Onconetix, Inc.

Note 1 — Organization and Basis of Presentation

Organization and Nature of Operations

Onconetix, Inc. (formerly known as Blue Water Biotech, Inc. and Blue Water Vaccines Inc.) (the “Company” or “Onconetix”) was formed on October 26, 2018, and is a commercial stage biotechnology company focused on the research, development, and commercialization of innovative solutions for oncology.

On December 15, 2023, Onconetix acquired 100% of the issued and outstanding voting equity interests in Proteomedix AG, a Swiss company (“Proteomedix” or “PMX”), and its related diagnostic product Proclarix. As a result of this transaction, Proteomedix became a wholly owned subsidiary of Onconetix. Proteomedix is a healthcare company whose mission is to transform prostate cancer diagnosis. Proteomedix has identified novel biomarker signatures with utility in prostate cancer diagnosis, prognosis and therapy management.

In April 2023, the Company acquired ENTADFI, a Food and Drug Administration (“FDA”)-approved, once daily pill that combines finasteride and tadalafil for the treatment of benign prostatic hyperplasia.

Historically, the Company’s focus was on the research and development of transformational vaccines to prevent infectious diseases worldwide, until the third quarter of 2023, at which time the Company halted its efforts on vaccine development activities to focus on commercialization activities for ENTADFI and pursue other potential acquisitions. 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 the ENTADFI assets were fully impaired at June 30, 2024 (see Notes 4 and 5).

On April 21, 2023, the Company filed an amendment to its Amended and Restated Certificate of Incorporation with the Secretary of State of Delaware to change its corporate name from “Blue Water Vaccines Inc.” to “Blue Water Biotech, Inc.” The name change was effective as of April 21, 2023. On December 15, 2023, the Company filed an amendment to its Amended and Restated Certificate of Incorporation with the Secretary of State of Delaware to change its corporate name from “Blue Water Biotech, Inc.” to “Onconetix, Inc.” In connection with each of the name changes, the Company also amended the Company’s bylaws to reflect the new corporate name.

Reverse Stock Split

On June 13, 2025, the Company effected a reverse stock split of all shares of its issued and outstanding Common Stock at a ratio of one-for-eighty-five (1:85). The Company accounted for the reverse stock split on a retrospective basis pursuant to 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 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.

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 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 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.

Note 1 — Organization and Basis of Presentation (cont.)

Basis of Presentation and Principles of Consolidation

The Company’s condensed consolidated financial statements have been prepared in conformity with accounting principles generally accepted in the United States of America (“U.S. GAAP”) and include the accounts of Onconetix and its 100% wholly owned subsidiary, Proteomedix, since the acquisition date of December 15, 2023. All significant intercompany balances and transactions have been eliminated in consolidation.

Unaudited Interim Consolidated Financial Statements

The accompanying condensed consolidated balance sheet as of March 31, 2026, and the condensed consolidated statements of operations and comprehensive loss and the condensed consolidated statements of convertible preferred stock and stockholders’ equity (deficit) for the three months ended March 31, 2026 and 2025, and the condensed consolidated statements of cash flows for the three months ended March 31, 2026 and 2025 are unaudited. These unaudited interim consolidated financial statements have been prepared on the same basis as the audited consolidated financial statements, and in management’s opinion, include all adjustments, consisting of only normal recurring adjustments, necessary for the fair statement of the Company’s financial position as of March 31, 2026 and its results of operations and comprehensive loss for the three months ended March 31, 2026 and 2025, and its cash flows for the three months ended March 31, 2026 and 2025. The financial data and the other financial information disclosed in the notes to these condensed consolidated financial statements related to the three-month periods are also unaudited. Operating results for the three months ended March 31, 2026, are not necessarily indicative of the results that may be expected for the year ended December 31, 2026, any other interim periods, or any future year or period. The unaudited condensed consolidated financial statements included in this Report should be read in conjunction with the audited consolidated financial statements and notes thereto included in the Company’s Annual Report on Form 10-K for the year ended December 31, 2025, which includes a broader discussion of the Company’s business and the risks inherent therein.

Note 2 — Going Concern and Management’s Plans

The Company’s operating activities to date have been devoted to seeking licenses, engaging in research and development activities, potential asset and business acquisitions, expenditures associated with the previously planned commercial launch of ENTADFI, and the commercialization of Proclarix.

The Company has incurred substantial operating losses since inception and expects to continue to incur significant operating losses for the foreseeable future.

As of March 31, 2026, the Company had cash of approximately $3.7 million, a working capital surplus of approximately $1.3 million and an accumulated deficit of approximately $135.4 million. During the three months ended March 31, 2026, the Company used approximately $2.1 million in cash for operating activities. In addition, as of May 11, 2026, the Company’s cash balance was approximately $4.1 million.

The Company successfully closed a Series D financing and a Series E financing in September 2025 and October 2025, respectively. These financings provided the Company with additional cash flow to support near-term operations. While these capital raises may enable the Company to sustain current operations and meet existing obligations, the Company continues to generate recurring net operating losses and has not yet established sustained positive cash flows to support its strategic growth initiatives, which includes the commercialization of Proclarix, and participation in strategic transactions and investments, including its involvement with Realbotix. These factors raise substantial doubt about the Company’s ability to continue as a going concern within one year from the date of the issuance of these consolidated financial statements.

