Filed Pursuant to Rule 424(b)(5)
Registration Number 333-255699

CALCULATION OF REGISTRATION FEE

PROSPECTUS SUPPLEMENT

(To Prospectus dated April 30, 2021)

Up to $500,000,000   IMMUNITYBIO, INC.

Common Stock

We have entered into an open market sale agreement, or the sale agreement, with Jefferies LLC, or Jefferies, relating to shares of our common stock, $0.0001 par value per share, offered by this prospectus supplement and the accompanying prospectus. In accordance with the terms of the sale agreement, we may offer and sell shares of our common stock having an aggregate offering price of up to $500,000,000 from time to time through Jefferies, acting as our sales agent.

Our common stock is listed on The Nasdaq Global Select Market under the symbol “IBRX”. The last reported sale price of our common stock on The Nasdaq Global Select Market on April 29, 2021 was $17.93 per share.

We are a “smaller reporting company” as that term is defined in Rule 12b-2 promulgated under the Securities Exchange Act of 1934, as amended, or the Exchange Act, and, as such, have elected to comply with certain reduced public company reporting requirements for this prospectus supplement and future filings.

Sales, if any, of shares of our common stock under the sale agreement may be made by any method permitted by law. Jefferies is not required to sell any specific amount of securities, but will act as our sales agent using commercially reasonable efforts to sell on our behalf all of the shares of common stock requested to be sold by us, consistent with its normal trading and sales practices, applicable state and federal laws, rules and regulations and the rules of The Nasdaq Global Select Market, on mutually agreed terms between Jefferies and us. There is no arrangement for funds to be received in any escrow, trust or similar arrangement.

Jefferies will be entitled to compensation at a commission rate of up to 3.0% of the gross proceeds of any shares of common stock sold under the sale agreement. In connection with the sale of the common stock on our behalf, Jefferies may be deemed to be an “underwriter” within the meaning of the Securities Act of 1933, as amended, or the Securities Act and the compensation of Jefferies may be deemed to be underwriting commissions or discounts. We have also agreed to provide indemnification and contribution to Jefferies with respect to certain liabilities, including liabilities under the Securities Act or the Exchange Act. See the section titled “Plan of Distribution” on page S-18 of this prospectus supplement.

Investing in our common stock involves a high degree of risk. See “Risk Factors” beginning on page S-8 of this prospectus supplement, page 4 of the accompanying prospectus and in the reports we file with the Securities and Exchange Commission, or the SEC, pursuant to the Exchange Act, incorporated by reference into this prospectus supplement, to read about factors you should consider before buying shares of our common stock.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or passed upon the accuracy or adequacy of this prospectus supplement or the accompanying prospectus. Any representation to the contrary is a criminal offense.

Prospectus Supplement dated April 30, 2021

TABLE OF CONTENTS

For investors outside the United States: we have not, and the sales agent has not, done anything that would permit this offering or possession or distribution of this prospectus supplement, the accompanying prospectus and any free writing prospectus that we have authorized for use in connection with this offering in any jurisdiction where action for that purpose is required, other than in the United States. Persons outside the United States who come into possession of this prospectus supplement, the accompanying prospectus or any free writing prospectus that we have authorized for use in connection with this offering must inform themselves about, and observe any restrictions relating to, the offering of the common stock and the distribution of this prospectus supplement, the accompanying prospectus and any free writing prospectus that we have authorized for use in connection with this offering outside the United States.

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ABOUT THIS PROSPECTUS SUPPLEMENT

This prospectus supplement and the accompanying prospectus are part of a registration statement that we have filed with the SEC utilizing a “shelf” registration process. Under the shelf registration process, we may, from time to time, offer and sell any combination of our securities described in the accompanying prospectus in one or more offerings. We are providing information to you about this offering of our common stock in two parts. The first part is this prospectus supplement, which provides you with specific information regarding the terms of this offering and our common stock, and also adds to and updates information contained in the accompanying prospectus and the documents incorporated by reference into this prospectus supplement and the accompanying prospectus. The second part is the accompanying prospectus dated April 30, 2021, which includes the documents incorporated by reference therein and provides more general information, some of which does not apply to this offering of our common stock. Generally, when we refer to the prospectus, we are referring to this prospectus supplement and the accompanying prospectus combined. In this prospectus supplement, as permitted by law, we “incorporate by reference” information from other documents that we file with the SEC. This means that we can disclose important information to you by referring you to those documents. The information incorporated by reference is considered to be a part of this prospectus supplement and the accompanying prospectus and should be read with the same care.

We provide information to you about this offering of shares of our common stock in this prospectus supplement, which describes the specific details regarding this offering. This prospectus supplement adds to, updates, and changes information contained in the accompanying prospectus and the information incorporated by reference therein with respect to this offering of our common stock. To the extent there is a conflict between the information contained in this prospectus supplement and accompanying prospectus and the information contained in any document incorporated by reference into this prospectus supplement and accompanying prospectus that was filed with the SEC before the date of this prospectus supplement or accompanying prospectus, you should rely on the information in this prospectus supplement or accompanying prospectus; provided that if any statement in one of these documents is inconsistent with a statement in another document having a later date—for example, a document incorporated by reference into this prospectus supplement—the statement in the document having the later date modifies or supersedes the earlier statement. You should assume that the information contained in this prospectus supplement is accurate as of the date on the front cover of this prospectus supplement only and that any information we have incorporated by reference or included in the accompanying prospectus or any free writing prospectus is accurate only as of the date given in the document incorporated by reference or as of the date of the prospectus or free writing prospectus, as applicable, regardless of the time of delivery of this prospectus supplement, the accompanying prospectus or free writing prospectus or any sale of our common stock. Our business, financial condition, results of operations and prospects may have changed since that earlier date. We have not, and the sales agent has not authorized anyone to provide you with any information that is different from that contained in this prospectus supplement and in the accompanying prospectus or in any free writing prospectus prepared by us or on our behalf. We and Jefferies take no responsibility for, and can provide no assurances as to the reliability of, any other information that others may give you.

We are offering to sell, and seeking offers to buy, shares of common stock only in jurisdictions where offers and sales are permitted. The distribution of this prospectus supplement and the offering of the common stock in certain jurisdictions may be restricted by law. We are not, and Jefferies is not, making an offer to sell these securities in any jurisdiction where the offer or sale is not permitted. This prospectus supplement and the accompanying prospectus do not constitute, and may not be used in connection with, an offer to sell, or a solicitation of an offer to buy, any securities offered by this prospectus supplement or the accompanying prospectus by any person in any jurisdiction in which it is unlawful for such person to make such an offer or solicitation.

Before buying any of the common stock that we are offering, we urge you to carefully read both this prospectus supplement and the accompanying prospectus and all of the information incorporated by reference herein and therein, together with the additional information described in the sections titled “Where You Can Find

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More Information” and “Incorporation of Certain Information by Reference.” These documents contain important information that you should consider when making your investment decision.

You should not consider any information in this prospectus supplement or the accompanying prospectus to be investment, legal or tax advice. You should consult your own counsel, accountants and other advisers for legal, tax, business, financial and related advice regarding the purchase of the common stock offered by this prospectus supplement. If the description of the offering varies between this prospectus supplement and the accompanying prospectus, you should rely on the information contained in this prospectus supplement.

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RISK FACTORS

Investing in our securities involves a high degree of risk. Before deciding whether to invest in our securities, you should consider carefully, among other matters, the risks and uncertainties set forth below and described under the heading “Risk Factors” on page 4 of the accompanying prospectus, and those discussed under the heading “Risk Factors.” in Exhibit 99.3 to our Current Report on Form 8-K filed with the SEC on March 10, 2021, as updated by our annual, quarterly and other reports and documents that are incorporated by reference into this prospectus, and any free writing prospectus that we have authorized for use in connection with this offering.

The risks described in these documents are not the only ones we face. There may be other unknown or unpredictable economic, business, competitive, regulatory or other factors that could harm our future results. Additional risks not presently known to us or that we currently believe are immaterial may also significantly impair our business operations. Past financial performance may not be a reliable indicator of future performance, and historical trends should not be used to anticipate results or trends in future periods. If any of these risks actually occurs, our business, financial condition, results of operations or cash flow could be harmed. This could cause the trading price of our securities to decline, resulting in a loss of all or part of your investment. Such risks may be amplified by the COVID-19 pandemic and its potential impact on our business and the global economy. Please also read carefully the section below titled “Special Note Regarding Forward-Looking Statements.”

Risks Relating to the Offering

We will need substantial additional financing to fund our operations and complete the development and commercialization of our various product candidates, and if we are unable to obtain such financing, we may be unable to complete the development and commercialization of our product candidates. Raising additional capital may cause dilution to our stockholders, restrict our operations or require us to relinquish rights to our technologies or product candidates.

Our operations have consumed substantial amounts of cash since inception and we have generated only a minimal amount of revenue. As of December 31, 2020, we had an accumulated deficit of $1.6 billion. In addition, research and development and operating costs have also been substantial and are expected to increase. A significant portion of our funding had been in the form of promissory notes representing, based on preliminary estimates, $297.5 million in indebtedness as of March 31, 2021, including a $40.0 million advance during the first quarter of 2021, held by entities affiliated with Dr. Soon-Shiong. The notes bear interest at a per annum rate ranging from 3.0% to 6.0%, with accrued and unpaid interest compounded annually and computed on the basis of 365 or 366 days. The notes provide that all outstanding principal is due and payable on September 30, 2025, and accrued and unpaid interest is payable either on the maturity date or, with respect to one of the notes, on a quarterly basis.

