Google sister company Calico and drug giant AbbVie are chipping in another $1 billion to cure aging, the companies said Tuesday.

Alphabet’s Calico and AbbVie first partnered in 2014 to combat age-related diseases, including cancers and neurodegenerative diseases. The additional contributions bring Calico’s total funding to $2.5 billion.

Aging is an attractive area in the biotechnology space as companies look for ways to ease the challenges that come with growing old. The Food and Drug Administration does not consider aging a disease, so some companies are tackling diseases associated with it rather than aging itself.

Together, AbbVie and Calico have produced more than two dozen early-stage programs focused on diseases in oncology and neurosciences.

Under the agreement, Calico is responsible for research and early development until 2022 and will be responsible for Phase 2a trials through 2027. After that, AbbVie will have the option to manage late-stage development. AbbVie will help lead commercialization efforts.