Link Between Early Cytopenias and Clinical Outcomes in Lower-Risk MDS with Imetelstat

Overview

In patients with lower-risk myelodysplastic syndromes (LR-MDS) treated with imetelstat, early treatment-emergent cytopenias, specifically significant reductions in platelets and neutrophils within the first two cycles, were associated with improved hematologic responses. Notably, a ≥50% reduction in platelets correlated with greater hemoglobin increases and higher rates of red blood cell transfusion independence (RBC-TI).

Background

Myelodysplastic syndromes are characterized by ineffective hematopoiesis leading to cytopenias and risk of progression to acute myeloid leukemia. Imetelstat, a telomerase inhibitor, is approved for adults with LR-MDS who are transfusion-dependent and refractory or ineligible for erythropoiesis-stimulating agents. Previous studies demonstrated that imetelstat improves RBC-TI rates but is associated with early grade 3/4 neutropenia and thrombocytopenia, which are generally transient. Early cytopenias with other agents like lenalidomide have been linked to clinical response, prompting investigation of similar associations with imetelstat.

Data Highlights

Key Findings

• Grade 3/4 neutropenia and thrombocytopenia occurred early (median onset ~4 weeks) but were transient with low rates of severe clinical consequences.
• Patients with ≥50% platelet reduction within the first two cycles had significantly greater hemoglobin increases and higher likelihood of sustained Hb rise ≥1.5 g/dL.
• ≥50% platelet reduction was associated with significantly higher rates of ≥24-week RBC transfusion independence.
• ≥75% neutrophil reduction was linked to greater hemoglobin rise but not significantly associated with sustained Hb rise or RBC-TI rates.
• Early cytopenias may serve as biomarkers of on-target, disease-modifying effects of imetelstat in LR-MDS.

Clinical Implications

Monitoring early platelet and neutrophil count reductions during imetelstat therapy can provide prognostic information regarding hematologic response and transfusion independence in LR-MDS patients. The transient nature and low clinical complication rates of these cytopenias support their management with supportive care rather than treatment discontinuation. These findings may guide clinicians in anticipating and interpreting cytopenias as potential indicators of therapeutic efficacy.

Conclusion

Early treatment-emergent cytopenias, particularly significant platelet reductions, are associated with improved clinical outcomes in LR-MDS patients receiving imetelstat. These cytopenias likely reflect the drug’s on-target activity and can inform clinical management and prognostication.

References

1. IMerge Phase III Trial Results -- Imetelstat in LR-MDS
2. Lenalidomide Cytopenia Correlation Study -- del(5q) LR-MDS
3. IMerge Phase II and QTc Substudy Data -- Imetelstat Safety and Efficacy