Kardigan (KARD) backer ARCH discloses 16.2% ownership stake post-IPO

Rhea-AI Filing Summary

ARCH Venture Fund XIII and affiliates have disclosed a major ownership position in Kardigan, Inc. on Schedule 13D. They beneficially own 15,042,035 shares of common stock, representing 16.2% of Kardigan’s 93,089,121 shares outstanding following the IPO.

ARCH accumulated its stake through multiple preferred stock financings that converted into common stock at the IPO, plus a June 22, 2026 purchase of 1,250,000 IPO shares at $16.00 per share. In total, ARCH reports paying $194,999,973.81 for these securities.

The fund also holds a warrant for 876,040 shares at an exercise price of $13.4135 per share, exercisable only once Kardigan reaches a $5.0 billion market valuation and expiring on September 4, 2035. ARCH has registration rights under an Investors’ Rights Agreement and is subject to a 180‑day IPO lock-up from June 17, 2026. The shares are held for investment, and ARCH may buy more or sell depending on future conditions.

Key Figures

Beneficial ownership: 15,042,035 shares Ownership percentage: 16.2% Shares outstanding: 93,089,121 shares +5 more

8 metrics

Beneficial ownership 15,042,035 shares Common stock beneficially owned by ARCH reporting persons

Ownership percentage 16.2% Portion of Kardigan common stock outstanding after IPO

Shares outstanding 93,089,121 shares Kardigan common stock outstanding following IPO

IPO share purchase 1,250,000 shares at $16.00 Common stock bought from underwriters on June 22, 2026

Total amount invested $194,999,973.81 Aggregate consideration paid by AVF XIII for Kardigan securities

Warrant size and strike 876,040 shares at $13.4135 Common stock warrant issued with Series B financing

Warrant trigger valuation $5.0 billion Company market valuation required before warrant may be exercised

Lock-up duration 180 days after June 17, 2026 Period during which ARCH agreed not to sell or hedge shares

Key Terms

Schedule 13D, beneficially own, Investors' Rights Agreement, Lock-Up Agreement, +2 more

6 terms

Schedule 13D regulatory

"Please analyze the following financial content according to the instructions above. ... form_type": "SCHEDULE 13D""

A Schedule 13D is a legal document that investors file with regulators when they buy a large enough stake in a company to potentially influence its management or decisions. It provides details about the investor’s intention, ownership stake, and plans, helping other investors understand who is gaining control and what their motives might be.

beneficially own financial

"may be deemed to beneficially own the AVF XIII Record Shares"

Beneficially own means having the economic rights and risks of a security—such as the right to receive dividends, sell the shares, or profit from price changes—whether or not your name appears on the official share register. Think of it like renting a car: you use it and reap the benefits even if the title lists someone else. Investors care because beneficial ownership determines who truly controls value, must be disclosed under securities rules, and can signal potential influence or trading activity that affects a stock’s price.

Investors' Rights Agreement financial

"Amended and Restated Investors' Rights Agreement, dated September 4, 2025"

Lock-Up Agreement financial

"AVF XIII has entered into a lock-up agreement with the underwriters of the IPO"

A lock-up agreement is a contract that prevents company insiders and early investors from selling their shares for a fixed period after a stock sale, often after an initial public offering. It matters to investors because it temporarily limits the number of shares that can hit the market, which can keep the share price steadier; when the lock-up ends, a sudden increase in available shares can create extra volatility, revealing insiders’ confidence or lack thereof.

Warrant financial

"a Warrant exercisable for 876,040 shares of Common Stock at an exercise price of $13.4135 per share"

A warrant is a time-limited financial contract that gives its holder the right to buy a company's shares at a set price before a specified date, like a coupon that lets you purchase stock at a fixed discount for a limited time. It matters to investors because warrants offer leveraged exposure to a stock’s upside and can dilute existing shareholders if exercised, so they affect potential gains and the company’s outstanding share count.

market valuation financial

"only upon the first date on which the Issuer achieves a market valuation of $5.0 billion"

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FAQ

How much of Kardigan (KARD) does ARCH Venture currently own?

ARCH Venture Fund XIII and affiliated reporting persons beneficially own 15,042,035 Kardigan common shares, equal to 16.2% of the company’s 93,089,121 shares outstanding after the IPO. This sizable stake makes ARCH a significant shareholder with shared voting and dispositive power over the position.

How did ARCH Venture build its Kardigan (KARD) position and what did it pay?

