Positive results from Phase IIb trial of mirdametinib in NF1-PN

US drug developer SpringWorks Therapeutics (Nasdaq: SWTX) today announced what it described as positive top-line results from its Phase IIb ReNeu trial evaluating mirdametinib, an investigational MEK inhibitor, in pediatric and adult patients with NF1-associated plexiform neurofibromas (NF1-PN).

However, investors were not greatly impressed as, after a small 2% upturn pre-market, the stock was down 10.9% at $19.67 in mid-morning trading.

SpringWorks, which was spun out of Pfizer (NYSE: PFE) in 2017 with two assets – mirdametinib and nirogacestat, noted that the primary endpoint was confirmed objective response rate (ORR), defined as >= 20% reduction in target tumor volume as measured by MRI and assessed by Blinded Independent Central Review (BICR). As of the data cut-off of September 20, 52% (29/56) of pediatric patients and 41% (24/58) of adult patients had BICR confirmed objective responses within the 24- cycle treatment period (cycle length: 28 days).