Myozyme (Alglucosidase Alfa)
Enzyme replacement therapy for Pompe disease
Myozyme (alglucosidase alfa) is a recombinant enzyme replacement therapy used to treat Pompe disease (glycogen storage disease type II), a rare inherited metabolic disorder. Myozyme replaces the missing or deficient acid alpha-glucosidase (GAA) enzyme, helping to break down glycogen that accumulates in cells — particularly muscle cells. It is administered as an intravenous infusion every two weeks and is approved for use in patients of all ages, from newborns to adults.
Quick Facts
Key Takeaways
- Myozyme is the first approved enzyme replacement therapy specifically designed to treat Pompe disease in patients of all ages, including infants with the most severe form.
- It is administered as an intravenous infusion every two weeks at a dose of 20 mg/kg body weight, with the infusion rate gradually increased over time.
- Infusion-associated reactions (IARs), including potentially life-threatening anaphylaxis, are the most significant risk; pre-treatment with antihistamines and corticosteroids may be recommended.
- Clinical trials have demonstrated improvements in cardiac function, motor development, and survival in infantile-onset Pompe disease, and stabilization of respiratory and motor function in late-onset disease.
- Myozyme must be stored refrigerated (2–8°C) and reconstituted with sterile water before dilution with 0.9% sodium chloride for intravenous infusion.
What Is Myozyme and What Is It Used For?
Myozyme is used for the treatment of Pompe disease (also known as acid maltase deficiency or glycogen storage disease type II) in adults, adolescents, and children of all ages who have a confirmed diagnosis. Pompe disease is a rare, progressive, and often fatal inherited metabolic disorder caused by mutations in the GAA gene, which encodes the lysosomal enzyme acid alpha-glucosidase.
People with Pompe disease have low levels or a complete absence of an enzyme called acid alpha-glucosidase (GAA). This enzyme plays a critical role in controlling glycogen levels within lysosomes — the cellular compartments responsible for breaking down various substances. Glycogen is a complex carbohydrate that serves as a key energy source for the body. When GAA activity is insufficient, glycogen accumulates progressively in lysosomes, particularly in cardiac and skeletal muscle tissue, leading to cellular damage and organ dysfunction.
Myozyme contains a manufactured (recombinant) form of the human GAA enzyme called alglucosidase alfa, produced using Chinese hamster ovary (CHO) cell technology. When infused intravenously, alglucosidase alfa is taken up by cells through mannose-6-phosphate receptors on the cell surface, transported to lysosomes, and catalyzes the hydrolysis of accumulated glycogen to glucose. This process reduces the toxic buildup of glycogen and helps restore normal cellular function.
Pompe disease presents as a spectrum of clinical severity. Infantile-onset Pompe disease (IOPD), the most severe form, typically manifests within the first few months of life with hypertrophic cardiomyopathy, severe generalized muscle weakness (hypotonia), respiratory distress, and feeding difficulties. Without treatment, IOPD is usually fatal within the first year of life due to cardiorespiratory failure. Late-onset Pompe disease (LOPD) can present at any age from childhood to adulthood and is characterized by progressive proximal muscle weakness and respiratory decline, without the severe cardiomyopathy seen in the infantile form.
Clinical trials have demonstrated that Myozyme significantly improves survival and motor development in infantile-onset Pompe disease, reduces cardiac size, and improves cardiac function. In late-onset disease, treatment has been shown to stabilize and, in some cases, improve walking ability and pulmonary function compared to natural disease progression. The pivotal LOTS trial (Late-Onset Treatment Study) demonstrated that enzyme replacement therapy improved walking distance and stabilized respiratory function in adults with LOPD.
What Should You Know Before Taking Myozyme?
Contraindications
Do not use Myozyme if you have experienced life-threatening allergic (hypersensitivity) reactions to alglucosidase alfa or any of the other ingredients in this medicine, and if re-administration of the medicine was not successful. Symptoms of life-threatening allergic reactions include (but are not limited to) low blood pressure, very rapid heart rate, breathing difficulties, vomiting, swelling of the face, hives, or rash. If you have previously experienced a severe anaphylactic reaction to Myozyme, your healthcare team will carefully evaluate the risks and benefits before considering re-treatment, potentially using a desensitization protocol.
