Gene targeting strategy for B-NDG HLA-2.1 mice. The B2m gene (Exon1 to Exon3) of mouse was replaced by the sequence encompassing the human B2M CDS and HLA-A2.1 gene in B-NDG HLA-2.1 mice. The mouse B2m gene was knocked out while a fused gene composed of mouse B2m and Fcgrt gene was inserted after the signal peptide sequence of mouse Fcgrt gene in B-NDG B2m KO mice plus. The B-NDG HLA-2.1 mice were mated with B-NDG B2m KO mice plus to obtain a new mouse strain named B-NDG hB2M/HLA-A2.1 mice plus.

Pharmacokinetic characteristic of B-NDG hB2M/HLA-A2.1 mice plus has no difference compared with B-NDG mice. B-NDG mice, B-NDG HLA-A2.1 mice, B-NDG hB2M/HLA-A2.1 mice plus were treated with YH001 (anti-human CTLA4 antibody) (n=4). Blood samples were collected at different time point for the PK assay. The results showed that the PK results of B-NDG hB2M/HLA-A2.1 mice plus group was similar to that in B-NDG mice, and the drug concentration of B-NDG HLA-A2.1 mice group could not be measured at the time point 4 days later. Results indicated that when compared with B-NDG HLA-A2.1 mice, the B-NDG hB2M/HLA-A2.1 mice plus can significantly extend the half-life of antibody drugs in mice.