohn et al49
`demonstrated that the complement system is continu-
`ously activated in the eye. Thurman et al50 showed that
`oxidative stress reduces the regulation of complement
`on the surface of ARPE-19 cells (i.e., reduces surface
`expression of the complement inhibitors, decay accel-
`erating factor [CD55] and CD59) and impairs comple-
`ment regulation at the cell surface by factor H. Sublytic
`activation of the complement cascade also causes VEGF
`release from the cells, which compromises RPE barrier
`function. Similarly, oxidative stress can reduce the
`ability of interferon-gamma to increase CFH expression
`in RPE cells.51 In vitro evidence indicates that products
`of the photooxidation of A2E in RPE cells can serve as
`a trigger for the complement system.52 Thus, the relative
`abundance of lipofuscin in the submacular RPE may
`predispose the macula to chronic inflammation and
`
`AMD, particularly in patients who cannot control
`complement activation because of inherited abnormal-
`ities in the complement system. Hollyfield et al53 have
`described an animal model that links oxidative damage
`and complement activation to AMD.
`Sixth, some AMD-risk enhancing mutations not
`directly involving the complement pathway are also
`linked to inflammation or oxidative damage.54–59
`A proposed pathogenesis (Figure 4) of AMD suggests
`the possibility of therapeutic intervention at different
`points in the natural history of
`the disease with
`antioxidants, visual cycle inhibitors, antiinflammatory
`agents, antiangiogenic agents, and neuroprotective agents.
`
`Treatment
`
`Antioxidants
`
`The AREDS did not show a statistically significant
`benefit of the AREDS formulation for either the
`development of new GA or the involvement of the
`fovea in eyes with preexisting atrophy.60 In part, this
`result may be because of the paucity of GA patients in
`the study. AREDS II
`(http://clinicaltrials.gov/ct2/
`show/NCT00345176?term=Age-Related+Eye+Disease+
`Study+%28AREDS%29&rank=1)
`is a randomized,
`multicenter, clinical trial to assess 1) the role of lutein
`(10 mg)/zeaxanthin (2 mg) and omega-3 long-chain
`polyunsaturated fatty acids (docosahexaenoic acid
`[DHA]/eicosapentaenoic acid [EPA]) in prevention of
`development of GA or CNV; and 2) the possible
`deletion of beta-carotene and lowering the daily zinc
`oxide dose to 25 mg. A Phase 3 clinical trial is underway.
`A recently terminated Phase 2 clinical study, known as
`the OMEGA Study (Othera, Pharmaceuticals Inc.,
`Conshohocken, PA) (http://clinicaltrials.gov/ct2/show/
`NCT00485394?term=OMEGA+Study&rank=1),inves-
`tigated an eyedrop with a prodrug, known as OT 551
`
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`PATHWAY-BASED THERAPIES FOR AMD  ZARBIN AND ROSENFELD
`
`1353
`
`3. The
`Fig.
`complement
`pathway. Modified with per-
`mission from Donoso et al.2
`Components of the comple-
`ment system in which mu-
`tations have been associated
`with increased or decreased
`risk of drusen, GA, and CNV
`are circled. The coagulation
`system-activated
`intrinsic
`pathway is not shown.34
`
`(4-cyclopropanoyloxy-1-hydroxy-2,2,6,6-tetramethypi-
`peridine HCL), to treat GA. This prodrug penetrates the
`eye well and is converted to the active drug (TEMPOL-H),
`which has antioxidant, antiinflammatory (down regu-
`lates nuclear factor k-B), and antiangiogenic properties
`in preclinical models. OT 551 failed to slow the
`enlargement rate of GA after 18 months. We do not
`know if the failure to demonstrate a treatment benefit is
`because of inadequate posterior segment drug delivery
`or because of its mechanism of action.
`
`Visual Cycle Modulators
`
`Visual cycle modulators are intended to reduce the
`accumulation of toxic fluorophores (e.g., A2E) and
`lipofuscin in RPE cells. Retinol binding protein (RBP)
`possesses a high-affinity binding site for all-trans-
`retinol. The binding of retinol to RBP, in turn, creates
`a high-affinity binding site for transthyretin (TTR).