Management’s plans for funding the Company’s operations include advancing its strategic initiatives, including commercialization efforts related to Proclarix, and execution of recent and potential strategic transactions. Management also intends to pursue additional equity or debt financing to support operations and strategic initiatives. However, there are currently no committed sources of financing, and there is no assurance that additional funding will be available on favorable terms, if at all. This uncertainty raises significant concern about the Company’s ability to sustain operations and execute its strategic initiatives. If additional capital is not secured, the Company may need to curtail clinical trials, development, and commercialization efforts, and take further measures to reduce expenses to conserve cash.

Because of historical and expected operating losses and net operating cash flow deficits, there is substantial doubt about the Company’s ability to continue as a going concern for one year from the issuance of the unaudited condensed consolidated financial statements, which is not alleviated by management’s plans. The unaudited condensed consolidated financial statements have been prepared under the going concern basis of accounting. These unaudited condensed consolidated financial statements do not include any adjustments that might be necessary from the outcome of this uncertainty.

Note 3 — Summary of Significant Accounting Policies

During the three months ended March 31, 2026, there were no changes to the Company’s significant accounting policies described in the Company’s Annual Report on Form 10-K for the year ended December 31, 2025. Selected significant accounting policies are discussed in further detail below:

Fair Value Measurements

Fair value is defined as the price that would be received for sale of an asset or paid for transfer of a liability, in an orderly transaction between market participants at the measurement date. U.S. GAAP establishes a three-tier fair value hierarchy, which prioritizes the inputs used in measuring fair value. The hierarchy gives the highest priority to unadjusted quoted prices in active markets for identical assets or liabilities (Level 1 measurements) and the lowest priority to unobservable inputs (Level 3 measurements). These tiers include:

In some circumstances, the inputs used to measure fair value might be categorized within different levels of the fair value hierarchy. In those instances, the fair value measurement is categorized in its entirety in the fair value hierarchy based on the lowest level input that is significant to the fair value measurement. Financial instruments, including cash, inventory, accounts receivable, accounts payable, accrued liabilities, operating lease liabilities, and notes payable are carried at cost, which management believes approximates fair value due to the short-term nature of these instruments.

The fair value of the contingent warrant liability and the related party subscription agreement liability are valued using significant unobservable measures and other fair value inputs and are therefore classified as Level 3 financial instruments.

The fair value of financial instruments measured on a recurring basis is as follows as of March 31, 2026 and December 31, 2025:

Note 3 — Summary of Significant Accounting Policies(cont.)

These non-financial assets had been valued using significant unobservable measures and other fair value inputs and were classified as Level 3 measurements.

None of the Company’s other non-financial assets or liabilities are recorded at fair value on a non-recurring basis as of March 31, 2026 and December 31, 2025. There were no transfers between levels during the periods presented.

Revenue Recognition

The following is a description of principal activities from which the Company generates its revenue:

Development Services

Proteomedix provides a range of services to life sciences customers referred to as “Development Services” including testing for biomarker discovery, assay design and development. These Development Services are performed under individual statement of work (“SOW”) arrangements with specific deliverables defined by the customer. Development Services are generally performed on a time and materials basis. During the performance and through completion of the service to the customer in accordance with the SOW, the Company has the right to bill the customer for the agreed upon price and recognizes the Development Services revenue over the period estimated to complete the SOW. The Company generally identifies each SOW as a single performance obligation.

Completion of the service and satisfaction of the performance obligation under a SOW is typically evidenced by access to the data or test made available to the customer or any other form or applicable manner of delivery defined in the SOW. However, for certain SOWs under which work is performed pursuant to the customer’s highly customized specifications, the Company has the enforceable right to bill the customer for work completed, rather than upon completion of the SOW. For those SOWs, the Company recognizes revenue over a period of time during which the work is performed based on the expended efforts (inputs). As the performance obligation under the SOW is satisfied, any amounts earned as revenue and billed to the customer are included in accounts receivable.

Product Sales

The Company derives revenue through sales of its products, which includes Proclarix, its diagnostic product, directly to end users, including laboratories, hospitals, and medical centers, and to distributors. The Company considers customer purchase orders, which in some cases are governed by master sales agreements or standard terms and conditions, to be the contracts with a customer. For each contract, the Company considers the promise to transfer products, each of which is distinct, to be the identified performance obligations. In determining the transaction price, the Company evaluates whether the price is subject to refund or adjustment to determine the net consideration to which it expects to be entitled. The Company fulfills its performance obligation applicable to product sales once the product is transferred to the customer.

Other Revenue

The Company generates other revenue including license revenue through agreements that grant third parties rights to use its intellectual property and proprietary materials. In September 2025, the Company entered into a license agreement with Immunovia AB, under which it granted exclusive rights to certain intellectual property and transferred biological materials related to the PancreaSure™ test. The agreement included two non-refundable payments of $0.3 million. Based on the terms of the agreement and the nature of the license, the Company determined that the performance obligations were satisfied upon the transfer of the licensed rights. Accordingly, the Company recognized $0.6 million as license revenue during the year ended December 31, 2025. The license agreement also states that the Company shall earn a 3% royalty on any sales Immunovia has from products developed using the licensed intellectual property. Further, Immunovia agreed to pay the Company $0.1 million for the delivery of the biological materials. As of March 31, 2026, the Company had not recognized any revenue due to the royalties or due to the biological materials.

During the three months ended March 31, 2026 and 2025, the Company recognized revenue of approximately$0.02 million and $0.1 million, respectively.