ARCH built its Kardigan stake through multiple Series A, Series B and Series B‑1 preferred stock rounds that converted into common at the IPO, plus IPO shares. The filing states AVF XIII paid a total of $194,999,973.81 across these transactions, including 1,250,000 IPO shares at $16.00 each.

What warrant rights does ARCH hold in Kardigan (KARD)?

ARCH holds a warrant exercisable for 876,040 Kardigan common shares at an exercise price of $13.4135 per share. The warrant becomes exercisable only once Kardigan first reaches a $5.0 billion market valuation and expires on September 4, 2035, adding long‑dated upside exposure.

What lock-up restrictions apply to ARCH’s Kardigan (KARD) shares?

ARCH entered a lock-up agreement with the IPO underwriters. For 180 days after June 17, 2026, it generally may not sell, hedge, or otherwise dispose of Kardigan common stock without prior written consent from J.P. Morgan Securities LLC, Jefferies LLC, Leerink Partners LLC and TD Securities (USA) LLC.

What registration rights does ARCH have for its Kardigan (KARD) shares?

Under an Amended and Restated Investors’ Rights Agreement dated September 4, 2025, Kardigan granted ARCH demand, piggyback and shelf registration rights on its common shares. These rights terminate once specified conditions are met, including ARCH and affiliates holding under 1% of Kardigan’s outstanding capital stock.

How many Kardigan (KARD) options and RSUs does Paul Berns hold?

Reporting person Paul Berns holds options to purchase 113,513 Kardigan common shares, of which 53,483 are exercisable now and within the next 60 days. He also holds 20,706 restricted stock units, with none exercisable within the next 60 days, which are included in his reported beneficial ownership.

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13D

Under the Securities Exchange Act of 1934

Kardigan, Inc.

(Name of Issuer)

Common Stock, $0.00001 par value per share

(Title of Class of Securities)

48563V117

(CUSIP Number)

Mark McDonnell
ARCH Venture Management, LLC, 8755 W. Higgins Road, Suite 1025
Chicago, IL, 60631
(773) 380 6600

(Name, Address and Telephone Number of Person Authorized to Receive Notices and Communications)

06/22/2026

(Date of Event Which Requires Filing of This Statement)

If the filing person has previously filed a statement on Schedule 13G to report the acquisition that is the subject of this Schedule 13D, and is filing this schedule because of §§ 240.13d-1(e), 240.13d-1(f) or 240.13d-1(g), check the following box.

The information required on the remainder of this cover page shall not be deemed to be "filed" for the purpose of Section 18 of the Securities Exchange Act of 1934 ("Act") or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act (however, see the Notes).

schemaVersion:

SCHEDULE 13D

CUSIP Number(s): 48563V117

1

Name of reporting person

ARCH Venture Fund XIII, L.P.

2

Check the appropriate box if a member of a Group (See Instructions)

(a)
(b)

3

SEC use only

4

Source of funds (See Instructions)

WC

5

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

6

Citizenship or place of organization

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 0.00
8	Shared Voting Power 15,042,035.00
9	Sole Dispositive Power 0.00
10	Shared Dispositive Power 15,042,035.00

11

Aggregate amount beneficially owned by each reporting person

15,042,035.00

12

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

13

Percent of class represented by amount in Row (11)

16.2 %

14

Type of Reporting Person (See Instructions)

PN

SCHEDULE 13D

CUSIP Number(s): 48563V117

1

Name of reporting person

ARCH Venture Partners XIII, L.P.

2

Check the appropriate box if a member of a Group (See Instructions)

(a)
(b)

3

SEC use only

4

Source of funds (See Instructions)

WC

5

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

6

Citizenship or place of organization

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 0.00
8	Shared Voting Power 15,042,035.00
9	Sole Dispositive Power 0.00
10	Shared Dispositive Power 15,042,035.00

11

Aggregate amount beneficially owned by each reporting person

15,042,035.00

12

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

13

Percent of class represented by amount in Row (11)

16.2 %

14

Type of Reporting Person (See Instructions)

PN

SCHEDULE 13D

CUSIP Number(s): 48563V117

1

Name of reporting person

ARCH Venture Partners XIII, LLC

2

Check the appropriate box if a member of a Group (See Instructions)

(a)
(b)

3

SEC use only

4

Source of funds (See Instructions)

AF

5

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

6

Citizenship or place of organization

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 0.00
8	Shared Voting Power 15,042,035.00
9	Sole Dispositive Power 0.00
10	Shared Dispositive Power 15,042,035.00

