TRENTON, N.J. -- Drugmaker Pfizer Inc. is continuing its shopping spree with its fourth acquisition since the April collapse of its planned $160 billion megadeal to buy rival Allergan PLC and move its headquarters, on paper, to Allergan's base in lower-tax Ireland.

In its second deal this week, New York-based Pfizer said it's buying rights to Anglo-Swedish drugmaker AstraZeneca PLC's portfolio of approved and experimental antibiotic and antifungal pills, a move to boost Pfizer's business in one of its priority areas. The deal is valued in excess of $1.5 billion, including rights to sell the medicines in most countries outside the U.S., royalties and other payments.

The acquisition indicates a thawing of relations between the two companies barely two years after London-based AstraZeneca fought off Pfizer's hostile takeover attempt.

Pfizer had planned that $119 billion acquisition as a so-called "tax inversion" enabling Pfizer to slash its U.S. tax bill by moving its nominal headquarters -- but not its corporate offices or executives --to England.

The tax inversion strategy had been hot in corporate America for a few years, but it's cooled down since the U.S. Treasury Department in early April issued new tax rules to block the biggest U.S. drugmaker from becoming a corporate citizen of Ireland. Allergan is technically based in Dublin, but it's the result of a tax inversion merger and operates from Parsippany, New Jersey.

Under the deal announced Wednesday, AstraZeneca will receive an upfront payment of $550 million. Pfizer will get rights to some medicines in development and approved ones including Merrem, for treating bacterial meningitis and serious infections of the skin and stomach; Zinforo, for pneumonia and complex skin and soft tissue infections; and Zavicefta, a combination antibiotic the European Union just approved for treating serious bacterial infections.

Luke Miels, the head of the antibiotics business unit at AstraZeneca, said in a statement the company is "pleased that our strong science in antibiotics will continue to serve a critical public health need through Pfizer's dedicated focus on infectious diseases."

Pfizer's other recent deals include:

--On Monday, it announced a $14 billion deal to buy San Francisco-based Medivation, which develops pills for treating various cancers. That's a priority area, but Pfizer is playing catch-up with rivals dominating the new generation of targeted cancer medicines.

--On Aug. 1, Pfizer announced a deal worth $150 million upfront and potentially another $495 million to acquire what Pfizer didn't already own of Bamboo Therapeutics Inc. of Chapel Hill, North Carolina. It's is developing potentially lucrative gene therapies for rare diseases. Pfizer aims to become a leader in gene therapy.

--In June, Pfizer completed the $5.2 billion acquisition of Palo Alto, California-based Anacor Pharmaceuticals Inc., which could get a new eczema drug, crisaborole, approved by January. Pfizer also got topical toenail fungus treatment Kerydin and some other drugs in early testing.

In afternoon trading, Pfizer shares edged up 27 cents to $35.36. Investors seem to like Pfizer's return to focusing on deals to create new drugs, though. Since Pfizer scrapped the Allergan deal, its shares have jumped more than 12 per cent.