Background Beta-globinopathies, including beta-thalassemia and sickle cell disease (SCD), result from defective adult hemoglobin for which current treatments, including hydroxyurea and gene therapies, have variable efficacy, safety concerns, or limited accessibility. The transcription factor ZBTB7A represses gamma-globin expression, limiting fetal hemoglobin (HbF) production. Historically, transcription factors have been considered “undruggable.” We hypothesize that pharmacological degradation of ZBTB7A with SH6, a novel small-molecule degrader, could increase HbF, potentially serving as a treatment for beta-globinopathies.

Methods In vitro, CD34+ cells from healthy donors and patients with SCD or beta-thalassemia were isolated and differentiated into erythroid lineage, and treated with SH6 at varying concentrations. HbF levels, ZBTB7A protein expression, and cell viability were assessed by high-performance liquid chromatography (HPLC), flow cytometry, immunoblotting, and cell counting.

In vivo, immunodeficient NBSGW mice transplanted with human CD34+ hematopoietic stem and progenitor cells from healthy donors were randomized to SH6 (2.5 or 5 mg/kg) or vehicle for 21 days. Peripheral blood was monitored for engraftment. At endpoint, bone marrow and peripheral blood cells were analyzed for viability, lineage markers, and HbF levels using intracellular staining and cation-exchange HPLC. Toxicity was evaluated via complete blood counts, serum chemistries, organ weights, and histopathology.

Results In vitro, SH6 treatment of erythroid cultures from healthy donor CD34+ cells significantly increased gamma-globin expression and raised HbF levels from 11% to 34.7% by HPLC, with similar increases detected by flow cytometry, without affecting differentiation markers or cell expansion. In SCD and β-thalassemia patient-derived CD34+ cells, SH6 at 0.05 μM significantly increased HbF levels from 11% to 19% and from 26% to 36%, respectively, as reflected in flow cytometry analyses. SH6 elevated gamma-globin expression in patient-derived erythroid cells, including hydroxyurea-resistant lines.

In vivo, SH6 induced a significant, dose-dependent increase in HbF in human CD235a+ bone marrow cells within humanized mice, raising HbF from 2.5% in vehicle controls to 5% at 5 mg/kg, a level consistent with initial therapeutic thresholds reported in preclinical studies. SH6 also reduced ZBTB7A protein levels, confirming target engagement. Human hematopoietic engraftment remained stable, with preservation of erythroid differentiation markers and ability to reconstitute multiple lineages. SH6 was well tolerated, with normal serum chemistries, organ weights, and tissue histology.

Conclusion SH6 effectively elevates HbF in vitro and in vivo through ZBTB7A degradation, without impairing hematopoiesis or causing significant toxicity. These findings highlight SH6 as a potential novel therapy for beta-globinopathies.