Warnings and Precautions
If you are treated with Myozyme, you may experience an infusion-associated reaction (IAR) during the administration or in the hours following the infusion. These reactions can range from mild to severe and may include symptoms such as low blood pressure, chest discomfort, throat swelling, facial or lip swelling (angioedema), hives (urticaria), dizziness, skin rash, itching, nausea, vomiting, cough, and bronchospasm. In some cases, infusion-associated reactions can be very serious or life-threatening.
If you experience a severe infusion reaction — such as difficulty breathing, chest tightness, swelling of the face or throat, or a sudden drop in blood pressure — seek immediate medical attention. Your healthcare team may slow or stop the infusion and administer emergency medications. Always have the infusion in a setting where resuscitation equipment is available.
You may require pre-treatment with medications before your Myozyme infusion to help prevent allergic reactions. These may include antihistamines, corticosteroids, or antipyretic (fever-reducing) medications. Your doctor will determine the most appropriate pre-treatment regimen based on your individual history and reaction profile.
In clinical studies, physicians have used immunosuppressive medications (drugs that reduce the immune system's activity) to decrease the formation of antibodies against alglucosidase alfa. Because Pompe disease can cause weakness in the respiratory muscles, patients are already at increased risk for serious respiratory infections. The use of immunosuppressive drugs may further increase this risk. Your doctor will carefully weigh the potential benefits of immune modulation against the risks of increased infection susceptibility.
If you experience severe skin lesions (wounds), contact your doctor. If your legs swell or you experience generalized swelling, contact your doctor immediately, as these may be signs of nephrotic syndrome, a kidney condition that has been reported in some patients receiving enzyme replacement therapy. Your doctor should consider discontinuing Myozyme treatment and initiating appropriate medical management. The decision to restart treatment should be based on a careful assessment of risks and benefits.
Drug Interactions
Tell your doctor or pharmacist about all medicines you are currently using, have recently used, or might use. While no formal drug interaction studies have been conducted with Myozyme, the following considerations apply:
| Interacting Drug | Type | Effect | Recommendation |
|---|---|---|---|
| Immunosuppressants (e.g., rituximab, methotrexate) | Moderate | May reduce antibody formation against alglucosidase alfa but increase infection risk | Used under specialist supervision to modulate immune response |
| Chloroquine / Hydroxychloroquine | Major | May inhibit intracellular uptake and lysosomal processing of alglucosidase alfa | Avoid concurrent use |
| Amiodarone | Moderate | Lysosomotropic agent that may interfere with enzyme uptake into lysosomes | Discuss with prescribing physician |
| Antihistamines (pre-medication) | Beneficial | Help prevent infusion-associated reactions | Commonly used as pre-treatment before infusion |
| Corticosteroids (pre-medication) | Beneficial | Reduce immune-mediated infusion reactions | May be prescribed as pre-treatment for infusion |
Pregnancy and Breastfeeding
There is limited experience with the use of Myozyme in pregnant women. Animal studies have not shown direct or indirect harmful effects on reproductive function, but adequate controlled studies in pregnant women are lacking. Myozyme should not be used during pregnancy unless clearly necessary, and the potential benefits must justify the potential risks to the fetus. Women of childbearing potential with Pompe disease should discuss family planning with their healthcare provider.
Limited data suggests that alglucosidase alfa is excreted in breast milk in very small amounts. No adverse effects on the breastfed infant are expected, and therefore breastfeeding may be considered during Myozyme treatment. However, you may wish to discuss with your doctor whether to discontinue breastfeeding as a precautionary measure during the first 24 hours after each dose of Myozyme. If you are pregnant or breastfeeding, think you may be pregnant, or are planning to have a baby, seek advice from your doctor before receiving this medicine.
Driving and Operating Machinery
Exercise caution when driving or using machines shortly after receiving a Myozyme infusion. Some patients may experience dizziness, drowsiness, tremor, and/or low blood pressure during or after the infusion, which could impair the ability to drive or operate machinery safely. If you experience any of these symptoms, do not drive or use machines until they have fully resolved.
This medicine contains less than 1 mmol sodium (23 mg) per vial and is therefore considered essentially sodium-free. This is relevant for patients on a controlled sodium diet.
