Biogen has ended a purchasing agreement it inked with Karyopharm Therapeutics in January 2018 for the company’s investigational amyotrophic lateral sclerosis (ALS) drug, KPT-350.

KPT-350 is a selective inhibitor of nuclear export (SINE) compound that can more easily cross the blood-brain barrier than other SINE compounds. It targets a protein involved in inflammation and has other neuroprotective properties.

Biogen initially paid $10 million and committed to potential milestone payments of $207 million. With the termination of the agreement, Karyopharm said it is no longer entitled to any milestone payments or royalties, but has regained rights to the purchased assets.

Karyopharm believes KPT-350 and related compounds could potentially treat a range of neurological and inflammatory conditions.