FORZINITY

1 INDICATIONS AND USAGE FORZINITY is indicated to improve muscle strength in adult and pediatric patients with Barth syndrome weighing at least 30 kg. This indication is approved under accelerated approval based on an improvement in knee extensor muscle strength, an intermediate clinical endpoint [see Clinical Studies (14) ] . Continued approval for this indication may be contingent upon verification and description of clinical benefit in a confirmatory trial. FORZINITY™ is a mitochondrial cardiolipin binder indicated to improve muscle strength in adult and pediatric patients with Barth syndrome weighing at least 30 kg. ( 1 ) This indication is approved under accelerated approval based on an improvement in knee extensor muscle strength, an intermediate clinical endpoint. ( 14 ) Continued approval for this indication may be contingent upon verification and description of clinical benefit in a confirmatory trial(s).

2 DOSAGE AND ADMINISTRATION For patients weighing 30 kg and greater, the recommended dosage is 40 mg subcutaneously once daily. ( 2.1 ) Reduce the dose in adults with severe renal impairment. ( 2.2 , 8.6 ). 2.1 Recommended Dosage The recommended dosage of FORZINITY in patients weighing at least 30 kg is 40 mg subcutaneously once daily. Patients should receive the dose at the same time each day. Missed Dose If a dose is missed, skip the dose and take the next dose of FORZINITY at the scheduled time. Do not take a double dose of FORZINITY. 2.2 Dosage Modifications For Renal Impairment Refer to Table 1 for dosage modifications in adults with renal impairment. Table 1: Recommended Dosage in Adults with Renal Impairment Estimated Glomerular Filtration Rate (eGFR) (mL/minute) Recommended Dosage Greater than or equal to 30 mL/minute 40 mg subcutaneously once daily Less than 30 mL/minute and NOT on dialysis 20 mg subcutaneously once daily There is insufficient information to recommend a dosage regimen in adults with eGFR less than 30 mL/minute and on dialysis. There is insufficient information to recommend a dosage regimen in pediatric patients weighing 30 kg or greater with renal impairment. 2.3 Important Administration Instructions FORZINITY is a clear, colorless to yellow aqueous solution that contains the preservative, benzyl alcohol. Visually inspect each vial of FORZINITY for particulate matter and cloudiness prior to administration, whenever solution and container permit. Do not use if the solution is cloudy or particulate matter is present. Adult patients or caregivers may administer FORZINITY after proper training in preparing FORZINITY vials for administration, if a healthcare provider determines that it is appropriate, and with medical follow-up as necessary. Use aseptic technique to prepare and administer FORZINITY. Administer FORZINITY by subcutaneous injection in the abdomen (at least 2 inches from the navel) or outer thigh and rotate the injection site daily. Do not inject where the skin is tender, bruised, red, or hard. Avoid injecting into scars or stretch marks. Refer to the Instructions for Use for preparation and administration. FORZINITY is for single-patient-use only. Do not mix other products in the same syringe. Discard vials 8 days after first opening.

4 CONTRAINDICATIONS Serious hypersensitivity to elamipretide or any of the excipients in FORZINITY [see Warnings and Precautions (5.2) ]. Serious hypersensitivity to any of the ingredients ( 4 , 5.2 )

5 WARNINGS AND PRECAUTIONS Benzyl alcohol toxicity : Do not use in neonates. ( 5.1 ) 5.1 Risk of Benzyl Alcohol Toxicity in Neonates FORZINITY is not approved for use in neonates. Serious adverse reactions, including fatal reactions, of new onset or worsening metabolic acidosis that progressed to neurotoxicity, and in some cases gasping syndrome, have been reported in low-birth weight neonates (less than 2,500 grams) and preterm neonates (gestational age less than 34 weeks) who received benzyl alcohol (BA)-containing drugs intravenously. FORZINITY is not approved for intravenous use [see Dosage and Administration (2.1) ] . Gasping syndrome is a life-threatening condition in neonates caused by BA toxicity and is primarily characterized by multiorgan dysfunction secondary to metabolic acidosis, which leads to gasping respirations and death. The minimum amount of BA at which these serious adverse reactions, including fatal reactions, may occur is not known (FORZINITY contains 20 mg of BA per mL). [See Use in Specific Populations (8.4) .] 5.2 Hypersensitivity Hypersensitivity reactions, including serious allergic reactions requiring emergency medical intervention, have been reported in patients receiving FORZINITY. These reactions have included skin manifestations such as rash, papular lesions, and eczematous dermatitis, as well as respiratory symptoms including cough [see Adverse Reactions (6.1) ] . Reactions may occur within minutes to months after treatment initiation. Monitor patients for signs and symptoms of hypersensitivity reactions during treatment. If a serious hypersensitivity reaction occurs, do not administer further doses of FORZINITY and institute appropriate emergency treatment, including epinephrine, antihistamines, and corticosteroids as clinically indicated. Patients who have experienced a serious hypersensitivity reaction should not be rechallenged with FORZINITY [see Contraindications (4) ] . For mild to moderate skin reactions, consider treatment with topical corticosteroids and oral antihistamines. Consider discontinuation of FORZINITY if persistent or severe skin reactions develop.

