Korro Bio (KRRO) director reports 171K-share 10b5-1 plan sale

Rhea-AI Filing Summary

Korro Bio director Jean Francois Formela, reporting indirect interests in Atlas Venture funds, disclosed sales of 171,405 shares of common stock from June 22–24, 2026 at weighted-average prices between $13.95 and $15.10 under a Rule 10b5-1 trading plan adopted April 8, 2026.

Following these transactions, Atlas Venture funds associated with him reported holding 169,556 shares of Korro Bio common stock indirectly, with Formela disclaiming Section 16 beneficial ownership except for any pecuniary interest.

Insights

Equity analyst

Venture funds tied to a Korro Bio director sold shares under a pre-planned 10b5-1 program while retaining large positions.

The filing shows Atlas Venture entities associated with director Jean Francois Formela sold 171,405 shares of Korro Bio Common Stock in eight open-market transactions at prices from $13.95 to $15.10 per share. These are indirect holdings through Atlas funds, not personal direct ownership.

The trades were made under a Rule 10b5-1 trading plan adopted on April 8, 2026, indicating they were pre-scheduled rather than opportunistic. The funds still report substantial indirect holdings, including 169,556 shares, 793,994 shares and 936,252 shares, so this appears as partial profit-taking or portfolio management rather than a full exit.

Insider Trade Summary 10b5-1

Net Seller: 171,405 shares

Net Sell 8 txns

Insider FORMELA JEAN FRANCOIS

Role Director

Sold 171,405 shs ($2.46M)

Type	Security	Shares	Price	Value
Sale	Common Stock	40,679	$14.60	$594K
Sale	Common Stock	666	$14.98	$10K
Sale	Common Stock	6,979	$14.60	$102K
Sale	Common Stock	114	$14.98	$2K
Sale	Common Stock	101,579	$14.25	$1.45M
Sale	Common Stock	17,426	$14.25	$248K
Sale	Common Stock	3,382	$13.95	$47K
Sale	Common Stock	580	$13.95	$8K

Holdings After Transaction: Common Stock — 169,556 shares (Indirect, See footnote)

Footnotes (6)

1. F1. Shares were sold pursuant to a Rule 10b5-1 trading plan adopted by the Reporting Person on April 8, 2026.
2. F2. 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. F3. 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.
4. F4. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $13.95 to $14.49 inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold each separate price within the ranges set forth in footnotes (4), (5) and (6).
5. F5. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $13.95 to $14.88 inclusive.
6. F6. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $14.97 to $15.10 inclusive.

Key Figures

Total shares sold: 171,405 shares Number of sale transactions: 8 transactions Post-transaction indirect holdings: 169,556 shares +2 more

5 metrics

Total shares sold 171,405 shares Aggregate Korro Bio common shares sold indirectly by Atlas Venture funds on June 22–24, 2026

Number of sale transactions 8 transactions Non-derivative common stock sale transactions reported in this Form 4

Post-transaction indirect holdings 169,556 shares Indirect Korro Bio common stock holdings by Atlas Venture funds after the reported sales

Sale price range $13.95–$15.10 per share Weighted-average sale price ranges across multiple transactions as described in footnotes

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

Key Terms

Rule 10b5-1 trading plan, Section 16 beneficial ownership, weighted average price, pecuniary interest, +1 more

5 terms

Rule 10b5-1 trading plan regulatory

"Shares were sold pursuant to a Rule 10b5-1 trading plan adopted"

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

"disclaims Section 16 beneficial ownership of such shares, except"

weighted average price financial

"The price reported in Column 4 is a weighted average price."

Weighted average price is the average price of a security where each trade or component is counted according to its size, so bigger trades pull the average more than smaller ones. Think of it like calculating the average cost of a grocery haul where items you bought more of have greater influence on the final per-item cost. Investors use it to understand the true average price paid or received, judge execution quality, and compare trading performance against market movement.

pecuniary interest financial

"except to the extent of his pecuniary interest therein, if any."

indirect ownership financial

"These shares are held directly by Atlas Venture funds; reported as indirect."

FAQ

What did Korro Bio (KRRO) disclose in Jean Francois Formela's Form 4?

Korro Bio disclosed that Atlas Venture funds associated with director Jean Francois Formela sold 171,405 common shares between June 22–24, 2026. The transactions were reported as indirect holdings and executed under a Rule 10b5-1 trading plan adopted on April 8, 2026.

How many Korro Bio (KRRO) shares remain indirectly held after these sales?

After the reported sales, Atlas Venture funds associated with Formela held 169,556 Korro Bio common shares indirectly. Formela is a member of the funds’ general partner entities and disclaims Section 16 beneficial ownership except to the extent of any pecuniary interest.

Over what dates did Atlas Venture funds sell Korro Bio (KRRO) shares?

The Form 4 reports Atlas Venture funds selling Korro Bio common stock on June 22, 23 and 24, 2026. All eight transactions involved non-derivative common shares and were carried out under a pre-adopted Rule 10b5-1 trading plan dated April 8, 2026.

At what prices were the Korro Bio (KRRO) shares sold in this filing?

Reported sale prices are weighted averages across multiple trades, with ranges from $13.95 to $15.10 per share. Footnotes note that individual trades occurred within narrower bands and that detailed price breakdowns are available upon request to the issuer or the SEC staff.

Were the Korro Bio (KRRO) share sales made under a Rule 10b5-1 plan?

Yes. The filing states the shares were sold under a Rule 10b5-1 trading plan adopted by the reporting person on April 8, 2026. This indicates the sales followed a pre-arranged schedule rather than discretionary trading at the time of execution.

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Form 4 Insider Transactions: What Each Field Means →

Available on EDGAR 06/24/2026 - 08:09 PM Accepted by SEC EDGAR 06/24/2026 - 08:09 PM Learn about SEC filing dates

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).

X

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)
06/22/2026

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)
			Code	V	Amount	(A) or (D)	Price
Common Stock	06/22/2026		S(1)		3,382	D	$13.95	936,252	I	See footnote(2)
Common Stock	06/22/2026		S(1)		580	D	$13.95	194,075	I	See footnote(3)
Common Stock	06/23/2026		S(1)		101,579	D	$14.25(4)	834,673	I	See footnote(2)
Common Stock	06/23/2026		S(1)		17,426	D	$14.25(4)	176,649	I	See footnote(3)
Common Stock	06/24/2026		S(1)		40,679	D	$14.6(5)	793,994	I	See footnote(2)
Common Stock	06/24/2026		S(1)		666	D	$14.98(6)	793,328	I	See footnote(2)
Common Stock	06/24/2026		S(1)		6,979	D	$14.6(5)	169,670	I	See footnote(3)
Common Stock	06/24/2026		S(1)		114	D	$14.98(6)	169,556	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)
				Code	V	(A)	(D)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares

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.

4. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $13.95 to $14.49 inclusive. The Reporting Person undertakes to provide to the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold each separate price within the ranges set forth in footnotes (4), (5) and (6).

5. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $13.95 to $14.88 inclusive.

6. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $14.97 to $15.10 inclusive.

	/s/ Ommer Chohan, Attorney-in-fact	06/24/2026
	** 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)