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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 *F9* gene. It is indicated for the treatment of adults with moderately severe to severe hemophilia B who are currently using Factor IX (FIX) prophylaxis therapy, or have current or historical life-threatening hemorrhage, or have repeated, serious spontaneous bleeding episodes.
## Primary Indications
Treatment of adults with moderately severe to severe hemophilia B (congenital Factor IX deficiency).
## Adult Dosing
* **Dose:** 5 x 10¹¹ vector genomes (vg) per kilogram of body weight.
* **Administration:** Administered as a single, one-time intravenous infusion. Use a dedicated intravenous line.
* **Maximum:** No dose escalation is permitted; the efficacy and safety of repeat dosing have not been established.
## Pediatric Dosing
* **Established Status:** Safety and efficacy have not been established in pediatric patients (<18 years). Use in this population is currently **not indicated**.
## Dose Adjustments
* **Renal/Hepatic Impairment:** No formal clinical trials exist for dose adjustment. Because the liver serves as the primary transduction site, patients with pre-existing hepatic impairment may have reduced efficacy or increased risk of transaminitis.
## Contraindications
* Hypersensitivity to the active substance or any excipient.
* Active infection (acute or chronic systemic).
## Adverse Effects
* **Most Common:** Elevation in liver enzymes (ALT/AST), infusion-related reactions, headache, nausea, and pyrexia.
* **Serious:** Immune-mediated hepatotoxicity (triggered by the viral vector).
## Key Drug Interactions
* **Corticosteroids:** Concomitant use is often required as part of the mandatory prophylactic immunosuppression protocol to manage transaminitis.
* **Hepatotoxic Agents:** Avoid or use with extreme caution due to the risk of additive liver stress.
## Monitoring
* **Liver Function:** Monitor ALT at least weekly for at least the first 3 months post-infusion to detect and manage immune-mediated hepatotoxicity.
* **Factor IX Activity Levels:** Monitor activity levels post-infusion to evaluate therapeutic response and determine the timing for tapering prophylactic Factor IX replacement therapy.
## Clinical Pearls
* **Immunosuppression:** Patients must be placed on a prophylactic corticosteroid regimen (e.g., prednisone 60 mg/day or equivalent) per manufacturer guidelines to mitigate the destruction of transduced hepatocytes by the immune system.
* **Tapering:** Do not discontinue prophylactic Factor IX concentrate immediately after infusion. Coordination between the hematology team and the gene therapy center is required to safely taper and discontinue exogenous FIX.
* **Storage:** Requires ultra-cold storage in the original vial until immediately prior to preparation.
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**Educational Disclaimer:** This information is for educational purposes for healthcare professionals and does not replace the official FDA-approved Prescribing Information. Always verify the most current prescribing information, institutional protocols, and safety guidelines before administration.
