Mirdametinib

12.1 Mechanism of Action Mirdametinib is an inhibitor of mitogen-activated protein kinase kinases 1 and 2 (MEK1/2). MEK1/2 proteins are upstream regulators of the extracellular signal-related kinase (ERK) pathway. In vitro, mirdametinib inhibited kinase activity of MEK1 and MEK2 and downstream phosphorylation of ERK. In a mouse model of NF1, oral dosing of mirdametinib inhibited ERK phosphorylation and reduced neurofibroma tumor volume and proliferation.

1 INDICATIONS AND USAGE GOMEKLI is indicated for the treatment of adult and pediatric patients 2 years of age and older with neurofibromatosis type 1 (NF1) who have symptomatic plexiform neurofibromas (PN) not amenable to complete resection [see Clinical Studies (14) ]. GOMEKLI is a kinase inhibitor indicated for the treatment of adult and pediatric patients 2 years of age and older with neurofibromatosis type 1 (NF1) who have symptomatic plexiform neurofibromas (PN) not amenable to complete resection. ( 1 )

2 DOSAGE AND ADMINISTRATION The recommended dosage of GOMEKLI is 2 mg/m 2 orally twice daily, with or without food, for the first 21 days of each 28-day cycle. Continue treatment with GOMEKLI until disease progression or unacceptable toxicity. ( 2 ) 2.1 Recommended Evaluation and Testing Before Initiating GOMEKLI Prior to administration of GOMEKLI: conduct comprehensive ophthalmic assessment [see Warnings and Precautions (5.1) ]. assess ejection fraction (EF) by echocardiogram [see Warnings and Precautions (5.2) ]. 2.2 GOMEKLI Dosage Form Overview GOMEKLI is available in 2 dosage forms: capsules or tablets for oral suspension. GOMEKLI capsules: must be swallowed whole, do not open, break or chew capsules. GOMEKLI tablets for oral suspension: can be swallowed whole or can be dispersed in drinking water and administered orally as a liquid [see Dosage and Administration (2.4) ]. 2.3 Recommended Dosage The recommended dosage of GOMEKLI is 2 mg/m 2 orally twice daily (approximately every 12 hours) with or without food for the first 21 days of each 28-day cycle. The maximum dose is 4 mg twice daily. Continue treatment with GOMEKLI until disease progression or unacceptable toxicity. The recommended dose of GOMEKLI is based on body surface area (BSA) as shown in Table 1. Table 1: Recommended Dosage for GOMEKLI Body Surface Area (m 2 ) * Recommended Dosage for Capsules or Tablets for Oral Suspension 0.40 to 0.69 1 mg twice daily 0.70 to 1.04 2 mg twice daily 1.05 to 1.49 3 mg twice daily ≥1.50 4 mg twice daily * The recommended dosage for patients with a BSA less than 0.40 m 2 has not been established. Missed dose: If the patient misses a dose of GOMEKLI, do not take an additional dose. Take the next scheduled dose at the prescribed time. Vomiting: If vomiting occurs after GOMEKLI administration, do not take an additional dose. Take the next scheduled dose at the prescribed time. 2.4 GOMEKLI Preparation and Administration Instructions GOMEKLI Capsules Swallow GOMEKLI capsules whole with or without food. If more than one capsule is required for a dose, swallow one capsule at a time. Do not open, break or chew capsules. Do not administer to patients who are unable to swallow a whole capsule [see GOMEKLI Tablets for Oral Suspension]. GOMEKLI Tablets for Oral Suspension GOMEKLI tablets for oral suspension can be swallowed whole with or without food. If more than one tablet is required for a dose, swallow one tablet at a time. For patients who are not able to swallow whole tablets, prepare GOMEKLI tablets for oral suspension dispersed in drinking water and administer orally as a liquid [see Instructions for Use ]. Preparation and Administration Add the prescribed number of tablets to a dosing cup containing approximately 5 mL to 10 mL of drinking water. Gently swirl the water and tablets until the tablets are fully dispersed and an oral suspension is obtained. It takes approximately two to four minutes to fully disperse the tablets. Once the tablets are dispersed, the oral suspension will appear white and cloudy. Administer the oral suspension immediately after preparation from a dosing cup or oral syringe. After administration of the prepared suspension, add approximately 5 mL to 10 mL of drinking water to the dosing cup and gently swirl to resuspend any remaining particles. Administer the suspension to ensure the full dose is taken. Discard the oral suspension if not administered within 30 minutes after preparation. 2.5 Dosage Modifications for Adverse Reactions The recommended dose reductions for adverse reactions are provided in Table 2 . Table 2: Recommended Dose Reductions for GOMEKLI for Adverse Reactions Body Surface Area (m 2 ) Reduced Dose * Morning Evening 0.40 to 0.69 1 mg once daily 0.70 to 1.04 2 mg 1 mg 1.05 to 1.49 2 mg 2 mg ≥1.50 3 mg 3 mg * Permanently discontinue GOMEKLI in patients unable to tolerate GOMEKLI after one dose reduction. The recommended dosage modifications for adverse reactions are provided in Table 3 . Table 3: Recommended Dosage Modifications and Management of Adverse Reactions for GOMEKLI Adverse Reaction Severity Dosage Modification Ocular Toxicity [see Warnings and Precautions (5.1) ] Grade ≤ 2 Continue GOMEKLI at current dose level. Consider ophthalmologic examinations every 2 to 4 weeks until resolution to ≤Grade 1 or baseline. Grade ≥ 3 Withhold GOMEKLI until ≤Grade 1 or baseline. If recovery occurs ≤14 days, resume GOMEKLI at the next lower dose. If recovery occurs in >14 days, consider permanent discontinuation of GOMEKLI. Symptomatic Retinal Pigment Epithelium Detachment (RPED) Withhold GOMEKLI until ≤Grade 1 or baseline. Resume GOMEKLI at the same dose. Retinal Vein Occlusion (RVO) Permanently discontinue GOMEKLI. Left Ventricular Dysfunction [see Warnings and Precautions (5.2) ] Asymptomatic, absolute decrease in LVEF of 10% or greater from baseline and is less than the lower limit of normal Withhold GOMEKLI until ≤Grade 1. Resume GOMEKLI at reduced dose. Any absolute decrea

