[Complement inhibition treatment for geographic atrophy (GA): functional and morphological efficacy and relevant biomarkers in clinical practice]. / Komplementinhibitorentherapie bei geographischer Atrophie (GA): funktionelle und morphologische Wirksamkeit und relevante Biomarker in der klinischen Praxis.

The approval of complement inhibitory therapeutic agents for the treatment of geographic atrophy (GA) has highlighted the need for reliable and reproducible measurement of disease progression and therapeutic efficacy. Due to its availability and imaging characteristics optical coherence tomography (OCT) is the method of choice. Using OCT analysis based on artificial intelligence (AI), the therapeutic efficacy of pegcetacoplan was demonstrated at the levels of both the retinal pigment epithelium (RPE) and photoreceptors (PR). Cloud-based solutions that enable monitoring of GA are already available.

Autophagy in dry AMD: A promising therapeutic strategy for retinal pigment epithelial cell damage.

Dry age-related macular degeneration (AMD) is a prevalent clinical condition that leads to permanent damage to central vision and poses a significant threat to patients' visual health. Although the pathogenesis of dry AMD remains unclear, there is consensus on the role of retinal pigment epithelium (RPE) damage. Oxidative stress and chronic inflammation are major contributors to RPE cell damage, and the NOD-like receptor thermoprotein structural domain-associated protein 3 (NLRP3) inflammasome mediates the inflammatory response leading to apoptosis in RPE cells. Furthermore, lipofuscin accumulation results in oxidative stress, NLRP3 activation, and the development of vitelliform lesions, a hallmark of dry AMD, all of which may contribute to RPE dysfunction. The process of autophagy, involving the encapsulation, recognition, and transport of accumulated proteins and dead cells to the lysosome for degradation, is recognized as a significant pathway for cellular self-protection and homeostasis maintenance. Recently, RPE cell autophagy has been discovered to be closely linked to the development of macular degeneration, positioning autophagy as a cutting-edge research area in the realm of dry AMD. In this review, we present an overview of how lipofuscin, oxidative stress, and the NLRP3 inflammasome damage the RPE through their respective causal mechanisms. We summarized the connection between autophagy, oxidative stress, and NLRP3 inflammatory cytokines. Our findings suggest that targeting autophagy improves RPE function and sustains visual health, offering new perspectives for understanding the pathogenesis and clinical management of dry AMD.

Spectral Analysis of Human Retinal Pigment Epithelium Cells in Healthy and AMD Eyes.

Purpose: Retinal pigment epithelium (RPE) cells show strong autofluorescence (AF). Here, we characterize the AF spectra of individual RPE cells in healthy eyes and those affected by age-related macular degeneration (AMD) and investigate associations between AF spectral response and the number of intracellular AF granules per cell. Methods: RPE-Bruch's membrane flatmounts of 22 human donor eyes, including seven AMD-affected eyes (early AMD, three; geographic atrophy, one; neovascular, three) and 15 unaffected macula (<51 years, eight; >80 years, seven), were imaged at the fovea, perifovea, and near-periphery using confocal AF microscopy (excitation 488 nm), and emission spectra were recorded (500-710 nm). RPE cells were manually segmented with computer assistance and stratified by disease status, and emission spectra were analyzed using cubic spline transforms. Intracellular granules were manually counted and classified. Linear mixed models were used to investigate associations between spectra and the number of intracellular granules. Results: Spectra of 5549 RPE cells were recorded. The spectra of RPE cells in healthy eyes showed similar emission curves that peaked at 580 nm for fovea and perifovea and at 575 and 580 nm for near-periphery. RPE spectral curves in AMD eyes differed significantly, being blue shifted by 10 nm toward shorter wavelengths. No significant association coefficients were found between wavelengths and granule counts. Conclusions: This large series of RPE cell emission spectra at precisely predefined retinal locations showed a hypsochromic spectral shift in AMD. Combining different microscopy techniques, our work has identified cellular RPE spectral AF and subcellular granule properties that will inform future in vivo investigations using single-cell imaging.

