Atlas funds tied to Korro Bio (KRRO) log small planned stock sale

Filing Impact

(Neutral)

Filing Sentiment

(Negative)

Form Type

Rhea-AI Filing Summary

Korro Bio director-related funds report small planned share sale. Atlas Venture Fund XI, L.P. and Atlas Venture Opportunity Fund II, L.P., entities associated with director Jean Francois Formela, sold a total of 2,860 shares of Korro Bio common stock at $13.95 per share on May 28, 2026 in open-market transactions under a Rule 10b5-1 trading plan adopted on April 8, 2026.

Following these indirect transactions, Atlas Venture Fund XI, L.P. is shown holding 194,655 shares and Atlas Venture Opportunity Fund II, L.P. is shown holding 939,634 shares of common stock. Formela is a member of the general partner entities and disclaims Section 16 beneficial ownership of these shares except to the extent of any pecuniary interest.

Insider Trade Summary 10b5-1

Net Seller: 2,860 shares ($39,897)

Net Sell 2 txns

Insider FORMELA JEAN FRANCOIS

Role null

Sold 2,860 shs ($40K)

Type	Security	Shares	Price	Value
Sale	Common Stock	2,441	$13.95	$34K
Sale	Common Stock	419	$13.95	$6K

Holdings After Transaction: Common Stock — 939,634 shares (Indirect, See footnote)

Footnotes (1)

Shares were sold pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on April 8, 2026. These shares are held directly by Atlas Venture Fund XI, L.P. ("Atlas XI"). Atlas Venture Associates XI, L.P. ("AVA XI LP") is the general partner of Atlas XI. Atlas Venture Associates XI, LLC ("AVA XI LLC") is the general partner of AVA XI LP. The Reporting Person is a member of AVA XI LLC and disclaims Section 16 beneficial ownership of such shares, except to the extent of his pecuniary interest therein, if any. These shares are held directly by Atlas Venture Opportunity Fund II, L.P. ("AVOF II"). Atlas Venture Associates Opportunity II, L.P. ("AVAO II LP") is the general partner of AVOF II. Atlas Venture Associates Opportunity II, LLC ("AVAO II LLC") is the general partner of AVAO II LP. The Reporting Person is a member of AVAO II LLC and disclaims Section 16 beneficial ownership of such shares, except to the extent of his pecuniary interest therein, if any.

Key Figures

Shares sold: 2,860 shares Sale price: $13.95 per share Post-sale holdings (Atlas Venture Fund XI, L.P.): 194,655 shares +2 more

5 metrics

Shares sold 2,860 shares Total common stock sold on May 28, 2026

Sale price $13.95 per share Open-market sales of common stock

Post-sale holdings (Atlas Venture Fund XI, L.P.) 194,655 shares Common stock holdings following transactions

Post-sale holdings (Atlas Venture Opportunity Fund II, L.P.) 939,634 shares Common stock holdings following transactions

Rule 10b5-1 plan adoption date April 8, 2026 Date trading plan was adopted for these sales

Key Terms

Rule 10b5-1 trading plan, Section 16 beneficial ownership, open-market sale, indirect ownership, +1 more

5 terms

Rule 10b5-1 trading plan regulatory

"Shares were sold pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on April 8, 2026."

A Rule 10b5-1 trading plan is a pre-arranged schedule that allows company insiders to buy or sell stock at specific times, even if they have inside information. It helps prevent accusations of unfair trading by making these transactions look planned and transparent, rather than sneaky or illegal.

Section 16 beneficial ownership regulatory

"The Reporting Person ... disclaims Section 16 beneficial ownership of such shares, except to the extent of his pecuniary interest therein, if any."

open-market sale financial

"transaction_action: "open-market sale"; transaction_code_description: "Sale in open market or private transaction""

An open-market sale is when a shareholder sells existing shares directly on a public exchange to any willing buyer, rather than through a private deal. Think of it like putting goods on a busy market stall where price is set by supply and demand; for investors it matters because such sales increase available supply, can put short-term downward pressure on the stock price, and signal changes in liquidity or investor confidence.

indirect ownership financial

"direct_or_indirect: "I" and ownership_type: "indirect" for the reported common stock transactions."

pecuniary interest financial

"disclaims Section 16 beneficial ownership of such shares, except to the extent of his pecuniary interest therein, if any."

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Form 4 Insider Transactions: What Each Field Means →

06/01/2026 - 05:35 PM

SEC Form 4

FORM 4

UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP

Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934
or Section 30(h) of the Investment Company Act of 1940

OMB APPROVAL

OMB Number:			3235-0287
Estimated average burden
hours per response:			0.5

Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

Check this box to indicate that a transaction was made pursuant to a contract, instruction or written plan for the purchase or sale of equity securities of the issuer that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c). See Instruction 10.

1. Name and Address of Reporting Person^*

FORMELA JEAN FRANCOIS

(Last)

(First)

(Middle)

C/O KORRO BIO, INC.

