Gene targeting strategy for B-hALB plus/hFcRn mice.The coding sequence of the full-length human ALB protein was inserted to replaced part of murine exon 1 in B-hALB plus/hFcRn mice.The human full-length FCGRT cDNA sequence was inserted in the Fcgrt exon2 of B-hALB plus/hFcRn mice.

Strain specific albumin expression analysis in homozygous B-hALB plus/hFcRn mice by ELISA. Serum was collected from wild-type C57BL/6JNifdc mice (+/+) and homozygous B-hALB plus/hFcRn mice (H/H), and analyzed by ELISA with species-specific albumin ELISA kit (Mouse Albumin ELISA Kit, abcam, ab207620; Human Albumin ELISA Kit, abcam, ab179887). Mouse ALB was detectable in wild-type mice. Human ALB was exclusively detectable in homozygous B-hALB plus/hFcRn mice but not in wild-type mice.

Pharmacokinetic characteristic of wild-type C57BL/6JNifdc mice and homozygous B-hALB plus/hFcRn mice.C57BL/6JNifdc mice and homozygous B-hALB plus/hFcRn mice were injected intravenously with Ozoralizumab analog (in-house) at time 0 (n=12). Blood samples were collected at different time point for the PK assay. The half-life of Ozoralizumab analog (in-house) in B-hALB plus/hFcRn mice is longer than that in wild-type C57BL/6JNifdc mice, indicating that the albumin in B-hALB plus/hFcRn mice plays a role. This antibody can recognize both MSA (mouse serum albumin) and HSA (human serum albumin), leading to the speculation that its affinity for HSA would be higher than for MSA.