The complement system: a novel therapeutic target for age-related macular degeneration.

INTRODUCTION: With the recent FDA approvals of pegcetacoplan (SYFOVRE, Apellis Pharmaceuticals) and avacincaptad pegol (IZERVAY, Astellas Pharmaceuticals), modulation of the complement system has emerged as a promising therapeutic approach for slowing progression of geographic atrophy (GA) in AMD. AREAS COVERED: This article reviews the current understanding of the complement system, its role in AMD, and the various complement-targeting therapies in development for the treatment of GA, including monoclonal antibodies, aptamers, protein analogs, and gene therapies. Approved and investigational agents have largely focused on interfering with the activity of complement components 3 and 5, owing to their central roles in the classical, lectin, and alternative complement pathways. Other investigational therapies have targeted formation of membrane attack complex (a terminal step in the complement cascade which leads to cell lysis), complement factors H and I (which serve regulatory functions in the alternative pathway), complement factors B and D (within the alternative pathway), and complement component 1 (within the classical pathway). Clinical trials investigating these agents are summarized, and the potential benefits and limitations of these therapies are discussed. EXPERT OPINION: Targeting the complement system is a promising therapeutic approach for slowing the progression of GA in AMD, potentially improving visual outcomes. However, increased risk of exudative conversion must be considered, and further research is required to identify clinical criteria and best practices for initiating complement inhibitor therapy for GA.

Danicopan, an Oral Complement Factor D Inhibitor, Exhibits High and Sustained Exposure in Ocular Tissues in Preclinical Studies.

Purpose: Complement alternative pathway (AP) dysregulation has been implicated in geographic atrophy, an advanced form of age-related macular degeneration. Danicopan is an investigational, first-in-class inhibitor of factor D, an essential AP activation enzyme. We assessed danicopan distribution to the posterior segment of the eye after oral dosing. Methods: Tissue distribution of drug-derived radioactivity was evaluated using whole-body autoradiography following oral administration of [14C]-danicopan to pigmented and albino rats. Pharmacokinetics and ocular tissue distribution were studied in pigmented and albino rabbits following single and multiple oral dosing of danicopan. The melanin binding property was characterized in vitro. Results: Radioactivity was distributed widely in rats and became nonquantifiable in most tissues 24 hours postdose except in the pigmented rat uvea (quantifiable 672 hours postdose). Danicopan binding to melanin was established in vitro. After single dosing, the maximum concentration (Cmax) and area under the curve (AUC) in neural retina and plasma were similar in both rabbit types. After multiple dosing, AUC in neural retina was 3.4-fold higher versus plasma in pigmented rabbits. Drug levels in choroid/Bruch's membrane (BrM)/retinal pigment epithelium (RPE) were similar to plasma in albino rabbits but higher in pigmented rabbits: Cmax and AUC were 2.9- and 23.8-fold higher versus plasma after single dosing and 5.8- and 62.7-fold higher after multiple dosing. In pigmented rabbits, ocular tissue exposures slowly declined over time but remained quantifiable 240 hours postdose. Conclusions: The results demonstrate that danicopan crosses the blood-retina barrier and binds melanin reversibly, leading to a higher and more sustained exposure in melanin-containing ocular tissues (choroid/BrM/RPE) and in the neural retina as compared to in plasma after repeated oral dosing in pigmented animals. Translational Relevance: These findings suggest that oral danicopan possesses potential for treating geographic atrophy because AP dysregulation in the posterior segment of the eye is reported to be involved in the disease pathogenesis.

Deuterated docosahexaenoic acid protects against oxidative stress and geographic atrophy-like retinal degeneration in a mouse model with iron overload.

