Utility of a human FcRn transgenic mouse model in drug discovery for early assessment and prediction of human pharmacokinetics of monoclonal antibodies

Therapeutic antibodies continue to develop as an emerging drug class, with a need for preclinical tools to better predict in vivo characteristics. Transgenic mice expressing human neonatal Fc receptor (hFcRn) have potential as a preclinical pharmacokinetic (PK) model to project human PK of monoclonal antibodies (mAbs). Using a panel of 27 mAbs with a broad PK range, we sought to characterize and establish utility of this preclinical animal model and provide guidance for its application in drug development of mAbs. This set of mAbs was administered to both hemizygous and homozygous hFcRn transgenic mice (Tg32) at a single intravenous dose, and PK parameters were derived. Higher hFcRn protein tissue expression was confirmed by liquid chromatography-high resolution tandem mass spectrometry in Tg32 homozygous versus hemizygous mice. Clearance (CL) was calculated using non-compartmental analysis and correlations were assessed to historical data in wild-type mouse, non-human primate (NHP), and human. Results show that mAb CL in hFcRn Tg32 homozygous mouse correlate with human (r² = 0.83, r = 0.91, p < 0.01) better than NHP (r² = 0.67, r = 0.82, p < 0.01) for this dataset. Applying simple allometric scaling using an empirically derived best-fit exponent of 0.93 enabled the prediction of human CL from the Tg32 homozygous mouse within 2-fold error for 100% of mAbs tested. Implementing the Tg32 homozygous mouse model in discovery and preclinical drug development to predict human CL may result in an overall decreased usage of monkeys for PK studies, enhancement of the early selection of lead molecules, and ultimately a decrease in the time for a drug candidate to reach the clinic.     

Tissue expression profile of human neonatal Fc receptor (FcRn) in Tg32 transgenic mice

The neonatal Fc receptor (FcRn) is a homeostatic receptor responsible for prolonging immunoglobulin G (IgG) half-life by protecting it from lysosomal degradation and recycling it to systemic circulation. Tissue-specific FcRn expression is a critical parameter in physiologically-based pharmacokinetic (PBPK) modeling for translational pharmacokinetics of Fc-containing biotherapeutics. Using online peptide immuno-affinity chromatography coupled with high resolution mass spectrometry, we established a quantitative FcRn tissue protein expression profile in human FcRn (hFcRn) transgenic mice, Tg32 homozygous and hemizygous strains. The concentration of hFcRn across 14 tissues ranged from 3.5 to 111.2 pmole per gram of tissue. Our hFcRn quantification data from Tg32 mice will enable a more refined PBPK model to improve the accuracy of human PK predictions for Fc-containing biotherapeutics.     

Deletion polymorphisms in the promoter region of Fcgamma receptor IIB is not associated with antigen-specific IgG2a and IgG2b antibody responses in NC/Nga mice

Fcgamma receptor (R) IIB, a low-affinity FcR for IgG, inhibits B cell Ag R (BCR)-mediated activation when these two receptors are cross-linked by Ag and IgG-containing immune complexs (ICs). We found deletion polymorphisms in the promoter region of fcgr2b in NC/Nga mice, a model for human atopic dermatitis. NC/Nga mice produced significantly higher levels of ovalbumin (OVA)-specific IgG, IgG2a and IgG2b than did BALB/c mice. Analysis of (BALB/c x NC/Nga)F1 x BALB/c or (BALB/c x NC/Nga) F1 x NC/Nga backcross mice revealed that deletion polymorphisms of fcgr2b in NC/Nga mice does not directly regulate hyper OVA-specific IgG2a and IgG2b Ab responses.     

Investigation into the cancer protective effect of flaxseed in Tg.NK (MMTV/c-neu) mice, a murine mammary tumor model

The aim of the present study was to investigate whether low flaxseed doses relevant to human dietary exposure can prevent mammary tumors in transgenic Tg.NK mice, a model of breast cancer. Animals were exposed to flaxseed through the diet at human relevant levels. Tumor-related parameters and tumor development were evaluated. Hepatic cytochrome P450 and glutathione S-transferase activities were significantly reduced in animals receiving low flaxseed doses. An incidence of palpable tumors before sacrifice, a number of tumors per mouse, and a number of large tumors (>6 mm diameter) at necropsy were statistically significantly lower in the high flaxseed group compared to controls, suggesting a beneficial effect on tumor progression of small dietary doses of flaxseed. However, the number of tumor-bearing mice and multiplicity of tumors at necropsy were not statistically significantly lower compared to the controls. Thus, the effect of small dietary doses of flaxseed on mammary tumor development in Tg.NK mice remains to be established.

Electronic supplementary material

The online version of this article (doi:10.1007/s12263-011-0214-1) contains supplementary material, which is available to authorized users.