Role of Endothelin-A (ETA) and Endothelin-B (ETB) Receptors in the Vasodilatory Response to Endothelin-3 (ET-3)

What Was Tested

This registered early phase 1 trial tested Endothelin-1.

Endothelin-1 (ET-1) has been linked to a number of conditions including pulmonary arterial hypertension (PAH).

ET-1 acts via 2 receptors, ETA and ETB.

It had three arms (groups): Bosentan (experimental), Sitaxsentan (experimental) and Placebo (placebo comparator).

Placebo tablet twice daily will be taken for 7 days, before ET-1 plasma sample taken. ET-3 infusion (5mins) and associated forearm blood flow study (60 mins) will also occur after 7 days of placebo therapy.

The registry classes the interventions as biological and drug.

Who Took Part

10 planned participants were the target.

It was open to people of any sex aged from 18 years up to 70 years.

Healthy volunteers could join, not only people with the condition.

Examples of who could join: Healthy men and post-menopausal women. Age 18-70 years. BMI 18-35 kg/m2.

The full record lists 3 inclusion and 8 exclusion criteria; among the exclusions: are mentally or legally incapacitated; have donated blood within the last 4 weeks; have a history of past or present drug or alcohol abuse.

How the Study Was Run

It was run as a randomized, crossover and triple-blind study.

Because people in this Endothelin-1 study were split into groups at random, differences between the groups are less likely to reflect who happened to join each one.

In the crossover set-up each of the participants took both Endothelin-1 and the comparison in turn, acting as their own control.

Neither the participants nor the staff measuring them knew who was on Endothelin-1, so expectations could not easily colour the readings.

Those kept unaware of assignments: participant, care provider and investigator.

It started in 2009-01 with completion listed for 2009-09.

It ran at 1 site in United Kingdom.

Its stated primary purpose is basic science.

What Was Measured

Researchers chose this as the main measure: Plasma ET-1 after 7-day administration of bosentan, sitaxsentan and placebo (time frame: 7 days). Responses to ET-3 (maximum vasodilation after ET-3 administration and area under the curve of vasodilation) after bosentan compared with the results from sitaxsentan and placebo (time frame: 60 mins).

What This Means in Plain Language

Put simply, this is a early phase 1, randomized trial of Endothelin-1 in 10 people.

Its size is small, so on its own it can only give an early look.

The trial is marked completed; no results are posted to the registry yet, so nothing here describes outcomes.

More context: the Endothelin-1 compound page, all human trials.