The Food and Drug Administration (FDA) has approved Tibsovo (ivosidenib; Agios) for the treatment of adult patients with relapsed or refractory acute myeloid leukemia (AML) with a susceptible isocitrate dehydrogenase-1 (IDH1) mutation as detected by an FDA-approved test.

Tibsovo, a small molecule inhibitor, works by targeting the mutant IDH1 enzyme. In blood samples from patients with AML with mutated IDH1, ivosidenib decreased 2-hydroxyglutarate levels ex-vivo, reduced blast counts, and increased percentages of mature myeloid cells.

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The approval of Tibsovo was based on an open-label, single-arm, multicenter clinical trial (Study AG120-C-001) involving 174 patients with relapsed or refractory AML with an IDH1 miutation; patients received Tibsovo 500mg daily until disease progression, development of unacceptable toxicity, or undergoing hematopoietic stem cell transplantation. The most common IDH1 mutation types, identified via the Abbott RealTime IDH1 Assay, were R132C and R132H. The primary endpoint of the study was the combined complete remission (CR) and complete remission with partial hematologic improvement (CRh) rate. CRh was defined as <5% of blasts in the bone marrow, no evidence of disease and partial recovery of peripheral blood counts (platelets >50,000/microliter and ANC >500/microliter).

Treatment with Tibsovo resulted in a CR rate of 24.7% (median duration: 10.1 months), a CRh rate of 8% (median duration: 3.6 months), and a CR+CRh rate of 32.8% (mediation duration: 8.2 months). For patients who achieved a CR or CRh, the median time to CR or CRh was 2 months (range: 0.9 to 5.6 months). 

Among patients who were dependent on red blood cell (RBC) and/or platelet transfusions at baseline (N=110), 37.3% became independent of RBC and platelet transfusions during any 56-day post-baseline period. Of the patients who were independent of both RBC and platelet transfusions at baseline (N=64), 59.4% remained transfusion independent during any 56-day post-baseline period.

Tibsovo carries a Boxed Warning regarding the possibility of differentiation syndrome, which can be fatal if not treated. The most common adverse reactions associated with treatment include fatigue, leukocytosis, arthralgia, diarrhea, dyspnea, edema, nausea, mucositis, QT interval prolongation, rash, pyrexia, cough, and constipation.

Tibsovo is supplied as a 250mg tablet in 60-count bottles. 

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