`
`Binding of TTR to the RBP–retinol complex creates
`a large molecular complex that resists filtration in the
`kidney and permits a high steady-state concentration of
`retinol in the circulation, which facilitates delivery of
`retinol to extrahepatic target tissues such as the eye.
`Unlike other extrahepatic tissues, the eye demonstrates
`a unique preference for uptake of retinol when it is
`presented in the RBP–TTR complex. N-(4-hydroxy-
`phenyl) retinamide (Fenretinide; Sirion Therapeutics,
`Inc, Tampa, FL) displaces all-trans-retinol from RBP in
`blood. Fenretinide possesses a bulky side chain on its
`terminal end that prevents interaction of the complex
`with TTR. In the absence of TTR binding, the RBP–
`fenretinide complex is eliminated through glomerular
`filtration (excreted in urine) because of its relatively
`small size. Thus, fenretinide treatment causes a dose-
`dependent reversible reduction in circulating RBP and
`retinol. The unique requirement of the eye for retinol
`delivered by RBP renders the eye more susceptible to
`
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`1354 RETINA, THE JOURNAL OF RETINAL AND VITREOUS DISEASES  2010  VOLUME 30  NUMBER 9
`
`Fig. 4. Proposed pathophys-
`iology of AMD and locations
`in the pathway in which
`different
`therapeutic inter-
`ventions might be effective.
`Modified from Zarbin, M,
`Sunness JS. Dry age-related
`macular degeneration and
`age-related macular degener-
`ation pathogenesis. In: Levin
`LA, Albert DM, eds. Ocular
`Disease: Mechanisms
`and
`Management. China: Saunders
`(Elsevier); 2010:527–535.
`
`in women with breast cancer were 1) qualitative
`interaction between age and treatment duration and 2)
`plasma retinol.64 A trend toward mild inhibition of
`retinal photoreceptor function after prolonged duration
`of intervention was observed in the older women.64
`
`Fig. 5. Microscopic analysis of lipofuscin autofluorescence and cy-
`tostructure of the retina. Tissue sections were prepared from the eyes of
`ABCA42/2 albino and pigmented mice that had been treated with either
`DMSO or fenretinide (HPR) (10 mg/kg) for 42 days. Sections from
`albino mice were analyzed by fluorescence microscopy, while sections
`from pigmented mice were used for light microscopy. A. Analysis of
`lipofuscin autofluorescence revealed considerable accumulation within
`the RPE of DMSO-treated mice. B. In contrast, HPR-treated mice
`showed significantly reduced levels of lipofuscin fluorophores. C.
`Tissue sections prepared from an age-matched and strain-matched wild-
`type mouse are shown for comparison. Analysis of RPE and retina
`cytostructure by light microscopy revealed no aberrant morphology
`associated with either DMSO or HPR treatment (not shown). OS, outer
`segment. Reproduced with permission from Radu et al.61
`
`reductions in serum RBP retinol compared with other
`tissues. Consequently, during chronic fenretinide
`administration, levels of retinol within the eye will be
`reduced dramatically while other extrahepatic tissues
`will obtain retinol from alternate sources. Fenretinide
`reduces lipofuscin and A2E accumulation in the RPE of
`ABCA42/2 mice and causes modest delays in dark
`adaptation (Figure 5).61 A Phase 2 clinical trial of this
`oral agent is underway. Patients receive placebo, 100-
`mg, or a 300-mg dose. Interim analyses reported at
`scientific meetings suggest a possible therapeutic effect
`from the drug, but the results are preliminary. Regarding
`possible side effects from fenretinide, we note that
`fenretinide has been used in clinical trials for cancer
`therapy and prevention of malignant neoplasms.62–68 In
`these studies, which involve patients ranging in age from
`approximately 30 years to 60 years, the incidence of
`acquired night blindness ranges from 2% to 20%, with
`a median of approximately 15%.65,67–72 The incidence
`of dry eye ranges from 3% to 53%, with a median of
`approximately 5%.65,67,69,70,72 Typically, only a minority
`(approximately ,5%) of patients had to discontinue
`therapy because of
`these side effects. Reversible
`dark-adaptation changes
`and electroretinogram
`abnormalities were associated with fenretinide chemo-
`therapy (800 mg/day) for basal cell carcinoma73 and for
`breast cancer (200 mg/day),74 which is associated with
`a decline in plasma retinol concentration.75 Among
`breast cancer patients (mean age, 48 years) using 200
`mg/day,
`the changes in night vision were rarely
`symptomatic.76 Predictive factors with a significant
`effect on the electroretinogram at a dose of 200 mg/day
`
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`PATHWAY-BASED THERAPIES FOR AMD  ZARBIN AND ROSENFELD
`
`1355
`
`Aging and obesity are risk factors for diminished night
`vision because of a strong association with lower plasma
`retinol concentrations.75 We emphasize, however, that
`the clinical trial in progress will determine whether
`observed benefits outweigh these potential side effects.
