6.    Convertible Preferred Stock and Stockholders’ Equity (Deficit)

Reverse Stock Split

On March 31, 2020, the Company held a special meeting of its stockholders, at which its stockholders approved an amendment to the Company’s certificate of incorporation, as amended, to effect a reverse stock split of all of the outstanding shares of common stock at a specific ratio within a range from one-for-four to one-for-twenty, and to grant authorization to the board of directors to determine, in its sole discretion, the specific ratio and timing of the reverse stock split. On April 9, 2020, a 1-for-20 reverse stock split was effected and the condensed consolidated financial statements have been retroactively adjusted. All common stock share numbers, warrants to purchase common stock, prices and exercise prices have been retroactively adjusted to reflect the reverse stock split. The par value of the common stock and the Series A 8% Senior Convertible Preferred Stock, par value $0.0001 per share (the “Series A Preferred Stock”) outstanding and its par value were not adjusted for the reverse stock split. The common stock began trading on a split-adjusted basis on that day under the new CUSIP number 86633R 203.

6.    Convertible Preferred Stock and Stockholders’ Equity (Deficit), continued

Series A 8% Senior Convertible Preferred Stock

On April 18, 2019, we entered into a Securities Purchase Agreement, dated as of April 18, 2019, with Lisa Walsh (the “Preferred SPA”), pursuant to which we issued 250,000 shares of our Series A 8% Senior Convertible Preferred Stock, par value $0.0001 per share (the “Series A Preferred Stock”), which shares did have a stated value of $4.00, grant holders the same voting rights as holders of our shares of common stock, and are convertible into shares of our common stock at price of $80.00 per share, subject to a floor price of $30.00 and to adjustment under our Certificate of Designations of the Preferences, Rights and Limitations of the Series A Preferred Stock, in consideration for $1,000,000 (the “Initial Tranche”). The Series A Preferred Stock may be issued in tranches of at least $500,000 and in an aggregate of up to $5 million. In connection with the Initial Tranche, the Company also issued to Ms. Walsh a warrant to purchase 12,756 shares of our common stock.

The Series A Preferred Stock contained an embedded conversion feature that the Company determined is a derivative requiring bifurcation. The fair value of the derivative liability at the issuance of the Series A Preferred Stock was $216,000, which was recorded as a derivative liability with the offset recorded as a discount to the Series A Preferred Stock. (See Note 5 – Fair Value Measurements for the fair value computation.)

As of September 30, 2021, the Company no longer has a derivative liability or any preferred stock outstanding, as all outstanding shares of Series A Preferred Stock were exchanged for 250,000 shares of common stock and warrants to purchase up to 187,500 shares of Common Stock during the three months ending June 30, 2021. On June 4, 2021, the Company and Lisa Walsh (the “Investor”) entered into an exchange agreement pursuant to which the Company effected such exchange of securities with the Investor.

As of September 30, 2021, there are 20,000,000 shares of preferred stock authorized, but there are no shares issued or outstanding.

Common Stock

Carve-Out Plan

For the three and nine months ended September 30, 2021, 0 and 352 shares of restricted stock issued under the Carve-Out Plan (the “Plan”), respectively, were released with an intrinsic value of approximately $0 and $2,000, respectively. For the three and nine months ended September 30, 2020, 353 and 706 shares of restricted stock were released with an intrinsic value of approximately $1,000 and $3,000, respectively.

2018 Long Term Stock Incentive Plan

On January 30, 2018, the Company’s board of directors approved the establishment of the Company’s 2018 Long-Term Stock Incentive Plan (the “LTIP”) and termination of the Plan. Under the LTIP, the aggregate maximum number of shares of common stock (including shares underlying options) that may be issued under the LTIP pursuant to awards of Restricted Shares or Options will be limited to 15% of the outstanding shares of common stock , which calculation shall be made on the first trading day of each new fiscal year; provided that, in any year no more than 8% of the common stock or derivative securitization with common stock underlying 8% of the common stock may be issued in any fiscal year. Thereafter, the 15% evergreen provision governs the LTIP. For fiscal year 2021, up to 672,180 shares of common stock are available for participants under the LTIP.

