The ALB gene encodes albumin, mainly produced in the liver, and is the most abundant protein in human plasma, accounting for 60% to 65% of total plasma protein. The proprotein encoded by ALB is processed to produce a functional protein, and the EPI-X4 peptide derived from this protein is an endogenous inhibitor of the CXCR4 chemokine receptor. Albumin plays a role in regulating plasma colloid osmotic pressure, helping to maintain blood circulation and isolating and transporting many metabolites within the body, especially insoluble hydrophobic metabolites ^[1]. Human Serum Albumin (HSA) is an important carrier protein involved in the transport of a variety of endogenous molecules, including hormones, fatty acids, and metabolic products, as well as exogenous drugs. As a natural carrier protein, HSA has multiple ligand binding sites and a plasma half-life of up to 19 days, making it a promising drug carrier. Several HSA-based drug delivery systems have been approved for clinical trials ^[2-3]. In addition, albumin is also the main transporter of zinc, calcium, and magnesium in plasma, binding approximately 80% of all plasma zinc and approximately 45% of circulating calcium and magnesium, with an affinity ranking of zinc > calcium > magnesium ^[4]. Diseases associated with the ALB gene include hyperthyroxinemia, familial serum albumin abnormality, and analbuminemia ^[5].

The Transferrin receptor (TFRC) gene encodes Transferrin Receptor 1 (TFR1), a protein that is expressed at low levels in most normal cells but shows increased expression in highly proliferative cells, such as basal epidermal cells, intestinal epithelium, and certain activated immune cells. Brain capillary endothelial cells, which constitute the blood-brain barrier (BBB), also express this receptor at high levels ^[6]. TFR1 plays a critical role in maintaining iron metabolism and homeostasis by facilitating receptor-mediated endocytosis of iron-bound transferrin (Tf) via Tf cycling, thereby promoting iron uptake ^[7]. Cellular iron deficiency can lead to apoptosis, while cellular transformation requires substantial iron to sustain proliferation, with iron overload contributing to tumor progression. The high expression of TFR1 in many tumors makes it a potential tumor marker, offering a target for therapies to inhibit tumor growth and metastasis ^[6]. Moreover, TFR1 is implicated in anemia and iron metabolism disorders. Studies have shown that elevated TFR1 expression in cardiomyocytes is associated with exacerbated inflammation in myocarditis patients ^[8].

B6-hALB/hTFRC mice are a dual gene humanized model of Alb and Tfrc, obtained by crossing B6-hALB (HSA) mice (Catalog number: C001492) with B6-hTFRC (CDS) mice (Catalog number: C001584). This model can be used for the development of ALB/TFRC-targeted therapeutic drugs, as well as for the research on drug development using human serum albumin (HSA) as a carrier or drug delivery across the blood-brain barrier (BBB), and for in vivo pharmacodynamic and pharmacokinetic studies.