Oxidative stress plays a central role in age-related macular degeneration (AMD). Iron, a potent generator of hydroxyl radicals through the Fenton reaction, has been implicated in AMD. One easily oxidized molecule is docosahexaenoic acid (DHA), the most abundant polyunsaturated fatty acid in photoreceptor membranes. Oxidation of DHA produces toxic oxidation products including carboxyethylpyrrole (CEP) adducts, which are increased in the retinas of AMD patients. In this study, we hypothesized that deuterium substitution on the bis-allylic sites of DHA in photoreceptor membranes could prevent iron-induced retinal degeneration by inhibiting oxidative stress and lipid peroxidation. Mice were fed with either DHA deuterated at the oxidation-prone positions (D-DHA) or control natural DHA and then given an intravitreal injection of iron or control saline. Orally administered D-DHA caused a dose-dependent increase in D-DHA levels in the neural retina and retinal pigment epithelium (RPE) as measured by mass spectrometry. At 1 week after iron injection, D-DHA provided nearly complete protection against iron-induced retinal autofluorescence and retinal degeneration, as determined by in vivo imaging, electroretinography, and histology. Iron injection resulted in carboxyethylpyrrole conjugate immunoreactivity in photoreceptors and RPE in mice fed with natural DHA but not D-DHA. Quantitative PCR results were consistent with iron-induced oxidative stress, inflammation, and retinal cell death in mice fed with natural DHA but not D-DHA. Taken together, our findings suggest that DHA oxidation is central to the pathogenesis of iron-induced retinal degeneration. They also provide preclinical evidence that dosing with D-DHA could be a viable therapeutic strategy for retinal diseases involving oxidative stress.

LIF, a mitogen for choroidal endothelial cells, protects the choriocapillaris: implications for prevention of geographic atrophy.

In the course of our studies aiming to discover vascular bed-specific endothelial cell (EC) mitogens, we identified leukemia inhibitory factor (LIF) as a mitogen for bovine choroidal EC (BCE), although LIF has been mainly characterized as an EC growth inhibitor and an anti-angiogenic molecule. LIF stimulated growth of BCE while it inhibited, as previously reported, bovine aortic EC (BAE) growth. The JAK-STAT3 pathway mediated LIF actions in both BCE and BAE cells, but a caspase-independent proapoptotic signal mediated by cathepsins was triggered in BAE but not in BCE. LIF administration directly promoted activation of STAT3 and increased blood vessel density in mouse eyes. LIF also had protective effects on the choriocapillaris in a model of oxidative retinal injury. Analysis of available single-cell transcriptomic datasets shows strong expression of the specific LIF receptor in mouse and human choroidal EC. Our data suggest that LIF administration may be an innovative approach to prevent atrophy associated with AMD, through protection of the choriocapillaris.

Transplantation of Human Induced Pluripotent Stem Cell-Derived Retinal Pigment Epithelium in a Swine Model of Geographic Atrophy.

BACKGROUND: The aim of this study was to test the feasibility and safety of subretinal transplantation of human induced pluripotent stem cell (hiPSC)-derived retinal pigment epithelium (RPE) cells into the healthy margins and within areas of degenerative retina in a swine model of geographic atrophy (GA). METHODS: Well-delimited selective outer retinal damage was induced by subretinal injection of NaIO3 into one eye in minipigs (n = 10). Thirty days later, a suspension of hiPSC-derived RPE cells expressing green fluorescent protein was injected into the subretinal space, into the healthy margins, and within areas of degenerative retina. In vivo follow-up was performed by multimodal imaging. Post-mortem retinas were analyzed by immunohistochemistry and histology. RESULTS: In vitro differentiated hiPSC-RPE cells showed a typical epithelial morphology, expressed RPE-related genes, and had phagocytic ability. Engrafted hiPSC-RPE cells were detected in 60% of the eyes, forming mature epithelium in healthy retina extending towards the border of the atrophy. Histological analysis revealed RPE interaction with host photoreceptors in the healthy retina. Engrafted cells in the atrophic zone were found in a patchy distribution but failed to form an epithelial-like layer. CONCLUSIONS: These results might support the use of hiPSC-RPE cells to treat atrophic GA by providing a housekeeping function to aid the overwhelmed remnant RPE, which might improve its survival and therefore slow down the progression of GA.

