Chapel-Hill based Cempra co-founder and CEO Prabhavathi Fernades is retiring immediately and has been replaced by board member David Zaccardelli has been appointed acting CEO, the company said Monday. Baird analyst Brian Skorney suggested that her retirement could be due to “Surprisingly negative briefing documents disclosing saftey risks with its lead antibiotic drug in multiple clinical trials, reports the StreetInsider.com.

Fernades co–founded the antibiotic drug developer in 2006 and will remain a scientific consultant, but also leaves the company board.

Cempra (NASDAQ:CEMP) is a clinical-stage pharmaceutical company developing antibacterials to meet critical medical needs. Its antibiotic candidates include Solithromycin and Taksta.

“We founded Cempra with the goal of leading the development of new compounds that stand to address the critical unmet need for new antibiotic options, and it has been a privilege to lead and build Cempra alongside such tremendous colleagues and collaborators. Cempra is working to bring urgently needed new antibiotics, including solithromycin, to patients and physicians and I am excited about the future of the company under the leadership of Dr. David Zaccardelli and David Moore,” Fernandes said in a statement.

The company also named David Moore to the newly created position of president and chief commercial officer, effective immediately.

Zaccardelli is a seasoned industry leader with more than 25 years of experience including executive management and leadership across a wide range of pharmaceutical companies. From 2004 until 2016, Zaccardelli served in several senior management roles at United Therapeutics, which reported approximately $1.5 billion in revenues in 2015.

His roles included CEO, CMO, and executive vice president, pharmaceutical development and operations. Zaccardelli also founded and led a startup company focused on contract pharmaceutical development services, from 1997 through 2003. Zaccardelli worked at Burroughs Wellcome & Co. and Glaxo Wellcome, Inc. in a variety of clinical research positions from 1988 to 1996,

Prior to joining Cempra as chief commercial officer in 2014, Moore spent 14 years in commercial leadership roles at Johnson & Johnson’s Ortho-McNeil and Janssen Pharmaceutical divisions, where he developed and executed launch plans for several prescription pharmaceuticals for both primary and acute care settings.

Former Intersouth venture partner Garheng Kong, M.D., Ph.D, is chair of Cempra.

Shares of Cempra closed at $7.70 Monday.