Target. Modulate. Heal: Small Nucleic Acid Therapeutics and Gene Therapy Powered by Humanized Mouse Models

From rewriting faulty genes to silencing disease at its source, small nucleic acid therapeutics and gene therapy are redefining what’s possible in modern medicine. These powerful technologies enable precise control of gene expression and correction of genetic mutations — targeting previously “undruggable” genes and offering hope for diseases once considered incurable.

Small Nucleic Acid Therapeutics

**Small nucleic acid** drugs are short strands of nucleotides — known as oligonucleotides — designed to interact with specific DNA, RNA or protein targets within cells. Key modalities include:

• Antisense oligonucleotides (ASOs)
• Small interfering RNAs (siRNAs)
• MicroRNAs (miRNAs)
• Aptamers

Small nucleic acid therapeutics target pathological gene expression (Takakura et al. 2019 & Collotta et al. 2023)

Evaluation of Small Nucleic Acid Using Humanized Mouse Models

Small nucleic acid drugs can act on exons, introns, or untranslated regions (UTRs) of mRNA. To support their translation from bench to bedside, Biocytogen has developed proprietary humanized mouse models that exrpress full-length human genes. These models feature:

• Full-locus human gene replacement for accurate targeting by human nucleic acid drugs
• Stable gene expression across the lifespan
• In vivo validation for efficacy and safety
• Compatibility with disease models for pharmacodynamic studies in relevant pathological contexts

Case Study for Cardiovascular Disease: LPA Humanized Mice (B-hLPA Mice)

Lp(a) is a cholesterol-rich particle structurally similar to LDL, distinguished by the presence of apo(a), which is encoded by the LPA gene. Elevated Lp(a) levels are a recognized risk factor for cardiovascular disease. While conventional lipid-lowering therapies have limited effect on Lp(a), emerging siRNA treatments — such as olpasiran — can selectively silence hepatic LPA expression, reducing apo(a) production and significantly lowering plasma Lp(a) levels (Kronenberg et al. 2022).

In vivo efficacy of an olpasiran analog in humanized B-hLPA mice. A single dose of the olpasiran analog reduced plasma apo(a) levels by over 80% in heterozygous B-hLPA mice. These models provide a robust platform for preclinical evaluation of LPA-targeted nucleic acid therapies.

Case Study for Obesity and Type 2 Diabetes: INHBE Humanized Mice (B-hINHBE Mice)

INHBE encodes activin E, a liver-secreted hormone that suppresses lipolysis in adipose tissue, impacting fat distribution and metabolism. Loss-of-function mutations in INHBE are linked to reduced abdominal fat, improved metabolic health, and lower risk of cardiovascular disease and type 2 diabetes (Deaton et al. 2022), highlighting its potential as a cardiometabolic therapeutic target.

Efficacy study of INHBE-siRNA in humanized B-hINHBE mice with high-fat diet (HFD) induced obesity. B-hINHBE mice (7 weeks, male) were fed a high-fat diet for 12 weeks to induce mice obesity. Administration of INHBE-targeting siRNA resulted in significant reductions in body weight, as well as liver triglyceride and cholesterol levels. STD (Standard Chow Diet); TA (Test Article); TG (Triglyceride); TC (Total Cholesterol).

INHBE-siRNA treatment reverses obesity phenotypes in HFD-induced humanized B-hINHBE mice. Efficacy of INHBE-targeting siRNA was evaluated in B-hINHBE humanized mice subjected to a high-fat diet (HFD). After 13 treatments, lean and adipose tissue distribution was assessed using micro-CT.

Case Study for Neurological Disease: TFR1/DMPK Humanized Mice (B-hTFR1/hDMPK Mice)

Myotonic dystrophy type 1 (DM1) is a progressive neuromuscular disorder caused by toxic RNA from CTG repeat expansion in the DMPK gene. Antibody–oligonucleotide conjugates (AOCs) deliver siRNAs to affected tissues, with transferrin receptor 1 (TfR1) serving as an effective target for muscle-specific delivery due to its high expression in skeletal muscle (Pascual-Gilabert et al. 2021).

The inhibitory efficiency of the AOC drug against human DMPK in heterozygous B-hTFR1/hDMPK mice. The human DMPK mRNA in the treatment groups (AOC) were significantly reduced compared to the control groups (naked antibody and PBS) in tibialis anterior muscle, demonstrating that B-hTFR1/hDMPK mice provide a powerful preclinical model for in vivo evaluation of human DMPK targeted AOC drug.

Gene Therapy

**Gene therapy involves the direct modification of a patient’s genes to treat or prevent diseases. Techniques include replacing faulty genes, inactivating malfunctioning ones, or introducing new genes to combat disease. Biocytogen **has developed a suite of gene-edited mouse models that replicate the genetic alterations found in various disorders, facilitating the evaluation and acceleration of gene therapies for conditions like:

• Duchenne Muscular Dystrophy (DMD)
• Inherited Retinal Diseases (RHO mutation)
• Hemophilia

Case Study for Duchenne Muscular Dystrophy (DMD) Gene Therapy: Humanized DMD Mice (B-hDMD (exon44–46, del45) Mice)

Duchenne muscular dystrophy (DMD) is a severe, progressive genetic disorder caused by mutations in the DMD gene, which eliminate the production of dystrophin, a protein vital for muscle fiber stability. Without dystrophin, muscles are highly susceptible to damage, leading to gradual muscle weakness, loss of mobility, and impaired respiratory and cardiac function. Despite improved care, DMD remains a life-limiting condition with premature mortality (D’Ambrosio et al. 2023) ​​​​.

Current and investigational therapies for DMD (D’Ambrosio et al. 2023) & models available at Biocytogen

Muscle damage and histopathology in humanized B-hDMD (Exon44–46, del45) mice. A. Creatine kinase activity was significantly greater in homozygous B-hDMD (exon44–46, del45) mice compared to that in wild-type mice. B. H&E-stained muscle from B-hDMD (exon44–46, del45) mice shows dystrophic features of inflammation (red arrow) and centrally-located nuclei (black arrow), unlike normal wild-type controls.

Explore Biocytogen’s Humanized Mouse Models for Small Nucleic Acid Therapeutics & Gene Therapy!

*Contact us today to discover how our humanized mouse models can accelerate your development of innovative therapies!*

References

Takakura, Kazuki, et al. “The clinical potential of oligonucleotide therapeutics against pancreatic cancer.” International journal of molecular sciences 20.13 (2019): 3331.

Collotta, D., et al. “Antisense oligonucleotides: A novel Frontier in pharmacological strategy.” Frontiers in Pharmacology 14 (2023): 1304342.

Kronenberg, Florian, et al. “Lipoprotein (a) in atherosclerotic cardiovascular disease and aortic stenosis: a European Atherosclerosis Society consensus statement.” European heart journal 43.39 (2022): 3925–3946.

Deaton, Aimee M., et al. “Rare loss of function variants in the hepatokine gene INHBE protect from abdominal obesity.” Nature Communications 13.1 (2022): 4319.

Pascual-Gilabert, Marta, Arturo López-Castel, and Ruben Artero. “Myotonic dystrophy type 1 drug development: A pipeline toward the market.” Drug Discovery Today 26.7 (2021): 1765–1772.

D’Ambrosio, Eleonora S., and Jerry R. Mendell. “Evolving therapeutic options for the treatment of duchenne muscular dystrophy.” Neurotherapeutics 20.6 (2023): 1669–1681.