MYOZYME
Clinical safety rating: caution
Comprehensive clinical and safety monograph for MYOZYME (MYOZYME).
Alglucosidase alfa is a recombinant form of human acid alpha-glucosidase (GAA) that hydrolyzes glycogen to glucose in lysosomes. It replaces deficient GAA enzyme activity in patients with Pompe disease.
| Metabolism | Alglucosidase alfa is a protein; metabolism is expected to involve catabolic degradation via general protein catabolism pathways (e.g., proteolysis). |
| Excretion | Renal elimination is the primary route of clearance for alglucosidase alfa. Following intravenous administration, the drug is cleared via catabolism into small peptides and amino acids, which are then excreted renally. Less than 5% of the administered dose is excreted unchanged in urine. Biliary/fecal elimination is negligible. |
| Half-life | The terminal elimination half-life of alglucosidase alfa is approximately 2.3 hours at steady state. This short half-life necessitates weekly intravenous infusions to maintain therapeutic enzyme levels in target tissues. |
| Protein binding | Protein binding is approximately 10%. Alglucosidase alfa binds mainly to alpha-2-macroglobulin and other plasma proteins, but the binding is low and does not significantly affect distribution. |
| Volume of Distribution | The volume of distribution at steady state is approximately 0.24 L/kg, indicating limited distribution primarily within the vascular space and extracellular fluid. This is consistent with the large molecular weight of the enzyme, which restricts extravascular penetration. |
| Bioavailability | Alglucosidase alfa is administered intravenously, resulting in 100% bioavailability. No other routes of administration are clinically relevant. |
| Onset of Action | Following intravenous infusion, pharmacodynamic effects such as reduction in glycogen accumulation in tissues and improvement in cardiac function can be observed within weeks to months of initiating therapy. Clinical improvement in motor function and respiratory status typically becomes evident after 6 months of treatment. |
| Duration of Action | The duration of action is approximately one week, corresponding to the dosing interval. Weekly infusions are required to sustain enzyme levels adequate for continued glycogen clearance. Clinical effects are maintained with regular dosing. |
20 mg/kg IV every 2 weeks.
| Dosage form | INJECTABLE |
| Renal impairment | No specific dose adjustment required for renal impairment; however, monitor renal function due to potential nephrotoxicity. |
| Liver impairment | No specific dose adjustment required for hepatic impairment; safety and efficacy not established in severe hepatic impairment. |
| Pediatric use | 20 mg/kg IV every 2 weeks; same as adult dosing based on body weight. |
| Geriatric use | No specific dose adjustment required; use same weight-based dosing as adults. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for MYOZYME (MYOZYME).
| Breastfeeding | Unknown if excreted in human milk; M/P ratio not available. Consider developmental benefits of breastfeeding versus potential for adverse effects from immune response to enzyme. |
| Teratogenic Risk | Insufficient human data; animal studies show no evidence of fetal harm. Theoretical risk of immune-mediated effects due to enzyme replacement. No specific trimester risks identified. |
| Fetal Monitoring |
■ FDA Black Box Warning
None.
| Serious Effects |
["History of life-threatening hypersensitivity reaction (e.g., anaphylaxis) to alglucosidase alfa or any component of the formulation."]
| Precautions | ["Infusion-associated reactions (including anaphylaxis, hypotension, urticaria, rash, fever, rigors, vomiting, tachycardia, bronchospasm, and respiratory distress).","Severe cutaneous adverse reactions (e.g., Stevens-Johnson syndrome, toxic epidermal necrolysis).","Cardiac arrhythmias and sudden death in infantile-onset Pompe disease with cardiac hypertrophy.","Risk of acute cardiorespiratory failure in patients with compromised cardiac function or respiratory compromise."] |
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| Monitor for infusion-related reactions, hypersensitivity, and renal function. Fetal monitoring per standard obstetric care; no specific additional monitoring recommended. |
| Fertility Effects | No known effects on fertility in animal studies; human data lacking. No reports of impaired fertility. |