LYEL · Lyell Immunopharma, Inc.

Reflects 2,857,490 shares of Common Stock beneficially owned by the Reporting Person immediately prior to the reported transaction, less the 10 shares sold.

Reflects 2,857,500 shares of Common Stock beneficially owned by the Reporting Person immediately prior to the reported transaction, less the 10 shares sold.

Represents shares of Common Stock transferred by the Reporting Person to Wuxiong, Inc. as broker commission in connection with the Upfront Payment (as such term is defined in the License Agreement, dated November 6, 2025, between the Issuer and the Reporting Person). The transaction was a transfer of securities for no cash consideration to the Reporting Person and is reported under transaction code J.

Reflects 2,933,500 shares of Common Stock beneficially owned by the Reporting Person immediately prior to the reported transaction, less the 76,000 shares transferred.

Represents shares of Common Stock transferred by the Reporting Person to LifeSci Advisors, LLC as broker commission in connection with the Upfront Payment (as such term is defined in the License Agreement, dated November 6, 2025, between the Issuer and the Reporting Person). The transaction was a transfer of securities for no cash consideration to the Reporting Person and is reported under transaction code J.

Reflects 3,000,000 shares of Common Stock beneficially owned by the Reporting Person immediately prior to the reported transaction, less the 66,500 shares transferred. All shares are held directly and registered in the name of the Reporting Person.

The option shares shall vest on the earlier of (a) the date of the next annual meeting of the stockholders that occurs following June 10, 2026 (or the date immediately prior to such date if the Reporting Person's service as a director ends at such annual meeting due to the Reporting Person's failure to be reelected or the Reporting Person not standing for re-election); or (b) the first anniversary of June 10, 2026, subject to the Reporting Person providing continuous service through such date.

The option shares shall vest on the earlier of (a) the date of the next annual meeting of the stockholders that occurs following June 10, 2026 (or the date immediately prior to such date if the Reporting Person's service as a director ends at such annual meeting due to the Reporting Person's failure to be reelected or the Reporting Person not standing for re-election); or (b) the first anniversary of June 10, 2026, subject to the Reporting Person providing continuous service through such date.

Shares automatically sold to cover tax withholding obligation from settlement of vested restricted stock units.

Includes 1,000 shares acquired on May 18, 2026 under the Issuer's 2021 Employee Stock Purchase Plan.

The option shares shall vest on the earlier of (a) the date of the next annual meeting of the stockholders that occurs following June 10, 2026 (or the date immediately prior to such date if the Reporting Person's service as a director ends at such annual meeting due to the Reporting Person's failure to be reelected or the Reporting Person not standing for re-election); or (b) the first anniversary of June 10, 2026, subject to the Reporting Person providing continuous service through such date.

The option shares shall vest on the earlier of (a) the date of the next annual meeting of the stockholders that occurs following June 10, 2026 (or the date immediately prior to such date if the Reporting Person's service as a director ends at such annual meeting due to the Reporting Person's failure to be reelected or the Reporting Person not standing for re-election); or (b) the first anniversary of June 10, 2026, subject to the Reporting Person providing continuous service through such date.

The option shares shall vest on the earlier of (a) the date of the next annual meeting of the stockholders that occurs following June 10, 2026 (or the date immediately prior to such date if the Reporting Person's service as a director ends at such annual meeting due to the Reporting Person's failure to be reelected or the Reporting Person not standing for re-election); or (b) the first anniversary of June 10, 2026, subject to the Reporting Person providing continuous service through such date.

The option shares shall vest on the earlier of (a) the date of the next annual meeting of the stockholders that occurs following June 10, 2026 (or the date immediately prior to such date if the Reporting Person's service as a director ends at such annual meeting due to the Reporting Person's failure to be reelected or the Reporting Person not standing for re-election); or (b) the first anniversary of June 10, 2026, subject to the Reporting Person providing continuous service through such date.

The option shares shall vest on the earlier of (a) the date of the next annual meeting of the stockholders that occurs following June 10, 2026 (or the date immediately prior to such date if the Reporting Person's service as a director ends at such annual meeting due to the Reporting Person's failure to be reelected or the Reporting Person not standing for re-election); or (b) the first anniversary of June 10, 2026, subject to the Reporting Person providing continuous service through such date.