Ocular Therapeutics and Molecular Delivery Strategies for Neovascular Age-Related Macular Degeneration (nAMD).

Age-related macular degeneration (AMD) is the leading cause of vision loss in geriatric population. Intravitreal (IVT) injections are popular clinical option. Biologics and small molecules offer efficacy but relatively shorter half-life after intravitreal injections. To address these challenges, numerous technologies and therapies are under development. Most of these strategies aim to reduce the frequency of injections, thereby increasing patient compliance and reducing patient-associated burden. Unlike IVT frequent injections, molecular therapies such as cell therapy and gene therapy offer restoration ability hence gained a lot of traction. The recent approval of ocular gene therapy for inherited disease offers new hope in this direction. However, until such breakthrough therapies are available to the majority of patients, antibody therapeutics will be on the shelf, continuing to provide therapeutic benefits. The present review aims to highlight the status of pre-clinical and clinical studies of neovascular AMD treatment modalities including Anti-VEGF therapy, upcoming bispecific antibodies, small molecules, port delivery systems, photodynamic therapy, radiation therapy, gene therapy, cell therapy, and combination therapies.

Intraocular iron injection induces oxidative stress followed by elements of geographic atrophy and sympathetic ophthalmia.

Iron has been implicated in the pathogenesis of age-related retinal diseases, including age-related macular degeneration (AMD). Previous work showed that intravitreal (IVT) injection of iron induces acute photoreceptor death, lipid peroxidation, and autofluorescence (AF). Herein, we extend this work, finding surprising chronic features of the model: geographic atrophy and sympathetic ophthalmia. We provide new mechanistic insights derived from focal AF in the photoreceptors, quantification of bisretinoids, and localization of carboxyethyl pyrrole, an oxidized adduct of docosahexaenoic acid associated with AMD. In mice given IVT ferric ammonium citrate (FAC), RPE died in patches that slowly expanded at their borders, like human geographic atrophy. There was green AF in the photoreceptor ellipsoid, a mitochondria-rich region, 4 h after injection, followed later by gold AF in rod outer segments, RPE and subretinal myeloid cells. The green AF signature is consistent with flavin adenine dinucleotide, while measured increases in the bisretinoid all-trans-retinal dimer are consistent with the gold AF. FAC induced formation carboxyethyl pyrrole accumulation first in photoreceptors, then in RPE and myeloid cells. Quantitative PCR on neural retina and RPE indicated antioxidant upregulation and inflammation. Unexpectedly, reminiscent of sympathetic ophthalmia, autofluorescent myeloid cells containing abundant iron infiltrated the saline-injected fellow eyes only if the contralateral eye had received IVT FAC. These findings provide mechanistic insights into the potential toxicity caused by AMD-associated retinal iron accumulation. The mouse model will be useful for testing antioxidants, iron chelators, ferroptosis inhibitors, anti-inflammatory medications, and choroidal neovascularization inhibitors.

EX-vivo whole blood stimulation with A2E does not elicit an inflammatory cytokine response in patients with age-related macular degeneration.

Age-related macular degeneration (AMD) is a highly prevalent degenerative disease and a leading cause of vision loss worldwide. Evidence for an inflammatory component in the development of AMD exists, yet the exact mechanisms remain unclear. Bisretinoid N-retinylidene-N-retinylethanolamine (A2E) in retinal pigmental epithelial (RPE) cells, and in extracellular deposits constitutes a hallmark of AMD, but its role in the pathology of AMD is elusive. Here, we tested the hypothesis that A2E is responsible for the heightened inflammatory activity in AMD. To this end, we measured ex vivo mRNA expression of the cytokines TNF-α, IL-6, and IL-10 in whole blood samples after stimulation with A2E in a clinical sample of 27 patients with neovascular AMD and 24 patients with geographic atrophy secondary to AMD. Patients' spouses (n = 30) were included as non-affected controls. After stimulation with A2E, no statistical differences were found in the median expression level of TNF-α, IL-6, IL-10 between the control group, and the neovascular AMD and the geographic atrophy group. Our findings do not support evidence for the hypothesis, that A2E per se contributes to heightened inflammatory activity in AMD.

