PB0700 - Evaluation of Pharmacological Enhancers of Mutated Factor VII Activity ex vivo

Background: As replacement therapy requiring intravenous injection is the mainstay of treatment for congenital factor (F) VII deficiency, there is an unmet need for new therapeutic strategies using less invasive delivery mechanisms. Drug repurposing allows for rapid, more cost-effective discovery and implementation of new treatments, and identification of pharmacological enhancers of FVII activity would be of clinical importance. High-throughput screening of >1500 FDA-approved drugs identified the orally available histone deacetylase inhibitor abexinostat and the inhaled surfactant tyloxapol as enhancers of FVII p.Q160R variant activity in patient’s plasma in an ex vivo pilot study.

Aims: To investigate the dose-response effect of the clinically approved drugs abexinostat and tyloxapol ex vivo in patient’s plasma.

Methods: Plasma samples from seven patients carrying FVII p.Q160R mutation were incubated with eleven different concentrations of abexinostat and tyloxapol (0.1µM-10µM) for 1.5 hours (h) at 37 °C. Equal amounts of FVII antigen of each sample were loaded onto the assay plates. FVII activity was analyzed using Biophen FVII assay and absorbance measured at 405nm for 2h, 37 °C. Data were analyzed using KNIME software.

Results: The initial velocity (V0) and absorbance (A405) at 2h were calculated. Both treatments showed a dose-response effect in patient’s plasma. Abexinostat showed an EC50 value of 2,87µM (SEM ±0,554) in six patients. The change of magnitude in FVII activity was approximately 19% (SEM ±1,885). Tyloxapol demonstrated an EC50 of 2,43µM (SEM ±0,320) and the change of magnitude in FVII activity was 21,64% (SEM ±3,14).

Conclusion(s): These results showed that treatment with the FDA approved drugs abexinostat and tyloxapol increased FVII activity about 20% in patient’s plasma ex vivo. It is of importance that a modest increase of FVII activity can ameliorate the bleeding phenotype in patients. This proof-of-concept study demonstrates that drug repurposing may be feasible for novel treatment of FVII deficiency.