Onconetix, Inc.

This prospectus contains “forward-looking statements” within the meaning of the federal securities laws, and that involve significant risks and uncertainties. Words such as “may,” “should,” “could,” “would,” “predicts,” “potential,” “continue,” “expects,” “anticipates,” “future,” “intends,” “plans,” “believes,” “estimates,” and similar expressions, as well as statements in future tense, identify forward-looking statements. Forward-looking statements should not be read as a guarantee of future performance or results and may not be accurate indications of when such performance or results will be achieved. Forward-looking statements are based on information we have when those statements are made or management’s good faith belief as of that time with respect to future events and are subject to significant risks and uncertainties that could cause actual performance or results to differ materially from those expressed in or suggested by the forward-looking statements. Forward-looking statements are subject to a number of risks, uncertainties and assumptions in 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.

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PROSPECTUS SUMMARY

The SEC allows us to “incorporate by reference” certain information that we file with the SEC, which means that we can disclose important information to you by referring you to those documents. The information incorporated by reference is considered to be part of this prospectus, and information that we file later with the SEC will update automatically, supplement and/or supersede the information disclosed in this prospectus. Any statement contained in a document incorporated or deemed to be incorporated by reference in this prospectus shall be deemed to be modified or superseded for purposes of this prospectus to the extent that a statement contained in this prospectus or in any other document that also is or is deemed to be incorporated by reference in this prospectus modifies or supersedes such statement. Any such statement so modified or superseded shall not be deemed, except as so modified or superseded, to constitute a part of this prospectus. You should read the following summary together with the more detailed information regarding our company, our Common Stock and our financial statements and notes to those statements included in this prospectus.

Our Company

We are a commercial stage biotechnology company focused on the research, development, and commercialization of innovative solutions for oncology. Through our acquisition of Proteomedix, which closed on December 15, 2023, we own Proclarix, an in vitro diagnostic test for prostate cancer originally developed by Proteomedix and approved for sale in the European Union under the In Vitro Diagnostic Regulation (“IVDR”), which we anticipate will be marketed in the U.S. as a lab developed test through our license agreement with LabCorp.

Since our inception in October 2018 until April 2023, when we acquired ENTADFI, we devoted substantially all of our resources to performing research and development, undertaking preclinical studies and enabling manufacturing activities in support of our product development efforts, hiring personnel, acquiring and developing our technology and now halted vaccine candidates, organizing and staffing our company, performing business planning, establishing our intellectual property portfolio and raising capital to support and expand such activities.

ENTADFI is an FDA-approved, once daily pill that combines finasteride and tadalafil for the treatment of BPH, a disorder of the prostate. However, in light of (i) the time and resources needed to continue pursuing commercialization of ENTADFI, and (ii) the Company’s cash runway and indebtedness, the Company abandoned commercialization of ENTADFI and no longer holds remaining inventory of the product as of December 31, 2025. In addition, as part of cost reduction efforts and in connection with our initial pause in commercializing ENTADFI, we terminated three employees involved with the ENTADFI program, effective April 30, 2024, with such individuals to continue assisting the Company on an as-needed, consulting basis. Based on the circumstances surrounding ENTADFI, at June 30, 2024, the ENTADFI assets were fully impaired. Refer to Note 4 in the consolidated financial statements for the period ended December 31, 2024 for further discussion.

Proclarix is an easy-to-use next generation protein-based blood test that can be done with the same sample as a patient’s regular Prostate-Specific Antigen (“PSA”) test. The PSA test is a well-established prostate specific marker that measures the concentration of PSA molecules in a blood sample. A high level of PSA can be a sign of prostate cancer. However, PSA levels can also be elevated for many other reasons including infections, prostate stimulation, vigorous exercise or even certain medications. PSA results can be confusing for many patients and even physicians. It is estimated over 50% of biopsies with elevated PSA are negative or clinically insignificant resulting in an overdiagnosis and overtreatment that impacts the physician’s routine, our healthcare system, and the quality of patients’ lives. Approximately 10% of all men have elevated PSA levels., commonly referred to as the diagnostic “grey zone”, of which only 20 - 40% present clinically with cancer. Proclarix is intended for use in diagnosing these patients where it is difficult to decide if a biopsy is necessary to verify a potential clinically significant cancer diagnosis. Proclarix helps doctors and patients with unclear PSA test results through the use of our proprietary Proclarix Risk Score which delivers clear and immediate diagnostic support for further treatment decisions. No additional intervention is required, and results are available quickly. Local diagnostic laboratories can integrate this multiparametric test into their current workflow because Proclarix assays use the enzyme-linked immunosorbent assay (ELISA) standard, which most diagnostic laboratories are already equipped to process.

