# EDGAR Filing Document

**Accession Number:** 0001806952
**File Stem:** 0001012975-25-000768
**Filing Date:** 2025-11
**Character Count:** 35102
**Document Hash:** 5a191c2e382343373229b94883a20e36
**Contains OCR:** False
**Source Format:** 

## Filing Content

## Filing Summary
**0001012975-25-000768.hdr.sgml**: 20251114

**ACCESSION NUMBER**: 0001012975-25-000768

**CONFORMED SUBMISSION TYPE**: SCHEDULE 13G/A

**PUBLIC DOCUMENT COUNT**: 2

**FILED AS OF DATE**: 20251114

**DATE AS OF CHANGE**: 20251114

**SUBJECT COMPANY**: 

**COMPANY DATA:**
- **COMPANY CONFORMED NAME:** Lyell Immunopharma, Inc.
- **CENTRAL INDEX KEY:** 0001806952
- **STANDARD INDUSTRIAL CLASSIFICATION:** PHARMACEUTICAL PREPARATIONS [2834]
- **ORGANIZATION NAME:** 03 Life Sciences
- **EIN:** 833006753
- **STATE OF INCORPORATION:** DE
- **FISCAL YEAR END:** 1231

**FILING VALUES:**
- **FORM TYPE:** SCHEDULE 13G/A
- **SEC ACT:** 1934 Act
- **SEC FILE NUMBER:** 005-93402
- **FILM NUMBER:** 251487015

**BUSINESS ADDRESS:**
- **STREET 1:** 201 HASKINS WAY
- **CITY:** SOUTH SAN FRANCISCO
- **STATE:** CA
- **ZIP:** 94080
- **BUSINESS PHONE:** 650 695-0677

**MAIL ADDRESS:**
- **STREET 1:** 201 HASKINS WAY
- **CITY:** SOUTH SAN FRANCISCO
- **STATE:** CA
- **ZIP:** 94080
**FILED BY**: 

**COMPANY DATA:**
- **COMPANY CONFORMED NAME:** ARCH Venture Fund IX, L.P.
- **CENTRAL INDEX KEY:** 0001666306

**ORGANIZATION NAME:**
- **EIN:** 000000000
- **STATE OF INCORPORATION:** DE
- **FISCAL YEAR END:** 1231

**FILING VALUES:**
- **FORM TYPE:** SCHEDULE 13G/A

**BUSINESS ADDRESS:**
- **STREET 1:** 8755 W. HIGGINS ROAD, SUITE 1025
- **CITY:** CHICAGO
- **STATE:** IL
- **ZIP:** 60631
- **BUSINESS PHONE:** 773-380-6600

**MAIL ADDRESS:**
- **STREET 1:** 8755 W. HIGGINS ROAD, SUITE 1025
- **CITY:** CHICAGO
- **STATE:** IL
- **ZIP:** 60631

## Exhibit 99.1

**Exhibit 99.1**

**JOINT FILING AGREEMENT**

<br> Pursuant to Rule 13d-1-(k)(1) under the Securities Exchange Act of 1934, the undersigned hereby agree that only one statement containing the information required by Schedule 13G need be filed with respect to the ownership by each of the undersigned of shares of stock of Lyell Immunopharma, Inc.

This Agreement may be executed in any number of counterparts, each of which shall be deemed an original.

Dated: November 14, 2025

ARCH VENTURE FUND IX, L.P.

By: ARCH Venture Partners IX, L.P.

its General Partner

By: ARCH Venture Partners IX, LLC

its General Partner

By: <u>\*</u> 

Keith Crandell

Managing Director

ARCH VENTURE FUND IX OVERAGE, L.P.

By: ARCH Venture Partners IX Overage, L.P.

its General Partner

By: ARCH Venture Partners IX, LLC

its General Partner

By: <u>\*</u> 

Keith Crandell

Managing Director

ARCH VENTURE FUND XIII, L.P.

By: ARCH Venture Partners XIII L.P.

its General Partner

By: ARCH Venture Partners XIII, LLC

its General Partner

By: <u>\*</u> 

Keith Crandell

Managing Director

------

ARCH VENTURE PARTNERS IX, L.P.

By: ARCH Venture Partners IX, LLC

its General Partner

By: <u>\*</u> 

Keith Crandell

Managing Director

ARCH VENTURE PARTNERS IX OVERAGE, L.P.

By: ARCH Venture Partners IX, LLC

its General Partner

By: <u>\*</u> 

Keith Crandell

Managing Director

ARCH VENTURE PARTNERS IX, LLC

By: <u>\*</u> 

Keith Crandell

Managing Director

ARCH VENTURE PARTNERS XIII, L.P.

By: ARCH Venture Partners XIII, LLC

its General Partner

By: <u>\*</u> 

Keith Crandell

Managing Director

ARCH VENTURE PARTNERS XIII, LLC

By: <u>\*</u> 

Keith Crandell

Managing Director

------

 <u>\*</u> 

Keith Crandell

 <u>\*</u> 

Clinton Bybee

 <u>\*</u> 

Robert Nelsen

 <u>\*</u> 

Kristina Burrow

 <u>\*</u> 

Steven Gillis

 <u>\*</u> 

Paul Berns

\* By: /s/ Mark McDonnell

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Mark McDonnell as

&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;Attorney-in-Fact

\* This Agreement of Joint Filing 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.