As of December 31, 2020, we had cash, cash equivalents and marketable securities of $97.0 million. As of March 31, 2021, based on preliminary estimates, we had cash, cash equivalents and marketable securities of $84.3 million (consisting of an estimated $44.7 million of cash and cash equivalents and an estimated $39.6 million of marketable securities). In order to complete the development of our current product candidates, and implement our business plan, we will require substantial additional financing. Furthermore, changing circumstances may cause us to increase our spending significantly faster than we currently anticipate, and we may need to raise even greater amounts of funds sooner if we choose to expand more rapidly than we presently anticipate. Moreover, our fixed expenses such as rent and other contractual commitments are substantial and are expected to increase in the future.

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As a result of continuing anticipated operating cash outflows, we believe that substantial doubt exists regarding our ability to continue as a going concern without additional funding or financial support. To date, we have principally relied on borrowings from entities affiliated with our Executive Chairman and principal stockholder, Dr. Patrick Soon-Shiong, to fund our capital requirements. However, our Executive Chairman is not required to provide any additional financing to us and could decline to provide any such additional financing on acceptable terms, or at all, at any time. We have no lines of credit or committed sources of financing; however we may have access to incremental draws on the promissory notes we have with entities associated with our Executive Chairman Dr. Patrick Soon-Shiong.

We will need to obtain additional financing to fund our future operations, including completing the development and commercialization of our product candidates. Our future funding requirements will depend on many factors, including, but not limited to:

Unless and until we can generate a sufficient amount of revenues, we expect to seek to finance future cash needs through public or private equity offerings, license agreements, debt financings, credit facilities, collaborations, strategic alliances and marketing or distribution arrangements. In that connection, we intend to issue additional shares in connection with this offering and one or more future capital raising transactions. Additional funds may not be available when we seek to raise capital or need funds on terms that are acceptable to us, or at all. We have no committed source of additional capital and if we are unable to raise additional capital in sufficient amounts or on terms acceptable to us, we may be required to delay or reduce the scope of or eliminate one or more of our research or development programs or our commercialization efforts. Our current license agreements may also be terminated if we are unable to meet the payment obligations under those agreements. As a result, we may seek to access the public or private capital markets whenever conditions are favorable, even if we do not have an immediate need for additional capital at that time.

To the extent that we raise additional capital through the sale of additional equity or convertible debt securities, your ownership interest will be diluted, and the terms may include liquidation or other preferences that

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adversely affect your rights as a stockholder. The incurrence of additional indebtedness would result in increased fixed payment obligations and could involve certain restrictive covenants, such as limitations on our ability to incur additional debt, limitations on our ability to acquire or license intellectual property rights and other operating restrictions that could adversely impact our ability to conduct our business. If we raise additional funds through strategic partnerships and alliances and licensing arrangements with third parties, we may have to relinquish valuable rights to our technologies or product candidates, or grant licenses on terms unfavorable to us.

We will have broad discretion in the use of the net proceeds from this offering and may not use them effectively.

We cannot specify with certainty the particular uses of the net proceeds we will receive from this offering. Our management will have broad discretion in the application of the net proceeds, including for any of the purposes described in the section titled “Use of Proceeds.” We intend to use the net proceeds from this offering, if any, together with other available funds, to progress our clinical development programs, fund other research and development activities, for capital expenditures and for other general corporate purposes. We may also use a portion of the net proceeds to license intellectual property or to make acquisitions or investments. Our management may spend a portion or all of the net proceeds from this offering in ways that our stockholders may not desire or that may not yield a favorable return. The failure by our management to apply these funds effectively could harm our business, financial condition, results of operations and prospects. Pending their use, we may invest the net proceeds from this offering in a manner that does not produce income or that loses value.    

It is not possible to predict the actual number of shares we will sell under the sale agreement, or the gross proceeds resulting from those sales.

Subject to certain limitations in the sale agreement and compliance with applicable law, we have the discretion to deliver instruction to the sale agent to sell shares of our common stock at any time throughout the term of the sale agreement. The number of shares that are sold through the sale agent after our instruction will fluctuate based on a number of factors, including the market price of our common stock during the sales period, the limits we set with the sale agent in any instruction to sell shares, and the demand for our common stock during the sales period. Because the price per share of each share sold will fluctuate during this offering, it is not currently possible to predict the number of shares that will be sold or the gross proceeds to be raised in connection with those sales.

The common stock offered hereby will be sold in “at the market offerings,” and investors who buy shares at different times will likely pay different prices.

Investors who purchase shares in this offering at different times will likely pay different prices and may therefor experience different levels of dilution and different outcomes in their investment results. We will have discretion, subject to market demand, to vary the timing, prices, and numbers of shares sold in this offering. In addition, subject to the final determination by our board of directors, there is no minimum or maximum sales price for shares to be sold in this offering. Investors may experience a decline in the value of the shares they purchase in this offering as a result of sales made at prices lower than the prices they paid.

You may experience future dilution as a result of future equity offerings.

We will require more capital to pursue our preclinical and clinical activities, regulatory approval and the commercialization of our products. In addition, we may also choose to raise additional capital due to market conditions or strategic considerations even if we believe we have sufficient funds for our current or future operating plans. To raise additional capital, we may in the future offer additional shares of our common stock or other securities convertible into or exchangeable for our common stock at prices that may not be the same as the

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price per share in this offering. We may sell shares or other securities in any other offering at a price per share that is less than the price per share paid by investors in this offering, and investors purchasing shares or other securities in the future could have rights superior to existing stockholders. The price per share at which we sell additional shares of our common stock, or securities convertible or exchangeable into common stock, in future transactions may be higher or lower than the price per share paid by investors in this offering.

We are a “smaller reporting company,” and the reduced disclosure requirements applicable to smaller reporting companies may make our common stock less attractive to investors.

We are a “smaller reporting company,” as defined in Rule 12b-2 under the Exchange Act. We would cease to be a smaller reporting company if we no longer had either a public float less than $250 million or annual revenues less than $100 million and a public float less than $700 million as of June 30th of the prior fiscal year, determined on an annual basis. As a smaller reporting company, we are permitted and intend to rely on exemptions from certain disclosure requirements that are applicable to other public companies that are not smaller reporting companies. We cannot predict whether investors will find our common stock less attractive as a result of our reliance on these exemptions. If some investors find our common stock less attractive as a result, there may be a less active trading market for our common stock and our stock price may be more volatile.

We do not anticipate paying any cash dividends on our capital stock in the foreseeable future. Accordingly, stockholders must rely on capital appreciation, if any, for any return on their investment.

We have never declared nor paid cash dividends on our capital stock. We currently plan to retain all of our future earnings, if any, to finance the operation, development and growth of our business. As a result, capital appreciation, if any, of our common stock will be your sole source of gain for the foreseeable future.

You may experience immediate and substantial dilution in the net tangible book value per share of the common stock you purchase.

The price per share of our common stock being offered may be higher than the net tangible book value per share of our common stock outstanding prior to this offering. Assuming that an aggregate of 27,886,224 shares are sold at a price of $17.93 per share, the last reported sale price of our common stock on The Nasdaq Global Select Market on April 29, 2021, for aggregate proceeds of $500,000,000 in this offering, and after deducting commissions and estimated aggregate offering expenses payable by us, you will suffer immediate and substantial dilution of $17.03 per share, representing the difference between the as adjusted net tangible book value per share of our common stock as of December 31, 2020 after giving effect to this offering and the assumed offering price of $17.93 per share. See the section entitled “Dilution” below for a more detailed discussion of the dilution you will incur if you purchase common stock in this offering.

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SPECIAL NOTE REGARDING FORWARD-LOOKING STATEMENTS

This prospectus supplement, the accompanying prospectus and the information and documents we incorporate herein and therein by reference, and any free writing prospectus that we have authorized for use in connection with this offering contain, and we may from time to time make, written or oral “forward-looking statements” within the meaning of Section 27A of the Securities Act and Section 21E of the Securities Exchange Act of 1934, as amended, or Exchange Act, that are based on our management’s beliefs and assumptions and on information currently available to our management. All statements other than statements of historical fact are, or may be deemed to be, forward-looking statements. Although we believe that we have a reasonable basis for each forward-looking statement contained and incorporated by reference included in this prospectus and any prospectus supplement, we caution you that these statements are based on our projections of the future that are subject to known and unknown risks, including business, regulatory, economic and competitive risks, uncertainties, contingencies, assumptions and other factors that may cause our actual results, levels of activity, performance or achievements to be materially different from any future results, levels of activity, performance or achievements expressed or implied by such forward-looking statements. Factors that might cause or contribute to a material difference include, but are not limited to, those discussed elsewhere in this prospectus, the risks discussed in our other filings with the SEC and as set forth below.