Any revenues earned but not yet billed to the customer as of the date of the condensed consolidated financial statements are recorded as contract assets and are included in prepaid expenses and other current assets in the accompanying condensed consolidated financial statements. The Company had no unbilled accounts receivable as of March 31, 2026 and December 31, 2025. Amounts recorded in contract assets are reclassified to accounts receivable in our condensed consolidated financial statements when the customer is invoiced according to the billing schedule in the contract. Accounts receivable was approximately $0.04 million and $0.3 million as of March 31, 2026 and December 31, 2025, respectively.

Note 3 — Summary of Significant Accounting Policies (cont.)

In relation to customer contracts, the Company incurs costs to fulfill a contract but does not incur costs to obtain a contract. These costs to fulfill a contract do not meet the criteria for capitalization and are expensed as incurred.

New Accounting Pronouncements

There were no new accounting pronouncements issued since the Company’s filing of the Annual Report on Form 10-K for the year ended December 31, 2025, which could have a significant effect on the accompanying condensed consolidated financial statements.

Note 4 — Balance Sheet Details

Inventories

Inventories, which primarily relate to Proclarix product as of March 31, 2026 and Proclarix products as of December 31, 2025, consisted of the following:

Prepaid Expenses and Other Current Assets

Prepaid expenses and other current assets consisted of the following as of March 31, 2026, and December 31, 2025:

Goodwill

Goodwill consisted of the following as of March 31, 2026 and December 31, 2025:

Note 4 — Balance Sheet Details(cont.)

Impairments for three months ended March 31, 2026 and 2025

During the three months ended March 31, 2026 and 2025, the Company’s stock price and market capitalization declined, and the Company determined that this was an indicator of a potential impairment of its goodwill. Accordingly, as of March 31, 2026 and 2025, the Company performed quantitative analysis to identify and measure the amount of impairment losses to be recognized. The Company recognized goodwill impairment losses of approximately $8.1 million and $10.9 million for the three months ended March 31, 2026 and 2025, respectively.

Under the income approach, the Company estimated the fair value of the reporting unit based on the present value of estimated future cash flows, which the Company considers to be a Level 3 unobservable input in the fair value hierarchy. The Company prepared cash flow projections based on management’s estimates of future revenue and operating costs, taking into consideration the historical performance and the current macroeconomic, industry, and market conditions. The Company based the discount rate on the weighted-average cost of capital considering Company-specific characteristics and changes in the reporting unit’s projected cash flows. Under the market approach, the Company estimated the fair value of the reporting unit based on revenue market multiples derived from comparable companies with similar characteristics as the reporting unit, as well as an estimated control premium.

Accrued Expenses

Accrued expenses consisted of the following as of March 31, 2026 and December 31, 2025:

Note 5 — Significant Agreements

Immunovia AB

On September 17, 2025, Proteomedix entered into a license agreement with Immunovia AB, pursuant to which Immunovia obtained exclusive rights to certain intellectual property and proprietary biological materials related to the PancreaSure™ test. In exchange for these rights, Immunovia paid Proteomedix a non-refundable upfront license fee of $0.3 million. Based on the terms of the agreement and the nature of the license, the Company determined that the performance obligations were satisfied upon the transfer of the licensed rights. Accordingly, the Company recognized the $0.6 million as license revenue during the year ended December 31, 2025. Additionally, the agreement provided for a second payment of $0.3 million due by March 31, 2026, which was received during the three months ended March 31, 2026, and is no longer shown as a part of Accounts receivable, net on the consolidated balance sheet as of March 31, 2026.

Notes 6 — Notes Payable

Insurance Financing

During the three months ended March 31, 2026, the Company obtained financing for certain Director & Officer liability insurance policy premiums. The agreement assigns the lender a first priority lien on and security interest in the financed policies and any additional premium required in the financed policies.

The total premiums, taxes and fees financed are approximately $0.3 million, with an annual interest rate of 8.5%. In consideration of the premium payment by the lender to the insurance companies or the agent or broker, the Company unconditionally promised to pay the lender the amount financed plus interest and other charges permitted under the agreement. At March 31, 2026, the Company recognized approximately $0.2 million as an insurance financing note payable, which is included in the current portion of notes payable in the accompanying condensed consolidated balance sheets. The Company will pay the insurance financing through monthly installment payments of approximately $25,693, with the last payment for the note due on December 17, 2026.

During the three months ended March 31, 2026, the Company recorded approximately $2,000 of interest expense. As of March 31, 2026 and December 31, 2025, the Company has recorded accrued interest of approximately $2,000 and $0, respectively, which is included in accrued expenses in the accompanying condensed consolidated balance sheets.

Note 7 — Subscription Agreement

On December 18, 2023, the Company entered into a subscription agreement (the “Subscription Agreement”) with the PMX Investor, who became a stockholder of Onconetix at the closing of the PMX Transaction, for the sale of 1,176 units, each comprised of 1 share of common stock and 0.30 pre-funded warrants (the “Units”) at $4,250 per Unit. The Subscription Agreement includes a make-whole provision (the “Make-Whole Provision”) which requires the issuance of additional shares of common stock in the event that the 270-day volume weighted average price after the closing of the Subscription Agreement, is below $4,250, and the PMX Investor still holds the common shares acquired upon closing of the Subscription Agreement 270 days after such closing. The Subscription Agreement would only close upon obtaining stockholder approval for certain transactions involving the Company’s Series B Preferred Stock. The Subscription Agreement was amended on January 23, 2024 to include a provision for interest on the $5 million debenture, accruing at a rate of 4%, to be included in the calculation of the units to be issued upon the conversion. Stockholder approval was obtained on September 5, 2024, and as a result, the conversion and the issuance of 1,176 units, attributable to the Subscription Agreement, and 32 units, attributable to additional accrued interest under the debenture to the PMX Investor took place on September 24, 2024.

