US-based Vertex Pharmaceuticals has signed an agreement to acquire CTP-656, an investigational cystic fibrosis transmembrane conductance regulator (CFTR) potentiator from Concert Pharmaceuticals for up to $250m.

CTP-656 can be used as part of future once-daily combination regimens of CFTR modulators that treat the underlying cause of cystic fibrosis (CF).

Vertex Pharmaceuticals executive vice-president and chief medical officer Dr Jeffrey Chodakewitz said: "Our vision is to develop the most effective and convenient medicines for people with CF.

"We look forward to exploring once-daily regimens that combine CTP-656 with other potential medicines from our broad CF pipeline that treat the underlying cause of the disease."

As part of the agreement, Vertex will pay $160m to Concert for all development and commercialisation rights to CTP-656 globally.

If it is approved as part of a combination regimen to treat CF, Concert may receive up to another $90m based on regulatory approval in the US and reimbursement in the UK, Germany or France.

Concert developed CTP-656 by applying deuterium chemistry to modify Vertex's CFTR potentiator, ivacaftor, which is approved in the US, Europe, Canada and Australia for people with CF.

At present, Concert is conducting a Phase II study of CTP-656 in people with CF who have gating mutations.

CF is caused by a defective or missing CFTR protein resulting from mutations in the CFTR gene. 

The rare, life-threatening genetic disease CF affects about 75,000 people in North America, Europe and Australia.