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Laboratory issues in gene therapy and emicizumab
Annette E Bowyer1, Anna E Lowe2, Stefan Tiefenbacher3
1Department of Coagulation, Sheffield Haemophilia and Thrombosis Centre, Sheffield, UK.
Summary
Advances in haemophilia A and B treatments, like extended half-life factors and emicizumab, necessitate careful assay selection. Laboratories must evaluate diagnostic methods to ensure accurate clotting factor measurement and patient monitoring.
Area of Science:
- Hematology
- Clinical Diagnostics
- Pharmacology
Background:
- Haemophilia A and B treatments have advanced with extended half-life factor concentrates and targeted therapies like emicizumab.
- Newer treatments have revealed discrepancies between standard clotting factor assays (e.g., APTT-based) and chromogenic assays.
- Emicizumab, a factor VIII mimetic, interferes with certain haemostasis tests, impacting monitoring.
Purpose of the Study:
- To highlight the challenges in accurately measuring clotting factors (FVIII, FIX) with novel haemophilia treatments.
- To emphasize the need for evaluating assay methodologies due to reagent and product differences.
- To address the impact of emicizumab on common laboratory tests and the requirement for assay validation.
Main Methods:
- Review of current literature on haemophilia A and B treatment advancements.
- Analysis of discrepancies observed between one-stage APTT-based and chromogenic factor assays.
- Discussion of emicizumab's interference with haemostasis tests and laboratory adaptation strategies.
Main Results:
- Extended half-life factor concentrates and emicizumab present unique challenges for standard clotting assays.
- Emicizumab interferes with APTT-based assays and some chromogenic assays (those using human FIXa/FX).
- Chromogenic assays utilizing bovine FIXa/FX are unaffected by emicizumab, offering a reliable alternative.
Conclusions:
- Accurate monitoring of haemophilia patients requires careful consideration of assay methodologies and reagent composition.
- Laboratories must validate or adopt new assays to ensure reliable measurement of clotting factors in patients receiving novel therapies.
- Further research is needed on assay performance for gene therapy approaches in haemophilia.
