• TFR1, a membrane protein expressed across various cell and tissue types in the human body, plays a crucial role in facilitating iron transport and metabolism. TFR1 is markedly expressed in numerous types of cancer cells. Studies have demonstrated that targeting TFR1 can effectively suppress tumor growth and metastasis. Moreover, TFR1 is also implicated in other conditions such as anemia and neurodegenerative disorders, etc.
• The genome of mouse Tfr1 gene that encode the extracellular domain were replaced by human TfR1 counterparts in B-hTFR1 mice.
• Human TFR1 protein and RNA were detectable in B-hTFR1 mice. Humanization of TFR1 does not change the overall frequency or distribution of immune cell types in spleen, blood and lymph nodes. Humanization TFR1 does not alter various blood biochemical and hematological parameters.
• This product is used to evaluate the pharmacodynamics and safety of treatments for tumors and neurodegenerative diseases, as well as to assess the potential of drugs to penetrate the blood-brain barrier.

Targeting strategy of B-hTFR1 mice. The exons 4-19 of mouse Tfr1 gene that encode the extracellular domain were replaced by human TFR1 exons 4-19 in B-hTFR1 mice.

Human TFR1 mRNA and protein were only detected in homozygous B-hTFR1 mice (H/H), but not in wild-type C57BL/6 mice (+/+).

Human TFR1 was exclusively detectable in blood of homozygous B-hTFR1 mice, but not in wild-type C57BL/6 mice, and its expression level is independent of gender.

Human TFR1 was exclusively detectable in blood of homozygous B-hTFR1 mice, but not in wild-type C57BL/6 mice, and its expression level is independent of gender.

Human TFR1 was detectable on brain microvascular endothelium of homozygous B-hTFR1 mice, but not in wild-type C57BL/6 mice.

Humanization of TFR1 does not change the overall frequency or distribution of immune cell types in spleen, blood and lymph nodes. Values are expressed as mean ± SD.

Select mice aged 3 to 8 weeks, and randomly sample and weigh 50 males and 50 females from each age group. The minimum and maximum weights of the mice in the table are calculated as the average ± SD. The growth curve follows a normal distribution, with a 68% probability that random errors fall within the ± SD range.

In vivo pharmacokinetic (PK) evaluation of anti-human TFR1 bispecific antibodies (BsAbs). B-hTFR1 mice were injected with control IgG (10 mpk) and anti-human TFR1 BsAbs (10.9 mpk) provided by a client via tail vein. Brain and serum were taken for in vivo PK evaluation. Brain concentrations(A), serum concentrations (B), and brain-to-serum ratio (C) of anti-human TFR1 BsAbs were quantified. As shown in panel, anti-human TFR1 BsAbs exhibited higher serum clearance and enhanced brain exposure after dose. The results confirmed that brain of B-hTFR1 mice enables uptake of an intravenously administered anti-human TFR1 BsAbs and B-hTFR1 mice provide a powerful preclinical model for in vivo evaluation of effective delivery of protein therapeutics to the central nervous system (CNS). Graphs represent mean ± SEM. Note: This experiment was performed by the client using B-hTFR1 mice. All the other materials were provided by the client.Publications[1] Qian ZM, Li H, Sun H, Ho K. Targeted drug delivery via the transferrin receptor-mediated endocytosis pathway. Pharmacol Rev. 2002 Dec;54(4):561-87. doi: 10.1124/pr.54.4.561. PMID: 12429868.

B-hTFR1 mice were intravenously injected with AF680-conjugated control hIgG1 or anti human TFR1 antibodies ab1 and ab2 (provided by a client). After 2 days or 3 days post-injection, the mice were perfused and their brains were collected for analysis. (A) Mouse brain images under imaging system. (B) Fluorescence intensity of mouse brain under imaging system. The results indicate that the uptake of anti-human TFR1 antibody ab2 in the brain of B-hTFR1 mice was higher than that of anti-human TFR1 antibody ab1.

No abnormalities were found in the bone marrow of femurs from wild-type C57BL/6 mice (A) and B-hTFR1 mice (B).