# EDGAR Filing Document

**Accession Number:** 0001782107
**File Stem:** 0001213900-26-053255
**Filing Date:** 2026-5
**Character Count:** 29468
**Document Hash:** d818e0550738154b9e5f754637e98480
**Contains OCR:** False
**Source Format:** 

## Filing Content

## Filing Summary
**0001213900-26-053255.hdr.sgml**: 20260507

**ACCESSION NUMBER**: 0001213900-26-053255

**CONFORMED SUBMISSION TYPE**: S-1/A

**PUBLIC DOCUMENT COUNT**: 3

**FILED AS OF DATE**: 20260507

**DATE AS OF CHANGE**: 20260507

**FILER**: 

**COMPANY DATA:**
- **COMPANY CONFORMED NAME:** Onconetix, Inc.
- **CENTRAL INDEX KEY:** 0001782107
- **STANDARD INDUSTRIAL CLASSIFICATION:** PHARMACEUTICAL PREPARATIONS [2834]
- **ORGANIZATION NAME:** 03 Life Sciences
- **EIN:** 000000000
- **STATE OF INCORPORATION:** DE
- **FISCAL YEAR END:** 1231

**FILING VALUES:**
- **FORM TYPE:** S-1/A
- **SEC ACT:** 1933 Act
- **SEC FILE NUMBER:** 333-295376
- **FILM NUMBER:** 26952648

**BUSINESS ADDRESS:**
- **STREET 1:** 201 E. FIFTH STREET
- **STREET 2:** SUITE 1900
- **CITY:** CINCINNATI
- **STATE:** OH
- **ZIP:** 45202
- **BUSINESS PHONE:** 513-620-4101

**MAIL ADDRESS:**
- **STREET 1:** 201 E. FIFTH STREET
- **STREET 2:** SUITE 1900
- **CITY:** CINCINNATI
- **STATE:** OH
- **ZIP:** 45202

**FORMER COMPANY:**
- **FORMER CONFORMED NAME:** Blue Water Biotech, Inc.
- **DATE OF NAME CHANGE:** 20230424

**FORMER COMPANY:**
- **FORMER CONFORMED NAME:** Blue Water Vaccines Inc.
- **DATE OF NAME CHANGE:** 20190710

**As filed with the Securities and Exchange Commission on May 7, 2026**

**Registration No. 333-295376**

**UNITED STATES**

**SECURITIES AND EXCHANGE COMMISSION<br> Washington, D.C. 20549**

**Amendment No. 1**

**to**

**FORM S-1**

**REGISTRATION STATEMENT UNDER THE SECURITIES ACT OF 1933**

**Onconetix, Inc.**

(Exact Name of Registrant as Specified in its Charter)

---

| | | |
|:---|:---|:---|
| **Delaware** | **2834** | **83-2262816** |
| (State or other jurisdiction of<br> incorporation or organization) | (Primary Standard Industrial <br> Classification Code Number) | (I.R.S. Employer <br> Identification No.) |

---

**201 E. Fifth Street, Suite 1900<br> Cincinnati, Ohio 45202<br> Telephone: (513) 620-4101**<br> (Address, Including Zip Code, and Telephone Number, Including Area Code, of Registrant's Principal Executive Offices)

**David A. White<br> Chief Executive Officer** 

**201 E. Fifth Street, Suite 1900<br> Cincinnati, Ohio 45202<br> Telephone: (513) 620-4101**<br> (Name, Address, Including Zip Code, and Telephone Number, Including Area Code, of Agent for Service)

**with copies to:**

**Barry I. Grossman, Esq.<br> Jessica Yuan, Esq.<br> Ellenoff Grossman & Schole LLP<br> 1345 Avenue of the Americas<br> New York, NY 10105<br> Phone: (212) 370-1300<br> Fax: (212) 370-7889**

**Approximate date of commencement of proposed sale to the public:** From time to time after this registration statement becomes effective.

