Affimer reagents and therapeutics are a class of non-antibody binding proteins that have been engineered for a wide range of applications where antibodies and aptamers have limitations. They can be used to detect difficult targets, can easily be formatted for a wide range of applications and can be easily and cost effectively manufactured.  
 
Two Affimer scaffolds, based on similar protein conformations, have been developed. The first is of human origin, based on the naturally occurring human protease inhibitor Stefin A, and is ideal for therapeutic applications. The second is based on a consensus sequence of Cystatin A from a number of plant species and is ideal for use in reagents and diagnostics.