Abstract

Objective Complement biomarker analysis in ocular fluid samples from subjects with geographic atrophy (GA) in a Phase I/II clinical trial of subretinal AAV2 complement factor I (CFI; FI) gene therapy, PPY988 (formerly GT005), to understand target pharmacokinetics/pharmacodynamics. Clinical findings were subsequently utilized to investigate the therapeutic dose in an in vitro complement activation assay.

Design, setting and participants Biomarker data were evaluated from 28 subjects in FOCUS, a Phase I/II clinical trial evaluating the safety and efficacy of three ascending doses of PPY988.

Main outcomes and measures Vitreous humor (VH), and aqueous humor (AH) from subjects before surgery and at serial timepoints (week 5 or 12, 36, 96) were evaluated for changes in levels of intact complement factors I, B and H (FI, FB, FH) components C3, C4, and C1q and breakdown products (Ba, C3a, C3b/iC3b, C4b) using validated assays and OLINK® proteomics.

A modified in vitro assay of complement activation modelling VH complement concentrations was used to compare PPY988 potency to the approved intravitreal C3 inhibitor pegcetacoplan (Apellis) and complement Factor H (FH).

Results An average 2-fold increase in VH FI was observed post-treatment at week 36 and week 96. This correlated with a marked post-treatment reduction in VH concentration of the FB breakdown product Ba and Ba:FB ratio, but minimal changes in C3a and C3b/iC3b levels. Variable concordance in complement biomarker levels in VH versus AH suggest AH is not a reliable proxy for VH for complement activation. During the experimental comparison of doses, a 2-fold increase of FI achieved in the vitreous had only a minor effect on the complement amplification loop in vitro, indicating limited impact [IC50: 1229nM]. Pegcetacoplan completely blocks C3a generation at concentrations much lower than the estimated trough level for monthly intravitreal injections [IC50: 2nM]. Supplementation with FH in the assay revealed similar potency to pegcetacoplan [IC50: 6nM].

Conclusions and relevance PPY988 subretinal gene therapy may not have provided sufficient FI protein to meaningfully modulate complement activation to slow GA growth. Reviewing VH biomarkers is important for understanding target expression, pathway engagement, and determining optimal dose, thereby informing future clinical development.

Competing Interest Statement

The authors declare the following competing interests: Drs T Hallam, E Gardenal, A Jones, S Ellis, E Pekle, K Carney, and L Drage and Ms C Wenden, Ms H Beadsmoore and Mr T Haye are employees of Gyroscope Therapeutics Limited, a Novartis company. Drs Poor, McBlane, Kaiser, Lu, Kassem, Cho, Ferraro, Rangaswamy, Obeidat, Saint-Geniez, and Grosskreutz are employees of Novartis. T Hallam is an author on a pending patent for factor I trimolecular complex building/screening of complement changes. Professor Claire L Harris (Consultant: Q32 Bio, Biocryst; Grant funding: Ra Pharmaceuticals). CLH was an employee of Gyroscope Therapeutics, a Novartis Company. Professor David H Steel (Consultant: Alcon, Gyroscope, BVI, DORC, Eyepoint, Complement Therapeutics, Alimera; Grant funding: Bayer, Alcon, Roche, DORC, BVI, Boehringer, Gyroscope Therapeutics Ltd). Professor Robert E MacLaren (Consultant: Biogen, AGTC, and Beacon Therapeutics; Grant funding: Biogen). REM is also a named inventor on the Biogen BIIB112 patent licensed by the University of Oxford.

Clinical Trial

NCT03846193

Funding Statement

This study did not receive any funding

Author Declarations

I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained.

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The details of the IRB/oversight body that provided approval or exemption for the research described are given below:

The following primary sites gave ethical approval for this work: South Central Oxford A Research Ethics committee - UK; Advarra - US; Thomas Jefferson University Insitutional Biosafety Committee (IBC) - US; Wills Eye Hospital Institutional Review Board - US.

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Data Availability

All data produced in the present study are available upon reasonable request to the authors

ABBREVIATIONSAEsAdverse eventsAHAqueous humorAMDAge-related macular degenerationAPAlternative PathwayBLBaselineC3Complement component 3cDNAComplementary deoxyribonucleic acidCR1Complement receptor 1CSComplement systemDAFDecay-accelerating factorEDTAEthylenediaminetetraacetic acidFAFFundus autofluorescenceFBFactor BFDFactor DFDAFood and Drug AdministrationfdrFalse discovery rateFHFactor HFIFactor IGAGeographic atrophyGMPGood Manufacturing ProcessIVTIntravitrealLLOQLower limit of quantificationLODLimit of detectionLPSLipopolysaccharideMBLMannose binding lectinMCPMembrane cofactor proteinNPXNormalized protein expressionPKPharmacokineticsRCARegulators of complement activationRPERetinal pigment epitheliumRVRare variantSDSSubretinal delivery systemTPTotal proteinTVSITransvitreal surgical interventionUKUnited KingdomULOQUpper limit of quantificationUSUnited StatesVHVitreous humor