# EDGAR Filing Document

**Accession Number:** 0001840233
**File Stem:** 0001193125-26-048934
**Filing Date:** 2026-2
**Character Count:** 232665
**Document Hash:** 520e54b1b182d543dc51f229531780b0
**Contains OCR:** False
**Source Format:** 

## Filing Content

## Filing Summary
**0001193125-26-048934.hdr.sgml**: 20260212

**ACCESSION NUMBER**: 0001193125-26-048934

**CONFORMED SUBMISSION TYPE**: 424B5

**PUBLIC DOCUMENT COUNT**: 4

**FILED AS OF DATE**: 20260212

**DATE AS OF CHANGE**: 20260212

**FILER**: 

**COMPANY DATA:**
- **COMPANY CONFORMED NAME:** Xilio Therapeutics, Inc.
- **CENTRAL INDEX KEY:** 0001840233
- **STANDARD INDUSTRIAL CLASSIFICATION:** PHARMACEUTICAL PREPARATIONS [2834]
- **ORGANIZATION NAME:** 03 Life Sciences
- **EIN:** 851623397
- **STATE OF INCORPORATION:** DE
- **FISCAL YEAR END:** 1231

**FILING VALUES:**
- **FORM TYPE:** 424B5
- **SEC ACT:** 1933 Act
- **SEC FILE NUMBER:** 333-285703
- **FILM NUMBER:** 26627209

**BUSINESS ADDRESS:**
- **STREET 1:** 828 WINTER STREET
- **CITY:** WALTHAM
- **STATE:** MA
- **ZIP:** 02451
- **BUSINESS PHONE:** 617-833-1027

**MAIL ADDRESS:**
- **STREET 1:** 828 WINTER STREET
- **CITY:** WALTHAM
- **STATE:** MA
- **ZIP:** 02451

##### [**Table of Contents**](#toc)
**Filed Pursuant to Rule 424(b)(5) <br>Registration No. 333-285703** 

**PROSPECTUS SUPPLEMENT** 

**(To Prospectus dated May 8, 2025)**![LOGO](g74783g01a01.jpg)

**Pre-Funded Warrants to Purchase 74,780,300 Shares of Common Stock** 

We are offering pre-funded warrants to purchase up to 74,780,300 shares of our common stock pursuant to this prospectus supplement. The pre-funded warrants have an exercise price of $0.0001 per share and will be immediately exercisable for one share of common stock, subject to the beneficial ownership limitations described in the section "Description of Pre-Funded Warrants." This prospectus supplement also relates to the offering of the shares of our common stock issuable upon the exercise of such pre-funded warrants.

Our common stock is listed on the Nasdaq Capital Market under the symbol "XLO." On February 11, 2026, the last reported sale price of our common stock on the Nasdaq Capital Market was $0.535 per share. There is no established public trading market for the pre-funded warrants, and we do not expect a market to develop. We do not intend to list the pre-funded warrants on the Nasdaq Capital Market, any other national securities exchange or any other recognized trading system.

---

| | | |
|:---|:---|:---|
|  | **Per<br>Pre-Funded**<br>**Warrant** | **Total** |
|  Offering price | $0.5349 | $39999982 |
|  Underwriting discounts and commissions<sup>(1)</sup> | $0.0321 | $2400448 |
|  Proceeds, before expenses, to us | $0.5028 | $37599534 |

---

(1) See the section titled "Underwriting" beginning on page S-24 for a description of all compensation payable to the underwriter.

**Investing in our securities involves a high degree of risk. Before making an investment decision, please read the information under the heading "[Risk Factors](#supptoc74783_6)" beginning on page S-11 of this prospectus supplement and in the documents incorporated by reference into this prospectus supplement.** 

**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. Any representation to the contrary is a criminal offense.** 

The underwriter expects to deliver the pre-funded warrants against payment on or about February 13, 2026. See "Underwriting" for details.

The pre-funded warrants will be delivered to purchasers in certificated form.

*Sole Bookrunner* 

**Leerink Partners** 

**The date of this prospectus supplement is February 11, 2026.** 

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##### [**Table of Contents**](#toc)
**TABLE OF CONTENTS** 

**PROSPECTUS SUPPLEMENT** 

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| | |
|:---|:---|
|  [ABOUT THIS PROSPECTUS SUPPLEMENT](#supptoc74783_1) | S-2 |
|  [MARKET, INDUSTRY AND OTHER DATA](#supptoc74783_2) | S-4 |
|  [PROSPECTUS SUMMARY](#supptoc74783_3) | S-5 |
|  [THE OFFERING](#supptoc74783_4) | S-7 |
|  [SPECIAL NOTE REGARDING FORWARD-LOOKING STATEMENTS](#supptoc74783_5) | S-9 |
|  [RISK FACTORS](#supptoc74783_6) | S-11 |
|  [USE OF PROCEEDS](#supptoc74783_7) | S-14 |
|  [DILUTION](#supptoc74783_8) | S-15 |
|  [DESCRIPTION OF PRE-FUNDED WARRANTS](#supptoc74783_9) | S-17 |
|  [MATERIAL U.S. FEDERAL TAX CONSIDERATIONS FOR NON-U.S. HOLDERS](#supptoc74783_10) | S-19 |
|  [UNDERWRITING](#supptoc74783_11) | S-24 |
|  [LEGAL MATTERS](#supptoc74783_12) | S-30 |
|  [EXPERTS](#supptoc74783_13) | S-30 |
|  [WHERE YOU CAN FIND MORE INFORMATION](#supptoc74783_14) | S-31 |
|  [INCORPORATION OF CERTAIN INFORMATION BY REFERENCE](#supptoc74783_15) | S-31 |

---

**PROSPECTUS** 

---

| | |
|:---|:---|
|  [ABOUT THIS PROSPECTUS](#tx74783_1) | 1 |
|  [WHERE YOU CAN FIND MORE INFORMATION](#tx74783_2) | 2 |
|  [INCORPORATION BY REFERENCE](#tx74783_3) | 3 |
|  [CAUTIONARY NOTE REGARDING FORWARD-LOOKING STATEMENTS](#tx74783_4) | 4 |
|  [ABOUT XILIO THERAPEUTICS, INC.](#tx74783_5) | 6 |
|  [RISK FACTORS](#tx74783_6) | 7 |
|  [USE OF PROCEEDS](#tx74783_7) | 8 |
|  [DESCRIPTION OF CAPITAL STOCK](#tx74783_8) | 9 |
|  [DESCRIPTION OF DEBT SECURITIES](#tx74783_9) | 16 |
|  [DESCRIPTION OF WARRANTS](#tx74783_10) | 26 |
|  [DESCRIPTION OF UNITS](#tx74783_11) | 28 |
|  [FORMS OF SECURITIES](#tx74783_12) | 29 |
|  [PLAN OF DISTRIBUTION](#tx74783_13) | 31 |
|  [LEGAL MATTERS](#tx74783_14) | 34 |
|  [EXPERTS](#tx74783_15) | 34 |

---

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##### [**Table of Contents**](#toc)
**ABOUT THIS PROSPECTUS SUPPLEMENT** 

This document is in two parts. The first part is this prospectus supplement, which describes the specific terms of this offering and also supplements and updates information contained in the accompanying prospectus and the documents incorporated by reference herein. The second part, the accompanying prospectus, provides more general information. Generally, when we refer to this prospectus, we are referring to both parts of this document combined. To the extent there is a conflict between the information contained in this prospectus supplement and the information contained in the accompanying prospectus or any document incorporated by reference therein filed prior to the date of this prospectus supplement, you should rely on the information in this prospectus supplement; 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 in the accompanying prospectus—the statement in the document having the later date modifies or supersedes the earlier statement.

We further note that the representations, warranties and covenants made by us in any agreement that is filed as an exhibit to any document that is incorporated by reference herein were made solely for the benefit of the parties to such agreement, including, in some cases, for the purpose of allocating risk among the parties to such agreements, and should not be deemed to be a representation, warranty or covenant to you. Moreover, such representations, warranties or covenants were accurate only as of the date when made. Accordingly, such representations, warranties and covenants should not be relied on as accurately representing the current state of our affairs.

We have not, and Leerink Partners has not, authorized anyone to provide any information other than that contained or incorporated by reference in this prospectus supplement, in the accompanying prospectus or in any free writing prospectus prepared by or on behalf of us or to which we have referred you. Neither we nor Leerink Partners take any responsibility for, and can provide no assurance as to the reliability of, any other information that others may give you.

This prospectus supplement, the accompanying prospectus and any such free writing prospectus do not constitute an offer to sell, or a solicitation of an offer to purchase, the securities offered by this prospectus supplement, the accompanying prospectus and any such free writing prospectus in any jurisdiction to or from any person to whom or from whom it is unlawful to make such offer or solicitation of an offer in such jurisdiction. You should assume that the information appearing in this prospectus supplement, the accompanying prospectus and the documents incorporated by reference herein and in any free writing prospectus that we have authorized for use in connection with this offering is accurate only as of the date of those respective documents. It is important for you to read and consider all information contained in this prospectus supplement and in the accompanying prospectus, including the documents incorporated by reference herein and therein, in making your investment decision. You should also read and consider the information in the documents to which we have referred you in the sections entitled "Where You Can Find More Information" and "Incorporation by Reference" in this prospectus supplement and in the accompanying prospectus.

Other than in the United States, no action has been taken that would permit a public offering of the securities offered by this prospectus supplement in any jurisdiction where action for that purpose is required. The securities offered by this prospectus supplement may not be offered or sold, directly or indirectly, nor may this prospectus or any other offering material or advertisements in connection with the offer and sale of any such securities be distributed or published in any jurisdiction, except under circumstances that will result in compliance with the applicable rules and regulations of that jurisdiction. Persons into whose possession this prospectus supplement and accompanying prospectus comes are advised to inform themselves about and to observe any restrictions relating to the offering and the distribution of this prospectus supplement and accompanying prospectus.

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When we refer to "Xilio Therapeutics," "Xilio," "we," "our," "us" and the "Company" in this prospectus, we mean Xilio Therapeutics, Inc. and its consolidated subsidiaries unless otherwise specified. When we refer to "you," we mean the potential purchasers of the securities we may offer under this prospectus supplement.

Xilio Therapeutics and its associated logos are some of our trademarks and tradenames used in this prospectus. This prospectus also includes trademarks, tradenames and service marks that are the property of other organizations. Solely for convenience, our trademarks and tradenames referred to in this prospectus may appear without the <sup>®</sup> and <sup>™</sup> symbol, but those references are not intended to indicate, in any way, that we will not assert, to the fullest extent under applicable law, our rights, or the right of the applicable licensor to these trademarks and tradenames.

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**MARKET, INDUSTRY AND OTHER DATA** 

This prospectus supplement, including the information incorporated by reference, may contain estimates, projections and other information concerning our industry, our business, and the market for immuno-oncology therapies, as well as data regarding market research, estimates and forecasts prepared by our management. Information that is based on estimates, forecasts, projections, market research or similar methodologies is inherently subject to uncertainties and actual events or circumstances may differ materially from events and circumstances that are assumed in any such information. Unless otherwise expressly stated, we obtained any such industry, business, market and other data from reports, research surveys, studies and similar data prepared by market research firms and other third parties, industry, medical and general publications, government data and similar sources. In some cases, we may not expressly refer to the sources from which this data is derived. In that regard, when we refer to one or more sources of this type of data in any paragraph, you should assume that other data of this type appearing in the same paragraph is derived from the same sources, unless otherwise expressly stated or the context otherwise requires.

This industry, business, market and other information involves a number of assumptions and limitations, and you are cautioned not to give undue weight to such estimates. We have not independently verified any such third-party information and cannot assure you of its accuracy or completeness. Although we are responsible for all of the disclosure contained in this prospectus supplement and we believe any market position, market opportunity, market size and other information included or incorporated by reference in this prospectus supplement is reliable, such information is inherently imprecise. In addition, projections, 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 in the section titled "Risk Factors" and elsewhere in this prospectus supplement or in the documents incorporated by reference herein. 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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**PROSPECTUS SUMMARY** 

*This summary does not contain all of the information you should consider before buying our securities. You should read the entire prospectus carefully, especially the "Risk Factors" section beginning on page S-11, our most recent annual report on Form 10-K, our most recent quarterly report on Form 10-Q and our consolidated financial statements and the related notes incorporated by reference into this prospectus, before deciding to invest in our securities.* 

**Overview** 

We are a clinical-stage biotechnology company discovering and developing tumor-activated, or masked, immuno-oncology ("I-O") therapies with the goal of significantly improving outcomes for people living with cancer without the systemic side effects of current I-O treatments. We are leveraging our proprietary platform to advance a pipeline of novel, tumor-activated I-O molecules that are designed to optimize the therapeutic index by localizing anti-tumor activity within the tumor microenvironment, including masked antibodies, bispecifics, cytokines and immune cell engagers. Current I-O therapies have curative potential for patients with cancer. However, their potential is significantly curtailed by systemic toxicity that results from activity of the therapeutic molecule outside the tumor microenvironment. Our molecules are engineered to localize activity within the tumor microenvironment with minimal systemic effects, resulting in the potential to achieve enhanced anti-tumor activity and increasing the population of patients who may be eligible to receive our medicines.

**Corporate Information** 

We are a Delaware corporation that was incorporated on June 18, 2020, under the name Xilio Therapeutics, Inc. We maintain a website at the following address: www.xiliotx.com. The information contained on, or that can be accessed through, our website is not incorporated by reference into this prospectus, and any reference to our website address is intended to be an inactive textual reference only.

**Implications of Being an Emerging Growth Company and a Smaller Reporting Company** 

We are an "emerging growth company" ("EGC"), as defined in the Jumpstart Our Business Startups Act of 2012 (the "JOBS Act"). We may remain an EGC until December 31, 2026, although if the market value of our common stock that is held by non-affiliates exceeds $700.0 million as of any June 30 before that time or if we have annual gross revenues of $1.235 billion or more in any fiscal year, we would cease to be an EGC as of December 31 of the applicable year. We also would cease to be an EGC if we issue more than $1.0 billion of non-convertible debt over a three-year period. For so long as we remain an EGC, we are permitted and intend to rely on exemptions from certain disclosure requirements that are applicable to other public companies that are not EGCs. These exemptions include:

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• being permitted to provide only two years of audited financial statements, in addition to any required unaudited
interim financial statements, with correspondingly reduced "Management's Discussion and Analysis of financial Condition and Results of Operations" disclosure;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• not being required to comply with the auditor attestation requirements in the assessment of our internal control
over financial reporting;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• not being required to comply with any requirement that may be adopted by the Public Company Accounting Oversight
Board regarding mandatory audit firm rotation or a supplement to the auditor's report providing additional information about the audit and the financial statements;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• reduced disclosure obligations regarding executive compensation; and

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• exemptions from the requirements of holding a nonbinding advisory vote on executive compensation and stockholder
approval of any golden parachute payments not previously approved.

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We are also a "smaller reporting company" as defined in the Securities Act and Exchange Act. We may continue to be a smaller reporting company even after we are no longer an EGC, which would allow us to take advantage of many of the same exemptions from disclosure requirements, including reduced disclosure obligations regarding executive compensation. In addition, if we are a smaller reporting company with less than $100.0 million in annual revenue, we would not be required to comply with the auditor attestation requirements of Section 404 of the Sarbanes-Oxley Act of 2002.

As a result, the information in this prospectus and that we provide to our investors in the future may be different than what you might receive from other public reporting companies.

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**THE OFFERING** 

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| | |
|:---|:---|
| **Pre-funded warrants**  | We are offering pre-funded warrants to purchase up to 74,780,300 shares of our common stock. Each pre-funded warrant is exercisable for one share of our common stock. The purchase price of each pre-funded warrant is $0.5349. Each pre-funded warrant has an exercise price of $0.0001 per share and will be exercisable from the date of issuance until fully exercised, subject to a beneficial ownership limitation. See "Description of Pre-Funded Warrants." This prospectus supplement also relates to the offering of the shares of our common stock issuable upon exercise of such pre-funded warrants. |

---

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| | |
|:---|:---|
| **Common stock to be outstanding after this offering**  | 148,237,502 shares of common stock, assuming all of the pre-funded warrants being issued in this offering are exercised for cash. |

---

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| | |
|:---|:---|
| **Use of proceeds**  | We estimate that our net proceeds from the sale of pre-funded warrants in this offering will be approximately $37.1 million, after deducting the underwriting discounts and commissions and estimated offering expenses payable by us. |

---

We intend to use the net proceeds from this offering to advance the development of our product candidates and the balance, if any, for working capital requirements and other general corporate purposes. See "Use of Proceeds" on page S-14.

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| | |
|:---|:---|
| **Risk factors**  | Investing in our securities involves a high degree of risk. You should read the "Risk Factors" section of this prospectus and in the documents incorporated by reference in this prospectus for a discussion of factors to consider before deciding to purchase shares of our securities. |

---

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| | |
|:---|:---|
| **Nasdaq Capital Market symbol**  | "XLO" |

---

The number of shares of common stock to be outstanding after this offering is based on 73,457,202 shares of common stock outstanding as of February 11, 2026, and excludes:

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• 39,014,093 shares of our common stock issuable upon the exercise of stock options to purchase common stock that
were outstanding as of February 11, 2026, with a weighted-average exercise price of $1.03 per share;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• 222,750 shares of our common stock issuable upon the vesting of restricted stock units that were outstanding and
unvested as of February 11, 2026;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• 119,032,116 shares of our common stock issuable upon the exercise of pre-funded warrants to purchase common stock that were outstanding as of February 11, 2026, with an exercise price of $0.0001 per share;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• 2,631 shares of our common stock issuable upon the exercise of a warrant to purchase common stock that was
outstanding as of February 11, 2026, with an exercise price of $9.50 per share;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• 48,207,815 shares of our common stock issuable upon the exercise of Series C common stock warrants to purchase
common stock that were outstanding as of February 11, 2026, with an exercise price of $0.75 per warrant;

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&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• 4,994,377 shares of our common stock reserved for issuance pursuant to future awards under our 2021 Stock
Incentive Plan (the "2021 Plan") as of February 11, 2026;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• 750,000 shares of our common stock reserved for issuance pursuant to future awards under our 2022 Inducement
Stock Incentive Plan (the "2022 Inducement Plan") as of February 11, 2026; and

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• 1,838,509 shares of our common stock reserved for issuance pursuant to future awards under our 2021 Employee
Stock Purchase Plan (the "ESPP") as of February 11, 2026.

In addition, unless we specifically state otherwise, all information in this prospectus supplement reflects and assumes:

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• no exercise of the outstanding stock options or warrants (including pre-funded warrants) described above; and

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• full exercise of the pre-funded warrants being issued in this offering
for cash.

The information in this prospectus supplement does not reflect the issuance of up to $9.5 million of shares of our common stock that remain available for sale as of the date of this prospectus supplement under our "at-the-market" program with Leerink Partners. As of the date of this prospectus supplement, we have not sold any shares of our common stock under the at-the-market facility.

