Filed Pursuant to Rule 497
File No. 333-225447

PROSPECTUS SUPPLEMENT

(to Prospectus dated July 13, 2018)

2,600,000 Shares

6.375% Series E Cumulative Term Preferred Stock due 2025

(Liquidation Preference $25.00 per Share)

We are an externally managed, closed-end, non-diversified management investment company that has elected to be regulated as a business development company under the Investment Company Act of 1940, as amended (the “1940 Act”). For federal income tax purposes, we have elected to be treated as a regulated investment company under Subchapter M of the Internal Revenue Code of 1986, as amended (the “Code”). Our investment objectives are to: (i) achieve and grow current income by investing in debt securities of established businesses that we believe will provide stable earnings and cash flow to pay expenses, make principal and interest payments on our outstanding indebtedness and make distributions to stockholders that grow over time; and (ii) provide our stockholders with long-term capital appreciation in the value of our assets by investing in equity securities, generally in combination with the aforementioned debt securities, of established businesses that we believe can grow over time to permit us to sell our equity investments for capital gains.

We are offering 2,600,000 shares of our 6.375% Series E Term Cumulative Preferred Stock due 2025 (the “Series E Term Preferred Stock”). We will pay monthly dividends on the Series E Term Preferred Stock at an annual rate of 6.375% of the $25.00 liquidation preference per share, or $1.5938 per share of Series E Term Preferred Stock per year, on or about the last business day of each month, as declared by our Board of Directors, commencing on September 28, 2018.

We are required to redeem all of the outstanding Series E Term Preferred Stock on August 31, 2025 at a redemption price equal to $25.00 per share, plus an amount equal to accumulated but unpaid dividends, if any, to, but excluding, the date of redemption. We will also be required to redeem Series E Term Preferred Stock at a redemption price equal to $25.00 per share, plus an amount equal to accumulated but unpaid dividends, if any, to, but excluding, the date of redemption in the event of certain events that constitute a change of control of the Company. If we fail to maintain an asset coverage as required by Sections 18 and 61 of the 1940 Act (which is currently 200% and will be 150% effective April 10, 2019, unless earlier approved by the Company’s stockholders), we will redeem a sufficient number of shares of our then-outstanding shares of preferred stock (currently outstanding and any future issuances of preferred stock, collectively, the “Preferred Stock”) in an amount at least equal to the lesser of (1) the minimum number of shares of Preferred Stock necessary to cause us to meet our required asset coverage and (2) the maximum number of Preferred Stock that we can redeem out of cash legally available for such redemption. At any time on or after August 31, 2020, at our sole option, we may redeem the Series E Term Preferred Stock at a redemption price of $25.00 per share of Series E Term Preferred Stock, plus any accumulated but unpaid dividends, if any, on the Series E Term Preferred Stock up to, but excluding, the date of redemption. We cannot effect any amendment, alteration or repeal of our obligation to redeem all of the Series E Term Preferred Stock on August 31, 2025 without the prior unanimous consent of the holders of Series E Term Preferred Stock.

Each holder of our Series E Term Preferred Stock (and any other then-outstanding Preferred Stock we have issued or may issue in the future) will be entitled to one vote for each share held by such holder on any matter submitted to a vote of our stockholders, and the holders of all of our outstanding Preferred Stock and common stock will generally vote together as a single class. The holders of the our Preferred Stock, voting separately as a single class, will elect two of our directors and, upon our failure to pay dividends for at least two years, will elect a majority of our directors. The Series E Term Preferred Stock will rank equally in right of payment with all other shares of Preferred Stock and will rank senior in right of payment to our outstanding common stock.

We have applied to have the Series E Term Preferred Stock listed on Nasdaq under the symbol “GAINL.” Our common stock is traded on Nasdaq under the symbol “GAIN.” On August 13, 2018, the last sale price of our common stock, Series B Term Preferred Stock, Series C Term Preferred Stock and Series D Term Preferred Stock as reported on Nasdaq was $11.97 per share, $25.33 per share, $25.31 per share and $25.28 per share, respectively. The Series E Term Preferred Stock has no trading history and will not be convertible into our common stock or any other security of our company.

This prospectus supplement and the accompanying prospectus contain important information you should know before investing in the Series E Term Preferred Stock, including information about risks. Please read it before you invest and retain it for future reference. Additional information about us, including our annual, quarterly and current reports, has been filed with the Securities and Exchange Commission (the “SEC”), and can be accessed at its website at www.sec.gov. This information is also available free of charge by calling us collect at (866) 366-5745 or on the investor relations section of our corporate website located at www.GladstoneInvestment.com. You may also call us collect at this number to request other information or to make a shareholder inquiry. The information contained in, or that can be accessed through, our website is not part of this prospectus supplement or the accompanying prospectus. See “Where You Can Find More Information” on page S-65 of this prospectus supplement. 

