ANNX · Annexon, Inc.

1/36th of the shares subject to the option vest on each monthly anniversary measured from August 10, 2026 (the "Vesting Commencement Date"), such that 100% of the shares subject to the option will be fully vested and exercisable on the third anniversary of the Vesting Commencement Date, subject to Reporting Person's continuous service as a director on each such vesting date.

The underlying shares subject to the option vest and become exercisable as to 100% of the total number of shares subject to the option on the earlier of (i) the first anniversary of June 11, 2026 or (ii) the next Annual Meeting following June 11, 2026, subject to Reporting Person's continuous service as a director until such vesting date.

The underlying shares subject to the option vest and become exercisable as to 100% of the total number of shares subject to the option on the earlier of (i) the first anniversary of June 11, 2026 or (ii) the next Annual Meeting following June 11, 2026, subject to Reporting Person's continuous service as a director until such vesting date.

The shares subject to the option are fully vested and exercisable.

The underlying shares subject to the option vest and become exercisable as to 100% of the total number of shares subject to the option on the earlier of (i) the first anniversary of June 11, 2026 or (ii) the next Annual Meeting following June 11, 2026, subject to Reporting Person's continuous service as a director until such vesting date.

The underlying shares subject to the option vest and become exercisable as to 100% of the total number of shares subject to the option on the earlier of (i) the first anniversary of June 11, 2026 or (ii) the next Annual Meeting following June 11, 2026, subject to Reporting Person's continuous service as a director until such vesting date.

The underlying shares subject to the option vest and become exercisable as to 100% of the total number of shares subject to the option on the earlier of (i) the first anniversary of June 11, 2026 or (ii) the next Annual Meeting following June 11, 2026, subject to Reporting Person's continuous service as a director until such vesting date.

The underlying shares subject to the option vest and become exercisable as to 100% of the total number of shares subject to the option on the earlier of (i) the first anniversary of June 11, 2026 or (ii) the next Annual Meeting following June 11, 2026, subject to Reporting Person's continuous service as a director until such vesting date.

All shares were purchased by Alerce Medical Technology Partners, L.P. ("Alerce Medical"). The Reporting Person has sole voting and dispositive power over the shares held by Alerce Medical. The Reporting Person disclaims beneficial ownership of the shares except to the extent of his pecuniary interest therein.

As of May 28, 2026, includes (a) 240,000 shares that are held by the Muneer A. Satter Revocable Trust for which the Reporting Person serves as trustee and, in such capacity, has sole voting and dispositive power over all such shares, (b) 567,240 shares that are held by various other trusts and entities for which the Reporting Person serves as trustee, investment advisor or manager, as applicable, and, in each such capacity, has sole voting and dispositive power over all such shares, (c) 1,147,738 shares that are held by Satter Medical Technology Partners, L.P. for which the Reporting Person has sole voting and dispositive power over all such shares and (d) 8,387,156 shares that are held by Alerce Medical for which the Reporting Person has sole voting and dispositive power over all such shares. The Reporting Person disclaims beneficial ownership of all shares included under (b), (c) and (d) of this footnote, except to the extent of his pecuniary interest therein.

The transactions reported herein were effected pursuant to the Reporting Person's Rule 10b5-1 trading plan, adopted December 8, 2025.

The transactions reported herein were effected pursuant to the Reporting Person's Rule 10b5-1 trading plan, adopted December 8, 2025.

The transactions reported herein were effected pursuant to the Reporting Person's Rule 10b5-1 trading plan, adopted December 8, 2025.

The shares were sold to cover tax withholding obligations in connection with the vesting of restricted stock units ("RSUs").

This transaction was executed in multiple trades in prices ranging from $5.35 to $5.57, inclusive. The price reported in Column 4 above reflects the weighted average sale price. The Reporting Person hereby undertakes to provide to the Securities and Exchange Commission staff, the Issuer, or a security holder of the Issuer, upon request, full information regarding the number of shares sold at each respective price within the range set forth in this footnote.

