Equity	6 Months Ended
Jun. 30, 2018
Equity [Abstract]
Equity	Note 4 - Equity Series B/B-1 Convertible Preferred Stock: On July 20, 2016, the Company entered into a securities purchase agreement with an institutional investor for an offering of shares of convertible preferred stock and warrants with gross proceeds of approximately $3.5 million in a registered direct offering. The Series B issued under the securities purchase agreement was exchanged for Series B-1 Convertible Preferred Stock on October 30, 2016. The Series B-1 Convertible Preferred Stock was non-voting and was convertible into shares of common stock at the holder’s election at any time. Approximately $1.6 million of the proceeds were allocated to the preferred stock, representing the residual proceeds after the warrants were recorded at fair value (see below.) As of June 30, 2018, and December 31, 2017, all Series B/B-1-Convertible Preferred Stock had been converted into common stock and none were outstanding. Series C and D Convertible Preferred Stock: On October 30, 2016, the Company entered into a securities purchase agreement with an institutional investor for shares of convertible preferred stock and warrants with an aggregate purchase price of $3.8 million in a registered direct offering and simultaneous private placement. The first closing of the transaction occurred on November 3, 2016, whereby the Company received $3.6 million in gross proceeds and the second closing occurred on January 10, 2017, whereby the Company received gross proceeds of $0.2 million. The Series C and D Convertible Preferred Stock issued in the transaction included a contingent beneficial conversion amount of $1.3 million and $0.5 million, respectively, representing the intrinsic value of the shares at the time of issuance. This amount is reflected as an increase to the loss per share allocable to common stockholders in the six-month period ended June 30, 2017 when the contingency for the conversion was resolved with the shareholder approval allowing for the conversion of the preferred stock into common stock. As of June 30, 2018, and December 31, 2017, all shares of the Series C and D Convertible Preferred Stock had been converted into common stock and none were outstanding. Series E Convertible Preferred Stock: On April 24, 2017, the Company closed on an underwritten public offering of common stock, Series E Convertible Preferred Stock, and warrants to purchase shares of common stock for gross proceeds of $9.2 million, which included the full exercise of the underwriter’s over-allotment option to purchase additional shares and warrants. Net proceeds totaled approximately $8.0 million after deducting the underwriting discounts and commissions and other costs associated with the offering. As of June 30, 2018, and December 31, 2017, all shares of the Series E Convertible Preferred Stock had been converted into common stock and none were outstanding. Series F Convertible Preferred Stock: On November 27, 2017, the Company closed on an underwritten public offering of Series F Convertible Preferred Stock (“Series F preferred stock”) and warrants to purchase shares of common stock for gross proceeds of $18.0 million. Net proceeds totaled approximately $16.2 million after deducting the underwriting discounts and commissions and other costs associated with the offering. The offering was comprised of Series F preferred stock, convertible into shares of the Company’s common stock at a conversion price of $4.50 per share. Each share of Series F preferred stock was accompanied by a Series 1 warrant, which expires on the first anniversary of its issuance, to purchase 223 shares of the Company’s common stock at an exercise price of $4.50 per share, and a Series 2 warrant, which expires on the seventh anniversary of its issuance, to purchase 223 shares of the Company’s common stock at an exercise price of $4.50 per share. The Series F preferred stock and the warrants were immediately separable and were issued separately. The conversion price of the Series F preferred stock will be adjusted in the event of a stock split, combination, reclassification or stock dividend or if the Company consummates a fundamental transaction. The Series F preferred stock also has full ratchet price based anti-dilution protection, subject to customary carve outs, in the event of a down-round financing at a price per share below the conversion price of the Series F preferred stock (which protection will expire if, during any 20 of 30 consecutive trading days, the volume weighted average price of the Company’s common stock exceeds 300% of the then-effective conversion price of the Series F preferred stock and the daily dollar trading volume for each trading day during such period exceeds $200,000) (See Note 9 – Subsequent Events). The exercise price of the warrants is fixed and does not contain any variable pricing features, nor any price based anti-dilutive features, apart from customary adjustments for stock splits, combinations, reclassifications, stock dividends or fundamental transactions. A total of 18,000 shares of Series F Convertible Preferred Stock convertible into approximately 4.0 million shares of common stock and warrants to purchase approximately 8.0 million shares of common stock were issued in the offering. The Series F Convertible Preferred Stock included a beneficial conversion amount of $8.7 million, representing the intrinsic value of the shares at the time of issuance. As of June 30, 2018 and December 31, 2017, 17,390 and 14,220 shares of the Series F Convertible Preferred Stock had been converted into an aggregate of 3,877,970 and 3,171,060 shares of common stock and 610 and 3,780 remained outstanding, respectively. Placement Agent Fees: In connection with the issuance of the Series B, C and D Convertible Preferred Shares, the Company paid the placement agent an aggregate cash placement fee equal to 6% of the aggregate gross proceeds raised in the offering and issued warrants as described below. In connection with the