24/7 Wall St.

In what was a historic week for the stock markets, with all the big indexes hitting all-time highs, that didn’t stop insiders from stepping up to the plate to purchase more stock. For investors, aggressive insider buying at the top range of a secular bull market is just about the biggest confirmation that either good things are in the works earnings-wise, or something big could be a game-changing event for a company.

Insiders buying at market highs is huge, and it sends the message to investors that good things are still possible. While some add on a regular basis, others buy stock when they feel things are headed in the right direction. Either way, it is an extremely bullish sign — one our readers may want to take note of.

Here are this past week’s top insider buying reports.

Republic Services Inc. (NYSE: RSG) might as well take up permanent residence here on 24/7 Wall Street insider buying report. Once again, the private investment arm of Microsoft founder Bill Gates has hit the tape with another huge buy of the waste disposal company. In what can only be described as yet another mammoth purchase, the company bought 868,720 shares at prices ranging from $37.26 to $38.00. This cost Cascade a tidy $32.8 million. Republic shares were trading at $37.87 Thursday.

American Apparel Inc. (NYSE: APP) has been all over the news recently as the board ousted CEO Dov Charney and the stock has been plunging. In what seems to clearly be a bid to take over the struggling company, Charney and hedge fund Standard General bought 53,242,814 shares at $0.72 to $0.91 worth $39.4 million.

Charney entered a partnership with the investment firm, Standard General, late last week in an effort to claw his way back to the helm of the company he founded. But in striking a deal that gave him a 43% stake in American Apparel, Charney effectively ceded any authority that is not inextricably linked to Standard General’s approval. The stock was trading Thursday at $0.88.

ALSO READ: Key Stocks With Insider Selling This Week

Amicus Therapeutics Inc. (NASDAQ: FOLD) has been on fire, it also was in the news last week and a major owner really did some buying. Long/short biotech hedge fund Perceptive Advisors bought 4,000,000 shares at $3.49 to $3.50. That buy ticket cost the company a cool $14 million.

Amicus Therapeutics is a clinical-stage biopharmaceutical company that gained 10.2% after announcing that its final patient in a Phase 3 study (known as Study 012) had completed its 18-month treatment period, and that it was on track to deliver the results from its study involving migalastat as a monotherapy treatment for Fabry disease by the third quarter. It also made our list of stocks under $10 with huge upside potential. The stock was trading Thursday at $4.16.

Ladenburg Thalmann Financial Services Inc. (NYSE: LTS) had two directors, one of whom is a 10% owner, put some sizable buys on the tape. Together they purchased 360,000 shares at prices ranging from $3.15 to $3.46. The purchase came to $1.2 million, which represents some significant buying by company individuals. Ladenburg Thalmann, through its subsidiaries, provides brokerage and advisory, investment banking, equity research, institutional sales and trading, asset management, and trust services. The shares were trading Thursday at $3.50.

Accelerate Diagnostics Inc. (NASDAQ: AXDX) had a director and a 10% owner put in some large buy tickets for the stock. Between the two, they purchased 38,698 shares at prices ranging from $25.34 to $26.10. They spent $800,000 to pay for the stock buys as both added to their holdings. The stock was trading Thursday at $26.60.