The securities in which we invest generally would be rated below investment grade if they were rated by rating agencies. Below investment grade securities, which are often referred to as “junk,” have predominantly speculative characteristics with respect to the issuer’s capacity to pay interest and repay principal. They may also be difficult to value and are illiquid.

Investing in the Series E Term Preferred Stock involves a high degree of risk, including, among other things, the risk of leverage and risks relating to investments in securities of small, private and developing businesses. You could lose some or all of your investment. You should carefully consider each of the factors described under “Risk Factors” beginning on page S-11 of this prospectus supplement and beginning on page 13 of the accompanying prospectus before you invest in the Series E Term Preferred Stock.

The SEC, has not approved or disapproved of these securities or determined if this prospectus supplement or the accompanying prospectus is truthful or complete. Any representation to the contrary is a criminal offense.

The underwriters expect to deliver the Series E Term Preferred Stock on or about August 22, 2018.

Joint Book-Running Managers

Lead Manager

B. Riley FBR

Co-Managers

Prospectus Supplement dated August 14, 2018

ABOUT THIS PROSPECTUS SUPPLEMENT

This prospectus supplement, together with the accompanying prospectus, sets forth the information that you should know before investing. You should read the prospectus supplement and accompanying prospectus, which contain important information, before deciding whether to invest in the Series E Term Preferred Stock.

This prospectus supplement, which describes the specific terms of this offering, also adds to and updates information contained in the accompanying prospectus. The accompanying prospectus gives more general information, some of which may not apply to this offering. If the description of this offering varies between this prospectus supplement and the accompanying prospectus, you should rely on the information contained in this prospectus supplement. However, if any statement in one of these documents is inconsistent with a statement in another document having a later date, the statement in the document having the later date modifies or supersedes the earlier statement.

The Series E Term Preferred Stock does not represent a deposit or obligation of, and is not guaranteed or endorsed by, any bank or other insured depository institution, and is not federally insured by the Federal Deposit Insurance Corporation, the Federal Reserve Board or any other government agency.

You should rely only on the information contained in this prospectus supplement and the accompanying prospectus in making an investment decision. Neither we nor the underwriters have authorized any other person to provide you with different or inconsistent information. If anyone provides you with different or inconsistent information, you should not rely on it. The information appearing in this prospectus supplement, the accompanying prospectus is accurate only as of the respective dates of such information regardless of the time of delivery or any sale of the Series E Term Preferred Stock. Our business, financial condition, results of operations and prospects may have changed since those dates.

We are not, and the underwriters are not, making an offer to sell the Series E Term Preferred Stock in any jurisdiction where such an offer or sale is not permitted.

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TABLE OF CONTENTS

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RISK FACTORS

You should carefully consider the risks described below, and the risks described in “Risk Factors” beginning on page 13 of the accompanying prospectus, before deciding to invest in the Series E Term Preferred Stock. The risks and uncertainties described below and in the accompanying prospectus are not the only ones we face. Additional risks and uncertainties not presently known to us, or not presently deemed material by us, may also impair our operations and performance and the value of the Series E Term Preferred Stock. If any of the following risks or the risks described in the accompanying prospectus actually occur, our business, financial condition or results of operations could be materially adversely affected, and the value of the Series E Term Preferred Stock may be impaired. If that happens, the trading price of the Series E Term Preferred Stock could decline, and you may lose all or part of your investment.

Risks of Investing in Preferred Stock

We may be unable to use the net proceeds from this offering to redeem our Series B Term Preferred Stock and Series C Term Preferred Stock within the time period that we anticipate or at all, which could adversely affect our financial condition and results of operations and increase the likelihood of our failing to meet the asset coverage requirements of the 1940 Act.

We intend to use the net proceeds from this offering plus borrowings under our Credit Facility to redeem all outstanding shares of our Series B Term Preferred Stock and Series C Term Preferred Stock and for other general corporate purposes. We anticipate that substantially all of the net proceeds of this offering will be utilized in this manner within three months of the completion of this offering. However, we cannot assure you that we will be able to redeem the Series B Term Preferred Stock and Series C Term Preferred Stock within this time period or at all. Any delay or failure to use the net proceeds from this offering to redeem the Series B Term Preferred Stock and Series C Term Preferred Stock could adversely affect our financial condition and results of operations and increase the likelihood of our failing to meet the asset coverage requirements of the 1940 Act, as described below under “—Our amount of senior securities that are stock outstanding will increase as a result of this offering if we are unable to redeem shares of our Series B Term Preferred Stock and Series C Term Preferred Stock within the time period that we anticipate or at all, which could adversely affect our business, financial condition and results of operations, our ability to meet our payment obligations under the Credit Facility and our ability to meet the asset coverage requirements of the 1940 Act. ”

An investment in term preferred stock with a fixed interest rate bears interest rate risk.