issuance of the Series E and F Convertible Preferred Shares, the Company provided underwriting discounts and commissions of 9% and 8%, respectively, of the aggregate gross proceeds raised in the offering to the underwriter, and issued no warrants to the underwriter in such transactions. Investor Warrants: In connection with the issuance of the Series B Convertible Preferred Stock in July 2016, the Company issued the investor, at no additional cost, warrants to purchase 6,149 shares of common stock at an exercise price of $564 per share. The warrants were exercisable for 36 months commencing six months from the closing date and were subject to a reduction of the exercise price if the Company subsequently issued common stock or equivalents at an effective price less than the current exercise price of such warrants. Concurrently with the closing of the Series C and D Convertible Preferred Stock and warrant financing on November 3, 2016, the exercise price for these warrants was adjusted to $102 per share. In connection with the issuance of the Series C and D Convertible Preferred Stock in November 2016, the Company issued the investor, at no additional cost, warrants to purchase 35,295 shares of common stock at an exercise price of $108 per share. In connection with the issuance of the Series D Convertible Preferred Stock at the second closing in January 2017, the Company issued the investor, at no additional cost, warrants to purchase 1,961 shares of common stock at an exercise price of $108 per share. The warrants were exercisable for 60 months commencing on the earlier of the day of the receipt of approval of the Company’s stockholders of a proposal to approve the issuance of the shares of common stock underlying the warrants, or the six-month anniversary of the date of issuance. These warrants were subject to a reduction of the exercise price if the Company subsequently issued common stock or equivalents at an effective price less than the current exercise price of such warrants. Warrant Exercise Agreement: On February 15, 2017, the Company entered into a letter agreement with the institutional investors that held the majority of its outstanding warrants (the ‘‘Original Warrants’’), to incent the cash exercise of the investor warrants described above on or before March 31, 2017. In exchange for any such exercise, the Company agreed to provide the investors a replacement warrant (the ‘‘Replacement Warrants’’) to purchase the same number of shares of common stock as were issued upon exercise of the Original Warrants, with an exercise price equal to the consolidated closing bid price of its common stock on the date of issuance. The Replacement Warrants were issued in the same form as the Original Warrants except the exercise prices are not subject to reduction for subsequent equity issuances and the Replacement Warrants do not allow the investor to demand that the Company purchase the Replacement Warrants in the event of a fundamental transaction involving the Company. In connection with this agreement, between February and March 2017, the investors exercised all of the Original Warrants for gross cash proceeds to the Company of $2.0 million, and the Company issued 43,396 Replacement Warrants with exercise prices ranging from $34.6 per share to $99.8 per share. The Company entered into the letter agreement with the investors to incent the exercise of the Original Warrants in order to receive the cash proceeds from the exercise of the Original Warrants and because the exercise of the Original Warrants would allow the Company to remove the warrant liability from its balance sheet and avoid future fair value adjustments and associated volatility in its consolidated financial statements, as the Replacement Warrants are not accounted for as liabilities based on their terms. As of June 30, 2018, and December 31, 2017, there were no Original Warrants outstanding and all Replacement Warrants under the letter agreement had been issued. Placement Agent Warrant: In connection with the issuance of the Series B, C and D Convertible Preferred Stock, the Company issued warrants to the placement agent to purchase an aggregate of 2,605 shares of common stock at exercise prices ranging from $126.0 per share to $810.0 per share. These warrants were issued at no additional cost, were exercisable immediately, and expire five years from the closing of each offering. These warrants do not contain repricing provisions. Warrant Valuation: Both the Original Warrants and placement agent warrants were accounted for as liabilities and were recorded at fair value on the date of issuance. These warrants must be measured and recorded at fair value for each subsequent reporting period that the warrants remain outstanding, and any changes in fair value must be recognized in the consolidated statement of operations. In connection with the warrant exchange agreement described above, the Company remeasured each Original Warrant as of the date of exercise and recorded $1.4 million for the change in fair value of these warrants as an unrealized gain in the accompanying consolidated statement of operations for the six-month period ended June 30, 2017. The Replacement Warrants were valued at $0.5 million using the Black Scholes valuation model with the following assumptions: an expected dividend yield of 0%, expected stock price volatility of 49.65%-50.38%, risk-free interest rates of 1.95%-1.97% and an expected life of 5 years. The warrants have a five-year life and were fully vested at the date of grant. The terms of these warrants do not require them to be accounted for as liabilities and are therefore recorded in equity. As in incentive to early exercise the Original Warrants, the fair value provided to investors through the Replacement Warrants exceeded the fair value of the Original Warrants that was relinquished by the warrant holders by approximately $0.1 million, which has been reflected as an expense in the statement of operations for the six-month period ending June 30, 2017.