If any of the securities being registered on this Form are to be offered on a delayed or continuous basis pursuant to Rule 415 under the Securities Act of 1933, check the following box. ☒

If this Form is filed to register additional securities for an offering pursuant to Rule 462(b) under the Securities Act, please check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering. ☐

If this Form is a post-effective amendment filed pursuant to Rule 462(c) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering. ☐

If this Form is a post-effective amendment filed pursuant to Rule 462(d) under the Securities Act, check the following box and list the Securities Act registration statement number of the earlier effective registration statement for the same offering. ☐

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, a smaller reporting company, or an emerging growth company. See the definitions of "large accelerated filer," "accelerated filer," "smaller reporting company," and "emerging growth company" in Rule 12b-2 of the Exchange Act.

Large accelerated filer ☐ Accelerated filer ☐ <br> Non-accelerated filer ☒ Smaller reporting company ☒ <br> Emerging growth company ☒

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 7(a)(2)(B) of the Securities Act. ☐

**The Registrant hereby amends this Registration Statement on such date or dates as may be necessary to delay its effective date until the Registrant shall file a further amendment which specifically states that this Registration Statement shall thereafter become effective in accordance with Section 8(a) of the Securities Act of 1933, as amended, or until the Registration Statement shall become effective on such date as the Securities and Exchange Commission acting pursuant to said Section 8(a), may determine.**

**EXPLANATORY NOTE**

Onconetix, Inc. is filing this Amendment No. 1 (this "Amendment") to its Registration Statement on Form S-1 (File No. 333-295376) (the "Registration Statement") as an exhibit-only filing to file Exhibit 5.1. Accordingly, this Amendment consists only of the facing page, this explanatory note, Item 16(a) of Part II of the Registration Statement, the signature page to the Registration Statement and the filed exhibit. The remainder of the Registration Statement is unchanged and has been omitted.

