SeaStar Medical Holding Corp

S-11 ea0287377-s1_seastar.htm REGISTRATION STATEMENT

REGISTRATION STATEMENT

As filed with the Securities and Exchange Commission on April 28, 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

SeaStar Medical Holding Corporation

(Exact Name of Registrant as Specified in Its Charter)

3513 Brighton Blvd, Suite 410

Denver, CO 80216

(844) 427-8100

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

Eric Schlorff

Chief Executive Officer

3513 Brighton Blvd, Suite 410

Denver, CO 80216

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

Copies to:

Joshua Erekson

Daniel Lyman

Dorsey & Whitney LLP

111 South Main Street, Suite 2100

Salt Lake City, UT 84111

(801) 933-7360

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

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, please 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 under the Securities Exchange Act of 1934:

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 is filing a combined prospectus in this Registration Statement pursuant to Rule 429 under the Securities Act in order to satisfy the requirements of the Securities Act and the rules and regulations thereunder for this offering and offering registered under the registrant’s Registration Statement on Form S-1 (File No. 333-287403) (the “May 2025 Registration Statement”), which was declared effective on May 27, 2025. The combined prospectus in this registration statement, upon effectiveness, shall act as Post-Effective Amendment No. 1 on Form S-1 to the May 2025 Registration Statement and contains an updated prospectus relating to the offering and sale of shares of the registrant’s common stock issued in its public offering consummated on May 27, 2025 that were registered under the May 2025 Registration Statement. Such Post-Effective Amendment No. 1 shall become effective concurrently with the effectiveness of this Registration Statement in accordance with Section 8(c) 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 or until the Registration Statement shall become effective on such date as the Commission, acting pursuant to said Section 8(a), may determine.

EXPLANATORY NOTE

Pursuant to Rule 429 under the Securities Act of 1933, as amended (the “Securities Act”), this prospectus forms a part of Registration Statement on Form S-1, which Registration Statement also constitutes Post-Effective Amendment No. 1 on Form S-1 to the registrant’s Registration Statement on Form S-1 (File No. 333-287403 (the “May 2025 Registration Statement”) relating to (i) the issuance by the registrant of up to an aggregate of 1,664,543 shares of common stock, par value $0.0001 per share (“Common Stock”), and is being filed to update and supplement the information contained in the May 2025 Registration Statement, as declared effective by the Securities and Exchange Commission on May 27, 2025. This Post-Effective Amendment No. 1 to the May 2025 Registration Statement shall hereafter become effective concurrently with the effectiveness of this Registration Statement in accordance with Section 8(c) of the Securities Act.

The information 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 nor does it seek an offer to buy these securities in any jurisdiction where the offer or sale is not permitted.

Up to 1,664,543 Shares

Common Stock

SeaStar Medical Holding Corporation

This prospectus relates to the resale, from time to time, of up to 1,664,543 shares of our Common Stock by Lincoln Park Capital Fund, LLC (“Lincoln Park” or the “selling stockholder”).

The shares of Common Stock being offered by the selling stockholder have been or may be purchased pursuant to the purchase agreement, dated April 25, 2025, that we entered into with Lincoln Park (the “Purchase Agreement”). See “The Lincoln Park Transaction” for a description of the Purchase Agreement and “Selling Stockholder” for additional information regarding Lincoln Park. The prices at which Lincoln Park may sell the shares will be determined by the prevailing market price for the shares or in negotiated transactions. We are not selling any securities under this prospectus and will not receive any of the proceeds from the sale of shares of Common Stock by the selling stockholder. We may receive up to $14,657,887.43 (in addition to the $342,112.57 previously received from sales made pursuant to the Purchase Agreement prior to the date of this prospectus) aggregate gross proceeds (subject to certain limitations) under the Purchase Agreement from any sales we make to Lincoln Park pursuant to the Purchase Agreement after the date of this prospectus. As of April 20, 2026, we have sold an aggregate of 138,184 shares of our common stock to Lincoln Park for gross proceeds of approximately $342,112.57 under the Purchase Agreement, which shares (together with the 23,641 Commitment Shares) were registered for resale by Lincoln Park under the May 2025 Registration Statement.

The selling stockholder may sell or otherwise dispose of the shares of Common Stock described in this prospectus in a number of different ways and at varying prices. See “Plan of Distribution” for more information about how the selling stockholder may sell or otherwise dispose of the shares of Common Stock being registered pursuant to this prospectus. The selling stockholder is an “underwriter” within the meaning of Section 2(a)(11) of the Securities Act.

The selling stockholder will pay all brokerage fees and commissions and similar expenses. We will pay the expenses (except brokerage fees and commissions and similar expenses) incurred in registering the shares, including legal and accounting fees. See “Plan of Distribution.”

We are a “smaller reporting company” under the federal securities laws and, as such, are subject to reduced public company reporting requirements. See “Implications of Being a Smaller Reporting Company.”

We are an “emerging growth company” under the federal securities laws and, as such, are subject to reduced public company reporting requirements. See “Implications of Being an Emerging Growth Company.”

Our Common Stock and warrants exercisable for one share of Common Stock for $11.50 per share (the “Listed Warrants”) are traded on the Nasdaq Stock Market under the symbols “ICU” and “ICUCW,” respectively. On April 20, 2026, the closing price of our Common Stock was $4.63 per share, and the closing price of our Listed Warrants, was $0.0249 per warrant.

On January 5, 2026, we effected a 1-for-10 reverse stock split (the “Reverse Split”) of our issued and outstanding shares of Common Stock, and our shares of Common Stock began trading on a split-adjusted basis on the Nasdaq Capital Market on January 5, 2026 under the same symbol “ICU”. All of our stock options and warrants outstanding immediately prior to the Reverse Split were proportionally adjusted except for the Listed Warrants and the private placement warrants that were issued as part of the SPAC transaction, which total 16,788,000 outstanding warrants in the aggregate (the “Unadjusted Warrants”). The Unadjusted Warrants retain an $11.50 exercise price each and require the exercise of 250 warrants to purchase one share of Common Stock. Unless otherwise indicated, all other share and per share prices in this prospectus have been adjusted to reflect the Reverse Split.

Investing in our securities involves a high degree of risk. You should read “Risk Factors” beginning on page 6 of this prospectus, and under similar headings in the documents incorporated by reference in this prospectus, as well as in any amendments or supplements to this prospectus, to read about factors to consider before purchasing our securities.

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 , 2026.

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