Note 4 - Equity

Series B/B-1 Convertible Preferred Stock: On July 20, 2016, the Company entered into a securities purchase agreement with an institutional investor for an offering of shares of convertible preferred stock and warrants with gross proceeds of approximately $3.5 million in a registered direct offering. The Series B issued under the securities purchase agreement was exchanged for Series B-1 Convertible Preferred Stock on October 30, 2016. The Series B-1 Convertible Preferred Stock was non-voting and was convertible into shares of common stock at the holder’s election at any time. Approximately $1.6 million of the proceeds were allocated to the preferred stock, representing the residual proceeds after the warrants were recorded at fair value (see below.) As of June 30, 2018, and December 31, 2017, all Series B/B-1-Convertible Preferred Stock had been converted into common stock and none were outstanding.

Series C and D Convertible Preferred Stock: On October 30, 2016, the Company entered into a securities purchase agreement with an institutional investor for shares of convertible preferred stock and warrants with an aggregate purchase price of $3.8 million in a registered direct offering and simultaneous private placement. The first closing of the transaction occurred on November 3, 2016, whereby the Company received $3.6 million in gross proceeds and the second closing occurred on January 10, 2017, whereby the Company received gross proceeds of $0.2 million. The Series C and D Convertible Preferred Stock issued in the transaction included a contingent beneficial conversion amount of $1.3 million and $0.5 million, respectively, representing the intrinsic value of the shares at the time of issuance. This amount is reflected as an increase to the loss per share allocable to common stockholders in the six-month period ended June 30, 2017 when the contingency for the conversion was resolved with the shareholder approval allowing for the conversion of the preferred stock into common stock. As of June 30, 2018, and December 31, 2017, all shares of the Series C and D Convertible Preferred Stock had been converted into common stock and none were outstanding.

Series E Convertible Preferred Stock: On April 24, 2017, the Company closed on an underwritten public offering of common stock, Series E Convertible Preferred Stock, and warrants to purchase shares of common stock for gross proceeds of $9.2 million, which included the full exercise of the underwriter’s over-allotment option to purchase additional shares and warrants. Net proceeds totaled approximately $8.0 million after deducting the underwriting discounts and commissions and other costs associated with the offering. As of June 30, 2018, and December 31, 2017, all shares of the Series E Convertible Preferred Stock had been converted into common stock and none were outstanding.

Series F Convertible Preferred Stock: On November 27, 2017, the Company closed on an underwritten public offering of Series F Convertible Preferred Stock (“Series F preferred stock”) and warrants to purchase shares of common stock for gross proceeds of $18.0 million. Net proceeds totaled approximately $16.2 million after deducting the underwriting discounts and commissions and other costs associated with the offering.

The offering was comprised of Series F preferred stock, convertible into shares of the Company’s common stock at a conversion price of $4.50 per share. Each share of Series F preferred stock was accompanied by a Series 1 warrant, which expires on the first anniversary of its issuance, to purchase 223 shares of the Company’s common stock at an exercise price of $4.50 per share, and a Series 2 warrant, which expires on the seventh anniversary of its issuance, to purchase 223 shares of the Company’s common stock at an exercise price of $4.50 per share. The Series F preferred stock and the warrants were immediately separable and were issued separately. The conversion price of the Series F preferred stock will be adjusted in the event of a stock split, combination, reclassification or stock dividend or if the Company consummates a fundamental transaction. The Series F preferred stock also has full ratchet price based anti-dilution protection, subject to customary carve outs, in the event of a down-round financing at a price per share below the conversion price of the Series F preferred stock (which protection will expire if, during any 20 of 30 consecutive trading days, the volume weighted average price of the Company’s common stock exceeds 300% of the then-effective conversion price of the Series F preferred stock and the daily dollar trading volume for each trading day during such period exceeds $200,000) (See Note 9 – Subsequent Events). The exercise price of the warrants is fixed and does not contain any variable pricing features, nor any price based anti-dilutive features, apart from customary adjustments for stock splits, combinations, reclassifications, stock dividends or fundamental transactions. A total of 18,000 shares of Series F Convertible Preferred Stock convertible into approximately 4.0 million shares of common stock and warrants to purchase approximately 8.0 million shares of common stock were issued in the offering. The Series F Convertible Preferred Stock included a beneficial conversion amount of $8.7 million, representing the intrinsic value of the shares at the time of issuance. As of June 30, 2018 and December 31, 2017, 17,390 and 14,220 shares of the Series F Convertible Preferred Stock had been converted into an aggregate of 3,877,970 and 3,171,060 shares of common stock and 610 and 3,780 remained outstanding, respectively.

