What's Going On With Rare Diseases-Focused SpringWorks Therapeutics Stock Today?

SpringWorks Therapeutics Inc SWTX released topline results from its Phase 2b ReNeu trial evaluating mirdametinib, an investigational MEK inhibitor, in pediatric and adult patients with NF1-associated plexiform neurofibromas (NF1-PN).

The primary endpoint was confirmed objective response rate (ORR), defined as ≥ 20% reduction in target tumor volume. 

As of the data cutoff date of September 20, 2023, 52% (29/56) of pediatric patients and 41% (24/58) of adult patients had objective responses within the 24-cycle treatment period. 

However, investors were not impressed as the stock is trading lower mid-morning after a small upturn pre-market.

Neurofibromatosis type 1, a rare genetic disorder, is characterized by changes in skin coloring (pigmentation) and the growth of tumors along nerves in the skin, brain, and other body parts.

The ReNeu trial enrolled 114 patients in two cohorts (pediatric and adult).

An additional pediatric patient and two additional adult patients achieved confirmed objective responses after Cycle 24 in the long-term follow-up phase of the trial, where patients continue to receive mirdametinib treatment. 

The median best percent change from baseline in target tumor volume was -42% and -41% in the pediatric and adult cohorts, respectively. 

As of the data cut-off, the median duration of treatment was 22 months in both the pediatric and adult cohorts. The median duration of response was not reached in either cohort.

Mirdametinib was generally well tolerated in the ReNeu trial.

SpringWorks plans to submit a New Drug Application for mirdametinib to the FDA in the first half of 2024.

Price Action: SWTX shares are down 6.39% at $20.66 on the last check Thursday.