CONSOLIDATED STATEMENTS OF CASH FLOWS - USD ($)	6 Months Ended
	Jun. 30, 2020	Jun. 30, 2019
Cash flows from operating activities
Net loss	$ (4,865,561)	$ (4,871,050)
Adjustments to reconcile net loss to net cash used in operating activities:
Stock-based compensation expense	863,552	890,166
Amortization of held-to-maturity securities, net	229,919	90,785
Provision for contract losses	74,955	0
Foreign currency exchange loss (gain), net	50,204	10,966
Changes in operating assets and liabilities:
Interest receivable	103,576	(105,002)
Accounts receivable	32,112	(189,246)
Income tax receivable	0	506,866
Prepaid research and development	0	154,522
Prepaid expenses and other current assets	(321,533)	59,867
Accounts payable	154,484	665,126
Accrued expenses	(188,369)	(3,535)
Deferred research and development obligation	(37,268)	(50,430)
Net cash used in operating activities	(3,903,929)	(2,840,965)
Cash flows from investing activities
Purchases of held-to-maturity investment securities	(14,677,156)	(23,571,163)
Proceeds from maturities of investment securities	25,305,000	28,676,000
Net cash provided by investing activities	10,627,844	5,104,837
Cash flows from financing activities
Proceeds from exercise of options	230,743	149,180
Net cash provided by financing activities	230,743	149,180
Effect of exchange rate changes on cash	3,347	(17,846)
Net increase in cash and cash equivalents	6,958,005	2,395,206
Cash and cash equivalents at beginning of period	4,823,544	2,386,314
Cash and cash equivalents at end of period	11,781,549	4,781,520
Supplemental cash flow information
Cash received from income tax refund	$ 0	$ 506,866