Google ( GOOG) shares shot up in late trading Thursday after Standard & Poor's said it will add the search-engine giant to its S&P 500 index. Google, which has been spurned by the S&P in earlier opportunities for addition to the index, will replace Burlington Resources ( BR) after the close of trading March 31. Google shares jumped $30.97, or 9%, to $372.86 in after-hours trading Thursday. Shares of Idenix Pharmaceuticals ( IDIX) plummeted in late trading after the company said it had lowered dosing levels in an ongoing clinical trial for the hepatitis C treatment valopicitabine after observing dose-related gastrointestinal side effects in patients. Idenix said the modifications will delay the drug's development, but the company noted that it was encouraged by the level of antiviral activity in the lower-dose arms. Shares fell $4.26, or 21%, to $15.99 in late trading. Palm ( PALM) shares rose after the gadget maker's fiscal third-quarter results and fourth-quarter guidance beat analysts' estimate. For the quarter ended Feb. 28, the company's earnings rose to $19.8 million, or 19 cents a share, up from $10.6 million, or 10 cents a share, a year earlier. Revenue rose to $388.5 million from $285.3 million. Analysts had forecast earnings of 16 cents a share and $374.7 million in revenue. For the current quarter, Palm forecast earnings of 22 cents to 23 cents a share, before items, on revenue of $400 million to $405 million. Analysts project earnings of 20 cents a share and revenue of $395 million. Shares advanced $1.17, or 5.8%, to $21.31 after hours. Synnex ( SNX) shares climbed after the IT supply-chain services company beat Wall Street's first-quarter earnings expectations and offered a solid guidance. Synnex reported earnings of $10.7 million, or 34 cents a share, up from $8.6 million, or 27 cents a share, a year ago. Excluding stock-compensation costs, the company earned $11.2 million, or 36 cents a share. Revenue increased to $1.50 billion from $1.31 billion. Analysts polled by Thomson First Call predicted earnings of 33 cents a share, before items, on revenue of $1.45 billion.