Below is a three month price history chart comparing the stock performance of ARNA vs.

FORBES: Arena Pharmaceuticals Larger Than S&P 500 Component Advanced Micro Devices

At the closing bell, ARNA is up about 6.2%, while AMD is trading flat on the day Friday.

FORBES: Arena Pharmaceuticals Larger Than S&P 500 Component Advanced Micro Devices

Arena Pharmaceuticals (NASDAQ:ARNA ) received FDA approval for Lorcaserin that also treats obesity.

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The company has been in a race to develop an FDA-approved obesity drug, with rivals Arena Pharmaceuticals (ARNA) and Orexigen (OREX).

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Merck's entry in the HDL wars, developed with San Diego-based Arena Pharmaceuticals (nasdaq: ARNA - news - people ), are working on a modified niacin that does not cause flushing.

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Among the largest underlying components of XBI, in trading today Arena Pharmaceuticals Inc ( NASD: ARNA) is off about 4.9%, Pharmacyclics, Inc. ( NASD: PCYC) is down about 4.2%, and Onyx Pharmaceuticals, Inc. ( NASD: ONXX) is lower by about 0.5%.

FORBES: Noteworthy ETF Inflows: XBI, ARNA, PCYC, ONXX

Among the largest underlying components of XBI, in trading today Arena Pharmaceuticals Inc ( NASD: ARNA) is up about 0.5%, Onyx Pharmaceuticals, Inc. ( NASD: ONXX) is off about 0.1%, and Pharmacyclics, Inc. ( NASD: PCYC) is lower by about 2.5%.

FORBES: Noteworthy ETF Outflows: XBI, ARNA, ONXX, PCYC