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Jonathan Douxfils: Can We Estimate the VTE Risk of a Pill Before a Million Women Use It?
Jonathan Douxfils/LinkedIn
Dec 7, 2025, 16:21

Jonathan Douxfils: Can We Estimate the VTE Risk of a Pill Before a Million Women Use It?

Jonathan Douxfils, Board Member of Belgian Society on Thrombosis and Haemostasis, shared on LinkedIn:

”Can we estimate the VTE risk of a pill before a million women use it?

Today, the venous thromboembolism (VTE) risk of a new combined oral contraceptive (COC) is usually quantified years after launch, through large post-authorization safety studies.

In the meantime, clinicians and women must decide with incomplete information.

In our new article in RPTH Journal, we propose a different path: using a standardized biomarker – the normalized activated protein C sensitivity ratio (nAPCsr) – to predict population-based VTE risk for a given COC formulation.

Using >450 plasma samples from non-users and users of nine different COCs, we:

  • measured nAPCsr with a fully validated ETP-based APC resistance assay (ISO 17025, European Medicines Agency-endorsed for steroidal contraceptives), linked mean nAPCsr values to established VTE relative risks from de Bastos et al.’s network meta-analysis, built an exponential in silico model with R² = 0.96 and Spearman Rs = 1, accurately reproducing the known VTE risk hierarchy of EE/LNG, EE/“third-generation” progestins, and anti-androgenic combinations.

We then used this model to estimate VTE risk for COCs lacking mature epidemiology data in the de Bastos et al’s NMA, including EE30/DNG, EE20/DRSP, E2/NOMAC and E4/DRSP.

The predicted risks for E2- and E4-based pills fall closer to non-users and are consistent with emerging epidemiological data, supporting the concept that bioidentical estrogens may offer a safer hemostatic profile.

Why is this important?

– It shows that a harmonized biomarker (nAPCsr) can serve as a quantitative bridge between phase II–III trials and real-world VTE risk.
– It opens the door to earlier, more transparent risk categorization of new contraceptives, instead of waiting nearly a decade for PASS data.
– It offers regulators, companies and clinicians a common metric to compare the thrombotic profile of different pills beyond crude pharmacovigilance reporting.

Our hope is that this work will stimulate integration of validated coagulation biomarkers into regulatory decision-making, so that women and prescribers can discuss not only efficacy and cycle control, but also a more reliable, biomarker-informed estimate of VTE risk for each pill.

Congratulations to Laure Morimont for crowning achievement of this work and thank you to all the collaborators around this project and the co-authors of this paper, Mitchell Creinin, Ulysse Gapsard and Jean-Michel Foidart.”

Read the full article here.

Article: Predicting venous thromboembolism risk from ETP-based nAPCsr assay: toward early assessment of combined oral contraceptives.

Authors: Laure Morimont, Mitchell D. Creinin, Ulysse Gaspard, Jean-Michel Foidart, Jonathan Douxfils

Jonathan Douxfils: Can We Estimate the VTE Risk of a Pill Before a Million Women Use It?

Stay updated on all scientific advances in the field of thrombosis with Hemostasis Today.

COC Health Hematology Hemostasis Hemostasis Today Jean-Michel Foidart Jonathan Douxfils Laure Morimont Medicine Mitchell D. Creinin rpth thrombosis Ulysse Gaspard VTE
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