The shares were sold to cover tax withholding obligations in connection with the vesting of restricted stock units ("RSUs").

This transaction was executed in multiple trades in prices ranging from $5.36 to $5.57, inclusive. The price reported in Column 4 above reflects the weighted average sale price. The Reporting Person hereby undertakes to provide to the Securities and Exchange Commission staff, the Issuer, or a security holder of the Issuer, upon request, full information regarding the number of shares sold at each respective price within the range set forth in this footnote.

The shares were sold to cover tax withholding obligations in connection with the vesting of restricted stock units ("RSUs").

This transaction was executed in multiple trades in prices ranging from $5.34 to $5.57, inclusive. The price reported in Column 4 above reflects the weighted average sale price. The Reporting Person hereby undertakes to provide to the Securities and Exchange Commission staff, the Issuer, or a security holder of the Issuer, upon request, full information regarding the number of shares sold at each respective price within the range set forth in this footnote.

The shares were sold to cover tax withholding obligations in connection with the vesting of restricted stock units ("RSUs").

This transaction was executed in multiple trades in prices ranging from $5.35 to $5.56, inclusive. The price reported in Column 4 above reflects the weighted average sale price. The Reporting Person hereby undertakes to provide to the Securities and Exchange Commission staff, the Issuer, or a security holder of the Issuer, upon request, full information regarding the number of shares sold at each respective price within the range set forth in this footnote.

The shares were sold to cover tax withholding obligations in connection with the vesting of restricted stock units ("RSUs").

This transaction was executed in multiple trades in prices ranging from $5.36 to $5.57, inclusive. The price reported in Column 4 above reflects the weighted average sale price. The Reporting Person hereby undertakes to provide to the Securities and Exchange Commission staff, the Issuer, or a security holder of the Issuer, upon request, full information regarding the number of shares sold at each respective price within the range set forth in this footnote.

1/48th of the shares subject to the option vest on each monthly anniversary measured from February 19, 2026 (the "Vesting Commencement Date"), such that 100% of the shares subject to the option will be fully vested and exercisable on the fourth anniversary of the Vesting Commencement Date, subject to Reporting Person's continuous service with the Issuer as of each such vesting date.

Constitute restricted stock units ("RSUs") for which the Reporting Person is entitled to receive one (1) share of Common Stock for each RSU upon vesting. 1/3rd of the RSUs vest annually on February 19 of each year, with the first 1/3rd vesting on February 19, 2027, subject to Reporting Person's continuous service with the Issuer as of each such vesting date.

Constitute restricted stock units ("RSUs") for which the Reporting Person is entitled to receive one (1) share of Common Stock for each RSU upon vesting. 1/3rd of the RSUs vest annually on February 19 of each year, with the first 1/3rd vesting on February 19, 2027, subject to Reporting Person's continuous service with the Issuer as of each such vesting date.

Constitute restricted stock units ("RSUs") for which the Reporting Person is entitled to receive one (1) share of Common Stock for each RSU upon vesting. 1/3rd of the RSUs vest annually on February 19 of each year, with the first 1/3rd vesting on February 19, 2027, subject to Reporting Person's continuous service with the Issuer as of each such vesting date.

1/48th of the shares subject to the option vest on each monthly anniversary measured from February 19, 2026 (the "Vesting Commencement Date"), such that 100% of the shares subject to the option will be fully vested and exercisable on the fourth anniversary of the Vesting Commencement Date, subject to Reporting Person's continuous service with the Issuer as of each such vesting date.

1/48th of the shares subject to the option vest on each monthly anniversary measured from February 19, 2026 (the "Vesting Commencement Date"), such that 100% of the shares subject to the option will be fully vested and exercisable on the fourth anniversary of the Vesting Commencement Date, subject to Reporting Person's continuous service with the Issuer as of each such vesting date.

1/48th of the shares subject to the option vest on each monthly anniversary measured from February 19, 2026 (the "Vesting Commencement Date"), such that 100% of the shares subject to the option will be fully vested and exercisable on the fourth anniversary of the Vesting Commencement Date, subject to Reporting Person's continuous service with the Issuer as of each such vesting date.

