LONDON and PARIS — AstraZeneca plans to acquire specialty pharmaceutical manufacturer Novexel in a deal worth up to $505 million.

The companies said Wednesday that under the agreement, AstraZeneca will acquire all of Novexel’s shares for $350 million in cash and pay up to an additional $75 million to Novexel shareholders if specified development milestones are reached. AstraZeneca will also transfer to Novexel shareholders an amount equivalent to the cash balance of Novexel at closing, expected to be about $80 million.

AstraZeneca, which has dual headquarters in London and Sweden, and Paris-based Novexel said the deal is slated to close in the first quarter of 2010.

With the acquisition, AstraZeneca stands to gain a portfolio of clinical and preclinical compounds designed to address infections caused by drug-resistant bacteria in the hospital.

Novexel’s clinical development pipeline includes NXL104, a novel beta-lactamase inhibitor, and NXL103, an oral Streptogramin antibiotic.

NXL104, in combination with the cephalosporin antibiotic ceftazidime (CAZ-104), is currently in two Phase II clinical trials in patients with complicated intra-abdominal infections and patients with complicated urinary tract infections, according to Novexel. Under an agreement January 2008, Novexel granted Forest Laboratories the rights to develop NXL104 in combination with ceftaroline (CEF-104) in North America.

NXL103 is now in a Phase II clinical trial in adults with acute bacterial skin and skin structure infections. The trial is designed to assess the safety and efficacy of NXL103 in comparison to oral linezolid, and NXL103 has already delivered positive Phase II results in a trial evaluating it in the treatment of community acquired pneumonia, Novexel reported.

In addition, Novexel has two other programs in preclinical development: NXL105, an anti-Pseudomonal antibiotic, and NXL201, an echinocandin antifungal agent.