There were two new peer-reviewed scientific publications published in the first quarter of 2026 on the clinical utility of Proclarix. The first paper, by Schiess et al., has been accepted for publication in BMC Cancer, an open-access oncology research journal. The study evaluated Proclarix in a cohort of 371 men and ruled out clinically insignificant or absent prostate cancer while maintaining a low risk of missing csPCa. Proclarix was subsequently shown to significantly reduce overdiagnosis and unnecessary biopsies, outperforming both %fPSA and the ERSPC risk calculator. The second paper, by Athanasiou et al., has been published in the journal Cancers (2026, 18, 1348-62). In a cohort of 132 men under active surveillance, the study demonstrated the prognostic value of Proclarix® and its risk score in predicting the transition of patients from active surveillance to active treatment.

Proclarix is CE-marked and for sale in Europe. In the United Kingdom, as of March 31, 2026, Proclarix is now offered by a patient organization as an additional option within a screening initiative for early identification of prostate cancer and approximately 100 Proclarix tests were carried out within this initiative as of March 31, 2026.

We continue our sales efforts and expect growing revenues from sales of Proclarix in 2026 and beyond. We anticipate these sales to offset some expenses relating to commercial scale up and development, we expect our expenses also to increase in connection with our ongoing activities, as we:

As of March 31, 2026, Proteomedix has initiated a PRIME study, a multi-center clinical validation study conducted in collaboration with Labcorp to evaluate Proclarix in the U.S. market and across various ethnicities. The first participants have been enrolled and the study is designed to ultimately include up to 500 men.

We rely and will continue to rely on third parties for the manufacturing of Proclarix. We have no internal manufacturing capabilities, and we will continue to rely on third parties, of which the main suppliers are single-source suppliers, for commercial product.

We do not have any products approved for sale, aside from Proclarix. We have abandoned commercialization of ENTADFI and have destroyed our inventory of the product.

To date, we have financed our operations primarily with proceeds from our sale of preferred securities to seed investors, the initial public offering (“IPO”), and subsequent offerings of debt and equity securities. We will continue to require significant additional capital to commercialize Proclarix, and to fund operations for the foreseeable future. Accordingly, until such time as we can generate significant revenue, if ever, we expect to finance our cash needs through public or private equity or debt financings, third-party (including government) funding and to rely on third-party resources for marketing and distribution arrangements, as well as other collaborations, strategic alliances and licensing arrangements, or any combination of these approaches, to support our operations.

We have incurred net losses since inception and expect to continue to incur net losses in the foreseeable future. Our net losses may fluctuate significantly from quarter-to-quarter and year-to-year, depending in large part on the timing of our preclinical studies, clinical trials and manufacturing activities, our expenditures on other research and development activities and commercialization activities. As of March 31, 2026, we had cash of approximately $3.7 million, working capital of approximately $1.3 million and an accumulated deficit of approximately $135.4 million. During the quarter ended March 31, 2026, we used approximately $2.1 million in cash for operating activities. In addition, as of June 5, 2026, our cash balance was approximately $6.5 million. We believe that our current cash balance is not sufficient to fund its operations for one year from the date of issuance of the consolidated financial statements for the year. While such capital raises may enable us to sustain current operations and meet existing obligations, we continue to generate recurring net operating losses and have not yet established sustained positive cash flows to support our strategic growth initiatives. Such initiatives include the commercialization of Proclarix and our development and commercialization of future product candidates. These factors raise substantial doubt on our ability to continue as a going concern for one year from the date of issuance of our consolidated financial statements for the financial year ended December 31, 2025 and March 31, 2026.

