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Stephen A. Cohen, the founder and owner of SAC Capital Advisors LLC, has been charged by the U.S. Securities and Exchange Commission (SEC) with “failing reasonably to supervise two of his senior employees, who engaged in insider trading under his watch.” Cohen has 20 days to respond.

The SEC charges include details of trades in shares in Elan Corp. plc (NYSE: ELN), Wyeth — now part of Pfizer Inc. (NYSE: PFE) — , and Dell Inc. (NASDAQ: DELL). The two SAC employees, Mathew Martoma and Michael Steinberg, have already been charged by the SEC with insider trading.

The SEC contends that Cohen “received highly suspicious information” upon which he should have taken “prompt action” to determine if his employees had engaged in “unlawful conduct” and that Cohen should have taken action “to prevent violations of federal securities laws.

SAC Capital has said that Cohen acted appropriately and that he would vigorously defend himself against the charges.