TABLE OF CONTENTS INHIBRX BIOSCIENCES, INC. 11025 N. TORREY PINES ROAD, SUITE 140 LA JOLLA, CALIFORNIA 92037

INHIBRX BIOSCIENCES, INC.

11025 N. TORREY PINES ROAD, SUITE 140

LA JOLLA, CALIFORNIA 92037

Dear Inhibrx, Inc. Stockholder:

I am pleased to report that the previously announced spin-off (which we refer to as the "Spin-Off") by Inhibrx, Inc., which we refer to as "RemainCo," of its subsidiary Inhibrx Biosciences, Inc. is expected to become effective at 11:59 p.m., New York City time, on May 29, 2024. Inhibrx Biosciences, Inc., which we refer to as "SpinCo," is a Delaware corporation. As a result of a series of internal restructuring transactions to be effected by Inhibrx, Inc. prior to the distribution of SpinCo shares of common stock (which we refer to as the "Distribution") as described in this information statement, after 11:59 p.m., New York City time, on May 29, 2024, SpinCo's pipeline will be focused on multiple novel biologic therapeutic candidates, developed using our proprietary modular protein engineering platforms. SpinCo will own INBRX-105, INBRX-106, and INBRX-109, our clinical therapeutic candidates, as well as our discovery pipeline and certain corporate infrastructure currently owned by Inhibrx, Inc. SpinCo's shares of common stock, par value $0.0001 per share, which we refer to as "common stock," will be listed on the Nasdaq Global Market under the symbol "INBX." As described in this information statement, the Distribution is subject to the satisfaction or waiver by RemainCo and SpinCo of certain conditions, including satisfaction or waiver of the conditions precedent in the Agreement and Plan of Merger, dated as of January 22, 2024 (which we refer to as the "Merger Agreement"), by and among Inhibrx, Inc., Aventis Inc., a Pennsylvania corporation (which we refer to as "Acquirer") and a wholly-owned subsidiary of Sanofi S.A., and Art Acquisition Sub, Inc., a Delaware corporation (which we refer to as "Merger Sub") and a wholly-owned subsidiary of Acquirer, and in the Separation and Distribution Agreement, dated as of January 22, 2024 (which we refer to as the "Distribution Agreement"), by and among Inhibrx, Inc., SpinCo and Acquirer. The Merger Agreement provides for the acquisition by Acquirer of RemainCo through the merger of Merger Sub with and into RemainCo (which we refer to as the "Merger").

Holders of record of RemainCo's shares of common stock as of the close of business, New York City time, on May 17, 2024, which will be the record date, will receive one share of SpinCo common stock for every four shares of RemainCo common stock held. No action is required by any RemainCo stockholder to receive shares of SpinCo common stock. RemainCo stockholders will not be required either to pay anything for the new shares or to surrender any shares of RemainCo common stock.

In the Distribution, RemainCo will distribute, on a pro rata basis, to its stockholders as of the record date 92% of the issued and outstanding shares of SpinCo common stock that it owns as of the time of the Distribution and RemainCo will retain 8% of the issued and outstanding shares of SpinCo common stock as of the time of the Distribution. No fractional shares of SpinCo common stock will be issued. If you otherwise would be entitled to a fractional share you will receive a check for the cash value thereof, which generally will be taxable to you. In due course, you will be provided with information to enable you to compute your tax bases in both RemainCo and SpinCo shares of common stock.

The enclosed information statement describes the Distribution and contains important information about SpinCo. I suggest that you read it carefully. For more information on the Merger, see Inhibrx, Inc.'s Proxy Statement on Schedule 14A filed with the Securities and Exchange Commission (File No. 001-39452). If you have any questions regarding the Distribution, please contact Inhibrx, Inc.'s transfer agent, Continental Stock Transfer & Trust Company, at 1 State Street 30th Floor, New York, New York 10004.

Chief Executive Officer

Inhibrx Biosciences, Inc.