**PART II<br> INFORMATION NOT REQUIRED IN PROSPECTUS**

**Item 16. Exhibits and Financial Statement Schedules.**

---

| | | | | |
|:---|:---|:---|:---|:---|
| | | **Incorporated by Reference** | **Incorporated by Reference** | **Incorporated by Reference** |
| <br>**Exhibit No.** | <br>**Description** | **Form** | **Exhibit** | **Filing Date** |
| 2.1 | [Share Exchange Agreement, dated February 11, 2026, by and among Onconetix, Inc., Realbotix, LLC, Realbotix Corp, and Simulacra Corporation.†](https://www.sec.gov/Archives/edgar/data/1782107/000121390026015212/ea027670401ex2-1_onconetix.htm) | 8-K | 2.1 | February 12, 2026 |
| 3.1 | [Amended and Restated Certificate of Incorporation filed with Delaware Secretary of State dated February 23, 2022.](https://www.sec.gov/Archives/edgar/data/1782107/000121390022009250/ea156152ex3-1_bluewater.htm) | 8-K | 3.1 | February 24, 2022 |
| 3.2 | [Certificate of Amendment to the Company's Second Amended and Restated Certificate of Incorporation dated April 21, 2023](https://www.sec.gov/Archives/edgar/data/1782107/000121390023031827/ea177344ex3-1_bluewater.htm) | 8-K | 3.1 | April 24, 2023 |
| 3.3 | [Certificate of Amendment to the Company's Second Amended and Restated Certificate of Incorporation dated December 15, 2023.](http://www.sec.gov/Archives/edgar/data/1782107/000121390023097738/ea190395ex3-1_onconetix.htm) | 8-K | 3.1 | December 21, 2023 |
| 3.4 | [Fourth Amended and Restated Bylaws of the Company dated December 1 2023](https://www.sec.gov/Archives/edgar/data/1782107/000121390023097738/ea190395ex3-2_onconetix.htm) | 8-K | 3.2 | December 21, 2023 |
| 3.5 | [Certificate of Amendment to the Amended and Restated Certificate of Incorporation, as amended, of Onconetix, Inc. dated September 24, 2024.](http://www.sec.gov/Archives/edgar/data/1782107/000121390024081482/ea021556001ex3-1_onconetix.htm) | 8-K | 3.1 | September 24, 2024 |
| 3.6 | [Form of Certificate of Amendment to the Amended and Restated Certificate of Incorporation, as amended, of Onconetix, Inc., dated June 11, 2025](https://www.sec.gov/Archives/edgar/data/1782107/000121390025053367/ea024538701ex3-1_onconetix.htm) | 8-K | 3.1 | June 11, 2025 |
| 3.7 | [Certificate of Amendment to the Amended and Restated Certificate of Incorporation, as amended, of Onconetix, Inc. dated March 25, 2026](https://www.sec.gov/Archives/edgar/data/1782107/000121390026034902/ea028356901ex3-1.htm) | 8-K | 3.1 | March 27, 2026 |
| 4.1 | [Specimen Common Stock Certificate.](https://www.sec.gov/Archives/edgar/data/1782107/000121390021056861/fs12021a1ex4-1_bluewater.htm) | S-1 | 4.1 | October 8, 2021 |
| 4.2 | [Description of Registered Securities.](http://www.sec.gov/Archives/edgar/data/1782107/000121390024032225/ea020170101ex4-2_onconetix.htm) | 10-K | 4.2 | April 11, 2024 |
| 4.3 | [Form of Inducement PIO.](http://www.sec.gov/Archives/edgar/data/1782107/000121390024060635/ea020927701ex4-1_onconetix.htm) | 8-K | 4.1 | July 11, 2024 |
| 4.4 | [Form of Warrant.(Series C)](http://www.sec.gov/Archives/edgar/data/1782107/000121390024084866/ea021664901ex4-1_onconetix.htm) | 8-K | 4.1 | October 3, 2024 |
| 4.5 | [Form of Warrant.(Series D)](https://www.sec.gov/Archives/edgar/data/1782107/000121390025091966/ea025883001ex4-1_onconetix.htm) | 8-K | 4.1 | September 26, 2025 |
