Ionis Pharmaceuticals Inc. has licensed its experimental Alzheimer's disease therapy IONIS-MAPTrx to Biogen Inc.

Ionis earned $45 million from the licensing fee, with the possibility of receiving an additional $155 million in milestone payments, according to a Dec. 19 press release. Ionis, which develops RNA-targeted therapeutics, will also be eligible to receive future royalty payments in the low- to mid-teens based on sales of the medicine.

The agreement continues the companies' partnership in developing treatments for neurological disorders.

IONIS-MAPTrx is an antisense therapy that is designed to reduce the production of what is called microtubule-associated protein tau in the central nervous system. Microtubule-associated protein tau is thought to contribute or be the cause of multiple neurodegenerative diseases, including Alzheimer's disease and some forms of frontotemporal degeneration, according to Ionis.

Carlsbad, Calif.-based Ionis will be responsible for a current phase 1 clinical study of IONIS-MAPTrx in patients with mild Alzheimer's disease, which began in 2017. The company will also be responsible for a one-year long-term extension study that began in 2019.

Biogen will be responsible for any future studies of IONIS-MAPTrx and any further development, including regulatory filings and commercialization of the medicine, according to the press release.