INFORMATION STATEMENT

Inhibrx Biosciences, Inc.

Distribution of Common Stock

(par value $0.0001 per share)

This information statement is being furnished to Inhibrx, Inc.'s stockholders in connection with the distribution (the "Distribution") by Inhibrx, Inc. ("RemainCo") to holders of its shares of common stock of 92% of the issued and outstanding shares of common stock of Inhibrx Biosciences, Inc. ("SpinCo"). Prior to such Distribution, we will enter into a series of internal restructuring transactions (the "Separation") with Inhibrx, Inc., pursuant to which we will own the assets and liabilities associated with INBRX-105, INBRX-106, and INBRX-109, including the discovery pipeline, and certain corporate infrastructure currently owned by Inhibrx, Inc. (the "SpinCo Business"). As described in this information statement, the Spin-Off is subject to the satisfaction or waiver by RemainCo and SpinCo of certain conditions, including satisfaction or waiver of the conditions precedent included in the Agreement and Plan of Merger, dated as of January 22, 2024 (the "Merger Agreement"), by and among Inhibrx, Inc., Aventis Inc., a Pennsylvania corporation (which we refer to as "Acquirer") and a wholly-owned subsidiary of Sanofi S.A., and Art Acquisition Sub, Inc., a Delaware corporation (which we refer to as "Merger Sub") and a wholly-owned subsidiary of Acquirer, and the Separation and Distribution Agreement, dated as of January 22, 2024 (the "Distribution Agreement"), by and among Inhibrx, Inc., SpinCo and Acquirer.

The Merger Agreement provides for the acquisition by Acquirer of RemainCo (the "Merger"), which will be accomplished through the merger of Merger Sub with and into RemainCo, with RemainCo continuing as the surviving company.

Our shares of common stock will be distributed to holders of RemainCo's shares of common stock of record as of the close of business, New York City time, on May 17, 2024, which will be the record date. Each holder of shares of RemainCo common stock will receive one share of SpinCo common stock for every four shares of RemainCo common stock held on the record date.

The Distribution will be effective at 11:59 p.m., New York City time, on May 29, 2024. For RemainCo stockholders who own shares of RemainCo common stock in registered form, the transfer agent will credit their shares of SpinCo common stock to book entry accounts established to hold their shares of RemainCo common stock. Our distribution agent will send these stockholders a statement reflecting their shares of SpinCo common stock ownership shortly after May 29, 2024. For stockholders who own shares of RemainCo common stock through a broker or other nominee, their shares of SpinCo common stock will be credited to their accounts by the broker or other nominee. Stockholders will receive cash in lieu of fractional shares of our common stock. The Distribution will be taxable. See "The Separation and Distribution - Certain U.S. Federal Income Tax Consequences."

No stockholder approval of the Distribution is required or sought, except in connection with Inhibrx, Inc.'s Proxy Statement on Schedule 14A filed with the Securities and Exchange Commission (File No. 001-39452). We are not asking you for any other proxy, and you are requested not to send us any additional proxy. RemainCo stockholders will not be required to pay any cash or deliver any other consideration for our shares of common stock to be received by them in the Distribution, or to surrender or to exchange shares of RemainCo common stock in order to receive our shares of common stock, or to take any other action in connection with the Distribution. There is currently no trading market for our shares of common stock. We have applied to list our shares of common stock on the Nasdaq Global Market under the symbol "INBX," which is currently the symbol for the shares of common stock of Inhibrx, Inc. We expect that our shares of common stock will be temporarily listed on the Nasdaq Global Market under the symbol "INXB" until the business day after the completion of the Merger.

Following the Distribution and prior to the closing of the Merger, pursuant to the terms of RemainCo's 2023 Warrants (as defined herein), holders of RemainCo's 2023 Warrants outstanding as of the record date will receive SpinCo Warrants exercisable for up to an aggregate of 991,849 shares of SpinCo common stock.

