BloombergA Pfizer Inc. logo sits on a sign outside the companyPfizer Inc. agreed to buy Hospira Inc., a maker of injectable drugs and infusion technologies, for about $16 billion. Hospira HSP, -0.05% shareholders will receive $90 a share in cash, a 39% premium to Wednesday’s close. Pfizer PFE, -0.12% noted both sterile injectables and biosimilars are large and growing categories. The global marketplace value for generic sterile injectables is estimated to be $70 billion in 2020, while the marketplace for biosimilars is estimated to be about $20 billion by that time.. The companies tagged the enterprise value of the deal, which likely includes the assumption of debt, at about $17 billion. The deal is expected to immediately add to earnings upon closing. Pfizer last year made a $120 billion bid to buy AstraZeneca but was rebuffed. Pfizer Chief Executive Ian Read has said that the company remained open to doing a big deal. The drug maker, like its rivals, is dealing with billions lost in sales from drugs losing patent protection. An expanded version of this report appears at WSJ.com.