6 ADVERSE REACTIONS Most common adverse reactions are injection site reactions. ( 6.1 ) To report SUSPECTED ADVERSE REACTIONS, contact Stealth BioTherapeutics Inc. at 1-844-444-6486 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. In the FORZINITY clinical development program, 12 male patients aged 12 to 35 years with genetically-confirmed Barth syndrome received treatment with daily subcutaneous injections of 40 mg FORZINITY. Eleven of these 12 patients were Caucasian. Patients first participated in a double-blind, placebo-controlled crossover trial where they were randomized to one of two sequences: 12 weeks of FORZINITY in Period 1 then a 4-week washout followed by 12 weeks of placebo in Period 2 or 12 weeks of placebo in Period 1 then a 4-week washout followed by 12 weeks of FORZINITY in Period 2 Ten patients completed the randomized trial and entered the open-label extension period where they received FORZINITY once daily. Eight of these patients received FORZINITY for 168 weeks, three of whom received FORZINITY for a total of 192 weeks. Adverse reactions occurring more commonly on FORZINITY than on placebo include injection site reactions such as injection site erythema, pain, induration, pruritus, bruising, and urticaria (Table 2). Table 2: Summary of Adverse Drug Reactions in the Placebo-Controlled Crossover Study, Barth Safety Population Combined (Periods 1 and 2) Elamipretide Placebo N=12 N=12 n (%) n (%) Any local administration reaction 12 (100) 8 (67) Injection site erythema 12 (100) 3 (25) Injection site induration 8 (67) 2 (17) Injection site pruritus 8 (67) 2 (17) Injection site pain 9 (75) 5 (42) Injection site bruising 3 (25) 0 Injection site urticaria 3 (25) 0 Injection site hemorrhage 0 1 (8) Eosinophilia Increases in absolute eosinophil counts were noted frequently in studies where duration of administration of FORZINITY was 30 days or greater. Eosinophil counts generally peaked around 90 days after initial exposure (mean increase from baseline ~0.5 to 0.6 × 10 3 /uL) and returned to baseline levels after 6 to 12 months of continuous exposure or after discontinuation of FORZINITY. The elevation in eosinophils was not associated with clinical manifestations or changes in other laboratory parameters.

8.1 Pregnancy Risk Summary Barth Syndrome is a rare, X-linked, recessive, genetic disorder and is not likely to affect females. Therefore, there are no data with FORZINITY use in pregnant women to evaluate for a drug-related risk of major birth defects, miscarriage, or other adverse maternal or fetal outcomes. In animal reproduction studies, no adverse developmental outcomes occurred at any dose tested (see Data ). FORZINITY contains benzyl alcohol as a preservative. Because benzyl alcohol is rapidly metabolized by a pregnant woman, benzyl alcohol exposure in the fetus is unlikely. The background risk of major birth defects and miscarriage for the indicated population is unknown. All pregnancies have a background risk of birth defect, loss, or other adverse outcomes. In the U.S. general population, the estimated background risk of major birth defects and miscarriage in clinically recognized pregnancies is 2 to 4% and 15 to 20%, respectively. Data Animal Data In pregnant rats, once-daily intravenous infusion of elamipretide during the period of organogenesis [gestation day (GD) 7 to GD 17] did not result in embryo-fetal developmental toxicity at doses tested up to 10 mg/kg/day, approximately 4 times the clinical exposure at the maximum recommended human dose (MRHD) of 40 mg/day, based on area under the concentration-time curve (AUC). In pregnant rabbits, intravenous infusion with elamipretide once daily during the period of organogenesis (GD 7 to GD 19) did not result in embryo-fetal developmental toxicity at doses tested up to 50 mg/kg/day, approximately 10 times the clinical exposure at the MRHD, based on AUC. In a pre- and postnatal study in rats, elamipretide was subcutaneously administered at doses of 0, 5, 10 or 15 mg/kg/day throughout pregnancy and lactation (GD 6 to Lactation Day 20). No adverse developmental effects were observed at doses up to 15 mg/kg/day, approximately 6-times the clinical exposure at the MRHD, based on AUC.