11

Aggregate amount beneficially owned by each reporting person

15,042,035.00

12

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

13

Percent of class represented by amount in Row (11)

16.2 %

14

Type of Reporting Person (See Instructions)

OO

SCHEDULE 13D

CUSIP Number(s): 48563V117

1

Name of reporting person

Robert Nelsen

2

Check the appropriate box if a member of a Group (See Instructions)

(a)
(b)

3

SEC use only

4

Source of funds (See Instructions)

AF

5

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

6

Citizenship or place of organization

UNITED STATES

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 0.00
8	Shared Voting Power 15,042,035.00
9	Sole Dispositive Power 0.00
10	Shared Dispositive Power 15,042,035.00

11

Aggregate amount beneficially owned by each reporting person

15,042,035.00

12

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

13

Percent of class represented by amount in Row (11)

16.2 %

14

Type of Reporting Person (See Instructions)

IN

SCHEDULE 13D

CUSIP Number(s): 48563V117

1

Name of reporting person

Keith Crandell

2

Check the appropriate box if a member of a Group (See Instructions)

(a)
(b)

3

SEC use only

4

Source of funds (See Instructions)

AF

5

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

6

Citizenship or place of organization

UNITED STATES

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 0.00
8	Shared Voting Power 15,042,035.00
9	Sole Dispositive Power 0.00
10	Shared Dispositive Power 15,042,035.00

11

Aggregate amount beneficially owned by each reporting person

15,042,035.00

12

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

13

Percent of class represented by amount in Row (11)

16.2 %

14

Type of Reporting Person (See Instructions)

IN

SCHEDULE 13D

CUSIP Number(s): 48563V117

1

Name of reporting person

Kristina Burow

2

Check the appropriate box if a member of a Group (See Instructions)

(a)
(b)

3

SEC use only

4

Source of funds (See Instructions)

AF

5

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

6

Citizenship or place of organization

UNITED STATES

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 0.00
8	Shared Voting Power 15,042,035.00
9	Sole Dispositive Power 0.00
10	Shared Dispositive Power 15,042,035.00

11

Aggregate amount beneficially owned by each reporting person

15,042,035.00

12

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

13

Percent of class represented by amount in Row (11)

16.2 %

14

Type of Reporting Person (See Instructions)

IN

SCHEDULE 13D

CUSIP Number(s): 48563V117

1

Name of reporting person

Steven Gillis

2

Check the appropriate box if a member of a Group (See Instructions)

(a)
(b)

3

SEC use only

4

Source of funds (See Instructions)

AF

5

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

6

Citizenship or place of organization

UNITED STATES

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 0.00
8	Shared Voting Power 15,042,035.00
9	Sole Dispositive Power 0.00
10	Shared Dispositive Power 15,042,035.00

11

Aggregate amount beneficially owned by each reporting person

15,042,035.00

12

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

13

Percent of class represented by amount in Row (11)

16.2 %

14

Type of Reporting Person (See Instructions)

IN

SCHEDULE 13D

CUSIP Number(s): 48563V117

1

Name of reporting person

Paul Berns

2

Check the appropriate box if a member of a Group (See Instructions)

(a)
(b)

3

SEC use only

4

Source of funds (See Instructions)

AF

5

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

6

Citizenship or place of organization

UNITED STATES

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 53,483.00
8	Shared Voting Power 15,042,035.00
9	Sole Dispositive Power 53,483.00
10	Shared Dispositive Power 15,042,035.00

11

Aggregate amount beneficially owned by each reporting person

15,095,518.00

12

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

13

Percent of class represented by amount in Row (11)

16.2 %

14

Type of Reporting Person (See Instructions)