Term preferred stock, including the Series E Term Preferred Stock, pays dividends at a fixed dividend rate. Prices of fixed income investments vary inversely with changes in market yields. The market yields on securities comparable to the Series E Term Preferred Stock may increase, which would likely result in a decline in the secondary market price of the Series E Term Preferred Stock prior to the Mandatory Term Redemption Date. This risk may be even more significant in light of currently low prevailing market interest rates. For additional information concerning dividends on the Series E Term Preferred Stock, see “Description of the Series E Term Preferred Stock—Dividends and Dividend Periods.”

There is no guarantee that the Series E Term Preferred Stock will be approved for listing on Nasdaq, there may be no initial secondary trading market due to delayed listing, and even after listing a liquid secondary trading market may not develop.

We have applied to list the Series E Term Preferred Stock on Nasdaq, and we do not know when the Series E Term Preferred Stock will be approved for listing, if at all. If approved, we expect the Series E Term Preferred Stock to begin trading on Nasdaq within 30 days of the date of this prospectus supplement, though there can be no assurance that the Series E Term Preferred Stock will begin trading within this period, or at all. During the time the Series E Term Preferred Stock is not listed on Nasdaq, the underwriters may make a market in the Series

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E Term Preferred Stock, but they are not obligated to do so and may discontinue any market-making at any time without notice. Consequently, an investment in the Series E Term Preferred Stock during this period may be illiquid, and holders of such shares may not be able to sell them during that period as it is unlikely that an active secondary market for the Series E Term Preferred Stock will develop. If a secondary market does develop during this period, holders of the Series E Term Preferred Stock may be able to sell such shares only at substantial discounts from the Liquidation Preference. We cannot accurately predict the trading patterns of the Series E Term Preferred Stock, including the effective costs of trading the stock.

Even if our Series E Term Preferred Stock begins trading on Nasdaq, there is also a risk that such shares may be thinly traded, and the market for such shares may be relatively illiquid compared to the market for other types of securities, with the spread between the bid and asked prices considerably greater than the spreads of other securities with comparable terms and features. If an active trading market does develop, the Series E Term Preferred Stock may trade at prices lower than the initial offering price. The trading price of the Series E Term Preferred Stock would depend on many factors, including:

The Series E Term Preferred Stock will not be rated.

We do not intend to have the Series E Term Preferred Stock rated by any rating agency. Unrated securities usually trade at a discount to similar, rated securities. As a result, there is a risk that the Series E Term Preferred Stock may trade at a price that is lower than it might otherwise trade if rated by a rating agency. It is possible, however, that one or more rating agencies might independently determine to assign a rating to the Series E Term Preferred Stock. In addition, we may elect to issue other securities for which we may seek to obtain a rating. If any ratings are assigned to the Series E Term Preferred Stock in the future or if we issue other securities with a rating, such ratings, if they are lower than market expectations or are subsequently lowered or withdrawn, could adversely affect the market for or the market value of the Series E Term Preferred Stock.

The Series E Term Preferred Stock will bear a risk of early redemption by us.

We may voluntarily redeem some or all of the Series E Term Preferred Stock on or after August 31, 2020, which is five years before the Mandatory Term Redemption Date. We also may be forced to redeem some or all of the Series E Term Preferred Stock to meet regulatory requirements and the Asset Coverage requirements. We are also required to redeem all of the Series E Term Preferred Stock upon a Change of Control Triggering Event. Any such redemptions may occur at a time that is unfavorable to holders of the Series E Term Preferred Stock. We may have an incentive to redeem the Series E Term Preferred Stock voluntarily before the Mandatory Term Redemption Date if market conditions allow us to issue other Preferred Stock or debt securities at a rate that is lower than the Fixed Dividend Rate on the Series E Term Preferred Stock, or for other reasons. For further information regarding our ability to redeem the Series E Term Preferred Stock, see “Description of the Series E Term Preferred Stock—Optional Redemption” and “—Asset Coverage.”

Claims of holders of the Series E Term Preferred Stock will be subject to a risk of subordination relative to holders of our debt instruments.

Rights of holders of the Series E Term Preferred Stock will be subordinated to the rights of holders of our current and any future indebtedness, including the Credit Facility. Even though the Series E Term Preferred Stock will be

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officer, uses an established investment valuation policy, or the Policy, which has been approved by our Board of Directors, and each quarter our Board of Directors reviews the Policy to determine if changes thereto are advisable and also reviews whether the Valuation Team has applied the Policy consistently. We may engage other independent valuation firms to provide earnings multiple ranges, as well as other information, and evaluate such information for incorporation into the total enterprise value (“TEV”), of certain of our investments. Generally, at least once per year, we engage an independent valuation firm to value or review our valuation of our significant equity investments, which includes providing the information noted above. The Valuation Team evaluates such information for incorporation into our TEV, including review of all inputs provided by the independent valuation firm. The Valuation Team then makes a recommendation to our Board of Directors as to the fair value. Our Board of Directors reviews the recommended fair value and whether it is reasonable in light of the Policy and other relevant facts and circumstances and then votes to accept or reject the Valuation Team’s recommended fair value.

