Allergan, an AbbVie Company (NYSE:ABBV), and clinical-stage biotechnology company Molecular Partners (SIX:MOLN) reported on Thursday that that the US Food and Drug Administration (FDA) has issued a Complete Response Letter to the Biologics License Application (BLA) for Abicipar pegol, a novel, investigational DARPin therapy for patients with neovascular (wet) age-related macular degeneration (nAMD).

In the CRL, the FDA indicates that the rate of intraocular inflammation observed following administration of Abicipar pegol 2mg/0.05 ml results in an unfavorable benefit-risk ratio in the treatment of nAMD.

AbbVie intends to meet with the FDA to discuss its comments and determine next steps.

DARPin molecules are derived from naturally occurring binding proteins that consist of repeat sequences with capping structures at each end of the protein. They have three key properties that have made them an important investigational class of binding protein for researchers: high binding affinity, low molecular weight and customizable applications.