# Base editing and prime editing for sickle cell disease

> **NIH NIH R01** · ST. JUDE CHILDREN'S RESEARCH HOSPITAL · 2024 · $761,516

## Abstract

PROJECT SUMMARY
Despite advances in the medical care of sickle cell disease (SCD), most patients continue to experience severe
pain, poor quality of life, progressive organ deterioration and premature death. Allogeneic hematopoietic stem
cell transplantation (HSCT) can cure SCD but is associated with numerous toxicities and only 20% of patients
have Human Leukocyte Antigen (HLA)-matched donors. Therefore, improved and more widely accessible
curative therapies are needed. Genetic modification of autologous HSCs is a promising experimental approach
for treating SCD that circumvents some of the problems associated with allogeneic HSCT, although the optimal
technical strategies are not yet established. This proposal explores the use of adenosine base editors (ABEs)
and prime editors (PEs) for genetic correction of SCD. In contrast to conventional genome editing, these novel
approaches create precise nucleotide alterations independent of double-stranded DNA breaks (DSBs), which
can cause structural DNA abnormalities, cell death or malignant transformation. Adenosine base editors convert
targeted A·T base pairs to G·C pairs. Prime editors copy edited sequence information from a guide RNA template
into a targeted DNA locus. We will test these potentially transformative tools in 3 different strategies for SCD
therapy. Aim 1 employs ABEs to create HSC alterations that recapitulate hereditary persistence of fetal
hemoglobin (HPFH), a benign genetic condition that alleviates the pathophysiology of co-inherited SCD by
inducing the expression of red blood cell (RBC) fetal hemoglobin (HbF), a potent anti-sickling agent. We have
used protein evolution strategies to create new high-efficiency ABEs that generate HPFH mutations at
frequencies of up to 60% in CD34+ hematopoietic stem and progenitor cells (HSPCs), with HbF being induced
to levels that inhibit hypoxic sickling of erythroid progeny. Aim 2 uses ABEs to convert the mutant SCD codon
from valine to alanine, thereby generating “Hemoglobin Makassar (HbG)”, a naturally occurring benign non-
sickling variant. We have developed an altered PAM-specific ABE that converts HbS alleles to HbG in SCD
donor HSPCs at frequencies of up to 80%, with inhibition of RBC sickling. Aim 3 employs prime editing to revert
the mutant SCD codon to normal (Val→Glu), which we have shown to occur efficiently in the HEK293T cell line
and now aim to optimize in HSPCs from affected individuals. Overall, our preliminary studies have shown proof
of principle for three novel, independent editing approaches to treating SCD without the need to enrich for edited
cells or to create DSBs. Through the proposed research, we seek to optimize the efficiency of these approaches
in primary HSPCs and to further determine their safety and efficacy by using mouse models, in vitro culture
methods and biochemical assays. Developing three approaches simultaneously will enable us to compare their
outcomes directly and to determine the best therapeutic stra...

## Key facts

- **NIH application ID:** 10795850
- **Project number:** 5R01HL156647-04
- **Recipient organization:** ST. JUDE CHILDREN'S RESEARCH HOSPITAL
- **Principal Investigator:** DAVID R LIU
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2024
- **Award amount:** $761,516
- **Award type:** 5
- **Project period:** 2021-01-01 → 2025-08-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10795850

## Citation

> US National Institutes of Health, RePORTER application 10795850, Base editing and prime editing for sickle cell disease (5R01HL156647-04). Retrieved via AI Analytics 2026-05-24 from https://api.ai-analytics.org/grant/nih/10795850. Licensed CC0.

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