MEK Inhibitor Mirdametinib (PD-0325901) in Patients With Neurofibromatosis Type 1 Associated Plexiform Neurofibromas

Key Inclusion Criteria:

• Participant has documented NF1 mutation or a diagnosis of neurofibromatosis type 1 (NF1) using National Institute of Health (NIH) Consensus Conference criteriainclusive of the presence of a plexiform neurofibroma (PN).

• Participant has a PN that is causing significant morbidity.

• Participant has a PN that cannot be completely surgically removed.

• Participant has a target tumor that is amenable to volumetric MRI analysis.

• Participant is willing to undergo a tumor biopsy pre and post treatment if ≥ 18years of age.

• Participant has adequate organ and bone marrow function.

Key Exclusion Criteria:

• Participant has abnormal liver function or history of liver disease.

• Participant has lymphoma, leukemia or any malignancy within the past 5 years (exceptfor resected basal/squamous skin carcinomas without metastases within 3 years).

• Participant has breast cancer within 10 years.

• Participant has active optic glioma or other low-grade glioma requiring treatment.

• Participant has abnormal QT interval corrected or other heart disease within 6months.

• Participant has a history of retinal pathology, risk factors for retinal veinocclusion or has a history of glaucoma.

• Participant has known malabsorption syndrome or gastrointestinal conditions thatwould impair absorption of mirdametinib (PD-0325901).

• Participant has received NF1 PN-targeted therapy within 45 days.

• Participant previously received or is currently receiving therapy with mirdametinib (PD-0325901) or any other MEK1/2 inhibitor.

• Participant has received radiation therapy within 6 months or has received radiationto the orbit at any time.

• Participant is unable to undergo or tolerate MRI.

• Participant has active bacterial, fungal or viral infection.

• Participant has experienced other severe acute or chronic medical or psychiatricconditions within 1 year.