Exhibit 3.1

CERTIFICATE OF AMENDMENT
OF CERTIFICATE OF INCORPORATION
OF ONCONETIX, INC.

Onconetix, Inc., a corporation organized and existing under the laws of the State of Delaware (the “Corporation”), does hereby certify as follows:

1. The name of the Corporation is Onconetix, Inc.

2. The Certificate of Incorporation of the Corporation is amended by amending and restating Section D of Article IV in its entirety to read as follows:

D. Upon the filing and effectiveness (the “Effective Time”) of this amendment to the Corporation’s Certificate of Incorporation, as amended, pursuant to the Delaware General Corporation Law, each eighty-five (85) shares of the Common Stock issued immediately prior to the Effective Time (the “Old Common Stock”) shall be reclassified and combined into one validly issued, fully paid and non-assessable share of the Corporation’s Common Stock, $0.00001 par value per share (the “New Common Stock”), without any action by the holder thereof (the “Reverse Stock Split”). No fractional shares of New Common Stock shall be issued as a result of the Reverse Stock Split and, in lieu thereof, upon surrender after the Effective Time of a book entry position which formerly represented shares of Old Common Stock that were issued and outstanding immediately prior to the Effective Time, any person who would otherwise be entitled to a fractional share of New Common Stock as a result of the Reverse Stock Split, following the Effective Time, shall be entitled to receive a cash payment equal to the fraction of a share of New Common Stock to which such holder would otherwise be entitled multiplied by the closing price per share of the New Common Stock on The Nasdaq Stock Market LLC at the close of business on the date prior to the Effective Time. Each book entry position that theretofore represented shares of Old Common Stock shall thereafter represent that number of shares of New Common Stock into which the shares of Old Common Stock represented by such book entry position shall have been reclassified and combined; provided, that each person holding of record a book entry position that represented shares of Old Common Stock shall receive, a new book entry position evidencing and representing the number of shares of New Common Stock to which such person is entitled under the foregoing reclassification and combination.

3. This Certificate of Amendment has been duly adopted by the Board of Directors and stockholders of the Corporation in accordance with Section 242 of the General Corporation Law of the State of Delaware.

4. This Certificate of Amendment shall become effective as of 12:01 a.m. Eastern Time on June 13, 2025.

IN WITNESS WHEREOF, the Corporation has caused this Certificate of Amendment to be duly executed in its corporate name as of the 11th day of June, 2025.

Exhibit 10.1

THE ISSUANCE AND SALE OF THE SECURITY REPRESENTED BY THIS PROMISSORY NOTE HAS NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933, AS AMENDED, OR APPLICABLE STATE SECURITIES LAWS. THE SECURITY MAY NOT BE OFFERED FOR SALE, SOLD, TRANSFERRED OR ASSIGNED (i) IN THE ABSENCE OF (A) AN EFFECTIVE REGISTRATION STATEMENT FOR THE SECURITY UNDER THE SECURITIES ACT OF 1933, AS AMENDED, OR (B) AN OPINION OF COUNSEL, IN A FORM GENERALLY ACCEPTABLE TO THE COMPANY’S LEGAL COUNSEL, THAT REGISTRATION IS NOT REQUIRED UNDER SAID ACT OR (ii) UNLESS SOLD PURSUANT TO RULE 144 OR RULE 144A UNDER SAID ACT.

UNSECURED PROMISSORY NOTE

FOR VALUE RECEIVED, Onconetix, Inc., a Delaware corporation (the “Maker”), hereby promises to pay to the order of Keystone Capital Partners, LLC, a Delaware limited liability company or its assigns (“Holder”), the principal amount of $147,058.82 (the “Principal”) due and payable in accordance with the terms hereof.

In lieu of the accrual of interest on the outstanding principal amount hereof on any date prior to the Maturity Date, this Note carries an original issue discount of $22,058.82 (the “OID”); thus, the purchase price of this Note shall be $125,000.00, computed as follows: $147,058.82 initial principal balance less the OID. As set forth in Section 6 herein, this Note shall rank junior to any existing senior debt obligations of the Company (“Senior Indebtedness”).

1. Payment on Maturity. The entire unpaid Principal and OID of this Note, shall be due and payable upon the earlier of (i) the Company’s receipt of sufficient proceeds from that certain Equity Line of Credit (the “ELOC”) by and between the Company and the Holder and (ii) March 5, 20261. For the avoidance of doubt, the Holder shall be entitled to receive all proceeds from the ELOC until the Principal Amount ($147,058.82) has been repaid. The Maker will pay to the Holder of this Note on demand such further amount as shall be sufficient to cover up to $10,000 of costs and expenses of such Holder incurred in the drafting, negotiation, and enforcement or collection of this Note, including, without limitation, reasonable attorneys’ fees, expenses and disbursements. The purchase price of this Note is $125,000.00.

