Swiss drugmaker Novartis, opens new tab on Friday agreed ​to buy a breast cancer drug candidate for up ‌to $3 billion from U.S. biotech firm Synnovation Therapeutics, adding a targeted therapy to its pipeline of cancer drugs.

The company will pay $2 ​billion upfront and up to $1 billion that is contingent ​on further development achievements as part of the ⁠deal.

The experimental drug, SNV4818, belongs to a class of selective PI3Kα ​inhibitors, a new approach for the treatment of a type ​of breast cancer known as HR positive/HER2 negative and potentially other solid tumours.

The acquisition adds to a growing pipeline of targeted cancer ​therapies, including a radioligand therapy candidate, that Novartis is ​already testing. SNV4818 is currently in early‑stage trials and has shown promising ‌activity ⁠against tumors in lab studies, Novartis said.

Synnovation's drug targets only the mutated form of PI3Kα, an enzyme that often malfunctions in breast and other forms of cancer, while sparing ​the normal ​version found in ⁠healthy cells. And it aims to avoid the side effects seen with existing PI3Kα-inhibiting ​therapies.

"While mutated PI3Kα is a well‑established driver ​in HR+/HER2‑ ⁠breast cancer, there remains a challenge in achieving effective pathway inhibition with a tolerable therapeutic profile," said Shreeram Aradhye, the ⁠drugmaker's ​chief medical officer.

Novartis expects the deal ​to close in the first half of this year.