A portion of our assets are, and may in the future be, comprised of debt and equity securities that are valued based on internal assessment using valuation methods approved by our Board of Directors, without the input of ICE Data Pricing and Reference Data, LLC (formerly Standard and Poor’s Securities Evaluations, Inc.) (“ICE”), or other third-party evaluators. While we believe that our debt and equity valuation methods reflect those regularly used as standards by other professionals in our industry who value equity securities, the determination of fair value for securities that are not publicly traded necessarily involves an exercise of subjective judgment, whether or not we obtain the recommendations of an independent third-party evaluator.

Our use of these fair value methods is inherently subjective and is based on estimates and assumptions regarding each security. In the event that we are required to sell a security, we may ultimately sell for an amount materially less than the estimated fair value calculated by us or ICE, or determined using TEV, or the discounted cash flow methodology. As a result, a risk exists that the Asset Coverage attributable to the Preferred Stock, including the Series E Term Preferred Stock, may be materially lower than what is calculated based upon the fair valuation of our portfolio securities in accordance with our valuation policies. See “Risk Factors—Risks Related to Our Investments— Because the loans we make and equity securities we invest in are not publicly traded, there is uncertainty regarding the value of our privately held securities that could adversely affect our determination of our NAV.” on page 15 of the accompanying prospectus.

There is a risk of delay in our redemption of the Series E Term Preferred Stock, and we may fail to redeem such securities as required by their terms.

We generally make investments in private companies whose securities are not traded in any public market. Substantially all of the investments we presently hold and the investments we expect to acquire in the future are, and will be, subject to legal and other restrictions on resale and will otherwise be less liquid than publicly traded securities. The illiquidity of our investments may make it difficult for us to obtain cash equal to the value at which we record our investments quickly if a need arises. If we are unable to obtain sufficient liquidity prior to the Mandatory Term Redemption Date or a Change of Control Triggering Event, we may be forced to engage in a partial redemption or to delay a required redemption. If such a partial redemption or delay were to occur, the market price of the Series E Term Preferred Stock might be adversely affected.

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We finance our investments with borrowed money and senior securities, which will magnify the potential for gain or loss on amounts invested and may increase the risk of investing in us.

The following table illustrates the effect of leverage on returns from an investment in our Common Stock assuming various annual returns on our portfolio, net of expenses. The calculations in the table below are hypothetical, and actual returns may be higher or lower than those appearing in the table below.

Based on our outstanding indebtedness of $107.6 million as of June 30, 2018, and the effective annual interest rate of 5.4% as of that date, aggregate liquidation preference of our Series B Term Preferred Stock of $41.4 million, aggregate liquidation preference of our Series C Term Preferred stock of $40.3 million, aggregate liquidation preference of our Series D Term Preferred stock of $57.5 million, aggregate liquidation preference of the Series E Term Preferred Stock of $65.0 million to be issued in this offering, incremental borrowings under our Credit Facility of $19.0 million, and redemption of our Series B Term Preferred Stock and Series C Term Preferred Stock with an aggregate liquidation preference of $81.7 million, our investment portfolio at fair value would have been required to experience an annual return of at least 2.3% to cover annual interest payments on our outstanding debt and dividends on the Series B, Series C, Series D and Series E Preferred Stock.

Other Risks

In addition to regulatory limitations on our ability to raise capital, the Credit Facility contains various covenants that, if not complied with, could accelerate our repayment obligations under the facility, thereby materially and adversely affecting our liquidity, financial condition, results of operations and ability to pay distributions. In addition, we are obligated to redeem our Series D Term Preferred Stock in September 2023. If we do not have sufficient funds to redeem the Series D Term Preferred Stock, or if we do not have sufficient funds remaining following such redemption, we may experience an adverse effect on our business, financial condition and results of operations and our ability to meet our payment obligations under the Credit Facility and monthly dividend obligations with respect to our Preferred Stock.

We will have a continuing need for capital to finance our loans. We are party to a credit facility, which provides us with a revolving credit line facility of $165.0 million, of which $102.0 million was drawn as of August 13, 2018 and can be expanded to a total facility amount of $250.0 million through additional commitments of existing or new lenders. The Credit Facility permits us to fund additional loans and investments as long as we are within the conditions set forth in the credit agreement and is currently scheduled to mature in November 2021.