`Another visual cycle modulator is 13-cis-retinoic
`acid (Accutane, Hoffmann-La Roche, Inc., Nutley, NJ),
`which inhibits the conversion of all-trans-retinyl esters
`(in retinosomes) to 11-cis-retinol and the conversion of
`11-cis-retinol to 11-cis-retinal by retinol dehydrogenase
`and also reduces lipofuscin accumulation in ABCA42/2
`mice.77 This oral agent may be associated with a high
`nyctalopia.78 All-trans-retinylamine
`incidence
`of
`(ACU-4429; Acucela, Seattle, WA)
`is an orally
`administered compound that
`inhibits conversion of
`all-trans-retinyl ester to 11-cis-retinol via blockade
`of RPE65 or another protein needed for isomerization
`of all-trans-retinol. ACU-4429 also reduces lipofuscin
`and A2E accumulation in the RPE of ABCA42/2 mice.
`Because this molecule works as an enzyme inhibitor
`(rather than by reducing availability of precursor, thus
`reducing rhodopsin formation via mass action kinetics),
`its effects should last longer than fenretinide, thus
`permitting less frequent dosing. However, there may be
`greater risk of side effects, such as nyctalopia. Retinoids
`and farnesyl-containing isoprenoids (TDT and TDH)
`also block RPE65.
`Although the use of beta-carotene in the AREDS
`formulation and attempts to block the visual cycle as
`a treatment for AMD may seem contradictory, it is not
`clear that these treatment approaches are antagonistic.
`Normally, beta-carotene is metabolized to retinalde-
`hyde. Relatively high-dose beta-carotene supplemen-
`tation (not vitamin A) was used in the AREDS. In low
`doses, beta-carotene can act as an antioxidant.79 High
`doses of beta-carotene can reduce retinoic acid levels,
`possibly via stimulation of cytochrome P450 activity
`because of
`the formation of eccentric cleavage
`products (vs. the central cleavage of beta-carotene,
`which forms 2 retinal molecules).80 In addition, a free
`radical–rich environment also favors the formation of
`eccentric cleavage products, cytochrome P450 stim-
`ulation, and local retinoic acid deficiency. Thus, it is
`possible that in the local environment of the outer
`retina–RPE–Bruch membrane–choroid,
`fenretinide
`and beta-carotene may not have completely antago-
`nistic effects.
`
`Antiinflammatory Agents
`
`Corticosteroids have a number of antiangiogenic
`effects (Table 1). They have been used previously as
`sole treatment and as part of combination treatment for
`CNV.81 Iluvien (Alimera Sciences, Alpharetta, GA) is
`
`Table 1. Some Antiangiogenic Effects of Corticosteroids
`
`Induce capillary basement membrane dissolution (in
`growing capillaries).
`Alter the behavior of inflammatory cells that stimulate
`angiogenesis.
`Inhibit bFGF-stimulated choroidal endothelial cell
`migration and tube formation.
`Inhibit bFGF-induced activation of matrix
`metalloproteinase-2.
`Reduce oxidative stress–induced VEGF messenger RNA
`expression in ARPE-19 cells.
`Alter intercellular adhesion molecule expression of
`nonendothelial cells.
`Reduce blood–retinal barrier breakdown in rabbit eyes.
`Inhibit platelet-derived growth factor–induced VEGF
`expression.
`Reduce numbers of microglia in AMD-associated
`choroidal new vessels.