Until we generate revenue sufficient to support self-sustaining cash flows, if ever, we will need to raise additional capital to fund our continued operations, including our product development and commercialization activities related to our current and future products. There can be no assurance that additional capital will be available to us on acceptable terms, or at all, or that we will ever generate revenue sufficient to provide self-sustaining cash flows. These circumstances raise substantial doubt about our ability to continue as a going concern. The consolidated financial statements of Onconetix, incorporated by reference, as of and for the year ended December 31, 2025 and the period ended March 31, 2026, in this prospectus do not include any adjustment that might be necessary if the Company is unable to continue as a going concern.

Because of the numerous risks and uncertainties associated with our business, we are unable to predict the timing or amount of increased expenses or when or if we will be able to achieve or maintain profitability. Additionally, even if we are able to generate revenue from Proclarix, we may not become profitable. If we fail to become profitable or are unable to sustain profitability on a continuing basis, then we may be unable to continue our operations at planned levels and may be forced to reduce our operations.

Recent Developments

May 2026 Reverse Stock Split

On May 21, 2026, the Company effected a reverse stock split of all shares of its issued and outstanding Common Stock at a ratio of one-for-ten (1:10). The Company accounted for the reverse stock split on a retrospective basis pursuant to Accounting Standards Codification (“ASC”) 260,Earnings Per Share. All issued and outstanding common stock, common stock warrants, and share-based awards’ exercise prices and per share data have been adjusted in these condensed consolidated financial statements, on a retrospective basis, to reflect the reverse stock split for all periods presented. The number of authorized shares and par value of the preferred stock and common stock were not adjusted because of the reverse stock split.

Resignation of Andrew Oakley and Thomas Meier as Directors; Elections of Sammy Dorf as Chairman of the Board

Effective on April 20, 2026, Andrew Oakley and Thomas Meier notified the Board of their resignation from the Board. As a result of their resignation from the Board and effective as of the date mentioned herein, Mr. Oakley has also resigned from his position as Chairman of the Board and his service on the Audit Committee, Compensation Committee and the Nominating and Corporate Governance Committee, and Mr. Meier has also resigned from his service on the Compensation Committee.

Effective on April 23, 2026, the Board has appointed Sammy Dorf, an existing member of the Board, as Chairman of the Board. In connection with Mr. Dorf’s election as Chairman, the Compensation Committee of the Board has agreed to compensate Mr. Dorf $20,000 per year, payable on a quarterly basis, commencing on the date of his election.

Election of Josh Epstein

Effective as of April 23, 2026, the Board elected Josh Epstein to serve as a member of the Board and a member of the Audit Committee, Compensation Committee and as the chair of the Nominating and Corporate Governance Committee. Mr. Epstein, a Class II director, will serve for a term expiring at the Company’s 2026 annual meeting of stockholders.

For his service on the Board, Mr. Epstein will receive compensation consistent with that of other non-employee directors.

March 2026 Reverse Stock Split

On March 25, 2026, the Company effected a reverse stock split of all shares of its issued and outstanding Common Stock at a ratio of one-for-five (1:5). The Company accounted for the reverse stock split on a retrospective basis pursuant to Accounting Standards Codification (“ASC”) 260,Earnings Per Share. All issued and outstanding common stock, common stock warrants, and share-based awards’ exercise prices and per share data have been adjusted in these condensed consolidated financial statements, on a retrospective basis, to reflect the reverse stock split for all periods presented. The number of authorized shares and par value of the preferred stock and common stock were not adjusted because of the reverse stock split.