| 4.6 | [Form of Warrant.(Series E)](https://www.sec.gov/Archives/edgar/data/1782107/000121390025095847/ea025986001ex4-1_onconetix.htm) | 8-K | 4.1 | October 3, 2025 |
| 4.7 | [Certification of Designation of Series C Preferred Stock.](http://www.sec.gov/Archives/edgar/data/1782107/000121390024084866/ea021664901ex3-1_onconetix.htm) | 8-K | 3.1 | October 3, 2024 |
| 4.8 | [Certification of Designation of Series D Preferred Stock.](https://www.sec.gov/Archives/edgar/data/1782107/000121390025091966/ea025883001ex3-1_onconetix.htm) | 8-K | 3.1 | September 26, 2025 |
| 4.9 | [Certification of Designation of Series E Preferred Stock.](https://www.sec.gov/Archives/edgar/data/1782107/000121390025095847/ea025986001ex3-1_onconetix.htm) | 8-K | 3.1 | October 3, 2025 |
| 5.1\*\* | [Opinion of Ellenoff Grossman & Schole LLP as to the legality of the securities being registered.](ea028969801ex5-1.htm) |  |  |  |
| 10.1 | [2019 Equity Incentive Plan.](http://www.sec.gov/Archives/edgar/data/1782107/000121390021052037/fs12021ex10-1_bluewater.htm) | S-1 | 10.1 | October 8, 2021 |
| 10.2 | [2022 Equity Incentive Plan.](https://www.sec.gov/Archives/edgar/data/1782107/000121390022000991/fs12022a5ex10-2_bluewater.htm) | S-1/A | 10.2 | January 6, 2022 |
| 10.3 | [2019 Equity Incentive Plan Form of Stock Option Grant Agreement.](http://www.sec.gov/Archives/edgar/data/1782107/000121390021052037/fs12021ex10-3_bluewater.htm) | S-1 | 10.3 | October 8, 2021 |
| 10.4 | [2022 Equity Incentive Plan Form of Incentive Stock Option Agreement (Employee).](http://www.sec.gov/Archives/edgar/data/1782107/000121390022000991/fs12022a5ex10-4_bluewater.htm) | S-1/A | 10.4 | January 6, 2022 |
| 10.5 | [2022 Equity Incentive Plan Form of Nonstatutory Stock Option Agreement (Consultant).](http://www.sec.gov/Archives/edgar/data/1782107/000121390022000991/fs12022a5ex10-5_bluewater.htm) | S-1/A | 10.5 | January 6, 2022 |
| 10.6 | [2022 Equity Incentive Plan Form of Nonstatutory Stock Option Agreement (Non-Employee Director).](http://www.sec.gov/Archives/edgar/data/1782107/000121390022000991/fs12022a5ex10-6_bluewater.htm) | S-1/A | 10.6 | January 6, 2022 |
| 10.7 | [2022 Equity Incentive Plan Form of Nonstatutory Stock Option Agreement (Employee).](http://www.sec.gov/Archives/edgar/data/1782107/000121390022000991/fs12022a5ex10-7_bluewater.htm) | S-1/A | 10.7 | January 6, 2022 |
| 10.8 | [Lease Agreement, dated as of April 29, 2021, between the Registrant and Regus Management Group, LLC.](http://www.sec.gov/Archives/edgar/data/1782107/000121390021052037/fs12021ex10-11_bluewater.htm) | S-1 | 10.11 | October 8, 2021 |
| 10.9 | [General Release of Claims, dated October 5, 2023, by and between Jon Garfield and the Company.](http://www.sec.gov/Archives/edgar/data/1782107/000121390023081324/ea186383ex99-1_bluewater.htm) | 8-K | 99.1 | October 10, 2023 |
| 10.10 | [Release, dated January 10, 2024, by and between the Company and Dr. Neil Campbell.](http://www.sec.gov/Archives/edgar/data/1782107/000121390024003413/ea191591ex99-1_onconetix.htm) | 8-K | 99.1 | January 12, 2024 |
| 10.11 | [Form of Indemnification Agreement for Directors and Officers.](http://www.sec.gov/Archives/edgar/data/1782107/000121390023081324/ea186383ex10-3_bluewater.htm) | 8-K | 10.3 | October 10, 2023 |

