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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 the liver to produce factor IX (FIX) in patients with hemophilia B, potentially eliminating the need for routine factor prophylaxis.
## Primary Indications
Treatment of adults with hemophilia B (congenital factor IX deficiency) who currently use 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 × 10¹¹ vector genomes per kilogram (vg/kg)**, administered as a single intravenous infusion.
## Pediatric Dosing
Not established. Safety and efficacy in patients under 18 years of age have not been established.
## Dose Adjustments
* **Renal/Hepatic Impairment:** No formal adjustments provided in the prescribing information. However, patients with pre-existing liver disease may have reduced efficacy or increased risk of transaminitis.
* **Administration:** Ensure the patient is premedicated (typically with corticosteroids) prior to infusion to mitigate immune response.
## Contraindications
* Hypersensitivity to the active substance or any excipients.
* Active, uncontrolled infections (acute or chronic), as systemic immune modulation is required for treatment.
## Adverse Effects
* **Common:** Elevated liver enzymes (ALT/AST), infusion-related reactions (nausea, headache, tachycardia), and fatigue.
* **Serious:** Immune-mediated hepatotoxicity (triggered by T-cell response to the viral capsid), which requires proactive management.
## Key Drug Interactions
* **Corticosteroids:** Concomitant use is mandatory for prophylactic immunosuppression for several weeks following infusion.
* **Hepatotoxic Agents:** Use with caution; monitor liver function closely in patients receiving other drugs cleared by the liver.
## Monitoring
* **Liver Enzymes:** Monitor ALT/AST weekly for at least the first 3 months post-infusion to detect and manage immune-mediated hepatotoxicity.
* **Factor IX Activity:** Monitor plasma FIX levels periodically to ensure therapeutic range is maintained and to determine the necessity/timing of tapering existing prophylaxis.
* **Vector Shedding:** Monitor per institution-specific biosafety protocols.
## Clinical Pearls
* **Immune Response:** The therapeutic effect is dependent on the durability of the transgene and the patient’s ability to tolerate the vector without mounting an inhibitory immune response.
* **Efficacy:** Patients may require supplemental factor IX during the initial weeks post-infusion before reaching stable endogenous production.
* **Antibodies:** Patients with pre-existing anti-AAV5 neutralizing antibodies may not be candidates for therapy; screening is required before administration.
* **Long-term:** Durability of response beyond several years is still under active investigation.
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*Disclaimer: This information is for educational purposes only. Prescribing information for gene therapies is complex and highly specific. Always consult the latest FDA-approved package insert/Summary of Product Characteristics (SmPC) and institutional clinical protocols before prescribing or administering this medication.*
