Imetelstat, as a novel telomerase inhibitor, provides a new targeted treatment option for selected patients with myelodysplastic syndromes. The following overview covers three aspects: indications, dosing regimen, and dose adjustment.
I. Indications and Eligible Patients
1. Approved Therapeutic Indication
(1) Imetelstat is indicated for adult patients with myelodysplastic syndromes classified as lower-risk or intermediate-1 risk per the International Prognostic Scoring System (IPSS).
(2) These patients must have transfusion-dependent anemia, defined as requiring 4 or more units of red blood cells within an 8‑week period.
2. Prior Treatment and Resistance Requirements
Eligible patients must meet at least one of the following criteria: no response to prior erythropoiesis‑stimulating agent (ESA) therapy, loss of response after prior effectiveness, or inability to receive ESA therapy for any reason.
3. Relevant Exclusions
(1) Patients with a 5q deletion cytogenetic abnormality, or those previously treated with lenalidomide or hypomethylating agents, are not within the approved indication.
(2) These exclusion criteria help identify the patient population most likely to benefit.
II. Standard Dosing Regimen
1. Recommended Dose and Calculation
(1) The standard dose of imetelstat is 7.1 mg/kg, calculated based on the patient's actual body weight.
(2) Dose calculation must be precise; preparation may require combining the 47 mg and 188 mg lyophilized powder vial strengths to match the individualized dose requirement.
2. Route of Administration and Infusion Time
(1) The drug must be administered via intravenous infusion, with each infusion lasting a fixed duration of 2 hours.
(2) The infusion process must be monitored throughout by qualified healthcare professionals; the infusion rate must not be increased, nor the infusion time shortened.
3. Treatment Cycle and Duration
(1) Dosing occurs once every 4 weeks, constituting one complete treatment cycle.
(2) If after 24 weeks of continuous treatment (i.e., 6 administrations) the patient's red blood cell transfusion burden has not decreased, treatment discontinuation should be considered.
(3) This stopping rule facilitates timely efficacy assessment and avoids continuation of ineffective therapy.
III. Dose Adjustment and Special Management
1. Dose Reduction for Adverse Reactions
(1) When grade 3 or 4 adverse reactions occur, a stepwise dose reduction is required: first reduction to 5.6 mg/kg, second reduction to 4.4 mg/kg.
(2) If the patient still cannot tolerate the lowest dose, permanent treatment discontinuation is necessary.
2. Temporary Management of Hematologic Abnormalities
(1) If pre‑dose testing shows an absolute neutrophil count below 1.0×10⁹/L, or a platelet count below 50×10⁹/L, the scheduled dose should be withheld until values recover to safe levels, and then reassessed for continuation.
(2) Based on the severity and frequency of adverse reactions, the physician will decide whether to resume the original dose, reduce the dose, or discontinue treatment in subsequent cycles.
3. Special Population Considerations
(1) The safety and efficacy of imetelstat in children have not been established.
(2) No significant pharmacokinetic differences were observed between elderly patients (aged 65 years and older) and younger adults; no age‑specific adjustment is required.
(3) Mild to moderate hepatic or renal impairment does not have a clinically significant effect on drug metabolism, but data in severe impairment are insufficient; use with caution in such patients.
Note: This content is intended as a scientific overview of drug information and does not serve as clinical prescribing guidance. Specific treatment plans should strictly follow the prescribing instructions and supervision of the attending physician.