These forward-looking statements include, but are not limited to:

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In some cases, forward-looking statements can be identified by the use of forward-looking terms such as “anticipate,” “estimate,” “believe,” “continue,” “could,” “intend,” “may,” “might,” “seek,” “plan,” “potential,”

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“predict,” “should,” “will,” “expect,” “objective,” “projection,” “forecast,” “goal,” “guidance,” “outlook,” “effort,” “target,” “trajectory” or the negative of these terms or other comparable terms. However, the absence of these words does not mean that the statements are not forward-looking. These forward-looking statements are based on certain assumptions and analyses made by us in light of our experience and our perception of historical trends, current conditions and expected future developments, as well as other factors we believe are appropriate in the circumstances. Statements that “we believe” and similar statements reflect our beliefs and opinions on the relevant subject. These statements are based upon information available to us as of the date of this prospectus supplement, and although we believe such information forms a reasonable basis for such statements, such information may be limited or incomplete, and our statements should not be read to indicate that we have conducted a thorough inquiry into, or review of, all potentially available relevant information. These statements are inherently uncertain and investors are cautioned not to unduly rely upon these statements. We intend that such forward-looking statements be subject to the safe harbors created thereby. The sections in this prospectus supplement entitled “Risk Factors” and in the accompanying prospectus on page 4 “Risk Factors” and the risks discussed under the heading “Risk Factors” in Exhibit 99.3 to our Current Report on Form 8-K, filed on March 10, 2021, which are incorporated by reference in this prospectus as well as other disclosures included in this prospectus supplement or the accompanying prospectus, discuss some of the factors that could contribute to these differences.

These statements involve known and unknown risks, uncertainties and other factors that may cause our actual results, performance time frames or achievements to be materially different from any future results, performance, time frames or achievements expressed or implied by the forward-looking statements or, even if substantially realized, may not have the expected consequences to, or effects on, us. Given these risks, uncertainties and other factors, you should not place undue reliance on these forward-looking statements. Also, these forward-looking statements represent our estimates and assumptions only as of the date such forward-looking statements are made. You should read carefully this prospectus supplement, the accompanying prospectus and any related free writing prospectuses that we have authorized for use in connection with this offering, together with the information incorporated herein and therein by reference as described in the section titled “Where You Can Find More Information,” completely and with the understanding that our actual future results may be materially different from what we expect. We hereby qualify all of our forward-looking statements by these cautionary statements. Except as required by law, we assume no obligation to update or revise these forward-looking statements publicly, or to update the reasons actual results could differ materially from those anticipated in these forward-looking statements, even if new information becomes available in the future. If we do update one or more forward-looking statements, no inference should be drawn that we will make additional updates with respect to those or other forward-looking statements.

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USE OF PROCEEDS

We may issue and sell shares of our common stock having aggregate gross proceeds of up to $500,000,000 from time to time under this prospectus supplement and accompanying prospectus. Because there is no minimum offering amount required as a condition to close this offering, the actual total offering amount, commissions and proceeds to us, if any, are not determinable at this time. The amount of proceeds from this offering will depend upon the number of shares of our common stock sold and the market price at which they are sold. There can be no assurance that we will be able to sell any shares under or fully utilize the sale agreement as a source of financing.

We intend to use the net proceeds from this offering, if any, together with other available funds, to progress our clinical development programs, fund other research and development activities, for capital expenditures and for other general corporate purposes. We may also use a portion of the net proceeds to license intellectual property or to make acquisitions or investments. This expected use of our net proceeds from this offering represents our intentions based upon our current plans and business conditions, which could change in the future as our plans and business conditions evolve. The amounts and timing of our actual expenditures may vary significantly depending on numerous factors, including the progress of our product candidate development, the status of and results from clinical trials, as well as any collaborations that we may enter into with third parties for our product candidates, and any unforeseen cash needs. As of the date of this prospectus supplement, we cannot specify with certainty all of the particular uses for the net proceeds to us from this offering. As a result, our management will retain broad discretion over the timing and allocation of our net proceeds from this offering, and investors will be relying on the judgment of our management regarding the application of our net proceeds from this offering. The timing and amount of our actual expenditures will be based on many factors, including: competitive and technological developments; the progress of our clinical trials; regulatory approval of our product candidates; costs to commercialize our product candidates if approved; the anticipated growth of our business; and a number of other factors, including those listed in the section titled “Risk Factors” and in the documents incorporated by reference herein. Pending these uses, we plan to invest these net proceeds primarily in investment grade short- to intermediate-term corporate debt securities, government-sponsored securities, and foreign government bonds. The goal with respect to the investment of these net proceeds is capital preservation and liquidity so that such funds are readily available to fund our operations.

We anticipate that we will be required to raise substantial additional capital to continue to fund the clinical development of our product candidates and commercialize approved products. We expect to seek to raise additional capital through additional public or private financings which may be in the form of debt, equity, warrants or convertible securities.

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DILUTION

If you invest in this offering, your ownership interest will be diluted immediately to the extent of the difference between the public offering price per share and the as adjusted net tangible book value per share of our common stock after giving effect to this offering.

Our net tangible book value as of December 31, 2020 was $(120.0) million, or $(0.31) per share, based on the total number of shares of our common stock outstanding as of December 31, 2020. Net tangible book value per share is determined by subtracting our total liabilities from the total book value of our tangible assets and dividing the difference by the number of shares of common stock deemed to be outstanding at that date.

After giving effect to the assumed sale of 27,886,224 shares of common stock in the aggregate amount of $500,000,000 at an assumed public offering price of $17.93 per share, the last reported sale price of our common stock on April 29, 2021, and after deduction of commissions and estimated offering expenses payable by us, our as adjusted net tangible book value as of December 31, 2020 would have been approximately $368.3 million, or $0.90 per share. This represents an immediate increase in pro forma as adjusted net tangible book value of $1.21 per share to our existing stockholders and immediate dilution of $17.03 per share to new investors purchasing common stock in this offering.

The following table illustrates this dilution on a per share basis to new investors:

We may also increase or decrease the aggregate dollar amount of shares we are offering from the amount set forth above. The information discussed above is illustrative only and will adjust based on the actual public offering price, the actual number of shares that we offer in this offering, and other terms of this offering determined at the time of each offer and sale.

The foregoing table and calculations are based on 382,243,142 shares of common stock outstanding as of December 31, 2020 and excludes the following:

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In addition, unless we specifically state otherwise, all information in this prospectus supplement assumes no exercise of outstanding stock options subsequent to December 31, 2020.

To the extent that options are exercised, new options are issued under our equity incentive plans, or we issue additional shares of common stock or securities convertible or exchangeable for our common stock in the future, there will be further dilution to investors participating in this offering.

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PLAN OF DISTRIBUTION

We have entered into a sale agreement with Jefferies, under which we may offer and sell up to $500,000,000 of shares of our common stock from time to time through Jefferies acting as our sales agent.

Sales, if any, of shares of our common stock under the sale agreement may be made by any method permitted by law, including without limitation (i) by means of ordinary brokers’ transactions (whether or not solicited), (ii) to or through a market maker, (iii) directly on or through any national securities exchange or facility thereof, a trading facility of a national securities association, an alternative trading system, or any other market venue, (iv) in the over-the-counter market, (v) in privately negotiated transactions with our consent, (vi) block transactions or (vii) through a combination of any such method.

Each time we wish to issue and sell shares of our common stock under the sale agreement, we will notify the sales agent of the number of shares to be issued, the dates on which such sales are anticipated to be made, any limitation on the number of shares to be sold in any one day and any minimum price below which sales may not be made. Once we have so instructed the sales agent, unless the sales agent declines to accept the terms of such notice, the sales agent has agreed to use its commercially reasonable efforts consistent with its normal trading and sales practices to sell such shares up to the amount specified on such terms. The obligations of the sales agent under the sale agreement to sell shares of our common stock are subject to a number of conditions that we must meet. We or the sales agent may suspend the offering of shares of our common stock by notifying the other party.

The sale agreement also provides that we may also in the future enter into one or more terms agreements with the sales agent from time to time, on terms mutually satisfactory to us and the sales agent, to the extent we determine to sell shares of our common stock under the sale agreement directly to the sales agent as principal.

The settlement of sales of shares between the sales agent and us is generally anticipated to occur on the second trading day following the date on which the sale was made. Sales of shares of our common stock as contemplated in this prospectus supplement will be settled through the facilities of The Depository Trust Company or by such other means as we and the sales agent may agree upon. There is no arrangement for funds to be received in an escrow, trust or similar arrangement.

We will pay the sales agent a commission rate of up to 3.0% of the aggregate gross proceeds we receive from each sale of shares of our common stock. Because there is no minimum offering amount required as a condition to close this offering, the actual total public offering amount, commissions and proceeds to us, if any, are not determinable at this time. In addition, we have agreed to reimburse the sales agent for certain specified expenses, including the fees and disbursements of its legal counsel, under certain circumstances.

We estimate that the total expenses for the offering, excluding any commissions or expense reimbursement payable to the sales agent under the terms of the sale agreement, will be approximately $465,000. The remaining sale proceeds, after deducting any other transaction fees, will equal our net proceeds from the sale of such shares. The sales agent will provide written confirmation to us before the open on The Nasdaq Global Select Market on the day following each day on which shares of our common stock are sold under the sale agreement. Each confirmation will include the number of shares sold on that day, the aggregate gross proceeds of such sales and the proceeds to us.

