By Noel Randewich

SAN FRANCISCO (Reuters) - U.S. companies reacted on Wednesday with caution to businessman Donald Trump's victory in the U.S. presidential election and pointed to uncertainty over his lack of clear policy proposals.

A smattering of analyst conference calls held by companies reporting their quarterly results offered a glimpse of how they view the country's new path led by the former reality TV host.

Following campaign promises by Trump to renegotiate global trade agreements and make U.S. companies move factories back to the United States, over 1,100 manufacturers and businesses offered in an open letter on Wednesday to work with him.

"We will look for areas upon which we agree and can work productively with your new administration," said the letter, which was signed by companies including Caterpillar <CAT.N> and Boeing <BA.N>.

Magellan Health <MGLN.O>, a healthcare management company, noted in a call after its report that Trump promised to do away with President Barack Obama's signature Affordable Care Act.

"We think it will have an impact, clearly, on our business here," Chief Executive Barry Smith said. "We don't have any details of his proposals and the process by which they will be enacted, but we will hopefully know more in the coming weeks and months here."

HMS Holdings <HMSY.O>, another healthcare manager, also posted quarterly results above analysts' expectations but its stock slumped 17 percent.

"There hasn't been any real policy that we can react to at this point," HMS Holdings CEO Bill Luci said, addressing the election result.

Sucampo Pharmaceuticals <SCMP.O> jumped as much as 31 percent after the biopharmaceutical company raised its full-year sales forecast.

It was among several pharmaceutical companies rallying following months of promises by Democratic candidate Hillary Clinton to regulate drug prices.

"Obviously Hillary Clinton's agenda was much more well-articulated," said Chief Executive Officer Peter Greenleaf. "I will be interested to see what we learn as Mr. Trump takes office and we learn more about what his agenda is going to be for the industry."

In its quarterly call, EV Energy Partners LP <EVEP.O> said it and other oil and natural gas producers stand to benefit from reduced regulation under Trump.

"My concern, obviously, is Trump himself, whether or not he will be presidential and whether he can control his ego. My major concern, specifically, will be Mexico because it's such an important ally," said Executive Chairman John Walker.

Trump has vowed to build a wall on the U.S.-Mexico border to keep out immigrants.

(Reporting by Noel Randewich; editing by Grant McCool)