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# Durveqtix (fidanacogene elaparvovec-dzkt)
## Overview
Durveqtix is an adeno-associated virus vector-based gene therapy designed to deliver a functional copy of the human coagulation Factor IX (FIX) gene to the liver. It provides a one-time treatment to increase endogenous FIX activity in patients with Hemophilia B.
## Primary Indications
Treatment of adults (≥18 years) with moderate-to-severe Hemophilia B (congenital Factor IX deficiency) who are currently using Factor IX prophylactic therapy or have a history of life-threatening hemorrhage or repeated, serious spontaneous bleeding episodes.
## Adult Dosing
The recommended dose is 5 x 10¹¹ vector genomes (vg) per kilogram of body weight, administered as a single intravenous (IV) infusion.
## Pediatric Dosing
Safety and effectiveness in pediatric patients (younger than 18 years) have not been established. Use is currently restricted to adults.
## Dose Adjustments
* **Renal/Hepatic Impairment:** No formal clinical studies have been conducted. Use caution in patients with underlying hepatic impairment, as transgene expression is liver-dependent.
* **Baseline Antibodies:** Patients must be screened for pre-existing anti-AAVRh74 antibodies. Patients who test positive are currently excluded from treatment as efficacy is significantly reduced.
## Contraindications
* Patients with documented hypersensitivity to fidanacogene elaparvovec-dzkt or any of its components.
* Patients with active, severe infections (acute or chronic).
* Presence of neutralizing antibodies against AAVRh74.
## Adverse Effects
* **Most Common:** Elevated liver transaminases (ALT/AST), infusion-related reactions, nausea, vomiting, thrombocytopenia, and headache.
* **Serious:** Immune-mediated hepatotoxicity (triggered by host response to the viral vector).
## Key Drug Interactions
* **Corticosteroids:** Concomitant use is required post-infusion to manage immune responses.
* **Hepatotoxic Agents:** Avoid or use with extreme caution other agents known to cause liver injury, as these may exacerbate monitoring challenges for transaminitis.
## Monitoring
* **Liver Function:** Monitor ALT/AST levels at least weekly for the first 3 to 4 months post-infusion.
* **Factor IX Activity:** Monitor FIX levels periodically to ensure therapeutic expression.
* **Infusion Reaction:** Close observation for signs of hypersensitivity, including cytokine release, during and for at least 3 hours post-infusion.
## Clinical Pearls
* **Prophylactic Immunosuppression:** Patients typically require a tapering course of corticosteroids initiated shortly after infusion to prevent or mitigate the immune-mediated destruction of transduced hepatocytes (which leads to loss of FIX expression).
* **One-Time Only:** This is a non-repeatable therapy due to the development of neutralizing antibodies post-administration.
* **Management of Bleeding:** Patients may still require exogenous FIX replacement therapy during the initial weeks post-infusion until steady-state FIX expression is fully achieved.
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**Educational Disclaimer:** This information is for educational purposes only. Always consult the most current FDA-approved Prescribing Information (Package Insert) and institutional protocols before administering gene therapy products. Clinical guidelines for gene therapy are subject to rapid change.
