The firm announced it had agreed a deal with the board of California-based Anacor Pharmaceuticals.
Anacor's flagship product is crisaborole, a cream for eczema which is awaiting approval by US regulators.
The deal comes just weeks after Pfizer scrapped a planned $160bn merger with Irish drugmaker Allergan for tax reasons.
"We believe the acquisition of Anacor represents an attractive opportunity to address a significant unmet medical need for a large patient population," said Albert Bourla, head of Pfizer's global innovative pharma unit.
Crisaborole can achieve $2bn (£1.4bn) in annual sales if approved by the US Food and Drug Administration, according to Pfizer.
Some 18 million to 25 million people suffer from eczema in the US, but currently there are few safe appropriate treatments, Pfizer said.
Anacor shares jumped 57%, rising above the $99.25 a share agreed with Pfizer.
US drugs giant Pfizer will acquire the maker of a new eczema treatment in a deal worth $5.2bn (£3.6bn).