1/48th of the shares subject to the option vest on each monthly anniversary measured from February 19, 2026 (the "Vesting Commencement Date"), such that 100% of the shares subject to the option will be fully vested and exercisable on the fourth anniversary of the Vesting Commencement Date, subject to Reporting Person's continuous service with the Issuer as of each such vesting date.

1/48th of the shares subject to the option vest on each monthly anniversary measured from February 19, 2026 (the "Vesting Commencement Date"), such that 100% of the shares subject to the option will be fully vested and exercisable on the fourth anniversary of the Vesting Commencement Date, subject to Reporting Person's continuous service with the Issuer as of each such vesting date.

Constitute restricted stock units ("RSUs") for which the Reporting Person is entitled to receive one (1) share of Common Stock for each RSU upon vesting. 1/3rd of the RSUs vest annually on February 19 of each year, with the first 1/3rd vesting on February 19, 2027, subject to Reporting Person's continuous service with the Issuer as of each such vesting date.

Constitute restricted stock units ("RSUs") for which the Reporting Person is entitled to receive one (1) share of Common Stock for each RSU upon vesting. 1/3rd of the RSUs vest annually on February 19 of each year, with the first 1/3rd vesting on February 19, 2027, subject to Reporting Person's continuous service with the Issuer as of each such vesting date.

The shares were sold to cover tax withholding obligations in connection with the vesting of restricted stock units ("RSUs").

This transaction was executed in multiple trades in prices ranging from $4.925 to $5.155, inclusive. The price reported in Column 4 above reflects the weighted average sale price. The Reporting Person hereby undertakes to provide to the Securities and Exchange Commission staff, the Issuer, or a security holder of the Issuer, upon request, full information regarding the number of shares sold at each respective price within the range set forth in this footnote.

The shares were sold to cover tax withholding obligations in connection with the vesting of restricted stock units ("RSUs").

This transaction was executed in multiple trades in prices ranging from $4.93 to $5.16, inclusive. The price reported in Column 4 above reflects the weighted average sale price. The Reporting Person hereby undertakes to provide to the Securities and Exchange Commission staff, the Issuer, or a security holder of the Issuer, upon request, full information regarding the number of shares sold at each respective price within the range set forth in this footnote.

The shares were sold to cover tax withholding obligations in connection with the vesting of restricted stock units ("RSUs").

This transaction was executed in multiple trades in prices ranging from $4.925 to $5.17, inclusive. The price reported in Column 4 above reflects the weighted average sale price. The Reporting Person hereby undertakes to provide to the Securities and Exchange Commission staff, the Issuer, or a security holder of the Issuer, upon request, full information regarding the number of shares sold at each respective price within the range set forth in this footnote.

The shares were sold to cover tax withholding obligations in connection with the vesting of restricted stock units ("RSUs").

This transaction was executed in multiple trades in prices ranging from $4.925 to $5.17, inclusive. The price reported in Column 4 above reflects the weighted average sale price. The Reporting Person hereby undertakes to provide to the Securities and Exchange Commission staff, the Issuer, or a security holder of the Issuer, upon request, full information regarding the number of shares sold at each respective price within the range set forth in this footnote.

The shares were sold to cover tax withholding obligations in connection with the vesting of restricted stock units ("RSUs").

This transaction was executed in multiple trades in prices ranging from $4.93 to $5.16, inclusive. The price reported in Column 4 above reflects the weighted average sale price. The Reporting Person hereby undertakes to provide to the Securities and Exchange Commission staff, the Issuer, or a security holder of the Issuer, upon request, full information regarding the number of shares sold at each respective price within the range set forth in this footnote.

The transactions reported herein were effected pursuant to the Reporting Person's Rule 10b5-1 trading plan, adopted March 17, 2025.

The transactions reported herein were effected pursuant to the Reporting Person's Rule 10b5-1 trading plan, adopted March 17, 2025.

