In April 2017, the Company entered into a Controlled Equity Offering Sales Agreement (the “Sales Agreement”) with Cantor Fitzgerald & Co. (“Cantor”), as sales agent, pursuant to which the Company had the right to offer and sell, from time to time, through Cantor, shares of the Company’s common stock, par value $0.001 per share, by any method deemed to be an “at the market offering” as defined in Rule 415 under the Securities Act of 1933, as amended (the “Cantor ATM Offering”). In April 2017, the Company also filed a prospectus supplement (File No. 333-216977) with the SEC relating to the offer and sale of up to $20.0 million of common stock in the Cantor ATM Offering. In June 2017, the Company filed a first amendment to the prospectus supplement with the SEC to increase the amount of common stock that could be offered and sold in the Cantor ATM Offering under the Sales Agreement to $40.0 million in the aggregate, inclusive of the common stock previously sold in the Cantor ATM Offering prior to the date of the first amendment. In January 2018, the Company filed a second amendment to the prospectus supplement with the SEC to decrease the amount of common stock that could be offered and sold in the Cantor ATM Offering under the Sales Agreement to $23.0 million in the aggregate, inclusive of the common stock sold in the Cantor ATM Offering prior to the date of the second amendment. In February 2018, the Company and Cantor mutually agreed to terminate the Sales Agreement.

Prior to termination of the Sales Agreement, the Company sold 5,733,314 shares of common stock under the ATM Offering at then-market prices for total gross proceeds of approximately $21.1 million, including an aggregate of 261,352 shares of common stock sold for gross proceeds of $0.6 million during both the three and six months ended June 30, 2018. After $0.6 million of sales commissions and $0.2 million of other offering expenses paid by the Company in connection with the ATM Offering, the Company’s aggregate net proceeds from the ATM Offering were approximately $20.2 million. Sales commissions and offering expenses have been recorded as a reduction of proceeds received in arriving at the amount recorded in additional paid-in capital in the accompanying condensed consolidated balance sheets as of December 31, 2018.

In January 2018, the Company completed an underwritten public offering of 13,915,000 shares of its common stock at a price of $2.90 per share, including 1,815,000 shares sold pursuant to the exercise in full of the underwriters’ option to purchase additional shares. The Company sold its common stock through an underwriting agreement with Leerink Partners LLC and Cantor as representatives of the underwriters for the offering. The aggregate net proceeds to the Company from the offering were approximately $37.7 million, after deducting the underwriting discounts and commissions and offering expenses, for the year ended December 31, 2018.

In March 2019, the Company entered into a Controlled Equity Offering Sales Agreement (“Cowen Sales Agreement”) with Cowen and Company (“Cowen”), as sales agent, pursuant to which the Company has the right to offer and sell, from time to time, through Cowen, shares of the Company’s common stock, having an aggregate offering price of up to $40.0 million, by any method deemed to be an “at the market offering” as defined in Rule 415(a)(4) under the Securities Act of 1933, as amended (the “Cowen ATM Offering”) under the Company’s shelf registration statement on Form S-3 (File No. 333-229045). Approximately $0.2 million of costs incurred in connection with the offering were capitalized as deferred offering costs in the Company’s condensed consolidated balance sheets upon entry into this agreement.

As of September 30, 2019, no shares were sold under the Cowen ATM Offering and no shares will be sold under the Cowen ATM Offering as a result of the termination of the Cowen Sales Agreement in November 2019. As a result, the Company has written off approximately $0.1 million of the previously capitalized deferred offering costs as the Company will not utilize these costs in the sale of shares through the Cowen ATM Offering. The remaining $0.1 million of costs capitalized as deferred offering costs in the accompanying condensed consolidated balance sheets as of September 30, 2019 relate to the filing of the Form S-3 which are expected to be able to be utilized for a future ATM offering.

In September 2019, the Company entered into an underwriting agreement with Cantor Fitzgerald & Co. (the “2019 Underwriting Agreement”), relating to the issuance and sale in a public offering of 29,298,537 shares of its common stock, including 3,821,548 shares sold pursuant to the full exercise of the underwriter’s option to purchase additional shares. The price to the public in the offering was $0.65 per share and the underwriter agreed to purchase the shares from the Company pursuant to the 2019 Underwriting Agreement at a price of $0.611 per share. The net proceeds to the Company were approximately $17.7 million, after deducting the underwriting discounts and commissions and offering expenses.

The offering was made pursuant to the Company’s registration statement on Form S-3 (Registration Statement No. 333-229045), previously filed with the Securities and Exchange Commission (“SEC”) and declared effective by the SEC on February 11, 2019, and a prospectus supplement and accompanying prospectus thereunder.

