* Irma further weakens to post-tropical cyclone
* Apple edges higher ahead of expected iPhone launch
* Sage Therapeutics slumps after drug fails in study
* Futures up: Dow 56 pts, S&P 4 pts, Nasdaq 14.25 pts (Adds details, comment, updates prices)
Sept 12 (Reuters) - Wall Street was set to open higher on Tuesday as Irma further weakened to a post-tropical cyclone, and ahead of the highly anticipated launch of the new iPhone.
The weakening of Irma, the second major natural disaster to hit the United States after Hurricane Harvey, allayed concerns about the severity of its financial impact.
"Investors have gained confidence that the worst is over and concerns over Irma's economic impact seem to have disappeared for the moment," said Andre Bakhos, managing director of Janlyn Capital in Bernardsville, New Jersey.
All eyes will be on Apple as it prepares to unveil the 10th anniversary edition of the iPhone, whose sales will also have repercussions on its many suppliers and rivals.
Apple shares were up 0.82 percent ahead of the event, scheduled to start at 1:00 p.m. ET (1700 GMT).
At 8:30 a.m. ET, Dow e-minis were up 56 points, or 0.25 percent, with 10,890 contracts changing hands.
S&P 500 e-minis were up 4 points, or 0.16 percent, with 157,376 contracts traded.
Nasdaq 100 e-minis were up 14.25 points, or 0.24 percent, on volume of 15,465 contracts.
The market also seemed to shrug off North Korea's threat that the United States would soon face the "greatest pain" it had ever experienced in the wake of the U.N. stepping up sanctions against Pyongyang on Monday due to its nuclear tests.
North Korea on Tuesday rejected the U.N. Security Council resolution, which imposed a ban on the country's textile exports and capped crude oil imports.
"Although North Korea is a threat and can make the market nervous because of uncertainty, more and more global powers are coming on board, taking the pressure off of just the U.S. dealing with it. About that, the investors feel good," Bakhos said.
All three major Wall Street indexes closed up more than 1 percent on Monday, with the S&P 500 ending at a record high, as concerns over Irma faded and North Korea did not, as some had feared, test-fire missiles over the weekend during its founders day celebrations.
Sage Therapeutics slumped more than 25 percent in premarket trading after its drug to treat a life-threatening seizure disorder failed in a late-stage trial.
Bunge fell about 5 percent after the agricultural commodities trader said it would buy a 70 percent stake in IOI Loders Croklaan for $946 million.
Teva rose 7.24 percent after the drugmaker agreed to sell its contraceptive brand, Paragard, for $1.1 billion to a unit of Cooper Cos, whose stock was flat.
In economic data, the Labor Department is expected to release its monthly job openings and labor turnover survey report for July at 10:00 a.m. ET. Job openings rose to 6.163 million in June. (Reporting by Sruthi Shankar in Bengaluru; Editing by Savio D'Souza)