(Reuters) - Nearly a third of patients with an advanced form of a fast-progressing leukemia who carry a specific genetic mutation experienced a complete or near complete response to an experimental Agios Pharmaceuticals drug, according to data from an early stage trial released on Monday.
The study tested Agios’ ivosidenib, a once-a-day pill, in patients with an IDH1 gene mutation who had relapsed or were not helped by prior treatment for acute myeloid leukemia (AML).
Of 125 patients available for evaluation in the expansion of a Phase I study, 30.4 percent experienced a complete response or a complete response with partial hematologic recovery (CRh), researchers reported. Both represent no detectable sign of the cancer, but with the latter category blood counts have not fully returned to normal.
The complete response rate was 21.6 percent, while 8.8 percent had a CRh at the time of data readout. The overall response rate was 41.6 percent, according to data unveiled at the American Society of Hematology conference in Atlanta.
The median duration of response was 9.3 months for patients who achieved a complete response. That fell to 6.5 months when including all responders.
This new data “is compelling and demonstrates impressive single-agent efficacy with durable responses in these high-risk patients,” Dr. Courtney DiNardo, the study’s lead investigator from MD Anderson Cancer Center in Houston, said in a statement.
Median overall survival data was not yet available for patients who achieved complete response or CRh, meaning more than half of those patients were still alive at the time of data cutoff. Median overall survival was 9.3 months for the partial responders versus just 3.9 months for those not helped by the drug.
Agios, which holds full rights to ivosidenib, said it plans to use the early data to seek swift approval of the medicine, a similar path that led to the August U.S. approval of Idhifa, which Agios shares with Celgene Corp..
Idhifa is approved to treat relapsed AML in patients with a similar genetic mutation known as IDH2. Combined, IDH1 and IDH2 mutations account for about 20 percent of all AML cases.
The vast majority of AML patients do not respond to chemotherapy and need new treatments for the rapidly progressing deadly blood cancer.
Serious but not fatal side effects reported in 8 percent of ivosidenib patients included above normal white blood cell counts and QT elongation, a type of heart arrhythmia.
Reporting by Bill Berkrot; Editing by Steve Orlofsky