Korro Bio holder plans 6,602-share stock sale

Venture funds affiliated with Korro Bio file a Rule 144 notice covering a 6,602-share resale and disclose several prior block trades in recent months.

Rhea-AI Filing Summary

Korro Bio, Inc. (KRRO) has a Rule 144 notice indicating that Atlas Venture Opportunity Fund II, L.P. plans to sell up to 6,602 shares of Korro Bio common stock through Merrill Lynch on Nasdaq, with an approximate sale date of September 14, 2026 and an aggregate market value of $91,173.62.

The 6,602 shares were acquired in a private placement from the issuer for cash on April 22, 2024. The notice also lists multiple sales of Korro Bio common stock by Atlas Venture Fund XI, L.P. and Atlas Venture Opportunity Fund II, L.P. during the prior three months, including a trade of 101,579 shares on June 23, 2026 for $1,447,785.17.

Key Figures

Shares proposed to be sold: 6,602 shares Aggregate market value of proposed sale: $91,173.62 Korro Bio shares outstanding: 14,725,646 shares +4 more

7 metrics

Shares proposed to be sold 6,602 shares Korro Bio common stock under Rule 144 by Atlas Venture Opportunity Fund II, L.P.

Aggregate market value of proposed sale $91,173.62 Proposed sale of 6,602 Korro Bio shares

Korro Bio shares outstanding 14,725,646 shares Referenced in the securities information section

Acquisition date of shares to be sold April 22, 2024 Private placement from issuer for cash to Atlas Venture Opportunity Fund II, L.P.

Largest single sale in past 3 months 101,579 shares for $1,447,785.17 Sale by Atlas Venture Fund XI, L.P. on June 23, 2026

Example sale by Opportunity Fund II 17,426 shares for $248,369.29 Sale on June 23, 2026 by Atlas Venture Opportunity Fund II, L.P.

Approximate date of proposed sale September 14, 2026 Proposed Rule 144 sale of 6,602 shares

Key Terms

Rule 144, Private Placement, aggregate market value

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.

Private Placement financial

"Common Stock | 04/22/2024 | Private Placement | Issuer"

A private placement is a sale of securities directly to a selected group of investors, typically institutions or accredited investors, instead of through a public offering. It lets a company raise money faster and with fewer regulatory steps; for existing shareholders it matters because the newly issued shares, often sold at a discount, increase the share count and can dilute their ownership.

aggregate market value financial

"| 6602 | 91173.62 | 14725646 | 09/14/2026 | Nasdaq"

Aggregate market value is the combined price you would pay to buy all outstanding shares of a company or all companies in a group at current market prices — essentially the sum of each stock’s market capitalization. It matters to investors because it shows the overall size and weight of an investment or sector (like the total cost to buy every piece of a puzzle), helps compare scale across companies or markets, and influences index composition and risk exposure.

FAQ

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

What does the Form 144 filing mean for Korro Bio (KRRO)?

The filing reports that Atlas Venture Opportunity Fund II, L.P. intends to sell up to 6,602 shares of Korro Bio common stock under Rule 144, with Merrill Lynch as broker and an approximate sale date of September 14, 2026.

How many Korro Bio (KRRO) shares are covered by this Form 144 notice?

The notice covers a proposed sale of 6,602 shares of Korro Bio common stock, with an indicated aggregate market value of $91,173.62 at the time of the filing.

When and how were the Korro Bio (KRRO) shares to be sold acquired?

The 6,602 shares to be sold were acquired by Atlas Venture Opportunity Fund II, L.P. on April 22, 2024 in a private placement from Korro Bio for cash.

Which broker and exchange are listed for the planned Korro Bio (KRRO) sale?

The filing lists Merrill Lynch as the broker and indicates that the Korro Bio common stock is traded on Nasdaq for purposes of the planned Rule 144 sale.

What prior sales of Korro Bio (KRRO) shares are disclosed for the past three months?

The notice lists multiple sales of Korro Bio common stock by Atlas Venture Fund XI, L.P. and Atlas Venture Opportunity Fund II, L.P. between June 22, 2026 and September 11, 2026, including a sale of 101,579 shares for $1,447,785.17 on June 23, 2026.