2. Reserved.

3. Mandatory Prepayment. Notwithstanding anything herein to the contrary, so long as any amounts remain outstanding hereunder,

4. Representations and Warranties of Maker. Maker represents and warrants as follows as of the date hereof: (a) it is duly organized, validly existing and in good standing under the laws of its state of Delaware; (b) the execution, delivery and performance by Maker of this Note (i) are within Maker’s powers, (ii) have been duly authorized by all necessary actions, (iii) do not contravene its governing agreements, certificates or other organization documents, (iv) do not contravene any law or any contractual restriction binding on or affecting Maker, and (v) do not require any consent or approval under, violate, conflict with, result in any breach of or any loss of any benefit under, or constitute a default under, result in the acceleration of any obligation under, or result in termination or give to others any right of termination, vesting, amendment or acceleration of any material benefit under, in each case, with or without notice, the lapse of time or both, any contract to which the Maker or any subsidiary of the Maker is a party, or by which they or any of their respective properties or assets are bound; (c) except as may be required by applicable Nasdaq listing rules, no authorization or approval or other action by, and no notice to or filing with any governmental authority or regulatory body is required for the due execution, delivery and performance by Maker of this Note; (d) this Note constitutes the legal, valid and binding obligation of Maker party thereto, enforceable against Maker in accordance with its terms, except to the extent enforceability is limited by bankruptcy, insolvency, fraudulent conveyance, moratorium and other laws for the protection of creditors generally and by general equitable principles; and (e) there is no pending or, to Maker’s knowledge, threatened action or proceeding affecting Maker before any governmental agency or arbitrator with respect to the transactions contemplated by this Note or which may materially adversely affect the property, assets or condition (financial or otherwise) of Maker.

5. Late Charges. Any amount of Principal, OID or other amounts due hereunder which is not paid when due (a “Payment Default”) shall result in a late charge being incurred and payable by the Maker at the rate of fifteen percent (15%) per annum of such amount from the date such amount was due until the same is paid in full (the “Late Charges”).

6. Seniority; Subordination.

(a) The indebtedness evidenced by this Note and the payment of the principal and interest hereunder shall be Senior (as hereinafter defined) to, and have priority in right of payment over, all indebtedness of Maker, now outstanding or hereinafter incurred, except for any Senior Indebtedness and Pari Passu Indebtedness. “Senior,” as used herein, shall be deemed to mean that, in the event of any default in the payment of the obligations represented by this Note (after giving effect to “cure” provisions, if any) or of any liquidation, insolvency, bankruptcy, reorganization, or similar proceedings relating to Maker, all sums payable on this Note shall first be paid in full, with interest, if any, before any payment is made upon any indebtedness, now outstanding or hereinafter incurred, except for Senior Indebtedness and Pari Passu Indebtedness, and, in any such event, any payment or distribution of any character which shall be made in respect of any other indebtedness of Maker, other than Senior Indebtedness and Pari Passu Indebtedness, shall be paid over to Holder for application to the payment hereof, unless and until the obligations under this Note (which shall mean the principal and other obligations arising out of, premium, if any, interest on, and any costs and expenses payable under, this Note) shall have been paid and satisfied in full. “Pari Passu Indebtedness” shall mean indebtedness of Maker that ranks at all times pari passu in right of priority and payment with the claims of other unsecured and unsubordinated creditors[, including, without limitation, Holder and other holders of Notes].

(b) The indebtedness represented by this Note is unsecured and subordinate in right of payment to any Senior Indebtedness; provided, however that the foregoing shall not impair, as between Maker and Holder, the obligation of Maker to pay to Holder the principal and accrued interest as and when the same shall become due and payable, or shall prevent Holder, upon default hereunder, from exercising all rights, powers and remedies otherwise provided herein or by applicable law, all subject to the rights, if any, of the holders of Senior Indebtedness.

7. Indemnification; Expenses. Maker hereby indemnifies and holds harmless Holder, each of its affiliates and correspondents and each of their respective directors, officers, employees, agents and advisors (each an “Indemnified Party”) from and against any and all actions, claims, damages, losses, liabilities, fines, penalties, costs and expenses of any kind (including, without limitation, counsel fees and disbursements in connection with any subpoena, investigative, administrative or judicial proceeding, whether or not the Indemnified Party shall be designated a party thereto) which may be incurred by the Indemnified Party or which may be claimed against the Indemnified Party by any person by reason of or in connection with the execution, delivery or performance of this Note, or action taken or omitted to be taken by Holder under, this Note. Nothing in this paragraph is intended to limit Maker’s obligations contained elsewhere in this Note. Without prejudice to the survival of any other obligation of Maker hereunder, the indemnities and obligations of Maker contained in this paragraph shall survive the payment in full of all obligations hereunder. Maker agrees to pay to the Holder upon demand the amount of any and all costs and expenses, including the reasonable fees, costs, expenses and disbursements of counsel for the Holder and of any experts and agents, which the Holder may incur in connection with (i) the preparation, negotiation, execution, delivery, recordation, administration, amendment, waiver or other modification or termination of this Note, (ii) the custody, preservation, use or operation of, or the sale of, collection from, or other realization upon, any Collateral, (iii) the exercise or enforcement of any of the rights of the Holder hereunder, or (iv) the failure by Maker to perform or observe any of the provisions hereof.

