Political interest in the PBMbusiness model has transitioned into a full-fledged effort by theTrump administration to change it. (Photo: Shutterstock)

Cigna Corp. has successfully dodged two giant obstacles in itsattempt to purchase pharmacy-benefit managerExpress Scripts Holding Co. First, it got past Carl Icahn, whotried to convince investors to vote no on the deal inAugust, only to drop the effort days later after giving it furtherthought. And on Monday afternoon, it won clearance from theDepartment of Justice to go ahead with the transaction.

But the hardest part lies ahead. This is a period of massive uncertainty for the PBM business, andCigna is paying $54 billion for the pleasure of having to navigateit.

Related: CVS defends PBMs as Aetna dealprogresses

Even when the deal was announced in March, PBMs — whichnegotiate drug prices on behalf of employers and health plans —were under substantial public scrutiny, accused of using theirmiddlemen status to encourage and profit from ever-higher drugprices. And Amazon.com Inc. was casting its disruptive eye on the health-carebusiness.

Since then? Amazon's theoretical interest has become real. Ithired legendary Harvard surgeon Atul Gawande to run its high-profile employeehealth-cost containment joint venture, and confirmed its directinterest in the drug market with its purchase of online pharmacystartup PillPack.

Political interest in the PBM business model has transitionedinto a full-fledged effort by the Trump administration to changeit. It's working on a rule that may make the drug rebates that PBMsnegotiate — the primary service they provide and a major source ofprofit — substantially less lucrative.

The administration doesn't seem to be messing around. In aninterview with Bloomberg News on Sept. 12, Health and HumanServices Secretary Alex Azar said he was targeting “disruptive”change to the current system with an aim toward making it moretransparent.

Amazon, meanwhile, may have an advantage in a simpler and lessopaque drug management system. It's pretty good at getting thingsfrom point A to point B as cheaply as possible, and has a massiveroster of people that use its services every day.

To succeed in a world in which the model that made ExpressScripts a profitable PBM giant no longer works, Cigna will have tofigure out a new approach. That will likely mean accepting that itsPBM arm will be less of a profit center in its own right, and thatit must become a value-focused complement to its insurance business— one focused more on cost-effectiveness than the relentless huntfor the biggest possible rebate.

It won't be an easy shift, but it's essential if this merger isgoing to succeed.

How close is the drug-distribution industry to majordisruption? Take a look:

• How Amazon pharmacy could save the healthcare industry $100 billion yearly
• Pfizer CEO predicts an end to drugrebates
• Middlemen play gatekeeper in battle to curbdrug costs

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Max Nisen is a Bloomberg Opinion columnistcovering biotech, pharma and health care. He previously wrote aboutmanagement and corporate strategy for Quartz and Business Insider.This column does not necessarily reflect the opinion of theeditorial board or Bloomberg LP and its owners.