Shares automatically sold to cover tax withholding obligation from settlement of vested restricted stock units.

The price reported above reflects the weighted average price of the shares sold. The sale price ranged from $18.91 to $19.30 per share. Upon request from the SEC staff, the Issuer, or a security holder of the Issuer, the Reporting Person will provide full information regarding the number of shares sold at each separate price within the range set forth in this Form 4.

Shares automatically sold to cover tax withholding obligation from settlement of vested restricted stock units.

The price reported above reflects the weighted average price of the shares sold. The sale price ranged from $18.91 to $19.15 per share. Upon request from the SEC staff, the Issuer, or a security holder of the Issuer, the Reporting Person will provide full information regarding the number of shares sold at each separate price within the range set forth in this Form 4.

Shares automatically sold to cover tax withholding obligation from settlement of vested restricted stock units.

The price reported above reflects the weighted average price of the shares sold. The sale price ranged from $18.91 to $19.30 per share. Upon request from the SEC staff, the Issuer, or a security holder of the Issuer, the Reporting Person will provide full information regarding the number of shares sold at each separate price within the range set forth in this Form 4.

Includes 1,000 shares acquired on May 18, 2026 under the Issuer's 2021 Employee Stock Purchase Plan.

Shares automatically sold to cover tax withholding obligation from settlement of vested restricted stock units.

The price reported above reflects the weighted average price of the shares sold. The sale price ranged from $18.91 to $19.30 per share. Upon request from the SEC staff, the Issuer, or a security holder of the Issuer, the Reporting Person will provide full information regarding the number of shares sold at each separate price within the range set forth in this Form 4.

Includes 188 shares acquired on May 18, 2026 under the Issuer's 2021 Employee Stock Purchase Plan.

25% of the option shares will vest on March 9, 2027, with the remaining option shares to vest in equal monthly installments over the following 36 months, subject to the reporting person providing service through the applicable vesting date.

These shares are directly held by ARCH Venture Fund XIII, L.P. ("ARCH XIII"). ARCH Venture Partners XIII, L.P. ("AVP XIII LP") is the general partner of ARCH XIII. ARCH Venture Partners XIII, LLC ("AVP XIII LLC") is the general partner of AVP XIII LP. Keith Crandell, Robert Nelsen, Kristina Burow, Paul Berns and Steven Gillis are members of the investment committee of AVP XIII LLC (the "AVP XIII LLC Committee Members"). Each of AVP XIII LP and AVP XIII LLC may be deemed to beneficially own the shares held by ARCH XIII, and each of the AVP XIII LLC Committee Members may be deemed to share the power to direct the disposition and vote of the shares held by ARCH XIII. Each of AVP XIII LP, AVP XIII LLC and the AVP XIII LLC Committee Members disclaims beneficial ownership except to the extent of their pecuniary interest therein, if any.

These shares are directly held by ARCH Venture Fund XIII, L.P. ("ARCH XIII"). ARCH Venture Partners XIII, L.P. ("AVP XIII LP") is the general partner of ARCH XIII. ARCH Venture Partners XIII, LLC ("AVP XIII LLC") is the general partner of AVP XIII LP. Keith Crandell, Robert Nelsen, Kristina Burow, Paul Berns and Steven Gillis are members of the investment committee of AVP XIII LLC (the "AVP XIII LLC Committee Members"). Each of AVP XIII LP and AVP XIII LLC may be deemed to beneficially own the shares held by ARCH XIII, and each of the AVP XIII LLC Committee Members may be deemed to share the power to direct the disposition and vote of the shares held by ARCH XIII. Each of AVP XIII LP, AVP XIII LLC and the AVP XIII LLC Committee Members disclaims beneficial ownership except to the extent of their pecuniary interest therein, if any.

Shares automatically sold to cover tax withholding obligation from settlement of performance-based vested restricted stock units.

The price reported above reflects the weighted average price of the shares sold. The sale price ranged from $23.3939 to $24.6305 per share. Upon request from the SEC staff, the Issuer, or a security holder of the Issuer, the Reporting Person will provide full information regarding the number of shares sold at each separate price within the range set forth in this Form 4.