IN

SCHEDULE 13D

Item 1.	Security and Issuer
(a)	Title of Class of Securities: Common Stock, $0.00001 par value per share
(b)	Name of Issuer: Kardigan, Inc.
(c)	Address of Issuer's Principal Executive Offices: 506 Carnegie Center Drive, Suite 201, Princeton, NEW JERSEY , 08540.
Item 2.	Identity and Background
(a)	This statement is being filed by (1) ARCH Venture Fund XIII, L.P. ("AVF XIII"), (2) ARCH Venture Partners XIII, L.P. ("AVP XIII LP") which is the sole general partner of AVF XIII, (3) ARCH Venture Partners XIII, LLC ("AVP XIII LLC") which is the sole general partner of AVP XIII LP, (4) Keith Crandell ("Crandell"), (5) Robert Nelsen ("Nelsen"), (6) Kristina Burow ("Burow"), (7) Steven Gillis ("Gillis"), and (8) Paul Berns ("Berns"). Nelsen, Crandell, Burow, Gillis, and Berns are referred to collectively as the "AVP XIII Investment Committee Members." Each of the individuals and entities above shall be referred to herein as a "Reporting Person" and collectively as the "Reporting Persons."
(b)	The business address of each of the Reporting Persons is 8755 West Higgins Road, Suite 1025, Chicago, IL, 60631.
(c)	The principal business of AVP XIII LP is to act as the general partner of AVF XIII and the principal business of AVP XIII LLC is to act as the general partner of AVP XIII LP. AVP XIII Investment Committee Members act as investment committee members of AVP XIII LLC, and as managing directors or investment committee members of a number of affiliated partnerships with similar businesses.
(d)	During the five years prior to the date hereof, none of the Reporting Persons has been convicted in a criminal proceeding.
(e)	During the five years prior to the date hereof, none of the Reporting Persons has been a party to a civil proceeding of a judicial or administrative body of competent jurisdiction ending in a judgment, decree or final order enjoining future violations of, or prohibiting or mandating activities subject to, Federal or State securities laws or finding any violation with respect to such laws.
(f)	AVF XIII and AVP XIII LP are limited partnerships organized under the laws of the State of Delaware. AVP XIII LLC is a limited liability company organized under the laws of the State of Delaware. Each AVP XIII Committee Member is a US citizen.
Item 3.	Source and Amount of Funds or Other Consideration
	On June 6, 2024, AVF XIII purchased 1,202,764 shares of Series A Preferred Stock of Kardigan, Inc. (the "Issuer") at a purchase price of $12.1941 per share. The number of shares reflects a 1 for 1.5928 forward stock split (the "Stock Split") effective immediately prior to the closing of the initial public offering of the Issuer (the "IPO"). Each share of Series A Preferred Stock automatically converted into one share of the Issuer's Common Stock, par value $0.00001 per share (the "Common Stock") at the closing of the IPO. On July 22, 2024, AVF XIII purchased 1,530,791 shares of Series A Preferred Stock of the Issuer at a purchase price of $12.1941 per share. The number of shares reflects the Stock Split. Each share of Series A Preferred Stock automatically converted into one share of Common Stock at the closing of the IPO. On February 14, 2025, AVF XIII purchased 2,733,557 shares of Series A Preferred Stock of the Issuer at a purchase price of $12.1941 per share. The number of shares reflects the Stock Split. Each share of Series A Preferred Stock automatically converted into one share of Common Stock at the closing of the IPO. On August 27, 2025, AVF XIII purchased 2,733,557 shares of Series A Preferred Stock of the Issuer at a purchase price of $12.1941 per share. The number of shares reflects the Stock Split. Each share of Series A Preferred Stock automatically converted into one share of Common Stock at the closing of the IPO. On September 5, 2025, AVF XIII purchased 1,917,731 shares of Series B Preferred Stock and 1,809,846 shares of Series B-1 Preferred Stock of the Issuer at a purchase price of $13.4135 per share. AVF XIII also received a Common Stock Warrant for 876,040 shares at an exercise price of $13.4135 per share (the "Warrants"). The number of shares reflects the Stock Split. Each share of Series B Preferred Stock and Series B-1 Preferred Stock automatically converted into one share of Common Stock at the closing of the IPO. On October 15, 2025, AVF XIII purchased 1,863,789 shares of Series B-1 Preferred Stock of the Issuer at a purchase price of $13.4135 per share. The number of shares reflects the Stock Split. Each share of Series B-1 Preferred Stock automatically converted into one share of Common Stock at the closing of the IPO. On June 22, 2026, AVF XIII purchased 1,250,000 shares of Common Stock at a purchase price of $16.00 per share from the underwriters of the IPO. The source of funds for each of the purchases described in this Item 3 was the working capital of AVF XIII. No part of the purchase price paid by AVF XIII was represented by funds or other consideration borrowed or otherwise obtained for the purpose of acquiring, holding, trading or voting the shares of Common Stock described above. The total amount paid for the securities purchased in the above-listed transactions is as follows: AVF XIII: $194,999,973.81
Item 4.	Purpose of Transaction
	AVF XIII and the other Reporting Persons acquired the Common Stock for investment purposes. Depending on market conditions, the continuing evaluation of the business and prospects of the Issuer and other factors, AVF XIII and other Reporting Persons may dispose of or acquire additional shares of Common Stock of the Issuer. Except as set forth above, none of the Reporting Persons has any present plans which relate to or would result in the matters set forth in subparagraphs (a) - (j) of Item 4 of Schedule 13D.
Item 5.	Interest in Securities of the Issuer
