By Luke Fletcher, MD
Imetelstat, a telomerase inhibitor, has shown interesting promise for ESA refractory or unlikely to respond low-risk Myelodysplastic syndrome (MDS). In the Phase 2 data presented at ASH (1), as well as data recently released from the phase 3 IMerge study (ClinicalTrials.gov identifier NCT02598661), imetelstat was shown to improve 8-week transfusion independence in comparison to the placebo, which was the primary endpoint of the study. It also met multiple secondary endpoints.
The IMerge study is a double-blind, randomized (2:1), placebo-controlled phase 3 trial comparing imetelstat to placebo in lower-risk MDS (IPSS low or intermediate-1) with relapsed, refractory or ineligible for ESAs (2). Patients must not have received hypomethylating agents or lenalidomide and must have been non-del(5q). The primary endpoint of the study was 8-week transfusion independence and secondary endpoints included 24-week transfusion independence. Subgroup analysis was also undertaken to compare lower-risk MDS subtypes, differences in transfusion burdens, and IPSS groups (low and intermediate 1). Statistical significance was defined as P<0.05.
The 8-week transfusion independence rate was 39.8% and significantly increased in comparison to the placebo (p<0.001). At 24 weeks, 28% of imetelstat patients were transfusion independent. Data was consistent across the subgroups in terms of benefit. The median rise in the responders was 3.6 g/dL hemoglobin.
Side effects were similar to prior studies with imetestat. The most frequent hematologic emergent adverse events included neutropenia and thrombocytopenia, however, clinical issues from these low counts such as infection or bleeding were similar between the groups, and recovery of cytopenias was higher in the imetelstat group.
With all this data to date, there is the expectation that imetelstat will be submitted for new drug application in mid-2023 and this is something to watch out for as a potential new option for low-risk MDS patients.
Platzbecker U, Komrokji RS, Fenaux P, et al. Imetelstat Achieved Prolonged, Continuous Transfusion Independence (TI) in Patients with Heavily Transfused Non-Del(5q) Lower-Risk Myelodysplastic Syndrome (LR-MDS) Relapsed/Refractory (R/R) to Erythropoiesis Stimulating Agents (ESAs) within the IMerge Phase 2 Study. Blood 2022; 140 (Supplement 1): 1106–1108. doi: https://doi.org/10.1182/blood-2022-169050
Geron Corporation. Geron Announces Positive Top-Line Results from IMerge Phase 3 Trial of Imetelstat in Lower Risk MDS. 1/4/2023. https://ir.geron.com/investors/press-releases/press-release-details/2023/Geron-Announces-Positive-Top-Line-Results-from-IMerge-Phase-3-Trial-of-Imetelstat-in-Lower-Risk-MDS/default.aspx