Selumetinib: New Hope for Inoperable Plexiform Neurofibromas in NF1
A new treatment option is now available for adults living with neurofibromatosis type 1 (NF1) and inoperable plexiform neurofibromas (PN), a challenging condition where tumors grow along nerves. The Food and Drug Administration (FDA) , approved selumetinib (Koselugo, AstraZeneca Pharmaceuticals LP) for this specific patient population. This approval expands the use of selumetinib, which was previously approved for pediatric patients aged one year and older with the same condition.
Plexiform neurofibromas are often difficult to treat, particularly when they are inoperable – meaning they cannot be completely removed without causing significant health risks due to their location or size. These tumors can encase or grow close to vital structures, be highly invasive, or have a rich blood supply, making surgical removal too dangerous. For years, treatment options for adults with inoperable PN have been limited, making this new approval a significant step forward.
Selumetinib’s Efficacy Demonstrated in Clinical Trial
The FDA’s decision is based on data from the KOMET trial (NCT04924608), a global, randomized, double-blind, placebo-controlled study. The trial involved patients aged 18 years or older diagnosed with NF1 and symptomatic, inoperable PN. Patients were randomly assigned to receive either selumetinib or a placebo twice daily for 12 cycles.
The primary outcome measured was the confirmed overall response rate (ORR) at the end of Cycle 16, assessed by independent central review using specific criteria for evaluating tumor response in neurofibromatosis and schwannomatosis. Results showed a confirmed ORR of 20% (95% confidence interval: 11-31%) in the selumetinib arm, compared to just 5% (95% confidence interval: 2-13%) in the placebo group (p-value 0.011). Notably, 86% of patients in the selumetinib group experienced a duration of response lasting at least six months.
How Selumetinib Works and Potential Side Effects
Selumetinib is a MEK inhibitor. MEK is a protein involved in cell signaling pathways that can become overactive in certain cancers and conditions like NF1. By inhibiting MEK, selumetinib helps to slow or stop the growth of the tumor.
As with any medication, selumetinib carries potential risks and side effects. The prescribing information includes warnings and precautions related to left ventricular dysfunction (a weakening of the heart’s main pumping chamber), ocular toxicity (potential eye problems), gastrointestinal issues, skin reactions, increased levels of creatine phosphokinase (an enzyme released when muscle tissue is damaged), elevated vitamin E levels, and an increased risk of bleeding. Adverse reactions observed in adult patients were consistent with the known safety profile of the drug.
Understanding Neurofibromatosis Type 1 and Plexiform Neurofibromas
Neurofibromatosis type 1 (NF1) is a genetic disorder that causes tumors to form on nerves throughout the body. These tumors are usually benign (non-cancerous), but they can cause a range of health problems depending on their size and location. Plexiform neurofibromas are a specific type of NF1-related tumor that can grow along larger nerves and often involve multiple nerve branches. They can cause pain, disfigurement, and functional impairment.
The approval of selumetinib represents a significant advancement in the treatment of NF1-related plexiform neurofibromas in adults. While not a cure, it offers a new therapeutic option for individuals who previously had limited choices. Further research continues to evaluate the long-term benefits and optimal use of selumetinib in this patient population. The KOMET trial and other ongoing studies, such as NCI Phase I (NCT02407405), are contributing to a better understanding of selumetinib’s efficacy and safety.
Full prescribing information for KOSELUGO is available on Drugs@FDA. Patients and healthcare providers should carefully review this information to understand the potential benefits and risks of selumetinib before initiating treatment.