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# Durveqtix (fidanacogene elaparvovec)
## Overview
Durveqtix is an adeno-associated virus (AAV) vector-based gene therapy designed to deliver a functional copy of the *F9* gene to hepatocytes. It enables endogenous production of Factor IX (FIX) in patients with Hemophilia B, effectively replacing the need for routine prophylactic factor replacement therapy.
## Primary Indications
Treatment of moderate-to-severe Hemophilia B (congenital Factor IX deficiency) in adults who are currently using Factor IX prophylactic therapy, or have current or historical life-threatening hemorrhage, or have repeated, serious spontaneous bleeding episodes.
## Adult Dosing
The recommended dose is 5 x 10¹¹ vector genomes (vg) per kilogram (kg) of body weight, administered as a single, one-time intravenous infusion.
## Pediatric Dosing
Safety and efficacy have not been established in pediatric patients under 18 years of age. Use is currently restricted to adults.
## Dose Adjustments
No dose adjustments are permitted. The therapy is a one-time, weight-based infusion. It cannot be repeated due to the development of neutralizing antibodies against the AAV vector.
## Contraindications
- Known hypersensitivity to the active substance or any excipients.
- Active, uncontrolled infections (acute or chronic).
- Known significant pre-existing neutralizing antibodies to AAV serotype Rh74 (as determined by a validated assay).
## Adverse Effects
- **Common:** Increased liver enzymes (aspartate aminotransferase [AST], alanine aminotransferase [ALT]), nausea, fatigue, headache, and infusion-related reactions.
- **Serious:** Hepatotoxicity is the primary concern, requiring preemptive corticosteroid management to suppress immune response against the vector.
## Key Drug Interactions
- **Corticosteroids:** These are required concurrently and post-infusion to manage immune-mediated hepatitis risks.
- **Hepatotoxic Agents:** Avoid or use with extreme caution other drugs known to cause liver injury.
## Monitoring
- **Liver Function Tests (LFTs):** Weekly monitoring of ALT/AST is mandatory for at least 15 weeks post-infusion to detect and manage immune-mediated hepatitis.
- **Factor IX Activity:** Monitor plasma Factor IX activity levels periodically to assess therapeutic response.
- **Bleeding Episodes:** Monitor for signs of breakthrough bleeding.
## Clinical Pearls
- **Prophylactic Steroids:** Patients must begin a prophylactic corticosteroid regimen (usually prednisolone or equivalent) starting shortly before infusion and continuing for several weeks to prevent liver inflammation caused by the immune response to the vector.
- **Efficacy Onset:** Therapeutic Factor IX expression may take several weeks to stabilize; patients must continue to have Factor IX concentrate available for breakthrough bleeding during the early post-infusion period.
- **Long-term monitoring:** Patients will require long-term follow-up (up to 15 years) for assessment of sustained therapeutic effect and potential delayed adverse events.
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**Educational Disclaimer:** This information is for educational purposes only. Dosing, indications, and safety protocols for gene therapies are highly specialized and rapidly evolving. Always verify the most current prescribing information (e.g., Summary of Product Characteristics or FDA-approved labeling) and adhere to institutional protocols and manufacturer guidelines before considering or administering this therapy.