As of March 31, 2026 and December 31, 2025, the fair value of the related party subscription agreement liability was $0. The change in fair value of the related party subscription agreement liability for the three months ended March 31, 2026 and 2025 was $0 and a decrease of $3,319,000, respectively.

Note 8 — Warrant and derivative liabilities

Contingent warrant liabilities

The following table summarizes the activity for the contingent warrant liabilities, using unobservable Level 3 inputs, for the three months ended March 31, 2026:

Series D derivative liabilities and warrant liabilities

On September 22, 2025, the Company completed a private placement transaction with institutional investors, resulting in the issuance of Series D convertible preferred stock and accompanying warrants to purchase shares of common stock. In connection with the Series D PIPE Financing, the Company recorded warrant liabilities related to the Series D Warrants and derivative liabilities associated with certain embedded features in the Series D Preferred Stock. These instruments were classified as liabilities and measured at fair value in accordance with ASC 815 due to their settlement provisions and other contractual terms. Refer to Note 9 for further details on the private placement transaction.

The Company measured its bifurcated embedded derivative liabilities and warrant liabilities as of March 31, 2026, December 31, 2025 and September 22, 2025, at fair value on a recurring basis using level 3 inputs. These financial instruments are measured using management’s best estimate of fair value, where the inputs into the determination of fair value require significant management judgment to estimation. The derivative liabilities and warrant liabilities were both measured using Monte Carlo valuation models. Valuations based on unobservable inputs are highly subjective and require significant judgments. Changes in such judgments could have a material impact on fair value estimates.

As of December 11, 2025, the Company had entered a letter of intent with Realbotix (“LOI”), which contemplates a change of control transaction. A closing condition of the LOI is that no convertible securities of the Company will be outstanding prior to, or upon, closing (subject to approval of the preferred shareholders) which creates two distinct timing scenarios for the settlement of the preferred securities: prior to, or at closing, pursuant to the terms of the LOI or after closing in the event the transaction proposed by the LOI is not completed. Given the disparate timing conditions, the valuation included two scenarios in the Monte Carlo valuation analysis as of March 31, 2026 and December 31, 2025: Closing and No Closing. The Closing scenario includes settlement logic for the preferred securities based on the profit-maximizing outcome of the preferred shareholder at the hypothetical closing date. The No Closing scenario models the embedded derivatives as if there was no forced conversion event (similar to valuation analyses of the embedded derivatives as of their original issuance and September 30, 2025).

The table below shows the inputs used to determine the fair value of the derivative liabilities:

The Limited Waiver Agreement executed on December 23, 2025 resulted in reclassification of the warrants to equity, the warrant liability was remeasured using inputs as of December 23, 2025, and no subsequent liability remeasurement was required through December 31, 2025.

Note 8 — Warrant and derivative liabilities(cont.)

The following table presents information about the Company’s derivative liabilities that are measured at fair value on a recurring basis as of March 31, 2026 and December 31, 2025, and indicates the fair value hierarchy of the valuation inputs the Company utilized to determine such fair value:

The following table sets forth a summary of the change in the fair value of the derivative liabilities that are measured at fair value on a recurring basis for the three months ended March 31, 2026:

Series E derivative liabilities and warrant liabilities

On October 1, 2025, the Company completed a private placement transaction with institutional investors, resulting in the issuance of Series E convertible preferred stock and accompanying warrants to purchase shares of common stock. In connection with the Series E PIPE financing, the Company recorded warrant liabilities related to the Series E Warrants and derivative liabilities associated with certain embedded features in the Series E Preferred Stock. These instruments were classified as liabilities and measured at fair value in accordance with ASC 815 due to their settlement provisions and other contractual terms. Refer to Note 9 for further detail on the private placement transaction.

The Company measures its bifurcated embedded derivative liability and warrant liability as of March 31, 2026, December 31, 2025 and issuance, at fair value on a recurring basis using level 3 inputs. These financial instruments are measured using management’s best estimate of fair value, where the inputs into the determination of fair value require significant management judgment to estimation. The derivative liability and warrant liability were both measured using Monte Carlo valuation models. Valuations based on unobservable inputs are highly subjective and require significant judgments. Changes in such judgments could have a material impact on fair value estimates.

As of December 11, 2025, the Company had entered a letter of intent with Realbotix (“LOI”), which contemplates a change of control transaction. A closing condition of the LOI is that no convertible securities of the Company will be outstanding prior to, or upon, closing (subject to approval of the preferred shareholders) which creates two distinct timing scenarios for the settlement of the preferred securities: prior to, or at closing, pursuant to the terms of the LOI or after closing in the event the transaction proposed by the LOI is not completed. Given the disparate timing conditions, the valuation included two scenarios in the Monte Carlo valuation analysis as of March 31, 2026 and December 31, 2025: Closing and No Closing. The Closing scenario includes settlement logic for the preferred securities based on the profit-maximizing outcome of the preferred shareholder at the hypothetical closing date. The No Closing scenario models the embedded derivatives as if there was no forced conversion event (similar to valuation analyses of the embedded derivatives as of their original issuance and September 30, 2025).