Realbotix Corp. Share Exchange Agreement

On February 11, 2026, we entered into a Share Exchange Agreement (the “Share Exchange Agreement”), by and among (i) Onconetix, (ii) Realbotix Corp., a company existing under the laws of the Province of Ontario (“Parent”), (iii) Simulacra Corporation, a Delaware corporation and a wholly-owned subsidiary of Parent (the “Seller”) and (iv) Realbotix, LLC, a Delaware limited liability company and wholly owned subsidiary of the Seller (the “Realbotix”).

Pursuant to the Share Exchange Agreement, subject to the terms and conditions set forth therein, the Seller agreed to contribute and transfer to us, and we agreed to acquire and accept, all of the issued and outstanding equity interests of Realbotix (the “Realbotix Interests”) in exchange for newly issued shares of Common Stock. (the “Share Exchange” and the other transactions contemplated by the Share Exchange Agreement, the “Realbotix Transactions”).

Unless otherwise defined herein, the capitalized terms used below are defined in the Share Exchange Agreement.

Consideration

In full consideration for the contribution of the Realbotix Interests, we will issue shares of Common Stock to the Seller (the “Exchange Shares”), such that, immediately following the Closing and after giving effect to such issuance, the Seller will own a percentage of our fully diluted shares (the “Fully Diluted Shares”) that will be adjusted based on Net Cash (as defined below) as follows: (i) if Net Cash is greater than or equal to $12.5 million, but less than $15.0 million, Seller will own 90% of the Fully Diluted Shares, (ii) if Net Cash is greater than or equal to $15.0 million, but less than $18.0 million, Seller will own 85% of the Fully Diluted Shares, (iii) if Net Cash is greater than or equal to $18.0 million, but less than $20.0 million, Seller will own 80% of the Fully Diluted Shares and (iv) if Net Cash is greater than or equal to $20.0 million, Seller will own 75% of the Fully Diluted Shares. “Net Cash” means the amount of cash and cash equivalents held by us upon the Closing, whether received by Realbotix or us in connection with the Realbotix Transactions, net of D&O tail insurance costs; change-of-control or other payments owed to our officers and director of as a result of the Realbotix Transactions; all our indebtedness; certain of our liabilities and our transaction expenses.

Conversion of Company Convertible Securities

Prior to the consummation of the Share Exchange, the holders of Realbotix Convertible Securities will exercise their rights to receive Realbotix Interests pursuant to the terms of such Realbotix Convertible Securities (as defined below) at the applicable conversion ratio as set forth in the Realbotix Convertible Securities (the “Realbotix Convertible Securities Conversion”). Upon completion of the Realbotix Convertible Securities Conversion and prior to Closing, all Realbotix Convertible Securities will be canceled or terminated, as applicable, will no longer be outstanding and will cease to exist and no payment or distribution will be made with respect thereto. Each holder of Realbotix Convertible Securities thereafter will cease to have any rights with respect to such securities.

Closing Conditions

The consummation of the Share Exchange is subject to customary closing conditions, including (i) the accuracy of the representations and warranties of the parties (subject to customary materiality qualifiers); (ii) compliance in all material respects by the parties with their respective covenants and agreements under the Share Exchange Agreement; (iii) delivery of customary closing certificates and good standing certificates; (iv) receipt by Board of a fairness opinion; (v) the absence of any law, order or injunction prohibiting the consummation of the Realbotix Transactions and (vi) receipt of any required third-party and regulatory approvals and consents.

The obligation of the Realbotix, Parent and Seller to complete the Closing is subject to the condition that, at Closing, we shall have an aggregate of at least $12.5 million in Net Cash (the “Net Cash Condition”).

Additionally, the obligation of Realbotix, Parent and us to complete the Closing are subject to the conditions that (i) we have entered into an agreement with an investor, reasonably acceptable to us and Realbotix, providing for an equity line of credit pursuant to which such investor would commit to purchase up to an aggregate of $125.0 million of Common Stock and (ii) the conversion of our Preferred Stock into Common Stock and the termination of or certain amendments to of all Onconetix Options and Onconetix Warrants (the “Convertible Securities Condition”).