`
`Modified from Zarbin.81
`
`a nonbioerodible polyimide tube containing 180 mg
`of the corticosteroid fluocinolone acetonide. It is inserted
`via a 25-gauge intravitreal
`injector, which creates
`a self-sealing wound. A Phase 2 study is underway
`involving 40 patients with bilateral GA, and the primary
`outcome is a difference in the enlargement rate of GA in
`treated versus untreated eyes. The study eye is
`randomized to high (0.5 mg/day) or low (0.2 mg/day)
`dose Iluvien. The fellow eye serves as a control.
`A number of agents that modulate different parts of
`the complement system are in Phase 1 and Phase 2
`clinical trials (Figure 6). In general, these agents work
`either by replacing a defective complement component
`(e.g., providing normal factor H to patients with Y402H
`mutations) so that complement activation can be
`modulated properly or by blocking the complement
`pathway (e.g., POT-4, which inhibits C3). Several
`examples will be discussed because they illustrate some
`of the challenges associated with manipulation of this
`pathway.
`lectin, and alternative pathways
`The classical,
`generate bioactive fragments C3a and C5a and the
`membrane attack complex (C5b,6,7,8,9) via C3
`cleavage. As a result, C3 inhibition should be very
`effective at blocking complement activation that arises
`from many different mutations involving the comple-
`ment system (thus, targeting a relatively large popula-
`tion of AMD patients), which should be a therapeutic
`advantage. However, this degree of complement in-
`hibition may create risks such as an increased risk of
`injection-associated endophthalmitis.
`In a murine
`model, it seems that C3 deficiency does not increase
`the risk of Staphylococcus aureus endophthalmitis.82
`Conversely, in a guinea pig model, complement deple-
`tion with cobra venom factor does seem to increase the
`risk of S. aureus, Staphylococcus epidermidis, and
`
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`Mylan v. Regeneron, IPR2021-00881
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`1356 RETINA, THE JOURNAL OF RETINAL AND VITREOUS DISEASES  2010  VOLUME 30  NUMBER 9
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`Fig. 6. Treatment of AMD
`through management
`of
`complement
`abnormalities.
`Depiction
`of
`complement
`pathways (on the right) is
`modified with
`permission
`from Donoso et al.2 Circles
`and the two red arrows in-
`dicate parts of the pathway
`that are targets of current
`therapy (listed on the left).
`
`Pseudomonas aeruginosa endophthalmitis.83,84 POT-4
`(Potentia Pharmaceuticals, Louisville, KY), a cyclic
`peptide of 13 amino acids that
`is a derivative of
`Compstatin, is a C3 inhibitor and is administered by
`intravitreal
`injection. An attractive feature of
`this
`preparation is that gel-like deposits will form in the
`vitreous when POT-4 is injected at high concentrations.
`These deposits last at least 6 months, thus providing
`a sustained-release delivery system. It is not known
`whether the doses administered intravitreally will have
`systemic effects, but a Phase 1 study of POT-4 in AMD
`eyes with CNV was completed successfully without
`any safety concerns (http://clinicaltrials.gov/ct2/show/
`NCT00473928?term=POT-4&rank=1).
`Inhibition of C5 is attractive because terminal
`complement activity is blocked, but proximal comple-
`ment
`functions
`remain intact,
`for example, C3a
`anaphylatoxin production, C3b opsonization, and im-
`mune complex and apoptotic body clearance. ARC1905
`(Ophthotech Corp., Princeton, NJ) is an anti-C5 aptamer
`delivered by intravitreal injection. It is in Phase 1 trials
`for
`nonexudative
`(http://clinicaltrials.gov/ct2/show/
`NCT00950638?term=ARC-1905&rank=1) and exuda-
`tive complications of AMD (http://clinicaltrials.gov/ct2/
`show/NCT00709527?term=ARC-1905&rank=2). Ecu-
`lizumab (SOLIRIS, Alexion Pharmaceuticals, Cheshire,
`CT) is a humanized monoclonal antibody that blocks C5
`and is administered intravenously. Eculizamab is
`already Food and Drug Administration–approved for
`the treatment of paroxysmal nocturnal hemoglobinuria
`and is in Phase 2 trials for treatment of nonexuda-
`tive complications of AMD (http://clinicaltrials.gov/ct2/
`show/NCT00935883?term=eculizumab&rank=2). C5a
`receptor blockade, for example, JPE1375 (Jerini AG,
`Berlin, Germany); PMX025 (Arana Therapeutics,
`
`Sydney, Australia); Neutrazimab (G2 Therapies, Dar-
`linghurst, New South Wales, Australia), might have an
`advantage or a disadvantage over direct C5a inhibition.