For the three and nine months ended September 30, 2021, 29,064 shares of restricted stock issued under the LTIP, were released with an intrinsic value of approximately $93,000. For the three and nine months ended September 30, 2020, 0 shares of restricted stock were released.

6.    Convertible Preferred Stock and Stockholders’ Equity (Deficit), continued

A summary of activity related to restricted stock awards (excluding the deferred shares and the inducement grant restricted stock award) for the nine months ended September 30, 2021 is presented below:

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As of September 30, 2021, the unamortized compensation costs related to the unvested restricted stock awards was approximately $2,028,000 which is to be amortized on a straight-line basis over a weighted-average period of approximately 2.4 years.

On September 13, 2021, the Company issued 310,000 shares of restricted common stock to Eric Almgren, the Company’s new Chief Strategist, as an inducement grant (“September 2021 Inducement Grant”). Such shares were issued outside the Company’s LTIP and 2020 Stock Plan. In accordance with the September 2021 Inducement Grant, 77,500 shares will vest monthly over a period of 36 months and the remaining 232,500 will vest in 77,500 increments, upon the achievement of certain company milestones related to the volume weighted average closing price per share of the Company’s common stock, as reported on NASDAQ, for the ten (10) consecutive days in which thresholds of the Company’s market capitalization of $75 million, $100 million and $150 million are achieved. The September 2021 Inducement Grant has been valued with an approximate value of $772,000 and will be amortized over 36 months. The Company recorded $10,000 of stock-based compensation for the three and nine months ended September 30, 2021.

2020 Stock Incentive Plan

On July 27, 2020, the board of directors adopted the Company’s 2020 Stock Incentive Plan (the “2020 Stock Plan”) and the reservation of an aggregate of 650,000 shares of the Company’s common stock authorized for issuance under the 2020 Stock Plan, subject to stockholder approval. The 2020 Stock Plan authorizes the grant of equity-based compensation to the Company’s senior managers, employees, directors, consultants, professionals and service providers in the form of stock options, restricted stock and restricted stock units. On July 27, 2020, the Company also granted, subject to stockholder approval, an aggregate of 614,824 restricted stock units to senior managers, employees, directors, consultants. Each of the awards are scheduled to vest on the first, second, and third anniversaries of August 15, 2020, so long as such award recipient remains in service of the Company on each such anniversary. Each restricted stock unit represents the right to receive one share of the Company’s common stock under the 2020 Stock Plan. On October 20, 2020, the Company held the 2020 Annual Meeting of Stockholders and approved the adoption of the 2020 Stock Plan and the reservation of an aggregate of 650,000 shares of the Company’s common stock. In connection with the approval, the Company issued 614,824 restricted stock units to employees, directors and consultants.

6.    Convertible Preferred Stock and Stockholders’ Equity (Deficit), continued

A summary of activity related to restricted stock units under the Company’s 2020 Stock Plan for the nine months ended September 30, 2021 is presented below:

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As of September 30, 2021, the unamortized compensation costs related to the unvested restricted stock units was approximately $1,042,000 which is to be amortized on a straight-line basis over a weighted-average period of approximately 1.9 years.

For the three and nine months ended September 30, 2021, 201,343 shares of restricted stock units were released under the 2020 Stock Plan with an intrinsic value of approximately $646,000. For the three and nine months ended September 30, 2020, no shares of restricted stock units were released.