Termination

In addition to termination by mutual written agreement, for the other party’s uncured breach or if a governmental order permanently prohibits the Closing, the Share Exchange Agreement provides for termination:

Each party will bear its own fees and expenses incurred in connection with the negotiation, execution and performance of the Share Exchange Agreement and the Realbotix Transactions. However, the Share Exchange Agreement provides for the payment of termination fees and reimbursement of transaction expenses in the following termination scenarios:

Representations and Warranties

We, Realbotix, and the Seller have made customary representations and warranties in the Share Exchange Agreement. The representations and warranties of us, Realbotix, and the Seller will not survive the Closing.

Covenants of the Parties

Each party to the Share Exchange Agreement agreed to use its commercially reasonable efforts to consummate the Realbotix Transaction.

The Share Exchange Agreement contains certain covenants by each of the parties, to be observed during the period between the execution of the Share Exchange Agreement and Closing, including covenants regarding: (1) the provision of access to information, properties, books, records and personnel; (2) delivery of audited financial statements of the Company; (3) litigation support; (4) the preparation and filing of a registration statement, SEC reports and related disclosure documents and compliance with Nasdaq listing and reporting requirements; (5) no insider trading; (6) further assurances; (7) public announcements; (8) confidentiality; (9) indemnification of directors and officers and tail insurance; and (10) transfer taxes.

The parties have agreed to take all necessary actions to cause our Board, immediately after closing, to consist of five directors, including: (i) one person who is designated by us and reasonably acceptable to Realbotix and (ii) four persons who are designated by Realbotix and reasonably acceptable to us.

We have also agreed to prepare and file with the Securities and Exchange Commission (“SEC”) a registration statement on Form S-4 in connection with the registration under the Securities Act of 1933, as amended (the “Securities Act”), of the issuance of the Exchange Shares to be issued under the Share Exchange Agreement and containing a proxy statement (a “Proxy Statement”) for the purpose of soliciting proxies from our stockholders for the matters to be acted on at the special meeting of our stockholders. We have also agreed to use reasonable best efforts to maintain its listing on the Nasdaq and to enable the listing on Nasdaq of the Exchange Shares.

During the time between the execution of the Share Exchange Agreement and the Closing, Realbotix agreed to conduct its business in the ordinary course of business in all material respects and to comply with certain covenants regarding the operation of its business, including covenants related to (i) amendments to the Realbotix’s organizational documents; (ii) recapitalization of the Realbotix’s equity interests; (iii) issuance of additional securities; (iv) incurrence of additional indebtedness; (v) material changes to tax elections; (vi) amendments to or termination of material contracts; (vii) maintenance of books and records; (viii) establishment of any subsidiary or entry into a new line of business; (ix) maintenance of insurance policies; (x) revaluation of material assets or material changes in accounting methods, principles or policies, except as required to comply with U.S. GAAP; (xi) waiver, settlement or compromise of material claims, actions or proceedings, subject to specified thresholds; (xii) acquisition of equity interests or assets, or any other form of business combination, outside of the ordinary course of business; (xiii) capital expenditures in excess of specified thresholds; (xiv) adoption of a plan of liquidation, dissolution, merger, consolidation, restructuring, recapitalization or other reorganization; (xv) voluntary incurrence of liabilities or obligations in excess of specified thresholds other than pursuant to contracts in existence as of the date of the Share Exchange Agreement or entered into in the ordinary course of business; (xvi) sale, lease, license or other disposition of any material portion of the Realbotix’s assets, properties or rights; (xvii) entry into any agreement, understanding or arrangement relating to the voting of the Realbotix’s equity interests; (xviii) taking any action that would reasonably be expected to materially delay or impair the obtaining of any required governmental or regulatory consents in connection with the Share Exchange Agreement; or (xix) authorization or agreement to take any of the foregoing actions.