---

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| | | | | |
|:---|:---|:---|:---|:---|
| 10.12 | [Form of Amendment, dated October 5, 2023, to Asset Purchase Agreement, dated June 13, 2023, by and among WraSer, Xspire, Legacy-Xspire Holdings, LLC, and the Company.](http://www.sec.gov/Archives/edgar/data/1782107/000101376223005521/f10q0623ex10-14_bluewater.htm) | 10-Q | 10.14 | October 20, 2023 |
| 10.13†# | [Exclusive Distribution Agreement, dated September 20, 2023, between the Company and Cardinal Health 105, LLC.](http://www.sec.gov/Archives/edgar/data/1782107/000121390023088387/f10q0923ex10-6_bluewater.htm) | 10-Q | 10.6 | November 17, 2023 |
| 10.14 | [Form of Lock-Up Agreement, dated December 15, 2023, by and among the Company and certain stockholders of Proteomedix.](http://www.sec.gov/Archives/edgar/data/1782107/000121390023097738/ea190395ex10-1_onconetix.htm) | 8-K | 10.1 | December 21, 2023 |
| 10.15 | [Form of Non-Competition and Non-Solicitation Agreement, dated December 15, 2023, by and among the Company and certain stockholders of Proteomedix.](http://www.sec.gov/Archives/edgar/data/1782107/000121390023097738/ea190395ex10-2_onconetix.htm) | 8-K | 10.2 | December 21, 2023 |
| 10.16 | [Form of Stockholder Support Agreement, dated December 15, 2023, by and among the Company, Proteomedix, and certain stockholders of Proteomedix](http://www.sec.gov/Archives/edgar/data/1782107/000121390023097738/ea190395ex10-3_onconetix.htm) | 8-K | 10.3 | December 21, 2023 |
| 10.17 | [Form of Subscription Agreement, dated December 15, 2023, by and among the Company, Proteomedix, and the PMX Investor.](http://www.sec.gov/Archives/edgar/data/1782107/000121390023097738/ea190395ex10-4_onconetix.htm) | 8-K | 10.4 | December 21, 2023 |
| 10.18 | [Separation Agreement, dated January 17, 2024, between the Company and Erin Henderson.](http://www.sec.gov/Archives/edgar/data/1782107/000121390024004855/ea191886ex10-1_onconetix.htm) | 8-K | 10.1 | January 19, 2024 |
| 10.19 | [Consulting Agreement, dated January 17, 2024, between the Company and The Aetos Group.](http://www.sec.gov/Archives/edgar/data/1782107/000121390024004855/ea191886ex10-2_onconetix.htm) | 8-K | 10.2 | January 19, 2024 |
| 10.20 | [Debenture, dated January 23, 2024 issued to the PMX Investor](http://www.sec.gov/Archives/edgar/data/1782107/000121390024007414/ea192391ex10-1_onconetix.htm) | 8-K | 10.1 | January 29, 2024 |
| 10.21 | [Consulting Agreement, dated January 4, 2024, by and between the Company and Thomas Meier.](http://www.sec.gov/Archives/edgar/data/1782107/000121390024012608/ea193470ex10-1_onconetix.htm) | 8-K | 10.1 | February 12, 2024 |
| 10.22 | [License Agreement, dated March 27, 2023, between Proteomedix and Laboratory Corporation of America Holdings.](http://www.sec.gov/Archives/edgar/data/1782107/000121390024032225/ea020170101ex10-55_onconetix.htm) | 10-K | 10.55 | April 11, 2024 |
| 10.23 | [Forbearance Agreement, dated April 24, 2024, by and between the Company and Veru Inc.](http://www.sec.gov/Archives/edgar/data/1782107/000121390024036645/ea020475101ex10-1_oncone.htm) | 8-K | 10.1 | April 26, 2024 |
| 10.24 | [Master Research Services Agreement, dated October 1, 2022, by and between Proteomedix AG and Immunovia, AB](http://www.sec.gov/Archives/edgar/data/1782107/000121390024049815/ea020378801ex10-60_onconetix.htm) | S-1/A | 10.6 | June 25, 2024 |
| 10.25 | [Collaboration Agreement, dated July 19, 2021, by and between Proteomedix AG and New Horizon Health Limited](http://www.sec.gov/Archives/edgar/data/1782107/000121390024049815/ea020378801ex10-61_onconetix.htm) | S-1/A | 10.61 | June 25, 2024 |