Placement Agent Fees: In connection with the issuance of the Series B, C and D Convertible Preferred Shares, the Company paid the placement agent an aggregate cash placement fee equal to 6% of the aggregate gross proceeds raised in the offering and issued warrants as described below. In connection with the issuance of the Series E and F Convertible Preferred Shares, the Company provided underwriting discounts and commissions of 9% and 8%, respectively, of the aggregate gross proceeds raised in the offering to the underwriter, and issued no warrants to the underwriter in such transactions.

Investor Warrants: In connection with the issuance of the Series B Convertible Preferred Stock in July 2016, the Company issued the investor, at no additional cost, warrants to purchase 6,149 shares of common stock at an exercise price of $564 per share. The warrants were exercisable for 36 months commencing six months from the closing date and were subject to a reduction of the exercise price if the Company subsequently issued common stock or equivalents at an effective price less than the current exercise price of such warrants. Concurrently with the closing of the Series C and D Convertible Preferred Stock and warrant financing on November 3, 2016, the exercise price for these warrants was adjusted to $102 per share.

In connection with the issuance of the Series C and D Convertible Preferred Stock in November 2016, the Company issued the investor, at no additional cost, warrants to purchase 35,295 shares of common stock at an exercise price of $108 per share. In connection with the issuance of the Series D Convertible Preferred Stock at the second closing in January 2017, the Company issued the investor, at no additional cost, warrants to purchase 1,961 shares of common stock at an exercise price of $108 per share. The warrants were exercisable for 60 months commencing on the earlier of the day of the receipt of approval of the Company’s stockholders of a proposal to approve the issuance of the shares of common stock underlying the warrants, or the six-month anniversary of the date of issuance. These warrants were subject to a reduction of the exercise price if the Company subsequently issued common stock or equivalents at an effective price less than the current exercise price of such warrants.

Warrant Exercise Agreement: On February 15, 2017, the Company entered into a letter agreement with the institutional investors that held the majority of its outstanding warrants (the ‘‘Original Warrants’’), to incent the cash exercise of the investor warrants described above on or before March 31, 2017. In exchange for any such exercise, the Company agreed to provide the investors a replacement warrant (the ‘‘Replacement Warrants’’) to purchase the same number of shares of common stock as were issued upon exercise of the Original Warrants, with an exercise price equal to the consolidated closing bid price of its common stock on the date of issuance. The Replacement Warrants were issued in the same form as the Original Warrants except the exercise prices are not subject to reduction for subsequent equity issuances and the Replacement Warrants do not allow the investor to demand that the Company purchase the Replacement Warrants in the event of a fundamental transaction involving the Company. In connection with this agreement, between February and March 2017, the investors exercised all of the Original Warrants for gross cash proceeds to the Company of $2.0 million, and the Company issued 43,396 Replacement Warrants with exercise prices ranging from $34.6 per share to $99.8 per share.

The Company entered into the letter agreement with the investors to incent the exercise of the Original Warrants in order to receive the cash proceeds from the exercise of the Original Warrants and because the exercise of the Original Warrants would allow the Company to remove the warrant liability from its balance sheet and avoid future fair value adjustments and associated volatility in its consolidated financial statements, as the Replacement Warrants are not accounted for as liabilities based on their terms. As of June 30, 2018, and December 31, 2017, there were no Original Warrants outstanding and all Replacement Warrants under the letter agreement had been issued.

Placement Agent Warrant: In connection with the issuance of the Series B, C and D Convertible Preferred Stock, the Company issued warrants to the placement agent to purchase an aggregate of 2,605 shares of common stock at exercise prices ranging from $126.0 per share to $810.0 per share. These warrants were issued at no additional cost, were exercisable immediately, and expire five years from the closing of each offering. These warrants do not contain repricing provisions.

Warrant Valuation: Both the Original Warrants and placement agent warrants were accounted for as liabilities and were recorded at fair value on the date of issuance. These warrants must be measured and recorded at fair value for each subsequent reporting period that the warrants remain outstanding, and any changes in fair value must be recognized in the consolidated statement of operations. In connection with the warrant exchange agreement described above, the Company remeasured each Original Warrant as of the date of exercise and recorded $1.4 million for the change in fair value of these warrants as an unrealized gain in the accompanying consolidated statement of operations for the six-month period ended June 30, 2017.

The Replacement Warrants were valued at $0.5 million using the Black Scholes valuation model with the following assumptions: an expected dividend yield of 0%, expected stock price volatility of 49.65%-50.38%, risk-free interest rates of 1.95%-1.97% and an expected life of 5 years. The warrants have a five-year life and were fully vested at the date of grant. The terms of these warrants do not require them to be accounted for as liabilities and are therefore recorded in equity. As in incentive to early exercise the Original Warrants, the fair value provided to investors through the Replacement Warrants exceeded the fair value of the Original Warrants that was relinquished by the warrant holders by approximately $0.1 million, which has been reflected as an expense in the statement of operations for the six-month period ending June 30, 2017.