During the same period, we also agreed to conduct its business in the ordinary course of business in all material respects and to comply with certain interim operating covenants, including covenants restricting our ability, without Realbotix’s prior written consent (subject to specified exceptions), to (i) amend its organizational documents; (ii) effect mergers, consolidations, acquisitions, liquidations, restructurings or other business combinations; (iii) issue, repurchase, redeem or otherwise modify its equity securities or declare dividends or other distributions; (iv) incur additional indebtedness or guarantee obligations of third parties; (v) dispose of material assets or subsidiaries; (vi) make material loans, advances or capital contributions; (vii) make material tax elections or changes in accounting methods, principles or practices, except as required by applicable law, GAAP or Regulation S-K; (viii) amend, terminate, waive or assign material contracts other than in the ordinary course of business; (ix) fail to maintain books, records or insurance coverage in the ordinary course of business; (x) establish subsidiaries or enter into new lines of business; (xi) settle material litigation or other proceedings other than within specified thresholds; (xii) make capital expenditures or incur liabilities in excess of specified thresholds; (xiii) enter into arrangements relating to the voting of Common Stock; (xiv) take actions that would reasonably be expected to materially delay or impair the receipt of required governmental or regulatory approvals; or (xv) authorize, commit or publicly propose any of the foregoing actions.

Governing Law

The Share Exchange Agreement is governed by the laws of the State of Delaware.

Series E PIPE Financing

On October 1, 2025, the Company entered into a securities purchase agreement (the “Series E Securities Purchase Agreement”) with institutional investor(s) and sold to such institutional investors(s)(collectively, the “Series E PIPE Investors”), an aggregate of 7,813 shares of Series E convertible preferred stock, par value $0.00001 per share (“Series E Preferred Stock”), which are convertible into common stock of the Company, $0.00001 par value per share and warrants (the “Series E Warrants”) to initially purchase 2,025,223 shares of Common Stock for an aggregate purchase price of $6.25 million, which was also equal to the net cash proceeds. The initial exercise price of the Series E Warrants was $3.8576. As part of anti-dilution contained in the Series E Warrants, upon reverse split, the warrants and exercise price reset based on the lowest closing price during the 16 trading days post the reverse split. The Company effected a reverse split on March 25, 2026, and the current Series E Warrants allow for the purchase of 1,070,498 shares of Common Stock at an exercise price of $7.298 on a post-reverse split basis. The Company effected another reverse split on May 21, 2026. Due to the anti-dilution provisions contained in the Series E Warrants, pursuant to which, upon a stock split, stock dividend, stock combination recapitalization or other similar transaction involving the Common Stock (each, a “Stock Combination Event” and such date, the “Stock Combination Event Date”), if the exercise price of the Series E Warrants is higher than lowest volume weighted average price (VWAP) during the fifteen (15) consecutive trading day period ending, and including the trading day immediate preceding the sixteenth (16 th) trading day (such price referred herein as the “Event Market Price”) after such Stock Combination Event Date, then the exercise price of the Series E Warrants then in effect shall be adjusted to the Event Market Price on such sixteenth (16 th) trading day. As such, the exercise price of the Series E Warrants is expected to reset on June 12, 2026. The Series E Warrants are exercisable beginning on the issuance date and expire on the third anniversary of the issuance date.

Concurrently with entering into the Series E Securities Purchase Agreement, the Company also entered into a registration rights agreement with the Series E PIPE Investors, pursuant to which it has agreed to provide the Series E PIPE Investors with certain registration rights related to the shares of Common Stock underlying the shares of Series E Preferred Stock and Series E Warrants.