How many Korro Bio (KRRO) shares are outstanding as referenced in the Form 144?

The filing references 14,725,646 shares of Korro Bio common stock outstanding, as part of the securities information related to the proposed Rule 144 sale.

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

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Available on EDGAR 09/14/2026 - 05:00 PM Accepted by SEC EDGAR 09/14/2026 - 04:58 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	0001885327
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	Korro Bio, Inc.
SEC File Number	001-39062
Address of Issuer	60 First Street 2nd Floor, Suite 250 Cambridge MASSACHUSETTS 02141
Phone	6174681999
Name of Person for Whose Account the Securities are To Be Sold	Atlas Venture Opportunity Fund II, L.P.
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	Shareholder

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 Stock	Merrill Lynch 555 California Street 18th Floor San Francisco CA 94104	6602	91173.62	14725646	09/14/2026	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 Stock	04/22/2024	Private Placement	Issuer			6602	04/22/2024	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
Atlas Venture Fund XI, L.P. 300 Technology Sq Ste 8 Cambridge MA 02139	Common Stock	06/22/2026	3382	47178.9
Atlas Venture Fund XI, L.P. 300 Technology Sq Ste 8 Cambridge MA 02139	Common Stock	06/23/2026	101579	1447785.17
Atlas Venture Fund XI, L.P. 300 Technology Sq Ste 8 Cambridge MA 02139	Common Stock	06/24/2026	41345	603694.88
Atlas Venture Fund XI, L.P. 300 Technology Sq Ste 8 Cambridge MA 02139	Common Stock	07/02/2026	85955	1206249.49
Atlas Venture Fund XI, L.P. 300 Technology Sq Ste 8 Cambridge MA 02139	Common Stock	07/06/2026	817	11405.24
Atlas Venture Fund XI, L.P. 300 Technology Sq Ste 8 Cambridge MA 02139	Common Stock	08/11/2026	1775	24772.79
Atlas Venture Fund XI, L.P. 300 Technology Sq Ste 8 Cambridge MA 02139	Common	08/19/2026	23584	330159.49
Atlas Venture Fund XI, L.P. 300 Technology Sq Ste 8 Cambridge MA 02139	Common Stock	08/26/2026	249	3476.86
Atlas Venture Fund XI, L.P. 300 Technology Sq Ste 8 Cambridge MA 02139	Common Stock	09/11/2026	8450	118177.48
Atlas Venture Opportunity Fund II, L.P. 300 Technology Sq Ste 8 Cambridge MA 02139	Common Stock	06/22/2026	580	8091
Atlas Venture Opportunity Fund II, L.P. 300 Technology Sq Ste 8 Cambridge MA 02139	Common Stock	06/23/2026	17426	248369.29
Atlas Venture Opportunity Fund II, L.P. 300 Technology Sq Ste 8 Cambridge MA 02139	Common Stock	06/24/2026	7093	103567.73
Atlas Venture Opportunity Fund II, L.P. 300 Technology Sq Ste 8 Cambridge MA 02139	Common Stock	07/02/2026	14745	206923.96
Atlas Venture Opportunity Fund II, L.P. 300 Technology Sq Ste 8 Cambridge MA 02139	Common Stock	07/06/2026	8506	118742.91
Atlas Venture Opportunity Fund II, L.P. 300 Technology Sq Ste 8 Cambridge MA 02139	Common Stock	08/11/2026	368	5135.99
Atlas Venture Opportunity Fund II, L.P. 300 Technology Sq Ste 8 Cambridge MA 02139	Common Stock	08/19/2026	4884	68372.58
Atlas Venture Opportunity Fund II, L.P. 300 Technology Sq Ste 8 Cambridge MA 02139	Common Stock	08/26/2026	51	712.13
Atlas Venture Opportunity Fund II, L.P. 300 Technology Sq Ste 8 Cambridge MA 02139	Common Stock	09/11/2026	1750	24474.62

144: Remarks and Signature

Remarks
Date of Notice	09/14/2026
Date of Plan Adoption or Giving of Instruction, If Relying on Rule 10b5-1	04/08/2026
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	Ommer Chohan
ATTENTION: Intentional misstatements or omission of facts constitute Federal Criminal Violations (See 18 U.S.C. 1001)