IN REVIEWING THIS INFORMATION STATEMENT, YOU SHOULD CAREFULLY CONSIDER THE MATTERS DESCRIBED UNDER THE CAPTION "RISK FACTORS" BEGINNING ON PAGE 11.

WE ARE AN EMERGING GROWTH COMPANY AS DEFINED IN THE JUMPSTART OUR BUSINESS STARTUPS ACT OF 2012 AND A SMALLER REPORTING COMPANY AND WE CANNOT BE CERTAIN IF THE REDUCED REPORTING REQUIREMENTS APPLICABLE TO EMERGING GROWTH COMPANIES AND SMALLER REPORTING COMPANIES WILL MAKE OUR SHARES OF COMMON STOCK LESS ATTRACTIVE TO INVESTORS. REFER TO "RISK FACTORS - RISKS RELATED TO OWNERSHIP OF OUR COMMON STOCK."

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

THIS INFORMATION STATEMENT DOES NOT CONSTITUTE AN OFFER TO SELL OR THE SOLICITATION OF AN OFFER TO BUY ANY SECURITIES.

Inhibrx, Inc. stockholders with inquiries related to the Distribution should contact Inhibrx, Inc.'s transfer agent, Continental Stock Transfer & Trust Company, at 1 State Street 30th Floor, New York, New York 10004.

The date of this information statement is May 24, 2024.

Unless otherwise indicated or the context otherwise requires, references in this information statement to:

"Acquirer" refers to Aventis Inc., a Pennsylvania corporation and a wholly-owned subsidiary of Sanofi S.A.;

"agonist" refers to an agent that activates a receptor to produce a biological response;

"apoptosis" refers to the process of programmed cell death;

"bivalent" refers to having two binding sites;

the "board of directors" or "our board of directors" refers to the board of directors of the Company;

the "bylaws" refers to our bylaws that will become effective as part of the Distribution, the form of which is filed as an exhibit to our registration statement on Form 10 of which this information statement is a part;

the "certificate of incorporation" refers to our certificate of incorporation that will become effective as part of the Distribution, the form of which is filed as an exhibit to our registration statement on Form 10 of which this information statement is a part;

"chondrosarcoma" refers to a type of bone cancer that starts in cartilage cells;

the "Company," "SpinCo," "we," "us," and "our," unless otherwise specified, refer to Inhibrx Biosciences, Inc. (a newly formed holding company) and its direct and indirect subsidiaries after giving effect to the Separation and Distribution;

"Ewing sarcoma" refers to a type of cancer of the bone or soft tissue that typically occurs in children and young adults;

"hepatoxicity" refers to liver damage;

"hexavalent" refers to having six binding sites;

"hyper-clustering" refers to aggregating a high number of receptors above a certain threshold;

"immunogenicity" refers to an immune response to an agent;

"INBRX-101" refers to a precisely engineered recombinant human AAT-Fc fusion protein therapeutic candidate that Inhibrx is developing for the treatment of patients with AATD and aGvHD;

"INBRX-105" refers to a precisely engineered multi-specific sdAb-based therapeutic candidate that is designed to agonize 4-1BB selectively in the presence of PD-L1, which is typically found in the tumor microenvironment and associated lymphoid tissues;

"INBRX-106" refers to a hexavalent OX40 agonist, currently being investigated as a single agent and in combination with Keytruda, a PD-1 blocking checkpoint inhibitor, in patients with locally advanced or metastatic solid tumors;

"INBRX-109" refers to a precisely engineered tetravalent therapeutic candidate targeting death-receptor 5, or DR5, a TNFRSF member, also known as tumor necrosis factor-related apoptosis-inducing ligand, or TRAIL, receptor 2;

the "Inhibrx Equity Incentive Plan" and the "Inhibrx, Inc. 2017 Plan" refer to the Inhibrx, Inc.'s 2017 Employee, Director and Consultant Equity Incentive Plan;

the "Inhibrx Stock Options" refers to the options to purchase shares of common stock of Inhibrx, Inc. outstanding immediately prior to the Distribution;