IF " DOCVARIABLE "SWDocIDLocation" 3" = "3" " DOCPROPERTY "SWDocID" 156438745v1" "" 156438745v1

------

### UNITED STATES SECURITIES AND EXCHANGE COMMISSION
**Washington, D.C. 20549**

## SCHEDULE 13G

### Under the Securities Exchange Act of 1934

**(Amendment No. 3)**

**Issuer:** Lyell Immunopharma, Inc.

**Title of Class of Securities:** Common Stock par value $0.0001 per share

**CUSIP Number:** 55083R203

**Date of Event Which Requires Filing of this Statement:** 09/30/2025

**Check the appropriate box to designate the rule pursuant to which this Schedule is filed:**

- [ ] Rule 13d-1(b)

- [ ] Rule 13d-1(c)

- [x] Rule 13d-1(d)

---

| 1. | Names of Reporting Persons<br>ARCH Venture Fund IX, L.P. | Names of Reporting Persons<br>ARCH Venture Fund IX, L.P. |
|:---|:---|:---|:---|
| 2. | Check the Appropriate Box if a Member of a Group (See Instructions)<br>(a) [ ] (b) [ ] | Check the Appropriate Box if a Member of a Group (See Instructions)<br>(a) [ ] (b) [ ] |
| 3. | SEC Use Only | SEC Use Only |
| 4. | Citizenship or Place of Organization<br>DE | Citizenship or Place of Organization<br>DE |
| Number of<br>Shares<br>Beneficially<br>Owned by<br>Each<br>Reporting<br>Person<br>With | 5. | Sole Voting Power<br>0 |
| Number of<br>Shares<br>Beneficially<br>Owned by<br>Each<br>Reporting<br>Person<br>With | 6. | Shared Voting Power<br>2759072 |
| Number of<br>Shares<br>Beneficially<br>Owned by<br>Each<br>Reporting<br>Person<br>With | 7. | Sole Dispositive Power<br>0 |
| Number of<br>Shares<br>Beneficially<br>Owned by<br>Each<br>Reporting<br>Person<br>With | 8. | Shared Dispositive Power<br>2759072 |
| 9. | Aggregate Amount Beneficially Owned by Each Reporting Person<br>2759072 | Aggregate Amount Beneficially Owned by Each Reporting Person<br>2759072 |
| 10. | Check if the Aggregate Amount in Row (9) Excludes Certain Shares (See Instructions) [ ] | Check if the Aggregate Amount in Row (9) Excludes Certain Shares (See Instructions) [ ] |
| 11. | Percent of Class Represented by Amount in Row (9)<br>13.0% | Percent of Class Represented by Amount in Row (9)<br>13.0% |
| 12. | Type of Reporting Person (See Instructions)<br>PN | Type of Reporting Person (See Instructions)<br>PN |

---

| 1. | Names of Reporting Persons<br>ARCH Venture Fund IX Overage, L.P. | Names of Reporting Persons<br>ARCH Venture Fund IX Overage, L.P. |
|:---|:---|:---|:---|
| 2. | Check the Appropriate Box if a Member of a Group (See Instructions)<br>(a) [ ] (b) [ ] | Check the Appropriate Box if a Member of a Group (See Instructions)<br>(a) [ ] (b) [ ] |
| 3. | SEC Use Only | SEC Use Only |
| 4. | Citizenship or Place of Organization<br>DE | Citizenship or Place of Organization<br>DE |
| Number of<br>Shares<br>Beneficially<br>Owned by<br>Each<br>Reporting<br>Person<br>With | 5. | Sole Voting Power<br>0 |
| Number of<br>Shares<br>Beneficially<br>Owned by<br>Each<br>Reporting<br>Person<br>With | 6. | Shared Voting Power<br>2759072 |
| Number of<br>Shares<br>Beneficially<br>Owned by<br>Each<br>Reporting<br>Person<br>With | 7. | Sole Dispositive Power<br>0 |
| Number of<br>Shares<br>Beneficially<br>Owned by<br>Each<br>Reporting<br>Person<br>With | 8. | Shared Dispositive Power<br>2759072 |
| 9. | Aggregate Amount Beneficially Owned by Each Reporting Person<br>2759072 | Aggregate Amount Beneficially Owned by Each Reporting Person<br>2759072 |
| 10. | Check if the Aggregate Amount in Row (9) Excludes Certain Shares (See Instructions) [ ] | Check if the Aggregate Amount in Row (9) Excludes Certain Shares (See Instructions) [ ] |
| 11. | Percent of Class Represented by Amount in Row (9)<br>13.0% | Percent of Class Represented by Amount in Row (9)<br>13.0% |
| 12. | Type of Reporting Person (See Instructions)<br>PN | Type of Reporting Person (See Instructions)<br>PN |

