Exhibit 12.1

COMPUTATION OF RATIO OF EARNINGS TO FIXED CHARGES

The following table
sets forth our ratio of earnings to fixed charges for each of the periods indicated (in thousands):



|                                                   |      |                         |         |      |  |   |         |   |  |      |         |   |      |   |         |   |  |   |         |  
|-------------------------------------------------- | ---- | ----------------------- | ------- | ---- |  | - | ------- | - |  | ---- | ------- | - | ---- | - | ------- | - |  | - | ------- | -
|                                                   |      | Year Ended December 31, |        
|                                                   | 2010 |                         |         | 2009 |  |   | 2008    |   |  | 2007 |         |   | 2006 |  
|Earnings:                                          |      |                         |         |      |  |   |         |   |  |      |         |   |      |   |         |   |  |   |         |  
|Net loss                                           |      | $                       | (22,898 | )    |  | $ | (30,288 | ) |  | $    | (43,907 | ) |      | $ | (24,339 | ) |  | $ | (33,327 | )
|Fixed charges                                      |      |                         | 805     |      |  |   | 934     |   |  |      | 1,636   |   |      |   | 3,456   |   |  |   | 4,496   |  
|                                                   |      |                         |         |      |  |   |         |   |  |      |         |   |      |   |         |   |  |   |         |  
|Total Earnings                                     |      | $                       | (22,093 | )    |  | $ | (29,354 | ) |  | $    | (42,271 | ) |      | $ | (20,883 | ) |  | $ | (28,831 | )
|                                                   |      |                         |         |      |  |   |         |   |  |      |         |   |      |   |         |   |  |   |         |  
|Fixed Charges:                                     |      |                         |         |      |  |   |         |   |  |      |         |   |      |   |         |   |  |   |         |  
|Interest expense                                   |      | $                       | 6       |      |  | $ | 36      |   |  | $    | 789     |   |      | $ | 2,625   |   |  | $ | 3,436   |  
|Portion of rent expense representative of interest |      |                         | 799     |      |  |   | 898     |   |  |      | 847     |   |      |   | 831     |   |  |   | 1,060   |  
|                                                   |      |                         |         |      |  |   |         |   |  |      |         |   |      |   |         |   |  |   |         |  
|Total Fixed Charges                                |      | $                       | 805     |      |  | $ | 934     |   |  | $    | 1,636   |   |      | $ | 3,456   |   |  | $ | 4,496   |  
|                                                   |      |                         |         |      |  |   |         |   |  |      |         |   |      |   |         |   |  |   |         |  
|Ratio of Earnings to Fixed Charges(1)              |      |                         |        |      |  |   |        |   |  |      |        |   |      |   |        |   |  |   |        |  



|(1) | For purposes of computing the ratio of earnings to fixed charges, earnings consist of net loss plus fixed charges. Fixed charges consist of interest expense,
amortization of debt expense and discount or premium related to indebtedness, whether expensed or capitalized, and that portion of rental payments under operating leases we believe to be representative of interest. Earnings were insufficient to
cover fixed charges for these periods. The amount of the coverage deficiency was $22,898, $30,288, $43,907, $24,339, and $33,327 for the years ended December 31, 2010, 2009, 2008, 2007 and 2006, respectively.
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