Adults with relapsed or refractory Acute Myeloid Leukemia (AML) have very few options for treatments until this month. The United States Food and Drug Administration (FDA) approved the first of a new class of cancer drug which is administered in a pill form. Tibsovo (ivosidenib) will be available for adults either suffering from an AML that has not responded to other therapies or for patients whose AML has returned after having been treated initially with another course of therapy. Tibsovo is an IDH1 inhibitor, meaning the pill prevents isocitrate dehydrogenase type 1’s (IDH1) neoplastic activity on a molecular biology level. IDH is an enzyme in the citric acid cycle and is found to be mutated in a variety of cancers, according to the literature.
According to Richard Pazdur, MD, the Director of the Oncology Center of Excellence and Office of Hematology and Oncology Products at the FDA, “Tibsovo is a targeted therapy that fills an unmet need for patients with relapsed or refractory AML who have an IDH1 mutation.” The clinical trials involving Tibsovo (also known as AG120) were associated with complete remission for some patients and reduction in required transfusions in other patients.
This drug was granted an FDA fast track and priority review label as well as an orphan drug description because this affects smaller numbers of patients with this an IDH1 mutation.
Testing has been developed for IDH1 and IDH2 genes and they are most often analyzed simultaneously; testing can be done on plasma for hematological disease like in this case. Solid tumors can also be tested. IDH1 mutations have been found in gliomas, chondrosarcomas, and cholangiocarcinomas, colon and lung cancers, and melanomas. For some of these cancers, the treatment options and prognosis are poor, so this new drug class presents potential options for them in the future. The current procedural terminology (CPT) code for this testing was updated in 2018 to include IDH1 (81120) and IDH2 (81121) from a previous Tier 2 molecular pathology code the previous year.
There are currently clinical trials underway examining the efficacy and safety of IDH inhibitor drugs in the US, France, China, and Germany for gliomas, (NCT02771301, NCT02454634, NCT02597335), myeloid neoplasms beyond AML (NCT03564821), and cholangiocarcinomas (NCT02989857).
Agios Pharmaceuticals, the producer of Tibsovo, has indicated that this treatment will be very expensive, perhaps topping six figures for the few months patients would be on it. There are also some side effects discussed in the video linked to this article but were found to be manageable.