What Is the Correct Dosage of Myozyme?
Myozyme is administered by a physician experienced in treating patients with Pompe disease. It is given as an intravenous (IV) infusion, meaning the medicine is delivered directly into a vein through a drip. The drug is supplied as a powder that must be reconstituted with sterile water and then diluted with 0.9% sodium chloride solution before administration.
Adults
Standard Adult Dosage
Dose: 20 mg/kg body weight
Frequency: Every 2 weeks (biweekly)
Route: Intravenous infusion
Initial infusion rate: 1 mg/kg/hour
Rate escalation: Increase by 2 mg/kg/hour every 30 minutes if tolerated
Maximum infusion rate: 7 mg/kg/hour
The infusion rate should be increased gradually over the course of the infusion. The infusion typically starts at a rate of 1 mg/kg/hour, and if no signs of infusion-associated reactions occur, the rate may be increased by 2 mg/kg/hour every 30 minutes, up to a maximum of 7 mg/kg/hour. For an average adult weighing 70 kg, the total dose per infusion would be 1,400 mg (28 vials). The total infusion time varies depending on tolerance but may range from approximately 4 to 7 hours.
Children and Adolescents
Pediatric Dosage (All Ages)
Dose: 20 mg/kg body weight
Frequency: Every 2 weeks
Route: Intravenous infusion
Note: Same dosing regimen as adults, adjusted by body weight
The recommended dose for children and adolescents is the same as for adults: 20 mg/kg body weight given every two weeks. In infantile-onset Pompe disease, early initiation of treatment is critical, as delays can lead to irreversible cardiac and muscular damage. Clinical trials in infants have used the same weight-based dosing regimen, with careful monitoring of infusion reactions given the potential for immune-mediated responses in very young patients.
Elderly Patients
No specific dose adjustment is required for elderly patients. The same weight-based dosing of 20 mg/kg every two weeks applies. However, elderly patients may have concurrent conditions that affect infusion tolerance, and closer monitoring may be warranted, particularly regarding cardiovascular and respiratory function during infusions.
Home Infusion
Your doctor may consider transitioning you to home infusion with Myozyme if it is safe and convenient for you. This is typically considered after you have received several infusions in a clinical setting without significant adverse reactions. Home infusions must be performed by a trained healthcare professional who is equipped to manage infusion-related reactions. If you experience adverse effects during a home infusion, the healthcare professional can stop the infusion and initiate appropriate medical treatment.
Missed Dose
If you have missed a scheduled infusion, contact your doctor as soon as possible to arrange a replacement appointment. Maintaining a regular every-two-week schedule is important for optimal therapeutic benefit. Do not attempt to “make up” a missed dose by receiving a double dose at your next appointment.
Overdose
If Myozyme is administered at a higher dose or faster infusion rate than recommended, you may experience infusion-associated reactions. Symptoms of overdose may include:
- Cyanosis (bluish discoloration of the skin and lips due to low oxygen levels)
- Increased heart rate, palpitations
- Breathing difficulties, cough
- Dizziness, headache, taste disturbance
- High blood pressure, flushing
- Tongue swelling, vomiting, diarrhea, nausea
- Chest pain, chest discomfort, throat tightness
- Fever, chills, feeling cold, redness at the infusion site
- Muscle pain, muscle spasms, skin redness
If any of these reactions occur, tell your doctor immediately. The infusion rate will be slowed or the infusion will be stopped, and corrective treatment may be given as needed.
| Patient Group | Dose | Frequency | Special Considerations |
|---|---|---|---|
| Adults | 20 mg/kg IV | Every 2 weeks | Gradual rate escalation; max 7 mg/kg/hr |
| Children & Adolescents | 20 mg/kg IV | Every 2 weeks | Same as adults; early treatment critical in IOPD |
| Infants (IOPD) | 20 mg/kg IV | Every 2 weeks | Initiate as early as possible; monitor cardiac function closely |
| Elderly | 20 mg/kg IV | Every 2 weeks | No dose adjustment; monitor for comorbidities |
What Are the Side Effects of Myozyme?