February 2020 Private Placement

On February 28, 2020, the Company completed a private placement (the “February 2020 Private Placement”) of 91,062 units (the “Units”), each unit consisting of (i) one (1) share of common stock and (ii) a warrant to purchase 0.50 of a share of common stock (the “February 2020 Warrants”), at a price per Unit of $9.17. The Units were issued pursuant to a Unit Purchase Agreement, dated February 4, 2020, and a subscription agreement, dated February 28, 2020 by and among the Company and the purchasers signatory thereto. In connection with the February 2020 Private Placement, we paid Alexander Capital, L.P. (“Alexander”) cash fees of $83,000 and issued to Alexander a warrant to purchase 4,553 shares of common stock (the “February 2020 Alexander Warrant”). Such warrant is exercisable at a per share price of $8.80 and is exercisable at any time during the five-year period commencing on the date of issuance. The February 2020 Private Placement, which was priced above market, resulted in gross proceeds of $835,000 before fees and other expenses associated with the transaction.

The February 2020 Warrants are exercisable to purchase up to an aggregate of 45,534 shares of common stock commencing on the date of issuance at an exercise price of $9.80 per share, subject to adjustment upon stock splits, reverse stock splits, and similar capital changes. The February 2020 Warrants are exercisable immediately and will expire on the close of business on February 28, 2025. The exercise of the February 2020 Warrants are subject to beneficial ownership limitations such that each holder of such February 2020 Warrant may exercise it to the extent that such exercise would result in such holder being the beneficial owner in excess of 4.99% (or, upon election of such holder, 9.99%), which beneficial ownership limitation may be increased or decreased up to 9.99% upon notice to the Company, provided that any increase in such limitation will not be effective until 61 days following notice to the Company.

The grant date fair value of February 2020 Warrants was $103,000, which was recorded within stockholders’ equity as a cost of issuance and an increase to additional paid-in capital on the accompanying condensed consolidated balance sheet. The fair value of such warrants was determined using the Black-Scholes Model based on the following weighted average assumptions: common stock price on date of grant of $6.00; expected dividend yield of 0.0%; expected volatility of 59.0%; risk-free interest rate of 0.89% and expected life of 5 years.

6.    Convertible Preferred Stock and Stockholders’ Equity (Deficit), continued

The fair value of the February 2020 Alexander Warrant at issuance was $11,000. The fair value of such warrant was estimated using the Black-Scholes Model based on the following weighted average assumptions: common share price on date of grant $6.00, expected dividend yield 0%, expected volatility 59%, risk-free interest rate 0.89% and expected life of 5 years. The fair value was recorded within stockholders’ equity as a cost of issuance and an increase to additional paid-in capital on the accompanying condensed consolidated balance sheet.

April 2020 Public Offering

On April 23, 2020, the Company closed an underwritten public offering of 1,525,000 shares of its common stock, pre-funded common stock purchase warrants to purchase up to an aggregate of 475,000 shares of common stock, and common stock purchase warrants to purchase up to an aggregate of 2,000,000 shares of the Company’s common stock (the “April 2020 Public Offering”). Each share of common stock or pre-funded common stock purchase warrant was sold together with one common stock purchase warrant to purchase one share of common stock at a combined price to the public of $3.25 per share and common stock purchase warrant (or $3.24 per pre-funded common stock purchase warrant and common stock purchase warrant). Gross proceeds before deducting underwriting discounts, commissions and other offering expenses were approximately $6.5 million. In addition, the Company granted to Maxim a 45-day option to purchase up to an additional 300,000 shares of common stock and/or common stock purchase warrants to purchase up to an aggregate of 300,000 shares of common stock, at the public offering price, less discounts and commissions, of which Maxim partially exercised its option to purchase additional common stock purchase warrants to purchase up to an aggregate of 229,100 shares of common stock. Each common stock purchase warrant is immediately exercisable for one share of common stock at an exercise price of $3.25 per share and will expire five years from issuance. The Company also issued a warrant to Maxim to purchase up to 100,000 shares of common stock in connection with the April 2020 Public Offering (the “April 2020 Maxim Warrant”). Such warrant has an exercise price of $3.90 per share and is fully vested.

May 2020 Shelf Registration

On May 18, 2020, we registered for resale, pursuant to a prospectus supplement to our shelf registration statement, an aggregate of 60,250 shares of common stock, 50,000 of which shares were the Alexander Settlement Shares, and the remaining 10,250 of such shares which were issued to one of the Company’s vendors pursuant to the Settlement Letter, dated May 12, 2020, by and between us and such vendor.

