Designed Ankyrin Repeat Proteins: A Look at their Evolving Use in Medicine with a Focus on the Treatment of Chorioretinal Vascular Disorders

Abstract

Background: Antibodies constitute an important drug development platform for drugs to treat several ophthalmic, oncologic, and immunologic conditions, but due to limitations inherent in antibody production and structure, a wide range of other protein binding scaffolds are being investigated. Designed ankyrin repeat proteins (DARPins) are simple to produce and offer a range of advantages over antibodies because of their stability, high binding affinity, and rigid structure.

Objective: DARPins are being developed for a wide variety of medical applications, and the most studied molecule, abicipar pegol, is used to treat chorioretinal vascular diseases. This mini-review will discuss the current state of DARPin technology and will summarize drug development with a focus on abicipar.

Methods: PubMed searches with keywords "DARPin" and "designed ankyrin repeat proteins" were performed and the reference lists of identified articles were examined for additional research material. Studies using DARPin molecules were identified at Clinicaltrials. gov. Non-peer reviewed data were found through Google searches of pertinent websites.

Results: Abicipar prevents angiogenesis by binding all isoforms of vascular endothelial growth factor (VEGF)-A with single-digit picomolar affinity. Abicipar has a long intraocular half-life in rabbits and has produced promising results in pre-clinical studies. Pivotal phase III registration trials for the treatment of neovascular age-related macular degeneration are ongoing and a phase II/III trial for the treatment of diabetic macular edema has been announced.

Conclusion: Abicipar pegol has the potential to effectively treat chorioretinal vascular conditions with an extended duration of action beyond those of currently used anti-VEGF drugs.

Keywords: Abicipar pegol; anti-VEGF therapy; antibody alternative scaffold; chorioretinal vascular diseases; designed ankyrin repeat proteins (DARPins); extended dosing period.