Trial design

A summary of the planned IUAT design, randomisation, treatment arms, endpoint hierarchy and follow-up schedule.

Study design

IUAT is planned as a prospective, multicentre, randomised, open-label, blinded-endpoint trial.

Design element	Planned approach
Allocation	1:1 randomisation
Trial type	Strategy trial comparing clipping with contemporary EVT
Blinding	Open-label treatment with independent blinded endpoint adjudication
Minimisation	By centre, aneurysm size and aneurysm location
Centres	15+ UK neurovascular centres with international expansion planned
Primary follow-up	12 months
Extended follow-up	2 years and 5 years for clinical and durability outcomes

Trial pathway

Treatment arms

Arm A: surgical clipping

Microsurgical clipping using established open vascular neurosurgical approaches. Intraoperative neuromonitoring and ICG video angiography are strongly recommended where available.

Arm B: contemporary endovascular treatment

The endovascular arm is a strategy arm. The MDT and treating operator select the optimal EVT modality within the allocated strategy.

Permitted endovascular techniques include:

• simple coiling
• balloon-assisted coiling
• stent-assisted coiling
• intrasaccular devices such as WEB, Contour, Artisse, Neqstent and Nautilus
• flow diversion such as Pipeline, Surpass, FRED, Derivo and SILK

Why a strategy trial matters

A trial limited to simple coiling would not reflect current practice. IUAT tests clipping against the full contemporary endovascular strategy used in modern neurovascular centres.