The oral inhibitor drug gilteritinib (XOSPATA®) was recently approved by the FDA based on interim results of the clinical trial ADMIRAL, according to an article in EurekAlert for Science News.
A total of 371 adult patients with relapsed or refractory (resistant to treatment) AML, and presenting with a mutation in the FLT3 gene, were included in the ADMIRAL trial. One arm of the trial, 247 patients, received the drug, gilteritinib, and 124 patients in the second arm were treated with chemotherapy.
It has been noted that patients diagnosed with FLT3 mutations who have relapsed and were then treated with chemotherapy exhibited a low response and poor survival.
In order to reduce the risk of relapse, oncologists would often use aggressive chemotherapy and bone marrow transplant. Gilteritinib has been designed for this group that until now had no other recourse.
About the Fms-like Tyrosine Kinase 3 (FLT3) Gene
FLT3 is a gene that creates fms-like tyrosine kinase 3 (FLT3) found in a group of receptor tyrosine kinases. These receptors send signals into the cells that are responsible for major cellular events. Additional information about FLT3 is available here.
Mutated FLT3 genes have been discovered in approximately thirty percent of leukemia cells. They are generally found in non-cancerous bone marrow where they regulate blood cells. If however, the gene becomes mutated cancer will metastasize unless a drug such as gilteritinib is administered to halt FLT3’s progress.
There are two prevalent FLT3 mutations. The first is the aggressive FLT3 internal tandem duplication (ITD) which is known to cause frequent relapses. Even when treated with current drugs it has an overall survival of about four months.
The second mutation is found in the tyrosine kinase domain (TKD) that is spread out in 300 residues. This mutation has shown resistance to many of the FLT3 inhibitors. Information about FLT3 mutations is available here.
About Gilteritinib XOSPATA® Trial Results
Gilteritinib has been proven to inhibit activity in both ITD and TKD. Astellas Pharma, Inc. is the manufacturer of the drug which is registered under the trade name of XOSPATA®.
A followup of overall survival found that 37% of FLT3 patients who were treated with gilteritinib were still alive at the one-year mark versus 16.7% of subjects who were treated with chemotherapy.
Results were similar when combining the rates of complete remission (no signs of cancer) or partial remission (incomplete blood count recovery). The gilteritinib cohort recorded 34% while the chemotherapy group recorded 15%.
Side effects were similar in both arms. They included febrile neutropenia (44%), anemia (34%), and fever from various causes (39%).
Severe adverse events that were possibly caused by gilteritinib were diminshed platelet count (24%), anemia (20%), and febrile neutropenia (15%). In addition, 11% discontinued as a result of various side effects.
Early Treatment May Increase Cure Rates
The side effects of gilteritinib were favorable, allowing the patients to receive the drug as outpatients. Gilteritinib’s safety factor means that it can stabilize the disease and enable patients to undergo bone marrow transplant and also continue treatment post transplant. This would reduce chances of a relapse.
The consensus is that using these well-tolerated agents at the onset of the disease could bring about improved cure rates for this very high-risk leukemia.