Pfizer Inc. (NYSE:PFE) is in advanced talks to buy Global Blood Therapeutics, Inc. (NasdaqGS:GBT) the maker of a recently approved drug for sickle-cell disease, for about $5 billion, in the latest move by the drug giant to bolster its portfolio and pipeline. Pfizer is aiming to seal a deal for GBT in the coming days, according to people familiar with the matter. The situation is still fluid, and other suitors are still in the mix, some of the people said.

GBT announces its second-quarter results Monday. Bloomberg reported earlier this week that potential buyers were circling GBT, without naming them. The shares shot up on the news, adding to earlier gains since the spring.

They closed Thursday at $47.99, giving GBT a market value of just over $3 billion.