Note 8 — Warrant and derivative liabilities (cont.)

The table below shows the inputs used to determine the fair value of the derivative liabilities:

The Limited Waiver Agreement executed on December 23, 2025 resulted in reclassification of the warrants to equity, the warrant liability was remeasured using inputs as of December 23, 2025, and no subsequent liability remeasurement was required through December 31, 2025.

The following table presents information about the Company’s derivative liabilities that are measured at fair value on a recurring basis as of March 31, 2026 and December 31, 2025, and indicates the fair value hierarchy of the valuation inputs the Company utilized to determine such fair value:

The following table sets forth a summary of the change in the fair value of the derivative liabilities that are measured at fair value on a recurring basis for the three months ended March 31, 2026:

Note 9 — Convertible Preferred Stock and Stockholders’ Equity

Authorized Capital

As of March 31, 2026 and December 31, 2025, the Company is authorized to issue 250,000,000 shares and 10,000,000 shares of common stock and preferred stock, respectively, with a par value of $0.00001 for both common stock and preferred stock.

At March 31, 2026 and December 31, 2025, the Company had designated 1,150,000 shares,10,000 shares,2,700,000 shares,10,000 shares,32,000 shares, and 10,000 shares of Series Seed Preferred Stock, Series A Preferred Stock, Series B Preferred Stock, Series C Preferred Stock, Series D Preferred Stock, and Series E Preferred Stock, respectively.

Note 9 — Convertible Preferred Stock and Stockholders’ Equity (cont.)

Preferred Stock

Series Seed Convertible Preferred Stock

The Company has 1,150,000 shares of preferred stock designated as Series Seed Preferred Stock (“Series Seed”) and there areno shares of Series Seed outstanding as of March 31, 2026 and December 31, 2025.

Series A Convertible Preferred Stock

On September 29, 2023, the Company filed a Certificate of Designations of Rights and Preferences of Series A Preferred Stock of the Company (the “Series A Certificate of Designations”) with the State of Delaware to designate and authorize the issuance of up to 10,000 shares of Series A Preferred Stock.

On October 3, 2023, the Company issued 3,000 shares of Series A Convertible Preferred Stock in exchange for the settlement of $3.0 million in notes payable due to Veru, Inc.

On September 24, 2024, Veru converted all 3,000 shares of Series A Convertible Preferred Stock into 335 shares of the Company’s common stock per the stated conversion ratio. There were 0 shares of Series A Convertible Stock outstanding as of March 31, 2026 and December 31, 2025.

Series B Convertible Preferred Stock

In connection with the PMX acquisition on December 15, 2023, the Company issued 2,696,729 shares of Series B Convertible Preferred Stock, which were initially convertible into approximately 15,863 shares of common stock, subject to stockholder approval on September 5, 2024. All Series B Preferred Stock was fully converted into common stock on September 24, 2024. As of March 31, 2026 and December 31, 2025, no Series B Preferred Stock remains outstanding.

Series C Convertible Preferred Stock

On October 1, 2024, the Board of Directors 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 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 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 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 Conversion Amount of such Preferred Share by (y) the Conversion Price, $22.528, subject to adjustment as provided in the Certificate of Designations.

On July 16, 2025, the Company exercised its voluntary Series C Preferred Stock adjustment right to lower the conversion price of the Series C Preferred Stock to $17.50, and holders of 1,920 shares of Series C Preferred Stock agreed to convert their shares into shares of Common Stock. During the year ended December 31, 2025,1,369 shares of Series C Preferred Stock were redeemed for an aggregate amount of $1.71 million,1,920 shares of Series C Preferred Stock were converted into common stock and 203 shares of Series C Preferred Stock were exchanged into 244 shares of Series D Preferred Stock (as defined below). As of March 31, 2026 and December 31, 2025,7 shares of Series C Preferred Stock remain outstanding, with a carrying value of $1.7 thousand, as reflected in the accompanying consolidated balance sheet.

Series D Preferred Stock

On September 22, 2025, the Company entered into a securities purchase agreement (the “Series D Securities Purchase Agreement” and the financing contemplated therein, the “Series D PIPE Financing”) 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 purchase 872,565 shares of Common Stock, (the Series D Preferred Stock together with the Series D Warrants, the “Series D PIPE Securities”), for an aggregate purchase price of approximately $12.9 million and net cash proceeds of $9.3 million. The exercise price of the Series D Warrants is $18.448, and the Series D Warrants are exercisable beginning on the issuance date and expire on the third anniversary of the issuance date.

The Series D Preferred Stock was determined to be more akin to an equity-like host than a debt-like host and was classified as permanent equity as it was not redeemable in any manner that would require classification outside of permanent equity pursuant to ASC 480-10-S99. The Series D Preferred Stock was recorded on the accompanying consolidated balance sheet at its par value. Certain embedded share-settled redemption features within the Series D Preferred Stock were bifurcated and accounted for separately a derivative liability.

