2018 is shaping up to be an extraordinary year for novel drug approvals by the FDA, with another pair yesterday taking its tally to 55 with more than four weeks to go.
The approvals of Astellas’ FLT3 inhibitor Xospata (gilteritinib) for acute myeloid leukaemia and Catalyst Pharmaceuticals’ Firdapse (amifampridine) for rare autoimmune disease Lambert-Eaton Myasthenic Syndrome (LEMS), already put the number for 2018 nine in front of last year’s total – which was the highest level for more than 20 years.
The two new approvals are both breaking new ground, with Xospata becoming the first drug in the FLT3 inhibitor class to be approved for use in with relapsed or refractory AML with a FLT3 mutation, while Firdapse is the first treatment to be approved for LEMS, a rare neuromuscular disease estimated to affect three people per million worldwide.
Xospata has been cleared as a single-agent treatment for FLT3-positive AML, which the FDA notes is a particularly aggressive form of the blood cancer with a high risk of relapse. Its approval is based on the results of the ADMIRAL in 138 patients which revealed 21% experienced a complete remission (CR) or CR with partial haematological recovery.
“Xospata offers new hope to patients for whom the treatment path forward is unclear,” said Steven Benner, senior vice president and global therapeutic area head, Oncology Development, Astellas. “For the first time, people with relapsed or refractory FLT3 mutation-positive AML have an FDA approved FLT3-targeting treatment available to them.
The FDA green light is also big news for the Japanese company, trying to break into the increasingly important haemato-oncology field.
Astellas’ Steve Benner
“The approval of Xospata is also a proud, landmark moment for our oncology programme and marks the first approval of a medicine that will be the cornerstone of our new presence in blood cancers,” added Benner.
It is the second drug in the FLT3 inhibitor class to be approved in the US after Novartis’ Rydapt (midostaurin), which was approved for newly-diagnosed FLT3-positive AML by the FDA last year. Others are however moving through the late-stage pipeline, including Daiichi Sankyo’s quizartinib and Arog Pharma’s crenolanib. Like Xospata, these are both being tested initially in the relapsed/refractory AML setting.
Firdapse’s approval meanwhile is a massive step forward for patients with LEMS in the US, caused by an autoimmune reaction to calcium channels at the junction between nerves and muscles. It leads to significant muscle weakness, fatigue and other symptoms such as dry mouth.
Roughly half of LEMS cases are secondary to cancers, and particularly small cell lung cancer (SCLC), and is thought to be caused by an accidental attack of the neuromuscular junction by the immune system as it attempts to fight the cancer. The remainder are of unknown cause but may have a genetic component.
Amifampridine works by blocking potassium channels at the neuromuscular junction, which helps encourage the transport of calcium into nerve ending. The net result is that it increases levels of the neurotransmitter acetylcholine, which are reduced in LEMS as a result of the destruction of calcium channels.
The drug was originally developed by BioMarin, which got EU approval in 2009 and licensed it to Catalyst three years later. Sales in Europe were around $19m last year.