(a)	AVF XIII is the record owner of 15,042,035 shares of Common Stock and Warrants exercisable for 876,040 shares of Common Stock ("AVF XIII Record Shares"). AVP XIII LP, as the sole general partner of AVF XIII LP, may be deemed to beneficially own the AVF XIII Record Shares. AVP XIII LLC, as the sole general partner of AVP XIII LP, may be deemed to beneficially own the AVF XIII Record Shares. The Warrants may not be exercised until the first date on which the Issuer achieves a market valuation of $5.0 billion. As a result, none of the Warrants are currently exercisable. By virtue of their relationship as affiliated entities who have overlapping general partners and investment committee members, each of the AVP XIII Investment Committee Members and direct and indirect general partners of AVF XIII may be deemed to share the power to direct the AVF XIII Record Shares. Berns is the holder of options to purchase 113,513 shares of common stock, of which 53,483 are exercisable now and within the next 60 days, and 20,706 restricted stock units, of which 0 are exercisable now and within the next 60 days. Each Reporting Person disclaims beneficial ownership of the AVF XIII Record Shares except for the shares, if any, held of record by such Reporting Person. The percentage of outstanding Common Stock of the Issuer which may be deemed to be beneficially owned by each Reporting Person is set forth on Line 13 of such Reporting Person's cover sheet. Such percentage was calculated based on the 93,089,121 shares outstanding following the IPO, as reported by the Issuer in its Prospectus filed pursuant to Rule 424(b)(4) with the Securities and Exchange Commission on June 17, 2026, giving effect to the exercise of the underwriters' allotment, and includes vested options in the shares reported for Berns.
(b)	Regarding the number of shares as to which such person has: (i) sole power to vote or to direct the vote: See line 7 of cover sheets. (ii) shared power to vote or to direct the vote: See line 8 of cover sheets. (iii) sole power to dispose or to direct the disposition: See line 9 of cover sheets. (iv) shared power to dispose or to direct the disposition: See line 10 of cover sheets.
(c)	Except as set forth in this Schedule 13D, none of the Reporting Persons has effected any transaction in the Common Stock during the last 60 days.
(d)	No other person is known to have the right to receive or the power to direct the receipt of dividends from, or any proceeds from the sale of, shares beneficially owned by any of the Reporting Persons.
(e)	Not applicable.
Item 6.	Contracts, Arrangements, Understandings or Relationships With Respect to Securities of the Issuer
	Investor Rights Agreement AVF XIII is party to that certain Amended and Restated Investors' Rights Agreement, dated September 4, 2025 (the "Investor Rights Agreement"). Pursuant to the Investor Rights Agreement, the Issuer has granted to AVF XIII demand, piggyback and shelf registration rights with respect to shares of Common Stock held by AVF XIII. Such registration rights will terminate upon the earlier of (i) the occurrence of a deemed liquidation event, as defined in the Issuer's amended and restated certificate of incorporation, as currently in effect, (ii) such date after the completion of the IPO when AVF XIII (A) together with its affiliates (as determined under Rule 144 of the Securities Act) holds less than 1% of the Issuer's outstanding capital stock and (B) may immediately sell all registrable securities held by it pursuant to Rule 144 of the Securities Act without any volume limitations, or another similar exemption, during any three month period without registration, and (iii) the third anniversary of the IPO. Effective as of the closing of the IPO, the covenants relating to delivery of financial statements and inspection rights set forth in Section 3 and the rights of first offer were terminated. The foregoing description of the Investor Rights Agreement does not purport to be complete and is qualified in its entirety by reference to the full text of such agreement, which is filed as Exhibit 2 to this Schedule 13D and is incorporated herein by reference. Lock-Up Agreement AVF XIII has entered into a lock-up agreement with the underwriters of the IPO (the "Lock-Up Agreement") pursuant to which AVF XIII has agreed, subject to certain exceptions, not to offer, pledge, announce the intention to sell, sell, contract to sell, sell any option or contract to purchase, purchase any option or contract to sell, grant any option, right or warrant to purchase or otherwise dispose of, directly or indirectly, or enter into any swap or other agreement that transfers, in whole or in part, any of the economic consequences of ownership of the Common Stock for a period of 180 days after June 17, 2026, except with the prior written consent of J.P. Morgan Securities LLC, Jefferies LLC, Leerink Partners LLC and TD Securities (USA) LLC, subject to certain exceptions. The foregoing description of the Lock-Up Agreement does not purport to be complete and is qualified in its entirety by reference to the full text of such agreement, the form of which is filed as Exhibit 3 to this Schedule 13D and is incorporated herein by reference. Warrants In connection with the issuance of the Series B Preferred Stock, AVF XIII was issued by the Issuer a Warrant exercisable for 876,040 shares of Common Stock at an exercise price of $13.4135 per share (after giving effect to the Stock Split). The Warrant is exercisable, in whole or in part, only upon the first date on which the Issuer achieves a market valuation of $5.0 billion, and expires on September 4, 2035. The foregoing description of the Warrant does not purport to be complete and is qualified in its entirety by reference to the full text of such Warrant, which is filed as Exhibit 4 to this Schedule 13D and is incorporated herein by reference.
Item 7.	Material to be Filed as Exhibits.
	Exhibit 1 - Agreement of Joint Filing. Exhibit 2 - Amended and Restated Investors' Rights Agreement, dated September 4, 2025, as amended, by and among the Issuer and certain of its stockholders (incorporated by reference to Exhibit 4.4 to the Issuer's Registration Statement on Form S-1, filed with the Securities and Exchange Commission on May 26, 2026). Exhibit 3 - Form of Lock-Up Agreement (incorporated by reference to Exhibit D to the Form of Underwriting Agreement filed as Exhibit 1.1 to the Issuer's Registration Statement on Form S-1/A, filed with the Securities and Exchange Commission on June 11, 2026). Exhibit 4 - Warrant to Purchase Shares of Common Stock, by and between the Registrant and ARCH Venture Fund XIII, L.P., dated as of September 4, 2025 (incorporated by reference to Exhibit 4.2 to the Issuer's Registration Statement on Form S-1, filed with the Securities and Exchange Commission on May 26, 2026).

