Isembyld (apitegromab-mstn) is filed as Myostatin inhibitor monoclonal antibody. The sections below restate public label fields stored for this profile.
1 INDICATIONS AND USAGE ISEMBYLD is indicated for the treatment of spinal muscular atrophy (SMA) in adults and pediatric patients 2 years of age and older who are currently receiving a survival motor neuron 2 (SMN2)-targeted treatment. ISEMBYLD is a recombinant monoclonal antibody targeting proforms of myostatin, indicated for the treatment of spinal muscular atrophy (SMA) in adults and pediatric patients 2 years of age and older who are currently receiving a survival motor neuron 2 (SMN2)-targeted treatment. (1)
ISEMBYLD is a fully human monoclonal IgG4 antibody that binds to promyostatin and latent myostatin and inhibits the activation of myostatin, blocking myostatin signaling.
5 WARNINGS AND PRECAUTIONS Fractures: Serious fracture events have occurred in patients treated with ISEMBYLD. Use with caution in patients with a history of low bone density or multiple fractures. In patients who experience fractures, weigh the risks and benefits of continuing ISEMBYLD. (5.1) 5.1 Fractures ISEMBYLD may increase the risk of fractures, including serious fractures [see Adverse Reactions (6.1)]. In Study 1 [see Clinical Studies (14)], 5/53 (9%) of patients treated with ISEMBYLD 10 mg/kg and 3/53 (6%) of patients treated with ISEMBYLD 20 mg/kg (twice the recommended dosage) experienced fractures compared with one patient in the placebo group (2%) who had a fracture. Femur fractures occurred in three patients treated with ISEMBYLD in Study 1. No patients discontinued treatment due to fractures. In an ongoing open label extension study in which patients received ISEMBYLD 20 mg/kg (twice the recommended dosage), fractures occurred in 22 patients (9%), including 5 serious events of femur fractures. Most patients with fractures had histories of low bone density or previous fractures, or contractures. Some fracture events did not have a clear precipitating event (such as a fall). Animal studies have also demonstrated adverse effects in bone [see Nonclinical Toxicology (13.2)]. Use ISEMBYLD with caution in patients with a history of low bone density or multiple fractures. In patients who experience fractures, weigh the risks and benefits of continuing ISEMBYLD.
4 CONTRAINDICATIONS None. None. (4)
Upper respiratory tract infections (≥20%); Vomiting (≥20%); Cough (≥20%); Other viral infections (≥20%); Headache (≥20%); Gastroenteritis (≥20%); Pharyngitis (≥20%); Hypersensitivity (≥20%)
6 ADVERSE REACTIONS The following clinically significant adverse reactions are described elsewhere in the labeling: Fractures [see Warnings and Precautions (5.1)] Most common adverse reactions in SMA (incidence greater than or equal to 20% of patients treated with ISEMBYLD and more frequent than placebo) were upper respiratory tract infections, vomiting, cough, other viral infections, headache, gastroenteritis, pharyngitis, and hypersensitivity.(6.1) To report SUSPECTED ADVERSE REACTIONS, contact Scholar Rock, Inc. at 1-855-MED-SRRK (1-855-633-7775) 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 safety of ISEMBYLD for SMA was evaluated in a randomized, double-blind, and placebo-controlled study (Study 1) [see see Clinical Studies (14)]. In Study 1, ISEMBYLD was evaluated in 128 patients with SMA (2 to 21 years at the start of the study), which included 53 patients 2 to 12 years of age [mean 7 years of age] who received the recommended dosage of ISEMBYLD (10 mg/kg once every 4 weeks) for a mean exposure of 49 weeks. Of those 53 patients, 43% were female, 66% were White, 11% were of Hispanic or Latino ethnicity, 4% were Asian, and 2% were Black or African-American. The adverse reaction information presented below is from the patients who received the recommended dosage of ISEMBYLD, unless otherwise noted. The most common adverse reactions (reported in at least 20% of patients treated with ISEMBYLD and more frequently than in placebo) were upper respiratory tract infections, vomiting, cough, other viral infections, headache, gastroenteritis, pharyngitis, and hypersensitivity. Table 1 lists the common adverse reactions that occurred in at least 5% of patients treated with ISEMBYLD and at least 5% more frequently than placebo. Table 1: Adverse Reactions Reported in ≥ 5% of Patients with SMA Treated with ISEMBYLD 10 mg/kg and ≥ 5% More Frequently than in Placebo (Study 1) 1 Includes nasopharyngitis, rhinovirus infection, sinusitis, viral upper respiratory tract infection, upper respiratory tract infection, nasal congestion, rhinorrhea, rhinitis. 