Trial reportThrombosis and haemostasis2024
Field Study and Correlative Studies of Factor IX Variant FIX-R338L in Participants Treated with Fidanacogene Elaparvovec.
Trial report in Thrombosis and haemostasis, 2024. The graph could read no effect estimate from its abstract, so it casts no vote on the map. It is linked to trial NCT02484092 (Gene Therapy, Open-label, Dose-escalation Study of PF-06838435), which is not on this map. Cited by 4 papers.
What it found
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The abstract states no effect estimate the extractor could read, or names no intervention and outcome on the map, so this paper lights no cell and moves no belief. It is still indexed, cited and linked below.
The trial behind it
Trials whose registry record cites this paper, or whose number appears in the abstract. A trial that started after this paper was published is citing it as background, not reporting it.
Gene Therapy, Open-label, Dose-escalation Study of PF-06838435 (SPK-9001) [Adeno-associated Viral Vector With Human Factor IX Gene] in Subjects With Hemophilia B
Who cites it
4 citing papers in PubMed.
- Population Modeling of Factor IX Activity Following Administration of Fidanacogene Elaparvovec Gene Therapy in Participants with Hemophilia B.Clinical pharmacokinetics · 2025Article
- Evaluation of One-Stage Assays for the Monitoring of Recombinant Human Factor IX Padua Activity After Etranacogene Dezaparvovec Gene Therapy.Haemophilia : the official journal of the World Federation of Hemophilia · 2025Article
- A year in pharmacology: new drugs approved by the US Food and Drug Administration in 2024.Naunyn-Schmiedeberg's archives of pharmacology · 2025Review
- Recent Advances in Gene Therapy for Hemophilia.Clinical and applied thrombosis/hemostasis : official journal of the International Academy of Clinical and Applied Thrombosis/HemostasisReview
Corrections and comments
PubMed lists nothing against this paper. Absence here is not a guarantee, only a check that was made.
Authors and funding
11 authors.
Funding
No grant is acknowledged in the PubMed record.
Abstract
backgroundFidanacogene elaparvovec, an adeno-associated virus-based gene therapy vector expressing the high-activity factor IX (FIX) variant FIX-R338L, is in development for hemophilia B. One-stage clotting (OS) assays and chromogenic substrate (CS) assays are commonly used to measure FIX-R338L variant activity. Data from ongoing trials suggest FIX activity varies between different OS and CS assays. MATERIAL AND
methodsTo better understand FIX-R338L activity in clinical samples, an international multisite field study was conducted across a central laboratory and 18 local laboratories, using standard protocols, reagents, and instrumentation, with individual participant samples from a phase 1/2a study of fidanacogene elaparvovec.
resultsUnlike the wild-type FIX control, FIX-R338L activity was higher with the OS silica-based assay versus OS ellagic acid-based and CS assays. Variation in FIX activity was greater at the lowest activity levels. Activated FIX (FIXa) in plasma could result in higher OS assay activity or increased thrombin generation, which could overestimate FIX activity. However, FIXa was not detected in the participant samples, indicating that it was not contributing to the OS assay differences. Since individuals on gene therapy may receive exogenous replacement FIX products, replacement products were spiked into patient plasma samples to target a therapeutic concentration. Exogenous FIX was additive to endogenous FIX-R338L, with no interference from FIX-R338L.
conclusionThese results demonstrate FIX-R338L activity can be measured with OS and CS assays in clinical laboratories and provide insight into assay variability when measuring FIX with endogenously produced FIX-R338L. The findings may help establish best practices for measuring FIX-R338L activity (Clinicaltrials.gov identifier: NCT02484092).
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