The Series D Warrants and certain embedded share-settled redemption features of the Series D Preferred Stock issued were determined to be liability-classified instruments pursuant to ASC 480 and ASC 815. The embedded features of the Series D Preferred Stock were bifurcated and accounted for separately as derivative liabilities. The Company measured the warrant liabilities and bifurcated derivative liabilities at fair value on a recurring basis using Level 3 inputs as of September 22, 2025 (the issuance date), December 23, 2025 (amended warrants date), December 31, 2025 (derivative liabilities fair value date) and March 31, 2026, respectively. See Note 8 for further information regarding the valuation methodology and assumptions used in determining the fair value of the warrant and derivative liabilities.

The Series D Preferred Stock hasno voting rights. The Series D Preferred Stock are convertible into common stock at the election of the holders of the Series D Preferred Stock at any time at an initial conversion price of $18.448 per share. The conversion price is subject to customary adjustments for stock dividends, stock splits, reclassifications, stock combinations and the like (subject to certain exceptions), anti-dilution provisions, and a floor price of $0.5322.

The Series D Preferred Stock is not redeemable by the holder except in the event of 1) a liquidation, dissolution, or winding up, or 2) the Series D Preferred Stock is redeemable for common stock of the Company upon the occurrence of a change in control. Holders of the Series D Preferred Stock shall be entitled to receive dividends as authorized and declared by the Company’s Board of Directors, payable in cash, securities, or in other assets as determined by the Company’s Board of Directors.

In the event of the Company’s liquidation, dissolution, or winding up, holders of the Series D Preferred Stock will be entitled to receive out of the assets, whether capital or surplus, an amount equal to the stated value of the Series D Preferred Stock, plus any accrued and unpaid dividends thereon and any other fees or liquidated damages owed before any distribution or payment shall be made to the holders of any junior securities.

During the three months ended March 31, 2026, holders of Series D Preferred Stock converted 6,373 shares into 2,222,656 shares of common stock. As of March 31, 2026 and December 31, 2025,9,952 and 16,325 shares of Series D Preferred Stock remain outstanding, respectively.

Series E Preferred Stock

On October 1, 2025, Onconetix entered into, and sold to institutional investor(s) (collectively, the “PIPE Investors”), pursuant to a securities purchase agreement (the “Securities Purchase Agreement”) 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 (the “Common Stock”) and warrants to purchase 405,045 shares of Common Stock (the “Warrants” and, together with the Series E Preferred Stock, the “PIPE Securities”), for an aggregate purchase price of approximately $6.25 million and net cash proceeds of $6.2 million. Such investment is referred to as the “PIPE Financing”. The exercise price of the Series E Warrants is $19.288, and the Series E Warrants are exercisable beginning on the issuance date and expire on the third anniversary of the issuance date.

The Series E Preferred Stock was determined to be more akin to an equity-like host than a debt-like host and was classified as permanent equity as it was not redeemable in any manner that would require classification outside of permanent equity pursuant to ASC 480-10-S99. The Series E Preferred Stock was recorded on the accompanying consolidated balance sheet at its par value. Certain embedded share-settled redemption features within the Series E Preferred Stock were bifurcated and accounted for separately a derivative liability.

The Series E Warrants and certain embedded share-settled redemption features of the Series E Preferred Stock issued were determined to be liability-classified instruments pursuant to ASC 480 and ASC 815. The embedded features of the Series E Preferred Stock were bifurcated and accounted for separately as derivative liabilities. The Company measured the warrant liabilities and bifurcated derivative liabilities at fair value on a recurring basis using Level 3 inputs as of October 1, 2025 (the issuance date), December 23, 2025 (amended warrants date) and December 31, 2025 (derivative liabilities fair value date), and March 31, 2026. See Note 8 for further information regarding the valuation methodology and assumptions used in determining the fair value of the warrant and derivative liabilities.

The Series E Preferred Stock hasno voting rights. The Series E Preferred Stock are convertible into common stock at the election of the holders of the Series E Preferred Stock at any time at an initial conversion price of $19.288 per share. The conversion price is subject to customary adjustments for stock dividends, stock splits, reclassifications, stock combinations and the like (subject to certain exceptions), anti-dilution provisions, and a floor price of $0.298.

The Series E Preferred Stock is not redeemable by the holder except in the event of 1) a liquidation, dissolution, or winding up, or 2) the Series E Preferred Stock is redeemable for common stock of the Company upon the occurrence of a change in control. Holders of the Series E Preferred Stock shall be entitled to receive dividends as authorized and declared by the Company’s Board of Directors, payable in cash, securities, or in other assets as determined by the Company’s Board of Directors.

In the event of the Company’s liquidation, dissolution, or winding up, holders of the Series E Preferred Stock will be entitled to receive out of the assets, whether capital or surplus, an amount equal to the stated value of the Series E Preferred Stock, plus any accrued and unpaid dividends thereon and any other fees or liquidated damages owed before any distribution or payment shall be made to the holders of any junior securities.

During the three months ended March 31, 2026, holders of Series E Preferred Stock converted 232 shares into 76,555 shares of common stock. As of March 31, 2026 and December 31, 2025,7,581 and 7,813 shares of Series E Preferred Stock remain outstanding, respectively.

October 2024 ELOC

Concurrently, on October 2, 2024, the Company entered into a Common Stock Equity Line of Credit Purchase Agreement (the “ELOC Purchase Agreement”) with an institutional investor, whereby the Company may sell up to $25,000,000 of the Company’s new issued Common Stock. Pursuant to the ELOC Purchase Agreement, the investor shall purchase from the Company up to the lesser of (i) $25.0 million in shares of our Common Stock and (ii)3,902 shares, representing 19.99% of the total number of shares of Common Stock outstanding immediately prior to the execution of the ELOC Purchase Agreement. Pursuant to the ELOC Purchase Agreement,30% of the gross proceeds to the Company from any sale of common stock thereunder must be applied towards the redemption of the Series C Redeemable Preferred Stock.