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**SPECIAL NOTE REGARDING FORWARD-LOOKING STATEMENTS** 

This prospectus and the documents incorporated by reference herein contain forward-looking statements within the meaning of the U.S. Private Securities Litigation Reform Act of 1995 that involve substantial risks and uncertainties. All statements, other than statements of historical facts, contained in this prospectus and the documents incorporated by reference herein are forward-looking statements. In some cases, you can identify forward-looking statements by words such as "aim," "anticipate," "believe," "contemplate," "continue," "could," "estimate," "expect," "intend," "may," "might," "plan," "potential," "predict," "project," "should," "target," "would," or the negative of these words or other comparable terminology, although not all forward-looking statements contain these identifying words. These forward-looking statements include, but are not limited to, statements about:

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• the initiation, timing, progress and results of our research and development programs, including preclinical
studies and clinical trials;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• our estimates regarding expenses, future revenue and capital requirements and our expectations regarding our
ability to fund our operating expenses and capital expenditure requirements with our cash and cash equivalents;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• our ability to establish and maintain collaborations and strategic partnerships and realize the expected benefits
of such arrangements, including our collaboration agreement with AbbVie Group Holdings Limited ("AbbVie"), our license agreement with Gilead Sciences, Inc. ("Gilead"), and our clinical collaboration with F. Hoffmann-La Roche Ltd;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• our expectations regarding milestones, option-related fees and other contingent payments under our collaboration
agreement with AbbVie and our license agreement with Gilead;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• the potential receipt of up to $36.2 million in additional gross proceeds if the outstanding Series C common
stock warrants issued in connection with our June 2025 follow-on public offering are exercised;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• our ability to secure sufficient additional capital or implement other strategies needed to alleviate the
substantial doubt about our ability to continue as a going concern;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• the potential advantages and benefits of our current and future product candidates, including our beliefs
regarding the potential benefits of our current and future product candidates in combination with other agents;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• our strategic plans to research, develop and, if approved, subsequently commercialize any product candidates we
may develop;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• our ability to identify additional products, product candidates or technologies with significant potential that
are consistent with our research, development and commercial objectives;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• our manufacturing capabilities and strategy, including our reliance on third parties to manufacture our current
or future product candidates;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• our expectations regarding our ability to obtain and maintain intellectual property protection for our product
candidates;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• the timing of and our ability to submit investigational new drug applications or biologic license applications
for, and, if cleared or approved, maintain such regulatory applications or approvals for our product candidates;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• our commercialization and marketing capabilities and strategy related to our product candidates, if approved;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• the rate and degree of market acceptance of our product candidates, if approved;

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&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• our estimates regarding the addressable patient population and potential market opportunity for our current and
future product candidates;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• developments relating to or impacting our competitors and our industry, including the impact of current or future
government laws and regulations on us, third parties with whom we do business and our industry;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• the impact of current or future government laws and regulations on us or third parties with whom we do business
and our industry;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• our competitive position and expectations regarding developments and projections relating to our current or
future competitors and any competing therapies that are or become available;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• our expectations regarding the time during which we will be an emerging growth company under the JOBS Act;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• the impact of general economic conditions, including inflation and the imposition of new or revised global trade
tariffs;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• our anticipated use of the proceeds from this offering; and

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• other risks and uncertainties, including those listed under the section titled "Risk Factors" and the
documents incorporated by reference herein.

In addition, 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 while 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 an exhaustive inquiry into, or review of, all potentially available relevant information. These statements are inherently uncertain and you are cautioned not to unduly rely upon these statements.

Any forward-looking statements in this prospectus or the documents incorporated by reference herein reflect our current views with respect to future events or to our future financial performance and involve known and unknown risks, uncertainties and other important factors that may cause our actual results, performance or achievements to be materially different from any future results, performance or achievements expressed or implied by these forward-looking statements. We may not actually achieve the plans, intentions or expectations disclosed in our forward-looking statements, and you should not place undue reliance on our forward-looking statements. Actual results or events could differ materially from the plans, intentions and expectations disclosed in the forward-looking statements we make. We have included important factors in the cautionary statements included in this prospectus and the documents incorporated by reference herein, particularly in the sections entitled "Risk Factors", that could cause actual results or events to differ materially from the forward-looking statements that we make. Given these uncertainties, you should not place undue reliance on these forward-looking statements. Our forward-looking statements do not reflect the potential impact of any future acquisitions, mergers, dispositions, joint ventures or investments we may make or enter into.

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**RISK FACTORS** 

*You should consider carefully the risks described below and discussed under the section captioned "Risk Factors" contained in our most recent annual report on Form 10-K, as updated by our subsequent filings under the Exchange Act, each of which is incorporated by reference in this prospectus in their entirety, together with other information in this prospectus, and the information and documents incorporated by reference in this prospectus, and any free writing prospectus that we have authorized for use in connection with this offering before you make a decision to invest in our securities. If any of the following events actually occur, our business, operating results, prospects or financial condition could be materially and adversely affected. This could cause the trading price of our common stock to decline and you may lose all or part of your investment. The risks described below are not the only ones that we face. Additional risks not presently known to us or that we currently deem immaterial may also affect our business operations.* 

**Risks Relating to this Offering** 

***If you purchase securities in this offering, you will suffer immediate dilution in the book value of your investment.***

The offering price of the pre-funded warrants is substantially higher than the pro forma as adjusted net tangible book value per share of our common stock. Therefore, if you purchase pre-funded warrants in this offering, you will pay a price per pre-funded warrant that substantially exceeds our pro forma as adjusted net tangible book value per share after giving effect to this offering. Based on an offering price of $0.5349 per pre-funded warrant, plus the $0.0001 per share exercise price of each pre-funded warrant, you will experience immediate dilution of $0.2978 per share of common stock, representing the difference between our pro forma as adjusted net tangible book value per share as of September 30, 2025 after giving effect to this offering and the offering price. To the extent shares subsequently are issued under outstanding options or warrants you will incur further dilution. See the section entitled "Dilution" below for a more detailed illustration of the dilution you would incur if you participate in this offering.

***We have broad discretion over the use of our cash and cash equivalents, including any net proceeds we receive in this offering, and may not use them effectively.***

Our management will have broad discretion in the application of the net proceeds from this offering and you will not have the opportunity as part of your investment decision to assess whether the net proceeds are being used appropriately. Our management might not spend the net proceeds in ways that improve our results of operations or enhance the value of our common stock. The failure by our management to apply these funds effectively could result in financial losses that could have a material adverse effect on our business, cause the price of our common stock to decline and delay the development of our product candidates. Pending their use, we may invest the net proceeds from this offering in a manner that does not produce income or that loses value. See "Use of Proceeds."

***If a significant portion of our total outstanding shares are sold into the market, the market price of our common stock could drop significantly, even if our business is doing well.***

We currently have on file with the SEC a universal shelf registration statement on Form S-3 which allows us to offer and sell up to $250.0 million of a variety of securities, including common stock, preferred stock, debt securities, units or warrants from time to time pursuant to one or more offerings at prices and terms to be determined at the time of sale. In connection with the filing of our registration statement on Form S-3, we entered into a Sales Agreement with Leerink Partners LLC, as sales agent, pursuant to which we may offer and sell shares of our common stock from time to time having an aggregate offering price of up to $9.5 million under an "at-the-market" offering program. As of the date of this prospectus supplement, we have not sold any shares of our common stock under our "at-the-market" offering program. Sales of a substantial number of shares of our common stock by Leerink Partners LLC pursuant to the Sales Agreement, under our universal shelf registration statement or otherwise could also dilute our stockholders.

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

In order 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. We cannot assure you that we will be able to sell shares or other securities in any other offering at a price per share that is equal to or greater 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 other securities convertible into or exchangeable for our common stock in future transactions may be higher or lower than the price per share in this offering.

***We do not intend to pay dividends in the foreseeable future.***

We have never paid cash dividends on our common stock. We currently intend to retain our future earnings, if any, to finance the operation and growth of our business and currently do not plan to pay any cash dividends in the foreseeable future. As a result, only appreciation of the price of our common stock will provide a return to stockholders for the foreseeable future.

***There is no public market for the pre-funded warrants being offered in this offering.***

There is no established public trading market for the pre-funded warrants being offered in this offering, and we do not expect a market to develop. In addition, we do not intend to list the pre-funded warrants on the Nasdaq Capital Market or any other national securities exchange or nationally recognized trading systems. Without an active trading market, the liquidity of the pre-funded warrants will be limited.

***Except for the right to participate in certain dividends and distributions, holders of pre-funded warrants purchased in this offering will have no rights as common stockholders until such holders exercise their pre-funded warrants and acquire our common stock.***

Until holders of the pre-funded warrants acquire shares of our common stock upon exercise of such pre-funded warrants, except for the right to participate in certain dividends and distributions, such holders will have no rights with respect to the shares of our common stock underlying such pre-funded warrants. Upon exercise of the pre-funded warrants, the holders thereof will be entitled to exercise the rights of common stockholders only as to matters for which the record date occurs after the exercise date.

***We will not receive any meaningful amount of, or potentially any, additional funds upon the exercise of the pre-funded warrants; however, any exercise would increase the number of shares eligible for future resale in the public market and result in dilution to our stockholders.***

Each pre-funded warrant will be exercisable until it is fully exercised and by means of payment of the nominal cash purchase price upon exercise or by way of a cashless exercise, meaning that the holder may not pay a cash purchase price upon exercise, but instead would receive upon such exercise the number of shares of our common stock determined according to the formula set forth in the pre-funded warrant. Accordingly, we will not receive any meaningful, or potentially any, additional funds upon the exercise of the pre-funded warrants. To the extent such pre-funded warrants are exercised, additional shares of common stock will be issued for nominal or no additional consideration, which will result in dilution to the then existing holders of our common stock and will increase the number of shares eligible for resale in the public market.

***Significant holders or beneficial holders of shares of our common stock may not be permitted to exercise the pre-funded warrants that they hold.***

The exercisability of the pre-funded warrants is subject to beneficial ownership limitations, as described in "Description of Pre-Funded Warrants." As a result, you may not be able to exercise your pre-funded warrants for shares of our common stock at a time when it would be financially beneficial for you to do so. In such circumstance,

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you could seek to sell your pre-funded warrants to realize value, but you may be unable to do so in the absence of an established trading market for the pre-funded warrants.

***We have a special meeting of stockholders scheduled to approve a reverse stock split of our common stock to regain compliance with the Nasdaq continued listing requirements. The reverse stock split, if approved, may not have the intended effect and could have a materially adverse effect on our business.***

On February 23, 2026, we will hold a special meeting of stockholders to adopt and approve an amendment to our restated certificate of incorporation, as amended, to effect a reverse stock split within a range of not less than 1-for-2 and not greater than 1-for-30, with the exact ratio within such range and the implementation and timing of such reverse stock split to be determined by our board of directors. Only stockholders of record as of January 13, 2026 are entitled to vote at the special meeting. The market price per share of our common stock post-reverse stock split may not remain in excess of the $1.00 minimum bid price per share, as required by Nasdaq, or we may fail to meet the other requirements for continued listing on Nasdaq, including the minimum value of listed securities, which may result in in the delisting of our common stock from the Nasdaq Capital Market. Additionally, the reverse stock split could be viewed negatively by the market and other factors, which may adversely affect the market price of our common stock.

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**USE OF PROCEEDS** 

We estimate that we will receive net proceeds from this offering of approximately $37.1 million, after deducting the underwriting discounts and commissions and estimated offering expenses payable by us. We will receive nominal proceeds, if any, upon exercise of the pre-funded warrants.

As of December 31, 2025, we had cash and cash equivalents of $137.5 million.

We intend to use the net proceeds from this offering, together with existing cash and cash equivalents, to:

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• advance XTX501, a bispecific PD-1/masked IL-2, through IND enabling studies, submit an IND application and initiate a planned Phase 1 clinical trial;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• advance our masked T cell engager programs for PSMA, CLDN18.2 and STEAP1to advance at least two of these programs
into initial IND-enabling studies;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• and the balance, if any, to fund our working capital requirements and for other general corporate purposes

Based on our current plans, we believe our cash and cash equivalents, together with the net proceeds to us from this offering, but excluding any potential payments under our existing collaboration and partnership agreements with AbbVie and Gilead and the exercise of up to $36.1 million in outstanding Series C warrants, will be sufficient to enable us to fund our operating expenses and capital expenditure requirements through the end of 2027. However, we have based this estimate on an anticipated offering size and other assumptions that may prove to be wrong, and we could exhaust our available capital resources sooner than we anticipate. See the "Risk Factors" section of this prospectus supplement and the documents incorporated by reference for a discussion of the risks affecting our business that could have an adverse effect on our available capital resources.

This expected use of the 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 timing and progress of our development efforts, the status of and results from clinical trials, the development obligations under our collaboration agreements, the timing of regulatory submissions, as well as any collaboration, licensing or similar transactions that we may enter into with third parties for our product candidates and any unforeseen cash needs. As a result, our management will have broad discretion over the use of proceeds from this offering. We may find it necessary or advisable to use the net proceeds from this offering for other purposes, and we will have broad discretion in the application of net proceeds.

Pending application of the net proceeds as described above, we intend to invest the net proceeds in a variety of capital preservation investments including short-term, investment-grade, interest-bearing instruments, certificates of deposit or direct or guaranteed obligations of the U.S. government.

The cash and cash equivalents information as of December 31, 2025 is a preliminary estimate based on unaudited information and management estimates for the year ended December 31, 2025, is not a comprehensive statement of our financial results as of and for the fiscal year ended December 31, 2025, and may change. Our independent registered public accounting firm has not conducted an audit or review of, and does not express an opinion or any other form of assurance with respect to, this preliminary estimate.

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**DILUTION** 

Our historical net tangible book value as of September 30, 2025 was approximately $(8.1) million, or $(0.1562) per share. Our historical net tangible book value per share is determined by dividing our total tangible assets, less total liabilities, by the number of shares of our common stock outstanding as of September 30, 2025.

Our pro forma net tangible book value as of September 30, 2025 was approximately $26.2 million, or $0.1362 per share. Our pro forma net tangible book value is the amount of our total tangible assets less our total liabilities, after giving effect to (i) an aggregate 92,278,707 pre-funded warrants in lieu of shares of common stock issued and outstanding as of September 30, 2025 (and assuming the full exercise of the pre-funded warrants), (ii) the exercise of Series B common stock warrants after September 30, 2025 and prior to the date of this prospectus supplement for an aggregate of 14,117,906 shares of common stock and 34,089,909 pre-funded warrants in lieu of shares of common stock, and (iii) net proceeds of approximately $34.3 million in connection with such exercises. Pro forma net tangible book value per share represents our pro forma net tangible book value divided by the total number of shares of common stock outstanding as of September 30, 2025, after giving effect to the pro forma adjustments described above.

After giving further effect to the pro forma adjustments described above, our issuance and sale of pre-funded warrants to purchase up to 74,780,300 shares of common stock in this offering at the offering price of $0.5349 per pre-funded warrant, and after deducting the underwriting discounts and commissions and estimated offering expenses payable by us (and assuming the full exercise of the pre-funded warrants offered hereby), our pro forma as adjusted net tangible book value as of September 30, 2025 would have been approximately $63.3 million, or $0.2371 per share. This represents an immediate increase in pro forma as adjusted net tangible book value of $0.1009 per share to existing shareholders and immediate dilution of $0.2978 per share in pro forma as adjusted net tangible book value to purchasers of pre-funded warrants in this offering. Dilution per share to new investors purchasing securities in this offering is the difference between the offering price per pre-funded warrant paid by such purchasers in this offering, plus the $0.0001 per share exercise price of each pre-funded warrant, and the pro forma as adjusted net tangible book value per share of common stock immediately after this offering. The following table illustrates this dilution on a per share basis:

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| | | |
|:---|:---|:---|
|  Offering price per pre-funded warrant |  | $0.5349 |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Historical net tangible book value per share as of September 30, 2025 | $(0.1562) |  |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Increase in net tangible book value per share attributable to the pro forma adjustments described above | $0.2924 |  |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Pro forma net tangible book value per share as of September 30, 2025 | 0.1362 |  |
| &nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp; Increase in pro forma as adjusted net tangible book value per share attributable to new investors purchasing securities in this offering | 0.1009 |  |
|  Pro forma as adjusted net tangible book value per share after giving effect to this offering |  | 0.2371 |
|  Dilution per share to new investors purchasing securities in this offering |  | $0.2978 |

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The above discussion and table are based on 192,315,535 shares of our common stock issued and outstanding on a pro forma basis, which represents 51,829,013 shares of our common stock outstanding as of September 30, 2025, plus (i) 92,278,707 pre-funded warrants in lieu of shares of common stock issued and

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outstanding as of September 30, 2025 (and assuming the full exercise of the pre-funded warrants) and (ii) 14,117,906 shares of common stock and 34,089,909 pre-funded warrants in lieu of shares of common stock issued upon the exercise of 48,207,815 Series B common stock warrants after September 30, 2025 and prior to the date of this prospectus supplement, and excludes:

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• 11,513,192 shares of our common stock issuable upon the exercise of stock options to purchase common stock that
were outstanding as of September 30, 2025, with a weighted-average exercise price of $3.09 per share (prior to giving effect to a stock option repricing approved by our stockholders in November 2025);

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• 334,125 shares of our common stock issuable upon the vesting of restricted stock units that were outstanding and
unvested as of September 30, 2025;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• 2,631 shares of our common stock issuable upon the exercise of a warrant to purchase common stock that was
outstanding as of September 30, 2025, with an exercise price of $9.50 per share;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• 48,207,815 shares of our common stock issuable upon the exercise of Series C common stock warrants to purchase
common stock, with a current exercise price of $0.75 per warrant;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• 27,470,862 shares of our common stock issuable upon the exercise of stock options to purchase common stock issued
subsequent to September 30, 2025, with an exercise price of $0.841 per share, pursuant to awards granted under our 2025 Stock Incentive Plan, which was approved by our stockholders in November 2025;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• 1,907,013 shares of our common stock reserved for issuance pursuant to future awards under the 2021 Plan as of
September 30, 2025, and an additional 3,177,046 shares of our common stock that became available for issuance under our 2021 Plan on January 1, 2026 in accordance with the terms of the plan;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• 238,300 shares of our common stock reserved for issuance pursuant to future awards under the 2022 Inducement Plan
as of September 30, 2025, and an additional 454,800 shares of our common stock approved for issuance under the 2022 Inducement Plan by our board on January 20, 2026; and

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• 1,314,384 shares of our common stock reserved for issuance pursuant to future awards under the ESPP as of
September 30, 2025, and an additional 584,062 shares of our common stock that became available for issuance under our ESPP on January 1, 2026 in accordance with the terms of the plan.

In addition, unless we specifically state otherwise, all information in this prospectus supplement reflects and assumes no vesting of outstanding restricted stock units, no exercise of outstanding stock options, pre-funded warrants or warrants described above, which would result in further dilution to new investors. In addition, we may 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 the extent that we raise additional capital through the sale of equity or convertible debt securities, the issuance of these securities could result in further dilution to our stockholders.

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**DESCRIPTION OF PRE-FUNDED WARRANTS** 

*The following is a brief summary of certain terms and conditions of the pre-funded warrants being offered in this offering. The following description is subject in all respects to the provisions contained in the pre-funded warrants.*

***Form***

The pre-funded warrants will be issued as individual warrant agreements to the holders. The form of pre-funded warrant will be filed as an exhibit to a Current Report on Form 8-K that we expect to file with the Securities and Exchange Commission ("SEC").

***Term***

The pre-funded warrants will expire on the date the pre-funded warrant is exercised in full.

***Exercisability***

The pre-funded warrants are exercisable at any time after their original issuance. The holder of the pre-funded warrant may exercise the pre-funded warrant by delivering an exercise notice, completed and duly signed, and payment in cash of the exercise price for the number of shares of our common stock for which the pre-funded warrant is being exercised. The holder of the pre-funded warrant may also satisfy its obligation to pay the exercise price through a "cashless exercise," in which the holder receives the net value of the pre-funded warrant in shares of common stock determined according to the formula set forth in the pre-funded warrant. No fractional shares of our common stock will be issued in connection with the exercise of a pre-funded warrant. In lieu of fractional shares that would otherwise be issuable, the number of shares of common stock to be issued shall be rounded down to the next whole number.

***Exercise Limitations***

A holder will be prohibited from exercising any portion of any pre-funded warrant if immediately prior to or following such exercise such holder (together with its affiliates) would beneficially own more than 4.99%, 9.99%, or 19.99%, as elected by the holder, of our issued and outstanding common stock immediately after giving effect to the exercise, as such percentage ownership is determined in accordance with the terms of the pre-funded warrant. However, any holder of any pre-funded warrant may increase or decrease such percentage to any other percentage not in excess of 19.99%, provided that any such increase will not be effective until the 61st day after notice from the holder is delivered to us.

***Exercise Price***

The exercise price of our common stock purchasable upon the exercise of the pre-funded warrants is $0.0001 per share. The exercise price of the pre-funded warrants and the number of shares of our common stock issuable upon exercise of the pre-funded warrants are subject to appropriate adjustment in the event of certain stock dividends and distributions, stock splits, stock combinations, reclassifications or similar events affecting our common stock, as well as upon certain pro rata distributions to our stockholders for no consideration. The exercise price of the pre-funded warrants will not be adjusted below the par value of our common stock.

