Cellectar Biosciences, Inc.

S-11 tm2529020d1_s1.htm FORM S-1

As filed with the Securities and Exchange Commission on October 20, 2025

Registration No. 333-

UNITED STATES SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM S-1

REGISTRATION STATEMENT UNDER THE SECURITIES ACT OF 1933

CELLECTAR BIOSCIENCES, INC.

(Exact name of registrant as specified in its charter)

100 Campus Drive, Florham Park, New Jersey 07932

Telephone (608) 441-8120

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

James V. Caruso**

President and Chief Executive Officer

Cellectar Biosciences, Inc.

100 Campus Drive, Florham Park, New Jersey 07932

Telephone (608) 441-8120

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

With copies to:

Asher M. Rubin, Esq. Istvan Hajdu, Esq. Nick D. DeAngelis, Esq. Sidley Austin LLP 787 Seventh Avenue New York, New York 10019 Telephone (212) 839-5300

From time to time after the effectiveness of this registration statement.

As soon as practicable after this Registration Statement is declared 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. x

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 the Securities Act.¨

This registration statement shall hereafter become effective in accordance with the provisions of Section 8(a) of the Securities Act of 1933.

The information in this prospectus is not complete and may be changed. The selling stockholders named in this prospectus may not sell these securities or accept an offer to buy these securities until the registration statement filed with the Securities and Exchange Commission is effective. This prospectus is not an offer to sell these securities and the selling stockholders named in this prospectus are not soliciting an offer to buy these securities in any state or jurisdiction where such offer or sale is not permitted.

**Subject to Completion

Dated October 20, 2025

PROSPECTUS

Up to 2,096,188 Shares of Common Stock Offered by the Selling Stockholders

CELLECTAR BIOSCIENCES, INC.

Common Stock

This prospectus relates to the resale, from time to time by the selling stockholders named in this prospectus (the “selling stockholders”), of up to 2,096,188 shares of our common stock (the “Shares”) issuable upon exercise of common stock purchase warrants (the “Inducement Warrants”) issued to the selling stockholders in a warrant inducement transaction (the “Warrant Inducement”) which closed on October 8, 2025. For additional information about the transaction, see “Summary-Description of the Warrant Inducement.”

Our registration of the shares of common stock covered by this prospectus does not mean that the selling stockholders will offer or sell any such shares. We are registering the offer and resale of the Shares to fulfill our contractual obligations set forth in the Inducement Letters (as defined below) entered into on October 7, 2025.

We will not receive any of the proceeds from the sale of our Shares by the selling stockholders, although we will receive proceeds from the cash exercise of any Inducement Warrants.

Any shares of our common stock subject to resale hereunder will have been issued by us and received by the selling stockholders prior to any resale of such shares pursuant to this prospectus.

The selling stockholders, or their donees, pledgees, transferees or other successors-in-interest may offer or resell the Shares from time to time through public or private transactions at prevailing market prices, at prices related to prevailing market prices or at privately negotiated prices. The selling stockholders will bear all commissions and discounts and similar selling expenses, if any, attributable to the sale of Shares. We will bear all costs, expenses and fees (other than commissions and discounts and similar selling expenses) in connection with the registration of the Shares. For additional information on the methods of sale that may be used by the selling stockholders, see “Plan of Distribution” beginning on page 42 of this prospectus.

Our common stock is listed on the Nasdaq Capital Market under the symbol “CLRB.” On October 17, 2025, the last reported sale price of our common stock was $4.50.

Investing in our securities involves significant risks. We strongly recommend that you read carefully the risks we describe in “Risk Factors” beginning on page 9 of this prospectus and in any accompanying prospectus supplement, as well as the risk factors that are incorporated by reference into this prospectus from our filings made with the Securities and Exchange Commission, before investing in our securities.

Neither the Securities and Exchange Commission nor any state securities commission has approved or disapproved of these securities or passed upon the adequacy or accuracy of this prospectus. Any representation to the contrary is a criminal offense.

The date of this prospectus is , 2025.

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