---

| 1. | Names of Reporting Persons<br>ARCH Venture Fund XIII, L.P. | Names of Reporting Persons<br>ARCH Venture Fund XIII, L.P. |
|:---|:---|:---|:---|
| 2. | Check the Appropriate Box if a Member of a Group (See Instructions)<br>(a) [ ] (b) [ ] | Check the Appropriate Box if a Member of a Group (See Instructions)<br>(a) [ ] (b) [ ] |
| 3. | SEC Use Only | SEC Use Only |
| 4. | Citizenship or Place of Organization<br>DE | Citizenship or Place of Organization<br>DE |
| Number of<br>Shares<br>Beneficially<br>Owned by<br>Each<br>Reporting<br>Person<br>With | 5. | Sole Voting Power<br>0 |
| Number of<br>Shares<br>Beneficially<br>Owned by<br>Each<br>Reporting<br>Person<br>With | 6. | Shared Voting Power<br>2759072 |
| Number of<br>Shares<br>Beneficially<br>Owned by<br>Each<br>Reporting<br>Person<br>With | 7. | Sole Dispositive Power<br>0 |
| Number of<br>Shares<br>Beneficially<br>Owned by<br>Each<br>Reporting<br>Person<br>With | 8. | Shared Dispositive Power<br>2759072 |
| 9. | Aggregate Amount Beneficially Owned by Each Reporting Person<br>2759072 | Aggregate Amount Beneficially Owned by Each Reporting Person<br>2759072 |
| 10. | Check if the Aggregate Amount in Row (9) Excludes Certain Shares (See Instructions) [ ] | Check if the Aggregate Amount in Row (9) Excludes Certain Shares (See Instructions) [ ] |
| 11. | Percent of Class Represented by Amount in Row (9)<br>13.0% | Percent of Class Represented by Amount in Row (9)<br>13.0% |
| 12. | Type of Reporting Person (See Instructions)<br>PN | Type of Reporting Person (See Instructions)<br>PN |

---

| 1. | Names of Reporting Persons<br>ARCH Venture Partners IX, L.P. | Names of Reporting Persons<br>ARCH Venture Partners IX, L.P. |
|:---|:---|:---|:---|
| 2. | Check the Appropriate Box if a Member of a Group (See Instructions)<br>(a) [ ] (b) [ ] | Check the Appropriate Box if a Member of a Group (See Instructions)<br>(a) [ ] (b) [ ] |
| 3. | SEC Use Only | SEC Use Only |
| 4. | Citizenship or Place of Organization<br>DE | Citizenship or Place of Organization<br>DE |
| Number of<br>Shares<br>Beneficially<br>Owned by<br>Each<br>Reporting<br>Person<br>With | 5. | Sole Voting Power<br>0 |
| Number of<br>Shares<br>Beneficially<br>Owned by<br>Each<br>Reporting<br>Person<br>With | 6. | Shared Voting Power<br>2759072 |
| Number of<br>Shares<br>Beneficially<br>Owned by<br>Each<br>Reporting<br>Person<br>With | 7. | Sole Dispositive Power<br>0 |
| Number of<br>Shares<br>Beneficially<br>Owned by<br>Each<br>Reporting<br>Person<br>With | 8. | Shared Dispositive Power<br>2759072 |
| 9. | Aggregate Amount Beneficially Owned by Each Reporting Person<br>2759072 | Aggregate Amount Beneficially Owned by Each Reporting Person<br>2759072 |
| 10. | Check if the Aggregate Amount in Row (9) Excludes Certain Shares (See Instructions) [ ] | Check if the Aggregate Amount in Row (9) Excludes Certain Shares (See Instructions) [ ] |
| 11. | Percent of Class Represented by Amount in Row (9)<br>13.0% | Percent of Class Represented by Amount in Row (9)<br>13.0% |
| 12. | Type of Reporting Person (See Instructions)<br>PN | Type of Reporting Person (See Instructions)<br>PN |

---

| 1. | Names of Reporting Persons<br>ARCH Venture Partners IX Overage, L.P. | Names of Reporting Persons<br>ARCH Venture Partners IX Overage, L.P. |
|:---|:---|:---|:---|
| 2. | Check the Appropriate Box if a Member of a Group (See Instructions)<br>(a) [ ] (b) [ ] | Check the Appropriate Box if a Member of a Group (See Instructions)<br>(a) [ ] (b) [ ] |
| 3. | SEC Use Only | SEC Use Only |
| 4. | Citizenship or Place of Organization<br>DE | Citizenship or Place of Organization<br>DE |
| Number of<br>Shares<br>Beneficially<br>Owned by<br>Each<br>Reporting<br>Person<br>With | 5. | Sole Voting Power<br>0 |
| Number of<br>Shares<br>Beneficially<br>Owned by<br>Each<br>Reporting<br>Person<br>With | 6. | Shared Voting Power<br>2759072 |
| Number of<br>Shares<br>Beneficially<br>Owned by<br>Each<br>Reporting<br>Person<br>With | 7. | Sole Dispositive Power<br>0 |
| Number of<br>Shares<br>Beneficially<br>Owned by<br>Each<br>Reporting<br>Person<br>With | 8. | Shared Dispositive Power<br>2759072 |
| 9. | Aggregate Amount Beneficially Owned by Each Reporting Person<br>2759072 | Aggregate Amount Beneficially Owned by Each Reporting Person<br>2759072 |
| 10. | Check if the Aggregate Amount in Row (9) Excludes Certain Shares (See Instructions) [ ] | Check if the Aggregate Amount in Row (9) Excludes Certain Shares (See Instructions) [ ] |
| 11. | Percent of Class Represented by Amount in Row (9)<br>13.0% | Percent of Class Represented by Amount in Row (9)<br>13.0% |
| 12. | Type of Reporting Person (See Instructions)<br>PN | Type of Reporting Person (See Instructions)<br>PN |