During the three months ended March 31, 2026 and 2025, the Company received proceeds of $0 and $4.8 million under the ELOC, respectively.

Common Stock

As of March 31, 2026 and December 31, 2025 there were 2,755,184 and 312,028 shares of common stock issued, respectively, and 2,755,154 and 311,998 shares of common stock outstanding, respectively.

Treasury Stock

On November 10, 2022, the Board approved a stock repurchase program (the “Repurchase Program”) to allow the Company to repurchase up to 125,000 shares of common stock with a maximum price of $1.00 per share, with discretion to management to make purchases subject to market conditions. On November 18, 2022, the Board approved an increase to the maximum price to $2.00 per share. There was no expiration date for this program and prices are not adjusted for the reverse stock split to comply with the program.

There wereno repurchases of common stock during the three months ended March 31, 2026 and 2025.

On November 13, 2024, the Board terminated the Repurchase Program.

Warrants

The following summarizes the Company’s outstanding warrants, excluding contingent warrants issuable upon exercise of the outstanding warrants as of March 31, 2026:

As of March 31, 2026, the Company had outstanding warrants, which are exercisable into 1,136,288 shares of common stock. The shares of common stock underlying the warrants outstanding had an exercise price of $26.26 per share, based on the closing trading price on March 31, 2026.

Contingent Warrant Liabilities

As of March 31, 2026, the fair value of contingent warrant labilities includes the Series C PIPE warrants of $4,700 and those issuable upon exercise of the Inducement PIOs of approximately $20,278 totaling $24,978 included as contingent warrant liabilities in the accompanying condensed consolidated balance sheets.

As of December 31, 2025, the fair value of contingent warrant labilities includes the Series C Warrants of $6,300 and those issuable upon exercise of the Inducement PIOs of approximately $20,290 totaling $26,590 included as contingent warrant liabilities in the accompanying consolidated balance sheets.

Onconetix Equity Incentive Plans

The Company’s 2019 Equity Incentive Plan (the “2019 Plan”) was adopted by its board of directors and by its stockholders on July 1, 2019. On February 23, 2022 the Company’s board of directors adopted the Company’s 2022 Equity Incentive Plan (the “2022 Plan”), which is the successor and continuation of the Company’s 2019 Plan. Under the 2022 Plan, the Company may grant stock options, restricted stock, restricted stock units, stock appreciation rights, and other forms of awards to employees, directors, and consultants of the Company. In May 2023, the number of shares of common stock reserved for issuance under the 2022 Plan was increased to 185, and in September 2024, the number of shares of common stock reserved for issuance under the 2022 Plan was increased to 3,411. Stock-based awards granted during the three months ended March 31, 2026 and 2025 were all granted under the 2022 Plan. As of March 31, 2026, there are 1,752 shares available for issuance under the 2022 Plan.

Stock Options

The following summarizes activity related to the Company’s stock options under the 2019 Plan and the 2022 Plan for the three months ended March 31, 2026:

There wereno stock options granted during the three months ended March 31, 2026 and 2025.

The aggregate fair value of stock options that vested during the three months ended March 31, 2026 and 2025 was approximately $0 and $46,000, respectively.

Restricted Stock

On May 9, 2023, the Board’s Compensation Committee approved the issuance of restricted stock, granted under the Company’s 2022 Plan, to the Company’s executive officers, employees, and certain of the Company’s consultants. The restricted shares granted totaled 28, of which 8,4, and 8 were granted to the Company’s former CEO, former CFO, and former CBO, respectively. All of the restricted shares granted vest as follows:50% in January 2024,25% in August 2024, and 25% in August 2025. In addition, on May 31, 2023, the Board’s Compensation Committee approved the issuance of 1 share of restricted stock, granted to the Company’s non-executive Board members, with full vesting on May 31, 2024. Furthermore, on September 26, 2024, the Company issued its Board members a total of 39 restricted stock, with full vesting August 31, 2025. On February 24, 2025, in connection with the appointment of an executive Board member, the Company issued 4 shares of restricted stock with full vesting August 31, 2025. Subsequently, the Company modified the vesting date of 27 shares previously issued to the Board members to provide for full vesting August 31, 2026. On August 15, 2025, the Company issued its Board members a total of 494 restricted stock, with full vesting August 16, 2026.

The following summarizes activity related to the Company’s restricted stock awards granted under the 2022 Plan for the three months ended March 31, 2026:

Proteomedix Stock Option Plan

Proteomedix sponsors a stock option plan (the “PMX Option Plan”) which provides common stock option grants to be granted to certain employees and consultants, as was determined by the board of directors of Proteomedix. In connection with the PMX Transaction, the Company assumed the PMX Option Plan.

Generally, options issued under the PMX Option Plan have a term of not more than 11 years and provide for a four-year vesting period. Stock options issued under the PMX Option Plan are measured at fair value using the Black-Scholes option pricing model.

Note 9 — Convertible Preferred Stock and Stockholders’ Equity (cont.)

There was no activity under the PMX Option Plan for the three months ended March 31, 2026 and 2025. As of March 31, 2026 and December 31, 2025, there wereno outstanding stock options.