In connection with the sale of shares of our common stock on our behalf, the sales agent may be deemed to be an “underwriter” within the meaning of the Securities Act, and the compensation of the sales agent

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may be deemed to be underwriting commissions or discounts. We have agreed to indemnify the sales agent against certain civil liabilities, including liabilities under the Securities Act. We have also agreed to contribute to payments the sales agent may be required to make in respect of such liabilities.

The offering of shares of our common stock pursuant to the sale agreement will terminate upon the earlier of (i) the sale of all shares of common stock subject to the sale agreement and (ii) the termination of the sale agreement as permitted therein. The sales agent may terminate the sale agreement at any time upon prior notice. We may terminate the sale agreement at any time upon prior notice.

This summary of the material provisions of the sale agreement does not purport to be a complete statement of its terms and conditions. A copy of the sale agreement is filed as an exhibit to a current report on Form 8-K filed under the Securities Exchange Act of 1934, as amended, or the Exchange Act, and incorporated by reference in this prospectus supplement.

The sales agent and its affiliates may in the future provide various investment banking, commercial banking, financial advisory and other financial services for us and our affiliates, for which services it may in the future receive customary fees. In the course of its business, the sales agent may actively trade our securities for its own account or for the accounts of customers, and, accordingly, the sales agent may at any time hold long or short positions in such securities.

A prospectus supplement and the accompanying prospectus in electronic format may be made available on a website maintained by the sales agent, and the sales agent may distribute the prospectus supplement and the accompanying prospectus electronically.

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LEGAL MATTERS

The validity of the securities offered hereby will be passed upon for us by Wilson Sonsini Goodrich & Rosati, Professional Corporation, San Diego, California. Davis, Polk & Wardwell LLP, Menlo Park, California is representing the sales agent in connection with the offering.

EXPERTS

The combined consolidated financial statements of ImmunityBio, Inc. for the years ended December 31, 2020 and 2019, appearing in ImmunityBio, Inc.’s Current Report on Form 8-K/A filed with the Securities and Exchange Commission on April 22, 2021, have been audited by Ernst & Young LLP, independent registered public accounting firm, as set forth in their report thereon, included therein, and incorporated herein by reference. Such combined consolidated financial statements are incorporated herein by reference in reliance upon such report given on the authority of such firm as experts in accounting and auditing.

The consolidated financial statements of NantKwest, Inc. appearing in NantKwest, Inc.’s Annual Report (Form 10-K) for the year ended December 31, 2020, have been audited by Ernst & Young LLP, independent registered public accounting firm, as set forth in their report thereon, included therein, and incorporated herein by reference. Such consolidated financial statements are incorporated herein by reference in reliance upon such report given on the authority of such firm as experts in accounting and auditing.

The consolidated financial statements of NantCell, Inc. (fka ImmunityBio, Inc., a private company) for the years ended December 31, 2020 and 2019, appearing in ImmunityBio, Inc.’s Current Report on Form 8-K/A filed with the Securities and Exchange Commission on April 22, 2021, have been audited by Ernst & Young LLP, independent auditors, as set forth in their report thereon, included therein, and incorporated herein by reference. Such consolidated financial statements are incorporated herein by reference in reliance upon such report given on the authority of such firm as experts in accounting and auditing.

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WHERE YOU CAN FIND MORE INFORMATION

We have filed with the SEC a registration statement on Form S-3 under the Securities Act, of which this prospectus supplement forms a part. Our SEC filings are available to the public over the Internet at the SEC’s website at www.sec.gov. In addition, our Annual Report on Form 10-K, Quarterly Reports on Form 10-Q, and Current Reports on Form 8-K, including any amendments to those reports, and other information that we file with or furnish to the SEC pursuant to Section 13(a), 14 or 15(d) of the Exchange Act can also be accessed free of charge through the investor relations page of our website located at ir.immunitybio.com. These filings will be available as soon as reasonably practicable after we electronically file such material with, or furnish it to, the SEC. Information contained on or accessible through our website is not a part of this prospectus and is not incorporated by reference herein, and the inclusion of our website address and the SEC website address in this prospectus are inactive textual references only. Information contained on our website is not part of this prospectus.

This prospectus supplement and any accompanying prospectus are part of a registration statement on Form S-3 that we have filed with the SEC and do not contain all the information we have included in the registration statement and the accompanying exhibits and schedules we have filed with the SEC. Documents establishing the terms of the offered securities are or may be filed as exhibits to the registration statement. Statements in this prospectus supplement or any accompanying prospectus about these documents are summaries and each statement is qualified in all respects by reference to the document to which it refers. You should refer to the registration statement, exhibits and schedules for a more complete description about us and the securities.

You should rely only on the information provided in, and incorporated by reference in, this prospectus supplement and the accompanying prospectus and the registration statement. We have not authorized anyone else to provide you with different information. Our securities are not being offered in any state where the offer is not permitted. The information contained in documents that are incorporated by reference in this prospectus supplement is accurate only as of the dates of those documents. Our business, financial condition, results of operations and prospects may have changed since those dates.

INCORPORATION OF CERTAIN INFORMATION BY REFERENCE

The SEC allows us to incorporate by reference the information we file with it, which means that we can disclose important information to you by referring you to another document that we have filed separately with the SEC. The information incorporated by reference is deemed to be part of this prospectus supplement, and subsequent information that we file with the SEC will automatically update and supersede that information. You should read the information incorporated by reference because it is an important part of this prospectus supplement. Any statement contained in a previously filed document incorporated by reference will be deemed to be modified or superseded for purposes of this prospectus supplement to the extent that a statement contained in this prospectus supplement modifies or replaces that statement.

We incorporate by reference the following information or documents that we have filed with the SEC (excluding those portions of any Form 8-K that are not deemed “filed” pursuant to the General Instructions of Form 8-K):

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We also incorporate by reference into this prospectus supplement additional documents that we may file with the SEC under Sections 13(a), 13(c), 14 or 15(d) of the Exchange Act prior to the completion or termination of the offering, but excluding any information deemed furnished and not filed with the SEC. Any statements contained in a previously filed document incorporated by reference into this prospectus supplement is deemed to be modified or superseded for purposes of this prospectus supplement to the extent that a statement contained in this prospectus supplement, or in a subsequently filed document also incorporated by reference herein, modifies or supersedes that statement.

This prospectus supplement may contain information that updates, modifies or is contrary to information in one or more of the documents incorporated by reference in this prospectus supplement. You should rely only on the information incorporated by reference or provided in this prospectus supplement. We have not authorized anyone else to provide you with different information. You should not assume that the information in this prospectus supplement is accurate as of any date other than the date of this prospectus supplement or the date of the documents incorporated by reference in this prospectus supplement.

We will provide to each person, including any beneficial owner, to whom this prospectus supplement is delivered, upon written or oral request, at no cost to the requester, a copy of any and all of the information that is incorporated by reference in this prospectus supplement, but not delivered with the prospectus supplement, other than exhibits to such documents unless such exhibits are specifically incorporated by reference into the documents that this prospectus supplement incorporates.

Requests for such documents should be directed to:

ImmunityBio, Inc.

Attn: Investor Relations

3530 John Hopkins Court

San Diego, CA 92121

(858) 633-0300

You may also access the documents incorporated by reference in this prospectus supplement through our website at www.immunitybio.com. Except for the specific incorporated documents listed above, no information available on or through our website shall be deemed to be incorporated in this prospectus supplement or the registration statement of which it forms a part. Inclusion of our website address in this prospectus supplement is an inactive textual reference only.

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PROSPECTUS

ImmunityBio, Inc.

ImmunityBio, Inc. may offer, from time to time,

We may from time to time, in one or more offerings, offer and sell common stock, preferred stock, debt securities, warrants to purchase common stock, preferred stock or debt securities, or any combination of the foregoing, either individually or as units comprised of one or more of the other securities.

This prospectus provides a general description of the securities we may offer. This prospectus may not be used to sell securities unless accompanied by a prospectus supplement, which will describe the method and the terms of the offering. We will provide you with the specific amount, price and terms of the applicable offered securities in one or more supplements to this prospectus. We may also authorize one or more free writing prospectuses to be provided to you in connection with these offerings. A prospectus supplement and any free writing prospectus may also add, update or change information contained in this prospectus with respect to that offering. You should read this prospectus, the information and documents incorporated, or deemed to be incorporated, by reference in this prospectus, and any applicable prospectus supplement and any related free writing prospectus carefully before you purchase any of our securities offered hereby.

Our common stock is listed on the Nasdaq Global Select Market under the symbol “IBRX.” On April 29, 2021, the last reported sale price on the Nasdaq Global Select Market was $17.93 per share. There is currently no market for the other securities we may offer.

Investing in our securities involves risks. Please carefully read the information under the headings “Risk Factors ” beginning on page 4 of this prospectus and in any similar section contained in or incorporated by reference herein, including, without limitation, Exhibit 99.3 to the Form 8-K filed on March 10, 2021, or in the applicable prospectus supplement before you invest in our securities.

NEITHER THE SECURITIES AND EXCHANGE COMMISSION NOR ANY STATE SECURITIES COMMISSION HAS APPROVED OR DISAPPROVED OF THESE SECURITIES OR DETERMINED IF THIS PROSPECTUS IS TRUTHFUL OR COMPLETE. ANY REPRESENTATION TO THE CONTRARY IS A CRIMINAL OFFENSE.