| 10.26 | [Amendment No. 1, dated June 26, 2023, to Collaboration Agreement, dated July 19, 2021, by and between Proteomedix AG and New Horizon Health Limited](http://www.sec.gov/Archives/edgar/data/1782107/000121390024049815/ea020378801ex10-62_onconetix.htm) | S-1/A | 10.62 | June 25, 2024 |
| 10.27 | [Release Agreement, dated June 10, 2024, between the Company and Bruce Harmon.](http://www.sec.gov/Archives/edgar/data/1782107/000121390024052469/ea020763501ex99-1_onconetix.htm) | 8-K | 99.1 | June 13, 2024 |
| 10.28 | [Consulting Agreement, dated June 10, 2024, between the Company and Karina Fedasz.](http://www.sec.gov/Archives/edgar/data/1782107/000121390024052976/ea020793301ex10-1_onconet.htm) | 8-K/A | 10.1 | June 14, 2024 |
| 10.29 | [Form of Inducement Letter](http://www.sec.gov/Archives/edgar/data/1782107/000121390024060635/ea020927701ex10-1_onconetix.htm) | 8-K | 10.1 | July 11, 2024 |
| 10.30 | [Amended and Restated Forbearance Agreement between the Company and Veru, dated September 19, 2024](http://www.sec.gov/Archives/edgar/data/1782107/000121390024080705/ea021526501ex10-1_onconetix.htm) | 8-K | 10.1 | September 20, 2024 |
| 10.31 | [Form of Securities Purchase Agreement dated October 2, 2024 relating to the sale of the Series C Preferred Stock and Warrants](http://www.sec.gov/Archives/edgar/data/1782107/000121390024084866/ea021664901ex10-1_onconetix.htm) | 8-K | 10.1 | October 3, 2024 |
| 10.32 | [Form of Registration Rights Agreement dated as of October 2, 2024 relating to the resale of the shares of Common Stock underlying the Series C Preferred Stock and Warrants](http://www.sec.gov/Archives/edgar/data/1782107/000121390024084866/ea021664901ex10-2_onconetix.htm) | 8-K | 10.2 | October 3, 2024 |
| 10.33 | [ELOC Purchase Agreement dated October 2, 2024](https://www.sec.gov/Archives/edgar/data/1782107/000121390024107952/ea022447701ex10-45_onconetix.htm) | S-1 | 10.45 | December 11, 2024 |
| 10.34 | [ELOC Registration Rights Agreement dated October 2, 2024](https://www.sec.gov/Archives/edgar/data/1782107/000121390024107952/ea022447701ex10-46_onconetix.htm) | S-1 | 10.46 | December 11, 2024 |
| 10.35 | [Waiver and Amendment No. 1 to Forbearance Agreement, dated November 26, 2024, between the Company and Veru](http://www.sec.gov/Archives/edgar/data/1782107/000121390024105072/ea022349001ex10-1_onconetix.htm) | 8-K | 10.1 | December 3, 2024 |
| 10.36 | [Settlement Agreement and Release, dated September 22, 2025, by and between the Company and Veru, Inc.](https://www.sec.gov/Archives/edgar/data/1782107/000121390025091966/ea025883001ex10-3_onconetix.htm) | 8-K | 10.3 | September 26, 2025 |
| 10.37 | [Form of Termination Agreement effective as of September 24, 2025, by and between the Company and Ocuvex Therapeutics, Inc.](https://www.sec.gov/Archives/edgar/data/1782107/000121390025091966/ea025883001ex10-4_onconetix.htm) | 8-K | 10.4 | September 26, 2025 |
| 10.38 | [Note, dated February 12, 2025](https://www.sec.gov/Archives/edgar/data/1782107/000121390025014928/ea023134501ex10-1_onconetix.htm) | 8-K | 10.1 | February 18, 2025 |
| 10.39 | [Consulting Agreement, dated February 28, 2025, between the Company and James Sapirstein](https://www.sec.gov/Archives/edgar/data/1782107/000121390025018867/ea023257201ex99-1_onconetix.htm) | 8-K | 99.1 | February 28, 2025 |
| 10.40 | [Note, dated May 16, 2025](https://www.sec.gov/Archives/edgar/data/1782107/000121390025046909/ea024328701ex10-1_onconetix.htm) | 8-K | 10.1 | May 22, 2025 |

