Mirdametinib, formerly PD-0325901, is an oral and small molecule inhibitor of MEK1 and MEK2.
The company has already secured orphan drug designation from the US Food and Drug Administration (FDA) to treat of patients ≥ 2 years of age with neurofibromatosis type 1-associated inoperable plexiform neurofibromas that are progressing or causing significant morbidity.
SpringWorks is planning to start a phase 2b open-label and single-arm ReNeu trial in the third quarter of this year. The study will recruit both paediatric and adult NF1-PN patients.
NF1 is a rare genetic disorder, which causes due to mutations in the NF1 gene that encodes for neurofibromin, a crucial key suppressor of the MAPK pathway.
MAPK pathway is a major signalling network, which regulates cell growth and survival and plays a significant role in multiple oncology and rare disease indications.
Mirdametinib was assessed in various phase 1 and phase 2 clinical trials, which included more than 200 subjects.
The Neurofibromatosis Clinical Trial Consortium carried out a phase 2 trial to asses mirdametinib in 19 adolescent and adult patients with inoperable and symptomatic or growing plexiform neurofibromas.
Patients secured an oral dose of 2 mg/m2 BID with a maximum dose of 4 mg BID on a four-week cycle of three weeks-on, one week-off.
According to the company, eight patients (42%) achieved an objective response by cycle 12, prospectively defined as volumetric reduction in their target PN of at least 20%.
SpringWorks Therapeutics CEO Saqib Islam said: “This orphan designation in the European Union is another important recognition of the significant need for an effective treatment for patients with NF1, and follows the orphan drug and fast-track designations already granted for mirdametinib in the U.S. by the FDA.
“We expect to initiate our Phase 2b trial of mirdametinib in children and adults with NF1-PN this quarter and look forward to working closely with regulatory authorities throughout our development program.”