Drug distributor McKesson Corp, San Francisco, will spend $575 million to buy Oncology Therapeutics Network, South San Francisco, in a deal that will integrate OTN’s oncology drug-distribution operations with its own growing operation.

Earlier this year, McKesson completed a $1.1 billion deal for Per Se  Technologies. McKesson said the OTN deal should be completed by the end of the year.

With annual sales of more than $3 million, OTN ranks as one of the nation’s largest distributors of cancer drugs.