Purchase Agreements

On June 4, 2020, we entered into a securities purchase agreement (the “June 4, 2020 Purchase Agreement”) with several accredited investors providing for the issuance of (i) 2,275,000 shares of the Company’s common stock and (ii) warrants, with a term of 5.5 years, to purchase an aggregate of up to 2,275,000 shares of common stock at an exercise price of $2.55 per share, subject to customary adjustments thereunder, which warrants were immediately exercisable upon issuance and on a cashless basis if such warrants have not been registered on or before six months after the date of issuance. Pursuant to the June 4, 2020 Purchase Agreement, the investors purchased all of the securities sold thereby for an aggregate purchase price of $5,801,000. Pursuant to the June 4, 2020 Purchase Agreement, an aggregate of 2,275,000 shares of common stock were issued to the investors in a registered direct offering pursuant to a prospectus supplement to the Company’s currently effective registration statement on Form S-3, which was declared effective on September 6, 2019. The Company filed the prospectus supplement on June 5, 2020. Maxim acted as the placement agent. The warrants were issued to the investors in a concurrent private placement transaction pursuant to an exemption from the registration requirements of the Securities Act provided in Section 4(a)(2) of the Securities Act and/or Regulation D promulgated thereunder. The Company paid Maxim a fee of approximately $464,000, which was equal to 8% of the aggregate purchase price paid by investors placed by Maxim and certain expenses. The June 4, 2020 Purchase Agreement contains customary representations, warranties and agreements of the Company and the investors and customary indemnification rights and obligations of the parties thereto. The offering of the securities pursuant to the June 4, 2020 Purchase Agreement was closed on June 8, 2020.

6.    Convertible Preferred Stock and Stockholders’ Equity (Deficit), continued

On June 9, 2020, we entered into a securities purchase agreement (the “June 9, 2020 Purchase Agreement”) with several accredited investors providing for the issuance of (i) 2,040,000 shares of the Company’s common stock and (ii) warrants, with a term of 5.5 years, to purchase an aggregate of up to 2,040,000 shares of common stock at an exercise price of $2.61 per share, subject to customary adjustments thereunder, which warrants were immediately exercisable upon issuance and on a cashless basis if the Warrants have not been registered on or before six months after the date of issuance. Pursuant to the June 9, 2020 Purchase Agreement, the investors purchased all of the securities sold thereby for an aggregate purchase price of $5,324,000. Pursuant to the June 9, 2020 Purchase Agreement, an aggregate of 2,040,000 shares of common stock were issued to the investors in a registered direct offering, pursuant to a prospectus supplement to the Company’s currently effective registration statement on Form S-3, which was declared effective on September 6, 2019. The Company filed the prospectus supplement on June 10, 2020. Maxim acted as the placement agent. The warrants were issued to the investors in a concurrent private placement transaction pursuant to an exemption from the registration requirements of the Securities Act provided in Section 4(a)(2) of the Securities Act and/or Regulation D promulgated thereunder. The Company paid Maxim a fee of approximately $426,000, which was equal to 8% of the aggregate purchase price paid by investors placed by Maxim and certain expenses. The June 9, 2020 Purchase Agreement contains customary representations, warranties and agreements of the Company and the investors and customary indemnification rights and obligations of the parties thereto. The offering of the securities pursuant to the June 9, 2020 Purchase Agreement was closed on June 11, 2020.