"ligand" refers to an agent that naturally interacts with a receptor;

the "Merger" refers to the acquisition by Acquirer of RemainCo through the merger of Merger Sub with RemainCo;

"multivalent" refers to having two or more binding sites;

"Nasdaq" refers to The Nasdaq Stock Market LLC;

"pharmacodynamic" refers to the study of the biochemical and physiologic effects of drugs in the body;

"pharmacokinetics" refers to the study of the duration of exposure of a drug in the body following administration;

"RemainCo" refers to Inhibrx, Inc., a Delaware corporation, and its direct and indirect subsidiaries, prior to the closing of the Distribution, or to Inhibrx, Inc., a Delaware corporation, and its direct and indirect subsidiaries, following the closing of the Distribution, depending on the context;

"RemainCo Compensation Committee" refers to the compensation committee of the board of directors of RemainCo as in existence prior to the Distribution;

"RemainCo Stock Options" refers to the options to purchase shares of common stock of RemainCo outstanding immediately after the Distribution;

the "Separation" refers to a series of internal reorganization transactions that RemainCo will undertake prior to the Distribution, pursuant to which, among other transactions, SpinCo will hold, directly or indirectly through its subsidiaries, the SpinCo Business and RemainCo will hold, directly or indirectly through its subsidiaries, the RemainCo Business;

the "SpinCo Warrants" refers to Inhibrx Biosciences, Inc.'s warrants to purchase up to an aggregate of 991,849 shares of Inhibrx Biosciences, Inc.'s common stock at a per share exercise price of $0.0001 to be received by holders of RemainCo's 2023 Warrants pursuant to the terms of the RemainCo 2023 Warrants;

the "Spin-Off" or the "Distribution" refers to the transaction in which RemainCo will distribute to its stockholders 92% of the issued and outstanding shares of our common stock as of the time of the Distribution;

"stockholders" refers to stockholders of RemainCo or SpinCo, depending on the context;

"tetravalent" refers to having four binding sites;

"unresectable" refers to being unable to remove with surgery;

"valency" refers to the number of binding units that an agent has; and

"warrantholders" refers to warrantholders of Inhibrx, Inc.

the "2020 Warrants" refers to Inhibrx, Inc.'s warrants to purchase 7,354 shares of Inhibrx, Inc.'s common stock at a per share exercise price of $17.00 (subject to adjustment) issued by Inhibrx, Inc. in 2020;

the "2022 Warrants" refers to Inhibrx, Inc.'s warrants to purchase 40,000 shares of Inhibrx, Inc.'s common stock at a per share exercise price of $45.00 (subject to adjustment) issued by Inhibrx, Inc. in 2022;

the "2023 Warrants" refers to Inhibrx, Inc.'s pre-funded warrants to purchase 6,714,636 shares of Inhibrx, Inc.'s common stock at a per share exercise price of $0.0001 issued by Inhibrx, Inc. in 2023;

BASIS OF PRESENTATION

SpinCo was incorporated on January 8, 2024 under the laws of the State of Delaware as a direct, wholly-owned subsidiary of Inhibrx, Inc. and has had no significant operations or activity other than its initial issuance of shares for a nominal consideration and entry into the Distribution Agreement. Prior to the Distribution, and pursuant to the Separation, Inhibrx, Inc. will undergo an internal restructuring that will generally result in (a) RemainCo directly or indirectly owning, assuming or retaining those assets and liabilities primarily related to Inhibrx, Inc.'s INBRX-101 (which we refer to as the "RemainCo Business") and (b) SpinCo directly or indirectly owning, assuming or retaining those assets and liabilities primarily related to Inhibrx, Inc.'s platform for the research, development, manufacture and commercialization of INBRX-105, INBRX-106 and INBRX-109 (which we refer to as the "SpinCo Business"). Where we describe in this information statement our business activities, including in the supplemental historical combined financial statements of SpinCo, we do so as if these transfers have already occurred.

