Patrick Walsh has resigned his position as CEO of Wilmington-based AAIPharma Services Corp., the company announced.

AAIPharma and its affiliate, Cambridge Major Laboratories Inc., also announced in a news release Tuesday the appointment of Susan Nestegard as interim CEO.

Walsh said in a statement that he was asked to shepherd AAIPharma and Cambridge Major Labs through the first phase of the companies’ integration process after their merger in October.

“Now that the initial foundation, leadership team and process initiatives have been identified, it is time for me to step down,” he said in the release.

Walsh leaves a company that is dramatically different from the AAIPharma that declared bankruptcy in 2006 after selling its pharmaceutical division to Xanodyne.

Purchase in 2009 of the company’s profitable analytical and manufacturing unit – as well as the rights to the AAIPharma Services name – by Chicago-based equity firm Water Street Healthcare Partners was a turning point, Walsh said in an interview in February 2012. He said that the equity firm’s investment in the company, which allowed it to evolve from a division into a standalone company, went well beyond the purchase price.

“Water Street Healthcare Partners’ leadership and management structures consists of experienced CEOs and partners with strong track records in equity-backed investments,” he explained in the 2012 interview. “WSHP brings relevant management experience and a strong network of acquisition opportunities from its health care network. This allows us to pursue an internal and external growth strategy.”

Walsh joined AAIPharma in 2010, and helped strengthen the company’s leadership team with several new hires and promotions from within. During his tenure at the company, he and his team acquired Celsis Analytical Services and built a new 40,000-square-foot technology center adjacent to AAIPharma’s Wilmington headquarters.

Tuesday’s news release stated that Walsh also led the organization through its October merger with Cambridge Major Laboratories, which was financed by American Capital Ltd.

In an email Wednesday morning, Walsh said,"AAI is stronger today than it has ever been: more clients, higher revenue and one of the best reputations for reliability and quality in the contract service industry. In the last four years, the transformation of the company is truly a great American success story!

"I am very proud of the leadership team and employees who have led this fantastic company transformation and cultural shift. My role was to ensure this happened. Our private equity investors enjoyed one of their best returns on the sale of the company, so everyone (employees, clients, investors) benefited from the experience."

Walsh also said that his transition "allowed the board of directors plenty of advance notice of my resignation, so that there would be smooth and seamless transition. There is a retained search ongoing for my successor."

Walsh said in an email that his resignation has taken effect, but that he's available to the company during April. Nestegard, the interim CEO, will likely divide her time among the company's seven locations, including Wilmington, he added.

According to the news release, Nestegard serves on the boards of directors of American Capital as well as AAIPharma/Cambridge Major Laboratories. She is the former executive vice president and president, Global Healthcare, of Ecolab Inc. The release stated that Nestegard brings more than 30 years’ experience in health care and research and development to her new post.