On July 22, 2021, the Company entered into a securities purchase agreement (the “July 22nd Purchase Agreement”) with several accredited investors providing for the issuance of 2,500,000 shares of the Company’s common stock. Pursuant to the July 22nd Purchase Agreement, the investors purchased all of the securities sold thereby for an aggregate purchase price of $10,000,000. Pursuant to the July 22nd Purchase Agreement, an aggregate of 2,500,000 shares of common stock were issued to the investors in a registered direct offering pursuant to a prospectus supplement to the Company’s currently effective registration statement on Form S-3, which was declared effective on September 6, 2019. The offering of the securities pursuant to the July 22nd Purchase Agreement was closed on July 27, 2021. The Company filed the prospectus supplement on July 26, 2021. Maxim acted as the placement agent. The Company paid Maxim a fee of approximately $800,000, which was equal to 8% of the aggregate purchase price paid by investors placed by Maxim and certain expenses. The July 22nd Purchase Agreement contains customary representations, warranties and agreements of the Company and the investors and customary indemnification rights and obligations of the parties thereto.

Settlement Agreements

On May 14, 2020, we entered into a settlement agreement with Alexander (the “Alexander Settlement Agreement”), pursuant to which, in consideration for Alexander releasing us from all claims against us arising out of that certain engagement agreement, dated February 6, 2020, that we entered into with Alexander (the “Alexander Engagement Agreement”), other than indemnification for certain third-party claims, we agreed to (i) pay Alexander a one-time cash payment of $125,000 and (ii) issue to Alexander 50,000 shares of our common stock (the “Alexander Settlement Shares”) which had a value of approximately $111,000. We also released Alexander from the same type of claims against Alexander, other than indemnification for certain third-party claims. In connection with the Alexander Settlement Agreement, on May 14, 2020, we also entered into a leak-out agreement with Alexander (the “Alexander Leak-Out Agreement”), pursuant to which Alexander agreed not to dispose of more than 5,000 shares of common stock in any trading day, commencing on the date of such agreement and ending on the date on which Alexander no longer holds any Alexander Settlement Shares. The Company recorded a settlement expense of $237,000 which is included in general and administrative expense for the nine months ended September 30, 2020.

6.    Convertible Preferred Stock and Stockholders’ Equity (Deficit), continued

On November 9, 2020, in order to resolve a dispute between certain investors (the “February 2020 Holders”) and the Company regarding certain registration rights in connection with the February 2020 Private Placement, the Company entered into a settlement and release agreement with each of the February 2020 Holders (the “Settlement Agreement”), pursuant to which (i) the Company and the February 2020 Holders agreed to amend the original warrants issued in February 2020 (the “Original Warrants”) to provide for the purchase of one additional share of common stock for each share of common stock available under the Original Warrants, totaling 45,534 additional common stock purchase warrants, (ii) the Company and the February 2020 Holders agreed to amend the Original Warrants to reduce the exercise price to $2.55, and (iii) the Company agreed to issue an additional 236,375 shares of common stock and 236,369 common stock purchase warrants to purchase up to 236,369 shares of common stock. As consideration for the foregoing, the February 2020 Holders agreed to release any and all claims they may have against the Company, including, but not limited to, claims arising in connection with any securities held by the February 2020 Holders.

Warrants for Shares of Common Stock

The Company has issued warrants to purchase shares of common stock to employees and consultants as compensation for services rendered, as well as in conjunction with the purchase of shares of common stock in equity and debt transactions.

In connection with the March 2020 Note, the Company issued the March 2020 Note to the investor and the March 2020 Maxim Warrant to Maxim to purchase shares of common stock of 227,679 and 20,400, respectively (see Note 4 – Borrowings) at an exercise price of $6.40 per share. The grant date fair value of such warrants was $625,000, which was recorded as debt discount with the offset recorded to additional paid-in capital on the condensed consolidated balance sheets. The fair value of such warrants was determined using the Black-Scholes Model based on the following weighted average assumptions: common stock price on date of grant of $5.40; expected dividend yield of 0.0%; expected volatility of 61.0%; risk-free interest rate of 0.38% and expected life of 5 years.

