Consolidated Statements of Changes in Stockholders’ Equity (Deficit) - USD ($)
$ in Thousands
Total
Private Placement
Common stock
Common stock
Private Placement
Additional paid-in capital
Additional paid-in capital
Private Placement
Accumulated deficit
Accumulated other comprehensive loss
Beginning balance (in shares) at Dec. 31, 2018     22,471,776          
Beginning balance at Dec. 31, 2018 $ (5,418)   $ 3   $ 279,539   $ (280,403) $ (4,557)
Increase (Decrease) in Stockholders' Equity                
Issuance of common stock under Employee Stock Purchase Plan (in shares)     17,205          
Issuance of common stock under Employee Stock Purchase Plan 28       28      
Issuance of common stock upon exercise of options (in shares)     125,600          
Issuance of common stock upon exercise of options 150       150      
Issuance of vested restricted stock units (in shares)     93,750          
Issuance of vested restricted stock units 0              
Issuance of common stock, net of issuance costs (in shares)     22,188,706 3,178,174        
Issuance of common stock, net of issuance costs 30,942 $ 5,715 $ 2   30,940 $ 5,715    
Issuance of common stock through at-the-market offering, net (in shares)     615,453          
Issuance of common stock through at-the-market offering, net 1,006       1,006      
Issuance of common stock, pre-funded warrants and warrants through private placement (in shares)     37,634,883          
Issuance of common stock, pre-funded warrants and warrants through private placement 26,129   $ 4   26,125      
Stock-based compensation expense 5,161       5,161      
Currency translation adjustment 34             34
Unrealized loss on marketable securities 0              
Net loss (55,350)           (55,350)  
Ending balance (in shares) at Dec. 31, 2019     86,325,547          
Ending balance at Dec. 31, 2019 8,397   $ 9   348,664   (335,753) (4,523)
Increase (Decrease) in Stockholders' Equity                
Issuance of common stock under Employee Stock Purchase Plan (in shares)     110,212          
Issuance of common stock under Employee Stock Purchase Plan 184       184      
Issuance of common stock upon exercise of options (in shares)     76,128          
Issuance of common stock upon exercise of options 193       193      
Issuance of vested restricted stock units (in shares)     93,750          
Issuance of vested restricted stock units 0              
Issuance of common stock, net of issuance costs (in shares)       5,416,390        
Issuance of common stock, net of issuance costs   $ 10,268       $ 10,268    
Issuance of common stock through at-the-market offering, net (in shares)     1,069,486          
Issuance of common stock through at-the-market offering, net 2,108       2,108      
Issuance of common stock, pre-funded warrants and warrants through private placement (in shares)     8,342,128          
Issuance of common stock, pre-funded warrants and warrants through private placement 1   $ 1          
Issuance of common stock upon exercise of common warrants (in shares)     6,637,608          
Issuance of common stock upon exercise of warrants 24,263   $ 1   24,262      
Other financing fees (370)       (370)      
Issuance of common warrants with long-term debt, net 444       444      
Stock-based compensation expense 5,422       5,422      
Currency translation adjustment (40)             (40)
Unrealized loss on marketable securities 0              
Net loss $ (68,876)           (68,876)  
Ending balance (in shares) at Dec. 31, 2020 108,071,249   108,071,249          
Ending balance at Dec. 31, 2020 $ (18,006)   $ 11   391,175   (404,629) (4,563)
Increase (Decrease) in Stockholders' Equity                
Issuance of common stock under Employee Stock Purchase Plan (in shares)     58,794          
Issuance of common stock under Employee Stock Purchase Plan 161       161      
Issuance of common stock upon exercise of options (in shares)     447,492          
Issuance of common stock upon exercise of options 778       778      
Issuance of vested restricted stock units (in shares)     201,250          
Issuance of vested restricted stock units 0              
Issuance of common stock through at-the-market offering, net (in shares)     13,767,511          
Issuance of common stock through at-the-market offering, net 51,934   $ 1   51,933      
Issuance of common stock upon exercise of common warrants (in shares)     1,076,669          
Issuance of common stock upon exercise of warrants 5,624       5,624      
Stock-based compensation expense 7,720       7,720      
Currency translation adjustment (2)             (2)
Unrealized loss on marketable securities (1)             (1)
Net loss $ (25,687)           (25,687)  
Ending balance (in shares) at Dec. 31, 2021 123,622,965   123,622,965          
Ending balance at Dec. 31, 2021 $ 22,521   $ 12   $ 457,391   $ (430,316) $ (4,566)