Quarterly report pursuant to Section 13 or 15(d)

Basis of Presentation - Additional Information (Details)

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Basis of Presentation - Additional Information (Details) - USD ($)
 3 Months Ended 6 Months Ended 12 Months Ended
Oct. 07, 2022
Jun. 30, 2024
Jun. 30, 2023
Jun. 30, 2024
Jun. 30, 2023
Dec. 31, 2023
May 03, 2023
Oct. 17, 2022
Sep. 08, 2020
Jan. 21, 2020
Organization Consolidation And Presentation Of Financial Statements [Line Items]                    
Net losses   $ 4,997,000 $ 12,243,000 $ 12,098,000 $ 22,132,000 $ 38,371,000        
Accumulated deficit   473,396,000   473,396,000   461,298,000        
Cash and cash equivalents   $ 4,976,000   $ 4,976,000   $ 6,071,000        
Ordinary shares, par value   $ 0.01 $ 0.01 $ 0.01 $ 0.01 $ 0.01 $ 0.01      
Issuance of ordinary shares       1,700,000            
Additional ordinary shares with preemptive rights             60,000,000      
Maximum                    
Organization Consolidation And Presentation Of Financial Statements [Line Items]                    
Value of shares and securities may offer and sell               $ 100,000,000    
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                  
2025 Exchangeable Notes                    
Organization Consolidation And Presentation Of Financial Statements [Line Items]                    
Aggregate principal amount   $ 11,117,000   $ 11,117,000           $ 9,891,000
2025 Exchangeable Notes | Private Placement and Rights Offering                    
Organization Consolidation And Presentation Of Financial Statements [Line Items]                    
Aggregate principal amount                 $ 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