Quarterly report pursuant to Section 13 or 15(d)

Basis of Presentation - Additional Information (Details)

v3.23.2
Basis of Presentation - Additional Information (Details) - USD ($)
$ / shares in Units, shares in Millions
 3 Months Ended 6 Months Ended 12 Months Ended
Oct. 07, 2022
Jun. 30, 2023
Jun. 30, 2022
Jun. 30, 2023
Jun. 30, 2022
Dec. 31, 2022
May 03, 2023
Oct. 17, 2022
Aug. 17, 2022
Sep. 08, 2020
Jan. 21, 2020
Organization Consolidation And Presentation Of Financial Statements [Line Items]                      
Net losses   $ 12,243,000 $ 6,735,000 $ 22,132,000 $ 10,235,000 $ 44,434,000          
Accumulated deficit   445,059,000   445,059,000   422,927,000          
Cash and cash equivalents   13,734,000   13,734,000   $ 21,092,000          
Short-term investments   $ 30,998,000   $ 30,998,000              
Description of reverse share split       The Company's shareholders approved a reverse share split of the Company's ordinary shares on June 15, 2022, which became effective on August 17, 2022, (the Reverse Share Split). As of 5:00 p.m. Eastern Standard Time on August 17, 2022, every fifteen ordinary shares of $0.01 each (nominal value) in the authorized and unissued and authorized and issued share capital of the Company were consolidated into one ordinary share of $0.15 each (nominal value), and the nominal value of each ordinary share was subsequently reduced from $0.15 to $0.01 nominal value per share              
Ordinary shares, par value   $ 0.01 $ 0.01 $ 0.01 $ 0.01 $ 0.01 $ 0.01   $ 0.01    
Reverse share split previous nominal value                 0.15    
Maximum                      
Organization Consolidation And Presentation Of Financial Statements [Line Items]                      
Number of shares and securities may offer and sell               100.0      
Sales Agreement With H.C. Wainwright & Co., L.L.C                      
Organization Consolidation And Presentation Of Financial Statements [Line Items]                      
Ordinary shares, par value $ 0.01                    
Sales Agreement With H.C. Wainwright & Co., L.L.C | Maximum                      
Organization Consolidation And Presentation Of Financial Statements [Line Items]                      
May offer and sell ordinary shares for aggregate gross sales proceeds $ 16,000,000.0                    
0.01 Nominal Value                      
Organization Consolidation And Presentation Of Financial Statements [Line Items]                      
Ordinary shares, par value                 0.01    
0.15 Nominal Value                      
Organization Consolidation And Presentation Of Financial Statements [Line Items]                      
Ordinary shares, par value                 $ 0.15    
2025 Exchangeable Notes                      
Organization Consolidation And Presentation Of Financial Statements [Line Items]                      
Aggregate principal amount                     $ 9,891,000
2025 Exchangeable Notes | Private Placement and Rights Offering                      
Organization Consolidation And Presentation Of Financial Statements [Line Items]                      
Aggregate principal amount                   $ 220,000 $ 51,800,000
Debt instrument interest rate                     6.50%
RLNs | Private Placement and Rights Offering                      
Organization Consolidation And Presentation Of Financial Statements [Line Items]                      
Aggregate principal amount                   $ 500 $ 100,000