When insiders load up on their own shares, pay attention. Insiders usually buy their own shares for one reason only: They think the stock is cheap and has monster upside.

Alexion Pharmaceuticals Inc.

One biotechnology player that insiders are loading up on is Alexion Pharmaceuticals Inc. (ALXN - Get Report) , which develops and commercializes life-transforming therapeutic products.

Alexion Pharmaceuticals has a market cap of $27.19 billion. This stock trades at a reasonable valuation, with a forward price-to-earnings ratio of 18.4 times. Its estimated growth rate for this year is 14.9%, and for next year it's pegged at 23.7%. This is not a cash-rich company, since its total cash position is $1.46 billion and its total debt is $3.28 billion.

A director bought 2,009,734 shares, or $234.44 million worth of stock, at $114.33 to $117.95 per share.

If you're bullish on ALXN, I would look for long-biased trades if this stock is trending above key support at $113.22, and then once it breaks out above its 200-day at $122.93, with volume near or above its three-month average of 3 million shares. Some possible upside targets off that breakout are $130 to $133.67, or even $135 to $138 a share.

Meanwhile, Jim Cramer isn't buying Apple (AAPL) here, and says Facebook (FB) and Alphabet (GOOGL) look better on a dip.

Acorda Therapeutics Inc.

Another biotechnology player that insiders are active in is Acorda Therapeutics Inc. (ACOR - Get Report) , which identifies, develops, and commercializes therapies for neurological disorders in the U.S.

Acorda Therapeutics has a market cap of $862 million. This stock trades at a reasonable valuation, with a forward price-to-earnings of 13.9 times. Its estimated growth rate for this year is 692%, and for next year it's pegged at -47%. This is not a cash-rich company, since its total cash position is $133.62 million and its total debt is $327.12 million.

The CEO bought 20,000 shares, or $338,000 worth of stock, at $16.95 per share.

If you're bullish on ACOR, I would look for long-biased trades if this stock is trending above its 50-day at $16, and then once it breaks out above key resistance levels at $19 to its 200-day at $20.54, with volume near or above its three-month average of 1.14 million shares. Some possible upside targets off that breakout are $25 to $27 a share.

The Trade Desk Inc.

One technology player insiders are jumping into is The Trade Desk Inc. (TTD - Get Report) , which operates a self-service cloud-based platform that enables advertising buyers to create, manage and optimize data-driven digital advertising campaigns using their own teams.

The Trade Desk has a market cap of $2.08 billion. This stock trades at a fair valuation, with a forward price-to-earnings of 38.78 times. Its estimated growth rate for this year is 21.3%, and for next year it's pegged at 24.1%. This is a cash-rich company, since its total cash position is $106.57 million and its total debt is $25.85 million.

A director bought 20,000 shares, or $961,000 worth of stock, at $48.06 per share.

If you're in the bull camp on TTD, I would look for long-biased trades if this stock is trending above its 50-day at $45.90, and then once it breaks out above a key downtrend line over its 20-day at $52.58 and $54 with volume near or above its three-month average of 1.14 million shares. Some possible upside targets off that breakout are its 52-week high of $57.57 to $65 a share.

Akamai Technologies Inc.

Another technology player that insiders are in love with is Akamai Technologies Inc. (AKAM - Get Report) , which provides cloud services for delivering, optimizing and securing content and business applications over the internet.

Akamai Technologies has a market cap of $8.49 billion. This stock trades at a fair valuation, with a forward price-to-earnings of 17.11 times. Its estimated growth rate for this year is -5.2%, and for next year it's pegged at 12.1%. This is a cash-rich company, since its total cash position is $845.07 million and its total debt is $645.72 million.

The CEO bought 20,397 shares, or $999,000 worth of stock, at $49.02 per share.

If you're bullish on AKAM, I would look for long-biased trades if this stock is trending above its recent low of $46.81, and then once it breaks out above key resistance levels at $50.65 to its 50-day at $52.39 with volume near or above its three-month average of 2.62 million shares. If that breakout develops soon, this stock will set up to re-fill some of its previous gap-down-day zone from May that started near $62 a share.

The Williams Companies Inc.

My final stock with some decent insider buying is The Williams Companies Inc. (WMB - Get Report) , which operates as an energy infrastructure company primarily in the U.S.

The Williams Companies has a market cap of $23.43 billion. This stock trades at a fair valuation, with a forward price-to-earnings 28.64 times. Its estimated growth rate for this year is 270.2%, and for next year it's pegged at 2.1%. This is not a cash-rich company, since its total cash position is $639 million and its total debt is $21.82 billion.

The CEO bought 15,000 shares, or $429,000 worth of stock, at $28.60 per share.

If you're bullish on WMB, I would look for long-biased trades if this stock is trending above some near-term support at $27.11, and then once it breaks out above its 200-day at $29.15 to its 50-day at $29.59 and then over $29.69 with volume near or above its three-month average of 6.31 million shares. Some possible upside targets off that breakout are $31 to its 52-week high of $32.69, or even $35 a share.

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This article is commentary by an independent contributor. At the time of publication, the author held no positions in the stocks mentioned.