Fitch Ratings downgraded Cigna to "BBB" from "A-" due to the health insurer's financing of up to $24 billion in new debt to buy Express Scripts.
The ratings agency also removed Cigna from rating watch negative and assigned the health insurer a stable outlook.
"While Fitch believes that the potential strategic benefits associated with the combination of these companies are significant, today's rating action reflects Fitch's concerns regarding the sharp rise in financial leverage," Fitch Ratings said.
Cigna and Express Scripts are expected to close their deal in the fourth quarter of 2018.
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