Discovery of Bispecific Antagonists of Retinol Binding Protein 4 That Stabilize Transthyretin Tetramers: Scaffolding Hopping, Optimization, and Preclinical Pharmacological Evaluation as a Potential Therapy for Two Common Age-Related Comorbidities.

Accumulation of cytotoxic lipofuscin bisretinoids may contribute to atrophic age-related macular degeneration (AMD) pathogenesis. Retinal bisretinoid synthesis depends on the influx of serum all-trans-retinol (1) delivered via a tertiary retinol binding protein 4 (RBP4)-transthyretin (TTR)-retinol complex. We previously identified selective RBP4 antagonists that dissociate circulating RBP4-TTR-retinol complexes, reduce serum RBP4 levels, and inhibit bisretinoid synthesis in models of enhanced retinal lipofuscinogenesis. However, the release of TTR by selective RBP4 antagonists may be associated with TTR tetramer destabilization and, potentially, TTR amyloid formation. We describe herein the identification of bispecific RBP4 antagonist-TTR tetramer kinetic stabilizers. Standout analogue (±)-44 possesses suitable potency for both targets, significantly lowers mouse plasma RBP4 levels, and prevents TTR aggregation in a gel-based assay. This new class of bispecific compounds may be especially important as a therapy for dry AMD patients who have another common age-related comorbidity, senile systemic amyloidosis, a nongenetic disease associated with wild-type TTR misfolding.

Systemic levels of C-reactive protein in patients with age-related macular degeneration: A systematic review with meta-analyses.

Ageing of the retina is associated with the gradual accumulation of basal deposits and the formation of drusen. However, in some individuals this process is exacerbated and causes development of age-related macular degeneration. Late features of age-related macular degeneration include geographic atrophy of the neuroretina or choroidal neovascularization. Such changes lead to blurred vision, metamorphopsia, and scotoma, and is the leading cause of vision loss in developed countries. Chronic low-grade inflammation has been investigated because of its relationship to ageing and its role in the gap between chronological and biological ageing. Here, we systematically reviewed studies investigating systemic C-reactive protein in patients with age-related macular degeneration. We identified 53 studies with 60,598 participants (10,392 patients and 38,901 controls). Our meta-analyses revealed that early age-related macular degeneration was not associated to systemic C-reactive protein (Cohen's d = 0.03 [-0.04 to 0.10]; OR = 1.06 [0.93-1.20]; P = 0.39) whereas late age-related macular degeneration (Cohen's d = 0.38 [0.24 to 0.51]; OR = 1.99 [1.55-2.52]; P < 0.0001), and neovascular age-related macular degeneration (Cohen's d = 0.40 [0.24 to 0.56]; OR = 2.07 [1.55-2.76]; P < 0.0001) was associated with a small-to-moderate increase in systemic C-reactive protein. Our review provides an overview of this extensively studied field, provide summary estimates that provide insight into when and to what extent systemic C-reactive protein is associated with age-related macular degeneration, and help in distinguishing the potentially reversible disease processes from that of irreversible retinal ageing.

A Clinical Metabolite of Azidothymidine Inhibits Experimental Choroidal Neovascularization and Retinal Pigmented Epithelium Degeneration.

