Annual report pursuant to Section 13 and 15(d)

Quarterly Financial Data - Summary of Quarterly Financial Data (Detail)

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Quarterly Financial Data - Summary of Quarterly Financial Data (Detail) - USD ($)
$ / shares in Units, $ in Thousands
3 Months Ended 12 Months Ended
Dec. 31, 2019
Sep. 30, 2019
Jun. 30, 2019
Mar. 31, 2019
Dec. 31, 2018
Sep. 30, 2018
Jun. 30, 2018
Mar. 31, 2018
Dec. 31, 2019
Dec. 31, 2018
Dec. 31, 2017
Quarterly Financial Information Disclosure [Abstract]                      
Total revenues $ 526 $ 3,376 $ 10,791 $ 7,024 $ 7,409 $ 7,666 $ 8,774 $ 9,737 $ 21,717 $ 33,586 $ 35,377
Total operating expenses 3,371 6,759 11,619 11,974 11,414 12,324 13,331 14,794 33,723 51,863 52,927
Total other income 116 130 172 203 99 69 60 39 621 267 154
Net loss $ (2,729) $ (3,253) $ (656) $ (4,747) $ (3,906) $ (4,589) $ (4,497) $ (5,018) $ (11,385) $ (18,010) $ (17,396)
Net loss per share, basic and diluted $ (0.08) [1] $ (0.10) [1] $ (0.02) [1] $ (0.14) [1] $ (0.13) [1] $ (0.15) [1] $ (0.15) [1] $ (0.17) [1] $ (0.34) $ (0.59) $ (0.61)
[1] Net loss per share is computed independently for each quarter and the full year based upon respective shares outstanding; therefore, the sum of the quarterly net loss per share amounts may not equal the annual amounts reported.