Estrella Immunopharma, Inc.

As filed with the U.S. Securities and Exchange Commission on December 22, 2025

Registration No.

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORMS-1

REGISTRATION STATEMENT

UNDER

THE SECURITIES ACT OF 1933

(Exact Name of Registrant as Specified in its Charter)

5858 Horton Street, Suite 370

Emeryville, California, 94608

Telephone: (510) 318-9098

(Address, Including Zip Code, and Telephone Number, Including Area Code, of Registrant’s Principal Executive Offices)

Cheng Liu

Chief Executive Officer

5858 Horton Street, Suite 370

Emeryville, California, 94608

Telephone: (510) 318-9098

(Name, Address, Including Zip Code, and Telephone Number, Including Area Code, of Agent for Service)

Copies to:

Michael J. Blankenship

Winston & Strawn LLP

800 Capitol Street, Suite 2400

Houston, TX 77002-2925

Telephone: (713) 651-2600

Approximate date of commencement of proposed sale to public:

From time to time after the effective date hereof.

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, 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.

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 Commission, acting pursuant to Section 8(a), may determine.

The information contained in this preliminary prospectus is not complete and may be changed. These securities may not be sold until the registration statement filed with the Securities and Exchange Commission is effective. This preliminary prospectus is not an offer to sell these securities and it is not soliciting an offer to buy these securities in any state where the offer or sale is not permitted.

Up to 2,541,206 Shares of Common Stock

This prospectus relates to the offer and resale from time to time by the selling stockholders named in this prospectus (the “Selling Stockholders”) of up to 2,541,206 shares of our Common Stock. This amount includes (i) shares issued to certain Selling Stockholders in private placements and (ii) up to an aggregate of 735,857 additional shares of Common Stock that may be issuable to certain Selling Stockholders pursuant to contingent “true-up” provisions in the May-June 2025 and September 2025 subscription agreements, in each case subject to the terms and conditions of those agreements.

The shares being registered for resale by this prospectus represent approximately 6.7% of our total outstanding shares of Common Stock as of December 1, 2025. We provide more information about how the Selling Stockholders may sell the shares of Common Stock in the section titled “Plan of Distribution.”

Estrella’s Common Stock is traded on the Nasdaq Capital Market (“Nasdaq”) under the symbol “ESLA.” On December 19, 2025, the closing price of our Common Stock was $1.69 per share.

We are an “emerging growth company” as defined under the federal securities laws and, as such, have elected to comply with certain reduced public company reporting requirements.

We are a “controlled company” within the meaning of the corporate governance rules of the Nasdaq Capital Market. Eureka Therapeutics, Inc., is our controlling shareholder. As of December 1, 2025, Eureka Therapeutics, Inc. holds approximately 66.9% of the outstanding Common Stock and approximately 66.9% of the total voting power of the Company. See the section titled “Management of Estrella — Controlled Company.” Investing in our Common Stock is highly speculative and involves a high degree of risk. See “Risk Factors” beginning on page 5.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or determined if this prospectus is truthful or complete. Any representation to the contrary is a criminal offense.

The date of this prospectus is , 2025