Series D PIPE Financing

On September 22, 2025, the Company entered into a securities purchase agreement (the “Series D Securities Purchase Agreement”) with eleven institutional investors, and sold or exchanged debt, to such investors (collectively, the “Series D PIPE Investors”) an aggregate of 16,099 shares of Series D convertible preferred stock, par value $0.00001 per share (“Series D Preferred Stock”), which includes an issuance of 500 shares of Series D Preferred Stock to the lead investor in consideration for the Series D PIPE Investors’ irrevocable commitment to purchase shares of the Series D Preferred Stock, and warrants (the “Series D Warrants”) to initially purchase 4,362,827 shares of Common Stock for an aggregate purchase price of $12.9 million and net cash proceeds of $9.3 million. The initial exercise price of the Series D Warrants was $3.6896. As part of anti-dilution contained in the Series D Warrants, upon reverse split, the warrants and exercise price reset based on the lowest closing price during the 16 trading days post the reverse split. The Company effected a reverse split on March 25, 2026, and the current Series D Warrants allow for the purchase of 2,152,945 shares of Common Stock at an exercise price of $7.298 on a post-reverse split basis. The Company effected another reverse split on May 21, 2026. Due to the anti-dilution provisions contained in the Series D Warrants, pursuant to which, upon a stock split, stock dividend, stock combination recapitalization or other similar transaction involving the Common Stock (each, a “Stock Combination Event” and such date, the “Stock Combination Event Date”), if the exercise price of the Series D Warrants is higher than lowest volume weighted average price (VWAP) during the fifteen (15) consecutive trading day period ending, and including the trading day immediate preceding the sixteenth (16 th) trading day (such price referred herein as the “Event Market Price”) after such Stock Combination Event Date, then the exercise price of the Series D Warrants then in effect shall be adjusted to the Event Market Price on such sixteenth (16 th) trading day. As such, the exercise price of the Series E Warrants is expected to reset on June 12, 2026. The Series D Warrants are exercisable beginning on the issuance date and expire on the third anniversary of the issuance date.

Concurrently with entering into the Series D Securities Purchase Agreement, the Company also entered into a registration rights agreement with the Series D PIPE Investors, pursuant to which it has agreed to provide the Series D PIPE Investors with certain registration rights related to the shares of Common Stock underlying the shares of Series D Preferred Stock and Series D Warrants.

Amendment to Series D and Series E Warrants

On December 23, 2025, the Company entered into Limited Waiver Agreements (the “Warrant Limited Waiver”) with all holders of the Series D and Series E Warrants, effective as of October 1, 2025, pursuant to which such holders agreed to waive certain provisions of their Series D Warrants and Series E Warrants. Specifically, in the event the Company issues securities with a conversion price dependent on the price of the Common Stock (the “Variable Price”), the holders of Series D Warrants and Series E Warrants will no longer have the optional right to convert their applicable Series D Warrants and Series E Warrants at the Variable Price.

Additionally, the Warrant Limited Waiver waived the right of the Series D Warrants and the Series E Warrants to receive a guaranteed cash payment in connection with a “Fundamental Transaction” (as such term is defined in the Series D Warrants and Series E Warrants). Instead, in connection with a “Fundamental Transaction” that is not within the Company’s control, the holders of Series D Warrants and Series E Warrants are entitled only to receive the same form and proportion of consideration (or deemed common stock of the successor entity, if no such consideration is paid) as is offered and paid to holders of Common Stock, the definition of “Fundamental Transaction” in Series D Warrants and the Series E Warrants was further amended by the Warrant Limited Waiver to replace each reference to “at least” 50% with “more than” 50% of the outstanding Common Stock.

Termination of Ocuvex Business Combination Agreement

On July 16, 2025, the Company entered into an Agreement and Plan of Merger with (i) Onconetix Merger Sub, Inc., a Delaware corporation and a direct, wholly owned subsidiary of the Company, and (ii) Ocuvex Therapeutics, Inc., a Delaware corporation (“Ocuvex”, and such agreement, the “Ocuvex Merger Agreement”). Pursuant to the Merger Agreement, Merger Sub will merge with and into Ocuvex, with Ocuvex surviving the merger as a direct, wholly owned subsidiary of the Company (the “Ocuvex Merger” and the other transactions contemplated by the Merger Agreement, the “Ocuvex Transactions”).