These securities may be offered and sold to or through one or more underwriters, dealers and agents, or directly to purchasers, or through a combination of these methods. If underwriters, dealers, or agents are used to sell the securities, we will name them and describe their compensation in a prospectus supplement. See the sections of this prospectus entitled “About this Prospectus” and “Plan of Distribution” for more information. No securities may be sold without delivery of this prospectus and the applicable prospectus supplement describing the method and terms of the offering of such securities.

The date of this prospectus is April 30, 2021.

Table of Contents

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ABOUT THIS PROSPECTUS

This prospectus is part of a registration statement on Form S-3 that we filed with the U.S. Securities and Exchange Commission, or the SEC, using a “shelf” registration process, as a “well-known seasoned issuer” as defined in Rule 405 under the Securities Act of 1933, as amended, or the Securities Act. Under this shelf registration process, we may, from time to time, offer or sell any combination of the securities described in this prospectus in one or more offerings.

This prospectus provides you with a general description of the securities we may offer. Each time we sell securities, we will provide a prospectus supplement that will contain specific information about the terms of that offering. We may also authorize one or more free writing prospectuses to be provided to you that may contain material information relating to these offerings. The prospectus supplement or any related free writing prospectus may also add to, update or change information contained in this prospectus and, accordingly, to the extent inconsistent, information in this prospectus is superseded by the information in the prospectus supplement. Each prospectus supplement will provide the amount, price, terms and plan of distribution relating to the securities to be sold pursuant to such prospectus supplement. For additional information on the methods of sale, you should refer to the section entitled “Plan of Distribution” in this prospectus.

No person has been authorized to give any information or make any representations in connection with this offering other than those contained or incorporated by reference in this prospectus, any accompanying prospectus supplement and any related issuer free writing prospectus in connection with the offering described herein and therein. We and any agent, underwriter or dealer take no responsibility for, and can provide no assurance as to the reliability of, any other information others may give you. Neither this prospectus nor any prospectus supplement nor any related issuer free writing prospectus shall constitute an offer to sell or a solicitation of an offer to buy offered securities in any jurisdiction in which it is unlawful for such person to make such an offering or solicitation. This prospectus does not contain all of the information included in the registration statement. For a more complete understanding of the offering of the securities, you should refer to the registration statement, including its exhibits. Statements contained in this prospectus about the provisions or contents of any agreement or other document are not necessarily complete. If the SEC’s rules and regulations require that an agreement or document be filed as an exhibit to the registration statement, please see that agreement or document for a complete description of these matters.

You should read the entire prospectus and any prospectus supplement and any related issuer free writing prospectus, as well as the documents incorporated by reference into this prospectus or any prospectus supplement or any related issuer free writing prospectus, before making an investment decision. You should also read and carefully consider the information in the documents we have referred you to in “Where You Can Find More Information” and “Incorporation of Certain Information by Reference”. Neither the delivery of this prospectus or any prospectus supplement or any issuer free writing prospectus nor any sale made hereunder shall under any circumstances imply that the information contained or incorporated by reference herein or in any prospectus supplement or issuer free writing prospectus is correct as of any date subsequent to the date hereof or of such prospectus supplement or issuer free writing prospectus, as applicable. You should assume that the information appearing in this prospectus, any prospectus supplement or any document incorporated by reference is accurate only as of the date of the applicable documents, regardless of the time of delivery of this prospectus or any sale of securities. Our business, financial condition, results of operations and prospects may have changed since that date.

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RISK FACTORS

An investment in our securities involves a high degree of risk. Prior to making a decision about investing in our securities, in addition to carefully considering the other information contained in this prospectus, in any accompanying prospectus supplement and incorporated by reference herein or therein, you should carefully consider the risks described under the heading “Risk Factors” in the applicable prospectus supplement and any related free writing prospectus, the risks discussed under the heading “Risk Factors” in Exhibit 99.3 to our Current Report on Form 8-K, filed on March 10, 2021 and the risks discussed under the heading “Risk Factors” contained in our most recent annual report on Form 10-K and in our most recent quarterly report on Form 10-Q, all of which are incorporated herein by reference, and may be amended, updated, supplemented or superseded from time to time by annual, quarterly and other reports and documents we file with the SEC in the future and any prospectus supplement related to a particular offering. The risks and uncertainties we have described are not the only ones we face. Additional risks and uncertainties not presently known to us or that we currently deem immaterial may also affect our operations. See “Where You Can Find More Information” and “Incorporation by Reference.”

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FORWARD-LOOKING STATEMENTS

This prospectus, each prospectus supplement and the information and documents we incorporate herein and therein by reference, contain, and we may from time to time make, written or oral “forward-looking statements” within the meaning of Section 27A of the Securities Act and Section 21E of the Securities Exchange Act of 1934, as amended, or the Exchange Act, that are based on our management’s beliefs and assumptions and on information currently available to our management. All statements other than statements of historical fact are, or may be deemed to be, forward-looking statements. Although we believe that we have a reasonable basis for each forward-looking statement contained and incorporated by reference in this prospectus and any prospectus supplement, we caution you that these statements are based on our projections of the future that are subject to known and unknown risks, including business, regulatory, economic and competitive risks, uncertainties, contingencies, assumptions and other factors that may cause our actual results, levels of activity, performance or achievements to be materially different from any future results, levels of activity, performance or achievements expressed or implied by such forward-looking statements. Factors that might cause or contribute to a material difference include, but are not limited to, those discussed elsewhere in this prospectus and the risks discussed in our other filings with the SEC.

In some cases, forward-looking statements can be identified by the use of forward-looking terms such as “anticipate,” “estimate,” “believe,” “continue,” “could,” “intend,” “may,” “might,” “seek,” “plan,” “potential,” “predict,” “should,” “will,” “expect,” “objective,” “projection,” “forecast,” “goal,” “guidance,” “outlook,” “effort,” “target,” “trajectory” or the negative of these terms or other comparable terms. However, the absence of these words does not mean that the statements are not forward-looking. These forward-looking statements are based on certain assumptions and analyses made by us in light of our experience and our perception of historical trends, current conditions and expected future developments, as well as other factors we believe are appropriate in the circumstances. Statements that “we believe” and similar statements reflect our beliefs and opinions on the relevant subject. These statements are based upon information available to us as of the date of this prospectus, and although we believe such information forms a reasonable basis for such statements, such information may be limited or incomplete, and our statements should not be read to indicate that we have conducted a thorough inquiry into, or review of, all potentially available relevant information. We intend that such forward-looking statements be subject to the safe harbors created thereby. The sections in this prospectus entitled “Risk Factors,” the risks discussed under the heading “Risk Factors” in Exhibit 99.3 to our Current Report on Form 8-K, filed on March 10, 2021, in “Part I—Item 1A—Risk Factors” of our most recent report on Form 10-K or “Part II—Item 1A—Risk Factors” in our Quarterly Reports on Form 10-Q which are incorporated by reference in this prospectus as well as other disclosures included in this prospectus or the supplement hereto, discuss some of the factors that could contribute to these differences.

Other unknown or unpredictable factors also could harm our results. Consequently, actual results or developments anticipated by us may not be realized or, even if substantially realized, may not have the expected consequences to, or effects on, us. Given these uncertainties, prospective investors are cautioned not to place undue reliance on such forward-looking statements. All subsequent written or oral forward-looking statements attributable to us or any person acting on our behalf are expressly qualified in their entirety by the cautionary statements contained or referred to in this section. Except as required by law, we undertake no obligation to update or revise publicly any of the forward-looking statements after the date of this prospectus. If we do update one or more forward-looking statements, no inference should be drawn that we will make additional updates with respect to those or other forward-looking statements.

This prospectus and the documents incorporated by reference in this prospectus contain market data that we obtained from industry sources, including independent industry publications. In presenting this information, we have also made assumptions based on such data and other similar sources and on our knowledge of, and our experience to date in, the markets for our products. This data involves a number of assumptions and limitations, and you are cautioned not to give undue weight to such estimates. While we believe the market data included in this prospectus is generally reliable, such information is inherently imprecise. In addition, projections,

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assumptions and estimates of our future performance and the future performance of the industry in which we operate are necessarily subject to a high degree of uncertainty and risk due to a variety of factors, including those described under the heading “Risk Factors” in this prospectus, the risks discussed under the heading “Risk Factors” in Exhibit 99.3 to our Current Report on Form 8-K, filed on March 10, 2021, and in “Part I—Item 1A—Risk Factors” of our most recent report on Form 10-K or “Part II—Item 1A—Risk Factors” of our Quarterly Reports on Form 10-Q which are incorporated by reference in this prospectus. These and other factors could cause results to differ materially from those expressed in the estimates made by the independent parties and by us.

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USE OF PROCEEDS

We will retain broad discretion over the use of the net proceeds to us from the sale of our securities under this prospectus. Unless we state otherwise in the applicable prospectus supplement, we expect to use the net proceeds that we will receive from the sale of the securities under this prospectus for general corporate purposes, including working capital, capital expenditures, funding continued research and development with respect to products and technologies, and clinical and process development and manufacturing of our product candidates. We may also use a portion of the net proceeds to license intellectual property or to make acquisitions or investments.