Such warrant issued to the investor contained an adjustment provision such that if the Company issues or sells any shares of common stock or common stock equivalents (as defined in the March 2020 Note), subject to certain exceptions, at an effective price lower than the conversion price, then in effect, the conversion price shall be reduced to the price per share paid for such shares of common stock or common stock equivalents. The common stock and common stock equivalents issued by the Company in the April 2020 Public Offering were issued at price per share of $3.25, which was lower than the conversion price then in effect. Additionally, the Alexander Settlement Shares, issued to Alexander under the Alexander Settlement Agreement, on May 14, 2020, were issued at a price per share which was lower than the conversion price then in effect. The Company modified the exercise price of the March 2020 Warrant as a result of each of these transactions and calculated the incremental fair value related to these modifications. The resulting deemed dividend from these down round adjustments was $134,000, and this is included as an offset to additional paid-in capital in the accompanying condensed consolidated balance sheets.

Concurrent with the April 2020 Public Offering, the Company issued prefunded warrants for $475,000 at an exercise price of $0.01 per share. These warrants were exercised immediately upon the closing of the transactions for proceeds of $4,750 and the investors received 475,000 shares of common stock.

Additionally, as a result of the April 2020 Public Offering, the Company issued warrants to purchase shares of common stock to the common stock investors, prefunded warrants investors, and Maxim of 1,525,000, 475,000 and 291,000, respectively. The warrants have an exercise price of $3.25 per share and are fully vested. The grant date fair value of those warrants was $2,606,000, which was recorded within stockholders’ equity as a cost of issuance and an increase to additional paid-in capital on the accompanying condensed consolidated balance sheet. The fair value of the warrants was determined using the Black-Scholes Model based on the following weighted average assumptions: common stock price on date of grant of $2.50; expected dividend yield of 0.0%; expected volatility of 64.0%; risk-free interest rate of 0.37% and expected life of 5 years.

6.    Convertible Preferred Stock and Stockholders’ Equity (Deficit), continued

The Company also issued the April 2020 Maxim Warrant to purchase up to 100,000 shares of common stock to Maxim in connection with the April 2020 Public Offering. Such warrant has an exercise price of $3.90 per share and is fully vested. The fair value of such warrant at issuance was $106,000. The fair value of the warrant was estimated using the Black-Scholes Model based on the following weighted average assumptions: common share price on date of grant $2.50, expected dividend yield 0%, expected volatility 64%, risk-free interest rate 0.37% and expected life of 5 years. The fair value was recorded within stockholders’ equity as a cost of issuance and an increase to additional paid-in capital on the accompanying condensed consolidated balance sheet.

In connection with the offering pursuant to the June 4, 2020 Purchase Agreement, the Company issued warrants to the investors to purchase up to an aggregate of 2,275,000 shares of common stock. Such warrants have an exercise price of $2.55 per share and are fully vested. The grant date fair value of those warrants was $3,153,000, which was recorded within stockholders’ equity as a cost of issuance and an increase to additional paid-in capital on the accompanying condensed consolidated balance sheet. The fair value of such warrants was determined using the Black-Scholes Model based on the following weighted average assumptions: common stock price on date of grant of $2.52; expected dividend yield of 0.0%; expected volatility of 64.0%; risk-free interest rate of 0.45% and expected life of 5.5 years.

In connection with the offering pursuant to the June 9, 2020 Purchase Agreement, the Company issued warrants to the investors to purchase up to an aggregate of 2,040,000 shares of common stock. Such warrants have an exercise price of $2.61 per share and are fully vested. The grant date fair value of those warrants was $2,375,000, which was recorded within stockholders’ equity as a cost of issuance and an increase to additional paid-in capital on the accompanying condensed consolidated balance sheet. The fair value of such warrants was determined using the Black-Scholes Model based on the following weighted average assumptions: common stock price on date of grant of $2.25; expected dividend yield of 0.0%; expected volatility of 64.0%; risk-free interest rate of 0.32% and expected life of 5.5 years.

