Phage display for targeting PCSK9

Abstract

Since the development of the theoretical use of antibodies as therapeutic agents by Paul Ehrlich [1] and following the key scientific breakthrough for the development of the hybridoma technology [2], monoclonal antibodies (mAbs) have had a profound impact on therapy. DNA recombinant technologies have been utilised to replace the murine sequences with their human counterpart leading to the development of first chimeric, then humanised, and finally fully human therapeutic antibodies. The use of mAbs has expanded exponentially during the last two decades and currently covers several therapeutic areas, such as oncology, autoimmune, cardiovascular, and inflammatory diseases. In this article of EBioMedicine, Shuhua Tan and colleagues describe the development of a new mAb anti PCSK9 (proprotein convertase subtilisin/kexin type 9) by using a phage display human single-chain fragment variable (scFv) library for antibodies selection [3]. This new technology allows the identification of antibodies outside the immune system, avoiding the use of experimental animals. The authors first selected an scFv with high affinity to PCSK9, then performed two rounds of in vitro affinity maturation processes to further improve its affinity to the target. Finally, they constructed the full-length Fc-silenced anti-PCSK9 antibodies by fusing two antiPCSK9 scFv variants (AP2M18 and AP2M21) to a modified human IgG1 Fc fragment. The interest in targeting PCSK9 is derived from the fact that before 2015, low-density lipoprotein cholesterol (LDL-C) concentration could be lowered by reducing cholesterol intake in the diet (< 300 mg/day), and by using oral pharmacological therapies, i.e. statins, ezetimibe, and bempedoic acid. Statins treatment is associated with a 10 12% lower cardiovascular (CV) events per mmol/L reduction in LDL-C during the first year of treatment, followed by a 22 24% during each subsequent year [4]. Combination therapy with the Niemann-Pick C1-Like 1 (NPC1L1) inhibitor, ezetimibe, or the ATPcitrate lyase inhibitor, bempedoic acid, further control LDL-C levels