Pending these uses, we may invest our net proceeds from this offering primarily in investment grade short- to intermediate-term corporate debt securities, government-sponsored securities, and foreign government bonds.

The specific allocations of the proceeds we receive from the sale of our securities will be described in the applicable prospectus supplement.

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DIVIDEND POLICY

To date, we have not declared or paid any cash dividends on our capital stock. We currently intend to retain all available funds and any future earnings for use in the operation of our business and do not anticipate paying any dividends on our common stock in the foreseeable future. Any future determination to declare dividends will be made at the discretion of our board of directors and will depend on, among other factors, our financial condition, operating results, capital requirements, general business conditions and other factors that our board of directors may deem relevant.

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DESCRIPTION OF OUR CAPITAL STOCK

The following is a summary of the material provisions of the common stock and the preferred stock contained in our amended and restated certificate of incorporation and bylaws. For more detailed information, please refer to our amended and restated certificate of incorporation and bylaws, each as amended, which are included as exhibits to the registration statement of which this prospectus is part.

General

Our authorized capital stock consists of 520,000,000 shares, all with a par value of $0.0001 per share, of which:

As of March 31, 2021, we had outstanding 383,067,321 shares of common stock held of record by 62 stockholders.

In addition, as of March 31, 2021, (i) 12,614,446 shares of our common stock were subject to outstanding awards under our equity incentive plans, of which 4,978,314 shares of common stock were issuable upon exercise of options outstanding as of March 31, 2021, at a weighted average exercise price of $13.21 per share, and 7,636,132 shares of common stock were issuable upon the vesting of restricted stock units outstanding as of March 31, 2021 and (ii) 1,638,000 shares of our common stock were subject to an outstanding warrant that will become exercisable, at an exercise price of $3.24 per share, if certain performance conditions are satisfied.

Additionally, as of March 31, 2021, in connection with the acquisition of Altor, we issued CVRs under which we have agreed to pay the prior stockholders of Altor approximately $304.0 million upon successful approval of the BLA or foreign equivalent for Anktiva by December 31, 2022 and approximately $304.0 million upon the first calendar year prior to December 31, 2026 in which worldwide net sales of Anktiva exceed $1.0 billion (with the payments payable in cash or shares of our common stock or a combination of both). Dr. Soon-Shiong and his related party hold approximately $279.5 million in the aggregate of CVRs and they have both irrevocably agreed to receive shares of common stock in satisfaction of their CVRs. Of the remaining CVRs, $6.8 million will be paid in cash, and the holders of the balance of the CVRs can elect to receive either cash or our common stock for the CVRs.

Common Stock

The holders of our common stock are entitled to one vote per share on all matters to be voted on by our stockholders. Holders of our common stock have no cumulative voting rights. Subject to preferences that may be applicable to any outstanding shares of preferred stock, holders of our common stock are entitled to receive dividends, if any, as may be declared from time to time by our board of directors out of our assets which are legally available. In the event of our liquidation, dissolution or winding up, holders of our common stock are entitled to share ratably in all assets remaining after payment of all liabilities and the liquidation preferences of any of our outstanding shares of preferred stock. Holders of our common stock have no preemptive, conversion, redemption or subscription rights and there are no sinking fund provisions applicable to our common stock.

Preferred Stock

No shares of preferred stock are outstanding. Our board of directors is authorized, subject to certain limitations prescribed by law, to designate and issue up to a total of 20,000,000 shares of preferred stock, par value $0.0001 per share, without stockholder approval. Our board of directors may issue preferred stock from time to time in one or more series and fix the designations, preferences and rights of the shares of each such series and any qualifications, limitations or restrictions on the shares of each such series, including dividend rights and rates, conversion rights, voting rights, terms of redemption, liquidation preferences and the number of shares constituting any such series, any or all of which may be greater than or senior to those of the common stock.

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Our board of directors may authorize the issuance of preferred stock with voting or conversion rights that could harm the voting power or other rights of the holders of the common stock. The issuance of preferred stock, while providing flexibility in connection with possible acquisitions and other corporate purposes, could, among other things, have the effect of delaying, deferring or preventing a change in control of our company and might harm the market price of our common stock and the voting and other rights of the holders of common stock. We have no current plans to issue any shares of preferred stock.

The actual effect of any such issuance on the rights of the holders of common stock will not be known until our board of directors determines the specific rights of the holders of preferred stock; however, the potential effects of such an issuance include:

Registration Rights

Under the terms of the Registration Rights Agreement dated December 23, 2014, or the registration rights agreement, we have provided Cambridge Equities, L.P., or Cambridge, with a right to demand registration of the shares of common stock issued to Cambridge, which was amended as further described below. Dr. Soon-Shiong, chairman of our board of directors, is the sole member of the general partner of Cambridge. We have also granted to Cambridge “piggyback” registration rights exercisable at any time that allows Cambridge to include the shares of our common stock that they own in any public offering of equity securities initiated by us for our own account or the account of others (other than those public offerings pursuant to registration statements on forms that do not permit registration for resale by them). These “piggyback” registration rights are not available with respect to any shares of our common stock held by Cambridge which are eligible for resale pursuant to certain exemptions from registration under the Securities Act or that are the subject of a then-effective registration statement.

Additionally, pursuant to a voting agreement, we agreed and acknowledged that all shares of our common stock issued to certain significant stockholders in connection with our merger with NantCell, Inc. (formerly known as ImmunityBio, Inc., a private company) (and any common stock issued or issuable with respect to such shares of our common stock) shall constitute “Registrable Securities” and “Piggyback Registrable Securities” for purposes of, and be subject to the registration rights under, the registration rights agreement described above. Moreover, we agreed to increase the number of demand registration rights to which Cambridge is entitled to under the registration rights agreement from one to seven.

We have obtained a waiver of these registration rights from Cambridge in connection with the filing of this Form S-3 registration statement.

Nominating Agreement

Under the terms of the Nominating Agreement, dated June 18, 2015, between us and Cambridge, Cambridge has the right to designate one director to be nominated for election to our board of directors for as long as Cambridge and/or its affiliates directly own more than 20% of the issued and outstanding shares of our common stock, subject to adjustment for stock splits, stock dividends, recapitalizations and similar transactions. Dr. Soon-Shiong, who controls the entity that is the general partner of Cambridge and has the sole power to vote or direct to vote and the sole power to dispose or direct the disposition, was selected by Cambridge to hold this board seat. The Cambridge director nominee shall be nominated and recommended for election by our board of directors or other duly authorized committee, subject to any applicable limitations imposed by the DGCL, the board of directors’ fiduciary duties to our stockholders and any other applicable law. Cambridge’s right to have a

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designee nominated or appointed to serve on our board of directors shall automatically terminate wherever Cambridge owns less than 20% of our issued and outstanding shares of common stock.

Anti-Takeover Effects of Delaware Law and Our Amended and Restated Certificate of Incorporation and Bylaws

Provisions of the Delaware General Corporation Law, or the DGCL, our amended and restated certificate of incorporation and our bylaws may have the effect of delaying, deferring or discouraging another party from acquiring control of our company. These provisions, which are summarized below, may have the effect of discouraging takeover bids. These provisions are also designed, in part, to encourage anyone seeking to acquire control of us to negotiate first with our board of directors. We believe that the benefits of increased protection our potential ability to negotiate with an unfriendly or unsolicited acquirer outweigh the disadvantages of discouraging a proposal to acquire us, because negotiation of these proposals could result in an improvement of their terms.

Amended and Restated Certificate of Incorporation and Bylaws

Our amended and restated certificate of incorporation and our amended and restated bylaws include a number of provisions that could deter hostile takeovers or delay or prevent changes in control of our management team, including the following:

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The limitation of liability and indemnification provisions in our amended and restated certificate of incorporation, and our amended and restated bylaws may discourage stockholders from bringing a lawsuit against directors for breach of their fiduciary duties. These provisions may also have the effect of reducing the likelihood of derivative litigation against directors and officers, even though such an action, if successful, might otherwise benefit us and our stockholders. We may be adversely affected to the extent that, in a class action or direct suit, we pay the costs of settlement and damage awards against directors and officers pursuant to these indemnification provisions. Except as set forth in our periodic reports as incorporated herein by reference, there is currently no pending material litigation or proceeding involving any of our directors, officers, employees or agents for which indemnification is sought.

Transfer Agent and Registrar

The transfer agent and registrar for our common stock is American Stock Transfer & Trust Company, LLC. The transfer agent’s address is 6201 15th Avenue, Brooklyn, New York 11219, and its telephone number is (800) 937-5449.

Nasdaq Global Select Market Listing

Our common stock is listed on the Nasdaq Global Select Market under the symbol “IBRX.”

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DESCRIPTION OF THE DEBT SECURITIES

The following description, together with the additional information we include in any applicable prospectus supplement, summarizes certain general terms and provisions of the debt securities that we may offer under this prospectus. When we offer to sell a particular series of debt securities, we will describe the specific terms of the series in a supplement to this prospectus. We will also indicate in the supplement to what extent the general terms and provisions described in this prospectus apply to a particular series of debt securities.

We may issue debt securities either separately, or together with, or upon the conversion or exercise of or in exchange for, other securities described in this prospectus. Debt securities may be senior, senior subordinated or subordinated obligations and, unless otherwise specified in a supplement to this prospectus, the debt securities will be our direct, unsecured obligations and may be issued in one or more series.