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As a result of the Credit Facility, we are subject to certain limitations on the type of loan investments we make, including, but not limited to, restrictions on geographic concentrations, sector concentrations, loan size, dividend payout, payment frequency and status, and average life. The Credit Facility also requires us to comply with other financial and operational covenants, which require us to, among other things, maintain certain financial ratios, including asset and interest coverage, and a minimum net worth. As of August 13, 2018, we were in compliance with these covenants; however, our continued compliance with these covenants depends on many factors, some of which are beyond our control. Current market conditions have forced us to write down the value of a portion of our assets as required by the 1940 Act and fair value accounting rules. These are not realized losses, but constitute adjustment in asset values for purposes of financial reporting and for collateral value for the Credit Facility. As assets are marked down in value, the amount we can borrow on the Credit Facility decreases.

In particular, potential depreciation in the valuation of our assets, which valuation is subject to changing market conditions that remain very volatile, may affect our ability to comply with the covenants under the Credit Facility, including the minimum net worth covenant. As of June 30, 2018, our net assets were $379.8 million, up from $354.2 million at March 31, 2018. The increase in our net assets was primarily a result of unrealized appreciation over the respective periods. Additionally, the Credit Facility currently contains a performance guaranty that requires the Company to maintain (i) a minimum net worth (defined in the Credit Facility to include our mandatory redeemable term preferred stock) of the greater of $210.0 million or $210.0 million plus 50% of all equity and subordinated debt raised minus 50% of any equity or subordinated debt redeemed or retired after November 16, 2016, which equated to $222.2 million as of June 30, 2018, (ii) asset coverage with respect to senior securities representing indebtedness of at least 200% (or such higher percentage as may be set forth in Section 61 of the 1940 Act), and (iii) our status as a BDC under the 1940 Act and as a RIC under the Code. As of June 30, 2018, and as defined in the performance guaranty of the Credit Facility, we had a net worth of $514.7 million, an asset coverage ratio on our senior securities representing indebtedness of 566.8%, calculated in compliance with the requirements of Sections 18 and 61 of the 1940 Act, and an active status as a BDC and RIC. As of June 30, 2018, we were in compliance with all covenants under the Credit Facility; however, our continued compliance depends on many factors, some of which are beyond our control. Accordingly, there are no assurances that we will continue to comply with these covenants. Under the Credit Facility, we are also required to maintain our status as a BDC under the 1940 Act and as a RIC under the Code. Our failure to satisfy these covenants could result in foreclosure by our lenders, which would accelerate our repayment obligations under the facility and thereby have a material adverse effect on our business, liquidity, financial condition, results of operations and ability to pay distributions to our stockholders.

In addition, we are required to redeem all outstanding shares of Series D Term Preferred Stock on September 30, 2023, at a redemption price equal to the liquidation preference, plus an amount equal to accumulated but unpaid dividends, if any, on such shares (whether or not earned or declared, but excluding interest on such dividends) up to, but excluding, the redemption date. If we fail to redeem the Series D Term Preferred Stock pursuant to the mandatory redemption required on September 30, 2023, or in any other circumstance in which we are required to redeem the Series D Term Preferred Stock, then the fixed dividend rate of the Series D Term Preferred Stock will increase to an annual rate of 9.25% for so long as such failure continues. If we do not have sufficient funds to redeem the Series D Term Preferred Stock or if we do not have sufficient funds remaining following such redemption, we may experience an adverse effect on our business, financial condition and results of operations and our ability to meet our payment obligations under the Credit Facility and monthly dividend obligations with respect to our Preferred Stock.

Our amount of senior securities outstanding will increase as a result of this offering if we are unable to redeem shares of our Series B Term Preferred Stock and Series C Term Preferred Stock within the time period that we anticipate or at all, which could adversely affect our business, financial condition and results of operations, our ability to meet our payment obligations under the Credit Facility and our ability to meet the asset coverage requirements of the 1940 Act.

As of June 30, 2018, we had $41.4 million outstanding of Series B Term Preferred Stock, $40.3 million outstanding of Series C Term Preferred Stock, $57.5 million outstanding of Series D Term Preferred Stock,

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$102.5 million of borrowings outstanding under the Credit Facility, and a $5.1 million secured borrowing. We intend to use the proceeds from this offering to redeem all outstanding shares of the Series B Term Preferred Stock and Series C Term Preferred Stock and for other general corporate purposes. We intend to redeem the shares of Series B Term Preferred Stock and Series C Term Preferred Stock within 45 days of the completion of this offering; however, we cannot assure you that we will be able to redeem the shares of Series B Term Preferred Stock and Series C Term Preferred Stock within this time period or at all. Until such time as the Series B Term Preferred Stock and Series C Term Preferred Stock are redeemed in full using the proceeds of this offering (and, to the extent that the aggregate amount of shares of Series E Term Preferred Stock issued in this offering exceeds the aggregate amount of Series B Term Preferred Stock and Series C Term Preferred Stock currently outstanding, following such redemption of the Series B Term Preferred Stock and Series C Term Preferred Stock), our amount of senior securities that are stock outstanding will increase as a result of this offering.