Like all medicines, Myozyme can cause side effects, although not everybody gets them. Side effects were mainly reported while patients were being treated or shortly afterwards (infusion-associated reactions). Some of these reactions were serious or life-threatening, including severe generalized allergic reactions (anaphylaxis) and anaphylactic shock. If you experience any severe reaction, seek immediate medical attention. You may require pre-treatment before subsequent infusions to prevent or reduce the severity of future reactions.
Some patients have experienced flu-like symptoms in connection with the infusion, with symptoms persisting for a few days after the infusion was completed. Your healthcare team will monitor you closely during and after each infusion and will adjust the infusion rate or stop the infusion if significant reactions occur.
Very Common
- Hives (urticaria)
- Rash
- Increased heart rate (tachycardia)
- Facial flushing
- Fever or elevated body temperature
- Cough
- Rapid breathing (tachypnea)
- Vomiting
- Low oxygen levels in the blood
Common
- Pallor (paleness)
- Elevated or high blood pressure
- Bluish skin discoloration (cyanosis)
- Chills, tremor
- Agitation, irritability
- Headache, dizziness
- Tingling or numbness (paresthesia)
- Pain or local reactions at infusion site
- Itching (pruritus)
- Nausea, diarrhea
- Facial, throat, or generalized swelling (angioedema)
- Swelling of arms and legs
- Chest discomfort, throat tightness
- Fatigue
- Muscle pain, muscle spasms
- Severe skin lesions
- Skin redness (erythema)
Not Known
- Swelling around eyes, periorbital edema
- Asthma, abnormal breath sounds (including wheezing)
- Breathing difficulties (including shortness of breath)
- Cold extremities (e.g., hands, feet)
- Low blood pressure (hypotension)
- Constriction of blood vessels (vasoconstriction)
- Bronchospasm
- Feeling of warmth or cold, general malaise
- Weakness (asthenia), drowsiness, fainting
- Burning sensation, excessive sweating
- Increased lacrimation (tearing)
- Mottled skin, restlessness
- Throat irritation, tissue hypoxia
- Decreased heart rate (bradycardia), cardiac arrest
- Palpitations, non-cardiac chest pain
- Conjunctivitis (eye inflammation)
- Abdominal pain, dyspepsia, swallowing difficulty
- Joint pain (arthralgia)
- Temporary cessation of breathing (apnea) or respiratory arrest
- Proteinuria (protein loss in urine)
- Nephrotic syndrome: swelling of the legs, generalized edema, and protein loss in urine
- Swelling and thickening of skin at infusion site (extravasation)
- Red palms (palmar erythema), transient skin discoloration
- Infusion site urticaria, infusion site pruritus, infusion site blistering
Contact your healthcare provider or seek emergency medical attention immediately if you experience signs of a severe allergic reaction: difficulty breathing, rapid heartbeat, swelling of the face, lips, or tongue, widespread hives, sudden drop in blood pressure, loss of consciousness, or cardiac symptoms during or after your Myozyme infusion.
It is important to report suspected side effects after the medicine has been authorized. This allows continued monitoring of the medicine's benefit-risk balance. Healthcare professionals and patients are encouraged to report suspected adverse reactions to their national regulatory authority (e.g., FDA MedWatch in the US, Yellow Card Scheme in the UK, EMA EudraVigilance in Europe).
How Should You Store Myozyme?
Keep this medicine out of the sight and reach of children. Do not use this medicine after the expiry date stated on the label after “EXP.” The expiry date refers to the last day of that month.
Unopened vials: Store in a refrigerator at 2°C to 8°C (36°F to 46°F). Do not freeze. Keep the vials in the outer carton to protect them from light.
After reconstitution: The reconstituted solution should be diluted immediately and the infusion should be started as soon as possible. Chemical and physical in-use stability has been demonstrated for up to 24 hours at 2°C to 8°C when stored protected from light. From a microbiological standpoint, the product should be used immediately. If not used immediately, in-use storage times and conditions prior to use are the responsibility of the user.
Disposal: Do not throw away any medicines via wastewater or household waste. Ask your pharmacist how to throw away medicines you no longer use. These measures will help protect the environment. As Myozyme is administered in healthcare settings, proper disposal of unused product and waste materials is handled by the healthcare facility according to local regulations for pharmaceutical waste.
