Shares of Chapel Hill-based Cempra sank more than 56 percent following news the US Food and Drug Administration (FDA) rejected its antibiotic for community-acquired bacterial pneumonia (CABP).

The drug, solithromycin, is a next-generation version of the antibiotic macrolides, which are prescribed for CABP. It derived from the drug Ketek, which was discontinued after it was linked to deadly liver problems.

The FDA said data on the drug’s effect on the liver and manufacturing issues were the reasons.

The agency specifically cited concerns about elevations in liver enzymes caused by the drug. Those effects were transient in Cempra trials and no acute liver injury occurred.

The FDA, however, said Cempra’s 920 patient database is too small to rule out the potential risk of liver injury and recommended an additional 9,000 patient study. In previous trials, the drug showed effectiveness against antibiotic resistant CABP.

A warning about potential liver damage would be required even if no problems show up in new trials.

It also wants a “comprehensive plan for post-marketing safety assessment.”

Cempra requested a meeting with the FDA as soon as possible and will update the agency on its alternate manufacturing plans.

Two days ago, (Dec. 27), the Law Offices of Vincent Wong announced that a class action lawsuit has been commenced in the USDC for the Middle District of North Carolina on behalf of investors who purchased Cempra, Inc. (NASDAQ:CEMP) securities between October 22, 2015 and November 1, 2016.

According to the complaint, during the Class Period, Cempra made false and/or misleading statements and/or failed to disclose that: (i) Cempra’s lead product candidate solithromycin posed significant safety risks for hepatotoxicity; and as a result of the foregoing, Cempra’s public statements were materially false and misleading at all relevant times.

Cempra stock (CEMP:Nasdaq) sold at $2.60 a share, down more than 56 percent during mid-morning trading Thursday.