AstraZeneca has gained access to a class of drugs being developed by Ardelyx in a deal which could be worth over $270 million to the US biotech.

The Anglo-Swedish drugmaker has signed a worldwide exclusive licensing agreement for Ardelyx' NHE3 inhibitor programme. AstraZeneca notes that NHE3 is the sodium–hydrogen antiporter 3, a protein essential in the absorption of sodium in the intestines.

The lead compound in the programme is RDX5791, which has been evaluated in a Phase IIa trial in constipation-predominant irritable bowel syndrome and in two Phase I studies in healthy subjects for its ability to divert sodium absorption in the gastrointestinal tract. The drug is believed to decrease the absorption of dietary sodium and thus divert sodium excretion from urine to the faeces, "sparing the kidney and the cardiovascular system from unhealthy exposure of both sodium and fluid accumulation".

The companies plan to develop RDX5791 for use in end-stage renal disease and chronic kidney disease, in addition to IBS-C. They may also evaluate "possible development in other diseases that are a consequence of sodium and fluid overload".

Cashwise, AstraZeneca will pay $35 million upfront, plus $237.5 million in milestones related to launch and commercialisation, as well as tiered, double-digit royalties. It will pay development costs, while Ardelyx will conduct clinical trials in Phase II.

The latter firm also has an option to co-promote the product in the USA, "subject to agreed limitations". Gunnar Olsson, head of cardiovascular and gastrointestinal innovative medicines at AstraZeneca, said there is a significant unmet medical need to address the challenges caused by sodium and excess fluid in people with renal impairment. With a novel mechanism of action, "RDX5791 has the potential to have a major impact on how doctors treat these patients".

Mike Raab, Ardelyx chief executive, said that DX5791 "is our first clinical example of how our technology can be used to develop non-absorbed, small molecule therapeutics. We are delighted that AstraZeneca recognises the potential of this compound".