US-based Ionis Pharmaceuticals has exclusively out-licensed its antisense drug inotersen and AKCEA-TTR-L to Akcea Therapeutics under an agreement potentially worth $1.7bn.

Inotersen is being developed to treat hereditary transthyretin amyloidosis (hATTR), a rare and fatal disease, while AKCEA-TTR-L is being developed for both hereditary and wild-type ATTR.

The partnership will combine Ionis’ commercial preparations with Akcea’s infrastructure and capabilities for the launch of inotersen in the US and EU, with approvals expected in mid-2018.

To support the launch, inotersen commercial team from Ionis will join Akcea, which will have global rights for the commercialisation of both inotersen and AKCEA-TTR-L.

Ionis Pharmaceuticals CEO and chairperson Stanley Crooke said: “This collaboration will allow the combined Ionis-Akcea team to rapidly deliver inotersen to the patients who desperately need this treatment.

“This collaboration will allow the combined Ionis-Akcea team to rapidly deliver inotersen to the patients who desperately need this treatment.”

“Our partnering discussions resulted in a number of options and we decided this partnership with Akcea will maximise the commercial value of inotersen and our TTR franchise.”

Akcea will pay Ionis an upfront licensing fee of $150m, and Ionis will invest $200m in Akcea to support inotersen commercialisation.

The US and EU regulatory approvals of inotersen and AKCEA-TTR-L will trigger milestone payments of $50m and $40m, respectively, to Ionis.

Under the terms of the agreement, 60% of commercial profits and losses from inotersen will be borne by Ionis and the remaining by Akcea. After the first commercial sales of AKCEA-TTR-L, the profits and losses for both the drugs will be shared equally between the companies.

The licence for the drugs further includes sales milestone payments of up to $1.3bn.

Subject to customary closing conditions, the transaction is scheduled to be completed in the second quarter of this year. After completion, Ionis’ stake in Akcea is set to increase from 68% to 75%.