Consolidated Balance Sheets - USD ($)	Mar. 31, 2020	Dec. 31, 2019
Current assets:
Cash	$ 197,313,408	$ 219,966,167
Prepaid and other current assets	309,370	413,095
Total current assets	197,622,778	220,379,262
Equipment, net	34,518	30,623
Other assets	143,575	139,875
Total assets	197,800,871	220,549,760
Current liabilities:
Accounts payable	12,191,714	10,943,325
Accrued expenses and other current liabilities	9,339,721	10,949,128
Loan payable, current portion	4,568,432	2,602,292
Total current liabilities	26,099,867	24,494,745
Loan payable, long-term	15,544,138	17,332,626
Total liabilities	41,644,005	41,827,371
Stockholders' equity:
Preferred stock, $0.0001 par value per share (10,000,000 shares authorized, none issued and outstanding at March 31, 2020 and December 31, 2019, respectively)
Common stock, $0.0001 par value per share (150,000,000 shares authorized, 37,075,422 and 36,933,217 shares issued and outstanding at March 31, 2020 and December 31, 2019, respectively)	3,707	3,693
Additional paid-in capital	364,532,798	354,614,189
Accumulated deficit	(208,379,639)	(175,895,493)
Total stockholders' equity	156,156,866	178,722,389
Total liabilities and stockholders' equity	$ 197,800,871	$ 220,549,760