Stock-Based Compensation

Stock-based compensation expense related to stock options and restricted stock, for the three months ended March 31, 2026 and 2025 was as follows:

Note 10 — Commitments and Contingencies

Office Lease

Proteomedix leases office and lab space in Zurich Switzerland. In May 2025, Proteomedix entered into a lease amendment to reduce its leased premises. Effective June 30, 2025, the Company terminated the April 2024 lease amendment, which included office space and laboratory space. Additionally, a partial termination of a prior lease amendment further reduced the office space.

This lease expired on December 31, 2025, and was renewed for a successive two-year term, resulting in an additional right-of-use asset and lease liability of approximately $49,000. The lease, as renewed, requires payments of approximately $24,000 over the next twelve months. The lease will automatically renew for successive two-year terms, unless terminated. Either party may terminate the lease with twelve months’ written notice.

Litigation

From time to time, the Company may be subject to various legal proceedings and claims that arise in the ordinary course of its business activities. As of March 31, 2026, the Company is not a party to any material legal proceedings and is not aware of any pending or threatened claims.

Indemnification

In the normal course of business, the Company enters into contracts and agreements that contain a variety of representations and warranties and provide for general indemnifications. The Company’s exposure under these agreements is unknown because it involves claims that may be made against the Company in the future but have not yet been made. To date, the Company has not been required to defend any action related to its indemnification obligations. The maximum potential amount of future payments the Company could be required to make under these indemnification agreements is not estimable at this time.

Note 11 — Related Party Transactions

On June 17, 2025, the Company entered into a separate consulting agreement with a firm affiliated with Dr. Meier. The agreement provides for the payment of certain success fees and reimbursement of related expenses. Under its terms, Dr. Meier is entitled to earn up to 10% of success fees for transactions greater than $9 million earned by the affiliated firm, payable only upon receipt of such proceeds. The Company recorded approximately $0 in related expenses during the three months ended March 31, 2026 and 2025. As of March 31, 2026 and December 31, approximately $16,500 related to this agreement was included in accounts payable.

Note 12 — Net Loss Per Share

Basic net loss per share is computed by dividing the net income or loss applicable to common shares by the weighted average number of common shares outstanding during the period. The weighted average number of shares of common stock outstanding includes pre-funded warrants because their exercise requires only nominal consideration for delivery of shares; it does not include any potentially dilutive securities or any unvested restricted shares of common stock. Certain restricted shares, although classified as issued and outstanding at March 31, 2026, are considered contingently returnable until the restrictions lapse and will not be included in the basic net loss per share calculation until the shares are vested. Unvested shares of the Company’s restricted stock do not contain non-forfeitable rights to dividends and dividend equivalents.

The two-class method is used to determine earnings per share based on participation rights of participating securities in any undistributed earnings. Each share of preferred stock that includes rights to participate in distributed earnings is considered a participating security and the Company uses the two-class method to calculate net income available to the Company’s common stockholders per common share — basic and diluted.

The following securities were excluded from the computation of diluted shares outstanding due to the losses incurred in the periods presented, as they would have had an anti-dilutive impact on the Company’s net loss:

Note 13 – Segment Information

The Company conducts its business activities and reports financial results asone business segment. The presentation of financial results asone reportable segment is consistent with the way the Company operates its business and is consistent with the manner in which the Chief Operating Decision Maker (“CODM”) evaluates performance and makes resource and operating decisions for the business. The Company’s CODM is the Chief Executive Officer. Furthermore, the Company notes that monitoring financial results as one reportable segment helps the CODM manage costs on a consolidated basis, consistent with the integrated nature of the operations. The CODM uses net loss, as reported on the Consolidated Statements of Operations and Comprehensive Loss, in evaluating performance of the Company and determining how to allocate resources of the Company as a whole. As the CODM evaluates performance on a consolidated basis, all required financial segment information is included in the consolidated financial statements.

Geographic Information

The distribution of revenue by geographical area was as follows:

Note 14 — Subsequent Events

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, with $5,000 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.

Result of the Special Meeting of Stockholders of the Company held on April 30, 2026:

On April 30, 2026, the Company held a special meeting of stockholders (the “April 2026 Special Meeting”). At the April 2026 Special Meeting, the stockholders of the Company approved the stockholder proposal to grant discretionary authority to Board to amend the Amended and Restated Certificate of Incorporation ofthe Company to effect one or more reverse stock splits of the Common Stock, at a ratio in the range of 1-for-2 to 1-for-10, provided that, (i) the Company shall not effect the aforementioned reverse stock splits that, in the aggregate, exceed 1-for-100, and (ii) any such reverse stock split is completed no later than the one year anniversary date of the April 2026 Special Meeting.

ELOC Draws and Series D & E Preferred Stock Conversions:

In the period between March 31, 2026, and May 12, 2026, the Company issued a total of 8,710,353 shares of common stock through conversions of preferred stock and a sale on the ELOC. The total shares of Series D Preferred Stock converted during this period were 1,796 in exchange for 1,537,118 shares of common stock. The total shares of Series E Preferred Stock converted during this period were 7,581 in exchange for 6,603,654 shares of common stock. The remaining outstanding shares of preferred stock as of May 12, 2026 are 8,156 for Series D Preferred Stock and 0 for Series E Preferred stock. Additionally, the Company received proceeds of approximately $994 thousand on the sale of 569,581 shares under the ELOC.