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With the summer doldrums over, the stock market is starting to return to more normal conditions. This week finally saw the equity capital markets return from summer vacation and volumes start to pick up again. We also saw some very large insider selling in a top European pharmaceutical stock.

We track insider selling every week here at 24/7 Wall Street, and we like to remind our readers that just because insiders at companies are selling shares that is not an immediate red flag. Insiders will sell to diversify their investments, to do estate and tax planning and sometimes they just have a big purchase to make, like real estate.

Here is this past week’s top insider selling.

Mallinckrodt PLC (NYSE: MNK) is a huge pharmaceutical company based in Ireland, and it saw some very big insider selling this past week. Two directors of the company sold a total of 246,177 shares of stock, at prices that ranged from $83.76 to $85.23, for a total sale of $20.1 million. Mallinckrodt develops, manufactures, markets and distributes branded and generic specialty pharmaceuticals, active pharmaceutical ingredients and diagnostic imaging agents worldwide. The stock traded at $86.25 at Friday’s close.

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KapStone Paper and Packaging Corp. (NYSE: KS) had a top executive sell shares this week. The COO sold a sizable chunk of 350,000 shares of stock, at prices between $43.02 and $32.14, for a total sale of $11.2 million. KapStone is a favorite stock at the Hodges Fund, a successful growth mutual fund. KapStone shares ended Friday at $30.20.

SL Green Realty Corp. (NYSE: SLG) had a high-placed executive sell stock this past week. The chairman sold 95,439 shares at $109.10. The total sale came to $10.4 million. SL Green is New York City’s largest office landlord and is a fully integrated real estate investment trust (REIT) that is focused primarily on acquiring, managing and maximizing value of Manhattan commercial properties. Shares closed Friday at $103.98, so the chairman’s sale looks well timed.

Performant Financial Corp. (NASDAQ: PFMT) had a director sell a large amount of stock this past week. A total of 997,332 shares were shed at a price of $8.72, for a total amount of $8.7 million. Performant is a leading provider of technology-enabled recovery and related analytics services in the United States. Shares ended the week at $9.13.

Microsoft Corp. (NASDAQ: MSFT) is a major technology name that caught some insider selling this week. One of the senior vice presidents at the software giant sold a total of 57,618 share of the company stock at $45.05. The total of the sale came to $2.6 million. Microsoft has had an outstanding year, with shares up over 25%. They were changing hands at $46.70 on Friday’s close.

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Other companies that saw insider selling this week included: Atmel Corp. (NASDAQ: ATML), Ball Corp. (NYSE: BLL), XL Group PLC (NYSE: XL) and Chimerix Inc. (NASDAQ: CMRX).

Investors who own any of these stocks may want to check their holdings to see if they should also be moving to the exits. Again, insider selling is not necessarily bad, but it may be a good time to review the thesis for owning and the profit and loss ledger.