***Transferability***

Subject to applicable laws, the pre-funded warrants may be transferred or assigned without our consent.

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***Exchange Listing***

There is no established public trading market for the pre-funded warrants, and we do not expect a market to develop. We do not intend to list the pre-funded warrants on the Nasdaq Capital Market, any other national securities exchange or any other nationally recognized trading system.

***Fundamental Transactions***

Upon the consummation of a fundamental transaction (as described in the pre-funded warrant, and generally including any merger or consolidation with or into another person in which we are not the surviving entity, the sale of all or substantially all of our assets, the acquisition of more than 50% of our outstanding common stock, or any person or group becoming the beneficial owner of more than 50% of the voting power of our outstanding common stock, or any reclassification or compulsory share exchange pursuant to which our common stock is effectively converted into or exchanged for other securities, cash or property), the holders of the pre-funded warrant will have the right to receive, upon exercise of the pre-funded warrant, the same amount and kind of securities, cash or property that such holders would have been entitled to receive had they exercised the pre-funded warrant immediately prior to such fundamental transaction, without regard to any limitations on exercise contained in the pre-funded warrant.

***No Rights as a Stockholder***

Except by virtue of such holder's ownership of shares of our common stock, and except for the right to participate in certain dividends and distributions, the holder of a pre-funded warrant does not have the rights or privileges of a holder of our common stock, including any voting rights, until such holder receives shares of our common stock upon the due exercise of a pre-funded warrant.

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**MATERIAL U.S. FEDERAL TAX CONSIDERATIONS FOR NON-U.S. HOLDERS** 

The following is a discussion of material U.S. federal income and estate tax considerations relating to ownership and disposition of our pre-funded warrants and shares of common stock acquired upon exercise of pre-funded warrants by a non-U.S. holder.

For purposes of this discussion, the term "non-U.S. holder" means a beneficial owner (other than a partnership or other pass-through entity) of pre-funded warrants or shares of common stock received upon exercise of pre-funded warrants that is not, for U.S. federal income tax purposes:

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• an individual who is a citizen or resident of the United States;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• a corporation, or other entity treated as a corporation for U.S. federal income tax purposes, created or
organized in or under the laws of the United States, any state thereof, or the District of Columbia;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• an estate the income of which is subject to U.S. federal income taxation regardless of its source; or

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• a trust if (1) a U.S. court is able to exercise primary supervision over the administration of the trust and
one or more U.S. persons has authority to control all substantial decisions of the trust or (2) the trust has a valid election in effect under applicable U.S. Treasury Regulations to be treated as a U.S. person.

This discussion does not address the tax treatment of partnerships or other entities or arrangements that are pass-through entities for U.S. federal income tax purposes or persons who hold their shares of our common stock or pre-funded warrants through partnerships or such other pass-through entities or arrangements. A partner in a partnership or other pass-through entity that will hold our common stock or pre-funded warrants should consult his, her or its own tax advisor regarding the tax consequences of the ownership and disposition of our common stock or pre-funded warrants through a partnership or other pass-through entity, as applicable.

This discussion is based on current provisions of the Internal Revenue Code of 1986, as amended (the "Code"), U.S. Treasury Regulations promulgated thereunder, current administrative rulings and judicial decisions, all as in effect as of the date of this prospectus supplement and all of which are subject to change or to differing interpretation, possibly with retroactive effect. Any change or differing interpretation could alter the tax consequences to holders described in this prospectus supplement. We have not requested a ruling from the Internal Revenue Service (the "IRS") with respect to the statements made and the conclusions reached in the following discussion and there can be no assurance that the IRS will not challenge one or more of the tax consequences described in this prospectus supplement.

We assume in this discussion that each holder holds shares of our common stock or pre-funded warrants as a "capital asset" within the meaning of Section 1221 of the Code (generally, property held for investment). This discussion does not address all aspects of U.S. federal income and estate taxation that may be relevant to a particular holder in light of that holder's individual circumstances nor does it address any aspects of U.S. state, local or non-U.S. taxes, the alternative minimum tax, the special tax accounting rules under Section 451(b) of the Code or the Medicare tax on net investment income. This discussion also does not consider any specific facts or circumstances that may apply to a holder and does not address the special tax rules applicable to particular holders, such as:

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• banks, financial institutions, and investment funds;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• brokers or dealers in securities;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• tax-exempt organizations and governmental organizations;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• pension plans, including "qualified foreign pension funds" as defined in Section 897(l)(2) of
the Code and entities all of the interests of which are held by qualified foreign pension funds;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• persons deemed to sell our common stock or pre-funded warrants under the
constructive sale provisions of the Code;

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&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• persons that hold our common stock or pre-funded warrants as part of a
straddle, hedge, conversion transaction, synthetic security or other integrated investment or who have elected to mark securities to market;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• insurance companies;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• controlled foreign corporations;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• passive foreign investment companies;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• non-U.S. governments; and

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• certain U.S. expatriates and former citizens or former long-term residents of the United States.

**THIS DISCUSSION IS FOR INFORMATIONAL PURPOSES ONLY AND IS NOT, AND IS NOT INTENDED TO BE, LEGAL OR TAX ADVICE. PROSPECTIVE INVESTORS SHOULD CONSULT THEIR OWN TAX ADVISORS REGARDING THE U.S. FEDERAL, STATE, LOCAL, AND NON-U.S. INCOME, ESTATE AND OTHER TAX CONSIDERATIONS OF ACQUIRING, HOLDING AND DISPOSING OF OUR COMMON STOCK OR PRE-FUNDED WARRANTS.** 

**Treatment of Pre-Funded Warrants** 

Although it is not entirely free from doubt, a pre-funded warrant should be treated as a share of our common stock for U.S. federal income tax purposes and a holder of pre-funded warrants should generally be taxed in the same manner as a holder of common stock as described below. Accordingly, upon exercise, no gain or loss should be recognized and the holding period of a pre-funded warrant should carry over to the share of common stock received. Similarly, the tax basis of the pre-funded warrant should carry over to the share of common stock received upon exercise increased by the exercise price per share. Our characterization is not binding on the IRS, and the IRS may treat our pre-funded warrants as warrants to acquire shares of our common stock. In that case, the amount and character of a holder's gain with respect to an investment in pre-funded warrants pursuant to this offering could be materially different than the discussion set forth below. Each holder should consult his, her or its own tax advisor regarding the risks associated with the acquisition of a pre-funded warrant pursuant to this offering (including potential alternative characterizations). The balance of this discussion generally assumes that the characterization described above is respected for U.S. federal income tax purposes.

**Distributions on our Common Stock or Pre-Funded Warrants** 

If we make distributions in respect of our common stock or pre-funded warrants, those distributions generally will constitute dividends for U.S. federal income tax purposes to the extent paid from our current or accumulated earnings and profits, as determined under U.S. federal income tax principles. If a distribution exceeds our current and accumulated earnings and profits, the excess will be treated as a tax-free return of the non-U.S. holder's investment, up to the holder's tax basis in the common stock or pre-funded warrants (and will reduce the non-U.S. holder's basis in the common stock or pre-funded warrants, but not below zero). Any remaining excess will be treated as capital gain, subject to the tax treatment described below under the heading "Gain on Sale, Exchange or Other Taxable Disposition of Our Common Stock or Pre-Funded Warrants." Any distributions will also be subject to the discussions below under the headings "Information Reporting and Backup Withholding" and "FATCA."

Except as described below, dividends paid to a non-U.S. holder generally will be subject to withholding of U.S. federal income tax at a 30% rate or such lower rate as may be specified by an applicable income tax treaty between the United States and such holder's country of residence. A non-U.S. holder of our common stock or pre-funded warrants who claims the benefit of an applicable income tax treaty between the United States and such holder's country of residence generally will be required to provide us or our paying agent with a properly executed IRS Form W-8BEN or W-8BEN-E (or successor form) and satisfy applicable certification and other requirements. A non-U.S. holder that is eligible for a reduced rate of U.S. withholding tax under an income tax treaty may obtain a refund or credit of any excess amounts withheld by timely filing an appropriate claim with

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the IRS. Non-U.S. holders are urged to consult their own tax advisors regarding their entitlement to benefits under a relevant income tax treaty and the specific methods available to them to satisfy these requirements.

Dividends that are treated as effectively connected with a trade or business conducted by a non-U.S. holder within the United States, and, if an applicable income tax treaty so provides, that are attributable to a permanent establishment or a fixed base maintained by the non-U.S. holder within the United States, are generally exempt from the 30% withholding tax if the non-U.S. holder satisfies applicable certification and disclosure requirements (generally including provision of a valid IRS Form W-8ECI (or applicable successor form) certifying that the dividends are effectively connected with the non-U.S. holder's conduct of a trade or business within the United States). However, such U.S. effectively connected income is taxed on a net income basis at the same U.S. federal income tax rates applicable to U.S. persons (as defined in the Code). Any U.S. effectively connected income received by a non-U.S. holder that is classified as a corporation for U.S. federal income tax purposes may also, under certain circumstances, be subject to an additional "branch profits tax" at a 30% rate or such lower rate as may be specified by an applicable income tax treaty between the United States and such holder's country of residence. Non-U.S. holders should consult their tax advisors with respect to other U.S. tax consequences of the ownership and disposition of our common stock and pre-funded warrants, including the possible imposition of the branch profits tax.

**Gain on Sale, Exchange or Other Taxable Disposition of Our Common Stock or Pre-Funded Warrants** 

Subject to the discussions below under "Information Reporting and Backup Withholding" and "FATCA," a non-U.S. holder generally will not be subject to U.S. federal income tax on any gain realized upon such non-U.S. holder's sale, exchange or other disposition of our common stock or pre-funded warrants unless:

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• the gain is effectively connected with the non-U.S. holder's
conduct of a trade or business in the United States, and, if an applicable income tax treaty so provides, the gain is attributable to a permanent establishment or fixed base maintained by the non-U.S. holder
in the United States; in these cases, the non-U.S. holder generally will be taxed on a net income basis at the same U.S. federal income tax rates applicable to U.S. persons (as defined in the Code), and, if
the non-U.S. holder is a foreign corporation, the branch profits tax described above under the heading "Distributions on our Common Stock or Pre-Funded Warrants" may also apply;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• the non-U.S. holder is a non-resident alien individual present in the United States for 183 days or more in the taxable year of the disposition and certain other requirements are met, in which case the non-U.S. holder will be subject to a 30% tax (or such lower rate as may be specified by an applicable income tax treaty between the United States and such holder's country of residence) on the net gain
derived from the disposition, which may be offset by certain U.S.-source capital losses of the non-U.S. holder, if any, provided that the non-U.S. holder has timely
filed U.S. federal income tax returns with respect to such losses; or

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• we are or have been, at any time during the five-year period preceding such disposition (or the non-U.S. holder's holding period, if shorter) a "U.S. real property holding corporation" unless our common stock is regularly traded on an established securities market and the non-U.S. holder held no more than 5% of our outstanding common stock, directly or indirectly, during the shorter of the five-year period ending on the date of the disposition or the period that the non-U.S. holder held our common stock. Special rules may apply to a holder of a pre-funded warrant. Non-U.S. holders are urged to
consult their own tax advisors regarding the application of these rules to pre-funded warrants. If we are determined to be a U.S. real property holding corporation and the foregoing exception does not apply,
then the non-U.S. holder generally will be taxed on its net gain derived from the disposition at the U.S. federal income tax rates applicable to U.S. persons (as defined in the Code). Generally, a corporation
is a "U.S. real property holding corporation" if the fair market value of its "U.S. real property interests" equals or exceeds 50% of the sum of the fair market value of its worldwide real property interests plus its other
assets used or held for use in a trade or business. Although there can be no assurance, we believe that we are not currently, and we do not anticipate becoming, a "U.S. real

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property holding corporation" for U.S. federal income tax purposes. No assurance can be provided that our common stock will be regularly traded on an established securities market for purposes of the rule described above.

**U.S. Federal Estate Tax** 

Shares of our common stock or pre-funded warrants that are owned or treated as owned by an individual who is a non-U.S. holder (as specially defined for U.S. federal estate tax purposes) at the time of death are considered U.S.-situs assets and will be included in the individual's gross estate for U.S. federal estate tax purposes. Such shares, therefore, may be subject to U.S. federal estate tax, unless an applicable estate tax or other treaty provides otherwise.

**Information Reporting and Backup Withholding** 

We must report annually to the IRS and to each non-U.S. holder the gross amount of the distributions on our common stock or pre-funded warrants paid to such holder and the tax withheld, if any, with respect to such distributions. Non-U.S. holders may have to comply with specific certification procedures to establish that the holder is not a U.S. person (as defined in the Code) in order to avoid backup withholding at the applicable rate with respect to distributions on our common stock or pre-funded warrants. Generally, a non-U.S. holder will comply with such procedures if it provides a properly executed IRS Form W-8BEN or W-8BEN-E (or other applicable Form W-8), or otherwise meets documentary evidence requirements for establishing that it is a non-U.S. holder, or otherwise establishes an exemption. Dividends paid to non-U.S. holders subject to withholding of U.S. federal income tax, as described above under the heading "Distributions on our Common Stock or Pre-Funded Warrants," will generally be exempt from U.S. backup withholding.

Information reporting and backup withholding generally will apply to the proceeds of a disposition of our common stock or pre-funded warrants by a non-U.S. holder effected by or through the U.S. office of any broker, U.S. or non-U.S., unless the holder certifies its status as a non-U.S. holder and satisfies certain other requirements, or otherwise establishes an exemption. Generally, information reporting and backup withholding will not apply to a payment of disposition proceeds to a non-U.S. holder where the transaction is effected outside the United States through a non-U.S. office of a non-U.S. broker. Non-U.S. holders should consult their own tax advisors regarding the application of the information reporting and backup withholding rules to them.

Copies of information returns may be made available to the tax authorities of the country in which the non-U.S. holder resides or is incorporated under the provisions of a specific treaty or agreement.

Backup withholding is not an additional tax. Rather, any amounts withheld under the backup withholding rules from a payment to a non-U.S. holder can be refunded or credited against the non-U.S. holder's U.S. federal income tax liability, if any, provided that an appropriate claim is timely filed with the IRS.

**FATCA** 

Provisions of the Code commonly referred to as the Foreign Account Tax Compliance Act ("FATCA"), generally impose a 30% withholding tax on dividends on, and gross proceeds from the sale or other disposition of, our common stock or pre-funded warrants if paid to a foreign entity unless (1) if the foreign entity is a "foreign financial institution" (which is broadly defined for this purpose and in general includes investment vehicles), the foreign entity undertakes certain due diligence, reporting, withholding, and certification obligations, (2) if the foreign entity is not a "foreign financial institution," the foreign entity identifies certain of its U.S. investors, or (3) the foreign entity is otherwise excepted under FATCA.

Withholding under FATCA generally applies to payments of dividends on our common stock or pre-funded warrants. While withholding under FATCA may apply to payments of gross proceeds from a sale or other

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disposition of our common stock or pre-funded warrants, withholding on payments of gross proceeds is not required under proposed U.S. Treasury Regulations. Although such regulations are not final, applicable withholding agents may rely on the proposed regulations until final regulations are issued.

If withholding under FATCA is required on any payment related to our common stock or pre-funded warrants, investors not otherwise subject to withholding (or that otherwise would be entitled to a reduced rate of withholding) on such payment may be required to seek a refund or credit from the IRS. An intergovernmental agreement between the United States and an applicable foreign country may modify the requirements described in this section. Non-U.S. holders should consult their own tax advisors regarding the possible implications of FATCA on their investment in, or ownership of, our common stock or pre-funded warrants and the entities through which they hold our common stock or pre-funded warrants.

**The preceding discussion of material U.S. federal tax considerations is for informational purposes only. It is not legal or tax advice. Prospective investors should consult their own tax advisors regarding the particular U.S. federal, state, local, and non-U.S. tax consequences of purchasing, holding and disposing of our common stock or pre-funded warrants, including the consequences of any proposed changes in applicable laws.** 

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**UNDERWRITING** 

Leerink Partners LLC is acting as sole bookrunner and sole underwriter for this offering. Subject to the terms and conditions set forth in the underwriting agreement between us and the underwriter, we have agreed to sell to the underwriter, and the underwriter has agreed to purchase from us, 74,780,300 pre-funded warrants.

Subject to the terms and conditions set forth in the underwriting agreement, the underwriter has agreed to purchase all of the pre-funded warrants sold under the underwriting agreement if any of the pre-funded warrants are purchased. If an underwriter defaults, the underwriting agreement provides that the purchase commitments of the non-defaulting underwriters may be increased or the underwriting agreement may be terminated.

We have agreed to indemnify the underwriter against certain liabilities, including liabilities under the Securities Act, or to contribute to payments the underwriter may be required to make in respect of those liabilities.

The underwriter is offering the pre-funded warrants, subject to prior sale, when, as and if issued to and accepted by it, subject to approval of legal matters by its counsel, including the validity of the pre-funded warrants, and subject to other conditions contained in the underwriting agreement, such as the receipt by the underwriter of officers' certificates and legal opinions. The underwriter reserves the right to withdraw, cancel or modify offers and to reject orders in whole or in part.

**Discounts and Commissions** 

The underwriter has advised us that it proposes initially to offer the pre-funded warrants at the offering price set forth on the cover page of this prospectus supplement and to dealers at that price less a concession not in excess of $0.01926 per pre-funded warrant. After the offering, the offering price, concession or any other term of this offering may be changed by the underwriter.

The following table shows the offering price, underwriting discounts and commissions that we are to pay the underwriter and the proceeds, before expenses, to us in connection with this offering.

---

| | | |
|:---|:---|:---|
|  | **Per Pre-Funded<br>Warrant** | **Total** |
|  Offering price | $0.5349 | $39999982.47 |
|  Underwriting discounts and commissions | $0.0321 | $2400447.63 |
|  Proceeds, before expenses, to us | $0.5028 | $37599534.84 |

---

We estimate expenses payable by us in connection with this offering, other than the underwriting discounts and commissions referred to above, will be approximately $450,000. We have agreed to reimburse the underwriter for up to (i) $3,500 relating to the registration or qualification of securities under the "blue sky" securities laws and (ii) $20,000 for its FINRA counsel fee. In accordance with FINRA Rule 5110, this FINRA reimbursed fee is deemed underwriting compensation for this offering.

Certain expenses payable by us in connection with this offering will be reimbursed by the underwriter.

**No Sales of Similar Securities** 

We and our executive officers and directors have agreed not to sell or transfer any common stock or securities convertible into or exchangeable or exercisable for common stock, (a) by us for 90 days; and (b) by our executive officers and directors for 60 days, in each case after the date of this prospectus supplement without first obtaining the written consent of Leerink Partners LLC as sole underwriter. Specifically, we and these other persons have agreed, with certain limited exceptions, not to directly or indirectly:

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• offer, pledge, sell, contract to sell, sell any option or contract to purchase, purchase any option or contract
to sell, grant any option, right or warrant to purchase, lend, or otherwise transfer or dispose of, directly or indirectly, any shares of common stock beneficially owned by the lock-up party or any other
securities so owned convertible into or exercisable or exchangeable for common stock; or

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&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• enter into any swap or other agreement or any transaction that transfers, in whole or in part, the economic
consequence of ownership of any common stock, whether any such swap, agreement or transaction is to be settled by delivery of shares or other securities, in cash or otherwise.