6 ADVERSE REACTIONS The following serious adverse reactions are described elsewhere in the labeling: Ocular Toxicity [see Warnings and Precautions (5.1) ] Left Ventricular Dysfunction [see Warnings and Precautions (5.2) ] Dermatologic Adverse Reactions [see Warnings and Precautions (5.3) ] Embryo-Fetal Toxicity [see Warnings and Precautions (5.4) ] Adults: The most common adverse reactions (>25%) were rash, diarrhea, nausea, musculoskeletal pain, vomiting, and fatigue. ( 6.1 ) The most common Grade 3 or 4 laboratory abnormality (>2%) was increased creatine phosphokinase. ( 6.1 ) Pediatric patients: The most common adverse reactions (>25%) were rash, diarrhea, musculoskeletal pain, abdominal pain, vomiting, headache, paronychia, left ventricular dysfunction, and nausea. ( 6.1 ) The most common Grade 3 or 4 laboratory abnormalities (>2%) were decreased neutrophil count and increased creatine phosphokinase. ( 6.1 ) To report SUSPECTED ADVERSE REACTIONS, contact SpringWorks Therapeutics Inc. at 1-888-400-7989 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch. 6.1 Clinical Trials Experience Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in practice. The pooled safety population described in the WARNINGS AND PRECAUTIONS reflects exposure to GOMEKLI in 133 patients (75 adults and 58 pediatric patients) in the ReNeu study [see Clinical Studies (14) ] (n=114) and Study NF-106 (n=19) [NCT-02096471]. Patients received GOMEKLI 2 mg/m 2 orally twice daily for the first 21 days of each 28-day cycle until disease progression or unacceptable toxicity. Among 133 patients who received GOMEKLI, 62% were exposed for one year or longer, 38% were exposed for 2 years or longer, and 12% were exposed for 3 years or longer. Neurofibromatosis Type 1-Associated Plexiform Neurofibromas The safety of GOMEKLI was evaluated in the ReNeu study [see Clinical Studies (14) ] . Eligible patients were 2 years of age and older with neurofibromatosis type 1 (NF1) who had symptomatic plexiform neurofibromas (PN). Patients were excluded for abnormal left ventricular ejection fraction (LVEF), uncontrolled hypertension, alanine transaminase (ALT) value of >2 × upper limit of normal (ULN), any current or history of retinal vein occlusion (RVO) or retinal pigment epithelium detachment (RPED), intraocular pressure >21 mmHg (or upper limit of normal adjusted by age), and history of glaucoma. Patients received GOMEKLI 2 mg/m2 orally twice daily for the first 21 days of each 28-day cycle until disease progression or unacceptable toxicity. Adult Patients The median age of adult patients (age ≥18) who received GOMEKLI was 35 years (range: 18-69); 64% were female; 85% were White, 9% were Black or African American, 3.4% were Asian, 3.4% were other races or race not reported; and 1.7% were Hispanic or Latino. For adult patients treated with GOMEKLI, the median duration of treatment was 22 months (range: 0.4 to 46 months). Serious adverse reactions occurred in 17% of adult patients who received GOMEKLI. Serious adverse reactions occurring in ≥1% of patients were COVID-19 (3.4%), nephrolithiasis (3.4%), and in 1 patient each: acute kidney injury, abdominal pain, ischemic colitis, urinary tract infection, retinal vein occlusion, scoliosis, squamous cell carcinoma of skin, cerebrovascular accident and chronic obstructive pulmonary disease. One fatal adverse reaction occurred in an adult patient (1.7%) who received GOMEKLI, due to COVID-19. Permanent discontinuation of GOMEKLI due to an adverse reaction occurred in 22% of adult patients. Adverse reactions which resulted in permanent discontinuation of GOMEKLI in ≥1% of adult patients were rash, diarrhea, nausea, abdominal pain, alopecia, dry skin, left ventricular dysfunction, cough, wheezing, COVID-19, peripheral swelling, RVO, dizziness, and vomiting. Dosage interruptions of GOMEKLI due to an adverse reaction occurred in 31% of adult patients. Adverse reactions which required dosage interruption in ≥5% of patients included left ventricular dysfunction and COVID-19. Dose reductions of GOMEKLI due to an adverse reaction occurred in 17% of adult patients. Adverse reactions which required dose reductions in ≥5% of patients included rash. The most common adverse reactions (>25%) were rash, diarrhea, nausea, musculoskeletal pain, vomiting, and fatigue. The most common Grade 3 or 4 laboratory abnormality (>2%) was increased creatine phosphokinase. Pediatric Patients The median age of pediatric patients (age ≤17 years) who received GOMEKLI was 10 years (range: 2 to 17); 54% were female; 66% were White, 20% were Black or African American, 9% were other races or race not reported, 3.6% were Asian, 1.8% were American Indian or Alaska Native; and 14% were Hispanic or Latino. For pediatric patients treated with GOMEKLI, the med