The debt securities will be issued under an indenture between us and a trustee to be named in the applicable prospectus supplement. We have summarized select portions of the indenture below. The summary is not complete. The form of the indenture has been filed as an exhibit to the registration statement, and you should read the indenture for provisions that may be important to you. Capitalized terms used in the summary and not defined herein have the meanings specified in the indenture.

General

The terms of each series of debt securities will be established by or pursuant to a resolution of our board of directors and set forth or determined in the manner provided in a resolution of our board of directors, in an officer’s certificate or by a supplemental indenture. The particular terms of each series of debt securities will be described in a prospectus supplement relating to such series (including any pricing supplement or term sheet).

We can issue an unlimited amount of debt securities under the indenture that may be in one or more series with the same or various maturities, at par, at a premium, or at a discount. We will set forth in a prospectus supplement (including any pricing supplement or term sheet) relating to any series of debt securities being offered, the aggregate principal amount and the following terms of the debt securities, if applicable:

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We may issue debt securities that provide for an amount less than their stated principal amount to be due and payable upon declaration of acceleration of their maturity pursuant to the terms of the indenture. We will provide you with information on the federal income tax considerations and other special considerations applicable to any of these debt securities in the applicable prospectus supplement.

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If we denominate the purchase price of any of the debt securities in a foreign currency or currencies or a foreign currency unit or units, or if the principal of and any premium and interest on any series of debt securities is payable in a foreign currency or currencies or a foreign currency unit or units, we will provide you with information on the restrictions, elections, general tax considerations, specific terms and other information with respect to that issue of debt securities and such foreign currency or currencies or foreign currency unit or units in the applicable prospectus supplement.

Transfer and Exchange

Each debt security will be represented by either one or more global securities registered in the name of a clearing agency registered under the Exchange Act (the “Depositary”) or a nominee of the Depositary (we will refer to any debt security represented by a global debt security as a “book-entry debt security”), or a certificate issued in definitive registered form (we will refer to any debt security represented by a certificated security as a “certificated debt security”) as set forth in the applicable prospectus supplement. Except as set forth under the heading “Global Debt Securities and Book-Entry System” below, book-entry debt securities will not be issuable in certificated form.

Certificated Debt Securities. You may transfer or exchange certificated debt securities at any office we maintain for this purpose in accordance with the terms of the indenture. No service charge will be made for any transfer or exchange of certificated debt securities, but we may require payment of a sum sufficient to cover any tax or other governmental charge payable in connection with a transfer or exchange.

You may effect the transfer of certificated debt securities and the right to receive the principal of, premium and interest on certificated debt securities only by surrendering the certificate representing those certificated debt securities and either reissuance by us or the trustee of the certificate to the new holder or the issuance by us or the trustee of a new certificate to the new holder.

Global Debt Securities and Book-Entry System. Each global debt security representing book-entry debt securities will be deposited with, or on behalf of, the Depositary, and registered in the name of the Depositary or a nominee of the Depositary.

Covenants

We will set forth in the applicable prospectus supplement any restrictive covenants applicable to any issue of debt securities.

No Protection in the Event of a Change of Control

Unless we state otherwise in the applicable prospectus supplement, the debt securities will not contain any provisions which may afford holders of the debt securities protection in the event we have a change in control or in the event of a highly leveraged transaction (whether or not such transaction results in a change in control) which could adversely affect holders of debt securities.

Consolidation, Merger and Sale of Assets

We may not consolidate with or merge with or into, or convey, transfer or lease all or substantially all of our properties and assets to any person (a “successor person”) unless:

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Notwithstanding the above, any of our subsidiaries may consolidate with, merge into or transfer all or part of its properties to us.

Events of Default

“Event of Default” means with respect to any series of debt securities, any of the following:

No Event of Default with respect to a particular series of debt securities (except as to certain events of bankruptcy, insolvency or reorganization) necessarily constitutes an Event of Default with respect to any other series of debt securities. The occurrence of certain Events of Default or an acceleration under the indenture may constitute an Event of Default under certain indebtedness of ours or our subsidiaries that could be outstanding from time to time.

We will provide the trustee written notice of any Default or Event of Default within 30 days of becoming aware of the occurrence of such Default or Event of Default, which notice will describe in reasonable detail the status of such Default or Event of Default and what action we are taking or propose to take in respect thereof.

If an Event of Default with respect to debt securities of any series at the time outstanding occurs and is continuing, then the trustee or the holders of not less than 25% in principal amount of the outstanding debt securities of that series may, by a notice in writing to us (and to the trustee if given by the holders), declare to be due and payable immediately the principal of (or, if the debt securities of that series are discount securities, that portion of the principal amount as may be specified in the terms of that series) and accrued and unpaid interest, if any, on all debt securities of that series. In the case of an Event of Default resulting from certain events of bankruptcy, insolvency or reorganization, the principal (or such specified amount) of and accrued and unpaid interest, if any, on all outstanding debt securities will become and be immediately due and payable without any declaration or other act on the part of the trustee or any holder of outstanding debt securities. At any time after a declaration of acceleration with respect to debt securities of any series has been made, but before a judgment or decree for payment of the money due has been obtained by the trustee, the holders of a majority in principal amount of the outstanding debt securities of that series may rescind and annul the acceleration if all Events of Default, other than the non-payment of accelerated principal and interest, if any, with respect to debt securities of that series, have been cured or waived as provided in the indenture. We refer you to the prospectus supplement relating to any series of debt securities that are discount securities for the particular provisions relating to acceleration of a portion of the principal amount of such discount securities upon the occurrence of an Event of Default.

The indenture provides that the trustee may refuse to perform any duty or exercise any of its rights or powers under the indenture unless the trustee receives indemnity satisfactory to it against any cost, liability or

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expense which might be incurred by it in performing such duty or exercising such right or power. Subject to certain rights of the trustee, the holders of a majority in principal amount of the outstanding debt securities of any series will have the right to direct the time, method and place of conducting any proceeding for any remedy available to the trustee or exercising any trust or power conferred on the trustee with respect to the debt securities of that series.

No holder of any debt security of any series will have any right to institute any proceeding, judicial or otherwise, with respect to the indenture or for the appointment of a receiver or trustee, or for any remedy under the indenture, unless:

Notwithstanding any other provision in the indenture, the holder of any debt security will have an absolute and unconditional right to receive payment of the principal of, premium and any interest on that debt security on or after the due dates expressed in that debt security and to institute suit for the enforcement of payment.

The indenture requires us, within 120 days after the end of our fiscal year, to furnish to the trustee a statement as to compliance with the indenture. If a Default or Event of Default occurs and is continuing with respect to the securities of any series and if it is known to a responsible officer of the trustee, the trustee shall send to each holder of the securities of that series notice of a Default or Event of Default within 90 days after it occurs or, if later, after a responsible officer of the trustee has knowledge of such Default or Event of Default. The indenture provides that the trustee may withhold notice to the holders of debt securities of any series of any Default or Event of Default (except in payment on any debt securities of that series) with respect to debt securities of that series if the trustee determines in good faith that withholding notice is in the interest of the holders of those debt securities.

Modification and Waiver

We and the trustee may modify, amend or supplement the indenture or the debt securities of any series without the consent of any holder of any debt security:

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We may also modify and amend the indenture with the consent of the holders of at least a majority in principal amount of the outstanding debt securities of each series affected by the modifications or amendments. We may not make any modification or amendment without the consent of the holders of each affected debt security then outstanding if that amendment will:

Except for certain specified provisions, the holders of at least a majority in principal amount of the outstanding debt securities of any series may on behalf of the holders of all debt securities of that series waive our compliance with provisions of the indenture. The holders of a majority in principal amount of the outstanding debt securities of any series may on behalf of the holders of all the debt securities of such series waive any past default under the indenture with respect to that series and its consequences, except a default in the payment of the principal of, premium or any interest on any debt security of that series; provided, however, that the holders of a majority in principal amount of the outstanding debt securities of any series may rescind an acceleration and its consequences, including any related payment default that resulted from the acceleration.

Defeasance of Debt Securities and Certain Covenants in Certain Circumstances

Legal Defeasance. The indenture provides that, unless otherwise provided by the terms of the applicable series of debt securities, we may be discharged from any and all obligations in respect of the debt securities of any series (subject to certain exceptions). We will be so discharged upon the irrevocable deposit with the trustee, in trust, of money and/or U.S. government obligations or, in the case of debt securities denominated in a single currency other than U.S. Dollars, government obligations of the government that issued or caused to be issued such currency, that, through the payment of interest and principal in accordance with their terms, will provide

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money or U.S. government obligations in an amount sufficient in the opinion of a nationally recognized firm of independent public accountants or investment bank to pay and discharge each installment of principal, premium and interest on and any mandatory sinking fund payments in respect of the debt securities of that series on the stated maturity of those payments in accordance with the terms of the indenture and those debt securities.

This discharge may occur only if, among other things, we have delivered to the trustee an opinion of counsel stating that we have received from, or there has been published by, the United States Internal Revenue Service a ruling or, since the date of execution of the indenture, there has been a change in the applicable United States federal income tax law, in either case to the effect that, and based thereon such opinion shall confirm that, the holders of the debt securities of that series will not recognize income, gain or loss for United States federal income tax purposes as a result of the deposit, defeasance and discharge and will be subject to United States federal income tax on the same amounts and in the same manner and at the same times as would have been the case if the deposit, defeasance and discharge had not occurred.

