The fact that Anthem wants to cut ties with Express Scripts is "perplexing," Express Scripts CEO Tim Wentworth told CNBC on Monday.
The pharmacy benefit manager announced on Monday its PBM contract with health-benefits company Anthem was unlikely to be extended after its expiration in late 2019.
"We've given them terrific service," Wentworth said in an interview with "Closing Bell."
"I would love nothing more than to find a way to keep Anthem as a client. We've offered them billions of dollars of rate relief for the next three years — price concessions, as it were — that they're not contractually entitled to."
Shares of Express Scripts fell more than 15 percent after the bell on Monday.
Last month, a federal judge dismissed two of the six counterclaims that Express Scripts raised in health insurer Anthem's $15 billion
Anthem had sued Express Scripts in March 2016, accusing it of excessive pricing and operational failures. It also sought the right to terminate its 10-year contract with Express Scripts.
Wentworth called the 2009 deal with Anthem "transformational" and noted that Anthem ultimately wound up with $4.7 billion up front that he said Anthem used to buy its stock back.
"We got them back in business in 2009, in their sanctioned CMS business. We delivered costs savings to them out of the shoot. They actually came up short in the short run in terms of delivering claims to us, and this deal actually didn't look terrific in the early years," he said.
He also brushed aside any notion that there may be more pressure from its other 2,900 clients, noting that the Anthem deal was different from all the others.
"Our 98 percent retention rate, 97.5 percent last year, proves that we're actually delivering for those clients," said Wentworth.
—Reuters contributed to this report.