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| | | | | |
|:---|:---|:---|:---|:---|
| 10.41 | [Note, dated June 5, 2025](https://www.sec.gov/Archives/edgar/data/1782107/000121390025053367/ea024538701ex10-1_onconetix.htm) | 8-K | 10.1 | June 11, 2025 |
| 10.42 | [Form of Company Support Agreement, dated July 16, 2025, by and among Parent, the Company and certain Company stockholders.](https://www.sec.gov/Archives/edgar/data/1782107/000121390025064469/ea024881501ex10-2_oncone.htm) | 8-K | 10.2 | July 16, 2025 |
| 10.43 | [Form of Conversion Price Reduction Consent](https://www.sec.gov/Archives/edgar/data/1782107/000121390025064469/ea024881501ex10-3_oncone.htm) | 8-K | 10.3 | July 16, 2025 |
| 10.44 | [Promissory Note, dated August 6, 2025, by and between Keystone Capital Partners, LLC and the Company](https://www.sec.gov/Archives/edgar/data/1782107/000121390025074952/ea025275901ex10-1_oncone.htm) | 8-K | 10.1 | August 12, 2025 |
| 10.45 | [Amended and Restated Promissory Note, dated August 7, 2025, by and between Veru, Inc. and the Company](https://www.sec.gov/Archives/edgar/data/1782107/000121390025074952/ea025275901ex10-2_oncone.htm) | 8-K | 10.2 | August 12, 2025 |
| 10.46 | [Promissory Note, dated August 28, 2025, by and between Keystone Capital Partners, LLC and the Company](https://www.sec.gov/Archives/edgar/data/1782107/000121390025084500/ea025595801ex10-1_onconetix.htm) | 8-K | 10.1 | September 4, 2025 |
| 10.47 | [Promissory Note, dated August 28, 2025, by and between KCP Fund I, LLC and the Company](https://www.sec.gov/Archives/edgar/data/1782107/000121390025084500/ea025595801ex10-2_onconetix.htm) | 8-K | 10.2 | September 4, 2025 |
| 10.48 | [Second Amended and Restated Promissory Note, dated August 28, 2025, by and between Veru, Inc. and the Company](https://www.sec.gov/Archives/edgar/data/1782107/000121390025084500/ea025595801ex10-3_onconetix.htm) | 8-K | 10.3 | September 4, 2025 |
| 10.49 | [Waiver, dated August 28, 2025, by and between Veru, Inc. and the Company](https://www.sec.gov/Archives/edgar/data/1782107/000121390025084500/ea025595801ex10-4_onconetix.htm) | 8-K | 10.4 | September 4, 2025 |
| 10.50 | [License Agreement, dated September 17, 2025, by and between Immunovia AB and Proteomedix AG](https://www.sec.gov/Archives/edgar/data/1782107/000121390025089845/ea025819601ex10-1_onconetix.htm) | 8-K | 10.1 | September 22, 2025 |
| 10.51 | [Form of Securities Purchase Agreement dated September 22, 2025 relating to the sale of the Series D Preferred Stock and Warrants](https://www.sec.gov/Archives/edgar/data/1782107/000121390025091966/ea025883001ex10-1_onconetix.htm) | 8-K | 10.1 | September 26, 2025 |
| 10.52 | [Form of Registration Rights Agreement dated as of September 22, 2025 relating to the resale of the shares of Common Stock underlying the Series D Preferred Stock and Warrants](https://www.sec.gov/Archives/edgar/data/1782107/000121390025091966/ea025883001ex10-2_onconetix.htm) | 8-K | 10.2 | September 26, 2025 |
| 10.53 | [Form of Securities Purchase Agreement dated October 1, 2025 relating to the sale of the Series E Preferred Stock and Warrants](https://www.sec.gov/Archives/edgar/data/1782107/000121390025095847/ea025986001ex10-1_onconetix.htm) | 8-K | 10.1 | October 3, 2025 |
| 10.54 | [Form of Registration Rights Agreement dated as of October 1, 2025 relating to the resale of the shares of Common Stock underlying the Series E Preferred Stock and Warrants](https://www.sec.gov/Archives/edgar/data/1782107/000121390025095847/ea025986001ex10-2_onconetix.htm) | 8-K | 10.2 | October 3, 2025 |
| 10.55 | [First Amendment to License Agreement between Proteomedix AG and Laboratory Corporation of America Holdings, dated December 6, 2025#](http://www.sec.gov/Archives/edgar/data/1782107/000121390025119898/ea026905201ex10-1_onconetix.htm) | 8-K | 10.1 | December 10, 2025 |
| 10.56# | [Employment Agreement, dated March 18, 2026, between the Company and Mr. David White#](http://www.sec.gov/Archives/edgar/data/1782107/000121390026034054/ea028333701ex10-1.htm)<br>| 8-K | 10.1 | March 25, 2026 |
| 21 | [List of Subsidiaries.](https://www.sec.gov/Archives/edgar/data/1782107/000121390026027725/ea028054701ex21.htm) | 10-K | 21.0 | March 13, 2026 |
| 23.1\* | [Consent of MaloneBailey LLP](https://www.sec.gov/Archives/edgar/data/1782107/000121390026048535/ea028790401ex23-1.htm) |  |  |  |
| 23.2\*\* | [Consent of Ellenoff Grossman & Schole (included as part of Exhibit 5.1 hereto).](ea028969801ex5-1.htm) |  |  |  |
| 24\* | [Power of Attorney](https://www.sec.gov/Archives/edgar/data/1782107/000121390026048535/ea0287904-s1_onconetix.htm#a_011) |  |  |  |
| 107\* | [Filing Fee Table.](https://www.sec.gov/Archives/edgar/data/1782107/000121390026048535/ea028790401ex-fee.htm) | S-1 | 107.0 | April 28, 2026 |

