Korro Bio (KRRO) director-affiliated funds sell 110,023 shares under 10b5-1 plan

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

The filing shows entities associated with director Jean Francois Formela sold 110,023 shares of Korro Bio common stock in open-market transactions. These trades were executed in early July 2026 at prices around $14 per share.

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

Yes. The filing states the shares were sold under a Rule 10b5-1 trading plan adopted on April 8, 2026. Such plans pre-schedule trades, meaning the sale timing was determined in advance rather than chosen in reaction to short-term market movements.

Q: Who actually holds the Korro Bio (KRRO) shares involved in this Form 4?

The shares are held by Atlas Venture Fund XI, L.P. and Atlas Venture Opportunity Fund II, L.P. The director is a member of their general partner entities and disclaims Section 16 beneficial ownership beyond any pecuniary interest.

Q: What type of transactions are reported in this Korro Bio (KRRO) Form 4?

All reported transactions are open-market sales of Korro Bio common stock, coded “S” for sale. There are no option exercises, gifts, or tax-withholding entries disclosed, and the derivative securities section shows no remaining derivative positions in this filing.

Filing Impact

(High)

Filing Sentiment

(Negative)

Form Type

Rhea-AI Filing Summary

Korro Bio director-linked funds reported open-market sales of 110,023 shares of Common Stock. The transactions were executed on July 2 and July 6, 2026 at weighted average prices around $14 per share, through entities associated with Atlas Venture funds.

The sales were made pursuant to a Rule 10b5-1 trading plan adopted on April 8, 2026, indicating they were pre-scheduled rather than discretionary market-timed trades. Following these transactions, the reporting entities together continue to hold large indirect positions, including 146,305 and 706,556 shares of Korro Bio common stock.

Insider Trade Summary 10b5-1

Net Seller: 110,023 shares ($1,542,970)

Net Sell 4 txns

Insider FORMELA JEAN FRANCOIS

Role null

Sold 110,023 shs ($1.54M)

Type	Security	Shares	Price	Value
Sale	Common Stock	817	$13.96	$11K
Sale	Common Stock	8,506	$13.96	$119K
Sale	Common Stock	85,955	$14.03	$1.21M
Sale	Common Stock	14,745	$14.03	$207K

Holdings After Transaction: Common Stock — 706,556 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. 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 $14.16 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 (2) and (5). 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 $14.05 inclusive.

Key Figures

Total shares sold: 110,023 shares July 2, 2026 sale size (fund A): 14,745 shares July 2, 2026 sale size (fund B): 85,955 shares +5 more

8 metrics

Total shares sold 110,023 shares Net open-market sales reported in Form 4

July 2, 2026 sale size (fund A) 14,745 shares Common Stock, open-market sale on July 2, 2026

July 2, 2026 sale size (fund B) 85,955 shares Common Stock, open-market sale on July 2, 2026

July 6, 2026 sale size (fund A) 8,506 shares Common Stock, open-market sale on July 6, 2026

July 6, 2026 sale size (fund B) 817 shares Common Stock, open-market sale on July 6, 2026

Weighted average price (July 2) $14.03 per share Sales in range $13.95–$14.05 inclusive

Weighted average price (July 6) $13.96 per share Sales in range $13.95–$14.16 inclusive

Holdings after trades (funds) 146,305 and 706,556 shares Indirect Common Stock holdings following reported sales

Key Terms

Rule 10b5-1 trading plan, weighted average price, Section 16 beneficial ownership, open-market sale, +2 more

6 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.

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.

Section 16 beneficial ownership regulatory

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

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.

Atlas Venture Fund XI, L.P. financial

"These shares are held directly by Atlas Venture Fund XI, L.P. ("Atlas XI")."

Atlas Venture Opportunity Fund II, L.P. financial

"These shares are held directly by Atlas Venture Opportunity Fund II, L.P. ("AVOF II")."

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Form 4 Insider Transactions: What Each Field Means →

Available on EDGAR 07/07/2026 - 06:05 PM Accepted by SEC EDGAR 07/07/2026 - 06:04 PM

FAQ

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

The filing shows entities associated with director Jean Francois Formela sold 110,023 shares of Korro Bio common stock in open-market transactions. These trades were executed in early July 2026 at prices around $14 per share.

At what prices were the Korro Bio (KRRO) shares sold in this Form 4?

The reported weighted average sale prices were about $14.03 and $13.96 per share. Footnotes note multiple trades within ranges of $13.95–$14.16 and $13.95–$14.05, with detailed breakdowns available from the reporting person upon request.

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

Yes. The filing states the shares were sold under a Rule 10b5-1 trading plan adopted on April 8, 2026. Such plans pre-schedule trades, meaning the sale timing was determined in advance rather than chosen in reaction to short-term market movements.

Who actually holds the Korro Bio (KRRO) shares involved in this Form 4?

The shares are held by Atlas Venture Fund XI, L.P. and Atlas Venture Opportunity Fund II, L.P. The director is a member of their general partner entities and disclaims Section 16 beneficial ownership beyond any pecuniary interest.

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

After the transactions, the reporting entities continue to hold 146,305 shares in one fund and 706,556 shares in another. These figures indicate significant continuing indirect ownership in Korro Bio common stock through the Atlas Venture funds.

What type of transactions are reported in this Korro Bio (KRRO) Form 4?

All reported transactions are open-market sales of Korro Bio common stock, coded “S” for sale. There are no option exercises, gifts, or tax-withholding entries disclosed, and the derivative securities section shows no remaining derivative positions in this filing.

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)
07/02/2026

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	07/02/2026		S⁽¹⁾		85,955	D	$14.03⁽²⁾	707,373	I	See footnote⁽³⁾
Common Stock	07/02/2026		S⁽¹⁾		14,745	D	$14.03⁽²⁾	154,811	I	See footnote⁽⁴⁾
Common Stock	07/06/2026		S⁽¹⁾		817	D	$13.96⁽⁵⁾	706,556	I	See footnote⁽³⁾
Common Stock	07/06/2026		S⁽¹⁾		8,506	D	$13.96⁽⁵⁾	146,305	I	See footnote⁽⁴⁾

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. 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 $14.16 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 (2) and (5).

3. 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.

4. 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.

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 $14.05 inclusive.

	/s/ Ommer Chohan, Attorney-in-fact	07/07/2026
	** 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