The lock-up provisions apply to common stock and to securities convertible into or exchangeable or exercisable for common stock. They also apply to common stock owned now or acquired later by the person executing the lock-up agreement or for which the person executing the lock-up agreement later acquires the power of disposition. The exceptions permit us, among other things and subject to restrictions, to: (i) issue the shares of common stock and pre-funded warrants, (ii) issue shares of common stock upon the exercise of an option or warrant or the conversion of a security, (iii) facilitate the establishment of a trading plan on behalf of a stockholder, officer or director of us pursuant to Rule 10b5-1 under the Exchange Act for the transfer of shares of common stock, provided that such plan does not provide for the transfer of common stock during the lock-up period and to the extent a public announcement or filing under the Exchange Act, if any, is required of or voluntarily made by us regarding the establishment of such plan, such announcement or filing shall include a statement to the effect that no transfer of common stock may be made under such plan during the lock-up period, (iv) grant options to purchase shares of common stock or other awards granted under a stock incentive plan or stock purchase plan and the issuance by us of shares of common stock upon the exercise thereof, provided that each newly appointed director of officer (including a newly appointed director or officer that is appointed during the lock-up period) that is a recipient of such securities shall execute and deliver to the underwriter a lock-up agreement covering the remainder of the lock-up period, (v) the filing by us of any registration statement on Form S-8 or a successor form thereto relating to the shares of common stock granted pursuant to or reserved for issuance under a stock incentive plan or stock purchase plan, or (vi) shares of common stock or other securities issued in connection with a transaction with an unaffiliated third party that includes a debt financing or a bona fide commercial relationship (including joint ventures, marketing or distribution arrangements, collaboration agreements, or intellectual property license agreements) or any acquisition of assets or acquisition of not less than a majority or controlling portion of the equity of another entity, provided that the aggregate number of shares issued pursuant to this clause (vi) shall not exceed 5% of the total number of outstanding shares of common stock immediately following the issuance and sale of the securities to be sold in connection with this offering and (y) the recipient of any such shares of common stock and securities issued pursuant to this clause (vi) during the lock-up period shall enter into a lock-up agreement on or prior to such issuance.

The exceptions permit parties to the "lock-up" agreements, among other things and subject to restrictions, to: (i) participate in transactions relating to shares of common stock or other securities acquired in the offering or in open market transactions after the completion of the offering, provided that no filing under Section 16(a) of the Exchange Act shall be required or shall be voluntarily made during the lock-up period in connection with subsequent sales of common stock or other securities acquired in the offering or such open market transactions, (ii) transfer shares of common stock or any security convertible into or exercisable or exchangeable for common stock as a bona fide gift or gifts, or for bona fide estate planning purposes, (iii) transfer or dispose of shares of common stock or any security convertible into or exercisable or exchangeable for common stock to any member of the immediate family of the lock-up party or any trust for the direct or indirect benefit of the lock-up party or the immediate family of the lock-up party, or if the lock-up party is a trust, to any beneficiary (including such beneficiary's estate) of the lock-up party, in a transaction not involving a disposition for value, (iv) transfer or dispose of shares of common stock or any security convertible into or exercisable or exchangeable for common stock to any corporation, partnership, limited liability company or other entity all of the beneficial ownership interests of which are held by the lock-up party or a member of the immediate family of the lock-up party, (v) transfer or dispose of shares of common stock or any security convertible into or exercisable or exchangeable for common stock by will, other testamentary document or intestate succession to the legal representative, heir, beneficiary or a member of the immediate family of the lock-up party upon the death of the lock-up party or in connection with a divorce settlement or solely by operation of law, such as pursuant to a qualified domestic order or court order, (vi) if the lock-up party is an entity, transfer or dispose of shares of common stock or any security convertible into common stock to general or limited partners, members or stockholders of the lock-up party, its direct or indirect affiliates (as defined in Rule 405 promulgated under the Securities Act of 1933, as amended) or to

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an investment fund or other entity that controls or manages, or is under common control with, the lock-up party, provided that in the case of any transfer, disposition or distribution pursuant to clause (ii), (iii), (iv), (v) or (vi), (A) each transferee, donee or distributee shall sign and deliver a lock-up agreement, and (B) no public announcement shall be made and no filing under Section 16(a) of the Exchange Act, reporting a reduction in beneficial ownership of shares of common stock, shall be required or shall be voluntarily made during the lock-up period (other than, in the case of a transfer or other disposition pursuant to clause (ii), (ii) or (v) above, any Form 4 or Form 5 required to be filed under the Exchange Act if the lock-up party is subject to Section 16 reporting with respect to us under the Exchange Act and indicating by footnote disclosure or otherwise the nature of the transfer or disposition), (vii) transfer or dispose of shares of common stock or any security convertible into or exercisable or exchangeable for common stock to us pursuant to any contractual arrangement in effect on the date of the underwriting agreement and disclosed to the underwriter that provides for the repurchase of the lock-up party's common stock or other securities by us or in connection with the termination of the lock-up party's employment with or service to us, provided that no filing under Section 16(a) of the Exchange Act reporting a reduction in beneficial ownership of shares of common stock shall be required or shall be voluntarily made during the lock-up period in connection with any such transfers or dispositions (other than any Form 4 or Form 5 required to be filed under the Exchange Act if the lock-up party is subject to Section 16 reporting with respect to us under the Exchange Act and indicating by footnote disclosure or otherwise the nature of the transfer or disposition), (viii) exercise stock options to purchase shares of common stock, granted under any equity incentive plan described in our Exchange Act filings and any related transfer to us of shares of common stock (including by way of "net" or "cashless" exercise solely to cover withholding tax obligations in connection with such exercise and any transfer to us for the payment of taxes as a result of such exercise), provided that any shares of common stock received upon exercise shall be subject to the restrictions on transfer set forth in the underwriting agreement, provided, further, that no filing under Section 16(a) of the Exchange Act reporting a reduction in beneficial ownership of shares of common stock shall be required or shall be voluntarily made during the lock-up period (other than a filing on a Form 4 that reports such disposition under the transaction code "F"), (ix) transfer or dispose of shares of common stock in connection with the vesting or settlement of restricted stock units, so long as such sale is effected pursuant to our sell to cover policy solely in an amount sufficient to cover withholding taxes due in connection with such restricted stock units, provided that any filing under Section 16(a) of the Exchange Act shall indicate in the footnotes thereto that the filing relates to the applicable circumstances described in this clause and no other public announcement shall be required or shall be made voluntarily in connection with such transfer, (x) establish a trading plan pursuant to Rule 10b5-1 under the Exchange Act for the transfer of shares of common stock, provided that such plan does not provide for the transfer of common stock during the lock-up period and to the extent a public announcement or filing under the Exchange Act, if any, is required of or voluntarily made by or on behalf of the lock-up party or us regarding the establishment of such plan, such announcement or filing shall include a statement to the effect that no transfer of common stock may be made under such plan during the lock-up period, or (xi) (A) transfer shares of common stock (or any securities convertible into or exercisable or exchangeable for common stock) pursuant to a bona fide third-party tender offer for shares of our capital stock made to all holders of our securities, merger, consolidation or other similar transaction approved by our board of directors the result of which is that any person (as defined in Section 13(d)(3) of the Exchange Act), or group of persons, other than us, becomes the beneficial owner (as defined in Rules 13d-3 and 13d-5 of the Exchange Act) of more than 50% of the total voting power of the voting stock of us and (B) entry into any lock-up, voting or similar agreement pursuant to which the lock-up party may agree to transfer, sell, tender or otherwise dispose of shares of common stock or such other securities in connection with a transaction described in (A) above, provided that in the event that such change of control transaction is not completed, the common stock (or any security convertible into or exercisable or exchangeable for common stock) owned by the lock-up party shall remain subject to the restrictions contained in the lock-up agreement.

**Nasdaq Global Select Market Listing** 

Our common stock is listed on the Nasdaq Capital Market under the symbol "XLO." We do not intend to list the pre-funded warrants on the Nasdaq Capital Market, any other national securities exchange or any other nationally recognized trading system.

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**Price Stabilization, Short Positions and Penalty Bids** 

Until the distribution of the securities is completed, SEC rules may limit underwriters and selling group members from bidding for and purchasing our common stock. However, the underwriter may engage in transactions that stabilize the price of the common stock, such as bids or purchases to peg, fix or maintain that price.

Similar to other purchase transactions, the underwriter's purchases to cover the syndicate short sales may have the effect of raising or maintaining the market price of our common stock or preventing or retarding a decline in the market price of our common stock. As a result, the price of our common stock may be higher than the price that might otherwise exist in the open market. The underwriter may conduct these transactions on the Nasdaq Capital Market, in the over-the-counter market or otherwise.

Neither we nor the underwriter make any representation or prediction as to the direction or magnitude of any effect that the transactions described above may have on the price of our common stock. In addition, neither we nor the underwriter make any representation that the underwriter will engage in these transactions or that these transactions, once commenced, will not be discontinued without notice.

The underwriter may also engage in passive market making transactions in our common stock on the Nasdaq Capital Market in accordance with Rule 103 of Regulation M during a period before the commencement of offers or sales of shares of our common stock in this offering and extending through the completion of distribution. A passive market maker must display its bid at a price not in excess of the highest independent bid of that security. However, if all independent bids are lowered below the passive market maker's bid, that bid must then be lowered when specified purchase limits are exceeded.

**Electronic Distribution** 

In connection with this offering, the underwriter or securities dealers may distribute prospectuses by electronic means, such as e-mail.

**Other Relationships** 

The underwriter is a full service financial institution engaged in various activities, which may include securities trading, commercial and investment banking, financial advisory, investment management, investment research, principal investment, hedging, financing and brokerage activities. The underwriter has in the past and may in the future engage in investment banking and other commercial dealings in the ordinary course of business with us and our affiliates, for which it may in the future receive customary fees, commissions and expenses. For example, Leerink Partners LLC also serves as sales agent in our at-the-market offering of our common stock and is the sales agent under our "at-the-market" program. In June 2025, Leerink Partners LLC served as sole bookrunner and sole underwriter for our underwritten public offering of securities comprising pre-funded warrants and common stock warrants.

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In addition, in the ordinary course of its business activities, the underwriter may make or hold a broad array of investments and actively trade debt and equity securities (or related derivative securities) and financial instruments (including bank loans) for its own account and for the accounts of its customers. Such investments and securities activities may involve securities and/or instruments of ours or our affiliates. The underwriter may also make investment recommendations and/or publish or express independent research views in respect of such securities or financial instruments and may hold, or recommend to clients that they acquire, long and/or short positions in such securities and instruments.

**Selling Restrictions** 

***Notice to Prospective Investors in the European Economic Area***

In relation to each Member State of the European Economic Area (each a "Relevant State"), no securities have been offered or will be offered pursuant to this offering to the public in that Relevant State prior to the publication of a prospectus in relation to the securities which has been approved by the competent authority in that Relevant State or, where appropriate, approved in another Relevant State and notified to the competent authority in that Relevant State, all in accordance with the Prospectus Regulation, except that the securities may be offered to the public in that Relevant State at any time:

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• to any qualified investor as defined under Article 2 of the Prospectus Regulation;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• to fewer than 150 natural or legal persons (other than qualified investors as defined under Article 2 of the
Prospectus Regulation), subject to obtaining the prior consent of the representative for any such offer; or

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• in any other circumstances falling within Article 1(4) of the Prospectus Regulation,

provided that no such offer of the securities shall require us or any underwriter to publish a prospectus pursuant to Article 3 of the Prospectus Regulation, supplement a prospectus pursuant to Article 23 of the Prospectus Regulation or publish an Annex IX document pursuant to Article 1(4) of the Prospectus Regulation.

For the purposes of this provision, the expression an "offer to the public" in relation to the securities in any Relevant State means the communication in any form and by any means of sufficient information on the terms of the offer and any securities to be offered so as to enable an investor to decide to purchase or subscribe for any securities, and the expression "Prospectus Regulation" means Regulation (EU) 2017/1129.

***Notice to Prospective Investors in the United Kingdom***

No securities have been offered or will be offered pursuant to the offering to the public in the United Kingdom except that the securities may be offered to the public in the United Kingdom at any time:

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;a) where (i) the offer is conditional on the admission of the securities to trading on the London Stock
Exchange plc's main market (in reliance on the exception in paragraph 6(a) of Schedule 1 of the POATR) or (ii) the securities being offered are at the time of the offer already admitted to trading on London Stock Exchange plc's main
market (in reliance on the exception in paragraph 6(b) of Schedule 1 of the POATR);

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;b) to any qualified investor as defined in paragraph 15 of Schedule 1 of the POATR;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;c) to fewer than 150 persons (other than qualified investors as defined in paragraph 15 of Schedule 1 of the
POATR), subject to obtaining the prior consent of the representative for any such offer; or

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;d) in any other circumstances falling within Part 1 of Schedule 1 of the POATR;

For the purposes of this provision, the expression an "offer to the public" in relation to the securities in the United Kingdom means the communication to any person which presents sufficient information on: (a) the securities to be offered; and (b) the terms on which they are to be offered, to enable an investor to decide to buy

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or subscribe for the securities and the expression "POATR" means the Public Offers and Admissions to Trading Regulations 2024.

***Notice to Prospective Investors in Canada***

The securities may be sold only to purchasers purchasing, or deemed to be purchasing, as principal that are accredited investors, as defined in National Instrument 45-106 Prospectus Exemptions or subsection 73.3(1) of the Securities Act (Ontario), and are permitted clients, as defined in National Instrument 31-103 Registration Requirements, Exemptions and Ongoing Registrant Obligations. Any resale of the securities must be made in accordance with an exemption from, or in a transaction not subject to, the prospectus requirements of applicable securities laws.

Securities legislation in certain provinces or territories of Canada may provide a purchaser with remedies for rescission or damages if this prospectus supplement (including any amendment thereto) contains a misrepresentation, provided that the remedies for rescission or damages are exercised by the purchaser within the time limit prescribed by the securities legislation of the purchaser's province or territory. The purchaser should refer to any applicable provisions of the securities legislation of the purchaser's province or territory for particulars of these rights or consult with a legal advisor.

Pursuant to section 3A.3 of National Instrument 33-105 Underwriting Conflicts (NI 33-105), the underwriter is not required to comply with the disclosure requirements of NI 33-105 regarding underwriter conflicts of interest in connection with this offering.

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**LEGAL MATTERS** 

The validity of the securities offered hereby will be passed upon for us by Wilmer Cutler Pickering Hale and Dorr LLP, Boston, Massachusetts. Leerink Partners LLC is being represented in connection with this offering by Cooley LLP, New York, New York.

**EXPERTS** 

The consolidated financial statements of Xilio Therapeutics, Inc. appearing in Xilio Therapeutics, Inc.'s Annual Report (Form 10-K) for the year ended December 31, 2024 have been audited by Ernst & Young LLP, independent registered public accounting firm, as set forth in their report thereon (which contains an explanatory paragraph describing conditions that raise substantial doubt about the Company's ability to continue as a going concern as described in Note 1 to the consolidated financial statements) included therein, and incorporated herein by reference. Such financial statements are, and audited financial statements to be included in subsequently filed documents will be, incorporated herein in reliance upon the report of Ernst & Young LLP pertaining to such financial statements (to the extent covered by consents filed with the Securities and Exchange Commission) 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 forms a part. The rules and regulations of the SEC allow us to omit from this prospectus certain information included in the registration statement. For further information about us and the securities we are offering under this prospectus, you should refer to the registration statement and the exhibits and schedules filed with the registration statement. With respect to the statements contained in this prospectus regarding the contents of any agreement or any other document, in each instance, the statement is qualified in all respects by the complete text of the agreement or document, a copy of which has been filed as an exhibit to the registration statement.

We file reports, proxy statements and other information with the SEC under the Exchange Act. The SEC maintains an Internet website that contains reports, proxy statements and other information about issuers, like us, that file electronically with the SEC. The address of that website is *www.sec.gov*.

**INCORPORATION BY REFERENCE** 

The SEC allows us to "incorporate by reference" the information we file with them which means that we can disclose important information to you by referring you to those documents instead of having to repeat the information in this prospectus. The information incorporated by reference is considered to be part of this prospectus, and later information that we file with the SEC will automatically update and supersede this information. We incorporate by reference the documents listed below and any future information filed (rather than furnished) with the SEC under Sections 13(a), 13(c), 14, or 15(d) of the Exchange Act between the date of this prospectus and the termination of this offering, provided, however, that we are not incorporating any information furnished under Item 2.02 or Item 7.01 of any current report on Form 8-K:

This prospectus incorporates by reference the documents set forth below that have previously been filed with the SEC:

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• Our Annual Report on [Form 10-K](http://www.sec.gov/Archives/edgar/data/../../../ix?doc=/Archives/edgar/data/1840233/000155837025002640/xlo-20241231x10k.htm) for the fiscal year ended December 31, 2024
filed with the SEC on March 11, 2025, including the information specifically incorporated by reference therein from our Definitive Proxy Statement on Schedule 14A filed with the SEC on April 28, 2025;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• Our Quarterly Reports on Form 10-Q for the quarterly periods ended [March 31, 2025](http://www.sec.gov/Archives/edgar/data/../../../ix?doc=/Archives/edgar/data/0001840233/000155837025006996/xlo-20250331x10q.htm) , filed with the SEC on May 8, 2025, [June 30, 2025](http://www.sec.gov/Archives/edgar/data/../../../ix?doc=/Archives/edgar/data/0001840233/000155837025011477/xlo-20250630x10q.htm) , filed with the SEC on
August 14, 2025, and [September 30, 2025](http://www.sec.gov/Archives/edgar/data/../../../ix?doc=/Archives/edgar/data/0001840233/000119312525278837/xlo-20250930.htm) , filed with the SEC on November 13, 2025;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• Our Current Reports on Form 8-K filed with the SEC
on [January 21, 2025](http://www.sec.gov/Archives/edgar/data/../../../ix?doc=/Archives/edgar/data/0001840233/000155837025000291/xlo-20250121x8k.htm) (with respect to Item 
8.01), [February 12, 2025](http://www.sec.gov/Archives/edgar/data/../../../ix?doc=/Archives/edgar/data/0001840233/000155837025000823/xlo-20250210x8k.htm) (with respect to Items 1.01, 3.02 and 8.01), [March 11, 2025](http://www.sec.gov/Archives/edgar/data/../../../ix?doc=/Archives/edgar/data/1840233/000119312525051532/d897420d8k.htm) , [April 8, 2025](http://www.sec.gov/Archives/edgar/data/../../../ix?doc=/Archives/edgar/data/1840233/000155837025004599/xlo-20250404x8k.htm) , [June 2, 2025](http://www.sec.gov/Archives/edgar/data/../../../ix?doc=/Archives/edgar/data/1840233/000119312525132710/d91295d8k.htm) (with respect to Item 8.01), [June 3, 2025](http://www.sec.gov/Archives/edgar/data/../../../ix?doc=/Archives/edgar/data/1840233/000119312525133773/d88500d8k.htm) (with respect to Items 1.01, 8.01 and 9.01, other than
Exhibit 99.1), [June 10, 2025](http://www.sec.gov/Archives/edgar/data/../../../ix?doc=/Archives/edgar/data/0001840233/000155837025008512/xlo-20250610x8k.htm) , [June 12, 2025](http://www.sec.gov/Archives/edgar/data/../../../ix?doc=/Archives/edgar/data/0001840233/000155837025008571/xlo-20250610x8k.htm) , [August 28, 2025](http://www.sec.gov/Archives/edgar/data/../../../ix?doc=/Archives/edgar/data/0001840233/000155837025011802/xlo-20250822x8k.htm) , [September 9, 2025](http://www.sec.gov/Archives/edgar/data/../../../ix?doc=/Archives/edgar/data/0001840233/000155837025011949/xlo-20250909x8k.htm) (with respect to Item 8.01), [October 3, 2025](http://www.sec.gov/Archives/edgar/data/../../../ix?doc=/Archives/edgar/data/0001840233/000119312525229231/d74952d8k.htm) , [November 25, 2025](http://www.sec.gov/Archives/edgar/data/../../../ix?doc=/Archives/edgar/data/0001840233/000119312525297165/xlo-20251121.htm) (with respect to Items 5.02 and 5.07), and [January 8, 2026](http://www.sec.gov/Archives/edgar/data/../../../ix?doc=/Archives/edgar/data/0001840233/000119312526007063/xlo-20260108.htm) (with respect to Item 5.02); and

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• The description of our common stock contained in our Registration Statement on [Form 8-A](http://www.sec.gov/Archives/edgar/data/1840233/000110465921127173/tm2115750d15_8a12b.htm) , as filed with the SEC on October 18, 2021, as the description therein has been updated
and superseded by the description of our capital stock contained in [Exhibit 4.3](http://www.sec.gov/Archives/edgar/data/1840233/000155837022002552/xlo-20211231xex4d3.htm) to our Annual Report on [Form 10-K](http://www.sec.gov/Archives/edgar/data/../../../ix?doc=/Archives/edgar/data/1840233/000155837022002552/xlo-20211231x10k.htm) for the fiscal year ended December 31, 2021, as
filed with the SEC on March 1, 2022, and including any amendments or reports filed for the purpose of updating such description.