In January 2021, pursuant to the Company’s solicitation of certain warrant holders, such warrant holders agreed to exercise warrants to purchase an aggregate of 1,221,675 shares of common stock for net proceeds of approximately $2.9 million. In consideration for their exercise of these warrants, for cash, the exercising holders were issued new warrants to purchase up to an aggregate of 305,419 shares of common stock, at an exercise price of $4.20 per share, which are exercisable for a period of five years. The grant date fair value of those warrants was $567,000, which was recorded as warrant inducement expense and an increase to additional paid-in capital on the accompanying condensed consolidated balance sheet. The fair value of such warrants was determined using the Black-Scholes Model based on the following weighted average assumptions: common stock price on date of grant of $3.85; expected dividend yield of 0.0%; expected volatility of 60.1%; risk-free interest rate of 0.45% and expected life of 5.0 years.

On April 18, 2019, the Company entered into a Securities Purchase Agreement with an existing shareholder, Lisa Walsh (the “Investor”), pursuant to which the Company issued 250,000 shares of our Series A 8% Convertible Preferred Stock (the “Original Securities”). On June 4, 2021, the Company and the Investor entered into that an exchange agreement pursuant to which the Company exchanged with the Investor the Original Securities held by the investor for: (i) 250,000 shares of common stock and (ii) warrants to purchase up to 187,500 shares of Common Stock. The warrants will be exercisable for a period of five (5) years and four (4) months. The exercise price with respect to the warrants is $3.00 per share. The exercise price and the number of shares of common stock issuable upon exercise of the warrants are subject to adjustment upon certain events, such as stock splits, combinations, dividends, distributions, reclassifications, mergers or other corporate change and dilutive issuances. The grant date fair value of those warrants was $570,000, which was recorded as loss on exchange of preferred stock and an increase to additional paid-in capital on the accompanying condensed consolidated balance sheet. The fair value of such warrants was determined using the Black-Scholes Model based on the following weighted average assumptions: common stock price on date of grant of $4.77; expected dividend yield of 0.0%; expected volatility of 60.7%; risk-free interest rate of 0.78% and expected life of 5.4 years.

6.    Convertible Preferred Stock and Stockholders’ Equity (Deficit), continued

In June 2021, pursuant to the Company’s solicitation of certain warrant holders, such warrant holders agreed to exercise warrants to purchase an aggregate of 1,000,000 shares of common stock for net proceeds of approximately $2.3 million. In consideration for their exercise of these warrants, for cash, the exercising holders were issued new warrants to purchase up to an aggregate of 250,000 shares of common stock, at an exercise price of $4.46 per share, which are exercisable for a period of five years. The grant date fair value of those warrants was $579,000, which was recorded as warrant inducement expense and an increase to additional paid-in capital on the accompanying condensed consolidated balance sheet. The fair value of such warrants was determined using the Black-Scholes Model based on the following weighted average assumptions: common stock price on date of grant of $4.50; expected dividend yield of 0.0%; expected volatility of 60.7%; risk-free interest rate of 0.77% and expected life of 5.0 years.

During the three months ended September 30, 2021, warrant holders exercised 19,000 warrants to purchase common stock, for proceeds of approximately $62,000.

Information regarding warrants for common stock outstanding and exercisable as of September 30, 2021 is as follows:

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Warrants exercisable as of September 30, 2021 excludes warrants to purchase 15,000 shares of common stock issued to a marketing firm, which vest upon the achievement of certain milestones. Additionally, warrants to purchase 20,722 shares of common stock which are shown above with a price of $15.80 are pre-funded warrants under which the holder must only pay $0.20 per share to complete the exercise.

Information regarding warrants for common stock outstanding and exercisable as of December 31, 2020 is as follows:

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6.    Convertible Preferred Stock and Stockholders’ Equity (Deficit), continued

Warrants exercisable as of December 31, 2020 exclude a warrant to purchase 15,000 shares of common stock issued to a marketing consulting firm. Such warrant will vest upon the achievement of certain milestones. Additionally, warrants to purchase 20,722 shares of common stock which are shown above with a price of $15.80 are pre-funded warrants under which the holder must only pay $0.20 per share to complete the exercise.