What is an Affimer?

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

Large binding surface obtained through two 9 amino acids loops enable Affimer proteins to bind with high-Affinity and exquisite selectivity. In-vitro phage display selection allows for a tailored screening approach to discriminate between closely related  targets. 

Selection and characterisation of new custom Affimer binders typically takes just 10 – 12 weeks using optimised and standardised processes.

Affimer molecules can be easily modified by genetic or chemical means allowing maximum flexibility to suit many  assay formats, including several therapeutics options such as multispecific molecules.

Affimer binders can be expressed cost-effectively in very high yields, in a simple bacterial expression system. This guarantees a consistent, high quality supply.

At 12-14 kDa, Affimer molecules are around 10 times smaller than antibodies - giving several performances advantages, such as allowing better tissue penetration and increased packing density on surfaces.