All reports and other documents we subsequently file pursuant to Section 13(a), 13(c), 14 or 15(d) of the Exchange Act, prior to the termination of this offering, including all such documents we may file with the SEC after the date of the initial registration statement and prior to the effectiveness of the registration statement, but

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excluding any information furnished to, rather than filed with, the SEC, will also be incorporated by reference into this prospectus and deemed to be part of this prospectus from the date of the filing of such reports and documents.

You may request a free copy of any of the documents incorporated by reference in this prospectus by writing or telephoning us at the following address:

Xilio Therapeutics, Inc.

828 Winter Street, Suite 300

Waltham, Massachusetts 02451

Attn: Investor Relations

Phone: (857) 524-2466

E-mail: investors@xiliotx.com

Exhibits to the filings will not be sent, however, unless those exhibits have specifically been incorporated by reference in this prospectus or any accompanying prospectus supplement.

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##### [**Table of Contents**](#toc)
**PROSPECTUS** 

**$250,000,000**![LOGO](g74783g00a03.jpg)

## Xilio Therapeutics, Inc.
**Common Stock** 

**Preferred Stock** 

**Debt Securities** 

**Units** 

**Warrants**

We may offer and sell securities from time to time in one or more offerings of up to $250,000,000 in aggregate offering price. This prospectus describes the general terms of these securities and the general manner in which these securities will be offered. We will provide the specific terms of these securities in supplements to this prospectus. The prospectus supplements will also describe the specific manner in which these securities will be offered and may also supplement, update or amend information contained in this document. You should read this prospectus and any applicable prospectus supplement before you invest.

We may offer these securities in amounts, at prices and on terms determined at the time of offering. The securities may be sold directly to you, through agents, or through underwriters and dealers. If agents, underwriters or dealers are used to sell the securities, we will name them and describe their compensation in a prospectus supplement.

Our common stock is listed on The Nasdaq Global Select Market under the symbol "XLO." On May 5, 2025, the last reported sale price of our common stock was $0.7398 per share.

**Investing in these securities involves risks. See the information included under "[Risk Factors](#tx74783_6)" on page 7 of this prospectus and in any accompanying prospectus supplement, and under similar headings in the documents incorporated by reference in this prospectus or any prospectus supplement, for a discussion of the factors you should carefully consider before deciding to purchase these securities.**

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

**The date of this prospectus is May 8, 2025.** 

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**TABLE OF CONTENTS** 

---

| | |
|:---|:---|
|  [ABOUT THIS PROSPECTUS](#tx74783_1) | 1 |
|  [WHERE YOU CAN FIND MORE INFORMATION](#tx74783_2) | 2 |
|  [INCORPORATION BY REFERENCE](#tx74783_3) | 3 |
|  [CAUTIONARY NOTE REGARDING FORWARD-LOOKING STATEMENTS](#tx74783_4) | 4 |
|  [ABOUT XILIO THERAPEUTICS, INC.](#tx74783_5) | 6 |
|  [RISK FACTORS](#tx74783_6) | 7 |
|  [USE OF PROCEEDS](#tx74783_7) | 8 |
|  [DESCRIPTION OF CAPITAL STOCK](#tx74783_8) | 9 |
|  [DESCRIPTION OF DEBT SECURITIES](#tx74783_9) | 16 |
|  [DESCRIPTION OF WARRANTS](#tx74783_10) | 26 |
|  [DESCRIPTION OF UNITS](#tx74783_11) | 28 |
|  [FORMS OF SECURITIES](#tx74783_12) | 29 |
|  [PLAN OF DISTRIBUTION](#tx74783_13) | 31 |
|  [LEGAL MATTERS](#tx74783_14) | 34 |
|  [EXPERTS](#tx74783_15) | 34 |

---

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##### [**Table of Contents**](#toc)
**ABOUT THIS PROSPECTUS** 

This prospectus is part of a registration statement that we filed with the Securities and Exchange Commission (the "SEC") utilizing a "shelf" registration process. Under this shelf registration process, we may from time to time sell any combination of the securities described in this prospectus in one or more offerings for an aggregate initial offering price of up to $250,000,000.

This prospectus provides you with a general description of the securities we may offer. Each time we sell securities, we will provide one or more prospectus supplements that will contain specific information about the terms of the offering. The prospectus supplement may also add, update or change information contained in this prospectus. You should read both this prospectus and the accompanying prospectus supplement together with the additional information described under the heading "Where You Can Find More Information."

You should rely only on the information contained in or incorporated by reference in this prospectus, in any accompanying prospectus supplement or in any related free writing prospectus filed by us with the SEC. We have not authorized anyone to provide you with different information. This prospectus and any accompanying prospectus supplement do not constitute an offer to sell or the solicitation of an offer to buy any securities other than the securities described in this prospectus or such accompanying prospectus supplement or an offer to sell or the solicitation of an offer to buy such securities in any circumstances in which such offer or solicitation is unlawful. You should assume that the information appearing in this prospectus, any prospectus supplement, the documents incorporated by reference and any related free writing prospectus is accurate only as of their respective dates. Our business, financial condition, results of operations and prospects may have changed materially since those dates.

Unless the context otherwise indicates, references in this prospectus to the "Company," "we," "our" and "us" refer collectively to Xilio Therapeutics, Inc., a Delaware corporation, and its consolidated subsidiaries.

We own various U.S. federal trademark applications and unregistered trademarks, including our company name. All other trademarks or trade names referred to in this prospectus are the property of their respective owners. Solely for convenience, the trademarks and trade names in this prospectus are referred to without the symbols <sup>®</sup> and <sup>™</sup>, but such references should not be construed as any indicator that their respective owners will not assert, to the fullest extent under applicable law, their rights thereto.

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##### [**Table of Contents**](#toc)
**WHERE YOU CAN FIND MORE INFORMATION**

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. Copies of certain information filed by us with the SEC are also available on our website at www.xiliotx.com. Our website is not a part of this prospectus and is not incorporated by reference in this prospectus.

This prospectus is part of a registration statement we filed with the SEC. This prospectus omits some information contained in the registration statement in accordance with SEC rules and regulations. You should review the information and exhibits in the registration statement for further information about us and our consolidated subsidiaries and the securities we are offering. Statements in this prospectus concerning any document we filed as an exhibit to the registration statement or that we otherwise filed with the SEC are not intended to be comprehensive and are qualified by reference to these filings and the exhibits attached thereto. You should review the complete document to evaluate these statements.

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**INCORPORATION BY REFERENCE**

The SEC allows us to incorporate by reference much of the information we file with the SEC, which means that we can disclose important information to you by referring you to those publicly available documents. The information that we incorporate by reference in this prospectus is considered to be part of this prospectus. Because we are incorporating by reference future filings with the SEC, this prospectus is continually updated and those future filings may modify or supersede some of the information included or incorporated in this prospectus. This means that you must look at all of the SEC filings that we incorporate by reference to determine if any of the statements in this prospectus or in any document previously incorporated by reference have been modified or superseded. This prospectus incorporates by reference the documents listed below (File No. 001-40925) and any future filings we make with the SEC under Sections 13(a), 13(c), 14 or 15(d) of the Securities Exchange Act of 1934, as amended (the "Exchange Act") (in each case, other than those documents or the portions of those documents not deemed to be filed) between the date of the initial registration statement and the effectiveness of the registration statement and following the effectiveness of the registration statement until the offering of the securities under the registration statement is terminated or completed:

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• Annual Report on [Form 10-K](http://www.sec.gov/Archives/edgar/data/../../../ix?doc=/Archives/edgar/data/1840233/000155837025002640/xlo-20241231x10k.htm) for the fiscal year ended December 31, 2024, as filed with the SEC on March 11, 2025;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• The information included in our definitive proxy statement on [Schedule 14A](http://www.sec.gov/Archives/edgar/data/1840233/000155837024005762/xlo-20240613xdef14a.htm) for the 2024 Annual Meeting of Stockholders, as filed with the SEC on April 
25, 2024, to the extent incorporated by reference into Part III of our Annual Report on [Form 10-K](http://www.sec.gov/Archives/edgar/data/../../../ix?doc=/Archives/edgar/data/1840233/000155837024004530/xlo-20231231x10k.htm) for the fiscal year ended on December 31, 2023;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• Current Reports on Form 8-K, as filed with the SEC on [January 21, 2025](http://www.sec.gov/Archives/edgar/data/../../../ix?doc=/Archives/edgar/data/0001840233/000155837025000291/xlo-20250121x8k.htm) , [February 12, 2025](http://www.sec.gov/Archives/edgar/data/../../../ix?doc=/Archives/edgar/data/0001840233/000155837025000823/xlo-20250210x8k.htm) , [March 11, 2025](http://www.sec.gov/Archives/edgar/data/../../../ix?doc=/Archives/edgar/data/1840233/000119312525051532/d897420d8k.htm) , and [April 8, 2025](http://www.sec.gov/Archives/edgar/data/../../../ix?doc=/Archives/edgar/data/1840233/000155837025004599/xlo-20250404x8k.htm) ; and

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• The description of our common stock contained in our Registration Statement on [Form 8-A](http://www.sec.gov/Archives/edgar/data/1840233/000110465921127173/tm2115750d15_8a12b.htm) , as filed with the SEC on October 
18, 2021, as the description therein has been updated and superseded by the description of our capital stock contained in [Exhibit 4.3](http://www.sec.gov/Archives/edgar/data/1840233/000155837022002552/xlo-20211231xex4d3.htm) to our Annual Report on [Form 10-K](http://www.sec.gov/Archives/edgar/data/1840233/000155837022002552/xlo-20211231x10k.htm) for the fiscal year ended December 31, 2021, as filed
with the SEC on March 1, 2022, and including any amendments or reports filed for the purpose of updating such description.

You may request a copy of these filings, at no cost, by writing or telephoning us at the following address or telephone number:

Xilio Therapeutics, Inc.

828 Winter Street, Suite 300

Waltham, Massachusetts 02451

Attn: Investor Relations

Phone: (857) 524-2466

E-mail: investors@xiliotx.com

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##### [**Table of Contents**](#toc)
**CAUTIONARY NOTE REGARDING FORWARD-LOOKING STATEMENTS**

This prospectus and the information incorporated by reference in this prospectus contain certain forward-looking statements within the meaning of Section 27A of the Securities Act of 1933, as amended (the "Securities Act") and Section 21E of the Exchange Act. All statements, other than statements of historical facts, contained in this prospectus are forward-looking statements. In some cases, you can identify forward-looking statements by words such as "aim," "anticipate," "believe," "contemplate," "continue," "could," "estimate," "expect," "intend," "may," "might," "plan," "potential," "predict," "project," "should," "target," "would," or the negative of these words or other comparable terminology, although not all forward-looking statements contain these identifying words.

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

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• the initiation, timing, progress and results of our research and development programs and preclinical studies and
clinical trials;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• our plans to develop and, if approved, subsequently commercialize any product candidates we may develop;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• the timing of and our ability to submit applications for, and obtain and, if approved, maintain regulatory
approvals for our product candidates;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• our estimates regarding expenses, future revenue, capital requirements and need for additional capital;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• our expectations regarding our ability to fund our operating expenses and capital expenditure requirements with
our cash and cash equivalents;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• the potential advantages of our current and future product candidates;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• the rate and degree of market acceptance of our product candidates, if approved;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• our estimates regarding the addressable patient population and potential market opportunity for our current and
future product candidates;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• our commercialization, marketing and manufacturing capabilities and strategy;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• our expectations regarding our ability to obtain and maintain intellectual property protection for our product
candidates;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• our ability to identify additional products, product candidates or technologies with significant commercial
potential that are consistent with our commercial objectives;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• the impact of government laws and regulations;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• our competitive position and expectations regarding developments and projections relating to our current or
future competitors and any competing therapies that are or become available;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• developments relating to our competitors and our industry;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• our ability to establish and maintain collaborations or obtain additional funding; and

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• our expectations regarding the time during which we will be an emerging growth company under the JOBS Act.

Any forward-looking statements in this prospectus reflect our current views with respect to future events or to our future financial performance and involve known and unknown risks, uncertainties and other important factors that may cause our actual results, performance or achievements to be materially different from any future results, performance or achievements expressed or implied by these forward-looking statements. We may not actually achieve the plans, intentions or expectations disclosed in our forward-looking statements, and you should not place undue reliance on our forward-looking statements. Actual results or events could differ

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materially from the plans, intentions and expectations disclosed in the forward-looking statements we make. You are cautioned that these forward-looking statements are only predictions and are subject to risks, uncertainties, and assumptions that are referenced in the section of any accompanying prospectus supplement entitled "Risk Factors."

You should also carefully review the risk factors and cautionary statements described in the other documents we file from time to time with the SEC, specifically our most recent Annual Report on Form 10-K, our Quarterly Reports on Form 10-Q and our Current Reports on Form 8-K, which could cause actual results or events to differ materially from the forward-looking statements that we make. Given these uncertainties, you should not place undue reliance on these forward-looking statements. Our forward-looking statements do not reflect the potential impact of any future acquisitions, mergers, dispositions, joint ventures, collaborations, partnerships or investments we may make or enter into.

You should read this prospectus, the documents incorporated by reference in this prospectus and the documents that we have filed as exhibits to the registration statement of which this prospectus is part completely and with the understanding that our actual future results may be materially different from what we expect. The forward-looking statements contained in this prospectus are made as of the date of this prospectus, and we do not assume any obligation to update any forward-looking statements, whether as a result of new information, future events or otherwise, except as required by applicable law.

Unless otherwise expressly stated, we obtained this industry, business, market and other data from our own internal estimates and research as well as from reports, research surveys, studies and similar data prepared by market research firms and other third parties, industry, medical and general publications, government data and similar sources. All of the market data used in this prospectus and the information incorporated herein involves a number of assumptions and limitations, and you are cautioned not to give undue weight to such data. Industry publications and third-party research, surveys and studies generally indicate that their information has been obtained from sources believed to be reliable, although they do not guarantee the accuracy or completeness of such information. Our estimates of the potential market opportunities for our product candidates include several key assumptions based on our industry knowledge, industry publications, third-party research and other surveys, which may be based on a small sample size and may fail to accurately reflect market opportunities. While we believe that our internal assumptions are reasonable, no independent source has verified such assumptions.

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**ABOUT XILIO THERAPEUTICS, INC.**

**Overview**

We are a clinical-stage biotechnology company discovering and developing tumor-activated, or masked, immuno-oncology ("I-O") therapies with the goal of significantly improving outcomes for people living with cancer without the systemic side effects of current I-O treatments. We are leveraging our proprietary platform to build a pipeline of novel, tumor-activated I-O molecules that are designed to optimize the therapeutic index by localizing anti-tumor activity within the tumor microenvironment, including masked antibodies, bispecifics, cytokines and immune cell engagers.

**Corporate Information**

Our principal executive offices are located at 828 Winter Street, Suite 300, Waltham, Massachusetts 02451, and our telephone number is (857) 524-2466. Our website address is www.xiliotx.com. The information contained on, or accessible through, our website is not incorporated by reference into this prospectus and should not be considered to be a part of this prospectus. We have included our website address in this prospectus solely as an inactive textual reference.

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**RISK FACTORS**

Investing in our securities involves significant risk. Prior to making a decision about investing in our securities, you should carefully consider the specific factors discussed under the heading "Risk Factors" contained in the applicable prospectus supplement and in any free-writing prospectus that we authorize for use in connection with an offering, together with all of the other information contained or incorporated by reference in the prospectus supplement or appearing or incorporated by reference in this prospectus, including the risks, uncertainties and assumptions discussed under the heading "Risk Factors" included in our most recent Annual Report on Form 10-K, our subsequent Quarterly Reports on Form 10-Q or our current reports on Form 8-K that we have filed with the SEC, which are incorporated herein by reference, and which may be amended, supplemented or superseded from time to time by other reports we file with the SEC in the future. 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 significantly affect our operations. The occurrence of any of these risks might cause you to lose all or part of your investment in the offered securities.

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**USE OF PROCEEDS**

We intend to use the net proceeds from the sale of any securities offered under this prospectus primarily for general corporate purposes unless otherwise indicated in the applicable prospectus supplement. General corporate purposes may include, without limitation, expenditures for research and development activities, clinical trials, acquisitions or in-licenses of products, product candidates or technologies, acquisitions of complementary companies or businesses, expenditures to build out our development and commercial capabilities, personnel-related expenditures, collaborations, working capital and capital expenditures. We may temporarily invest the net proceeds in a variety of capital preservation instruments, including short-term, investment grade, interest bearing instruments and U.S. government securities, until they are used for their stated purpose. We have not determined the amount of net proceeds to be used specifically for such purposes. As a result, our management will have broad discretion over the allocation of the net proceeds of any offering.

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**DESCRIPTION OF CAPITAL STOCK**

The following description of our capital stock is intended as a summary only and therefore is not a complete description of our capital stock. This description is based upon, and is qualified by reference to, our restated certificate of incorporation, our second amended and restated bylaws and applicable provisions of Delaware corporate law. You should read our restated certificate of incorporation and second amended and restated bylaws, which are filed as exhibits to the registration statement of which this prospectus forms a part, for the provisions that are important to you.

Our authorized capital stock consists of 200,000,000 shares of common stock, par value $0.0001 per share, and 5,000,000 shares of preferred stock, par value $0.0001 per share, all of which preferred stock is undesignated. Our common stock is registered under Section 12(b) of the Exchange Act.

**Common Stock**

*Annual Meeting.* Annual meetings of our stockholders are held on the date designated in accordance with our second amended and restated bylaws. Written notice must be mailed to each stockholder entitled to vote not less than ten nor more than 60 days before the date of the meeting. The presence in person or by proxy of the holders of record of a majority of our issued and outstanding shares entitled to vote at such meeting constitutes a quorum for the transaction of business at meetings of the stockholders. Special meetings of the stockholders may be called for any purpose by the board of directors. Except as may be otherwise provided by applicable law, our restated certificate of incorporation or our second amended and restated bylaws, all elections shall be decided by a plurality, and all other questions shall be decided by a majority, of the votes cast by stockholders entitled to vote thereon at a duly held meeting of stockholders at which a quorum is present.

*Voting Rights*. Each holder of common stock is entitled to one vote for each share held of record on all matters to be voted upon by stockholders, including the election of directors. Our restated certificate of incorporation and second amended and restated bylaws do not provide for cumulative voting rights. Except as otherwise provided by law, our restated certificate of incorporation or our second amended and restated bylaws, in all matters other than the election of directors, the affirmative vote of the majority of the shares present in person or represented by proxy at a meeting at which a quorum is present and entitled to vote on the subject matter shall be the act of the stockholders. Directors shall be elected by a plurality of the shares present in person or represented by proxy at a meeting at which a quorum is present and entitled to vote on the election of directors.

*Dividends*. Subject to the rights, powers and preferences of any outstanding preferred stock, and except as provided by law or in our restated certificate of incorporation, dividends may be declared and paid or set aside for payment on the common stock out of legally available assets or funds when and as declared by the board of directors. The payment of dividends is contingent upon our revenue and earnings, capital requirements, and general financial condition, as well as contractual restrictions and other considerations deemed to be relevant by our board of directors.

*Liquidation, Dissolution and Winding Up*. Subject to the rights, powers and preferences of any outstanding preferred stock, in the event of our liquidation, dissolution or winding up, our net assets will be distributed pro rata to the holders of our common stock.

*Other Rights*.

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• Holders of the common stock have no right to:

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• convert the stock into any other security;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• have the stock redeemed;

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&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• purchase additional stock; or

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• maintain their proportionate ownership interest.