60 FIRST STREET, 2ND FLOOR, SUITE 250

(Street)

CAMBRIDGE

MASSACHUSETTS

02141

(City)

(State)

(Zip)

UNITED STATES

(Country)

2. Issuer Name and Ticker or Trading Symbol
Korro Bio, Inc. [ KRRO ]

5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)

X	Director	10% Owner
	Officer (give title below)	Other (specify below)

2a. Foreign Trading Symbol

3. Date of Earliest Transaction (Month/Day/Year)
05/28/2026

6. Individual or Joint/Group Filing (Check Applicable Line)

X	Form filed by One Reporting Person
	Form filed by More than One Reporting Person

4. If Amendment, Date of Original Filed (Month/Day/Year)

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1. Title of Security (Instr. 3)	2. Transaction Date (Month/Day/Year)	2A. Deemed Execution Date, if any (Month/Day/Year)	3. Transaction Code (Instr. 8)		4. Securities Acquired (A) or Disposed Of (D) (Instr. 3, 4 and 5)			5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4)	6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	7. Nature of Indirect Beneficial Ownership (Instr. 4)
1. Title of Security (Instr. 3)	2. Transaction Date (Month/Day/Year)	2A. Deemed Execution Date, if any (Month/Day/Year)	Code	V	Amount	(A) or (D)	Price		6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	7. Nature of Indirect Beneficial Ownership (Instr. 4)
Common Stock	05/28/2026		S⁽¹⁾		2,441	D	$13.95	939,634	I	See footnote⁽²⁾
Common Stock	05/28/2026		S⁽¹⁾		419	D	$13.95	194,655	I	See footnote⁽³⁾

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security (Instr. 3)	2. Conversion or Exercise Price of Derivative Security	3. Transaction Date (Month/Day/Year)	3A. Deemed Execution Date, if any (Month/Day/Year)	4. Transaction Code (Instr. 8)		5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5)		6. Date Exercisable and Expiration Date (Month/Day/Year)		7. Title and Amount of Securities Underlying Derivative Security (Instr. 3 and 4)		8. Price of Derivative Security (Instr. 5)	9. Number of derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4)	10. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	11. Nature of Indirect Beneficial Ownership (Instr. 4)
1. Title of Derivative Security (Instr. 3)	2. Conversion or Exercise Price of Derivative Security	3. Transaction Date (Month/Day/Year)	3A. Deemed Execution Date, if any (Month/Day/Year)	Code	V	(A)	(D)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares	8. Price of Derivative Security (Instr. 5)		10. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	11. Nature of Indirect Beneficial Ownership (Instr. 4)

Explanation of Responses:

1. Shares were sold pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on April 8, 2026.

2. These shares are held directly by Atlas Venture Fund XI, L.P. ("Atlas XI"). Atlas Venture Associates XI, L.P. ("AVA XI LP") is the general partner of Atlas XI. Atlas Venture Associates XI, LLC ("AVA XI LLC") is the general partner of AVA XI LP. The Reporting Person is a member of AVA XI LLC and disclaims Section 16 beneficial ownership of such shares, except to the extent of his pecuniary interest therein, if any.

3. These shares are held directly by Atlas Venture Opportunity Fund II, L.P. ("AVOF II"). Atlas Venture Associates Opportunity II, L.P. ("AVAO II LP") is the general partner of AVOF II. Atlas Venture Associates Opportunity II, LLC ("AVAO II LLC") is the general partner of AVAO II LP. The Reporting Person is a member of AVAO II LLC and disclaims Section 16 beneficial ownership of such shares, except to the extent of his pecuniary interest therein, if any.

	/s/ Ommer Chohan, Attorney-in-fact	06/01/2026
	** Signature of Reporting Person	Date
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
* If the form is filed by more than one reporting person, see Instruction 4 (b)(v).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.
Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB Number.
* Form 4: SEC 1474 (03-26)

Source: View Original Filing on SEC EDGAR

FAQ

What insider activity did Korro Bio (KRRO) report in this Form 4?

Korro Bio reported that Atlas Venture Fund XI, L.P. and Atlas Venture Opportunity Fund II, L.P., entities associated with director Jean Francois Formela, sold 2,860 shares of common stock at $13.95 per share on May 28, 2026 in open-market transactions.

Was the Korro Bio (KRRO) insider sale made under a Rule 10b5-1 plan?

Yes. The shares were sold pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on April 8, 2026. Such pre-arranged plans automate trading and can make the timing of transactions less informative about near-term views.

How many Korro Bio (KRRO) shares do the Atlas funds hold after the sale?

After the reported trades, Atlas Venture Fund XI, L.P. is shown holding 194,655 Korro Bio common shares, while Atlas Venture Opportunity Fund II, L.P. is shown holding 939,634 shares, according to the post-transaction ownership figures in the Form 4.

Does Jean Francois Formela directly own the Korro Bio (KRRO) shares sold?

No. The shares are held directly by Atlas Venture Fund XI, L.P. and Atlas Venture Opportunity Fund II, L.P. Formela is a member of their general partner entities and disclaims Section 16 beneficial ownership except for any pecuniary interest.

What type of transaction code appears in this Korro Bio (KRRO) Form 4?

The Form 4 uses transaction code “S,” which indicates a sale in an open market or private transaction. Both reported trades involve common stock and are classified as non-derivative open-market sales at a stated per-share price.