Shares automatically sold to cover tax withholding obligation from settlement of performance-based vested restricted stock units.

The price reported above reflects the weighted average price of the shares sold. The sale price ranged from $23.3939 to $24.7850 per share. Upon request from the SEC staff, the Issuer, or a security holder of the Issuer, the Reporting Person will provide full information regarding the number of shares sold at each separate price within the range set forth in this Form 4.

Shares automatically sold to cover tax withholding obligation from settlement of performance-based vested restricted stock units.

The price reported above reflects the weighted average price of the shares sold. The sale price ranged from $23.3939 to $24.7850 per share. Upon request from the SEC staff, the Issuer, or a security holder of the Issuer, the Reporting Person will provide full information regarding the number of shares sold at each separate price within the range set forth in this Form 4.

Shares automatically sold to cover tax withholding obligation from settlement of vested restricted stock units.

Shares automatically sold to cover tax withholding obligation from settlement of vested restricted stock units.

Represents restricted stock units granted under the Issuer's 2021 Equity Incentive Plan. 12.5% of the total number of restricted stock units will vest on August 9, 2026, and thereafter an additional 1/16th of the total number of restricted stock units will vest quarterly thereafter, subject to the reporting person providing service through the applicable vesting date.

Twelve and one-half percent (12.5%) of the total number of shares of Common Stock subject to the option will be vested and exercisable on the date that is six (6) months after February 9, 2026 (the "Vesting Commencement Date") and thereafter, an additional one fortyeighth (1/48th) of the shares will become vested and exercisable monthly on the same day as the Vesting Commencement Date (or, if there is no such corresponding day for a given month, on the last day of such month), until the option has become vested and exercisable with respect to one hundred percent (100%) of the shares, subject to the Reporting Person providing service to the Issuer through each applicable vesting date.

Twelve and one-half percent (12.5%) of the total number of shares of Common Stock subject to the option will be vested and exercisable on the date that is six (6) months after February 9, 2026 (the "Vesting Commencement Date") and thereafter, an additional one fortyeighth (1/48th) of the shares will become vested and exercisable monthly on the same day as the Vesting Commencement Date (or, if there is no such corresponding day for a given month, on the last day of such month), until the option has become vested and exercisable with respect to one hundred percent (100%) of the shares, subject to the Reporting Person providing service to the Issuer through each applicable vesting date.

Shares automatically sold to cover tax withholding obligation from settlement of vested restricted stock units.

Shares automatically sold to cover tax withholding obligation from settlement of vested restricted stock units.

Twelve and one-half percent (12.5%) of the total number of shares of Common Stock subject to the option will be vested and exercisable on the date that is six (6) months after February 9, 2026 (the "Vesting Commencement Date") and thereafter, an additional one forty-eighth (1/48th) of the shares will become vested and exercisable monthly on the same day as the Vesting Commencement Date (or, if there is no such corresponding day for a given month, on the last day of such month), until the option has become vested and exercisable with respect to one hundred percent (100%) of the shares, subject to the Reporting Person providing service to the Issuer through each applicable vesting date.

Twelve and one-half percent (12.5%) of the total number of shares of Common Stock subject to the option will be vested and exercisable on the date that is six (6) months after February 9, 2026 (the "Vesting Commencement Date") and thereafter, an additional one fortyeighth (1/48th) of the shares will become vested and exercisable monthly on the same day as the Vesting Commencement Date (or, if there is no such corresponding day for a given month, on the last day of such month), until the option has become vested and exercisable with respect to one hundred percent (100%) of the shares, subject to the Reporting Person providing service to the Issuer through each applicable vesting date.

Twelve and one-half percent (12.5%) of the total number of shares of Common Stock subject to the option will be vested and exercisable on the date that is six (6) months after February 9, 2026 (the "Vesting Commencement Date") and thereafter, an additional one fortyeighth (1/48th) of the shares will become vested and exercisable monthly on the same day as the Vesting Commencement Date (or, if there is no such corresponding day for a given month, on the last day of such month), until the option has become vested and exercisable with respect to one hundred percent (100%) of the shares, subject to the Reporting Person providing service to the Issuer through each applicable vesting date.