Holders of shares of the common stock are not required to make additional capital contributions.

*Transfer Agent and Registrar*. Computershare Trust Company, N.A. is transfer agent and registrar for the common stock.

**Preferred Stock**

We are authorized to issue "blank check" preferred stock, which may be issued in one or more series upon authorization of our board of directors. Our board of directors is authorized to fix the designations, powers, preferences and the relative, participating, optional or other special rights and any qualifications, limitations and restrictions of the shares of each series of preferred stock. The authorized shares of our preferred stock are available for issuance without further action by our stockholders, unless such action is required by applicable law or the rules of any stock exchange on which our securities may be listed. If the approval of our stockholders is not required for the issuance of shares of our preferred stock, our board may determine not to seek stockholder approval. The specific terms of any series of preferred stock offered pursuant to this prospectus will be described in the prospectus supplement relating to that series of preferred stock.

A series of our preferred stock could, depending on the terms of such series, impede the completion of a merger, tender offer or other takeover attempt. Our board of directors will make any determination to issue preferred shares based upon its judgment as to the best interests of our stockholders. Our directors, in so acting, could issue preferred stock having terms that could discourage an acquisition attempt through which an acquirer may be able to change the composition of our board of directors, including a tender offer or other transaction that some, or a majority, of our stockholders might believe to be in their best interests or in which stockholders might receive a premium for their stock over the then-current market price of the stock.

The preferred stock has the terms described below unless otherwise provided in the prospectus supplement relating to a particular series of preferred stock. You should read the prospectus supplement relating to the particular series of preferred stock being offered for specific terms, including:

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• the designation and stated value per share of the preferred stock and the number of shares offered;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• the amount of liquidation preference per share;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• the price at which the preferred stock will be issued;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• the dividend rate, or method of calculation of dividends, the dates on which dividends will be payable, whether
dividends will be cumulative or noncumulative and, if cumulative, the dates from which dividends will commence to accumulate;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• any redemption or sinking fund provisions;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• if other than the currency of the United States, the currency or currencies including composite currencies in
which the preferred stock is denominated and/or in which payments will or may be payable;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• any conversion provisions; and

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• any other rights, preferences, privileges, limitations and restrictions on the preferred stock.

The preferred stock will, when issued, be fully paid and non-assessable. Unless otherwise specified in the prospectus supplement, each series of preferred stock will rank equally as to dividends and liquidation rights in all respects with each other series of preferred stock. The rights of holders of shares of each series of preferred stock will be subordinate to those of our general creditors.

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*Rank*. Unless otherwise specified in the prospectus supplement, the preferred stock will, with respect to dividend rights and rights upon our liquidation, dissolution or winding up of our affairs, rank:

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• senior to our common stock and to all equity securities ranking junior to such preferred stock with respect to
dividend rights or rights upon our liquidation, dissolution or winding up of our affairs;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• on a parity with all equity securities issued by us, the terms of which specifically provide that such equity
securities rank on a parity with the preferred stock with respect to dividend rights or rights upon our liquidation, dissolution or winding up of our affairs; and

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• junior to all equity securities issued by us, the terms of which specifically provide that such equity securities
rank senior to the preferred stock with respect to dividend rights or rights upon our liquidation, dissolution or winding up of our affairs.

The term "equity securities" does not include convertible debt securities.

*Dividends*. Holders of preferred stock of each series will be entitled to receive, when, as and if declared by our board of directors, cash dividends at such rates and on such dates described in the prospectus supplement. Different series of preferred stock may be entitled to dividends at different rates or based on different methods of calculation. The dividend rate may be fixed or variable or both. Dividends will be payable to the holders of record as they appear on our stock books on record dates fixed by our board of directors, as specified in the applicable prospectus supplement.

Dividends on any series of preferred stock may be cumulative or noncumulative, as described in the applicable prospectus supplement. If our board of directors does not declare a dividend payable on a dividend payment date on any series of noncumulative preferred stock, then the holders of that noncumulative preferred stock will have no right to receive a dividend for that dividend payment date, and we will have no obligation to pay the dividend accrued for that period, whether or not dividends on that series are declared payable on any future dividend payment dates. Dividends on any series of cumulative preferred stock will accrue from the date we initially issue shares of such series or such other date specified in the applicable prospectus supplement.

No dividends may be declared or paid or funds set apart for the payment of any dividends on any parity securities unless full dividends have been paid or set apart for payment on the preferred stock. If full dividends are not paid, the preferred stock will share dividends pro rata with the parity securities.

No dividends may be declared or paid or funds set apart for the payment of dividends on any junior securities unless full dividends for all dividend periods terminating on or prior to the date of the declaration or payment will have been paid or declared and a sum sufficient for the payment set apart for payment on the preferred stock.

*Liquidation Preference*. Upon any voluntary or involuntary liquidation, dissolution or winding up of our affairs, then, before we make any distribution or payment to the holders of any common stock or any other class or series of our capital stock ranking junior to the preferred stock in the distribution of assets upon any liquidation, dissolution or winding up of our affairs, the holders of each series of preferred stock shall be entitled to receive out of assets legally available for distribution to stockholders, liquidating distributions in the amount of the liquidation preference per share set forth in the prospectus supplement, plus any accrued and unpaid dividends thereon. Such dividends will not include any accumulation in respect of unpaid noncumulative dividends for prior dividend periods. Unless otherwise specified in the prospectus supplement, after payment of the full amount of their liquidating distributions, the holders of preferred stock will have no right or claim to any of our remaining assets. Upon any such voluntary or involuntary liquidation, dissolution or winding up, if our available assets are insufficient to pay the amount of the liquidating distributions on all outstanding preferred stock and the corresponding amounts payable on all other classes or series of our capital stock ranking on parity with the preferred stock and all other such classes or series of shares of capital stock ranking on parity with the

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preferred stock in the distribution of assets, then the holders of the preferred stock and all other such classes or series of capital stock ranking on parity with the preferred stock will share ratably in any such distribution of assets in proportion to the full liquidating distributions to which they would otherwise be entitled.

Upon any such liquidation, dissolution or winding up and if we have made liquidating distributions in full to all holders of preferred stock, we will distribute our remaining assets among the holders of any other classes or series of capital stock ranking junior to the preferred stock according to their respective rights and preferences and, in each case, according to their respective number of shares. For such purposes, our consolidation or merger with or into any other corporation, trust or entity, or the sale, lease or conveyance of all or substantially all of our property or assets will not be deemed to constitute a liquidation, dissolution or winding up of our affairs.

*Redemption*. If so provided in the applicable prospectus supplement, the preferred stock will be subject to mandatory redemption or redemption at our option, as a whole or in part, in each case upon the terms, at the times and at the redemption prices set forth in such prospectus supplement.

The prospectus supplement relating to a series of preferred stock that is subject to mandatory redemption will specify the number of shares of preferred stock that shall be redeemed by us in each year commencing after a date to be specified, at a redemption price per share to be specified, together with an amount equal to all accrued and unpaid dividends thereon to the date of redemption. Unless the shares have a cumulative dividend, such accrued dividends will not include any accumulation in respect of unpaid dividends for prior dividend periods. We may pay the redemption price in cash or other property, as specified in the applicable prospectus supplement. If the redemption price for preferred stock of any series is payable only from the net proceeds of the issuance of shares of our capital stock, the terms of such preferred stock may provide that, if no such shares of our capital stock shall have been issued or to the extent the net proceeds from any issuance are insufficient to pay in full the aggregate redemption price then due, such preferred stock shall automatically and mandatorily be converted into the applicable shares of our capital stock pursuant to conversion provisions specified in the applicable prospectus supplement.

Notwithstanding the foregoing, we will not redeem any preferred stock of a series unless:

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• if that series of preferred stock has a cumulative dividend, we have declared and paid or contemporaneously
declare and pay or set aside funds to pay full cumulative dividends on the preferred stock for all past dividend periods and the then current dividend period; or

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• if such series of preferred stock does not have a cumulative dividend, we have declared and paid or
contemporaneously declare and pay or set aside funds to pay full dividends for the then current dividend period.

In addition, we will not acquire any preferred stock of a series unless:

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• if that series of preferred stock has a cumulative dividend, we have declared and paid or contemporaneously
declare and pay or set aside funds to pay full cumulative dividends on all outstanding shares of such series of preferred stock for all past dividend periods and the then current dividend period; or

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• if that series of preferred stock does not have a cumulative dividend, we have declared and paid or
contemporaneously declare and pay or set aside funds to pay full dividends on the preferred stock of such series for the then current dividend period.

However, at any time we may purchase or acquire preferred stock of that series (1) pursuant to a purchase or exchange offer made on the same terms to holders of all outstanding preferred stock of such series or (2) by conversion into or exchange for shares of our capital stock ranking junior to the preferred stock of such series as to dividends and upon liquidation.

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If fewer than all of the outstanding shares of preferred stock of any series are to be redeemed, we will determine the number of shares that may be redeemed pro rata from the holders of record of such shares in proportion to the number of such shares held or for which redemption is requested by such holder or by any other equitable manner that we determine. Such determination will reflect adjustments to avoid redemption of fractional shares.

Unless otherwise specified in the prospectus supplement, we will mail notice of redemption at least 10 days but not more than 60 days before the redemption date to each holder of record of preferred stock to be redeemed at the address shown on our stock transfer books. Each notice shall state:

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• the redemption date;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• the number of shares and series of preferred stock to be redeemed;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• the redemption price;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• the place or places where certificates for such preferred stock are to be surrendered for payment of the
redemption price;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• that dividends on the shares to be redeemed will cease to accrue on such redemption date;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• the date on which the holder's conversion rights, if any, as to such shares shall terminate; and

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• the specific number of shares to be redeemed from each such holder if fewer than all the shares of any series are
to be redeemed.

If notice of redemption has been given and we have set aside the funds necessary for such redemption in trust for the benefit of the holders of any shares called for redemption, then from and after the redemption date, dividends will cease to accrue on such shares, and all rights of the holders of such shares will terminate, except the right to receive the redemption price.

*Voting Rights*. Holders of preferred stock will not have any voting rights, except as required by law or as indicated in the applicable prospectus supplement.

Unless otherwise provided for under the terms of any series of preferred stock, no consent or vote of the holders of shares of preferred stock or any series thereof shall be required for any amendment to our restated certificate of incorporation that would increase the number of authorized shares of preferred stock or the number of authorized shares of any series thereof or decrease the number of authorized shares of preferred stock or the number of authorized shares of any series thereof (but not below the number of authorized shares of preferred stock or such series, as the case may be, then outstanding).

*Conversion Rights*. The terms and conditions, if any, upon which any series of preferred stock is convertible into shares of our common stock will be set forth in the applicable prospectus supplement relating thereto. Such terms will include the number of shares of common stock into which the shares of preferred stock are convertible, the conversion price, rate or manner of calculation thereof, the conversion period, provisions as to whether conversion will be at our option or at the option of the holders of the preferred stock, the events requiring an adjustment of the conversion price and provisions affecting conversion in the event of the redemption.

*Transfer Agent and Registrar*. The transfer agent and registrar for the preferred stock will be set forth in the applicable prospectus supplement.

**Provisions of Our Restated Certificate of Incorporation and Second Amended and Restated Bylaws and Delaware Law That May Have Anti-Takeover Effects**

Certain provisions of our restated certificate of incorporated and second amended and restated bylaws may have the effect of making it more difficult for a third party to acquire, or of discouraging a third party from

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attempting to acquire, control of us. Such provisions could limit the price that certain investors might be willing to pay in the future for shares of our common stock and may limit the ability of stockholders to remove current management or directors or approve transactions that stockholders may deem to be in their best interest and, therefore, could adversely affect the price of our common stock.

*No Cumulative Voting.* The Delaware General Corporation Law ("DGCL") provides that stockholders are not entitled to the right to accumulate votes in the election of directors unless our restated certificate of incorporation provides otherwise. Our restated certificate of incorporation does not provide for cumulative voting.

*Board of Directors*. Our restated certificate of incorporation provides for a board of directors divided as nearly equally as possible into three classes. Each class is elected to a term expiring at the annual meeting of stockholders held in the third year following the year of such election. The number of directors comprising our board of directors is fixed from time to time by the board of directors.

*Removal of Directors by Stockholders*. Delaware law provides that members of our board of directors may only be removed for cause by a vote of the holders of at least 75% of the outstanding shares entitled to vote on the election of the directors.

*Board Vacancies Filled Only by Majority of Directors Then in Office*. Vacancies and newly created seats on our board may be filled only by our board of directors. Further, only our board of directors may determine the number of directors on our board. The inability of stockholders to determine the number of directors or to fill vacancies or newly created seats on the board makes it more difficult to change the composition of our board of directors.

*Stockholder Nomination of Directors*. Our second amended and restated bylaws provide that a stockholder must notify us in writing of any stockholder nomination of a director not earlier than the 120th day and not later than the 90th day prior to the first anniversary of the preceding year's annual meeting; provided, that if the date of the annual meeting is advanced by more than 30 days or delayed by more than 60 days from such anniversary date, notice by the stockholder to be timely must be so delivered not earlier than the 120th day prior to the date of such annual meeting and not later than the later of (x) the 90th day prior to the date of such annual meeting and (y) the 10th day following the day on which notice of the date of such annual meeting was given or public announcement of the date of such annual meeting is first made by us, whichever first occurs.

*No Action By Written Consent*. Our restated certificate of incorporation provides that our stockholders may not act by written consent and may only act at duly called meetings of stockholders.

*Undesignated Preferred Stock.* As discussed above, our board of directors has the ability to issue preferred stock with voting or other rights or preferences that could impede the success of any attempt to change control of our company. These and other provisions may have the effect of deferring hostile takeovers or delaying changes in control or management of us.

These provisions of Delaware law, our restated certificate of incorporation and our second amended and restated bylaws may have the effect of deterring hostile takeovers or delaying changes in our control or in our management. These provisions are intended to enhance the likelihood of continued stability in the composition of our board of directors and in the policies they implement, and to discourage certain types of transactions that may involve an actual or threatened change of our control. These provisions are designed to reduce our vulnerability to an unsolicited acquisition proposal. The provisions also are intended to discourage certain tactics that may be used in proxy fights. However, such provisions could have the effect of discouraging others from making tender offers for our shares and, as a consequence, they also may inhibit fluctuations in the market price of our shares that could result from actual or rumored takeover attempts.

*Exclusive Forum Selection*. Our restated certificate of incorporation provides that, unless we consent in writing to the selection of an alternative forum, the Court of Chancery of the State of Delaware (or, if the Court

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of Chancery of the State of Delaware does not have jurisdiction, the federal district court for the District of Delaware) shall, to the fullest extent permitted by law, be the sole and exclusive forum for (1) any derivative action or proceeding brought on our behalf, (2) any action asserting a claim of breach of a fiduciary duty owed by any of our directors, officers, other employees or stockholders to our company or our stockholders, (3) any action asserting a claim arising pursuant to any provision of the DGCL or as to which the DGCL confers jurisdiction on the Court of Chancery of the State of Delaware or (4) any action asserting a claim arising pursuant to any provision of our restated certificate of incorporation or second amended or restated bylaws (in each case, as they may be amended from time to time) or governed by the internal affairs doctrine. This choice of forum provision will not apply to actions arising under the Securities Act, the Exchange Act or any other claim for which the federal courts have exclusive jurisdiction. Unless we consent in writing to the selection of an alternative forum, the federal district courts of the United States of America shall, to the fullest extent permitted by law, be the sole and exclusive forum for the resolution of any claims arising under the Securities Act. Although our restated certificate of incorporation contains the choice of forum provisions described above, it is possible that a court could rule that such a provision is inapplicable for a particular claim or action or that such provision is unenforceable.

*Delaware Business Combination Statute.* We are subject to Section 203 of the DGCL ("Section 203"), which prohibits a Delaware corporation from engaging in business combinations with an interested stockholder. An interested stockholder is generally defined as an entity or person beneficially owning 15% or more of the outstanding voting stock of the corporation or any entity or person affiliated with or controlling or controlled by such entity or person ("interested stockholder"). Section 203 provides that an interested stockholder may not engage in business combinations with the corporation for a period of three years after the date that such stockholder became an interested stockholder, with the following exceptions:

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• before such date, the board of directors of the corporation approved either the business combination or the
transaction that resulted in the stockholder becoming an interested stockholder;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• upon completion of the transaction that resulted in the stockholder becoming an interested stockholder, the
interested stockholder owned at least 85% of the voting stock of the corporation outstanding at the time the transaction began, excluding for purposes of determining the voting stock outstanding (but not the outstanding voting stock owned by the
interested stockholder) those shares owned (i) by persons who are directors and also officers and (ii) employee stock plans in which employee participants do not have the right to determine confidentially whether shares held subject to the
plan will be tendered in a tender or exchange offer; or

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• on or after such date, the business combination is approved by the board of directors and authorized at an annual
or special meeting of the stockholders, and not by written consent, by the affirmative vote of at least 66 2/3% of the outstanding voting stock that is not owned by the interested stockholder.

In general, Section 203 defines business combinations to include the following:

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• any merger or consolidation involving the corporation and the interested stockholder;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• any sale, lease, transfer, pledge or other disposition of 10% or more of the assets of the corporation to or with
the interested stockholder;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• subject to certain exceptions, any transaction that results in the issuance or transfer by the corporation of any
stock of the corporation to the interested stockholder;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• any transaction involving the corporation that has the effect of increasing the proportionate share of the stock
or any class or series of the corporation beneficially owned by the interested stockholder; or

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• the receipt by the interested stockholder of the benefit of any loss, advances, guarantees, pledges or other
financial benefits by or through the corporation.

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**DESCRIPTION OF DEBT SECURITIES**

The following description summarizes the general terms and provisions of the debt securities that we may offer and sell from time to time. We will describe the specific terms of the debt securities and the extent, if any, to which the general provisions summarized below apply to any series of debt securities, in the prospectus supplement relating to such series and any applicable free writing prospectus that we may authorize to be delivered. As used in this "Description of Debt Securities" the term "debt securities," means the senior and subordinated debt securities that we issue and the trustee authenticates and delivers under the applicable indenture. When we refer to "the Company," "we," "our" and "us" in this section, we mean Xilio Therapeutics, Inc. excluding, unless the context otherwise requires or as otherwise expressly stated, our subsidiaries.

We may issue senior debt securities from time to time, in one or more series under a senior indenture to be entered into between us and a senior trustee to be named in a prospectus supplement, which we refer to as the senior trustee. We may issue subordinated debt securities from time to time, in one or more series under a subordinated indenture to be entered into between us and a subordinated trustee to be named in a prospectus supplement, which we refer to as the subordinated trustee. The forms of senior indenture and subordinated indenture are filed as exhibits to the registration statement of which this prospectus forms a part. The senior indenture and the subordinated indenture are referred to individually as an indenture and together as the indentures and the senior trustee and the subordinated trustee are referred to individually as a trustee and together as the trustees. This section summarizes some of the provisions of the indentures and is qualified in its entirety by the specific text of the indentures, including definitions of terms used in the indentures. Wherever we refer to particular sections of, or defined terms in, the indentures, those sections or defined terms are incorporated by reference in this prospectus or the applicable prospectus supplement. You should review the indentures that are filed as exhibits to the registration statement of which this prospectus forms a part for additional information.

Neither indenture will limit the amount of debt securities that we may issue. The applicable indenture will provide that debt securities may be issued up to an aggregate principal amount authorized from time to time by us and may be payable in any currency or currency unit designated by us or in amounts determined by reference to an index.

**General**

The senior debt securities will constitute our unsecured and unsubordinated general obligations and will rank equally in right of payment with our other unsecured and unsubordinated obligations. The subordinated debt securities will constitute our unsecured and subordinated general obligations and will be junior in right of payment to our senior indebtedness (including senior debt securities), as described under the heading "— Certain Terms of the Subordinated Debt Securities — Subordination." The debt securities will be structurally subordinated to all existing and future indebtedness and other liabilities of our subsidiaries unless such subsidiaries expressly guarantee such debt securities.

