Stock-based compensation expense recognized for stock-based awards in the condensed consolidated statements of operations for the three months ended March 31, 2022 and 2021 was as follows (in thousands): (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2022	Mar. 31, 2021
Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Research and development	$ 13	$ 19
Research and Development Expense [Member]
Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Research and development	5	5
Clinical and regulatory
Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Research and development	3	9
General and Administrative Expense [Member]
Share-Based Payment Arrangement, Expensed and Capitalized, Amount [Line Items]
Research and development	$ 5	$ 5