A potential merger between health insurers Cigna and Humana would create a powerhouse to rival UnitedHealth and CVS — but the deal is far from guaranteed from an antitrust perspective. Both parties have pursued selective divestitures in their respective insurance presences, but Cigna's stronghold in pharmacy benefit could raise regulators' hackles, industry watchers tell Axios. Cigna earlier this month was reportedly selling its Medicare Advantage unit, per Reuters — a move one health care banker tells Axios was likely a prelude to jumping on Humana. "It would leave us with three PBMs controlling the market with most of the market share," co-leader of the Healthcare practice, John Jones, tells Axios. "A big focus will be what impact it will have on costs," he adds. "These PBMs also administer the Medicare Part D benefit for Medicare so impact to the government and the elderly will also likely be evaluated."