The issuance of additional senior securities could have significant consequences on our future operations, including:

We may authorize, establish, create, issue and sell shares of one or more series of a class of our senior securities while shares of Series E Term Preferred Stock are outstanding without the vote or consent of the holders thereof.

While shares of Series E Term Preferred Stock are outstanding, we may, without the vote or consent of the holders thereof, authorize, establish and create and issue and sell shares of one or more series of a class of our senior securities representing stock under Section 18, as modified by Section 61, of the 1940 Act, ranking on parity with the Series E Term Preferred Stock as to payment of dividends and distribution of assets upon dissolution, liquidation or the winding up of our affairs, in addition to then outstanding shares of Series E Term Preferred Stock, including additional series of Preferred Stock, and authorize, issue and sell additional shares of any such series of Preferred Stock then outstanding or so established and created, in each case in accordance with applicable law, provided that we will, immediately after giving effect to the issuance of such additional Preferred Stock and to our receipt and application of the proceeds thereof, including to the redemption of Preferred Stock with such proceeds, have Asset Coverage as required by Sections 18 and 61 of the 1940 Act (which, as of the date hereof, is 200% and shall be 150% effective April 10, 2019, unless earlier approved by the Company’s stockholders).

Any of the above-listed factors could have an adverse effect on our business, financial condition and results of operations and our ability to meet our payment obligations under the Credit Facility and monthly dividend obligations or redemption obligations with respect to our Preferred Stock.

Our ability to meet our payment and other obligations under the Credit Facility and monthly dividend obligations with respect to our Preferred Stock depends on our ability to generate significant cash flow in the future. This, to some extent, is subject to general economic, financial, competitive, legislative and regulatory factors as well as other factors that are beyond our control. We cannot assure you that our business will generate cash flow from

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operations, or that future borrowings will be available to us under the Credit Facility or otherwise, in an amount sufficient to enable us to meet these obligations and to fund other liquidity needs. If we are not able to generate sufficient cash flow to service our obligations, we may need to refinance or restructure our debt, sell assets, reduce or delay capital investments, or seek to raise additional capital. If we are unable to implement one or more of these alternatives, we may not be able to meet our payment obligations under the Credit Facility or monthly dividend obligations with respect to our Preferred Stock.

In addition, we may issue debt securities, other evidences of indebtedness (including borrowings under the Credit Facility), senior securities representing indebtedness and senior securities that are stock up to the maximum amount permitted by the 1940 Act. The 1940 Act currently permits us, as a BDC, to issue senior securities representing indebtedness and senior securities that are stock (such as our Preferred Stock), in amounts such that our asset coverage, in accordance with Sections 18 and 61 of the 1940 Act, is at least 200% (currently) or 150% (effective April 10, 2019, unless earlier approved by the Company’s stockholders). The issuance of additional senior securities in this offering may increase the likelihood of our failing to meet the asset coverage requirements of the 1940 Act, especially while our Series B Term Preferred Stock, Series C Term Preferred Stock and Series D Term Preferred Stock remain outstanding. Our ability to pay distributions, issue senior securities or repurchase shares of our Common Stock would be restricted if the asset coverage on each of our senior securities is not at least the minimum amount required by applicable law in effect. If the aggregate value of our assets declines, we might be unable to satisfy that minimum asset coverage requirement. To satisfy the minimum asset coverage requirement in the event that we are seeking to pay a distribution, we might either have to (i) liquidate a portion of our loan portfolio to repay a portion of our indebtedness or (ii) issue Common Stock. This may occur at a time when a sale of a portfolio asset may be disadvantageous, or when we have limited access to capital markets on agreeable terms. In addition, any amounts that we use to service our indebtedness or for offering expenses will not be available for distributions to stockholders. Furthermore, if we have to issue Common Stock at a price below net asset value (“NAV”) per common share, as we have in the past upon obtaining the requisite stockholder and board approvals, any non-participating common stockholders will be subject to dilution.

We may not be permitted to declare a dividend or make any distribution to stockholders or repurchase shares until such time as we satisfy the asset coverage tests under the provisions of the 1940 Act that apply to BDCs. As a BDC, we have the ability to issue senior securities only in amounts such that our asset coverage, as defined in the 1940 Act, equals at least 200% (currently) (or 150%, effective April 10, 2019, unless earlier approved by the Company’s stockholders) after each issuance of senior securities. If the value of our assets declines, we may be unable to satisfy this test. If that happens, we may be required to sell a portion of our investments and, depending on the nature of our leverage, repay a portion of our debt at a time when such sales and/or repayments may be disadvantageous.