2 Includes metapneumovirus infection, parvovirus B19 infection, COVID-19, respiratory syncytial virus infection, respiratory syncytial virus bronchiolitis, influenza, parainfluenzae, adenovirus, respiratory tract infection viral, and viral infection. 3 Includes other similar terms. 4 Includes pharyngitis, pharyngitis streptococcal, oropharyngeal pain. 5 Includes dermatitis acneiform, dermatitis atopic, eczema, flushing, rash, rash maculo-papular, urticaria. 6 Includes application site reaction, catheter site pain, infusion related reaction, infusion site bruising, infusion site pain, injection site bruising, injection site pain. 7 Includes other similar terms 8 Includes foot fracture, clavicle fracture, femur fracture, tibia fracture, torus fracture. 9 Includes fatigue, lethargy. Adverse Reaction ISEMBYLD(10 mg/kg)(N = 53)% Placebo (N = 50)% Upper respiratory tract infections1 66 54 Vomiting 30 16 Cough 28 22 Other viral infections2 26 16 Headache 23 16 Gastroenteritis3 23 8 Pharyngitis4 21 14 Hypersensitivity5 21 16 Diarrhea 17 0 Injection site reactions6 13 0 Abdominal pain7 13 6 Arthralgia 13 4 Contusion 11 6 Fall 11 6 Fractures8 9 2 Fatigue9 9 2 Pain in extremity 9 4 Hematoma 6 0 Myalgia 6 0 Acute Respiratory Failure In Study 1, serious events of acute respiratory failure in the setting of lower respiratory tract infections occurred in two patients treated with ISEMBYLD at a dose of 10 mg/kg and in one patient that received placebo. Pneumonia In Study 1, serious adverse events of pneumonia occurred in three patients treated with ISEMBYLD at a dose of 10 mg/kg and in no patients that received placebo. Laboratory Findings Creatine Phosphokinase In Study 1, CPK increases were seen more frequently in patients treated with ISEMBYLD 10 mg/kg (n=53) compared to placebo (n=50). By month 12, mean CPK levels increased by 91 U/L in patients treated with ISEMBYLD compared to 3 U/L in placebo. Increases in CPK were seen in 28% of patients treated with ISEMBYLD, compared to 12% in placebo; among these, 3 patients (6%) treated with ISEMBYLD had CPK elevations of greater than 2.5 times the upper limit of normal (ULN), compared to none in placebo. Similar patterns of elevations were seen in patients receiving ISEMBYLD who were over 12 years of age compared to those 2 to 12 years of age. One patient with elevated CPK at baseline who received ISEMBYLD 20 mg/kg (twice the recommended dosage) in the 13 to 21 age group had further CPK increases to greater than 10 times the ULN. Patients with CPK elevations in Study 1 have generally been asymptomatic.
2 DOSAGE AND ADMINISTRATION The recommended dosage of ISEMBYLD is 10 mg/kg administered once every 4 weeks as an intravenous infusion over approximately 60 minutes to 120 minutes at an infusion rate no greater than 150 mL/hour. (2.1, 2.4) ISEMBYLD must be diluted in 0.9% Sodium Chloride Injection prior to administration (2.3) See Full Prescribing Information for important preparation and administration instructions. (2.3, 2.4) 2.1 Recommended Dosage The recommended dosage of ISEMBYLD is 10 mg/kg administered once every 4 weeks as an intravenous infusion over approximately 60 minutes to 120 minutes at an infusion rate no greater than 150 mL/hour. ISEMBYLD must be diluted prior to administration [see Dosage and Administration (2.3)]. Doses of ISEMBYLD of 20 mg/kg administered once every 4 weeks were also assessed in Study 1; however, this dosage is not recommended as it did not demonstrate additional efficacy [see Clinical Studies (14)]. 2.2 Recommendations Regarding Missed Dose If a planned dose is missed, it is recommended to administer ISEMBYLD as soon as possible and then restart the dosing schedule 4 weeks after the missed dose is administered [see Dosage and Administration (2.1)]. Alternatively, if a planned dose is missed, dosing may be resumed on the next scheduled dose to maintain the original dosing schedule. 2.3 Preparation Instructions ISEMBYLD must be diluted in 0.9% Sodium Chloride Injection to a final concentration of 5 mg/mL prior to intravenous infusion. The diluted solution for infusion must be prepared by a healthcare professional using aseptic technique as follows: Calculate the required dose (mg) of ISEMBYLD to be administered based on the patient’s weight and on the recommended dosage of 10 mg/kg. Determine the volume (mL) of ISEMBYLD needed and the correct number of vials to supply the calculated dose. Remove ISEMBYLD vials from the refrigerator and allow vials to warm to room temperature while remaining in the carton until time of use. Do not use external heat sources to warm ISEMBYLD vials because heat may damage the product. Do not shake. Visually inspect each vial of ISEMBYLD. ISEMBYLD is a clear