---

| 1. | Names of Reporting Persons<br>ARCH Venture Partners IX, LLC | Names of Reporting Persons<br>ARCH Venture Partners IX, LLC |
|:---|:---|:---|:---|
| 2. | Check the Appropriate Box if a Member of a Group (See Instructions)<br>(a) [ ] (b) [ ] | Check the Appropriate Box if a Member of a Group (See Instructions)<br>(a) [ ] (b) [ ] |
| 3. | SEC Use Only | SEC Use Only |
| 4. | Citizenship or Place of Organization<br>DE | Citizenship or Place of Organization<br>DE |
| Number of<br>Shares<br>Beneficially<br>Owned by<br>Each<br>Reporting<br>Person<br>With | 5. | Sole Voting Power<br>0 |
| Number of<br>Shares<br>Beneficially<br>Owned by<br>Each<br>Reporting<br>Person<br>With | 6. | Shared Voting Power<br>2759072 |
| Number of<br>Shares<br>Beneficially<br>Owned by<br>Each<br>Reporting<br>Person<br>With | 7. | Sole Dispositive Power<br>0 |
| Number of<br>Shares<br>Beneficially<br>Owned by<br>Each<br>Reporting<br>Person<br>With | 8. | Shared Dispositive Power<br>2759072 |
| 9. | Aggregate Amount Beneficially Owned by Each Reporting Person<br>2759072 | Aggregate Amount Beneficially Owned by Each Reporting Person<br>2759072 |
| 10. | Check if the Aggregate Amount in Row (9) Excludes Certain Shares (See Instructions) [ ] | Check if the Aggregate Amount in Row (9) Excludes Certain Shares (See Instructions) [ ] |
| 11. | Percent of Class Represented by Amount in Row (9)<br>13.0% | Percent of Class Represented by Amount in Row (9)<br>13.0% |
| 12. | Type of Reporting Person (See Instructions)<br>OO | Type of Reporting Person (See Instructions)<br>OO |

---

| 1. | Names of Reporting Persons<br>ARCH Venture Partners XIII, L.P. | Names of Reporting Persons<br>ARCH Venture Partners XIII, L.P. |
|:---|:---|:---|:---|
| 2. | Check the Appropriate Box if a Member of a Group (See Instructions)<br>(a) [ ] (b) [ ] | Check the Appropriate Box if a Member of a Group (See Instructions)<br>(a) [ ] (b) [ ] |
| 3. | SEC Use Only | SEC Use Only |
| 4. | Citizenship or Place of Organization<br>DE | Citizenship or Place of Organization<br>DE |
| Number of<br>Shares<br>Beneficially<br>Owned by<br>Each<br>Reporting<br>Person<br>With | 5. | Sole Voting Power<br>0 |
| Number of<br>Shares<br>Beneficially<br>Owned by<br>Each<br>Reporting<br>Person<br>With | 6. | Shared Voting Power<br>2759072 |
| Number of<br>Shares<br>Beneficially<br>Owned by<br>Each<br>Reporting<br>Person<br>With | 7. | Sole Dispositive Power<br>0 |
| Number of<br>Shares<br>Beneficially<br>Owned by<br>Each<br>Reporting<br>Person<br>With | 8. | Shared Dispositive Power<br>2759072 |
| 9. | Aggregate Amount Beneficially Owned by Each Reporting Person<br>2759072 | Aggregate Amount Beneficially Owned by Each Reporting Person<br>2759072 |
| 10. | Check if the Aggregate Amount in Row (9) Excludes Certain Shares (See Instructions) [ ] | Check if the Aggregate Amount in Row (9) Excludes Certain Shares (See Instructions) [ ] |
| 11. | Percent of Class Represented by Amount in Row (9)<br>13.0% | Percent of Class Represented by Amount in Row (9)<br>13.0% |
| 12. | Type of Reporting Person (See Instructions)<br>PN | Type of Reporting Person (See Instructions)<br>PN |

---

| 1. | Names of Reporting Persons<br>ARCH Venture Partners XIII, LLC | Names of Reporting Persons<br>ARCH Venture Partners XIII, LLC |
|:---|:---|:---|:---|
| 2. | Check the Appropriate Box if a Member of a Group (See Instructions)<br>(a) [ ] (b) [ ] | Check the Appropriate Box if a Member of a Group (See Instructions)<br>(a) [ ] (b) [ ] |
| 3. | SEC Use Only | SEC Use Only |
| 4. | Citizenship or Place of Organization<br>DE | Citizenship or Place of Organization<br>DE |
| Number of<br>Shares<br>Beneficially<br>Owned by<br>Each<br>Reporting<br>Person<br>With | 5. | Sole Voting Power<br>0 |
| Number of<br>Shares<br>Beneficially<br>Owned by<br>Each<br>Reporting<br>Person<br>With | 6. | Shared Voting Power<br>2759072 |
| Number of<br>Shares<br>Beneficially<br>Owned by<br>Each<br>Reporting<br>Person<br>With | 7. | Sole Dispositive Power<br>0 |
| Number of<br>Shares<br>Beneficially<br>Owned by<br>Each<br>Reporting<br>Person<br>With | 8. | Shared Dispositive Power<br>2759072 |
| 9. | Aggregate Amount Beneficially Owned by Each Reporting Person<br>2759072 | Aggregate Amount Beneficially Owned by Each Reporting Person<br>2759072 |
| 10. | Check if the Aggregate Amount in Row (9) Excludes Certain Shares (See Instructions) [ ] | Check if the Aggregate Amount in Row (9) Excludes Certain Shares (See Instructions) [ ] |
| 11. | Percent of Class Represented by Amount in Row (9)<br>13.0% | Percent of Class Represented by Amount in Row (9)<br>13.0% |
| 12. | Type of Reporting Person (See Instructions)<br>OO | Type of Reporting Person (See Instructions)<br>OO |

