# Multiplex base/prime editors for in vivo selection of modified HSPCs in hemoglobinopathy

> **NIH NIH R01** · FRED HUTCHINSON CANCER RESEARCH CENTER · 2021 · $747,027

## Abstract

A significant obstacle in current hematopoietic stem cell (HSC) gene therapy studies has been the ability to
achieve persisting high-level engraftment of gene-modified cells to provide long-term therapeutic efficacy.
Subtherapeutic engraftment occurs even under full myeloablative conditioning and will likely become an even
bigger issue with nonmyeloablative and nongenotoxic conditioning. The only corrective measure for
subtherapeutic correction levels is an allogeneic HSC transplant, which subjects patients to the risks of graft-
versus-host disease. Here we propose an alternative, minimally toxic approach to increase engraftment
of gene-modified cells into the therapeutic range that avoids the significant side-effects associated with
myeloablative conditioning and allogeneic HSC transplantation. Our approach will be applied to sickle cell
disease (SCD) and ß-thalassemia, which represent the most common severe monogenic diseases worldwide.
Gene replacement therapies for these disorders have shown promising early results but also in many cases
subtherapeutic gene-correction levels. In this application, we propose an innovative strategy to enrich genome-
edited and therapeutically relevant HSC post-transplantation in the context of reduced, nonmyeloablative
conditioning. This strategy relies on three coordinated aims that collectively address current HSC gene
therapy/genome editing transplantation. Specific Aim 1 will optimize safety and efficacy of novel base
editors/prime editors to allow simultaneous modification of the therapeutic globin target and of the selection gene.
Specific Aim 2 will apply these novel editing tools to the modification of HSCs derived from both healthy or
sickle cell patients in order to support high levels of therapeutic globin production upon engraftment and drug
selection in the mouse xenograft model. Specific Aim 3 will build upon these findings to evaluate engraftment
and selection protocols for edited HSC in the clinically relevant rhesus macaque autologous transplant model in
the setting of reduced-intensity conditioning. To accomplish these aims, we assembled a multidisciplinary team
which includes investigators with complementary expertise in base editing/prime editing (Dr. Liu),
hemoglobinopathies (Dr. Weiss) and HSC biology and transplantation (Dr. Kiem). Our findings should be
applicable to other diseases in which genetically corrected cells do not have a natural selective advantage and
also to other reduced-intensity, nongenotoxic conditioning regimens. Collectively, the proposed studies will
define a safer and effective HSCs transplantation protocol that will serve as a foundation for clinical testing in
patients suffering from hemoglobinopathies and from other genetic diseases.

## Key facts

- **NIH application ID:** 10122590
- **Project number:** 2R01HL136135-05
- **Recipient organization:** FRED HUTCHINSON CANCER RESEARCH CENTER
- **Principal Investigator:** HANS-PETER KIEM
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2021
- **Award amount:** $747,027
- **Award type:** 2
- **Project period:** 2017-01-17 → 2024-12-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10122590

## Citation

> US National Institutes of Health, RePORTER application 10122590, Multiplex base/prime editors for in vivo selection of modified HSPCs in hemoglobinopathy (2R01HL136135-05). Retrieved via AI Analytics 2026-05-24 from https://api.ai-analytics.org/grant/nih/10122590. Licensed CC0.

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