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

March 28

Weekly Loss

Exelixis (NASDAQ:EXEL)

$3.38

46%

MannKind (NASDAQ:56400P706)

$4.83

18%

Rally Software (UNKNOWN:RALY.DL)

$13.69

16%

Kandi Technologies (NASDAQ:KNDI)

$16.14

15%

Organovo (NASDAQ:ONVO)

$7.41

12%

Source: Barron's.

Let's start with Exelixis. The biotech shed nearly half of its value after a critical study of its cabozantinib in treating metastatic castration-resistant prostate cancer fell short of expectations. A more diversified biotech could withstand a hit like this, but a lot of the value in Exelixis was based on the the efficacy of this single drug.

MannKind investors and needle-weary diabetes sufferers are hoping that an inhaled insulin can improve their situations. However, an FDA staff review is raising concerns about MannKind's Afrezza. The treatment's impact on lung function is just one of the many concerns that may hold Afrezza back, and investors decided to take one not-so-small step back on MannKind.

Rally Software continued to sell off after posting disappointing quarterly results a week earlier. The provider of cloud-based solutions for managing Agile software development may have posted a narrower deficit than analysts were targeting, but its guidance was uninspiring. 

Kandi slumped after Jim Cramer passed on the opportunity to offer a bullish perspective. The stock came up during Mad Money's Lightning Round on Monday, but Cramer countered that he preferred a larger stateside maker of off-road vehicles. Naturally Kandi bulls will argue that the comments miss the mark. Kandi's appeal has been in the electric cars that it's now working on and growing participation in Chinese auto-sharing offerings.   

Organovo stumbled despite presenting at the 2nd Annual Regen Med Investor Day on Wednesday. Organovo has a great story to tell. It's toiling away on 3-D proxies of human tissues that could be used for medical research and therapeutic applications. The stock's been volatile, and even after this past week's sell-off it has still nearly tripled since the start of last year.