Pursuant to performance-based restricted stock units granted to the reporting person on February 9, 2024, 4,000 shares were issued on the Transaction Date upon the achievement of certain performance criteria certified by the compensation committee of the Issuer's board of directors on the Transaction Date.

Includes 390 shares acquired on November 18, 2025 under the Issuer's 2021 Employee Stock Purchase Plan.

Pursuant to performance-based restricted stock units granted to the reporting person on February 9, 2024, 20,000 shares were issued on the Transaction Date upon the achievement of certain performance criteria certified by the compensation committee of the Issuer's board of directors on the Transaction Date.

Pursuant to performance-based restricted stock units granted to the reporting person on February 9, 2024, 4,000 shares were issued on the Transaction Date upon the achievement of certain performance criteria certified by the compensation committee of the Issuer's board of directors on the Transaction Date.

Includes 390 shares acquired on November 18, 2025 under the Issuer's 2021 Employee Stock Purchase Plan.

The price reported above reflects the weighted average price of the shares sold. The sale price ranged from $38.6643 to $38.6751 per share. Upon request from the SEC staff, the Issuer, or a security holder of the Issuer, the Reporting Person will provide full information regarding the number of shares sold at each separate price within the range set forth in this Form 4.

Shares automatically sold to cover tax withholding obligation from settlement of vested restricted stock units.

Shares automatically sold to cover tax withholding obligation from settlement of vested restricted stock units.

Shares automatically sold to cover tax withholding obligation from settlement of vested restricted stock units.

The price reported above reflects the weighted average price of the shares sold. The sale price ranged from $16.08 to $16.11 per share. Upon request from the SEC staff, the Issuer, or a security holder of the Issuer, the Reporting Person will provide full information regarding the number of shares sold at each separate price within the range set forth in this Form 4.

Shares automatically sold to cover tax withholding obligation from settlement of vested restricted stock units.

12.5% of the option shares will vest on April 27, 2026, with the remaining option shares to vest in equal monthly installments over the following forty-two months, subject to the reporting person providing service through the applicable vesting date.

12.5% of the option shares will vest on April 27, 2026, with the remaining option shares to vest in equal monthly installments over the following forty-two months, subject to the reporting person providing service through the applicable vesting date.

12.5% of the option shares will vest on April 27, 2026, with the remaining option shares to vest in equal monthly installments over the following forty-two months, subject to the reporting person providing service through the applicable vesting date.

Shares automatically sold to cover tax withholding obligation from settlement of vested restricted stock units.

The price reported above reflects the weighted average price of the shares sold. The sale price ranged from $10.49 to $10.64 per share. Upon request from the SEC staff, the Issuer, or a security holder of the Issuer, the Reporting Person will provide full information regarding the number of shares sold at each separate price within the range set forth in this Form 4.

Shares automatically sold to cover tax withholding obligation from settlement of vested restricted stock units.

The price reported above reflects the weighted average price of the shares sold. The sale price ranged from $10.49 to $10.64 per share. Upon request from the SEC staff, the Issuer, or a security holder of the Issuer, the Reporting Person will provide full information regarding the number of shares sold at each separate price within the range set forth in this Form 4.

Shares automatically sold to cover tax withholding obligation from settlement of vested restricted stock units.

The price reported above reflects the weighted average price of the shares sold. The sale price ranged from $10.49 to $10.64 per share. Upon request from the SEC staff, the Issuer, or a security holder of the Issuer, the Reporting Person will provide full information regarding the number of shares sold at each separate price within the range set forth in this Form 4.

Shares automatically sold to cover tax withholding obligation from settlement of vested restricted stock units.

The price reported above reflects the weighted average price of the shares sold. The sale price ranged from $10.49 to $10.64 per share. Upon request from the SEC staff, the Issuer, or a security holder of the Issuer, the Reporting Person will provide full information regarding the number of shares sold at each separate price within the range set forth in this Form 4.

Pursuant to performance-based restricted stock units granted to the reporting person on February 9, 2024, 4,000 shares were issued on the Transaction Date upon the achievement of certain performance criteria certified by the compensation committee of the Issuer's board of directors on the Transaction Date and 4,000 shares will be issued on August 20, 2026, subject to the reporting person providing service through such date.