---

| 1. | Names of Reporting Persons<br>Keith Crandell | Names of Reporting Persons<br>Keith Crandell |
|:---|:---|:---|:---|
| 2. | Check the Appropriate Box if a Member of a Group (See Instructions)<br>(a) [ ] (b) [ ] | Check the Appropriate Box if a Member of a Group (See Instructions)<br>(a) [ ] (b) [ ] |
| 3. | SEC Use Only | SEC Use Only |
| 4. | Citizenship or Place of Organization<br>X1 | Citizenship or Place of Organization<br>X1 |
| Number of<br>Shares<br>Beneficially<br>Owned by<br>Each<br>Reporting<br>Person<br>With | 5. | Sole Voting Power<br>0 |
| Number of<br>Shares<br>Beneficially<br>Owned by<br>Each<br>Reporting<br>Person<br>With | 6. | Shared Voting Power<br>2759072 |
| Number of<br>Shares<br>Beneficially<br>Owned by<br>Each<br>Reporting<br>Person<br>With | 7. | Sole Dispositive Power<br>0 |
| Number of<br>Shares<br>Beneficially<br>Owned by<br>Each<br>Reporting<br>Person<br>With | 8. | Shared Dispositive Power<br>2759072 |
| 9. | Aggregate Amount Beneficially Owned by Each Reporting Person<br>2759072 | Aggregate Amount Beneficially Owned by Each Reporting Person<br>2759072 |
| 10. | Check if the Aggregate Amount in Row (9) Excludes Certain Shares (See Instructions) [ ] | Check if the Aggregate Amount in Row (9) Excludes Certain Shares (See Instructions) [ ] |
| 11. | Percent of Class Represented by Amount in Row (9)<br>13.0% | Percent of Class Represented by Amount in Row (9)<br>13.0% |
| 12. | Type of Reporting Person (See Instructions)<br>IN | Type of Reporting Person (See Instructions)<br>IN |

---

| 1. | Names of Reporting Persons<br>Clinton Bybee | Names of Reporting Persons<br>Clinton Bybee |
|:---|:---|:---|:---|
| 2. | Check the Appropriate Box if a Member of a Group (See Instructions)<br>(a) [ ] (b) [ ] | Check the Appropriate Box if a Member of a Group (See Instructions)<br>(a) [ ] (b) [ ] |
| 3. | SEC Use Only | SEC Use Only |
| 4. | Citizenship or Place of Organization<br>X1 | Citizenship or Place of Organization<br>X1 |
| Number of<br>Shares<br>Beneficially<br>Owned by<br>Each<br>Reporting<br>Person<br>With | 5. | Sole Voting Power<br>0 |
| Number of<br>Shares<br>Beneficially<br>Owned by<br>Each<br>Reporting<br>Person<br>With | 6. | Shared Voting Power<br>1820634 |
| Number of<br>Shares<br>Beneficially<br>Owned by<br>Each<br>Reporting<br>Person<br>With | 7. | Sole Dispositive Power<br>0 |
| Number of<br>Shares<br>Beneficially<br>Owned by<br>Each<br>Reporting<br>Person<br>With | 8. | Shared Dispositive Power<br>1820634 |
| 9. | Aggregate Amount Beneficially Owned by Each Reporting Person<br>1820634 | Aggregate Amount Beneficially Owned by Each Reporting Person<br>1820634 |
| 10. | Check if the Aggregate Amount in Row (9) Excludes Certain Shares (See Instructions) [ ] | Check if the Aggregate Amount in Row (9) Excludes Certain Shares (See Instructions) [ ] |
| 11. | Percent of Class Represented by Amount in Row (9)<br>8.6% | Percent of Class Represented by Amount in Row (9)<br>8.6% |
| 12. | Type of Reporting Person (See Instructions)<br>IN | Type of Reporting Person (See Instructions)<br>IN |