Effective September 24, 2025, pursuant to Section 9.01(a) of the Merger Agreement, Ocuvex and the Company entered into a Termination and Release Agreement (the “Termination Agreement”) pursuant to which they agreed to terminate the Ocuvex Merger Agreement and the transactions contemplated thereby. The Termination Agreement also terminates and makes void the ancillary documents entered by and among Ocuvex and the Company in connection with the Ocuvex Merger Agreement. The Termination Agreement also provides for a mutual release of claims among the Parties and their affiliates and in consideration of the foregoing, the Company agreed to pay to Ocuvex, an amount equal to**$**302,343.55 (the “Termination Payment”), which represents all amounts payable by the Company to Ocuvex pursuant to Section 6.02(f) of the Merger Agreement.

As of September 24, 2025, Ocuvex confirmed receipt of the Termination Payment, and as a result the Ocuvex Merger Agreement is of no further force and effect.

Series C PIPE Financing

On October 1, 2024, the Board authorized the Company to create a series of 10,000 shares of preferred stock designated as “Series C convertible Preferred Stock”, with a par value of $0.00001, pursuant to the certificate of designations. At any time after the initial issuance date of Series C convertible Preferred Stock, each Series C Preferred Share shall be convertible into validly issued, fully paid and non-assessable shares of Common Stock. The holders of Series C Preferred Stock are entitled to dividends, on an as-if converted basis, equal to and in the same form as dividends actually paid on shares of Common Stock, when and if actually paid. In addition, from and after the occurrence and during the continuance of any Triggering Event, dividends (“Default Dividends”) will accrue on the Stated Value of each Series C Preferred Share at a rate of fifteen percent (15.0%) (the “Default Rate”) per annum. Each holder is entitled to convert any portion of the outstanding Series C Preferred Shares held by such holder into validly issued, fully paid and non-assessable Conversion shares at the Conversion Rate, which can be determined by dividing (x) the post-reverse split Conversion Amount of such Series C Preferred Share by (y) the post-reverse split Conversion Price, $225.28, subject to adjustment as provided in the Series C Certificate of Designations.

On October 2, 2024, the Company entered into, and sold, to six institutional investors (collectively, the “PIPE Investors”), pursuant to the securities purchase agreement an aggregate of 3,499 shares of Series C Preferred Stock which includes an issuance of 840 shares of Series C Preferred Stock to the lead investor in consideration for the PIPE Investors’ irrevocable commitment to purchase shares of the Series C Preferred Stock, and warrants to purchase 136 shares of Common Stock on a post-reverse split basis for aggregate net cash proceeds to the Company of $1.9 million. The exercise price of the warrants is $18,615.00 on a post-reverse split basis, and the warrants are exercisable six months after the issuance date and expire on the third anniversary of the Initial Exercisability Date.

In no event may any Series C Preferred Shares be converted (or Series C Warrants be exercised) and shares of Common Stock be issued to any holder if after giving effect to the issuance of shares of Common Stock upon such conversion of the Series C Preferred Shares (or exercise of the Series C Warrants), the holder (together with its affiliates, if any) would beneficially own more than 4.99% of the outstanding shares of Common Stock, which we refer to herein as the “Series C PIPE Blocker”. The Series C PIPE Blocker may be raised or lowered to any percentage not in excess of 9.99% at the option of the applicable holder of the Series C Preferred Shares (or Series C Warrants), except that any raise will only be effective upon 61-days’ prior notice to the Company.

On July 16, 2025, the Company exercised its voluntary adjustment right under the Series C to lower the conversion price of the Series C Preferred Stock, until July 31, 2025, to a post-reverse split of $175.00, and holders of 2,130 shares Series C Preferred Stock agreed to convert their shares into shares of Common Stock. As of September 30, 2025, 7 shares of Series C Preferred Stock were outstanding, after the exchange of 203 shares of Series C Preferred Stock into 244 shares of Series D Preferred Stock.

As of March 31, 2026, 7 shares of Series C Preferred Stock were outstanding from the original issuance of 3,499 shares of Series C Preferred Stock to institutional investors, after the i) redemption of 1,369 shares of Series C Preferred Stock for aggregate consideration of $1.71 million, ii) the conversion of 1,920 shares of Series C Preferred Stock into shares of Common Stock, and iii) the exchange of 203 shares of Series C Preferred Stock into 244 shares of Series D Preferred Stock.

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