What Does Myozyme Contain?
The active substance in Myozyme is alglucosidase alfa. Each vial contains 50 mg of alglucosidase alfa. After reconstitution with 10.3 mL of water for injections, the solution contains 5 mg of alglucosidase alfa per mL. After further dilution with 0.9% sodium chloride solution, the final concentration ranges between 0.5 mg/mL and 4 mg/mL.
Inactive Ingredients (Excipients)
- Mannitol (E421) — serves as a bulking agent and stabilizer for the lyophilized (freeze-dried) powder
- Sodium dihydrogen phosphate monohydrate (E339) — buffer component to maintain pH
- Disodium hydrogen phosphate heptahydrate (E339) — buffer component to maintain pH
- Polysorbate 80 (E433) — surfactant that helps stabilize the protein during reconstitution and prevents aggregation
Appearance and Packaging
Myozyme is a powder for concentrate for solution for infusion in a glass vial (50 mg per vial). Each pack contains 1, 10, or 25 vials. Not all pack sizes may be marketed in all countries. The powder is white to off-white in appearance. After reconstitution, the solution is a clear, colorless to pale yellow liquid that may contain thin white strands or translucent fibers. The reconstituted solution must be inspected visually and should not be used if it is discolored or contains particulate matter other than those described. The pH of the reconstituted solution is approximately 6.2.
Marketing authorization holder: Sanofi B.V., Paasheuvelweg 25, 1105 BP Amsterdam, Netherlands.
Manufacturer: Genzyme Ireland Limited, IDA Industrial Park, Old Kilmeaden Road, Waterford, Ireland.
How Does Myozyme Interact with Other Drugs?
No formal drug-drug interaction studies have been conducted with Myozyme. However, based on the drug's mechanism of action and pharmacological properties, several theoretical and clinically relevant interactions should be considered.
Lysosomotropic Agents (Avoid)
Drugs that accumulate in lysosomes or alter lysosomal pH — such as chloroquine, hydroxychloroquine, and amiodarone — may theoretically interfere with the intracellular uptake and enzymatic activity of alglucosidase alfa. These agents can raise lysosomal pH, which reduces the activity of acid hydrolases including the replacement enzyme. Co-administration with chloroquine or hydroxychloroquine should be avoided. If amiodarone is necessary for cardiac management, the potential impact on enzyme replacement therapy should be discussed with your treating physician.
Immunosuppressants (Use with Caution)
In some patients, particularly those with infantile-onset Pompe disease who develop high antibody titers against alglucosidase alfa, immunosuppressive medications may be used to reduce antibody formation and improve therapeutic efficacy. Agents that have been used in this context include rituximab, methotrexate, mycophenolate mofetil, and intravenous immunoglobulin (IVIG). The use of these agents requires careful consideration, as immunosuppression in patients with Pompe disease increases the risk of serious infections, particularly respiratory infections, in a population already vulnerable due to respiratory muscle weakness.
Pre-medications (Commonly Co-administered)
Antihistamines (such as diphenhydramine or cetirizine), corticosteroids (such as methylprednisolone or dexamethasone), and antipyretic medications (such as acetaminophen/paracetamol) are frequently administered before Myozyme infusions to reduce the risk and severity of infusion-associated reactions. These pre-medications are considered part of the standard infusion protocol and do not negatively impact the efficacy of Myozyme.
Frequently Asked Questions About Myozyme
Pompe disease is a rare inherited metabolic disorder caused by a deficiency of the enzyme acid alpha-glucosidase (GAA). Without sufficient GAA, glycogen accumulates in lysosomes throughout the body, particularly in cardiac and skeletal muscle cells. This progressive glycogen buildup causes muscle damage and weakness. Enzyme replacement therapy with Myozyme provides the missing enzyme externally, allowing cells to break down accumulated glycogen and reducing further damage. Without treatment, the most severe form (infantile-onset) is typically fatal within the first year of life.
The total infusion time varies depending on the patient's weight and tolerance. For a typical adult, the infusion may take approximately 4 to 7 hours. The infusion starts at a slow rate (1 mg/kg/hour) and is gradually increased every 30 minutes if tolerated, up to a maximum rate of 7 mg/kg/hour. The slow initial rate is necessary to minimize the risk of infusion-associated reactions. Over time, if infusions are well-tolerated, some patients may be able to complete their infusions more quickly at higher rates.
