1. Clinical Overview
Pegaspargase is a modified, pegylated form of the enzyme L-asparaginase, used as a chemotherapeutic agent. It is a conjugate of monomethoxypolyethylene glycol (PEG) and L-asparaginase derived from Escherichia coli. The pegylation significantly prolongs its plasma half-life and reduces immunogenicity compared to native asparaginase, making it suitable for patients with hypersensitivity to native forms. It is a cornerstone in the treatment of acute lymphoblastic leukemia (ALL).
| Onset | Duration | Bioavailability |
|---|---|---|
| Rapid depletion of plasma asparagine levels occurs within hours of administration. | The enzymatic activity and asparagine depletion can persist for approximately 2-3 weeks after a single dose. | 100% (Administered via intramuscular or intravenous routes only). |
2. Mechanism of Action
Pegaspargase hydrolyzes circulating L-asparagine to aspartic acid and ammonia. Lymphoblastic leukemic cells, particularly those of T-cell and B-cell lineage, have a deficient expression of the enzyme asparagine synthetase and are auxotrophic for asparagine. Depletion of this extracellular essential amino acid selectively inhibits protein and nucleic acid synthesis in these malignant cells, leading to cytotoxic cell death.
3. Indications & Uses
- First-line treatment of Acute Lymphoblastic Leukemia (ALL) in combination chemotherapy regimens (for both pediatric and adult patients).
- Treatment of ALL in patients who have developed hypersensitivity to native forms of L-asparaginase (E. coli or Erwinia derived).
4. Dosage & Administration
Adult Dosage: 2500 IU/m² body surface area (BSA) administered intramuscularly (IM) or intravenously (IV) every 14 days. The 3750IU vial is a standard strength; dosing is calculated based on BSA.
Administration: For IM use: Administer as a deep intramuscular injection into a large muscle mass (e.g., vastus lateralis). Do not inject more than 2 mL into a single site. For IV use: Dilute in 100 mL of 0.9% Sodium Chloride or 5% Dextrose injection. Administer over 1-2 hours via infusion. DO NOT administer as an IV push or bolus. Pre-medication with antihistamines, corticosteroids, and acetaminophen is often recommended to mitigate infusion-related reactions. Observe patient for at least 1 hour post-administration.
5. Side Effects
Common side effects may include:
- Elevated liver transaminases (AST/ALT)
- Hyperbilirubinemia
- Hypoalbuminemia
- Nausea/Vomiting
- Malaise/Fatigue
- Fever
- Allergic reactions (rash, urticaria)
6. Drug Interactions
| Drug | Effect | Severity |
|---|---|---|
| Warfarin and other Anticoagulants | Pegaspargase decreases synthesis of clotting factors (II, VII, IX, X), potentiating anticoagulant effect and increasing bleeding risk. | Major |
| Aspirin, NSAIDs | Increased risk of bleeding due to additive effects on platelet function and coagulation. | Major |
| Hepatotoxic drugs (e.g., Paracetamol/Acetaminophen in high doses, Azole antifungals, Statins) | Increased risk of severe hepatotoxicity. | Major |
| Pancreatotoxic drugs (e.g., Corticosteroids at high doses, Valproic acid) | Increased risk of pancreatitis. | Moderate |
| Methotrexate | Sequencing is critical. Pegaspargase given before high-dose methotrexate can reduce its clearance and increase toxicity. Typically, methotrexate is given before asparaginase in protocols. | Major |
| Vincristine | May increase risk of neurotoxicity. Some protocols recommend administering vincristine before pegaspargase. | Moderate |
| Live Vaccines | Risk of disseminated infection due to immunosuppression. Avoid vaccination during and for at least 3 months after therapy. | Major |
7. Patient Counselling
- DO report any signs of allergic reaction immediately: rash, itching, swelling of face/tongue, dizziness, trouble breathing.
- DO monitor your blood sugar levels regularly as instructed by your doctor.
- DO report severe or persistent abdominal pain, nausea, or vomiting.
- DO inform all your healthcare providers (including dentists) that you are on this medication.
- DO maintain adequate hydration.
- DONT take any new medications, including over-the-counter drugs, herbal supplements, or vitamins, without consulting your oncologist.
- DONT consume alcohol.
- DONT receive live vaccines without explicit approval from your oncologist.
8. Toxicology & Storage
Overdose: Symptoms would be an exacerbation of known toxicities: severe hepatotoxicity with jaundice, coagulopathy leading to hemorrhage, severe pancreatitis, hyperglycemic crisis, and profound allergic reactions.
Storage: Store unopened vials in a refrigerator at 2°C to 8°C. **DO NOT FREEZE.** Protect from light. The reconstituted solution (with Sterile Water for Injection) is stable for 48 hours if refrigerated at 2°C to 8°C. Do not use if the solution is cloudy or contains particulate matter. Discard any unused portion. It is a single-use vial.