# Platelet-derived FVIII Gene Therapy of Hemophilia A

> **NIH NIH R01** · MEDICAL COLLEGE OF WISCONSIN · 2022 · $513,937

## Abstract

SUMMARY
The development of inhibitory antibodies (inhibitors) against FVIII is not only a severe and important
complication of protein replacement therapy, but also a major concern in gene therapy of hemophilia A.
Generation of such inhibitors might potentially preclude gene therapy for hemophilia A. In this project, we
propose to investigate a novel gene therapy approach that will provide therapeutic FVIII protein and induce
immune tolerance for hemophilia A and hemophilia A with inhibitors based on the hypothesis that targeting the
production of FVIII to platelets that activate at the site where FVIII is needed could overcome the presence of
inhibitory antibodies. In addition, targeting neo-protein FVIII expression and storage in the α-granules of
platelets that contain immunomosuppresive molecule, transforming growth factor beta-1, and that aged
platelets undergo apoptosis and phagocytosis would generate immunoregulatory milieu, promoting antigen-
specific immunologic tolerance.
We have developed a clinically translatable gene therapy protocol for hemophilia A using lentiviral gene
delivery of the FVIII expression cassette under control of the platelet-specific αIIb promoter (2bF8) to
hematopoietic stem cells resulting in FVIII expression in platelets. Our previous studies using animal models
have demonstrated that platelet targeted FVIII expression results in FVIII storage together with its carrier
protein VWF in platelet α-granules and that platelets-FVIII retains efficacy even in the presence of inhibitors
with no overt thrombotic risk. Our further studies show that 2bF8 lentiviral gene delivery to hematopoietic stem
cells can not only restore hemostasis in hemophilia A mice but also induce immune tolerance through
peripheral clonal deletion of CD4 T cells and induction of antigen-specific regulatory T cells. We found that
VWF is essential for platelet gene therapy of HA with inhibitors. In the current application, we propose to
develop optimal preconditioning regimen for platelet gene therapy for hemophilia A and hemophilia A with
inhibitors. We will elucidate how VWF/FVIII interaction impacts platelet-FVIII delivery and FVIII immune
responses in platelet-specific FVIII gene therapy. We will explore the potential underlying mechanisms by
which the unique peripheral tolerance is processed after 2bF8 gene therapy.
These studies should help us to further understand the biological characteristics of 2bF8 gene therapy, with the
potential to develop a safe curative gene therapy approach that can not only provide therapeutic protein, but
also induce the antigen-specific immune tolerance for the clinical treatment of HA patients and patients with
inhibitors, as well as non-hereditary hemophilic patients with acquired inhibitory antibodies that can also have
life-threatening clinical bleeding.

## Key facts

- **NIH application ID:** 10397019
- **Project number:** 5R01HL102035-13
- **Recipient organization:** MEDICAL COLLEGE OF WISCONSIN
- **Principal Investigator:** Qizhen Shi
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2022
- **Award amount:** $513,937
- **Award type:** 5
- **Project period:** 2010-07-01 → 2024-06-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10397019

## Citation

> US National Institutes of Health, RePORTER application 10397019, Platelet-derived FVIII Gene Therapy of Hemophilia A (5R01HL102035-13). Retrieved via AI Analytics 2026-05-22 from https://api.ai-analytics.org/grant/nih/10397019. Licensed CC0.

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