There's never a shortage of losers in the stock market. Let's take a closer look at five of this past week's biggest sinkers.

Company

May 2

Weekly Loss

Endocyte (NASDAQ: ECYT)

$6.62

63%

Gogo (GOGO 0.69%)

$13.42

26%

Capstone Turbine (CPST)

$1.70

23%

Ballard Power Systems (BLDP -2.76%)

$3.57

14%

Coach (TPR -1.60%)

$43.88

12%

Source: Barron's.

Let's start with Endocyte. The biotech shed nearly two thirds of its value after a once potentially promising treatment for platinum-resistant ovarian cancer was shot down. The data safety monitoring board halted a late-stage trial for Endocyte's Vintafolide, illustrating the problem of buying into biotechnology companies riding on the approval of a single drug. 

Gogo ran into some turbulence after being blindsided by an announcement of future competition. Gogo has become synonymous with providing leading airlines with in-flight Internet connections for passengers. The excitement turned into concern when Ma Bell and a leading avionics company announced that they would team up to offer a rival platform by the end of next year. 

Capstone shares slipped after selling 18.825 million shares of common stock to a single institutional investors. The maker of co-generation turbines that run on many different fuel types sold its freshly minted shares at $1.70, a discount to its price of $2.06 at the time. The market doesn't like dilution, even if Capstone stands to collect $30.2 million in proceeds. 

Ballard Power ran out of fuel after posting disappointing financial results. Revenue climbed 13% to $14 million for the fuel cell specialist, just shy of the $15.3 million that Wall Street was expecting. Despite coming up short, Ballard Power did manage to stick to its guidance calling for 30% in top-line growth and breaking even when it comes to adjusted EBITDA. In other words, revenue growth should accelerate from here. Ballard Power wound up giving up all of the prior week's gains that resulted from acquiring hundreds of patents and applications covering transportation and stationary fuel-cell technology. 

Finally we have Coach failing to make a winning play. The luxury handbag maker continues to lose market share in the premium categories it once dominated. Revenue slipped 7% in its latest quarter with a crushing 18% drop in North American sales. Earnings did come in ahead of Wall Street profit targets, but that's not much of a consolation when shoppers think Coach is no longer cool. Citigroup downgraded the stock on the uninspiring financials.