`C5a receptor blockade might inhibit some important
`inflammatory pathways31 without preventing membrane
`attack complex formation.
`Replacement of CFH should inhibit inflammation
`in AMD patients with risk-enhancing mutations in
`CFH. It is not clear whether patients with other
`mutations will benefit from this therapy. An attractive
`feature of this approach, which might require genetic
`screening before treatment,
`is that
`there is no
`increased risk of infection because we have innate
`systems that permit CFH to modulate C3 activation
`locally. The recombinant human form of the full-
`length CFH protein in its ‘‘protective’’ form is known
`as rhCFHp (Ophtherion, Inc, New Haven, CT). This
`protein can be administered intravenously or intra-
`vitreally. In preclinical models, intravitreal adenovi-
`ral vector delivery of the CFH gene has been effective
`and offers the promise of a sustained delivery system.
`(Our understanding is that Ophtherion, Inc., is not
`going to continue with its
`rhCFHp program.)
`Replacement of defective CFH is also being de-
`veloped by Taligen (TT30, a recombinant fusion
`protein, Taligen Therapeutics, Cambridge, MA)
`(http://www.taligentherapeutics.com/pipeline/index.
`html). Taligen is also exploring factor B inhibition
`using a humanized antibody fragment (TA106).
`Gene therapy to silence genes by preventing
`messenger RNA expression might be useful
`for
`treatment of AMD because deletion of genes closely
`related to CFH (i.e., CFHR1 and CFHR3) seems to be
`strongly protective against AMD.38 However, short-
`interfering RNA therapies in the eye may be toxic,85
`
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`Mylan v. Regeneron, IPR2021-00881
`Page 9
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`PATHWAY-BASED THERAPIES FOR AMD  ZARBIN AND ROSENFELD
`
`1357
`
`and it seems that the deletion of CFHR1 and CFHR3
`protects against development of AMD at least in part
`because the deletion tags a protective haplotype and
`does not occur in association with the Y402H single-
`nucleotide polymorphism.86
`Sirolimus (rapamycin; Macusight/Santen, Union City,
`CA)
`is a macrolide fungicide that
`targets mTOR
`(mammalian target of rapamycin) and is antiinflamma-
`tory, antiangiogenic, and antifibrotic; mTOR is a protein
`kinase that regulates proliferation, motility, survival, and
`protein synthesis. Rapamycin can be administered
`subconjunctivally and was in Phase 1/2 studies in
`patients with GA (http://clinicaltrials.gov/ct2/show/
`NCT00766649?term=rapamycin&cond=Macular+
`Degeneration&rank=3) as well as in monotherapy
`(http://clinicaltrials.gov/ct2/show/NCT00712491?term=
`rapamycin&cond=Macular+Degeneration&rank=1) and
`combination therapy trials with ranibizumab for exuda-
`tive
`complications
`of AMD (http://clinicaltrials.
`gov/ct2/show/NCT00766337?term=rapamycin&cond=
`Macular+Degeneration&rank=2). Glatiramer acetate
`(Copaxone; TEVA, Petach Tikva,
`Israel)
`induces
`glatiramer acetate–specific suppressor T cells and
`downregulates inflammatory cytokines.
`It can be
`administered subcutaneously and is in Phase 2
`and Phase 3 studies in patients with drusen (http://
`clinicaltrials.gov/ct2/show/NCT00466076?term=copax-
`one&rank=10). A small, randomized, controlled study
`demonstrated efficacy after 12 weeks of subcutaneous
`injections.87 It remains to be shown whether drusen
`disappearance, the end point of this study, represents
`an appropriate surrogate end point for long-term visual
`acuity preservation in AMD eyes. The Complications
`of Age-Related Macular Degeneration Prevention
`(CAPT) trial demonstrated no long-term visual benefit
`to laser photocoagulation-induced drusen resorption.88
`The mechanism of action of
`the two treatment
`modalities, however, is fundamentally different. Laser
`treatment induces inflammation, and glatiramer ace-
`tate is antiinflammatory.
`Amyloid-b oligomers are toxic to cells (soluble
`monomers are not)