Enasidenib (IDHIFA): A Comprehensive Guide to Targeted Therapy for IDH2-Mutated Acute Myeloid Leukemia

　　Enasidenib,marketed under the brand name IDHIFA,is an oral small-molecule targeted agent designed to inhibit mutant isocitrate dehydrogenase 2(IDH2).It is approved for adult patients with relapsed or refractory acute myeloid leukemia(R/R AML)who carry a confirmed IDH2 mutation.As a precision-medicine therapy,enasidenib is not suitable for all AML patients.Prior to initiating treatment,a validated blood or bone marrow assay must confirm the presence of an IDH2 mutation to determine eligibility.

　　Mechanism of Action

　　Under normal physiological conditions,the IDH2 enzyme plays a role in cellular energy metabolism.Mutations in the IDH2 gene—most commonly R140Q,R172S,and R172K—cause the mutant protein to produce excessive amounts of the oncometabolite 2-hydroxyglutarate(2-HG).Accumulation of 2-HG disrupts epigenetic regulation and blocks normal myeloid cell differentiation,contributing to leukemogenesis.Enasidenib selectively binds to and inhibits mutant IDH2,reducing intracellular 2-HG levels,relieving the differentiation block,and promoting the maturation of abnormal myeloid precursors,thereby exerting its antileukemic effect.

　　Dosing and Monitoring

　　Before starting enasidenib,the treating team should complete baseline assessments including confirmation of IDH2 mutation status,complete blood counts,serum biochemistry,and evaluation of risks for leukocytosis and tumor lysis syndrome(TLS).The recommended dose is 100 mg taken orally once daily,with or without food.Tablets should be swallowed whole and must not be chewed,split,or crushed.Patients are advised to take the medication at approximately the same time each day.If a dose is missed or vomiting occurs after ingestion,the patient should follow the prescribing information for guidance on make-up dosing and resume the regular schedule the following day.

　　In the absence of disease progression or unacceptable toxicity,treatment should continue for a minimum of six months to allow adequate time for a clinical response.Therapy may be maintained until disease progression or intolerable adverse events occur.During the first three months of treatment,laboratory monitoring should be performed at least every two weeks,with close attention to hematologic parameters,biochemical markers,and early signs of differentiation syndrome.

　　Adverse Effects and Safety Management

　　Common adverse reactions observed with enasidenib(incidence≥20%)include elevated total bilirubin,hypocalcemia,nausea,diarrhea,hypokalemia,vomiting,decreased appetite,and hypophosphatemia.Serious adverse events may include marked hyperbilirubinemia,severe electrolyte disturbances,significant diarrhea,differentiation syndrome,non-infectious leukocytosis,and tumor lysis syndrome.

　　Differentiation syndrome is a distinctive and potentially life-threatening complication associated with IDH inhibitors.Clinical manifestations range from fever to acute renal impairment,hypoxia,respiratory failure,and,in severe cases,multi-organ dysfunction.Prompt recognition and intervention—including temporary drug discontinuation and corticosteroid administration—are critical.

　　Storage

　　Enasidenib should be stored at 20°C–25°C,with excursions permitted between 15°C and 30°C.Keep the bottle tightly closed and retain the tablets in their original container.The desiccant included in the bottle helps protect against moisture and should not be removed;transferring tablets to alternative containers is discouraged.

　　Special Population Considerations

　　Based on animal reproductive toxicity studies,enasidenib may cause fetal harm.Females of reproductive potential must use effective contraception during treatment and for at least two months after the last dose.Breastfeeding is not recommended during this period,as it is unknown whether enasidenib is excreted in human milk.Males with female partners of reproductive potential should also use effective contraception during treatment and for at least two months following the final dose.