to moderately opalescent, colorless to slightly yellow solution that is free from visible particulates. Do not use if the solution in the vial is discolored or particulate matter is present. Withdraw the required volume of ISEMBYLD from each vial using a sterile syringe and transfer to an infusion bag that is di(2-ethylhexyl)phthalate (DEHP)-free. Dilute ISEMBYLD to a final concentration of 5 mg/mL by adding the appropriate amount of 0.9% Sodium Chloride Injection to the infusion bag. Gently invert the bag to mix the solution. Do not shake. Do not mix or dilute with other drugs. Discard any unused ISEMBYLD remaining in the vial(s). The diluted solution should be administered immediately after preparation. If not used immediately, store the infusion bag, protected from light, either at room temperature (20°C to 25°C [68°F to 77°F]) or in a refrigerator at 2°C to 8°C (36°F to 46°F) for up to 4 hours (including preparation and infusion time). Do not freeze. 2.4 Administration Instructions If necessary, remove the diluted ISEMBYLD solution from the refrigerator and allow the diluted solution to warm to room temperature. Do not use external heat sources to warm ISEMBYLD diluted solution because heat may damage the product. Visually inspect the diluted ISEMBYLD solution for particles or discoloration prior to administration [see Dosage Forms and Strengths (3)]. Do not use if it is discolored, opaque, or foreign particles are seen. Use a dedicated line with an infusion set containing a 0.2 or 0.22 micron low protein binding polyethersulfone (PES) in-line infusion filter. Use infusion sets and lines that are di(2 ethylhexyl)phthalate (DEHP)-free. Infuse the diluted solution of ISEMBYLD intravenously over approximately 60 minutes to 120 minutes at an infusion rate no greater than 150 mL/hour. After completion of the infusion, flush the infusion line with 0.9% Sodium Chloride Injection to ensure that all the ISEMBYLD has been administered.
17 PATIENT COUNSELING INFORMATION Advise the patient to read the FDA-approved patient labeling (Patient Information). Missed Dose Instructions Inform patients that if a planned dose is missed, they should either: have ISEMBYLD administered as soon as possible and then maintain the regular dosing schedule 4 weeks after the missed dose is given, or the dose can be skipped and the next dose can be given as originally scheduled [see Dosage and Administration (2.2)]. Fractures Inform patients that ISEMBYLD may increase the risk of fractures, some of which can be serious [see Warnings and Precautions (5.1)]. Manufactured by: Scholar Rock, Inc. 301 Binney Street Cambridge, MA 02142 USA U.S. License No.: 2372 ©2026 Scholar Rock, Inc.
According to its FDA label, Isembyld (apitegromab-mstn) is approved for: 1 INDICATIONS AND USAGE ISEMBYLD is indicated for the treatment of spinal muscular atrophy (SMA) in adults and pediatric patients 2 years of age and older who are currently receiving a survival motor neuron 2 (SMN2)-targeted treatment. ISEMBYLD is a recombinant monoclonal antibod… For medical advice, please talk to your prescriber or pharmacist.
Isembyld (apitegromab-mstn) belongs to the Myostatin inhibitor monoclonal antibody class of medications.
The FDA label lists Isembyld (apitegromab-mstn) as: 3 DOSAGE FORMS AND STRENGTHS Injection: 150 mg/3 mL (50 mg/mL) apitegromab-mstn as a clear to moderately opalescent, colorless to slightly yellow solution in a single-dose vial. Injection: 150 mg/3 mL (50 mg/mL) solution in a single-dose vial. (3); intravenous route. Available strengths and packaging vary by manufacturer.
Not yet. As of the most recent FDA data we ingest, no A-rated generic equivalent is listed for Isembyld. Availability changes as patents expire.
Our ingest of the FDA label for Isembyld (apitegromab-mstn) does not include a Boxed Warning at this time. See the full label on DailyMed for the current, authoritative version.
The FDA Enforcement Report does not show an active/ongoing recall for Isembyld (apitegromab-mstn) in our latest ingest. Recall data can change daily — verify at FDA.gov.
The FDA record lists the approval date for Isembyld (apitegromab-mstn) as 2026-09-11.
The FDA label lists Scholar Rock, Inc. as a labeler/manufacturer of Isembyld (apitegromab-mstn). Multiple firms may market generics of the same molecule.
The FDA label states: "Storage and Handling Store ISEMBYLD vials in a refrigerator between 2°C to 8°C (36°F to 46°F) in the original carton to protect from light. Do not freeze. Do not shake. Discard unused portion. For storage of the diluted…" Follow the packaging insert for the authoritative guidance.
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