Plant-derived Durvalumab variants show efficient PD-1/PD-L1 blockade and therapeutically favourable FcR binding

Immune checkpoint blocking therapy targeting the PD-1/PD-L1 inhibitory signalling pathway has produced encouraging results in the treatment of a variety of cancers. Durvalumab (Imfinzi (R)) targeting PD-L1 is currently used for immunotherapy of several tumour malignancies. The Fc region of this IgG1 antibody has been engineered to reduce Fc gamma R interactions with the aim of enhancing blockade of PD-1/PD-L1 interactions without the depletion of PD-L1-expressing immune cells. Here, we used Nicotiana benthamiana to produce four variants of Durvalumab (DL): wild-type IgG1 and its 'Fc-effector-silent' variant (LALAPG) carrying further modifications to increase antibody half-life (YTE); IgG4(S228P) and its variant (PVA) with Fc mutations to decrease binding to Fc gamma RI. In addition, DL variants were produced with two distinct glycosylation profiles: afucosylated and decorated with alpha 1,6-core fucose. Plant-derived DL variants were compared to the therapeutic antibody regarding their ability to (i) bind to PD-L1, (ii) block PD-1/PD-L1 inhibitory signalling and (iii) engage with the neonatal Fc receptor (FcRn) and various Fc gamma receptors. It was found that plant-derived DL variants bind to recombinant PD-L1 and to PD-L1 expressed in gastrointestinal cancer cells and are able to effectively block its interaction with PD-1 on T cells, thereby enhancing their activation. Furthermore, we show a positive impact of Fc amino acid mutations and core fucosylation on DL's therapeutic potential. Compared to Imfinzi (R), DL-IgG1 (LALAPG) and DL-IgG4 (PVA)(S228P) show lower affinity to CD32B inhibitory receptor which can be therapeutically favourable. Importantly, DL-IgG1 (LALAPG) also shows enhanced binding to FcRn, a key determinant of serum half-life of IgGs.

Automated summary

Immune checkpoint blocking therapy targeting the PD-1/PD-L1 inhibitory signalling pathway has shown promising results in cancer treatment. This study produced different variants of Durvalumab using Nicotiana benthamiana and found that they exhibited similar functions to the therapeutic antibody, including binding to PD-L1, blocking PD-1/PD-L1 signaling, and interacting with FcRn and Fc gamma receptors.