Septerna officer proposes roughly $391K share sale

The proposed shares are to come from option exercises over the next three months; two earlier sales are identified as 10b5-1 sales.

Rhea-AI Filing Summary

Septerna, Inc. (SEPN) officer Daniel Long gave notice of a proposed sale of 10,001 common shares, with an approximate aggregate market value of $391,339.13 and an approximate sale date of October 1, 2026. The securities to be sold were and will be received upon stock-option exercises over the next three months. Morgan Stanley Smith Barney LLC is listed as broker. Prior sales identified as 10b5-1 sales include 3,333 shares on September 1, 2026, and 3,334 shares on August 3, 2026.

Key Figures

Proposed sale: 10,001 common shares Aggregate market value: Approximately $391,339.13 Shares outstanding: 46,676,947 shares +4 more

7 metrics

Proposed sale 10,001 common shares Approximate sale date October 1, 2026

Aggregate market value Approximately $391,339.13 Proposed sale

Shares outstanding 46,676,947 shares Securities information

Prior sale 3,333 common shares Sold September 1, 2026; identified as a 10b5-1 sale

Reported sale amount $126,077.72 Sale on September 1, 2026

Prior sale 3,334 common shares Sold August 3, 2026; identified as a 10b5-1 sale

Reported sale amount $114,919.98 Sale on August 3, 2026

Key Terms

Rule 144, 10b5-1 Sales, stock options

3 terms

Rule 144 regulatory

"See the definition of “person” in paragraph (a) of Rule 144"

Rule 144 is a U.S. securities regulation that sets conditions under which restricted or insider-held shares can be legally resold to the public, such as required holding periods, availability of public information, limits on how much can be sold at once, and certain filing requirements. For investors it matters because it determines when previously locked-up shares can enter the market — like a release valve that can increase supply, affect share price, and signal insider intent.

10b5-1 Sales regulatory

"10b5-1 Sales for DANIEL LONG"

10b5-1 sales are pre-arranged stock-trading plans that let company insiders automatically buy or sell shares according to a fixed schedule or formula, even if they later learn confidential information. Think of it as setting up an automatic thermostat for trades: it creates a clear, documented path that can protect insiders from insider-trading accusations and gives investors a signal about predictable insider activity—though it can also simply be a way for insiders to diversify or raise cash.

stock options financial

"received upon the exercise of stock options over the next three months"

Stock options are agreements that give a person the right to buy or sell a company's stock at a specific price within a certain time frame. They are often used as a reward or incentive, similar to a coupon that can be used later if the stock price rises, allowing the holder to make a profit.

FAQ

AI-generated questions and answers. How Rhea-AI works. Not financial advice.

How many SEPN shares does Daniel Long plan to sell?

Daniel Long gave notice of a proposed sale of 10,001 common shares, with an approximate aggregate market value of $391,339.13. The securities information lists an approximate sale date of October 1, 2026.

What recent SEPN sales did Daniel Long report?

The past-three-month sales table lists 3,333 common shares sold on September 1, 2026, for $126,077.72 and 3,334 common shares sold on August 3, 2026, for $114,919.98. Both entries are identified as 10b5-1 sales.

AI-generated analysis. How Rhea-AI works. Not financial advice.

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Available on EDGAR 10/01/2026 - 04:32 PM Accepted by SEC EDGAR 10/01/2026 - 04:32 PM Learn about SEC filing dates

Form 144 Filer Information	UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 Form 144 NOTICE OF PROPOSED SALE OF SECURITIES PURSUANT TO RULE 144 UNDER THE SECURITIES ACT OF 1933
FORM 144

144: Filer Information

Filer CIK	0002040349
Filer CCC	XXXXXXXX
Is this a LIVE or TEST Filing?	LIVE TEST
Submission Contact Information
Name
Phone
E-Mail Address

144: Issuer Information

Name of Issuer	Septerna, Inc.
SEC File Number	001-42382
Address of Issuer	250 East Grand Avenue South San Francisco CALIFORNIA 94080
Phone	650-338-3533
Name of Person for Whose Account the Securities are To Be Sold	DANIEL LONG
See the definition of "person" in paragraph (a) of Rule 144. Information is to be given not only as to the person for whose account the securities are to be sold but also as to all other persons included in that definition. In addition, information shall be given as to sales by all persons whose sales are required by paragraph (e) of Rule 144 to be aggregated with sales for the account of the person filing this notice.
Relationship to Issuer	Officer

144: Securities Information

Title of the Class of Securities To Be Sold	Name and Address of the Broker	Number of Shares or Other Units To Be Sold	Aggregate Market Value	Number of Shares or Other Units Outstanding	Approximate Date of Sale	Name the Securities Exchange
Common	Morgan Stanley Smith Barney LLC Executive Financial Services 1 New York Plaza 8th Floor New York NY 10004	10001	391339.13	46676947	10/01/2026	NASDAQ

Furnish the following information with respect to the acquisition of the securities to be sold and with respect to the payment of all or any part of the purchase price or other consideration therefor:

144: Securities To Be Sold

Title of the Class	Date you Acquired	Nature of Acquisition Transaction	Name of Person from Whom Acquired	Is this a Gift?	Date Donor Acquired	Amount of Securities Acquired	Date of Payment	Nature of Payment *
Common	10/01/2026	Exercise of Stock Options	Issuer			10001	10/01/2026	Cash

* If the securities were purchased and full payment therefor was not made in cash at the time of purchase, explain in the table or in a note thereto the nature of the consideration given. If the consideration consisted of any note or other obligation, or if payment was made in installments describe the arrangement and state when the note or other obligation was discharged in full or the last installment paid.

Furnish the following information as to all securities of the issuer sold during the past 3 months by the person for whose account the securities are to be sold.

144: Securities Sold During The Past 3 Months

Name and Address of Seller	Title of Securities Sold	Date of Sale	Amount of Securities Sold	Gross Proceeds
10b5-1 Sales for DANIEL LONG 250 East Grand Avenue South San Francisco CA 94080	Common	09/01/2026	3333	126077.72
10b5-1 Sales for DANIEL LONG 250 East Grand Avenue South San Francisco CA 94080	Common	08/03/2026	3334	114919.98

144: Remarks and Signature

Remarks	The securities to be sold were and will be received upon the exercise of stock options over the next three months. The dates of acquisition and payment were and will be the dates of exercise/sale.
Date of Notice	10/01/2026
Date of Plan Adoption or Giving of Instruction, If Relying on Rule 10b5-1	03/20/2026
ATTENTION:
The person for whose account the securities to which this notice relates are to be sold hereby represents by signing this notice that he does not know any material adverse information in regard to the current and prospective operations of the Issuer of the securities to be sold which has not been publicly disclosed. If such person has adopted a written trading plan or given trading instructions to satisfy Rule 10b5-1 under the Exchange Act, by signing the form and indicating the date that the plan was adopted or the instruction given, that person makes such representation as of the plan adoption or instruction date.
Signature	/s/ Daniel Long
ATTENTION: Intentional misstatements or omission of facts constitute Federal Criminal Violations (See 18 U.S.C. 1001)