The incident happened on the Burn Road between Parkgate and Doagh on Monday 18th September.
The collision, which was reported to police at around 8.30 pm on Monday night, involved a white Vauxhall Astra van, a red Volvo V70 and a black Vauxhall Corsa.
Further enquiries by officers at the scene have led to a possible line of enquiry that a further vehicle may have been involved but did not remain at the scene.
An 18 year old man was taken to hospital following the collision to be treated for what is described as life changing injuries.
The road was closed for a number of hours but has since re-opened.
Police would appeal to anyone who was on the Burn Road on Monday evening and who noticed any of these cars travelling in the area or anyone with any information which could assist officers with their enquiries to contact them in Antrim on 101 quoting reference number 1434 18/09/17.