Aetna - The health insurer and others including Cigna, Humana and Anthem rose after UnitedHealth Group posted better-than-expected fourth-quarter earnings.
Insperity - The human-resources outsourcing company soared after Starboard Value said it bought a 13.2 percent stake in the company.
ASML Holding - The semiconductor-production equipment gained after posting fourth-quarter results above estimates.
Illumina - The maker of DNA sequencing machines fell after President Barack Obama did not mention sequencing 1 million genomes as reported ahead of his State of the Union address Tuesday night.
TD Ameritrade Holding - The brokerage climbed after its quarterly earnings matched expectations.
Alynylam Pharmaceuticals - The drug developer dropped fell after pricing 4.7 million shares of common stock at $95 a piece.
BHP Billiton - The Australian miner rose after saying it would shutter 40 percent of its shale oil rigs in the United States.
Mosaic - The producer of phosphate fertilizer gained, a day after raising its fourth-quarter guidance.
(See CNBC's Market Insider Blog)
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