Blackstone will acquire Chartis from Audax Private Equity, according to a news release. Audax will remain invested in the company.

Chartis, founded in 2001 and based in Chicago, is a healthcare advisory firm with brands including Chartis, Jarrard, Greeley and HealthScape Advisors.

Blackstone (NYSE: BX), founded in 1985 and based in New York, is investing in Chartis through its core private equity strategy. The firm is one of the world’s largest alternative asset managers.

Audax, with private equity offices in Boston, New York and San Francisco, focuses on investments in middle market companies and has a wide flexibility on investment size. Founded in 1999, the firm targets companies within healthcare and several other industries, specifically those generating between $5 million and $80 million in annual EBITDA.

Terms of the transaction were not disclosed.