Stock index futures pointed to a higher open on Wednesday after forecast-beating results from Apple removed a weeks-old market overhang and lifted optimism in a corporate earnings season that is already far outstripping expectations.

Quarterly profit at Apple Inc almost doubled after a jump in iPhone sales. The stock, which dominates markets because of its size, had sold off recently, partly on fears earnings could disappoint.

Apple shares leaped 9.5 percent to $613.59 in premarket trade and could provide the catalyst to drive the market back to 2012 highs hit earlier this month.

It's another amazing quarter from Apple that is single handedly driving markets this morning, wrote Peter Boockvar, an equity strategist and portfolio manager at Miller Tabak in New York in a note.

The earnings season so far has been stronger than expected. With results from 153 S&P 500 companies, more than three-fourths have topped estimates, according to Thomson Reuters Proprietary Research as of Tuesday.

S&P 500 futures rose 8.2 points and were above fair value, a formula that evaluates pricing by taking into account interest rates, dividends and time to expiration on the contract. Dow Jones industrial average futures gained 42 points, and Nasdaq 100 futures added 52.5 points.

It has been a long time since I've seen one earnings report be so meaningful for the market, said Rick Meckler, president of investment firm LibertyView Capital Management of Apple's earnings.

The fact that they weren't the negative surprise that so many people feared will be a huge relief to this market and really could provide the impetus to bring it back to those previous highs.

The S&P 500 has fallen as much as 4.2 percent after running up about 30 percent from October to a 2012 peak in April. Fears about a resurgent debt crisis in Europe have been one of the main drivers of the pullback.

The cost to insure Spanish and Italian government debt against default fell as debt markets in the two countries looked more stable than in previous days, with traders citing buying from short-term investors.

In the latest economic data, durable goods orders for March fell 4.2 percent in the biggest decline in three years. Futures pared gains briefly but most of the losses were short-lived as investors focused on Apple.

This will create doubts about the strength of the recovery and reinforce the bears, said Jim Awad, managing director at Zephyr Management in New York. Today will be a tug-of-war between doubts about economic strength and good earnings.

The Federal Reserve will end a 2-day meeting later Wednesday. Fed officials may appear slightly more upbeat on the economy, but investors should not mistake cautious optimism for a desire to raise interest rates soon.

Also on the earnings front, Boeing Co posted higher quarterly profit and raised its earnings forecast for the year, sending the shares up 2.6 percent to $75.10 premarket.

Caterpillar Inc reported a 29 percent rise in profit. But its shares fell 1 percent to $107.36 after sales missed estimates.

Biotechnology company Amgen Inc will buy Turkey's Mustafa Nevzat Pharmaceuticals, a maker of injectable generic drugs, for about $700 million in a deal underscoring a thirst for emerging markets sales.

Amgen also posted better-than-expected profit late Tuesday and the biotechnology company bought back more of its shares. The shares rose 0.8 percent to $69.16.

In the latest merger, energy company Halcón Resources Corp said it will buy oil and gas driller GeoResources Inc for nearly $1 billion. GeoResources's shares rose 21.1 percent to $37.25 premarket.

Nearly half of Mexico's state prosecuting authorities said on Tuesday they had no immediate plans to investigate allegations of corruption by Walmex, the Mexican arm of Wal-Mart Stores Inc .

Shares of Wal-Mart have slumped 7.5 percent since the allegations were reported by the New York Times last weekend. Walmex shares have lost nearly 15 percent.

(Reporting by Ed Krudy; editing by Jeffrey Benkoe)