The debt securities will be our unsecured obligations. Any secured debt or other secured obligations will be effectively senior to the debt securities to the extent of the value of the assets securing such debt or other obligations.

The applicable prospectus supplement and/or free writing prospectus will include any additional or different terms of the debt securities of any series being offered, including the following terms:

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• the title and type of the debt securities;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• whether the debt securities will be senior or subordinated debt securities, and, with respect to any subordinated
debt securities the terms on which they are subordinated;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• the initial aggregate principal amount of the debt securities;

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&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• the price or prices at which we will sell the debt securities;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• the maturity date or dates of the debt securities and the right, if any, to extend such date or dates;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• the rate or rates, if any, at which the debt securities will bear interest, or the method of determining such
rate or rates;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• the date or dates from which such interest will accrue, the interest payment dates on which such interest will be
payable or the method of determination of such dates;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• the right, if any, to extend the interest payment periods and the duration of that extension;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• the manner of paying principal and interest and the place or places where principal and interest will be payable;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• the denominations of the debt securities if other than $2,000 or multiples of $1,000;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• provisions for a sinking fund, purchase fund or other analogous fund, if any;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• any redemption dates, prices, obligations and restrictions on the debt securities;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• the currency, currencies or currency units in which the debt securities will be denominated and the
currency, currencies or currency units in which principal and interest, if any, on the debt securities may be payable;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• any conversion or exchange features of the debt securities;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• whether the debt securities will be subject to the defeasance provisions in the indenture;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• whether the debt securities will be issued in definitive or global form or in definitive form only upon
satisfaction of certain conditions;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• whether the debt securities will be guaranteed as to payment or performance;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• any special tax implications of the debt securities;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• any events of defaults or covenants in addition to or in lieu of those set forth in the indenture; and

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• any other material terms of the debt securities.

When we refer to "principal" in this section with reference to the debt securities, we are also referring to "premium, if any."

We may from time to time, without notice to or the consent of the holders of any series of debt securities, create and issue further debt securities of any such series ranking equally with the debt securities of such series in all respects (or in all respects other than (1) the payment of interest accruing prior to the issue date of such further debt securities or (2) the first payment of interest following the issue date of such further debt securities). Such further debt securities may be consolidated and form a single series with the debt securities of such series and have the same terms as to status, redemption or otherwise as the debt securities of such series.

You may present debt securities for exchange and you may present debt securities for transfer in the manner, at the places and subject to the restrictions set forth in the debt securities and the applicable prospectus supplement. We will provide you those services without charge, although you may have to pay any tax or other governmental charge payable in connection with any exchange or transfer, as set forth in the indenture.

Debt securities may bear interest at a fixed rate or a floating rate. Debt securities bearing no interest or interest at a rate that at the time of issuance is below the prevailing market rate (original issue discount securities) may be sold at a discount below their stated principal amount. U.S. federal income tax considerations applicable to any such discounted debt securities or to certain debt securities issued at par which are treated as having been issued at a discount for U.S. federal income tax purposes will be described in the applicable prospectus supplement.

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We may issue debt securities with the principal amount payable on any principal payment date, or the amount of interest payable on any interest payment date, to be determined by reference to one or more currency exchange rates, securities or baskets of securities, commodity prices or indices. You may receive a payment of principal on any principal payment date, or a payment of interest on any interest payment date, that is greater than or less than the amount of principal or interest otherwise payable on such dates, depending on the value on such dates of the applicable currency, security or basket of securities, commodity or index. Information as to the methods for determining the amount of principal or interest payable on any date, the currencies, securities or baskets of securities, commodities or indices to which the amount payable on such date is linked and certain related tax considerations will be set forth in the applicable prospectus supplement.

**Certain Terms of the Senior Debt Securities**

*Covenants.* Unless we indicate otherwise in a prospectus supplement with respect to a particular series of senior debt securities, the senior debt securities will not contain any financial or restrictive covenants, including covenants restricting either us or any of our subsidiaries from incurring, issuing, assuming or guaranteeing any indebtedness secured by a lien on any of our or our subsidiaries' property or capital stock, or restricting either us or any of our subsidiaries from entering into sale and leaseback transactions.

*Consolidation, Merger and Sale of Assets.* Unless we indicate otherwise in a prospectus supplement with respect to a particular series of senior debt securities, we may not consolidate with or merge into any other person, in a transaction in which we are not the surviving corporation, or convey, transfer or lease our properties and assets substantially as an entirety to any person, in either case, unless:

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• the successor entity, if any, is a U.S. corporation, limited liability company, partnership or trust;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• the successor entity assumes our obligations on the senior debt securities and under the senior indenture;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• immediately after giving effect to the transaction, no default or event of default shall have occurred and be
continuing; and

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• we have delivered to the senior trustee an officer's certificate and an opinion of counsel, each stating
that the consolidation, merger, conveyance, transfer or lease and, if a supplemental indenture is required in connection with such transaction, such supplemental indenture, comply with the senior indenture and all conditions precedent provided for
in the senior indenture relating to such transaction have been complied with.

The restrictions described in the bullets above do not apply (1) to our consolidation with or merging into one of our affiliates, if our board of directors determines in good faith that the purpose of the consolidation or merger is principally to change our state of incorporation or our form of organization to another form or (2) if we merge with or into a single direct or indirect wholly-owned subsidiary of ours.

The surviving business entity will succeed to, and be substituted for, us under the senior indenture and the senior debt securities and, except in the case of a lease, we shall be released from all obligations under the senior indenture and the senior debt securities.

*No Protection in the Event of a Change in Control.* Unless we indicate otherwise in a prospectus supplement with respect to a particular series of senior debt securities, the senior debt securities will not contain any provisions that may afford holders of the senior 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).

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*Events of Default.* Unless we indicate otherwise in a prospectus supplement with respect to a particular series of senior debt securities, the following are events of default under the senior indenture with respect to senior debt securities of each series:

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• failure to pay interest on any senior debt securities of such series when due and payable, if that default
continues for a period of 30 days (or such other period as may be specified for such series);

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• failure to pay principal on the senior debt securities of such series when due and payable whether at maturity,
upon redemption, by declaration or otherwise (and, if specified for such series, the continuance of such failure for a specified period);

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• default in the performance of or breach of any of our covenants or agreements in the senior indenture applicable
to senior debt securities of such series, other than a covenant breach which is specifically dealt with elsewhere in the senior indenture, and that default or breach continues for a period of 90 days after we receive written notice from the
trustee or from the holders of 25% or more in aggregate principal amount of the senior debt securities of such series;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• certain events of bankruptcy or insolvency, whether or not voluntary; and

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• any other event of default provided for in such series of senior debt securities as may be specified in the
applicable prospectus supplement.

Unless we indicate otherwise in a prospectus supplement with respect to a particular series of senior debt securities, the default by us under any other debt, including any other series of our debt securities, is not a default under the senior indenture.

If an event of default other than an event of default specified in the fourth bullet point above occurs with respect to a series of senior debt securities and is continuing under the senior indenture, then, and in each such case, either the trustee or the holders of not less than 25% in aggregate principal amount of such series then outstanding under the senior indenture (each such series voting as a separate class) by written notice to us and to the trustee, if such notice is given by the holders, may, and the trustee at the request of such holders shall, declare the principal amount of and accrued interest on such series of senior debt securities to be immediately due and payable, and upon this declaration, the same shall become immediately due and payable.

If an event of default specified in the fourth bullet point above occurs and is continuing, the entire principal amount of and accrued interest on each series of senior debt securities then outstanding shall automatically become immediately due and payable.

Unless otherwise specified in the prospectus supplement relating to a series of senior debt securities originally issued at a discount, the amount due upon acceleration shall include only the original issue price of the senior debt securities, the amount of original issue discount accrued to the date of acceleration and accrued interest, if any.

Upon certain conditions, declarations of acceleration may be rescinded and annulled and past defaults may be waived by the holders of a majority in aggregate principal amount of all the senior debt securities of such series affected by the default, each series voting as a separate class. Furthermore, subject to various provisions in the senior indenture, the holders of a majority in aggregate principal amount of a series of senior debt securities, by notice to the trustee, may waive a continuing default or event of default with respect to such senior debt securities and its consequences, except a default in the payment of principal of or interest on such senior debt securities (other than any such default in payment resulting solely from an acceleration of the senior debt securities) or in respect of a covenant or provision of the senior indenture which cannot be modified or amended without the consent of the holders of each such senior debt security. Upon any such waiver, such default shall cease to exist, and any event of default with respect to such senior debt securities shall be deemed to have been cured, for every purpose of the senior indenture; but no such waiver shall extend to any subsequent or other default or event of default or impair any right consequent thereto.

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The holders of a majority in aggregate principal amount of a series of senior debt securities may 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 such senior debt securities. However, the trustee may refuse to follow any direction that conflicts with law or the senior indenture, that may involve the trustee in personal liability or that the trustee determines in good faith may be unduly prejudicial to the rights of holders of such series of senior debt securities not joining in the giving of such direction and may take any other action it deems proper that is not inconsistent with any such direction received from holders of such series of senior debt securities. A holder may not pursue any remedy with respect to the senior indenture or any series of senior debt securities unless:

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• the holder gives the trustee written notice of a continuing event of default;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• the holders of at least 25% in aggregate principal amount of such series of senior debt securities make a written
request to the trustee to pursue the remedy in respect of such event of default;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• the requesting holder or holders offer the trustee indemnity satisfactory to the trustee against any costs,
liability or expense;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• the trustee does not comply with the request within 60 days after receipt of the request and the offer of
indemnity; and

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• during such 60-day period, the holders of a majority in aggregate
principal amount of such series of senior debt securities do not give the trustee a direction that is inconsistent with the request.

These limitations, however, do not apply to the right of any holder of a senior debt security of any affected series to receive payment of the principal of and interest on such senior debt security in accordance with the terms of such debt security, or to bring suit for the enforcement of any such payment in accordance with the terms of such debt security, on or after the due date for the senior debt securities, which right shall not be impaired or affected without the consent of the holder.

The senior indenture requires certain of our officers to certify, on or before a fixed date in each year in which any senior debt security is outstanding, as to their knowledge of our compliance with all covenants, agreements and conditions under the senior indenture.

*Satisfaction and Discharge*. We can satisfy and discharge our obligations to holders of any series of debt securities if:

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• we have paid or caused to be paid the principal of and interest on all senior debt securities of such series
(with certain limited exceptions) when due and payable; or

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• we deliver to the senior trustee for cancellation all senior debt securities of such series theretofore
authenticated under the senior indenture (with certain limited exceptions); or

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• all senior debt securities of such series have become due and payable or will become due and payable within one
year (or are to be called for redemption within one year under arrangements satisfactory to the senior trustee) and we deposit in trust an amount of cash or a combination of cash and U.S. government or U.S. government agency obligations (or in the
case of senior debt securities denominated in a foreign currency, foreign government securities or foreign government agency securities) sufficient to make interest, principal and any other payments on the debt securities of that series on their
various due dates;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• and if, in any such case, we also pay or cause to be paid all other sums payable under the senior indenture, as
and when the same shall be due and payable and we deliver to the senior trustee an officer's certificate and an opinion of counsel, each stating that these conditions have been satisfied.

Under current U.S. federal income tax law, the deposit and our legal release from the debt securities would be treated as though we took back your debt securities and gave you your share of the cash and debt securities or

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bonds deposited in trust. In that event, you could recognize gain or loss on the debt securities you give back to us. Purchasers of the debt securities should consult their own advisers with respect to the tax consequences to them of such deposit and discharge, including the applicability and effect of tax laws other than the U.S. federal income tax law.

*Defeasance.*Unless the applicable prospectus supplement provides otherwise, the following discussion of legal defeasance and covenant defeasance will apply to any series of debt securities issued under the indentures.

*Legal Defeasance*.We can legally release ourselves from any payment or other obligations on the debt securities of any series (called "legal defeasance") if certain conditions are met, including the following:

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• We deposit in trust for your benefit and the benefit of all other direct holders of the debt securities of the
same series cash or a combination of cash and U.S. government or U.S. government agency obligations (or, in the case of senior debt securities denominated in a foreign currency, foreign government or foreign government agency obligations) that will
generate enough cash to make interest, principal and any other payments on the debt securities of that series on their various due dates.

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• There is a change in current U.S. federal income tax law or an IRS ruling that lets us make the above deposit
without causing you to be taxed on the debt securities any differently than if we did not make the deposit and instead repaid the debt securities ourselves when due. Under current U.S. federal income tax law, the deposit and our legal release from
the debt securities would be treated as though we took back your debt securities and gave you your share of the cash and debt securities or bonds deposited in trust. In that event, you could recognize gain or loss on the debt securities you give
back to us.

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• We deliver to the trustee a legal opinion of our counsel confirming the tax law change or ruling described above.

If we accomplish legal defeasance, as described above, you would have to rely solely on the trust deposit for repayment of the debt securities. You could not look to us for repayment in the event of any shortfall.

*Covenant Defeasance*.Without any change in current U.S. federal tax law, we can make the same type of deposit described above and be released from some of the covenants in the debt securities (called "covenant defeasance"). In that event, you would lose the protection of those covenants but would gain the protection of having money and securities set aside in trust to repay the debt securities. In order to achieve covenant defeasance, we must do the following (among other things):

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• deposit in trust for your benefit and the benefit of all other direct holders of the debt securities of the same
series cash or a combination of cash and U.S. government or U.S. government agency obligations (or, in the case of senior debt securities denominated in a foreign currency, foreign government or foreign government agency obligations) that will
generate enough cash to make interest, principal and any other payments on the debt securities of that series on their various due dates.

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• deliver to the trustee a legal opinion of our counsel confirming that under current U.S. federal income tax law
we may make the above deposit without causing you to be taxed on the debt securities any differently than if we did not make the deposit and instead repaid the debt securities ourselves when due.

If we accomplish covenant defeasance, you could still look to us for repayment of the debt securities if there were a shortfall in the trust deposit. In fact, if one of the events of default occurred (such as our bankruptcy) and the debt securities become immediately due and payable, there may be such a shortfall. Depending on the events causing the default, you may not be able to obtain payment of the shortfall.

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*Modification and Waiver.* We and the trustee may amend or supplement the senior indenture or the senior debt securities of any series without the consent of any holder:

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• to convey, transfer, assign, mortgage or pledge any assets as security for the senior debt securities of one or
more series;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• to evidence the succession of a corporation, limited liability company, partnership or trust to us, and the
assumption by such successor of our covenants, agreements and obligations under the senior indenture or to otherwise comply with the covenant relating to mergers, consolidations and sales of assets;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• to comply with the requirements of the SEC in order to effect or maintain the qualification of the senior
indenture under the Trust Indenture Act of 1939, as amended (the "Trust Indenture Act");

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• to add to our covenants such new covenants, restrictions, conditions or provisions for the protection of the
holders, and to make the occurrence, or the occurrence and continuance, of a default in any such additional covenants, restrictions, conditions or provisions an event of default;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• to cure any ambiguity, defect or inconsistency in the senior indenture or in any supplemental indenture or to
conform the senior indenture or the senior debt securities to the description of senior debt securities of such series set forth in this prospectus or any applicable prospectus supplement;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• to provide for or add guarantors with respect to the senior debt securities of any series;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• to establish the form or forms or terms of the senior debt securities as permitted by the senior indenture;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• to evidence and provide for the acceptance of appointment under the senior indenture by a successor trustee, or
to make such changes as shall be necessary to provide for or facilitate the administration of the trusts in the senior indenture by more than one trustee;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• to add to, change or eliminate any of the provisions of the senior indenture in respect of one or more series of
senior debt securities, provided that any such addition, change or elimination shall (a) neither (1) apply to any senior debt security of any series created prior to the execution of such supplemental indenture and entitled to the benefit
of such provision nor (2) modify the rights of the holder of any such senior debt security with respect to such provision or (b) become effective only when there is no senior debt security described in clause (a)(1) outstanding;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• to make any change to the senior debt securities of any series so long as no senior debt securities of such
series are outstanding; or

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• to make any change that does not adversely affect the rights of any holder in any material respect.

Other amendments and modifications of the senior indenture or the senior debt securities issued may be made, and our compliance with any provision of the senior indenture with respect to any series of senior debt securities may be waived, with the consent of the holders of a majority of the aggregate principal amount of the outstanding senior debt securities of each series affected by the amendment or modification (voting as separate series); provided, however, that each affected holder must consent to any modification, amendment or waiver that:

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• extends the final maturity of any senior debt securities of such series;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• reduces the principal amount of any senior debt securities of such series;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• reduces the rate, or extends the time for payment of, interest on any senior debt securities of such series;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• reduces the amount payable upon the redemption of any senior debt securities of such series;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• changes the currency of payment of principal of or interest on any senior debt securities of such series;

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&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• reduces the principal amount of original issue discount securities payable upon acceleration of maturity or the
amount provable in bankruptcy;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• waives a continuing default in the payment of principal of or interest on the senior debt securities (other than
any such default in payment resulting solely from an acceleration of the senior debt securities);

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• changes the provisions relating to the waiver of past defaults or impairs the right of holders to receive payment
or to institute suit for the enforcement of any payment or conversion of any senior debt securities of such series on or after the due date therefor;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• modifies any of the provisions of these restrictions on amendments and modifications, except to increase any
required percentage or to provide that certain other provisions cannot be modified or waived without the consent of the holder of each senior debt security of such series affected by the modification;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• adversely affects the right to convert or exchange senior debt securities into common stock, other securities or
property in accordance with the terms of the senior debt securities; or

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• reduces the above-stated percentage of outstanding senior debt securities of such series whose holders must
consent to a supplemental indenture or modifies or amends or waives certain provisions of or defaults under the senior indenture.

It shall not be necessary for the holders to approve the particular form of any proposed amendment, supplement or waiver, but it shall be sufficient if the holders' consent approves the substance thereof. After an amendment, supplement or waiver of the senior indenture in accordance with the provisions described in this section becomes effective, the trustee must give to the holders affected thereby certain notice briefly describing the amendment, supplement or waiver. Any failure by the trustee to give such notice, or any defect therein, shall not, however, in any way impair or affect the validity of any such amendment, supplemental indenture or waiver.

*Notice of Redemption.* Notice of any redemption of senior debt securities will be mailed at least 10 days but not more than 60 days before the redemption date to each holder of senior debt securities of a series to be redeemed. Any notice may, at our discretion, be subject to the satisfaction or waiver of one or more conditions precedent. In that case, such notice shall state the nature of such condition precedent. If we elect to redeem a portion but not all of such senior debt securities, the trustee will select the senior debt securities to be redeemed in a manner that complies with applicable legal and stock exchange requirements, if any. Interest on such debt securities or portions of senior debt securities will cease to accrue on and after the date fixed for redemption, unless we default in the payment of such redemption price and accrued interest with respect to any such senior debt security or portion thereof.

If any date of redemption of any senior debt security is not a business day, then payment of principal and interest may be made on the next succeeding business day with the same force and effect as if made on the nominal date of redemption and no interest will accrue for the period after such nominal date.

*Conversion Rights.* We will describe the terms upon which senior debt securities may be convertible into our common stock or other securities in a prospectus supplement. These terms will include the type of securities the senior debt securities are convertible into, the conversion price or manner of calculation thereof, the conversion period, provisions as to whether conversion will be at our option or the option of the holders, the events requiring an adjustment of the conversion price and provisions affecting conversion in the event of the redemption of the senior debt securities and any restrictions on conversion. They may also include provisions adjusting the number of shares of our common stock or other securities issuable upon conversion.

*No Personal Liability of Incorporators, Stockholders, Officers, or Directors.* The senior indenture provides that no recourse shall be had under any obligation, covenant or agreement of ours in the senior indenture or any

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supplemental indenture, or in any of the senior debt securities or because of the creation of any indebtedness represented thereby, against any of our incorporators, stockholders, officers or directors, past, present or future, or of any predecessor or successor entity thereof under any law, statute or constitutional provision or by the enforcement of any assessment or by any legal or equitable proceeding or otherwise. Each holder, by accepting the senior debt securities, waives and releases all such liability.

