[424B5] CalciMedica, Inc. Prospectus Supplement (Debt Securities)

Rhea-AI Filing Summary

CALC filed a prospectus supplement for its at-the-market program, stating it may offer and sell shares of common stock with an aggregate offering price of up to $9,700,000 from time to time through H.C. Wainwright & Co. as sales agent under Form S-3 General Instruction I.B.6.

The filing cites a public float of approximately $36.3 million, based on 14,399,531 shares outstanding and 10,146,506 shares held by non‑affiliates at a $3.58 closing price on September 9, 2025. The company has sold $2.3 million of securities under I.B.6 during the prior 12 months. The stock last traded at $3.03 on November 5, 2025. Pursuant to I.B.6, public primary sales cannot exceed one‑third of the public float in any 12‑month period while float remains below $75.0 million.

Filed Pursuant to Rule 424(b)(5)

Registration No. 333-273949

PROSPECTUS SUPPLEMENT

(To Prospectus Supplement dated December 20, 2024

To Prospectus dated August 18, 2023)

Up to $9,700,000 of Shares of

Common Stock

This prospectus supplement amends and supplements the information in our prospectus dated August 18, 2023, as supplemented by the prospectus supplement dated December 20, 2024 (the “Prior Prospectus Supplement”, and, together with the accompanying prospectus, the “Prior Prospectus”), filed as part of our registration statement on Form S-3 (File No. 333-273949). This prospectus supplement should be read in conjunction with the Prior Prospectus, and is qualified by reference thereto, except to the extent that the information herein amends or supersedes the information contained in the Prior Prospectus. This prospectus supplement is not complete without, and may only be delivered or utilized in connection with, the Prior Prospectus, and any future amendments or supplements thereto.

We filed the Prior Prospectus to register the offer and sale of our common stock, par value $0.0001 per share, from time to time pursuant to the terms of that certain at the market offering agreement (the “Offering Agreement”), between H.C. Wainwright & Co., LLC (“Wainwright”), acting as sales agent, and us.

We are filing this prospectus supplement to amend the Prior Prospectus to update the amount of shares we are eligible to sell under General Instruction I.B.6 on Form S-3. As a result of these limitations and the current public float of our common stock, and in accordance with the terms of the Offering Agreement, we may offer and sell shares of our common stock having an aggregate offering price of up to $9,700,000 from time to time through Wainwright, as further described below.

As of the date of this prospectus supplement, the aggregate market value of our common stock held by non-affiliates of our public float was approximately $36.3 million based on a total number of 14,399,531 shares of common stock outstanding, of which 10,146,506 shares of common stock were held by non-affiliates, at a price of $3.58 per share, the closing sales price of our common stock on September 9, 2025, which is the highest closing price of our common stock on the Nasdaq Capital Market within the prior 60 days. We have sold $2.3 million of securities pursuant to General Instruction I.B.6 of Form S-3 during the prior 12-calendar month period that ends on and includes the date of this prospectus supplement (excluding this offering). Accordingly, based on the foregoing, we are currently eligible under General Instruction I.B.6 of Form S-3 to offer and sell shares of our common stock having an aggregate offering price of up to $9,700,000. Pursuant to General Instruction I.B.6 of Form S-3, in no event will we sell securities in a public primary offering with a value exceeding one-third of our public float in any 12-month period so long as our public float remains below $75.0 million.

Our common stock is listed on the Nasdaq Capital Market under the trading symbol “CALC.” On November 5, 2025, the last reported sale price of our common stock was $3.03 per share.

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.

H.C. Wainwright & Co.

The date of this prospectus supplement is November 6, 2025.

FAQ

What did CALC file in this 424B5 supplement?

It updated its at-the-market program and may sell up to $9,700,000 of common stock from time to time through H.C. Wainwright & Co. as sales agent.

What limits CALC’s ATM capacity under S-3?

General Instruction I.B.6 caps public primary offerings at one‑third of public float in any 12‑month period while float is below $75.0 million.

What is CALC’s current public float used for the I.B.6 calculation?

Approximately $36.3 million, based on 10,146,506 non‑affiliate shares at $3.58 (the highest closing price within the prior 60 days on September 9, 2025).

How many shares are outstanding for CALC?

Shares outstanding were 14,399,531 as of the date referenced in the supplement’s float calculation.

How much has CALC sold under I.B.6 in the last 12 months?

It has sold $2.3 million of securities during the prior 12‑month period (excluding this offering).

What is CALC’s trading symbol and recent price?

The stock trades on Nasdaq as “CALC”. The last reported sale price was $3.03 on November 5, 2025.