Yes, most patients treated with Myozyme develop antibodies (immunoglobulin G, or IgG) against alglucosidase alfa. In many cases, these antibodies do not significantly affect the clinical benefit of the treatment. However, some patients — particularly those with infantile-onset Pompe disease who have no residual GAA enzyme (known as CRIM-negative patients) — can develop high-sustained antibody titers that may reduce the efficacy of the therapy. In such cases, immune tolerance induction protocols using immunosuppressive agents may be considered.
No, Myozyme is not a cure for Pompe disease. It is an enzyme replacement therapy that manages the condition by providing the missing enzyme. Treatment must be continued lifelong, as stopping the infusions would allow glycogen to accumulate again. While Myozyme has been shown to significantly improve survival, cardiac function, and motor development in infantile-onset Pompe disease, and to stabilize respiratory and motor function in late-onset disease, it does not completely reverse all disease manifestations. Research into gene therapy and next-generation enzyme replacement therapies is ongoing.
Myozyme and Lumizyme both contain the same active ingredient, alglucosidase alfa, and are manufactured by Sanofi Genzyme. They differ primarily in their manufacturing process and scale. Myozyme was originally approved for use in all ages, while Lumizyme was initially approved only for late-onset Pompe disease in patients aged 8 years and older. The FDA later unified the labeling, and in many regions outside the US, only Myozyme is marketed. Both products provide the same therapeutic enzyme and have the same dosing regimen (20 mg/kg every two weeks). Your doctor will prescribe the product that is available in your region.
Myozyme must be reconstituted with 10.3 mL of water for injections per vial using aseptic technique. The water should be added slowly, drop by drop, along the side of the vial — not directly onto the freeze-dried powder. The vial should be tilted and gently rolled (not shaken or inverted) to dissolve the powder. The reconstituted solution contains 5 mg/mL and should be inspected for particles. It is then further diluted with 0.9% sodium chloride solution in an infusion bag to a final concentration of 0.5–4 mg/mL. A 0.2-micron low-protein-binding in-line filter should be used during administration. The entire process should be completed under aseptic conditions, and the infusion should begin within 3 hours of reconstitution.
References
- European Medicines Agency (EMA). Myozyme: EPAR — Product Information. Last updated 2024. Available at: ema.europa.eu
- U.S. Food and Drug Administration (FDA). Myozyme (alglucosidase alfa) Prescribing Information. Sanofi Genzyme, 2023.
- Kishnani PS, Corzo D, Nicolino M, et al. “Recombinant human acid alpha-glucosidase: major clinical benefits in infantile-onset Pompe disease.” Neurology. 2007;68(2):99–109. doi:10.1212/01.wnl.0000251268.41188.04
- van der Ploeg AT, Clemens PR, Corzo D, et al. “A randomized study of alglucosidase alfa in late-onset Pompe's disease.” N Engl J Med. 2010;362(15):1396–1406. doi:10.1056/NEJMoa0909859
- American College of Medical Genetics and Genomics (ACMG). “Pompe disease diagnosis and management guideline.” Genet Med. 2006;8(5):267–288.
- Toscano A, Schoser B. “Enzyme replacement therapy in late-onset Pompe disease: a systematic literature review.” J Neurol. 2013;260(4):951–959. doi:10.1007/s00415-012-6636-x
- World Health Organization (WHO). WHO Model List of Essential Medicines. 23rd edition, 2023.
- Cupler EJ, Berger KI, Leshner RT, et al. “Consensus treatment recommendations for late-onset Pompe disease.” Muscle Nerve. 2012;45(3):319–333. doi:10.1002/mus.22329
Medical Editorial Team
This article has been developed by the iMedic Medical Editorial Team, a group of licensed physicians and pharmacists with expertise in metabolic diseases, rare disorders, and clinical pharmacology. All content is reviewed according to international guidelines from the EMA, FDA, ACMG, and WHO.
Reviewed by board-certified specialists in metabolic medicine and clinical pharmacology. Evidence graded according to the GRADE framework.
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