*Concerning the Trustee.* The senior indenture provides that, except during the continuance of an event of default, the trustee will not be liable except for the performance of such duties as are specifically set forth in the senior indenture. If an event of default has occurred and is continuing, the trustee will exercise such rights and powers vested in it under the senior indenture and will use the same degree of care and skill in its exercise as a prudent person would exercise under the circumstances in the conduct of such person's own affairs.

The senior indenture and the provisions of the Trust Indenture Act incorporated by reference therein contain limitations on the rights of the trustee thereunder, should it become a creditor of ours or any of our subsidiaries, to obtain payment of claims in certain cases or to realize on certain property received by it in respect of any such claims, as security or otherwise. The trustee is permitted to engage in other transactions, provided that if it acquires any conflicting interest (as defined in the Trust Indenture Act), it must eliminate such conflict or resign.

We may have normal banking relationships with the senior trustee in the ordinary course of business.

*Unclaimed Funds.* All funds deposited with the trustee or any paying agent for the payment of principal, premium, interest or additional amounts in respect of the senior debt securities that remain unclaimed for two years after the date upon which such amounts became due and payable will be repaid to us. Thereafter, any right of any holder of senior debt securities to such funds shall be enforceable only against us, and the trustee and paying agents will have no liability therefor.

*Governing Law.* The senior indenture and the senior debt securities will be governed by, and construed in accordance with, the internal laws of the State of New York.

**Certain Terms of the Subordinated Debt Securities**

Other than the terms of the subordinated indenture and subordinated debt securities relating to subordination or otherwise as described in the prospectus supplement relating to a particular series of subordinated debt securities, the terms of the subordinated indenture and subordinated debt securities are identical in all material respects to the terms of the senior indenture and senior debt securities.

Additional or different subordination terms may be specified in the prospectus supplement applicable to a particular series.

*Subordination.* The indebtedness evidenced by the subordinated debt securities is subordinate to the prior payment in full of all of our senior indebtedness, as defined in the subordinated indenture. During the continuance beyond any applicable grace period of any default in the payment of principal, premium, interest or any other payment due on any of our senior indebtedness, we may not make any payment of principal of or interest on the subordinated debt securities (except for certain sinking fund payments). In addition, upon any payment or distribution of our assets upon any dissolution, winding-up, liquidation or reorganization, the payment of the principal of and interest on the subordinated debt securities will be subordinated to the extent provided in the subordinated indenture in right of payment to the prior payment in full of all our senior indebtedness. Because of this subordination, if we dissolve or otherwise liquidate, holders of our subordinated debt securities may receive less, ratably, than holders of our senior indebtedness. The subordination provisions do not prevent the occurrence of an event of default under the subordinated indenture.

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The term "senior indebtedness" of a person means with respect to such person the principal of, premium, if any, interest on, and any other payment due pursuant to any of the following, whether outstanding on the date of the subordinated indenture or incurred by that person in the future:

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• all of the indebtedness of that person for money borrowed;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• all of the indebtedness of that person evidenced by notes, debentures, bonds or other securities sold by that
person for money;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• all of the lease obligations that are capitalized on the books of that person in accordance with generally
accepted accounting principles;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• all indebtedness of others of the kinds described in the first two bullet points above and all lease obligations
of others of the kind described in the third bullet point above that the person, in any manner, assumes or guarantees or that the person in effect guarantees through an agreement to purchase, whether that agreement is contingent or otherwise; and

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• all renewals, extensions or refundings of indebtedness of the kinds described in the first, second or fourth
bullet point above and all renewals or extensions of leases of the kinds described in the third or fourth bullet point above;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• unless, in the case of any particular indebtedness, renewal, extension or refunding, the instrument creating or
evidencing it or the assumption or guarantee relating to it expressly provides that such indebtedness, renewal, extension or refunding is not superior in right of payment to the subordinated debt securities. Our senior debt securities constitute
senior indebtedness for purposes of the subordinated indenture.

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**DESCRIPTION OF WARRANTS**

**General** 

We may issue warrants to purchase common stock, preferred stock or debt securities. We may offer warrants separately or together with one or more additional warrants, common stock, preferred stock or debt securities, or any combination of those securities in the form of units, as described in the applicable prospectus supplement. If we issue warrants as part of a unit, the accompanying prospectus supplement will specify whether those warrants may be separated from the other securities in the unit prior to the expiration date of the warrants. The applicable prospectus supplement will also describe the following terms of any warrants:

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• the specific designation and aggregate number of, and the offering price at which we will issue, the warrants;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• the currency or currency units in which the offering price, if any, and the exercise price are payable;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• the date on which the right to exercise the warrants will begin and the date on which that right will expire or,
if you may not continuously exercise the warrants throughout that period, the specific date or dates on which you may exercise the warrants;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• whether the warrants are to be sold separately or with other securities as parts of units;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• whether the warrants will be issued in definitive or global form or in any combination of these forms, although,
in any case, the form of a warrant included in a unit will correspond to the form of the unit and of any security included in that unit;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• any applicable material U.S. federal income tax consequences;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• the identity of the warrant agent for the warrants and of any other depositaries, execution or paying agents,
transfer agents, registrars or other agents;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• the proposed listing, if any, of the warrants or any securities purchasable upon exercise of the warrants on any
securities exchange;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• the designation and terms of any equity securities purchasable upon exercise of the warrants;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• the designation, aggregate principal amount, currency and terms of any debt securities that may be purchased upon
exercise of the warrants;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• if applicable, the designation and terms of the preferred stock with which the warrants are issued and the number
of warrants issued with each security;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• if applicable, the date from and after which any warrants issued as part of a unit and the related debt
securities, preferred stock, or common stock will be separately transferable;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• the number of shares of common stock, preferred stock purchasable upon exercise of a warrant and the price at
which those shares may be purchased;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• if applicable, the minimum or maximum amount of the warrants that may be exercised at any one time;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• information with respect to book-entry procedures, if any;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• the anti-dilution provisions of, and other provisions for changes to or adjustment in the exercise price of, the
warrants, if any;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• any redemption or call provisions; and

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• any additional terms of the warrants, including terms, procedures and limitations relating to the exchange or
exercise of the warrants.

**Prefunded Warrants** 

We may also issue prefunded warrants to purchase common stock. A prefunded warrant is a type of warrant that allows the holder to purchase a specified number of shares of common stock at a nominal exercise price,

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generally equal to the par value of the underlying common stock. The prefunded warrants may be issued as individual warrant agreements to the holders. In addition to the terms described in the bullets above, the applicable prospectus supplement will describe the following terms of any prefunded warrants:

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• the date on which the right to exercise the pre-funded warrants will
begin, generally on the date of issuance, and the date on which that right will expire, generally when the prefunded warrant is exercised in full;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• whether the warrant may only be exercised pursuant to a cashless exercise procedure;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• certain beneficial ownership limitations, such that a holder will not be entitled to exercise any portion of any
prefunded warrant that, upon giving effect to (or immediately prior to) such exercise, would cause the holder's beneficial ownership to exceed a specified threshold, typically 4.99% or 9.99%, of the number of shares of our outstanding common
stock or the combined voting power of all of our securities, which threshold may be subject to increase or decrease at the option of the holder, subject to a maximum ownership threshold, typically 9.99% or 19.99%, and compliance with a notice
period;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• in the event of a fundamental transaction (generally including any reorganization, recapitalization or
reclassification of our common stock, the sale, transfer or other disposition of all or substantially all of our assets, our consolidation or merger with or into another person in which we are not the surviving entity, the acquisition of more than
50% of our outstanding shares, or any person or group becoming the beneficial owner of more than 50% of the voting power of our outstanding shares), the right of the holder to receive, upon exercise of the prefunded warrants, the same kind and
amount of securities, cash or other property that such holder would have received had they exercised the prefunded warrants immediately prior to such fundamental transaction, without regard to any limitations on exercise contained in the prefunded
warrants; and

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• any additional terms of the warrants, including terms, procedures and limitations relating to the exchange or
exercise of the prefunded warrants.

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**DESCRIPTION OF UNITS**

We may issue units consisting of one or more of the other securities described in this prospectus in any combination, as described in the applicable prospectus supplement. We may issue units in one or more series, which will be described in the applicable prospectus supplement. The applicable prospectus supplement will also describe the following terms of any units:

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• the designation and the terms of the units and of the securities constituting the units, including
whether and under what circumstances the securities comprising the units may be traded separately;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• the identity of any unit agent for the units, if applicable, and of any other depositaries, execution or
paying agents, transfer agents, registrars or other agents;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• any additional terms of the governing unit agreement, if applicable;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• any additional provisions for the issuance, payment, settlement, transfer or exchange of the units or of the
debt securities, common stock, preferred stock or warrants constituting the unit; and

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• any applicable material U.S. federal income tax consequences.

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**FORMS OF SECURITIES**

Each debt security, unit and warrant will be represented either by a certificate issued in definitive form to a particular investor or by one or more global securities representing the entire issuance of securities. Unless the applicable prospectus supplement provides otherwise, certificated securities will be issued in definitive form and global securities will be issued in registered form. Definitive securities name you or your nominee as the owner of the security, and in order to transfer or exchange these securities or to receive payments other than interest or other interim payments, you or your nominee must physically deliver the securities to the trustee, registrar, paying agent or other agent, as applicable. Global securities name a depositary or its nominee as the owner of the debt securities, units or warrants represented by these global securities. The depositary maintains a computerized system that will reflect each investor's beneficial ownership of the securities through an account maintained by the investor with its broker/dealer, bank, trust company or other representative, as we explain more fully below.

**Global Securities**

We may issue the debt securities of a particular series, units and warrants in the form of one or more fully registered global securities that will be deposited with a depositary or its nominee identified in the applicable prospectus supplement and registered in the name of that depositary or nominee. In those cases, one or more global securities will be issued in a denomination or aggregate denominations equal to the portion of the aggregate principal or face amount of the securities to be represented by global securities. Unless and until it is exchanged in whole for securities in definitive registered form, a global security may not be transferred except as a whole by and among the depositary for the global security, the nominees of the depositary or any successors of the depositary or those nominees.

If not described below, any specific terms of the depositary arrangement with respect to any securities to be represented by a global security will be described in the prospectus supplement relating to those securities. We anticipate that the following provisions will apply to all depositary arrangements.

Ownership of beneficial interests in a global security will be limited to persons, called participants, that have accounts with the depositary or persons that may hold interests through participants. Upon the issuance of a global security, the depositary will credit, on its book-entry registration and transfer system, the participants' accounts with the respective principal or face amounts of the securities beneficially owned by the participants. Any dealers, underwriters or agents participating in the distribution of the securities will designate the accounts to be credited. Ownership of beneficial interests in a global security will be shown on, and the transfer of ownership interests will be effected only through, records maintained by the depositary, with respect to interests of participants, and on the records of participants, with respect to interests of persons holding through participants. The laws of some states may require that some purchasers of securities take physical delivery of these securities in definitive form. These laws may impair your ability to own, transfer or pledge beneficial interests in global securities.

So long as the depositary, or its nominee, is the registered owner of a global security, that depositary or its nominee, as the case may be, will be considered the sole owner or holder of the securities represented by the global security for all purposes under the applicable indenture, warrant agreement or unit agreement. Except as described below, owners of beneficial interests in a global security will not be entitled to have the securities represented by the global security registered in their names, will not receive or be entitled to receive physical delivery of the securities in definitive form and will not be considered the owners or holders of the securities under the applicable indenture, warrant agreement or unit agreement. Accordingly, each person owning a beneficial interest in a global security must rely on the procedures of the depositary for that global security and, if that person is not a participant, on the procedures of the participant through which the person owns its interest, to exercise any rights of a holder under the applicable indenture, warrant agreement or unit agreement. We understand that under existing industry practices, if we request any action of holders or if an owner of a beneficial interest in a global security desires to give or take any action that a holder is entitled to give or take

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under the applicable indenture, warrant agreement or unit agreement, the depositary for the global security would authorize the participants holding the relevant beneficial interests to give or take that action, and the participants would authorize beneficial owners owning through them to give or take that action or would otherwise act upon the instructions of beneficial owners holding through them.

Principal, premium, if any, and interest payments on debt securities, and any payments to holders with respect to warrants or units, represented by a global security registered in the name of a depositary or its nominee will be made to the depositary or its nominee, as the case may be, as the registered owner of the global security. None of us, or any trustee, warrant agent, unit agent or other agent of ours, or any agent of any trustee, warrant agent or unit agent will have any responsibility or liability for any aspect of the records relating to payments made on account of beneficial ownership interests in the global security or for maintaining, supervising or reviewing any records relating to those beneficial ownership interests.

We expect that the depositary for any of the securities represented by a global security, upon receipt of any payment to holders of principal, premium, interest or other distribution of underlying securities or other property on that registered global security, will immediately credit participants' accounts in amounts proportionate to their respective beneficial interests in that global security as shown on the records of the depositary. We also expect that payments by participants to owners of beneficial interests in a global security held through participants will be governed by standing customer instructions and customary practices, as is now the case with the securities held for the accounts of customers or registered in "street name," and will be the responsibility of those participants.

If the depositary for any of the securities represented by a global security is at any time unwilling or unable to continue as depositary or ceases to be a clearing agency registered under the Exchange Act, and a successor depositary registered as a clearing agency under the Exchange Act is not appointed by us within 90 days, we will issue securities in definitive form in exchange for the global security that had been held by the depositary. Any securities issued in definitive form in exchange for a global security will be registered in the name or names that the depositary gives to the relevant trustee, warrant agent, unit agent or other relevant agent of ours or theirs. It is expected that the depositary's instructions will be based upon directions received by the depositary from participants with respect to ownership of beneficial interests in the global security that had been held by the depositary.

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**PLAN OF DISTRIBUTION**

We may sell securities:

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• through underwriters;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• through dealers;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• through agents;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• directly to purchasers; or

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• through a combination of any of these methods of sale.

In addition, we may issue the securities as a dividend or distribution or in a subscription rights offering to our existing security holders. This prospectus may be used in connection with any offering of our securities through any of these methods or other methods described in the applicable prospectus supplement.

We may directly solicit offers to purchase securities, or agents may be designated to solicit such offers. We will, in the prospectus supplement relating to such offering, name any agent that could be viewed as an underwriter under the Securities Act, and describe any commissions that we must pay. Any such agent will be acting on a best efforts basis for the period of its appointment or, if indicated in the applicable prospectus supplement, on a firm commitment basis.

The distribution of the securities may be effected from time to time in one or more transactions:

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• at a fixed price, or prices, which may be changed from time to time;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• at market prices prevailing at the time of sale;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• at prices related to such prevailing market prices; or

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• at negotiated prices.

Each prospectus supplement will describe the method of distribution of the securities and any applicable restrictions.

The prospectus supplement with respect to the securities of a particular series will describe the terms of the offering of the securities, including the following:

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• the name of the agent or any underwriters;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• the public offering or purchase price and the proceeds we will receive from the sale of the securities;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• any discounts and commissions to be allowed or re-allowed or paid to the
agent or underwriters;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• all other items constituting underwriting compensation;

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• any discounts and commissions to be allowed or re-allowed or paid to
dealers; and

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• any exchanges on which the securities will be listed.

If any underwriters or agents are utilized in the sale of the securities in respect of which this prospectus is delivered, we will enter into an underwriting agreement or other agreement with them at the time of sale to them, and we will set forth in the prospectus supplement relating to such offering the names of the underwriters or agents and the terms of the related agreement with them.

If a dealer is utilized in the sale of the securities in respect of which this prospectus is delivered, we will sell such securities to the dealer, as principal. The dealer may then resell such securities to the public at varying prices to be determined by such dealer at the time of resale.

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If we offer securities in a subscription rights offering to our existing security holders, we may enter into a standby underwriting agreement with dealers, acting as standby underwriters. We may pay the standby underwriters a commitment fee for the securities they commit to purchase on a standby basis. If we do not enter into a standby underwriting arrangement, we may retain a dealer-manager to manage a subscription rights offering for us.

Remarketing firms, agents, underwriters, dealers and other persons may be entitled under agreements that they may enter into with us to indemnification by us against certain civil liabilities, including liabilities under the Securities Act, and may be customers of, engage in transactions with or perform services for us in the ordinary course of business.

If so indicated in the applicable prospectus supplement, we will authorize underwriters or other persons acting as our agents to solicit offers by certain institutions to purchase securities from us pursuant to delayed delivery contracts providing for payment and delivery on the date stated in the prospectus supplement. Each contract will be for an amount not less than, and the aggregate amount of securities sold pursuant to such contracts shall not be less nor more than, the respective amounts stated in the prospectus supplement. Institutions with whom the contracts, when authorized, may be made include commercial and savings banks, insurance companies, pension funds, investment companies, educational and charitable institutions and other institutions, but shall in all cases be subject to our approval. Delayed delivery contracts will not be subject to any conditions except that:

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• the purchase by an institution of the securities covered under that contract shall not at the time of delivery be
prohibited under the laws of the jurisdiction to which that institution is subject; and

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;• if the securities are also being sold to underwriters acting as principals for their own account, the
underwriters shall have purchased such securities not sold for delayed delivery. The underwriters and other persons acting as our agents will not have any responsibility in respect of the validity or performance of delayed delivery contracts.

Certain agents, underwriters and dealers, and their associates and affiliates may be customers of, have borrowing relationships with, engage in other transactions with, and/or perform services, including investment banking services, for us or one or more of our respective affiliates in the ordinary course of business.

In order to facilitate the offering of the securities, any underwriters may engage in transactions that stabilize, maintain or otherwise affect the price of the securities or any other securities the prices of which may be used to determine payments on such securities. Specifically, any underwriters may overallot in connection with the offering, creating a short position for their own accounts. In addition, to cover overallotments or to stabilize the price of the securities or of any such other securities, the underwriters may bid for, and purchase, the securities or any such other securities in the open market. Finally, in any offering of the securities through a syndicate of underwriters, the underwriting syndicate may reclaim selling concessions allowed to an underwriter or a dealer for distributing the securities in the offering if the syndicate repurchases previously distributed securities in transactions to cover syndicate short positions, in stabilization transactions or otherwise. Any of these activities may stabilize or maintain the market price of the securities above independent market levels. Any such underwriters are not required to engage in these activities and may end any of these activities at any time.

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Under Rule 15c6-1 of the Exchange Act, trades in the secondary market generally are required to settle in one business day, unless the parties to any such trade expressly agree otherwise. The applicable prospectus supplement may provide that the original issue date for your securities may be more than one scheduled business day after the trade date for your securities. Accordingly, in such a case, if you wish to trade securities on any date prior to the first business day before the original issue date for your securities, you will be required, by virtue of the fact that your securities initially are expected to settle in more than one scheduled business day after the trade date for your securities, to make alternative settlement arrangements to prevent a failed settlement.

The securities may be new issues of securities and may have no established trading market. The securities may or may not be listed on a national securities exchange. We can make no assurance as to the liquidity of or the existence of trading markets for any of the securities.

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**LEGAL MATTERS**

Unless the applicable prospectus supplement indicates otherwise, the validity of the securities in respect of which this prospectus is being delivered will be passed upon by Wilmer Cutler Pickering Hale and Dorr LLP.

**EXPERTS**

The consolidated financial statements of Xilio Therapeutics, Inc. appearing in Xilio Therapeutics, Inc.'s Annual Report (Form 10-K) for the year ended December 31, 2024 have been audited by Ernst & Young LLP, independent registered public accounting firm, as set forth in their report thereon (which contains an explanatory paragraph describing conditions that raise substantial doubt about the Company's ability to continue as a going concern as described in Note 1 to the consolidated financial statements) included therein, and incorporated herein by reference. Such financial statements are, and audited financial statements to be included in subsequently filed documents will be, incorporated herein in reliance upon the report of Ernst & Young LLP pertaining to such financial statements (to the extent covered by consents filed with the Securities and Exchange Commission) given on the authority of such firm as experts in accounting and auditing.

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![LOGO](g74783g36a36.jpg)

**Pre-Funded Warrants to Purchase 74,780,300 Shares of Common Stock** 

**Prospectus Supplement** 

**Leerink Partners** 

**February 11, 2026**