The following tables present changes in stockholders’ equity for the nine-month periods ended September 30, 2021 and 2020 (in thousands, except share data):


					Additional		Accumulated Other						Total
	Common				Paid-In		Comprehensive			Accumulated			Stockholders’
	Shares		Amount		Capital		Income (Loss)			Deficit			Equity
Balance at December 31, 2020		66,234,056	$	7	$	962,173	$	1		$	(435,109	)	$	527,072
Issuance of common stock through at-the-market offerings, net of issuance costs of $52		641,709		-		45,255		-			-			45,255
Exercise of stock options		1,014,569		-		13,340		-			-			13,340
Equity-based compensation		-		-		6,424		-			-			6,424
Other comprehensive loss		-		-		-		(13	)		-			(13	)
Net loss		-		-		-		-			(46,205	)		(46,205	)
Balance at March 31, 2021		67,890,334		7		1,027,192		(12	)		(481,314	)		545,873
Exercise of stock options		394,801		-		6,163		-			-			6,163
Vesting of restricted stock units		26,235		-		-		-			-			-
Issuance of shares under employee stock purchase plan		20,410		-		970		-			-			970
Equity-based compensation		-		-		10,614		-			-			10,614
Other comprehensive loss		-		-		-		(1	)		-			(1	)
Net loss		-		-		-		-			(68,806	)		(68,806	)
Balance at June 30, 2021		68,331,780		7		1,044,939		(13	)		(550,120	)		494,813
Issuance of common stock through follow-on offering, net of issuance costs of $284		4,758,620		-		648,315		-			-			648,315
Exercise of stock options		1,227,067		-		20,365		-			-			20,365
Vesting of restricted stock units		24,711		-		-		-			-			-
Equity-based compensation		-		-		15,410		-			-			15,410
Other comprehensive loss		-		-		-		(161	)		-			(161	)
Net loss		-		-		-		-			(71,644	)		(71,644	)
Balance at September 30, 2021		74,342,178	$	7	$	1,729,029	$	(174	)	$	(621,764	)	$	1,107,098

					Additional		Accumulated Other						Total
	Common				Paid-In		Comprehensive			Accumulated			Stockholders’
	Shares		Amount		Capital		Income			Deficit			Equity
Balance at December 31, 2019		50,198,044	$	5	$	570,493	$	261		$	(300,878	)	$	269,881
Issuance of common stock through at-the-market offerings, net of issuance costs of $48		351,252		-		5,079		-			-			5,079
Exercise of stock options		53,579		-		336		-			-			336
Equity-based compensation		-		-		4,157		-			-			4,157
Other comprehensive income		-		-		-		112			-			112
Net loss		-		-		-		-			(31,806	)		(31,806	)
Balance at March 31, 2020		50,602,875		5		580,065		373			(332,684	)		247,759
Issuance of common stock through follow-on offering, net of issuance costs of $369		6,301,370		1		107,731		-			-			107,732
Issuance of common stock in private placement with Regeneron		925,218		-		12,580		-			-			12,580
Issuance of common stock through at-the-market offerings, net of issuance costs of $23		755,848		-		9,643		-			-			9,643
Exercise of stock options		83,631		-		1,035		-			-			1,035
Issuance of shares under employee stock purchase plan		55,296		-		685		-			-			685
Equity-based compensation		-		-		4,764		-			-			4,764
Other comprehensive loss		-		-		-		(218	)		-			(218	)
Net loss		-		-		-		-			(32,393	)		(32,393	)
Balance at June 30, 2020		58,724,238		6		716,503		155			(365,077	)		351,587
Exercise of stock options		67,974		-		597		-			-			597
Equity-based compensation		-		-		5,400		-			-			5,400
Other comprehensive loss		-		-		-		(124	)		-			(124	)
Net loss		-		-		-		-			(27,840	)		(27,840	)
Balance at September 30, 2020		58,792,212	$	6	$	722,500	$	31		$	(392,917	)	$	329,620

On June 29, 2021, the Company entered into an underwriting agreement related to a public offering of 4,758,620 shares of its common stock (inclusive of shares sold pursuant to the exercise of the underwriters’ option to purchase additional shares) at a public offering price of $145.00 per share. The offering closed on July 2, 2021, for aggregated net proceeds of $648.3 million after deducting $41.7 million in underwriting discounts and offering costs.

In August 2019, the Company entered into an Open Market Sale Agreement (the “2019 Sales Agreement”) with Jefferies, under which Jefferies was able to offer and sell, from time to time in “at-the-market” offerings, common stock having aggregate gross proceeds of up to $150.0 million. The Company agreed to pay Jefferies cash commissions of 3.0% of the gross proceeds of sales of common stock under the 2019 Sales Agreement. Please refer to the Company’s Annual Report for the year ended December 31, 2020 for additional information regarding these offerings.

During the first half of 2021, the Company issued 641,709 shares of its common stock in a series of sales at an average price of $72.79 per share in accordance with the 2019 Sales Agreement, for aggregate net proceeds of $45.3 million after payment of cash commissions to Jefferies and approximately $0.1 million related to legal, accounting and other fees in connection with the sales. There was no activity under the 2019 Sales Agreement in the third quarter of 2021. During the nine months ended September 30, 2020, the Company issued 1,107,100 shares of its common stock in a series of sales at an average price of $13.78 per share in accordance with the 2019 Sales Agreement, for aggregate net proceeds of $14.7 million after payment of cash commissions to Jefferies and approximately $0.1 million related to legal, accounting and other fees in connection with the sales.

As of September 30, 2021, $47.4 million in shares of common stock remain eligible for sale under the 2019 Sales Agreement.