Tom Thornton, the leader of the Kansas Bioscience Authority, which is under investigation and been criticized by Gov. Sam Brownback, has resigned.

The announcement Friday came from KBA board chairman John Carlin.

David Vranicar, who has been president of the KBA’s commercialization arm, was named interim president and chief executive officer of the KBA.

“The state can be rightfully proud of the organization Tom helped build,” Carlin, a former governor, saidin a prepared statement.

“He assembled and guided a stellar team of professionals who represent an innovative, independent agency that is envied by many other states across the nation. Tom will remain in contact, which will be helpful to us in the transition process. We are grateful for his service and wish him well in his future endeavors,” Carlin said.

Thornton has led the economic development agency since 2006.

This year, he came under fire from state Sen. Susan Wagle, R-Wichita, who complained about Thornton’s $265,000 salary.

Wagle, chair of the Senate Commerce Committee, also alleged that Thornton had conflicts of interest. KBA officials said her accusations were based on incorrect information.

Wagle also revealed that the Johnson County District Attorney’s Office had launched an investigation into KBA. KBA officials have said they don’t know what the investigation is about and the District Attorney’s Office has refused to comment.

Brownback had called on the KBA to conduct a forensic audit of its operation. Carlin announced last week that the agency would do that.

On Friday, Wagle said Thornton’s resignation “resolves only one of the problems my committee has been addressing.”

She declined to provide more details, saying there was a criminal investigation going on.

“There is clearly a problem within the agency,” she said. “We have a lot more questions.”

Her Commerce Committee is scheduled to continue meetings on the KBA when the Legislature returns to session on April 27.

In his resignation letter to board chairman Carlin, Thornton said “The KBA is hailed across the country as a model for bioscience development and the envy of other states.”

Thornton reviewed some of the KBA’s accomplishments, including helping secure the $650 million National Bio and Agro-Defense Facility, which will be built in Manhattan. He said Kansas has become positioned as an international leader in animal health research, while gaining national recognition in drug and bio-energy research.

He did not give a reason for his resignation and ended the letter with the state’s motto: “Ad astra per aspera,” which means to the stars through difficulties.

The KBA was formed in 2004 and Thornton was its first president and CEO.