This transaction was executed in multiple trades in prices ranging from $4.43 to $4.50, inclusive. The price reported in Column 4 above reflects the weighted average purchase price. The Reporting Person hereby undertakes to provide to the Securities and Exchange Commission staff, the Issuer, or a security holder of the Issuer, upon request, full information regarding the number of shares purchased at each respective price within the range set forth in this footnote.

This transaction was executed in multiple trades in prices ranging from $4.165 to $4.215, inclusive. The price reported in Column 4 above reflects the weighted average purchase price. The Reporting Person hereby undertakes to provide to the Securities and Exchange Commission staff, the Issuer, or a security holder of the Issuer, upon request, full information regarding the number of shares purchased at each respective price within the range set forth in this footnote.

These shares are held by The Park Family Revocable Trust. The Reporting Person and her spouse are co-trustees of the trust.

All shares were purchased by Alerce Medical Technology Partners, L.P. ("Alerce Medical"). The Reporting Person has sole voting and dispositive power over the shares held by Alerce Medical. The Reporting Person disclaims beneficial ownership of the shares except to the extent of his pecuniary interest therein.

This transaction was executed in multiple trades in prices ranging from $4.165 to $4.415, inclusive. The price reported in Column 4 above reflects the weighted average purchase price. The Reporting Person hereby undertakes to provide to the Securities and Exchange Commission staff, the Issuer, or a security holder of the Issuer, upon request, full information regarding the number of shares purchased at each respective price within the range set forth in this footnote.

As of November 21, 2025, includes (a) 240,000 shares that are held by the Muneer A. Satter Revocable Trust for which the Reporting Person serves as trustee and, in such capacity, has sole voting and dispositive power over all such shares, (b) 567,240 shares that are held by various other trusts and entities for which the Reporting Person serves as trustee, investment advisor or manager, as applicable, and, in each such capacity, has sole voting and dispositive power over all such shares, (c) 1,147,738 shares that are held by Satter Medical Technology Partners, L.P. for which the Reporting Person has sole voting and dispositive power over all such shares and (d) 7,773,659 shares that are held by Alerce Medical for which the Reporting Person has sole voting and dispositive power over all such shares. The Reporting Person disclaims beneficial ownership of all shares included under (b), (c) and (d) of this footnote, except to the extent of his pecuniary interest therein.

All shares were purchased by Alerce Medical Technology Partners, L.P. ("Alerce Medical"). The Reporting Person has sole voting and dispositive power over the shares held by Alerce Medical. The Reporting Person disclaims beneficial ownership of the shares except to the extent of his pecuniary interest therein.

This transaction was executed in multiple trades in prices ranging from $4.25 to $5.065, inclusive. The price reported in Column 4 above reflects the weighted average purchase price. The Reporting Person hereby undertakes to provide to the Securities and Exchange Commission staff, the Issuer, or a security holder of the Issuer, upon request, full information regarding the number of shares purchased at each respective price within the range set forth in this footnote.

As of November 21, 2025, includes (a) 240,000 shares that are held by the Muneer A. Satter Revocable Trust for which the Reporting Person serves as trustee and, in such capacity, has sole voting and dispositive power over all such shares, (b) 567,240 shares that are held by various other trusts and entities for which the Reporting Person serves as trustee, investment advisor or manager, as applicable, and, in each such capacity, has sole voting and dispositive power over all such shares, (c) 1,147,738 shares that are held by Satter Medical Technology Partners, L.P. for which the Reporting Person has sole voting and dispositive power over all such shares and (d) 7,773,659 shares that are held by Alerce Medical for which the Reporting Person has sole voting and dispositive power over all such shares. The Reporting Person disclaims beneficial ownership of all shares included under (b), (c) and (d) of this footnote, except to the extent of his pecuniary interest therein.

All shares were purchased by Alerce Medical Technology Partners, L.P. ("Alerce Medical"). The Reporting Person has sole voting and dispositive power over the shares held by Alerce Medical. The Reporting Person disclaims beneficial ownership of the shares except to the extent of his pecuniary interest therein.

