Korro Bio director sells 300 shares at $13.96

Q: What insider transaction did KRRO report for Jean Francois Formela?

Korro Bio, Inc. reported that director Jean Francois Formela, through Atlas Venture investment funds, indirectly sold a total of 300 shares of KRRO common stock on August 26, 2026, in transactions reported on a Form 4.

Q: How many KRRO shares were sold and at what price on this Form 4?

A total of 300 shares of KRRO common stock were sold, split into 249 shares and 51 shares, at a weighted average price of about $13.96 per share, with individual trade prices ranging from $13.955 to $13.98.

Q: Did Jean Francois Formela sell KRRO shares directly or indirectly?

The reported KRRO sales were indirect. The shares are held by Atlas Venture Fund XI, L.P. and Atlas Venture Opportunity Fund II, L.P., and Formela reports them as indirectly owned through these entities.

Q: Does Jean Francois Formela claim full beneficial ownership of these KRRO shares?

No. The filing states that Formela disclaims Section 16 beneficial ownership of the shares held by the Atlas Venture funds, except to the extent of his pecuniary interest in those entities, if any.

Korro Bio, Inc. (KRRO) director Jean Francois Formela, through investment funds associated with Atlas Venture, reported indirect sales of a total of 300 shares of common stock on August 26, 2026.

Filing Impact

(Neutral)

Filing Sentiment

(Neutral)

Form Type

Rhea-AI Filing Summary

Korro Bio, Inc. (KRRO) director Jean Francois Formela, through investment funds associated with Atlas Venture, reported indirect sales of a total of 300 shares of common stock on August 26, 2026. The shares were sold pursuant to a Rule 10b5-1 trading plan at a weighted average price of about $13.96 per share, in multiple trades between $13.955 and $13.98. The shares are held by Atlas Venture Fund XI, L.P. and Atlas Venture Opportunity Fund II, L.P., and Formela disclaims Section 16 beneficial ownership except to the extent of his pecuniary interest.

Insider Trade Summary 10b5-1

Net Seller: 300 shares

Net Sell 2 txns

Insider FORMELA JEAN FRANCOIS

Role Director

Sold 300 shs ($4K)

Type	Security	Shares	Price	Value
Sale	Common Stock ^{F1, F2, F3}	249	$13.96	$3K
Sale	Common Stock ^{F1, F2, F4}	51	$13.96	$711.96

Holdings After Transaction: Common Stock — 141,002 shares (Indirect, See footnote)

Footnotes (4)

F1. Shares were sold pursuant to a Rule 10b5-1 trading plan on April 8, 2026.
F2. The price reported in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $13.955 to $13.98 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 range set forth in this footnote.
F3. 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.
F4. 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 (Atlas Venture Fund XI, L.P.): 249 shares Shares sold (Atlas Venture Opportunity Fund II, L.P.): 51 shares Total shares sold: 300 shares +4 more

7 metrics

Shares sold (Atlas Venture Fund XI, L.P.) 249 shares Indirect sale of KRRO common stock on August 26, 2026

Shares sold (Atlas Venture Opportunity Fund II, L.P.) 51 shares Indirect sale of KRRO common stock on August 26, 2026

Total shares sold 300 shares Aggregate of two indirect sales reported on Form 4

Weighted average sale price $13.96 per share Weighted average for sales on August 26, 2026

Sale price range low $13.955 per share Lowest price among multiple transactions included in the sale

Sale price range high $13.98 per share Highest price among multiple transactions included in the sale

Rule 10b5-1 plan date April 8, 2026 Date of the Rule 10b5-1 trading plan referenced in the footnote

Key Terms

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

4 terms

Rule 10b5-1 trading plan regulatory

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

"The Reporting Person is a member of AVA XI LLC and disclaims Section 16 beneficial ownership of such shares"

pecuniary interest financial

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

FAQ

What insider transaction did KRRO report for Jean Francois Formela?

Korro Bio, Inc. reported that director Jean Francois Formela, through Atlas Venture investment funds, indirectly sold a total of 300 shares of KRRO common stock on August 26, 2026, in transactions reported on a Form 4.

How many KRRO shares were sold and at what price on this Form 4?

A total of 300 shares of KRRO common stock were sold, split into 249 shares and 51 shares, at a weighted average price of about $13.96 per share, with individual trade prices ranging from $13.955 to $13.98.

Were the KRRO insider sales made under a Rule 10b5-1 plan?

Yes. The footnotes state the shares were sold pursuant to a Rule 10b5-1 trading plan dated April 8, 2026, indicating the transactions were pre-arranged under that plan.

Did Jean Francois Formela sell KRRO shares directly or indirectly?

The reported KRRO sales were indirect. The shares are held by Atlas Venture Fund XI, L.P. and Atlas Venture Opportunity Fund II, L.P., and Formela reports them as indirectly owned through these entities.

Does Jean Francois Formela claim full beneficial ownership of these KRRO shares?

No. The filing states that Formela disclaims Section 16 beneficial ownership of the shares held by the Atlas Venture funds, except to the extent of his pecuniary interest in those entities, if any.

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Available on EDGAR 08/28/2026 - 04:30 PM Accepted by SEC EDGAR 08/28/2026 - 04:30 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)
08/26/2026

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	08/26/2026		S⁽¹⁾		249	D	$13.96⁽²⁾	680,948	I	See footnote⁽³⁾
Common Stock	08/26/2026		S⁽¹⁾		51	D	$13.96⁽²⁾	141,002	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 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 $13.955 to $13.98 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 range set forth in this footnote.

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.

	/s/ Ommer Chohan, Attorney-in-fact	08/28/2026
	** 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