---

| 1. | Names of Reporting Persons<br>Robert Nelsen | Names of Reporting Persons<br>Robert Nelsen |
|:---|:---|:---|:---|
| 2. | Check the Appropriate Box if a Member of a Group (See Instructions)<br>(a) [ ] (b) [ ] | Check the Appropriate Box if a Member of a Group (See Instructions)<br>(a) [ ] (b) [ ] |
| 3. | SEC Use Only | SEC Use Only |
| 4. | Citizenship or Place of Organization<br>X1 | Citizenship or Place of Organization<br>X1 |
| Number of<br>Shares<br>Beneficially<br>Owned by<br>Each<br>Reporting<br>Person<br>With | 5. | Sole Voting Power<br>0 |
| Number of<br>Shares<br>Beneficially<br>Owned by<br>Each<br>Reporting<br>Person<br>With | 6. | Shared Voting Power<br>2759072 |
| Number of<br>Shares<br>Beneficially<br>Owned by<br>Each<br>Reporting<br>Person<br>With | 7. | Sole Dispositive Power<br>0 |
| Number of<br>Shares<br>Beneficially<br>Owned by<br>Each<br>Reporting<br>Person<br>With | 8. | Shared Dispositive Power<br>2759072 |
| 9. | Aggregate Amount Beneficially Owned by Each Reporting Person<br>2759072 | Aggregate Amount Beneficially Owned by Each Reporting Person<br>2759072 |
| 10. | Check if the Aggregate Amount in Row (9) Excludes Certain Shares (See Instructions) [ ] | Check if the Aggregate Amount in Row (9) Excludes Certain Shares (See Instructions) [ ] |
| 11. | Percent of Class Represented by Amount in Row (9)<br>13.0% | Percent of Class Represented by Amount in Row (9)<br>13.0% |
| 12. | Type of Reporting Person (See Instructions)<br>IN | Type of Reporting Person (See Instructions)<br>IN |

---

| 1. | Names of Reporting Persons<br>Kristina Burow | Names of Reporting Persons<br>Kristina Burow |
|:---|:---|:---|:---|
| 2. | Check the Appropriate Box if a Member of a Group (See Instructions)<br>(a) [ ] (b) [ ] | Check the Appropriate Box if a Member of a Group (See Instructions)<br>(a) [ ] (b) [ ] |
| 3. | SEC Use Only | SEC Use Only |
| 4. | Citizenship or Place of Organization<br>X1 | Citizenship or Place of Organization<br>X1 |
| Number of<br>Shares<br>Beneficially<br>Owned by<br>Each<br>Reporting<br>Person<br>With | 5. | Sole Voting Power<br>0 |
| Number of<br>Shares<br>Beneficially<br>Owned by<br>Each<br>Reporting<br>Person<br>With | 6. | Shared Voting Power<br>2759072 |
| Number of<br>Shares<br>Beneficially<br>Owned by<br>Each<br>Reporting<br>Person<br>With | 7. | Sole Dispositive Power<br>0 |
| Number of<br>Shares<br>Beneficially<br>Owned by<br>Each<br>Reporting<br>Person<br>With | 8. | Shared Dispositive Power<br>2759072 |
| 9. | Aggregate Amount Beneficially Owned by Each Reporting Person<br>2759072 | Aggregate Amount Beneficially Owned by Each Reporting Person<br>2759072 |
| 10. | Check if the Aggregate Amount in Row (9) Excludes Certain Shares (See Instructions) [ ] | Check if the Aggregate Amount in Row (9) Excludes Certain Shares (See Instructions) [ ] |
| 11. | Percent of Class Represented by Amount in Row (9)<br>13.0% | Percent of Class Represented by Amount in Row (9)<br>13.0% |
| 12. | Type of Reporting Person (See Instructions)<br>IN | Type of Reporting Person (See Instructions)<br>IN |

---

| 1. | Names of Reporting Persons<br>Steven Gillis | Names of Reporting Persons<br>Steven Gillis |
|:---|:---|:---|:---|
| 2. | Check the Appropriate Box if a Member of a Group (See Instructions)<br>(a) [ ] (b) [ ] | Check the Appropriate Box if a Member of a Group (See Instructions)<br>(a) [ ] (b) [ ] |
| 3. | SEC Use Only | SEC Use Only |
| 4. | Citizenship or Place of Organization<br>X1 | Citizenship or Place of Organization<br>X1 |
| Number of<br>Shares<br>Beneficially<br>Owned by<br>Each<br>Reporting<br>Person<br>With | 5. | Sole Voting Power<br>0 |
| Number of<br>Shares<br>Beneficially<br>Owned by<br>Each<br>Reporting<br>Person<br>With | 6. | Shared Voting Power<br>2759072 |
| Number of<br>Shares<br>Beneficially<br>Owned by<br>Each<br>Reporting<br>Person<br>With | 7. | Sole Dispositive Power<br>0 |
| Number of<br>Shares<br>Beneficially<br>Owned by<br>Each<br>Reporting<br>Person<br>With | 8. | Shared Dispositive Power<br>2759072 |
| 9. | Aggregate Amount Beneficially Owned by Each Reporting Person<br>2759072 | Aggregate Amount Beneficially Owned by Each Reporting Person<br>2759072 |
| 10. | Check if the Aggregate Amount in Row (9) Excludes Certain Shares (See Instructions) [ ] | Check if the Aggregate Amount in Row (9) Excludes Certain Shares (See Instructions) [ ] |
| 11. | Percent of Class Represented by Amount in Row (9)<br>13.0% | Percent of Class Represented by Amount in Row (9)<br>13.0% |
| 12. | Type of Reporting Person (See Instructions)<br>IN | Type of Reporting Person (See Instructions)<br>IN |