Purpose: Azidothymidine (AZT), a nucleoside reverse transcriptase inhibitor, possesses anti-inflammatory and anti-angiogenic activity independent of its ability to inhibit reverse transcriptase. The aim of this study was to evaluate the efficacy of 5'-glucuronyl azidothymidine (GAZT), an antiretrovirally inert hepatic clinical metabolite of AZT, in mouse models of retinal pigment epithelium (RPE) degeneration and choroidal neovascularization (CNV), hallmark features of dry and wet age-related macular degeneration (AMD), respectively. Methods: RPE degeneration was induced in wild-type (WT) C57BL/6J mice by subretinal injection of Alu RNA. RPE degeneration was assessed by fundus photography and confocal microscopy of zonula occludens-1-stained RPE flat mounts. Choroidal neovascularization was induced by laser injury in WT mice, and CNV volume was measured by confocal microscopy. AZT and GAZT were delivered by intravitreous injections. Inflammasome activation was monitored by western blotting for caspase-1 and by ELISA for IL-1ß in Alu RNA-treated bone marrow-derived macrophages (BMDMs). Results: GAZT inhibited Alu RNA-induced RPE degeneration and laser-induced CNV. GAZT also reduced Alu RNA-induced caspase-1 activation and IL-1ß release in BMDMs. Conclusions: GAZT possesses dual anti-inflammatory and anti-angiogenic properties and could be a viable treatment option for both forms of AMD.

A role for mast cells in geographic atrophy.

Mast cells (MCs) are the initial responders of innate immunity and their degranulation contribute to various etiologies. While the abundance of MCs in the choroid implies their fundamental importance in the eye, little is known about the significance of MCs and their degranulation in choroid. The cause of geographic atrophy (GA), a progressive dry form of age-related macular degeneration is elusive and there is currently no therapy for this blinding disorder. Here we demonstrate in both human GA and a rat model for GA, that MC degranulation and MC-derived tryptase are central to disease progression. Retinal pigment epithelium degeneration followed by retinal and choroidal thinning, characteristic phenotypes of GA, were driven by continuous choroidal MC stimulation and activation in a slow release fashion in the rat. Genetic manipulation of MCs, pharmacological intervention targeting MC degranulation with ketotifen fumarate or inhibition of MC-derived tryptase with APC 366 prevented all of GA-like phenotypes following MC degranulation in the rat model. Our results demonstrate the fundamental role of choroidal MC involvement in GA disease etiology, and will provide new opportunities for understanding GA pathology and identifying novel therapies targeting MCs.

Amelotin is expressed in retinal pigment epithelium and localizes to hydroxyapatite deposits in dry age-related macular degeneration.

Deposition of hydroxyapatite (HAP) basal to the retinal pigment epithelium (RPE) is linked to the progression of age-related macular degeneration (AMD). Serum-deprivation of RPE cells in culture mimics some features of AMD. We now show that serum-deprivation also leads to the induction of amelotin (AMTN), a protein involved in hydroxyapatite mineralization in enamel. HAP is formed in our culture model and is blocked by siRNA inhibition of AMTN expression. In situ hybridization and immunofluorescence imaging of human eye tissue show that AMTN is expressed in RPE of donor eyes with geographic atrophy ("dry" AMD) in regions with soft drusen containing HAP spherules or nodules. AMTN is not found in hard drusen, normal RPE, or donor eyes diagnosed with wet AMD. These findings suggest that AMTN is involved in formation of HAP spherules or nodules in AMD, and as such provides a new therapeutic target for slowing disease progression.

Choriocapillaris Degeneration in Geographic Atrophy.

Early age-related macular degeneration (AMD) is characterized by degeneration of the choriocapillaris, the vascular supply of retinal photoreceptor cells. We assessed vascular loss during disease progression in the choriocapillaris and larger vessels in the deeper choroid. Human donor maculae from controls (n = 99), early AMD (n = 35), or clinically diagnosed with geographic atrophy (GA; n = 9, collected from outside the zone of retinal pigment epithelium degeneration) were evaluated using Ulex europaeus agglutinin-I labeling to discriminate between vessels with intact endothelial cells and ghost vessels. Morphometric analyses of choriocapillaris density (cross-sectional area of capillary lumens divided by length) and of vascular lumen/stroma ratio in the outer choroid were performed. Choriocapillaris loss was observed in early AMD (Bonferroni-corrected P = 0.024) with greater loss in GA (Bonferroni-corrected P < 10-9), even in areas of intact retinal pigment epithelium. In contrast, changes in lumen/stroma ratio in the outer choroid were not found to differ between controls and AMD or GA eyes (P > 0.05), suggesting choriocapillaris changes are more prevalent in AMD than those in the outer choroid. In addition, vascular endothelial growth factor-A levels were negatively correlated with choriocapillaris vascular density. These findings support the concept that choroidal vascular degeneration, predominantly in the microvasculature, contributes to dry AMD progression. Addressing capillary loss in AMD remains an important translational target.

