Bambusa Therapeutics, Inc.

S-11 bambusa-sx1.htm S-1

As filed with the Securities and Exchange Commission on October 9, 2026.

Registration No. 333-

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM S-1

REGISTRATION STATEMENT

UNDER

THE SECURITIES ACT OF 1933

Bambusa Therapeutics, Inc.

(Exact name of registrant as specified in its charter)

22 Boston Wharf Road, Floor 7

Boston, Massachusetts 02210

(617) 848-6188

(Address, including zip code, and telephone number, including area code, of registrant’s principal executive offices)

Shanshan Xu, M.D., Ph.D., M.B.A.

Chief Executive Officer, President, and Chairperson

22 Boston Wharf Road, Floor 7

Boston, Massachusetts 02210

(617) 848-6188

(Name, address, including zip code, and telephone number, including area code, of agent for service)

Copies to:

Approximate date of commencement of proposed sale to the public: As soon as practicable 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.

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 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 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.

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 is not soliciting an offer to buy these securities in any jurisdiction where the offer or sale is not permitted.

Subject to Completion

Preliminary Prospectus Dated , 2026

PROSPECTUS

Shares

Common Stock

This is Bambusa Therapeutics, Inc.’s initial public offering. We are selling shares of our common stock.

We expect the public offering price to be between $ and $ per share. Prior to this offering, there has been no public market for our common stock. We have applied to list our common stock on the Nasdaq Global Select Market (“Nasdaq”) under the symbol “BBTX.” The closing of this offering is contingent upon such listing.

We are an “emerging growth company” and a “smaller reporting company” as defined under the federal securities laws and, as such, have elected to comply with certain reduced public company reporting requirements in this prospectus and may elect to do so in future filings. See “Prospectus Summary—Implications of Being an Emerging Growth Company and a Smaller Reporting Company.”

Investing in our common stock involves risks that are described in the section titled “Risk Factors” beginning on page 15 of this prospectus.

(1)See the section titled “Underwriting” for additional information on underwriting compensation.

At our request, the underwriters have reserved up to % of the shares of common stock offered by this prospectus for sale, at the initial public offering price, to certain persons associated with us. See the section titled “Underwriting—Reserved Share Program.”

The underwriters may also exercise their option to purchase up to additional shares from us, at the public offering price, less the underwriting discount, for 30 days after the date of this prospectus.

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

The shares will be ready for delivery on or about , 2026.

The date of this prospectus is , 2026

TABLE OF CONTENTS

Neither we nor any of the underwriters have authorized anyone to provide you with information that is different than the information contained in this prospectus and any free writing prospectus prepared by or on behalf of us or to which we have referred you. Neither we nor the underwriters take any responsibility for, and cannot provide any assurance as to the reliability of, any other information that others may give you. The information contained in this prospectus or in any applicable free writing prospectus is accurate only as of the date of this prospectus or such free writing prospectus, as applicable, regardless of the time of delivery of this prospectus or any such free writing prospectus or of any sale of the securities offered hereby. Our business, operating results, financial condition, and prospects may have changed since that date.

This prospectus is an offer to sell only the securities offered hereby and only under circumstances and in jurisdictions where it is lawful to do so. Neither we nor any of the underwriters have taken any action that would permit this offering or possession or distribution of this prospectus in any jurisdiction where action for that purpose is required, other than in the United States. Persons who have come into possession of this prospectus in a jurisdiction outside the United States are required to inform themselves about and to observe any restrictions relating to this offering and the distribution of this prospectus.

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