Development and characterization of an anti-HTRA1 antibody for dry AMD treatment

Abstract

Purpose : Dry age-related macular degeneration (AMD) is the most common form of AMD and has no effective treatment due to its complex multifactorial nature. Combination of genetics and biology suggests high-temperature requirement A1 (HTRA1), a secreted homotrimeric serine protease, as one potential factor. We developed an anti-HTRA1 antibody conjugated with a half-life extending biopolymer. The molecule was specifically designed to bind to the active trimeric configuration of HTRA1 with 1:1 stoichiometry. Anti-HTRA1 in combination with other drug components could be a promising therapeutic for dry AMD.

Methods : Anti-HTRA1 antibodies were initially discovered from immunized rodents using single cell microfluidics technology. Selected hits were humanized and affinity matured with phage display. Affinity and potency were determined by SPR and FRET-based cleavage assays. Thermostability was assessed by DLS and DSF. Polyreactivity was evaluated by ELISA with a panel of common antigens and BVP particles. The stoichiometry of the antibody and HTRA1 in the complex was measured by SEC-MALS and mass photometry. The antibodies were conjugated with a phosphorylcholine biopolymer to assess compatibility with the ABC Platform™.

Results : Selected anti-HTRA1 antibodies from immunized rodents presented an advantageous 1:1 stoichiometry with one antibody binding to one trimeric HTRA1. Affinity maturation and engineering of humanized antibodies highly improved binding affinity, thermostability and eliminated sequence liabilities. Optimized molecules bind to trimeric HTRA1 with picomolar affinity and effectively inhibit its enzymatic activity, while showing minimal to no binding to monomeric HTRA1 and homologs, respectively. High thermostability, low polyreactivity and compatibility with ABC Platform™ indicate a favorable developability profile for the generation of long-lasting anti-HTRA1 inhibitor molecules.

Conclusions : We have developed an anti-HTRA1 antibody that preferentially binds to active trimeric HTRA1 with 1:1 stoichiometry. The molecule demonstrates high binding affinity and potency along with good developability. When embedded in Kodiak’s ABC Platform™, this molecule in combination with other therapeutics could be a promising candidate for a next generation dry AMD treatment.

This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.