In September 2019, concurrent with the closing of the September 2019 underwritten public offering, the Company entered into a Securities Purchase Agreement (the “Securities Purchase Agreement”) with certain institutional accredited investors (the “Purchasers”), pursuant to which the Company sold to the Purchasers, in a private placement transaction, an aggregate of 5,411,687 pre-funded warrants to purchase up to an aggregate of 5,411,687 shares of our common stock (“Warrant Shares”), at a price of $0.64 per warrant (which $0.64 price relates to the pre-funded portion of the total $0.65 exercise price per share). Each pre-funded warrant has a remaining exercise price of $0.01 per share and became immediately exercisable upon issuance, subject to certain beneficial ownership limitations.

The exercise price of the pre-funded warrants will be subject to adjustment in the event of any stock dividends and splits, recapitalization, reorganization or similar transaction, as described in the pre-funded warrants. The pre-funded warrants are exercisable on a “cashless” basis in certain circumstances.

The pre-funded warrants and the Warrant Shares were not registered under the Securities Act and were offered pursuant to the exemption provided in Section 4(a)(2) under the Securities Act and Rule 506(b) promulgated thereunder. The Company agreed to file a registration statement to register the resale of the Warrant Shares within 30 days following the date of the Closing and to obtain effectiveness of such registration statement within 90 days following the Closing, subject to certain exceptions. Each Purchaser was an “accredited investor” as defined in Rule 501(a) under the Securities Act.

Cantor Fitzgerald & Co. (the “Placement Agent”) acted as the sole placement agent in connection with the private placement of the warrants. Pursuant to a Placement Agency Agreement between us and the Placement Agent, we agreed to pay the Placement Agent a cash fee equal to 6% of the gross proceeds to us from the sale of the pre-funded warrants, and to provide reimbursement for certain out-of-pocket expenses. Upon closing, the Company received approximately $3.1 million in net proceeds from the sale of the pre-funded warrants in the private placement, which does not include proceeds that may be received upon exercise of the pre-funded warrants, after deducting the Placement Agent fee and other expenses.

A summary of the Company’s stock option activity for the nine months ended September 30, 2019 is as follows:

	Number of Shares			Weighted- Average Exercise Price Per Share		Weighted- Average Remaining Contractual Life (Years)		Aggregate Intrinsic Value
Balance at December 31, 2018		2,047,237		$	3.07		7.6	$	366,007
Granted		1,227,500			1.50
Exercised		(54,256	)		2.23			$	21,380
Forfeited		(62,946	)		3.26
Expired/Cancelled		(216,545	)		3.38
Balance at September 30, 2019		2,940,990		$	2.41		8.2	$	-
Exercisable at September 30, 2019		1,300,596		$	2.90		6.6	$	1,621

Stock option activity includes 35,000 and 80,000 inducement awards granted during the three and nine months ended September 30, 2019, respectively. As of September 2019, there was total unrecognized compensation expense of $2,137,036 related to unvested stock options, which the Company expects to recognize over a weighted-average period of approximately 2.53 years.

A summary of restricted stock unit (“RSU”) activity for the nine months ended September 30, 2019 is as follows:

	Number of Shares			Weighted- Average Grant Date Fair Value Per Share
Balance at December 31, 2018		227,707		$	3.39
Granted		77,500			1.93
Released		(58,128	)		3.30
Balance at September 30, 2019		247,079		$	2.95
Vested and unissued at September 30, 2019		15,001		$	3.26

Vested and unissued awards at September 30, 2019 represents RSU awards granted on August 16, 2018 for which the vesting date was September 30, 2019, but for which issuance of the awards occurred on the next business day, October 1, 2019. Unrecognized compensation expense related to the remaining unvested RSUs was $628,172 at September 30, 2019, which the Company expects to recognize over a weighted-average remaining service period of 2.47 years.

Stock-based compensation expense recorded in the accompanying condensed consolidated statements of operations for the three and nine months ended September 30, 2019 and 2018 was as follows:

	Three Months Ended September 30,				Nine Months Ended September 30,
	2019		2018		2019		2018
Selling, general and administrative	$	226,645	$	200,317	$	625,821	$	1,475,975
Research and development		74,652		41,553		181,336		121,651
Cost of product and product-related services revenue		15,258		16,105		37,976		45,727
	$	316,555	$	257,975	$	845,133	$	1,643,353

Stock-based compensation expense for the nine months ended September 30, 2018 included $1.0 million of selling, general and administrative compensation expense relating to the issuance of 259,551 shares under RSUs granted to the Company’s executive officers in January 2018 at a grant date fair value of $3.84 per share. The RSUs vested in full on January 29, 2018.