What is Hemophilia?

Hemophilia is an X-linked recessive inherited bleeding disorder caused by pathogenic variants in the F8 gene located at Xq28 or the F9 gene at Xq27 of the X chromosome, leading to impaired synthesis and function of coagulation factor VIII (FVIII) or coagulation factor IX (FIX), respectively. Clinically, it manifests as spontaneous or post-traumatic bleeding due to impaired thrombin generation. The global actual prevalence of hemophilia is approximately 17.1 per 100,000 male residents.

Among these, hemophilia A (HA) caused by FVIII deficiency accounts for 80%-85%, while hemophilia B (HB) caused by FIX deficiency accounts for 15%-20%. Based on plasma coagulation factor activity levels (FVIII:C/FIX:C), it can be classified as severe (<1 IU/dL), moderate (1-5 IU/dL), or mild (5-40 IU/dL).

Image Source Insights into the Molecular Genetic of Hemophilia A and Hemophilia B: The Relevance of Genetic Testing in Routine Clinical Practice

 

Pathogenesis

The core pathological mechanism of hemophilia lies in the interruption of the intrinsic pathway of the coagulation cascade during the thrombin burst phase. In normal hemostasis, activated coagulation factor IXa (FIXa) must bind with its cofactor FVIIIa, Ca²⁺, and platelet phospholipid surfaces to form the intrinsic tenase complex. This complex catalyzes the activation of coagulation factor X (FX) to FXa with extremely high efficiency, subsequently driving the assembly of the prothrombinase complex and achieving explosive generation of thrombin, ultimately forming a stable cross-linked fibrin clot.

Image source: Merck Manuals

 

Hemophilia A is primarily caused by F8 gene mutations or deletions leading to coagulation factor VIII deficiency. Coagulation factor VIII is a glycoprotein with a molecular weight of approximately 330 kDa, mainly synthesized by hepatocytes. During coagulation, FVIII serves as a cofactor for FIXa, activating coagulation factor X in the presence of calcium ions and phospholipids to continue the coagulation process. When FVIII activity decreases, thrombin generation is delayed, fibrin formation is impaired, resulting in persistent bleeding.

Hemophilia B is mainly caused by F9 gene mutations leading to coagulation factor IX deficiency. FIX is a vitamin K-dependent serine protease with a molecular weight of approximately 56 kDa, synthesized by the liver. In the coagulation cascade, FIX activates factor X through interactions with Ca²⁺ ions, membrane phospholipids, and FVIII. When FIX is deficient, the intrinsic coagulation pathway is blocked, and activated partial thromboplastin time is significantly prolonged.

Normal coagulation requires factor VIII and IX levels >30% of normal. Hemophilia patients, due to deficiency of these key factors, experience impaired generation of coagulation thromboplastin in the intrinsic pathway and prolonged coagulation time. When factor activity falls below 1%, patients experience spontaneous bleeding, particularly in joints and muscles.
 

Image Source Based on a population PK model to evaluate the relationship between FVIII activity levels and bleeds

 

Gene Therapy

Recombinant adeno-associated virus (rAAV) vector therapy: Utilizes rAAV (such as serotype 5) to deliver functional F8 (using B-domain deleted variants) or F9 genes (using high-activity Padua variants) to hepatocytes, achieving long-term, stable coagulation factor expression. Representative drugs include Etranacogene dezaparvovec (Hemgenix®) for HB and Valoctocogene roxaparvovec (Roctavian™) for HA. Clinical data show they can significantly increase factor levels and reduce annualized bleeding rate (ABR), enabling most patients to discontinue routine prophylactic treatment.

Lipid nanoparticle (LNP) delivery of mRNA: Achieves short-term, high-level expression of FVIII or FIX, suitable for perioperative management or as a bridging strategy for immune modulation.

Mouse Models

F8 KO mice: Knockout of coagulation factor VIII, F8 gene (exon 17), leading to loss of coagulation factor VIII function. These mice exhibit prolonged coagulation time and internal bleeding symptoms, suitable for evaluating therapeutic strategies and technologies for FVIII deficiency.

F9 KO mice: Knockout of coagulation factor IX, F9 gene, leading to loss of coagulation factor IX function. Compared to hemophilia A mice, their symptoms are relatively mild.

F11 KO mice: Knockout of coagulation factor XI, F11, leading to deficiency of coagulation factor XI. Compared to hemophilia A and B, their bleeding symptoms are milder.

R333Q-hFIX mice: Constructed by targeted knock-in of hF9 gene carrying the R333Q missense mutation, expressing antigenic but inactive FIX protein (CRM⁺), used for studying "low immunogenicity" phenotypes with low inhibitor risk.

R29X-hFIX mice: Introduction of R29X nonsense mutation, leading to complete absence of FIX protein (CRM⁻), serving as a key model for evaluating treatment safety in high-risk genotypes.

MingCeler Biotech Supports Gene Therapy

While gene therapy offers hope for rare diseases, its development and validation depend critically on animal model support. MingCeler Biotech has developed multiple rare disease mouse models using its proprietary TurboMice™ technology. The TurboMice™ platform overcomes technical challenges associated with long mouse model generation cycles and low success rates for complex models, enabling editing at virtually any target gene locus and producing complete homozygous gene-edited mouse models directly from embryonic stem cells in as little as 2 months.

MingCeler Biotech can customize various hemophilia mouse models according to client needs, including F8 KO mice, F9 KO mice, F11 KO mice, R333Q-hFIX mice, and R29X-hFIX mice. We welcome inquiries from researchers!
 

References:

[1] Pezeshkpoor B, Oldenburg J, Pavlova A. Insights into the Molecular Genetic of Hemophilia A and Hemophilia B: The Relevance of Genetic Testing in Routine Clinical Practice. Hamostaseologie. 2022 Dec;42(6):390-399. doi: 10.1055/a-1945-9429. Epub 2022 Dec 22. PMID: 36549291; PMCID: PMC9779947.

[2] Merck Manuals

[3] Nathwani AC. Gene therapy for hemophilia. Hematology Am Soc Hematol Educ Program. 2019 Dec 6;2019(1):1-8. doi: 10.1182/hematology.2019000007. PMID: 31808868; PMCID: PMC6913446.

[4] Li J, Yan ZY. Construction and research progress of hemophilia mouse models. Zhongguo Bijiao Yixue Zazhi. 2019;29(6):141-146.

[5] Sabatino DE, Nichols TC, Merricks E, Bellinger DA, Herzog RW, Monahan PE. Animal models of hemophilia. Prog Mol Biol Transl Sci. 2012;105:151-209. doi: 10.1016/B978-0-12-394596-9.00006-8. PMID: 22137432; PMCID: PMC3713797.

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Disclaimer: Some materials are sourced from the internet. Contact us for removal if infringement is found. This article is for informational purposes only and does not constitute treatment recommendations. The views expressed do not represent the official stance of MingCeler Biotech. For treatment guidance, please consult a qualified healthcare professional at a formal medical institution.