Defeasance of Certain Covenants. The indenture provides that, unless otherwise provided by the terms of the applicable series of debt securities, upon compliance with certain conditions:

The conditions include:

No Personal Liability of Directors, Officers, Employees or Stockholders

None of our past, present or future directors, officers, employees or stockholders, as such, will have any liability for any of our obligations under the debt securities or the indenture or for any claim based on, or in respect or by reason of, such obligations or their creation. By accepting a debt security, each holder waives and

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releases all such liability. This waiver and release is part of the consideration for the issue of the debt securities. However, this waiver and release may not be effective to waive liabilities under U.S. federal securities laws, and it is the view of the SEC that such a waiver is against public policy.

Governing Law

The indenture and the debt securities, including any claim or controversy arising out of or relating to the indenture or the securities, will be governed by the laws of the State of New York.

The indenture will provide that we, the trustee and the holders of the debt securities (by their acceptance of the debt securities) irrevocably waive, to the fullest extent permitted by applicable law, any and all right to trial by jury in any legal proceeding arising out of or relating to the indenture, the debt securities or the transactions contemplated thereby.

The indenture will provide that any legal suit, action or proceeding arising out of or based upon the indenture or the transactions contemplated thereby may be instituted in the federal courts of the United States of America located in the City of New York or the courts of the State of New York in each case located in the City of New York, and we, the trustee and the holder of the debt securities (by their acceptance of the debt securities) irrevocably submit to the non-exclusive jurisdiction of such courts in any such suit, action or proceeding. The indenture will further provide that service of any process, summons, notice or document by mail (to the extent allowed under any applicable statute or rule of court) to such party’s address set forth in the indenture will be effective service of process for any suit, action or other proceeding brought in any such court. The indenture will further provide that we, the trustee and the holders of the debt securities (by their acceptance of the debt securities) irrevocably and unconditionally waive any objection to the laying of venue of any suit, action or other proceeding in the courts specified above and irrevocably and unconditionally waive and agree not to plead or claim any such suit, action or other proceeding has been brought in an inconvenient forum.

DESCRIPTION OF THE WARRANTS

We may issue warrants for the purchase of our common stock, preferred stock or debt securities or any combination thereof. Warrants may be issued independently or together with our common stock, preferred stock or debt securities and may be attached to or separate from any offered securities. Each series of warrants will be issued under a separate warrant agreement to be entered into between us and a bank or trust company, as warrant agent. This summary of some provisions of the warrants is not complete. For the terms of a particular series of warrants, you should refer to the prospectus supplement for that series of warrants and the warrant agreement for that particular series.

The particular terms of any issue of warrants will be described in the prospectus supplement relating to the issue. Those terms may include:

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Holders of equity warrants will not be entitled:

Debt warrant certificates may be exchangeable for new debt warrant certificates of different denominations. Debt warrants may be exercised at the corporate trust office of the warrant agent or any other office indicated in the prospectus supplement. Prior to the exercise of their debt warrants, holders of debt warrants will not have any of the rights of holders of the debt securities purchasable upon exercise and will not be entitled to payment of principal or any premium, if any, or interest on the debt securities purchasable upon exercise.

DESCRIPTION OF UNITS

We may issue units consisting of one or more of our common stock, preferred stock, debt securities or warrants.

The prospectus supplement relating to a particular issue of units will describe the terms of such units, including the following:

PLAN OF DISTRIBUTION

We may sell the securities from time to time pursuant to underwritten public offerings, direct sales to the public, “at the market” offerings, negotiated transactions, block trades or a combination of these methods. We may sell the offered securities from time to time:

We will identify the specific plan of distribution, including any underwriters, dealers, agents or direct purchasers and their compensation in the applicable prospectus supplement.

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LEGAL MATTERS

Certain legal matters will be passed upon for us by Wilson Sonsini Goodrich & Rosati, Professional Corporation, San Diego, California. Additional legal matters may be passed on for us, or any underwriters, dealers or agents, by counsel that we will name in the applicable prospectus supplement.

EXPERTS

The combined consolidated financial statements of ImmunityBio, Inc. for the years ended December 31, 2020 and 2019, appearing in ImmunityBio, Inc.’s Current Report on Form 8-K/A filed with the Securities and Exchange Commission on April 22, 2021, have been audited by Ernst & Young LLP, independent registered public accounting firm, as set forth in their report thereon, included therein, and incorporated herein by reference. Such combined consolidated financial statements are incorporated herein by reference in reliance upon such report given on the authority of such firm as experts in accounting and auditing.

The consolidated financial statements of NantKwest, Inc. appearing in NantKwest, Inc.’s Annual Report

(Form 10-K) for the year ended December 31, 2020, have been audited by Ernst & Young LLP, independent registered public accounting firm, as set forth in their report thereon, included therein, and incorporated herein by reference. Such consolidated financial statements are incorporated herein by reference in reliance upon such report given on the authority of such firm as experts in accounting and auditing.

The consolidated financial statements of NantCell, Inc. (fka ImmunityBio, Inc., a private company) for

the years ended December 31, 2020 and 2019, appearing in ImmunityBio, Inc.’s Current Report on Form 8-K/A filed with the Securities and Exchange Commission on April 22, 2021, have been audited by Ernst & Young LLP, independent auditors, as set forth in their report thereon, included therein, and incorporated herein by reference. Such consolidated financial statements are incorporated herein by reference in reliance upon such report given on the authority of such firm as experts in accounting and auditing.

WHERE YOU CAN FIND MORE INFORMATION

Because we are subject to the information and reporting requirements of the Exchange Act, we file annual, quarterly and current reports, proxy statements and other information with the SEC. Our SEC filings are available to the public over the Internet at the SEC’s website at www.sec.gov. In addition, our Annual Report on Form 10-K, Quarterly Reports on Form 10-Q, and Current Reports on Form 8-K, including any amendments to those reports, and other information that we file with or furnish to the SEC pursuant to Section 13(a) or 15(d) of the Exchange Act can also be accessed free of charge through the investor relations page of our website located at ir.immunitybio.com. These filings will be available as soon as reasonably practicable after we electronically file such material with, or furnish it to, the SEC. Information contained on or accessible through our website is not a part of this prospectus and is not incorporated by reference herein, and the inclusion of our website address and the SEC website address in this prospectus are inactive textual references only. Information contained on our website is not part of this prospectus.

This prospectus and any accompanying prospectus supplement are part of a registration statement on Form S-3 that we have filed with the SEC and do not contain all the information we have included in the registration statement and the accompanying exhibits and schedules we have filed with the SEC. Forms of the indenture and other documents establishing the terms of the offered securities are or may be filed as exhibits to the registration statement. Statements in this prospectus or any prospectus supplement about these documents are summaries and each statement is qualified in all respects by reference to the document to which it refers. You should refer to the registration statement, exhibits and schedules for a more complete description about us and the securities. The registration statement, exhibits and schedules are available through the SEC’s Internet site.

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INFORMATION INCORPORATED BY REFERENCE

The SEC allows us to incorporate by reference the information we file with it, which means that we can disclose important information to you by referring you to another document that we have filed separately with the SEC. The information incorporated by reference is deemed to be part of this prospectus, and subsequent information that we file with the SEC will automatically update and supersede that information. You should read the information incorporated by reference because it is an important part of this prospectus. Any statement contained in a previously filed document incorporated by reference will be deemed to be modified or superseded for purposes of this prospectus to the extent that a statement contained in this prospectus modifies or replaces that statement.

We incorporate by reference the following information or documents that we have filed with the SEC (excluding those portions of any Form 8-K that are not deemed “filed” pursuant to the General Instructions of Form 8-K):

All reports and other documents we subsequently file pursuant to Section 13(a), 13(c), 14 or 15(d) of the Exchange Act after the date of this prospectus and prior to the termination of the offering of our securities to which this prospectus relates will automatically be deemed to be incorporated by reference into this prospectus and to be part of this prospectus from the date of the filing of such reports and documents. We are not, however, incorporating by reference any documents or portions thereof that are not deemed “filed” with the SEC, including any information furnished pursuant to Item 2.02 or Item 7.01 of Form 8-K (and any related exhibits furnished with such furnished information). Any statements in any such future filings will automatically be deemed to modify and supersede any information in any document we previously filed with the SEC that is incorporated or deemed to be incorporated herein by reference to the extent that statements in the later filed document modify or replace such earlier statements. Any statement so modified or superseded shall not be deemed, except as so modified or superseded, to constitute a part of this prospectus.

We will provide without charge to each person, including any beneficial owner, to whom this prospectus is delivered, upon written or oral request, a copy of any or all documents that are incorporated by reference into this prospectus, but not delivered with the prospectus, other than exhibits to such documents unless such exhibits are specifically incorporated by reference into the documents that this prospectus incorporates. You should direct written requests to: ImmunityBio, Inc., 3530 John Hopkins Court, San Diego, California 92121, Attention: Investor Relations, or you may call us at (858) 633-0300.

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Up to $500,000,000

ImmunityBio, Inc.

Common Stock

PROSPECTUS SUPPLEMENT

April 30, 2021