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\* Previously filed.

\*\* Filed herewith.

† Certain of the exhibits and schedules to this Exhibit have been omitted in accordance with Regulation S-K Item 601(a)(5). The Company agrees to furnish a copy of all omitted exhibits and schedules to the SEC upon its request.

# Certain portions of this exhibit (indicated by "[\*]" have been omitted pursuant to Item 601(b)(10)(iv) of Regulation S-K as we have determined they (1) are not material and (2) are the type that the Company treats as private or confidential. The Registrant hereby agrees to furnish a copy of any omitted portion to the SEC upon request.

**SIGNATURES**

Pursuant to the requirements of the Securities Act of 1933, as amended, the Registrant certifies that it has duly caused this Registration Statement to be signed on its behalf by the undersigned, thereunto duly authorized, in the City of Cincinnati, Ohio, on May 7, 2026.

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| | |
|:---|:---|
| **ONCONETIX, INC.** | **ONCONETIX, INC.** |
| By: | /s/ David A. White |
| Name: | David A. White |
| Title: | Chief Executive Officer |

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Pursuant to the requirements of the Securities Act of 1933, as amended, this Registration Statement has been signed by the following persons in the capacities and on the dates indicated.

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| | | |
|:---|:---|:---|
| **Signature** | **Title** | **Date** |
| /s/ David A. White | Chief Executive Officer | May 7, 2026 |
| David A. White | (Principal Executive Officer) |  |
| \* | Interim Chief Financial Officer | May 7, 2026 |
| Karina M. Fedasz | (Principal Financial and Accounting Officer) |  |
| \* | Chairman of the Board and Director | May 7, 2026 |
| Sammy Dorf |  |  |
| \* | Director | May 7, 2026 |
| Sarah Romano |  |  |
| \* | Director | May 7, 2026 |
| Josh Epstein |  |  |

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Pursuant to Power of Attorney

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| | |
|:---|:---|
| By: | /s/ David A. White |
|  | David A. White |
|  | Attorney-in-Fact |

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## Exhibit 5.1

**Exhibit 5.1**

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| | |
|:---|:---|
| ![](ea028969801_ex5-1img1.jpg) | 1345 AVENUE OF THE AMERICAS, 11<sup>th</sup> FLOOR<br> NEW YORK, NEW YORK 10017<br> TELEPHONE: (212) 370-1300<br> FACSIMILE: (212) 370-7889<br> www.egsllp.com |

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May 7, 2026

Onconetix, Inc.

201 E. Fifth Street, Suite 1900

Cincinnati, OH 45202

Re: <u>Registration Statement on Form S-1</u>

Ladies and Gentlemen:

We have acted as counsel to Onconetix, Inc., a Delaware corporation (the "Company"), in connection with the filing by the Company of a Registration Statement on Form S-1 (the "Registration Statement") with the Securities and Exchange Commission, including a related prospectus filed with the Registration Statement (the "Prospectus"), covering the resale of up to 25,000,000 shares (the "Shares") of common stock of the Company, par value $0.00001 per share (the "Common Stock"), by Keystone Capital Partners, LLC.

We have examined the Registration Statement, the Prospectus, the Amended and Restated Certificate of Incorporation, Fourth Amended and Restated Bylaws, the Certificate of Designations of Series C Preferred Shares, and the Certificate of Designations of Series D Preferred, each as currently in effect as of the date hereof, and such documents and considered such legal matters as we have deemed necessary and relevant as the basis for the opinion set forth below. With respect to such examination, we have assumed the genuineness of all signatures, the authenticity of all documents submitted to us as originals, the conformity to original documents of all documents submitted to us as reproduced or certified copies, and the authenticity of the originals of those latter documents. As to questions of fact material to this opinion, we have, to the extent deemed appropriate, relied upon certain representations of certain officers and employees of the Company.

The opinions expressed herein are limited solely to the General Corporation Law of the State of Delaware, including the applicable provisions of the Delaware Constitution and the reported judicial decisions interpreting such law, as currently in effect, and we express no opinion as to the effect of any other law of the State of Delaware or the laws of any other jurisdiction. Our opinion is based on these laws as in effect on the date hereof and as of the effective date of the Registration Statement, and we assume no obligation to revise or supplement this opinion after the effective date of the Registration Statement should the law be changed by legislative action, judicial decision, or otherwise. We express no opinion as to whether the laws of any other jurisdiction are applicable to the subject matter hereof. We are not rendering any opinion as to compliance with any other federal or state law, rule or regulation relating to securities, or to the sale or issuance thereof.

Based upon the foregoing, we are of the opinion that the Shares, when sold and issued against payment therefor in accordance with the Registration Statement and the Prospectus, will be validly issued, fully paid and non-assessable

We hereby consent to the filing of this opinion as Exhibit 5.1 to the Registration Statement and to the reference to our firm under the caption "Legal Matters" in the prospectus constituting a part of the Registration Statement. In giving this consent, we do not hereby admit that we are in the category of persons whose consent is required under Section 7 of the Securities Act, or the rules and regulations promulgated thereunder.

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| |
|:---|
| Very truly yours, |
| /s/ Ellenoff Grossman & Schole LLP |
| Ellenoff Grossman & Schole LLP |

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