Therapeutic Approaches with Intravitreal Injections in Geographic Atrophy Secondary to Age-Related Macular Degeneration: Current Drugs and Potential Molecules.

The present review focuses on recent clinical trials that analyze the efficacy of intravitreal therapeutic agents for the treatment of dry age-related macular degeneration (AMD), such as neuroprotective drugs, and complement inhibitors, also called immunomodulatory or anti-inflammatory agents. A systematic literature search was performed to identify randomized controlled trials published prior to January 2019. Patients affected by dry AMD treated with intravitreal therapeutic agents were included. Changes in the correct visual acuity and reduction in geographic atrophy progression were evaluated. Several new drugs have shown promising results, including those targeting the complement cascade and neuroprotective agents. The potential action of the two groups of drugs is to block complement cascade upregulation of immunomodulating agents, and to prevent the degeneration and apoptosis of ganglion cells for the neuroprotectors, respectively. Our analysis indicates that finding treatments for dry AMD will require continued collaboration among researchers to identify additional molecular targets and to fully interrogate the utility of pluripotent stem cells for personalized therapy.

Gift of Sight: Stem-Cell Patches for Wet and Dry Macular Degeneration.

Regenerative Patch Technologies LLC was founded by Mark Humayun, MD, PhD, and David R. Hinton, MD, from the University of Southern California; and Dennis O. Clegg, PhD, from the University of California, Santa Barbara. The technology to produce the stem cell-based retinal implant is exclusively licensed to Regenerative Patch Technologies LLC from the University of Southern California, the California Institute of Technology, and the University of California, Santa Barbara. Humayun and Hinton have an equity interest in and are consultants for Regenerative Patch Technologies LLC.

In Vivo Stability Profiles of Anti-factor D Molecules Support Long-Acting Delivery Approaches.

The collection of aqueous humor (phase 1 b/2 Mahalo study) from patients dosed intravitreally with anti-factor D (AFD; FCFD4514S, lampalizumab), a humanized antibody fragment previously under investigation to treat geographic atrophy (GA) secondary to age-related macular degeneration, presented a unique opportunity to examine AFD properties in clinical samples. We investigated AFD stability and target-binding characteristics to set up strategies for engineering and evaluating optimized molecules that enable less frequent dosing. Two variants, AFD.v8 and AFD.v14, were evaluated as alternatives to AFD for longer-acting treatments. Mass spectrometry, surface plasmon resonance, and immunoassay were used to assess AFD stability and binding activity in aqueous humor samples from Mahalo patients. In vitro stability and binding activity of AFD, AFD.v8, and AFD.v14 were assessed in human vitreous humor versus buffer at 37 °C over 16 weeks and in vivo in rabbits over 28 days along with pharmacokinetic determinations. In human aqueous humor, AFD specific binding was >85% through 30 days, and deamidation was <3% through 60 days, consistent with the AFD stability and binding activity in vitreous humor from humans in vitro and rabbits in vivo. Target binding, stability, and rabbit pharmacokinetic parameters of AFD.v8 and AFD.v14 were similar to those of AFD. Physiological stability and activity of AFD translated across in vitro and in vivo studies in humans and rabbits. The two variants AFD.v8 and AFD.v14 demonstrated comparable potency and pharmacokinetics. These findings, along with previously demonstrated improved solubility of AFD.v8 and AFD.v14, provide proof-of-concept for developing other similar long-acting therapeutic variants.