This transaction was executed in multiple trades in prices ranging from $3.57 to $4.19, inclusive. The price reported in Column 4 above reflects the weighted average purchase price. The Reporting Person hereby undertakes to provide to the Securities and Exchange Commission staff, the Issuer, or a security holder of the Issuer, upon request, full information regarding the number of shares purchased at each respective price within the range set forth in this footnote.

As of November 19, 2025, includes (a) 240,000 shares that are held by the Muneer A. Satter Revocable Trust for which the Reporting Person serves as trustee and, in such capacity, has sole voting and dispositive power over all such shares, (b) 567,240 shares that are held by various other trusts and entities for which the Reporting Person serves as trustee, investment advisor or manager, as applicable, and, in each such capacity, has sole voting and dispositive power over all such shares, (c) 1,147,738 shares that are held by Satter Medical Technology Partners, L.P. for which the Reporting Person has sole voting and dispositive power over all such shares and (d) 6,951,046 shares that are held by Alerce Medical for which the Reporting Person has sole voting and dispositive power over all such shares. The Reporting Person disclaims beneficial ownership of all shares included under (b), (c) and (d) of this footnote, except to the extent of his pecuniary interest therein.

All shares were purchased by Alerce Medical Technology Partners, L.P. ("Alerce Medical"). The Reporting Person has sole voting and dispositive power over the shares held by Alerce Medical. The Reporting Person disclaims beneficial ownership of the shares except to the extent of his pecuniary interest therein.

This transaction was executed in multiple trades in prices ranging from $3.01 to $3.285, inclusive. The price reported in Column 4 above reflects the weighted average purchase price. The Reporting Person hereby undertakes to provide to the Securities and Exchange Commission staff, the Issuer, or a security holder of the Issuer, upon request, full information regarding the number of shares purchased at each respective price within the range set forth in this footnote.

As of November 19, 2025, includes (a) 240,000 shares that are held by the Muneer A. Satter Revocable Trust for which the Reporting Person serves as trustee and, in such capacity, has sole voting and dispositive power over all such shares, (b) 567,240 shares that are held by various other trusts and entities for which the Reporting Person serves as trustee, investment advisor or manager, as applicable, and, in each such capacity, has sole voting and dispositive power over all such shares, (c) 1,147,738 shares that are held by Satter Medical Technology Partners, L.P. for which the Reporting Person has sole voting and dispositive power over all such shares and (d) 6,951,046 shares that are held by Alerce Medical for which the Reporting Person has sole voting and dispositive power over all such shares. The Reporting Person disclaims beneficial ownership of all shares included under (b), (c) and (d) of this footnote, except to the extent of his pecuniary interest therein.

All shares were purchased by Alerce Medical Technology Partners, L.P. ("Alerce Medical"). The Reporting Person has sole voting and dispositive power over the shares held by Alerce Medical. The Reporting Person disclaims beneficial ownership of the shares except to the extent of his pecuniary interest therein.

This transaction was executed in multiple trades in prices ranging from $2.695 to $3.115, inclusive. The price reported in Column 4 above reflects the weighted average purchase price. The Reporting Person hereby undertakes to provide to the Securities and Exchange Commission staff, the Issuer, or a security holder of the Issuer, upon request, full information regarding the number of shares purchased at each respective price within the range set forth in this footnote.

As of November 19, 2025, includes (a) 240,000 shares that are held by the Muneer A. Satter Revocable Trust for which the Reporting Person serves as trustee and, in such capacity, has sole voting and dispositive power over all such shares, (b) 567,240 shares that are held by various other trusts and entities for which the Reporting Person serves as trustee, investment advisor or manager, as applicable, and, in each such capacity, has sole voting and dispositive power over all such shares, (c) 1,147,738 shares that are held by Satter Medical Technology Partners, L.P. for which the Reporting Person has sole voting and dispositive power over all such shares and (d) 6,951,046 shares that are held by Alerce Medical for which the Reporting Person has sole voting and dispositive power over all such shares. The Reporting Person disclaims beneficial ownership of all shares included under (b), (c) and (d) of this footnote, except to the extent of his pecuniary interest therein.