Regulations governing our operation as a BDC and RIC will affect our ability to raise, and the way in which we raise, additional capital or borrow for investment purposes, which may have a negative effect on our growth. As a result of the annual distribution requirement to qualify as a RIC, we may need to periodically access the capital markets to raise cash to fund new investments. We may issue senior securities representing indebtedness, including borrowing money from banks or other financial institutions, or senior securities that are stock, such as our Series B Term Preferred Stock, our Series C Term Preferred Stock, and our Series D Term Preferred Stock, only in amounts such that our asset coverage, as defined in the 1940 Act, equals at least 200% (currently) or 150% (effective April 10, 2019, unless earlier approved by the Company’s stockholders) after each such incurrence or issuance. See “Management’s Discussion and Analysis of Financial Condition and Results of Operations — Overview—Recent Developments — Small Business Credit Availability Act.” Further, we may not be permitted to declare a dividend or make any distribution to our outstanding stockholders or repurchase shares until such time as we satisfy this test. Our ability to issue different types of securities is also limited. Compliance with these requirements may unfavorably limit our investment opportunities and reduce our ability in comparison to other companies to profit from favorable spreads between the rates at which we can borrow and the rates at which we can lend. As a BDC, therefore, we intend to continuously issue equity at a rate more frequent than our privately owned competitors, which may lead to greater stockholder dilution. We have incurred leverage to generate capital to make additional investments. If the value of our assets declines, we may be unable to satisfy the asset coverage test under the

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1940 Act, which could prohibit us from paying distributions and could prevent us from qualifying as a RIC. If we cannot satisfy the asset coverage test, we may be required to sell a portion of our investments and, depending on the nature of our debt financing, repay a portion of our indebtedness at a time when such sales and repayments may be disadvantageous.

Recently-enacted legislation allows us to incur additional leverage under the 1940 Act, distinct from certain of our obligations under our Credit Facility and our three series of mandatorily redeemable preferred stock.

Historically, as a BDC, under the 1940 Act, we are generally required to maintain asset coverage of 200% for senior securities representing indebtedness (i.e., debt) or stock (i.e., preferred stock). On March 23, 2018, President Trump signed into legislation the Consolidated Appropriations Act of 2018, also known as the “omnibus spending package.” Included in Title VIII therein is the Small Business Credit Availability Act that includes certain regulations under the federal securities laws impacting BDCs. Among other items, the Small Business Credit Availability Act allows a BDC to increase the amount of debt it may incur by modifying the asset coverage percentage from 200% to 150% (subject to specific approval and disclosure requirements).

On April 10, 2018, our Board of Directors, including a “required majority” (as such term is defined in Section 57(o) of the 1940 Act) thereof, approved the modified asset coverage requirements set forth in Section 61(a)(2) of the 1940 Act, as amended by the Small Business Credit Availability Act. As a result, the Company’s asset coverage requirements for senior securities will be changed from 200% to 150%, effective one year after the date of the Board of Director’s approval; or on April 10, 2019, unless earlier approved by the Company’s stockholders. Under the current 200% asset coverage standard, we may borrow debt or issue senior securities in the amount of $1.00 for every $1.00 of equity in the Company. Starting from April 10, 2019, unless earlier approved by the Company’s stockholders, under the 150% asset coverage standard, we may borrow debt or issue senior securities in the amount of $2.00 for every $1.00 of equity in the Company. This reduction in the asset coverage ratio will allow us to double the amount of debt that we may incur and, therefore, your risk of an investment in us may increase. In addition, our management fee is based on our average gross assets, which include investments made with proceeds of borrowings, and, as a result, if we were to incur additional leverage, management fees paid to the Advisor would increase.

Notwithstanding the modified asset coverage leverage ratio under the 1940 Act described above, we currently remain subject to a minimum asset coverage requirement of 200% with respect to certain provisions of our Credit Facility and our three series of mandatorily redeemable preferred stock. If we drop below the 200% minimum asset coverage requirement, we may under certain circumstances be required to repay all outstanding indebtedness under our Credit Facility and redeem our then-outstanding term preferred stock. In addition, in the event we fall below the 200% minimum asset coverage requirement, we may need to renegotiate our Credit Facility and issue additional series of term preferred stock with a lower asset coverage requirement. Such events, if they were to occur, could have a significant adverse effect on our business, financial condition, results of operations and cash flows.

