* Raises 2018 adjusted profit forecast midpoint by 40 cents
* Expects Express Scripts deal to close by year-end
* Shares up 3.1 percent at $220.26 (Adds details from conference call, analyst quote, shares)
By Manas Mishra and Tamara Mathias
Nov 1 (Reuters) - U.S. health insurer Cigna Corp, which is in the process of acquiring Express Scripts Holding Co , significantly bumped up its 2018 adjusted profit forecast, and its shares rose more than 3 percent on Thursday.
The company beat Wall Street expectations for quarterly profit by 40 cents per share as it kept a tight rein on medical costs across its businesses, but the new 2018 forecast of $14.20 to $14.40 per share raises the midpoint from its prior outlook by 55 cents.
"The guidance raise in excess of the magnitude of the earnings beat this quarter signals Cigna's confidence in its industry-leading medical cost performance," Leerink analyst Ana Gupte said.
Cigna's $52 billion buy of pharmacy benefits manager Express Scripts is on track to close by the end of the year, after which the company expects to focus on paying down debt.
"Over the immediate term ... our capital priorities are quite clear. We're very well positioned ... to aggressively pay down our debt levels in the first 18 to 24 months," Chief Executive Officer David Cordani said on a conference call.
"As we look beyond that, we're going to have a tremendous capital flexibility," he added.
Cigna's Express Scripts deal, and CVS Health Corp's $69 billion acquisition of Cigna rival Aetna Inc signals a changing healthcare landscape as companies work to cut costs and brace for the threat of disruptive players such as Amazon.com Inc moving into the healthcare arena.
Cigna is banking on the Express Scripts deal to help lower client expenses and cushion the impact of increases in the cost of medical services.
In the third quarter, Cigna's commercial medical loss ratio - the amount it spends on medical claims compared to income from premiums in its biggest business - improved to 76.3 percent, from 78.6 percent a year earlier.
The consensus estimate was 77.4 percent, according to Evercore ISI.
Cigna, which mainly sells large and medium-sized corporate and international insurance, said the commercial business saw a 3 percent rise in membership to 15.8 million.
The company, which also provides government-backed Medicare plans, reported a near 38 percent net rise in income for shareholders to $772 million.
Excluding items, Cigna earned $3.84 per share, well above analysts' average estimate of $3.44, according to IBES data from Refinitiv.
Operating revenue rose 10.3 percent to $11.46 billion, beating estimate of $11.17 billion.
Cigna shares rose 3.1 percent at $220.26 in morning trading. (Reporting by Manas Mishra and Tamara Mathias in Bengaluru; Editing by Sriraj Kalluvila and Bill Berkrot)