The transactions reported herein were effected pursuant to the Reporting Person's Rule 10b5-1 trading plan, adopted March 17, 2025.

This transaction was executed in multiple trades in prices ranging from $3.15 o $3.20, inclusive. The price reported in Column 4 above reflects the weighted average purchase price. The Reporting Person hereby undertakes to provide to the Securities and Exchange Commission staff, the Issuer, or a security holder of the Issuer, upon request, full information regarding the number of shares purchased at each respective price within the range set forth in this footnote.

The transactions reported herein were effected pursuant to the Reporting Person's Rule 10b5-1 trading plan, adopted March 17, 2025.

This transaction was executed in multiple trades in prices ranging from $3.035 o $3.08, inclusive. The price reported in Column 4 above reflects the weighted average purchase price. The Reporting Person hereby undertakes to provide to the Securities and Exchange Commission staff, the Issuer, or a security holder of the Issuer, upon request, full information regarding the number of shares purchased at each respective price within the range set forth in this footnote.

The transactions reported herein were effected pursuant to the Reporting Person's Rule 10b5-1 trading plan, adopted March 17, 2025.

This transaction was executed in multiple trades in prices ranging from $2.06 to $2.115, inclusive. The price reported in Column 4 above reflects the weighted average purchase price. The Reporting Person hereby undertakes to provide to the Securities and Exchange Commission staff, the Issuer, or a security holder of the Issuer, upon request, full information regarding the number of shares purchased at each respective price within the range set forth in this footnote.

The transactions reported herein were effected pursuant to the Reporting Person's Rule 10b5-1 trading plan, adopted March 17, 2025.

This transaction was executed in multiple trades in prices ranging from $2.37 to $2.44, inclusive. The price reported in Column 4 above reflects the weighted average purchase price. The Reporting Person hereby undertakes to provide to the Securities and Exchange Commission staff, the Issuer, or a security holder of the Issuer, upon request, full information regarding the number of shares purchased at each respective price within the range set forth in this footnote.

The shares were sold to cover tax withholding obligations in connection with the vesting of restricted stock units ("RSUs").

This transaction was executed in multiple trades in prices ranging from $2.57 to $2.64, inclusive. The price reported in Column 4 above reflects the weighted average sale price. The Reporting Person hereby undertakes to provide to the Securities and Exchange Commission staff, the Issuer, or a security holder of the Issuer, upon request, full information regarding the number of shares sold at each respective price within the range set forth in this footnote.

The shares were sold to cover tax withholding obligations in connection with the vesting of restricted stock units ("RSUs").

This transaction was executed in multiple trades in prices ranging from $2.58 to $2.61, inclusive. The price reported in Column 4 above reflects the weighted average sale price. The Reporting Person hereby undertakes to provide to the Securities and Exchange Commission staff, the Issuer, or a security holder of the Issuer, upon request, full information regarding the number of shares sold at each respective price within the range set forth in this footnote.

The shares were sold to cover tax withholding obligations in connection with the vesting of restricted stock units ("RSUs").

This transaction was executed in multiple trades in prices ranging from $2.57 to $2.64, inclusive. The price reported in Column 4 above reflects the weighted average sale price. The Reporting Person hereby undertakes to provide to the Securities and Exchange Commission staff, the Issuer, or a security holder of the Issuer, upon request, full information regarding the number of shares sold at each respective price within the range set forth in this footnote.

The transactions reported herein were effected pursuant to the Reporting Person's Rule 10b5-1 trading plan, adopted March 17, 2025.

This transaction was executed in multiple trades in prices ranging from $2.45 to $2.47, inclusive. The price reported in Column 4 above reflects the weighted average purchase price. The Reporting Person hereby undertakes to provide to the Securities and Exchange Commission staff, the Issuer, or a security holder of the Issuer, upon request, full information regarding the number of shares purchased at each respective price within the range set forth in this footnote.