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USE OF PROCEEDS

We estimate that the net proceeds of this offering will be approximately $62.7 million, after the payment of underwriting discounts and commissions of $2.0 million and estimated offering expenses of $0.3 million payable by us. We intend to use the net proceeds from this offering along with a draw on our Credit Facility, if necessary, to redeem all outstanding shares of our Series B Term Preferred Stock and our Series C Term Preferred Stock, within 45 days of the completion of this offering. As of the date of this prospectus supplement, the aggregate redemption price of all outstanding shares of our Series B Term Preferred Stock is $41.4 million and the cost of redeeming all outstanding shares of our Series C Term Preferred Stock is $40.3 million. After such utilization, we intend to use any remaining net proceeds of the offering for other general corporate purposes. Shares of our Series B Term Preferred Stock accrue cumulative dividends at an annual rate of 6.75% and must be redeemed in full by December 31, 2021. Shares of our Series C Term Preferred Stock accrue cumulative dividends at an annual rate of 6.50% and must be redeemed in full by May 31, 2022.

We have granted the underwriters the right to purchase up to 390,000 additional shares of Series E Term Preferred Stock at the public offering price, less underwriting discounts and commissions, within 30 days of the date of this prospectus supplement solely to cover over-allotments, if any. If the underwriters exercise such option in full, the estimated net proceeds to us, after the payment of underwriting discounts and commissions of $2.3 million and estimated offering expenses of $0.3 million payable by us, will be $72.1 million. We anticipate that substantially all of the net proceeds of this offering will be utilized in the manner described above within three months of the completion of such offering. Pending such utilization, we intend to invest the net proceeds of the offering primarily in cash, cash equivalents, U.S. government securities and other high-quality debt investments that mature in one year or less from the date of investment, consistent with the requirements for continued qualification as a RIC for federal income tax purposes.

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RATIO OF EARNINGS TO COMBINED FIXED CHARGES AND DIVIDENDS ON PREFERRED STOCK

Computation of Pro Forma Ratio of Earnings to Combined Fixed Charges and Dividends on Preferred Stock After Adjustment for Issuance of the Series E Term Preferred Stock

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CAPITALIZATION

The following table sets forth our capitalization as of June 30, 2018:

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SELECTED QUARTERLY FINANCIAL DATA

The following tables set forth certain quarterly financial data for each of the eight quarters in the two years ended March 31, 2018 and the first quarter of the fiscal year ending March 31, 2019. The data was derived from our unaudited consolidated financial statements. Results for any quarter are not necessarily indicative of results for the past fiscal year or for any future quarter.

(DOLLAR AMOUNTS IN THOUSANDS, EXCEPT PER SHARE DATA)

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Regulatory Compliance

Our ability to seek external debt financing, to the extent that it is available under current market conditions, is further subject to the asset coverage limitations of the 1940 Act, which require us to have asset coverage (as defined in Sections 18 and 61 of the 1940 Act, as amended), of at least 200% (currently) or 150% (effective April 10, 2019, unless earlier approved by the Company’s stockholders) on each of our senior securities representing indebtedness and our senior securities that are stock (such as our three series of term preferred stock).

On April 10, 2018, our Board of Directors, including a “required majority” (as such term is defined in Section 57(o) of the 1940 Act) thereof, approved the modified asset coverage requirements set forth in Section 61(a)(2) of the 1940 Act, as amended by the Small Business Credit Availability Act. As a result, the Company’s asset coverage requirements for senior securities will be changed from 200% to 150%, effective one year after the date of the Board of Directors’ approval; or April 10, 2019, unless earlier approved by the Company’s stockholders. Under the current 200% asset coverage standard, we may borrow debt or issue senior securities in the amount of $1.00 for every $1.00 of equity in the Company. Starting from April 10, 2019, under the 150% asset coverage standard, we may borrow debt or issue senior securities in the amount of $2.00 for every $1.00 of equity in the Company. Notwithstanding the modified asset coverage requirement under the 1940 Act described above, we are separately subject to a minimum asset coverage requirement of 200% with respect to certain provisions of our Credit Facility and our three series of mandatorily redeemable preferred stock.

As of June 30, 2018, our asset coverage ratio on our senior securities representing indebtedness was 566.8% and our asset coverage on our senior securities that are stock was 250.2%.

Investment Highlights

During the three months ended June 30, 2018, and inclusive of non-cash transactions, we invested $29.2 million in one new portfolio company, received $32.1 million in proceeds from repayments and sales, and extended $0.9 million of follow-on investments to existing portfolio companies through revolver draws and term loans.

Investment Activity

During the three months ended June 30, 2018, the following significant transactions occurred:

The following significant investment activity occurred subsequent to June 30, 2018. Also refer to Note 13 — Subsequent Events in the accompanying Notes to Consolidated Financial Statements included elsewhere in this prospectus supplement.

Recent Developments

Registration Statement

On June 5, 2018, we filed a registration statement on Form N-2 (File No. 333-225447), which the SEC declared effective on July 13, 2018. The registration statement permits us to issue, through one or more transactions, up to

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