8. Reserved.

9. Miscellaneous.

(a) All amounts to be paid in cash hereunder shall be paid when due by wire transfer in United States dollars and immediately available funds in accordance with the wire instructions delivered to such party entitled to receive such payment prior to such date.

(b) If any cash payment on this Note shall become due on a Saturday, Sunday or a bank or legal holiday, such payment shall be made on the next succeeding business day.

(c) No course of dealing and no delay on the part of the Holder of this Note in exercising any right, power or remedy shall operate as a waiver thereof or otherwise prejudice such Holder’s rights, powers or remedies. No right, power or remedy conferred by this Note upon the Holder hereof shall be exclusive of any other right, power or remedy referred to herein or now or hereafter available at law, in equity, by statute or otherwise.

(d) Maker hereby waives presentment, protest and demand, notice of protest, demand and dishonor and nonpayment of this Note.

(e) If Late Charges or other amounts payable under this Note is in excess of the maximum permitted by law, Late Charges or other amounts chargeable hereunder shall be reduced to the maximum amount permitted by law and any excess over the maximum amount permitted by law shall be credited to the Principal of this Note and applied to the same and not to the payment of Late Charges or such other amounts, as applicable.

(f) Maker hereby (i) irrevocably submits to the jurisdiction of any New York State or Federal court sitting in New York City, New York in any action or proceeding arising out of or relating to this Note, (ii) waive any defense based on doctrines of venue or forum non conveniens, or similar rules or doctrines and (iii) irrevocably agree that all claims in respect of such an action or proceeding may be heard and determined in such New York State or Federal court. This Note shall be governed by, and construed in accordance with, the laws of the State of Delaware. MAKER HEREBY WAIVES ANY RIGHT TO TRIAL BY JURY IN ANY ACTION, PROCEEDING OR COUNTERCLAIM ARISING OUT OF OR RELATING TO THIS NOTE.

(g) This Note shall be binding upon and inure to the benefit of Maker and Holder and their respective successors, assigns, heirs and legal representations, except that Maker may not assign any rights or obligations hereunder without the prior written consent of Holder. Holder may assign to other affiliated entities all or a portion of its rights under this Note.

(h) Maker acknowledges that the transaction of which this Note is a part is a commercial transaction and hereby waives its right to any notice and hearing as may be allowed by any state or federal law with respect to any prejudgment remedy which any Holder or its successors or assigns may use.

(i) The Holder of this Note may proceed to protect and enforce the rights of such Holder by an action at law, suit in equity or other appropriate proceeding, whether for the specific performance of any agreement contained herein, or for an injunction against a violation of any of the terms hereof or thereof, or in aid of the exercise of any power granted hereby or thereby or by law or otherwise.

(j) If this Note is lost or destroyed, Maker shall, at Holder’s request and upon receipt of a lost note affidavit, in a customary form, from the Holder, execute and return to Holder a replacement promissory note identical to this Note. No replacement of this Note shall result in a novation of Maker’s obligations under this Note. Maker acknowledges the need to act promptly upon its receipt of the documentation evidencing any request by Holder that the Note be replaced pursuant to this paragraph and agrees that Maker will meet the reasonable deadlines of Holder provided that Maker has received the applicable documents at least ten (10) business days prior to such deadline. Furthermore, Maker agrees to reasonably cooperate with Holder to effectuate the obtainment of such title policy endorsements, or new title evidence and other assurances and documents as Holder shall reasonably require.

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IN WITNESS WHEREOF, this Note has been executed as of the date first written above.

5

Exhibit 99.1

Onconetix, Inc. Announces 1-for-85 Reverse Stock Split and Results of the Special Meeting of Stockholders

CINCINNATI, Ohio, June 11, 2025 (GLOBE NEWSWIRE) -- Onconetix, Inc. (NASDAQ: ONCO) (“Onconetix” or the “Company”), a commercial-stage biotechnology company focused on the research, development, and commercialization of innovative solutions for men’s health and oncology, today announced that the Company’s stockholders have approved a proposal to effect a reverse split, which was voted on at the Company’s 2025 special meeting of stockholders (the “Special Meeting”) held on May 30, 2025, and that its Board of Directors (the “Board of Directors” or “Board”) approved a 1-for-85 reverse stock split of its outstanding shares of common stock, to be effective as of 12:01 a.m. Eastern Time on June 13, 2025.

