# TFPI, Protein S, and Plasma FIXa in Hormone-Induced Hypercoagulability

> **NIH NIH R01** · VERSITI BLOOD HEALTH, INC. · 2021 · $703,988

## Abstract

Venous thromboembolism (VTE) in women taking oral contraceptives (OC) is a problem of broad clinical
significance that is mediated, at least in part, by estrogen effects on the expression of blood coagulation
proteins by the liver or vasculature. Our overall goal is to identify and characterize the underlying coagulation
pathways leading to OC-induced hypercoagulability and to identify genetic factors prevalent in individuals at
highest risk for VTE. OC use decreases the plasma concentration of two endogenous anticoagulant proteins,
tissue factor pathway inhibitor (TFPI) and protein S (PS) that modulate plasma FIXa production and activity.
We have developed a highly sensitive and specific (<10 pmol/L) technique for measurement of plasma FIXa
activity using an enhanced thrombin generation assay, which amplifies the FIXa signal from subject plasma via
thrombin generation in FIX-deficient plasma. Using this assay in plasma samples from blood donors we found
that OC-induced changes in TFPI and PS are associated with elevated plasma factor IXa (FIXa) activity in
~30% of women taking OC. Our central hypothesis is that OC use alters the inhibition of procoagulant
responses by the natural anticoagulants TFPI and PS, producing large increases in plasma factor IXa (FIXa)
activity and a systemic hypercoagulable state. This hypothesis will be probed to identify biochemical and
genetic correlates of OC-induced hypercoagulability. Biochemical studies using recombinant FIX variants
resistant to antithrombin or PS binding will be used to define how TFPI and PS modulate FIXa generation in
human plasma-based systems. The clinical impact of the biochemical findings will be examined by
measurement of plasma levels of TFPI, PS, and FIXa, GWAS analysis, and a thrombosis history questionnaire
in two cohorts of pre-menopausal women: 1) a cross-sectional cohort of ~1000 pre-menopausal blood donors;
and 2) a longitudinal cohort of ~45 adolescent girls to be followed for one year after initiation of OC-therapy.
The data collected in the cross-sectional cohort will be modeled to identify non-genetic and genetic factors that
correlate with OC-associated differences in plasma TFPI, PS and FIXa and thrombosis history. The data
collected in the longitudinal cohort will be used to examine the time course and stability of the OC-induced
plasma hypercoagulable state within individuals using repeated measures analysis. These findings will be used
to validate plasma protein changes and the effect of SNPs identified by GWAS in the cross-sectional cohorts.
The proposed experiments will define the biochemical and genetic underpinnings of the OC-induced hyper-
coaguable state focused on our finding of elevated amounts of an activated clotting factor, FIXa, in the plasma
of about 30% of women using OC. These results will also establish rationale for further clinical studies to define
the predictive value of plasma FIXa and associated genetic markers for OC-induced thrombosis and facilita...

## Key facts

- **NIH application ID:** 10120016
- **Project number:** 1R01HL149364-01A1
- **Recipient organization:** VERSITI BLOOD HEALTH, INC.
- **Principal Investigator:** Alan E Mast
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2021
- **Award amount:** $703,988
- **Award type:** 1
- **Project period:** 2021-08-01 → 2025-07-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10120016

## Citation

> US National Institutes of Health, RePORTER application 10120016, TFPI, Protein S, and Plasma FIXa in Hormone-Induced Hypercoagulability (1R01HL149364-01A1). Retrieved via AI Analytics 2026-05-24 from https://api.ai-analytics.org/grant/nih/10120016. Licensed CC0.

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