As a result of the Distribution, RemainCo's stockholders will own 92% of the issued and outstanding shares of SpinCo common stock as of the time of the Distribution and RemainCo will retain 8% of the issued and outstanding shares of SpinCo common stock as of the time of the Distribution. Additionally, following the Distribution, holders of the SpinCo Warrants will have the right to exercise their SpinCo Warrants for up to an aggregate of 991,849 shares of SpinCo common stock. Immediately following and in connection with the Distribution, a wholly-owned subsidiary of Acquirer will merge with and into RemainCo.

Except as otherwise indicated, all of the information in this information statement does not reflect an additional 4,000,000 shares of common stock reserved for future grants under our new equity incentive plan (the "Omnibus Incentive Plan"). See "Executive Compensation - Equity Compensation Plan Information - Post-Spin-Off SpinCo Omnibus Incentive Plan."

The Separation and Distribution is being treated as a reverse spin-off for financial accounting and reporting purposes in accordance with ASC 505-60, Spinoffs and Reverse Spinoffs. Notwithstanding the legal form of the Spin-Off described elsewhere in this information statement, because a wholly-owned subsidiary of Acquirer will merge with and into RemainCo immediately following the Distribution, no senior management of Inhibrx, Inc. will be retained by RemainCo following the Distribution, and the relative size of SpinCo's operations relative to the RemainCo Business, we consider SpinCo as the accounting spinnor of RemainCo, and the accounting successor to Inhibrx, Inc.

The disposal of the RemainCo Business does not meet the criteria to be presented as discontinued operations. As the RemainCo Business does not meet the definition of a business as defined by ASC 805, Business Combinations, because substantially all of the fair value of the gross assets transferred is concentrated in one asset, a gain will be recognized for the difference between the fair value and carrying value of the disposed assets in accordance with ASC 845, Nonmonetary Transactions.

We have determined that Inhibrx, Inc. represents the predecessor entity to SpinCo. Therefore, the historical financial statements presented herein and in our future filings, with respect to periods prior to the Separation and Distribution, will be represented by the historical consolidated financial statements of Inhibrx, Inc. The financial information furnished in the "Unaudited Pro Forma Condensed Consolidated Financial Statements" section presents SpinCo's operations by removing the assets, liabilities, revenues and expenses legally being divested related to the RemainCo Business from the historical financial statements of Inhibrx, Inc., as well as incremental autonomous entity adjustments necessary to present SpinCo as if it were a historically standalone entity. Additionally, we have also provided the historical combined financial statements and related notes of SpinCo and Management's Discussion and Analysis of Financial Condition and Results of Operations of SpinCo, each on a supplemental basis.

Refer to the "Unaudited Pro Forma Condensed Consolidated Financial Statements" section for further details on the basis of presentation included elsewhere within this information statement.

Certain percentages and other figures provided and used in this information statement may not add up to 100% due to the rounding of individual components.

QUESTIONS AND ANSWERS ABOUT THE SEPARATION AND DISTRIBUTION

The following is a brief summary of the terms of the Separation and Distribution. Please see "The Separation and Distribution" for a more detailed description of the matters described below.

What is the Separation and Distribution?

The Separation is the method by which Inhibrx, Inc. will separate the businesses of SpinCo from Inhibrx Inc.'s other business, creating two separate, publicly traded companies. The Separation will generally result in (i) RemainCo directly or indirectly owning, assuming or retaining those assets and liabilities primarily related to Inhibrx Inc.'s INBRX-101 and (ii) SpinCo directly or indirectly owning, assuming or retaining those assets and liabilities primarily related to Inhibrx, Inc.'s platform for the research, development, manufacture and commercialization of INBRX-105, INBRX-106 and INBRX-109.

