SFLT 1 APHERESIS reduced circulating soluble Fms like tyrosine kinase 1 levels and appeared safe and well tolerated in women with very preterm preeclampsia, according to findings from a single arm open label trial investigating a potential disease specific treatment approach.
sFlt 1 Apheresis in Very Preterm Preeclampsia
Soluble Fms like tyrosine kinase 1 is a placental protein that plays a central role in the pathogenesis of preeclampsia, a life-threatening pregnancy complication for which no disease specific therapies currently exist. Researchers developed an extracorporeal apheresis strategy using an adsorber containing high affinity IgG1 antibodies directed against soluble Fms like tyrosine kinase 1 to selectively remove the circulating protein.
In pregnant baboons, the intervention reduced circulating soluble Fms like tyrosine kinase 1 levels by approximately 50%. The approach was subsequently evaluated in women with very preterm preeclampsia, with primary endpoints focused on safety and tolerability.
Phase A included seven women treated with single ascending doses. Before apheresis, mean soluble Fms like tyrosine kinase 1 levels were 15,120±4,484 pg ml−1. Maternal and fetal vital signs, alongside umbilical artery pulsatility indices, remained stable before, during, and after treatment.
Blood Pressure and sFlt 1 Reductions Correlated
Phase B evaluated repeated dosing in nine women with very preterm preeclampsia. Median gestational age was 30.3 weeks: interquartile range, 29.3–30.9 weeks. Mean systolic and diastolic blood pressures before treatment were 146±10 mmHg and 92±5 mmHg, respectively. Preapheresis soluble Fms like tyrosine kinase 1 levels measured 11,960±3,056 pg ml−1.
Each apheresis session reduced circulating soluble Fms like tyrosine kinase 1 levels by 16.7±7.6% and mean arterial pressure by 4.1±7.8 mmHg. Investigators also identified a strong correlation between reductions in mean arterial pressure and reductions in circulating soluble Fms like tyrosine kinase 1 levels: R=0.63.
Pregnancy continuation from admission lasted a median of 10 days: range, 3–19 days. Neonatal birth weights generally remained stable or increased compared with antenatal estimated birth weights in pregnancies with the longest extensions.
Safety Findings Support Further Investigation
Treatment related adverse events were limited and included mild hypocalcaemia in three women, skin haemorrhage at the puncture site in one woman, and false labour in one woman. Overall, the data suggest that sFlt 1 apheresis may represent a feasible therapeutic strategy for women with very preterm preeclampsia.
The investigators concluded that controlled trials are now required to confirm the safety and efficacy of selective soluble Fms like tyrosine kinase 1 removal in this patient population.
Reference
Thadhani R et al. Targeted removal of soluble Fms-like tyrosine kinase 1 in very preterm preeclampsia: a pilot trial. Nature Medicine. 2026; https://doi.org/10.1038/s41591-026-04333-6.
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