Results of the Special Meeting

At the Special Meeting, Onconetix’s stockholders approved the following proposals:

Final voting results from the Special Meeting were reported in a Current Report on Form 8-K filed with the Securities and Exchange Commission (the “SEC”) on June 5, 2025.

Reverse Stock Split

In conjunction with stockholder approval of the reverse stock split, the Company’s Board of Directors determined to fix a split ratio of 1-for-85 shares. The Company’s common stock will begin trading on a reverse stock split-adjusted basis at the opening of the market on June 13, 2025. Following the reverse stock split, the Company’s common stock will continue to trade on The Nasdaq Capital Market under the symbol “ONCO” under the new CUSIP number 68237Q203. The reverse stock split is intended to enable the Company to regain compliance with the minimum bid price requirement of $1.00 per share of common stock for continued listing on The Nasdaq Capital Market.

At the effective time of the reverse split, every 85 issued and outstanding shares of the Company’s common stock will be converted automatically into one share of the Company’s common stock without any change in the par value per share. No fractional shares will be issued in connection with the reverse stock split, and fractional shares resulting from the reverse stock split will be canceled with the holders thereof receiving cash compensation. The amount of compensation will be determined by multiplying the fractional share by the closing price per share of the Company’s common stock on The Nasdaq Capital Market at the close of business on the trading day prior to the effective date of the reserve stock split, or June 12, 2025. The reverse split will have no effect on the number of authorized shares of the Company’s common stock, and the ownership percentage of each stockholder will remain unchanged other than as a result of fractional shares. The reverse stock split will additionally apply to the Company’s common stock issuable upon exercise or conversion of the Company’s equity awards, convertible preferred stock and warrants, as well as the applicable exercise price.

The reverse stock split will reduce the number of outstanding shares of the Company’s common stock from approximately 44.4 million to approximately 521,863.

About Onconetix, Inc.

Onconetix, Inc. is a commercial-stage biotechnology company focused on the research, development, and commercialization of innovative solutions for men’s health and oncology. The Company owns 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. The Company also owns ENTADFI, an FDA-approved, once-daily pill that combines finasteride and tadalafil for the treatment of benign prostatic hyperplasia, a disorder of the prostate. For more information, visit www.onconetix.com.

Forward-Looking Statements

Certain statements in this press release are forward-looking within the meaning of the Private Securities Litigation Reform Act of 1995. These statements may be identified by the use of forward-looking words such as “anticipate,” “believe,” “forecast,” “estimate,” “expect,” and “intend,” among others. These forward-looking statements (including, without limitation, statements regarding the timing and effectiveness of the anticipated reverse split and compliance with applicable Nasdaq continued listing requirements) are based on Onconetix’s current expectations and actual results could differ materially. There are a number of factors that could cause actual events to differ materially from those indicated by such forward-looking statements. These factors include, but are not limited to, market and other conditions; whether the Company will be able to regain and maintain compliance with Nasdaq’s applicable listing criteria and the effect of a delisting from Nasdaq on the market for the Company’s securities; whether a definitive agreement for the proposed transaction with Ocuvex Therapeutics, Inc. (“Ocuvex”) and any related financing will be entered into; whether such transactions, or any other contemplated transaction, may be completed with different terms, in an untimely manner, or not at all; whether the Company will be able to realize the benefits of a proposed transaction with Ocuvex; Onconetix’s ability to integrate the assets and commercial operations contemplated to be acquired from Ocuvex into the Company’s business; risks related to Onconetix’s ability to commercialize or monetize Proclarix and integrate the assets and commercial operations; risks related to the Company’s present need for capital to commercially launch Proclarix and have adequate working capital; risks related to Onconetix’s ability to attract, hire and retain skilled personnel necessary to commercialize and operate the Company’s commercial products; the failure to obtain and maintain the necessary regulatory approvals to market and commercialize Onconetix’s products; risks related to the Company’s ability to obtain and maintain intellectual property protection for its current products; and the Company’s reliance on third parties, including manufacturers and logistics companies. As with any commercial-stage pharmaceutical product or any product candidate under clinical development, there are significant risks in the development, regulatory approval and commercialization of biotechnology products. Onconetix does not undertake an obligation to update or revise any forward-looking statement. Investors should read the risk factors set forth in Onconetix’s Annual Report on Form 10-K, filed with the SEC on June 2, 2025 and periodic reports filed with the SEC on or after the date thereof. All of Onconetix’s forward-looking statements are expressly qualified by all such risk factors and other cautionary statements. The information set forth herein speaks only as of the date thereof. 

For more information:

Onconetix, Inc.
201 E. Fifth Street, Suite 1900

Cincinnati, OH 45202

Phone: (513) 620-4101

Investor Contact Information:

Onconetix Investor Relations
Email: investors@onconetix.com