In the Distribution, RemainCo will distribute, on a pro rata basis, to its stockholders as of the record date 92% of our issued and outstanding shares of common stock that it owns as of the time of the Distribution. Following the Distribution, we will be a separate company from RemainCo, and RemainCo will retain 8% of the issued and outstanding shares of our common stock as of the time of the Distribution. The number of shares of RemainCo common stock you own will not change as a result of the Distribution.

What is being distributed in the Distribution?

Approximately 13,100,190 shares of our common stock will be distributed in the Distribution, based upon the number of shares of RemainCo common stock outstanding as of April 29, 2024. The shares of SpinCo's common stock to be distributed by RemainCo will constitute 92% of our issued and outstanding shares of common stock as of the time of the Distribution. For more information on the shares of common stock being distributed in the Distribution, see "Description of Our Capital Stock."

What will holders of RemainCo common stock receive in the Distribution?

Holders of shares of RemainCo common stock will receive a distribution of one share of SpinCo common stock for every four shares of RemainCo common stock held by them on the record date. For a more detailed description, see "The Separation and Distribution."

What is the record date for the Distribution?

Record ownership will be determined as of the close of business, New York City time, on May 17, 2024, which we refer to as the record date. The person in whose name shares of RemainCo common stock are registered at the close of business on the record date is the person to whom the shares of SpinCo's common stock will be issued in the Distribution.

When will the Distribution occur?

We expect that our shares of common stock will be distributed by the distribution agent, on behalf of RemainCo, effective at 11:59 p.m., New York City time, on May 29, 2024, which we refer to as the "Distribution date."

What will the relationship between RemainCo and us be following the Distribution?

Following the Distribution, we will be a public company and RemainCo will retain 8% of the issued and outstanding shares of our common stock as of the time of the Distribution. In connection with the Separation and the Distribution, we and Inhibrx, Inc. entered into a Distribution Agreement for the purpose of accomplishing, among other things, the Separation of the business of SpinCo and the Distribution of 92% of our issued and outstanding shares of common stock as of the time of the Distribution to RemainCo's common stockholders. On or prior to the Distribution date, we will enter into a transition services agreement with RemainCo (the "Transition Services Agreement"),

pursuant to which we will provide certain transition services to RemainCo, and a pharmacovigilance agreement with RemainCo (the "Pharmacovigilance Agreement"), pursuant to which the parties will implement processes and procedures for sharing information as required for each party's compliance with its regulatory and pharmacovigilance responsibilities. Under the Distribution Agreement, each of RemainCo and SpinCo agrees to indemnify, defend and hold harmless the other party, and its affiliates and certain representatives, from and after the Distribution date, from losses in connection with, among other things, (i) the liabilities assigned to, or retained by, the other party, as applicable, or (ii) the breach by such party of the Distribution Agreement. Each of RemainCo and SpinCo agreed to release the other party from, among other things, any and all liabilities existing or arising from any acts or events occurring or failing to occur on or prior to the Distribution, including in connection with the Separation, the Distribution or any other transactions contemplated under the Distribution Agreement and the Transition Services Agreement, and each of RemainCo and SpinCo agreed not to bring any proceeding or claim against the other party in respect of such liabilities. We will also be party to other arrangements with RemainCo.

See "Certain Relationships and Related Party Transactions - Policies and Procedures on Related Party Transactions" for a discussion of the policy that will be in place for dealing with potential conflicts of interest that may arise from our ongoing relationship with RemainCo.

What do I have to do to participate in the Distribution?

No action is required on the part of RemainCo stockholders. Stockholders of RemainCo on the record date for the Distribution are not required to pay any cash or deliver any other consideration, including any shares of RemainCo common stock, for shares of our common stock distributable to them in the Distribution.

How will fractional shares be treated in the Distribution?

If you would be entitled to receive a fractional share of our common stock in the Distribution, you will instead receive a cash payment. See "The Separation and Distribution - Manner of Effecting the Distribution" for an explanation of how the cash payments will be determined.