In the "valley of death" of drug development, over 80% of preclinical candidate drugs fail in human trials, with "species differences" being a key factor in the inaccurate prediction of efficacy. How can we observe physiological and pharmacological responses in mice during the preclinical stage that are closer to those in humans? Humanized mice are the core technological platform for solving this challenge.
 

The Three Main Types of Humanized Mice
 

Based on the "humanization" strategy and research objectives, humanized mice are mainly divided into three types, suitable for different R&D scenarios:
 

Genetically Humanized Mice:​ Replace specific mouse gene(s) with their human counterpart(s) in situ, making them indispensable for verifying drug-target interactions, especially when the drug (e.g., monoclonal antibody) only recognizes the human target protein.
 

Immune System-Reconstituted Mice:​ Typically, immunodeficient mice (e.g., NSG) are engrafted with human hematopoietic stem cells (HSCs) to rebuild the human immune system. This is crucial for evaluating immunotherapies (e.g., immune checkpoint inhibitors) and infectious disease models.
 

Tumor Xenograft Mice:​ Human tumor cells or tissues are transplanted into immunodeficient mice. This is the standard model for evaluating the anti-tumor efficacy of drugs.
 

These three model types complement each other, addressing key questions such as "Does the drug recognize the human target?", "Can the drug eliminate human tumors?", and "How does the drug modulate the human immune system?", collectively forming a comprehensive preclinical efficacy evaluation system.
 

Among these, "Whether the drug recognizes the human target" is a primary concern. When a developed antibody or small molecule drug can only recognize the human target protein and has no binding activity to the mouse orthologue, efficacy validation must be performed on genetically humanized mouse models.
 

What are Genetically Humanized Mice?
 

Genetic humanization refers to the use of gene editing technology to replace a specific endogenous gene or gene fragment in a mouse model in situ (Knock-in) with its human orthologue, thereby expressing functional human protein in the mouse. This typically accompanies the silencing or loss of function of the endogenous animal gene.
 

Common types of genetic humanization include:
 

Full-Length Replacement Humanization:​ Replacing the entire mouse coding sequence (CDS) with the human CDS.
 

Domain Humanization:​ Replacing only key functional domains (e.g., antibody-binding domains) while retaining mouse signal peptides or intracellular domains to maintain signal transduction.
 

Exon Humanization:​ Replacing one or more exons containing functional segments to model human splicing variants or target specific functional regions.
 

Codon Humanization:​ Fine-tuning single or multiple codons to introduce human-specific amino acids or optimize codon preference for precise functional regulation.
 

Locus Humanization:​ Replacing the complete gene locus, including regulatory regions, introns, and exons, to recapitulate the human expression pattern.
 

Multi-Locus Humanization:​ Simultaneous humanization of multiple genes or signaling pathways for studying complex mechanisms or combination therapies.
 

MingCeler Biotech's EnhancerPlus Analysis Platform
 

During the genetic humanization process, low expression levels of the humanized gene in mice are a common technical bottleneck, potentially rendering the model unsuitable for subsequent experiments.
 

To address this challenge, MingCeler Biotech's proprietary EnhancerPlus​ Analysis Platform provides a systematic solution. Leveraging years of data accumulation, the platform can accurately predict the genomic location of enhancers, enabling evidence-based design of gene editing strategies. Optimized strategies can achieve expression patterns and levels closer to the endogenous gene. Platform-validated strategies can increase the transcription and translation efficiency of the humanized protein by 3-4 orders of magnitude.
 

Case Study:​ In a client's project to humanize gene X, the initial humanization strategy resulted in extremely low expression, failing to meet drug development needs. MingCeler Biotech utilized the EnhancerPlus​ Analysis Platform for strategy analysis, adjusted the editing plan, and developed a second-generation model within 2 months. The expression level of the human protein in this model increased by 3 orders of magnitude, approaching endogenous levels and meeting the client's requirements for drug testing.
 

Using traditional technology, obtaining the first generation of the target homozygous mice takes about 10-12 months, and failure is possible if the line cannot be bred. If the first-generation phenotype is unsatisfactory, existing technologies make iteration difficult, not only because of the long timeframe but also because optimizing the editing strategy design requires extensive knowledge in fields like epigenetics and molecular biology.
 

MingCeler Biotech TurboMice™ for Genetic Humanization
 

To address the pain points of long cycles and difficulty in iteration for genetic humanization, MingCeler Biotech's TurboMice™ technology offers a one-stop solution:
 

Supports Precise Insertion of Large Fragments:​ Enables precise and efficient knock-in of ultra-large human gene fragments (300 kb+), facilitating the construction of multi-target or fully humanized target mice.
 

Optimizes Expression Levels:​ Expression optimization via the proprietary EnhancerPlus​ Analysis Platform ensures human protein expression levels approach endogenous levels, meeting R&D and drug testing needs.
 

Rapid Iteration:​ Leveraging the advantage of obtaining homozygous mice in the F0 generation, protein expression can be rapidly validated at the animal level. If expectations are not met, the strategy can be adjusted at the ES cell stage, and a new generation of optimized models can be obtained in 2-5 months, significantly reducing R&D risks and time costs.
 

MingCeler Biotech​ can customize various genetically humanized mouse models according to client needs. Inquiries are welcome.