Imetelstat Approved for Certain Myelodysplastic Syndromes

The first-in-class targeted therapy inhibits telomerase, a cancer-promoting protein active in many cancers. 

The U.S. Food and Drug Administration (FDA) has approved imetelstat (Rytelo) for patients with low-risk or intermediate-1 risk myelodysplastic syndromes (MDS) who have anemia that requires transfusion of at least four red blood cell units over eight weeks and who are not responding to or are ineligible for medications that promote red blood cell production. 

Imetelstat was approved for certain myelodysplastic syndromes, a group of rare blood cancers.

Imetelstat is a targeted therapy that blocks the activity of telomerase, a cellular protein that promotes cancer by allowing cells to continue multiplying beyond what is considered normal. Telomerase is hyperactive in many cancers, including MDS. This is the first FDA approval for imetelstat and the first for any telomerase inhibitor. 

The approval is based on results from IMerge, a randomized, double-blind, placebo-controlled, multicenter, phase III clinical trial in which 178 patients with MDS were randomly assigned (2:1) to receive either imetelstat or placebo treatment until disease progression or unacceptable toxicity. All patients received supportive care, including red blood cell transfusions. 

Among patients treated with imetelstat, 39.8% were able to forego red blood cell transfusions for at least eight weeks, compared with 15% of patients who received placebo. Moreover, 28% of patients in the imetelstat arm went without transfusions for at least 24 weeks, compared with 3.3% of patients in the placebo arm. 

The recommended dosage for imetelstat is 7.1 mg/kg infused intravenously over 2 hours every 4 weeks. 

MDS are a group of rare blood cancers in which the patient’s body does not produce mature blood cells, often making the patient dependent on blood transfusions to maintain healthy blood cell levels. MDS are categorized as having a low, intermediate-1, intermediate-2, or high risk of progressing to acute myeloid leukemia, an aggressive blood cancer. MDS has been estimated to impact approximately 4 out of every 100,000 individuals in the United States each year. 

The FDA rendered its decision on June 6, 2024.