---

| 1. | Names of Reporting Persons<br>Paul Berns | Names of Reporting Persons<br>Paul Berns |
|:---|:---|:---|:---|
| 2. | Check the Appropriate Box if a Member of a Group (See Instructions)<br>(a) [ ] (b) [ ] | Check the Appropriate Box if a Member of a Group (See Instructions)<br>(a) [ ] (b) [ ] |
| 3. | SEC Use Only | SEC Use Only |
| 4. | Citizenship or Place of Organization<br>X1 | Citizenship or Place of Organization<br>X1 |
| Number of<br>Shares<br>Beneficially<br>Owned by<br>Each<br>Reporting<br>Person<br>With | 5. | Sole Voting Power<br>0 |
| Number of<br>Shares<br>Beneficially<br>Owned by<br>Each<br>Reporting<br>Person<br>With | 6. | Shared Voting Power<br>938438 |
| Number of<br>Shares<br>Beneficially<br>Owned by<br>Each<br>Reporting<br>Person<br>With | 7. | Sole Dispositive Power<br>0 |
| Number of<br>Shares<br>Beneficially<br>Owned by<br>Each<br>Reporting<br>Person<br>With | 8. | Shared Dispositive Power<br>938438 |
| 9. | Aggregate Amount Beneficially Owned by Each Reporting Person<br>938438 | Aggregate Amount Beneficially Owned by Each Reporting Person<br>938438 |
| 10. | Check if the Aggregate Amount in Row (9) Excludes Certain Shares (See Instructions) [ ] | Check if the Aggregate Amount in Row (9) Excludes Certain Shares (See Instructions) [ ] |
| 11. | Percent of Class Represented by Amount in Row (9)<br>4.4% | Percent of Class Represented by Amount in Row (9)<br>4.4% |
| 12. | Type of Reporting Person (See Instructions)<br>IN | Type of Reporting Person (See Instructions)<br>IN |

---

**Item 1(a). Name of Issuer:**
Lyell Immunopharma, Inc.

**Item 1(b). Address of Issuer's Principal Executive Offices:**
201 Haskins Way, South San Francisco, CA 94080

**Item 2(a). Name of Person Filing:**
ARCH Venture Fund IX, L.P. ("AVF IX"); ARCH Venture Partners IX, L.P. ("AVP IX LP"); ARCH Venture Partners IX, LLC ("AVP IX LLC"); ARCH Venture Fund IX Overage, L.P. ("AVF IX Overage"); ARCH Venture Partners IX Overage, L.P. ("AVF IX Overage GP"); ARCH Venture Fund XIII, L.P. ("AVF XIII"); ARCH Venture Partners XIII, L.P. ("AVP XIII LP"); ARCH Venture Partners XIII, LLC ("AVP XIII LLC") (collectively, the "Reporting Entities" and individually, each a "Reporting Entity"); and Keith Crandell ("Crandell"), Robert Nelsen ("Nelsen") and Clinton Bybee ("Bybee") (collectively, the "IX Managing Directors" and individually, each a "IX Managing Director"), Steven Gillis ("Gillis") and Kristina Burow ("Burow"), along with Nelsen and Crandell, collectively the "IX Investment Committee" and individually "IX Committee Members"; and Paul Berns ("Berns"), along with Nelsen, Crandell, Gillis, and Burow, collectively the "XIII Investment Committee" and individually "XIII Committee Members". The Reporting Entities, IX Managing Directors, IX Committee Members, and XIII Committee Members collectively are referred to as the "Reporting Persons".

**Item 2(b). Address of Principal Business Office:**
8755 W. Higgins Avenue, Suite 1025, Chicago, IL 60631

**Item 2(c). Citizenship:**
Each of AVF IX, AVF IX LP, AVF IX Overage, AVF IX Overage GP, AVF XIII and AVF XIII LP are limited partnerships organized under the laws of the State of Delaware. AVP IX LLC and AVP XIII LLC are each a limited liability company organized under the laws of the State of Delaware.  Each Managing Director is a US citizen.

**Item 2(d). Title of Class of Securities:**
Common Stock par value $0.0001 per share

**Item 2(e). CUSIP Number:**
55083R203

**Item 3. If this statement is filed pursuant to §§ 240.13d-1(b) or 240.13d-2(b) or (c), check whether the person filing is a:**

(a) [ ] Broker or dealer registered under section 15 of the Act (15 U.S.C. 78o).

(b) [ ] Bank as defined in section 3(a)(6) of the Act (15 U.S.C. 78c).

(c) [ ] Insurance company as defined in section 3(a)(19) of the Act (15 U.S.C. 78c).

(d) [ ] Investment company registered under section 8 of the Investment Company Act of 1940 (15 U.S.C. 80a-8).

(e) [ ] An investment adviser in accordance with § 240.13d-1(b)(1)(ii)(E);

(f) [ ] An employee benefit plan or endowment fund in accordance with § 240.13d-1(b)(1)(ii)(F);

(g) [ ] A parent holding company or control person in accordance with § 240.13d-1(b)(1)(ii)(G);

(h) [ ] A savings associations as defined in Section 3(b) of the Federal Deposit Insurance Act (12 U.S.C. 1813);

(i) [ ] A church plan that is excluded from the definition of an investment company under section 3(c)(14) of the Investment Company Act of 1940 (15 U.S.C. 80a-3);

(j) [ ] A non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J), if filing as a non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J), please specify the type of institution:

(k) [ ] Group, in accordance with Rule 240.13d-1(b)(1)(ii)(K).