SIGNATURE

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

ARCH Venture Fund XIII, L.P.

Signature:	ARCH Venture Partners XIII, L.P.
Name/Title:	its General Partner
Date:	06/29/2026

Signature:	ARCH Venture Partners XIII, LLC
Name/Title:	its General Partner
Date:	06/29/2026

Signature:	/s/ Mark McDonnell*
Name/Title:	Mark McDonnell, as Attorney-in-Fact for Keith Crandell, Managing Director
Date:	06/29/2026

ARCH Venture Partners XIII, L.P.

Signature:	ARCH Venture Partners XIII, LLC
Name/Title:	its General Partner
Date:	06/29/2026

Signature:	/s/ Mark McDonnell*
Name/Title:	Mark McDonnell, as Attorney-in-Fact for Keith Crandell, Managing Director
Date:	06/29/2026

ARCH Venture Partners XIII, LLC

Signature:	/s/ Mark McDonnell*
Name/Title:	Mark McDonnell, as Attorney-in-Fact for Keith Crandell, Managing Director
Date:	06/29/2026

Robert Nelsen

Signature:	/s/ Mark McDonnell*
Name/Title:	Mark McDonnell, as Attorney-in-Fact for Robert Nelsen
Date:	06/29/2026

Keith Crandell

Signature:	/s/ Mark McDonnell*
Name/Title:	Mark McDonnell, as Attorney-in-Fact for Keith Crandell
Date:	06/29/2026

Kristina Burow

Signature:	/s/ Mark McDonnell*
Name/Title:	Mark McDonnell, as Attorney-in-Fact for Kristina Burow
Date:	06/29/2026

Steven Gillis

Signature:	/s/ Mark McDonnell*
Name/Title:	Mark McDonnell, as Attorney-in-Fact for Steven Gillis
Date:	06/29/2026

Paul Berns

Signature:	/s/ Mark McDonnell*
Name/Title:	Mark McDonnell, as Attorney-in-Fact for Paul Berns
Date:	06/29/2026

Comments accompanying signature:

This Schedule 13D was executed by Mark McDonnell pursuant to a Power of Attorney filed as Exhibit 24.1 to the Form 3 relating to the beneficial ownership of shares of Metsera, Inc. by the Reporting Persons filed with the Securities Exchange Commission on January 30, 2025 and incorporated herein in its entirety by reference.