Korro Bio (KRRO) director-affiliated Atlas funds sell 171K shares under 10b5-1 plan

Q: Were the Korro Bio (KRRO) insider sales made under a Rule 10b5-1 trading plan?

Yes. A footnote states the shares were sold pursuant to a Rule 10b5-1 trading plan adopted on April 8, 2026 . Such plans pre-schedule trades, indicating these dispositions were arranged in advance rather than timed discretionarily.

Q: Who actually holds the Korro Bio (KRRO) shares involved in these transactions?

The shares are held by Atlas Venture Fund XI, L.P. and Atlas Venture Opportunity Fund II, L.P. . General partner entities manage these funds, and director Jean Francois Formela is a member of those general partners with only a pecuniary interest in the holdings.

Q: Does Jean Francois Formela personally own the Korro Bio (KRRO) shares sold?

The filing explains that Formela disclaims Section 16 beneficial ownership of the Atlas fund shares, except for any pecuniary interest. The positions are held by Atlas Venture funds, with Formela participating through their general partner entities.

Filing Impact

(Very High)

Filing Sentiment

(Negative)

Form Type

Rhea-AI Filing Summary

Korro Bio, Inc. director-affiliated investment funds reported multiple open-market sales of Common Stock. Entities associated with director Jean Francois Formela sold a total of 171,405 shares between $13.95 and $15.10 per share, executed under a pre-arranged Rule 10b5-1 trading plan adopted on April 8, 2026. The shares are held by Atlas Venture funds, where Formela is a member of the general partner entities and disclaims Section 16 beneficial ownership except for any pecuniary interest. Following these trades, indirect holdings disclosed in the filing remain substantial, including 169,556 shares, 793,994 shares and 936,252 shares reported for the relevant entities.

Insights

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 ($2,458,582)

Net Sell 8 txns

Insider FORMELA JEAN FRANCOIS

Role null

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 — 793,994 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. 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). 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. 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

Shares sold: 171,405 shares Lowest sale price: $13.95/share Highest sale price: $15.10/share +3 more

6 metrics

Shares sold 171,405 shares Total net shares sold across eight open-market transactions

Lowest sale price $13.95/share Lower end of weighted average price ranges in June 2026 sales

Highest sale price $15.10/share Upper end of weighted average price ranges in June 2026 sales

Post-sale holding example 1 169,556 shares Indirect holding reported after a June 24, 2026 transaction

Post-sale holding example 2 793,994 shares Indirect holding reported after a June 24, 2026 transaction

Post-sale holding example 3 936,252 shares Indirect holding reported after a June 22, 2026 transaction

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 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 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."

weighted average price financial

"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."

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

"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"

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.

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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

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)
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)
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	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)
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.

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)

Source: View Original Filing on SEC EDGAR

FAQ

How many Korro Bio (KRRO) shares were sold in this Form 4 filing?

The entities associated with director Jean Francois Formela sold 171,405 shares of Korro Bio Common Stock. These sales occurred across eight open-market transactions, as summarized in the filing’s transaction data and aggregate transaction summary.

What prices did the Korro Bio (KRRO) shares sell for in the reported trades?

The reported sales occurred at weighted average prices between $13.95 and $15.10 per share. Footnotes explain that each line reflects multiple trades within ranges such as $13.95–$14.49, $13.95–$14.88, and $14.97–$15.10.

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

Yes. A footnote states the shares were sold pursuant to a Rule 10b5-1 trading plan adopted on April 8, 2026. Such plans pre-schedule trades, indicating these dispositions were arranged in advance rather than timed discretionarily.

Who actually holds the Korro Bio (KRRO) shares involved in these transactions?

The shares are held by Atlas Venture Fund XI, L.P. and Atlas Venture Opportunity Fund II, L.P.. General partner entities manage these funds, and director Jean Francois Formela is a member of those general partners with only a pecuniary interest in the holdings.

What Korro Bio (KRRO) stake remains after these reported sales?

The filing shows the Atlas-affiliated entities still hold large indirect positions after selling 171,405 shares. Reported post-transaction balances include 169,556 shares, 793,994 shares and 936,252 shares for the relevant investment funds disclosed.

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

The filing explains that Formela disclaims Section 16 beneficial ownership of the Atlas fund shares, except for any pecuniary interest. The positions are held by Atlas Venture funds, with Formela participating through their general partner entities.