**Item 4. Ownership:**

**(a) Amount beneficially owned:**

AVF IX is the record owner of 910,317 shares of Common Stock (the "AVF IX Shares") as of September 30, 2025. AVP IX LP, as the sole general partner of AVF IX, may be deemed to beneficially own the AVF IX Shares.
AVF IX Overage is the record owner of 910,317 shares of Common Stock (the "AVF IX Overage Shares") as of September 30, 2025. AVF IX Overage GP, as the sole general partner of AVF IX Overage, may be deemed to beneficially own the AVF IX Overage Shares, combined with AVF IX Shares (the "IX Record Shares").
AVF XIII is the record owner of 938,438 shares of Common Stock (the "XIII Record Shares") as of September 30, 2025. AVP XIII LP, as the sole general partner of AVF XIII, may be deemed to beneficially own the XIII Record Shares.
AVP IX LLC, as the sole general partner of AVP IX LP and AVF IX Overage GP, may be deemed to beneficially own the IX Record Shares. As managing directors and investment committee members of AVP IX LLC, each IX Managing Director and IX Committee Members may also be deemed to share the power to direct the disposition and vote of the IX Record Shares.
AVP XIII LLC, as the sole general partner of AVP XIII LP, may be deemed to beneficially own the XIII Record Shares. As investment committee members of AVP XIII LLC, XIII Committee Members may also be deemed to share the power to direct the disposition and vote of the XIII Record Shares.
The information required by Item 4(b) is incorporated by reference to Row 11 of the cover pages hereto. The percentages set forth on the cover sheet for each Reporting Person is based upon 21,218,217 shares of common stock outstanding as of November 10, 2025, as reported on the Issuer's Quarterly Report on Form 10-Q as filed with the Securities and Exchange Commission on November 12, 2025.

**(b) Percent of class:**

See row 11 of the cover pages.

**(c) Number of shares as to which the person has:**

**(i) Sole power to vote or to direct the vote:**

See row 5 of the cover pages.

**(ii) Shared power to vote or to direct the vote:**

See row 6 of the cover pages.

**(iii) Sole power to dispose or to direct the disposition of:**

See row 7 of the cover pages.

**(iv) Shared power to dispose or to direct the disposition of:**

See row 8 of the cover pages.

**Item 5. Ownership of Five Percent or Less of a Class.**

[x] If this statement is being filed to report the fact that as of the date hereof the reporting person has ceased to be the beneficial owner of more than five percent of the class of securities, check the following.

**Item 6. Ownership of More than 5 Percent on Behalf of Another Person.**

Not Applicable

**Item 7. Identification and Classification of the Subsidiary**

Not Applicable

**Item 8. Identification and Classification of Members of the Group**

Not Applicable

**Item 9. Notice of Dissolution of Group**

Not Applicable

**Item 10. Certification:**

—

### 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 IX, L.P.**

**Date:** 11/14/2025

**By:** /s/ ARCH Venture Partners IX, L.P.

**Name & Title:** its General Partner

**ARCH Venture Fund IX Overage, L.P.**

**Date:** 11/14/2025

**By:** /s/ ARCH Venture Partners IX Overage, L.P.

**Name & Title:** its General Partner

**ARCH Venture Fund XIII, L.P.**

**Date:** 11/14/2025

**By:** /s/ ARCH Venture Partners XIII, L.P.

**Name & Title:** its General Partner

**ARCH Venture Partners IX, L.P.**

**Date:** 11/14/2025

**By:** /s/ ARCH Venture Partners IX, LLC

**Name & Title:** its General Partner

**ARCH Venture Partners IX Overage, L.P.**

**Date:** 11/14/2025

**By:** /s/ ARCH Venture Partners IX, LLC

**Name & Title:** its General Partner

**ARCH Venture Partners IX, LLC**

**Date:** 11/14/2025

**By:** /s/ Mark McDonnell

**Name & Title:** Mark McDonnell as Attorney-in-Fact for Keith Crandell, Managing Director

**ARCH Venture Partners XIII, L.P.**

**Date:** 11/14/2025

**By:** /s/ ARCH Venture Partners XIII, LLC

**Name & Title:** its General Partner

**ARCH Venture Partners XIII, LLC**

**Date:** 11/14/2025

**By:** /s/ Mark McDonnell

**Name & Title:** Mark McDonnell as Attorney-in-Fact for Keith Crandell, Managing Director

**Keith Crandell**

**Date:** 11/14/2025

**By:** /s/ Mark McDonnell

**Name & Title:** Mark McDonnell as Attorney-in-Fact for Keith Crandell

**Clinton Bybee**

**Date:** 11/14/2025

**By:** /s/ Mark McDonnell

**Name & Title:** Mark McDonnell as Attorney-in-Fact for Clinton Bybee

**Robert Nelsen**

**Date:** 11/14/2025

**By:** /s/ Mark McDonnell

**Name & Title:** Mark McDonnell as Attorney-in-Fact for mark McDonnell

**Kristina Burow**

**Date:** 11/14/2025

**By:** /s/ Mark McDonnell

**Name & Title:** Mark McDonnell as Attorney-in-Fact for Kristina Burrow

**Steven Gillis**

**Date:** 11/14/2025

**By:** /s/ Mark McDonnell

**Name & Title:** Mark McDonnell as Attorney-in-Fact for Steven Gillis

**Paul Berns**

**Date:** 11/14/2025

**By:** /s/ Mark McDonnell

**Name & Title:** Mark McDonnell as Attorney-in-Fact for Paul Berns