By Hester Plumridge 

LONDON-- AstraZeneca PLC has agreed to buy the rights to a portfolio of inhaled drugs from Almirall SA in a deal worth up to $2.1 billion, a significant step toward expanding its respiratory business and the type of pipeline-boosting deal favored by Chief Executive Pascal Soriot.

The deal will give the U.K. drug maker a type of treatment for chronic obstructive pulmonary disease which it currently lacks, a new type of inhaler and a portfolio of pipeline drugs, potentially helping it compete better with rivals such as respiratory-market leader GlaxoSmithKline PLC.

AstraZeneca's asthma treatment Symbicort has been gaining market share in the U.S. from Glaxo's best-selling drug, Advair.

The Almirall deal will also shore up AstraZeneca's revenue, which is forecast to decline between now and 2017. The company hopes a raft of new drugs--including a number of promising cancer treatments--will hit the market by that time.

However, the deal doubles up on a number of pipeline drugs that AstraZeneca acquired through its 2013 purchase of Pearl Therapeutics.

"We see a significant overlap with the recently acquired Pearl's assets, which could raise questions about AstraZeneca's strategy in respiratory, " Morgan Stanley said in a research note.

AstraZeneca said it would pay the Spanish drug maker an initial consideration of $875 million and up to a further $1.22 billion in development, launch and sales-related milestones and payments. That values the portfolio around 2.6 times revenue, Panmure Gordon said in a note.

For Almirall, the deal marks a surprising exit from respiratory drugs, its single largest unit, responsible for just under a third of total sales.

It removes the risk of delays to U.S. approval of one of Almirall's combination drugs, Barclays said in a note. Shares in the Spanish company, which has a market capitalization around $2.5 billion, rose 9% Wednesday. After the transaction, Almirall will be heavily dependent on its dermatology assets

The key marketed drug being acquired by AstraZeneca in the deal is Eklira, a long-acting muscarinic agonist--a type of drug that reverses airway obstruction.

AstraZeneca will also secure the rights to drugs in development and a subsidiary of Almirall devoted to the development of new inhaler devices.

Inhaler technologies are crucial to the delivery of respiratory drugs, allowing drugs to reach the airways in the right condition and combination.

For AstraZeneca, the deal adds to a string of acquisitions Mr. Soriot has made recently to bolster the company's revenue and drug pipeline. Since taking over in late 2012, Mr. Soriot has signed six such deals worth around $4.2 billion, including assets in oncology, respiratory and cardiovascular diseases.

In May, AstraZeneca fended off a $120 billion takeover approach from Pfizer Inc. , saying it undervalued the company. Mr. Soriot is now considering ways to maximize AstraZeneca's valuation, including potentially finding a partner to market its cancer drugs, exploring deals for its noncore neuroscience and anti-infective drugs, and signing deals to boost its pipeline.

AstraZeneca expects the acquisition, which it plans to finance through existing cash resources and short-term debt, to boost earnings starting in 2016.

"Our agreement with Almirall brings strategic and long-term value to AstraZeneca's strong respiratory franchise, one of our key growth platforms," Mr. Soriot said.

Shares in AstraZeneca rose around 1% to 4,360 pence in morning trading Wednesday.

Jana Simmons contributed to this article.

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