US STOCKS-Wall St up on GDP data; Twitter has biggest jump ever
* Twitter rallies after blockbuster results
* GDP shows more economic growth than expected in Q2
* Fed statement awaited, expected to trim monthly stimulus
* Biotechs rally on Amgen results, Regeneron trial data
* Indexes up: Dow 0.3 pct, S&P 0.4 pct, Nasdaq 0.7 pct (Updates to market open, adds analyst comment and Amgen results)
By Ryan Vlastelica
NEW YORK, July 30 (Reuters) - U.S. stocks were boosted Wednesday by some bullish earnings and a read on second-quarter economic growth that came in much stronger than expected, overshadowing a weak report on the labor market.
Gross domestic product grew at a 4 percent annual rate in the second quarter, above the 3 percent rate that had been expected and a sharp reversal from the weather-impacted first quarter, when the economy contracted a revised 2.1 percent.
Twitter Inc surged on heavy volume, jumping 25 percent to $48.25 in its biggest one-day advance ever after reporting that monthly active users had risen a better-than-expected 24 percent in the second quarter. The social networking company also gave a revenue forecast above forecasts. Continuación...