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Westlake BioPartners Fund II, L.P.

Disclosed activity across 3 companies

Tapewire entity
24701
SEC CIK
0001811947

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Reported relationships

Latest disclosed role at each company.

CompanyLast reported asReport datePublished
ACELYRIN, Inc.SLRN · Entity 7931010% ownerMay 09, 2023May 11, 2023
Electra Therapeutics, Inc.ETRA · Entity 926510% ownerSeptember 21, 2026September 22, 2026
Latigo Biotherapeutics, Inc.LTGO · Entity 470910% ownerAugust 10, 2026August 11, 2026

Disclosed balances

About these balances

Latest available filing per company, not a reconstructed current portfolio. Matching sequences show the last reported balance with all source rows expandable; grouping alone does not establish account ownership. Do not add unresolved positions together. Filings may omit unchanged positions, and amendments may correct only part of an older disclosure. Jointly reported shares are not necessarily this owner's personal holdings.

ACELYRIN, Inc.

Report date May 09, 2023 · Filed May 11, 2023

Jointly reported with Westlake BioPartners GP II, LLC, Harper Sean E

Security / awardOwnership accountDisclosed shares / unitsDisclosure context
Common StockSEC Table I · non-derivativeDirect9,790,729 Last balance in matching sequence After 2023-05-09 transaction · row 2 Source-order balances reconcile. Account continuity and personal attribution are not independently verified.
2 source rows

Row 1 · 2023-05-09 · Conversion · Acquired 8,540,729 · Balance 8,540,729

F1: Represents shares of Common Stock received upon conversion of shares of the reported series of preferred stock on a one-for-one basis without payment of further consideration.

F2: Shares held directly by Westlake BioPartners Fund II, L.P., or Westlake Fund II. Westlake BioPartners GP II, LLC, or Westlake GP II, is the general partner of Westlake Fund II. Westlake GP II may be deemed to have sole voting and dispositive power with regard to the shares held directly by Westlake Fund II. Beth C. Seidenberg and Sean E. Harper are the Managing Directors of Westlake GP II and share voting and dispositive power over the shares held by Westlake Fund II, each of whom disclaims beneficial ownership of the shares held by Westlake Fund II except to the extent of such person's pecuniary interest therein, if any.

F3: This report on Form 4 is jointly filed by Westlake Fund II, Westlake GP II and Sean E. Harper. Each of the Reporting Persons disclaims beneficial ownership of the securities reported herein for purposes of Rule 16a-1(a) under the Securities Exchange Act of 1934, as amended (the "Exchange Act"), except to the extent of such person's or entity's pecuniary interest therein, if any. Westlake Fund II has designated a representative, Beth C. Seidenberg, a Managing Director of Westlake GP II, to serve on the Issuer's board of directors. This report shall not be deemed an admission that any such entity or person is a beneficial owner of such securities for the purposes of Section 16 of the Exchange Act, or for any other purpose.

Row 2 · 2023-05-09 · Purchase · Acquired 1,250,000 · Balance 9,790,729

F4: Represents shares of Common Stock purchased in the Issuer's initial public offering of Common Stock (the "IPO").

F2: Shares held directly by Westlake BioPartners Fund II, L.P., or Westlake Fund II. Westlake BioPartners GP II, LLC, or Westlake GP II, is the general partner of Westlake Fund II. Westlake GP II may be deemed to have sole voting and dispositive power with regard to the shares held directly by Westlake Fund II. Beth C. Seidenberg and Sean E. Harper are the Managing Directors of Westlake GP II and share voting and dispositive power over the shares held by Westlake Fund II, each of whom disclaims beneficial ownership of the shares held by Westlake Fund II except to the extent of such person's pecuniary interest therein, if any.

F3: This report on Form 4 is jointly filed by Westlake Fund II, Westlake GP II and Sean E. Harper. Each of the Reporting Persons disclaims beneficial ownership of the securities reported herein for purposes of Rule 16a-1(a) under the Securities Exchange Act of 1934, as amended (the "Exchange Act"), except to the extent of such person's or entity's pecuniary interest therein, if any. Westlake Fund II has designated a representative, Beth C. Seidenberg, a Managing Director of Westlake GP II, to serve on the Issuer's board of directors. This report shall not be deemed an admission that any such entity or person is a beneficial owner of such securities for the purposes of Section 16 of the Exchange Act, or for any other purpose.

Series A Redeemable Convertible Preferred StockSEC Table II · derivative / convertible securityDirect0 Reported balance After 2023-05-09 transaction · row 3 Instrument identity requires review; Table II rows are not merged.
1 source row

Row 3 · 2023-05-09 · Conversion · Disposed 4,056,795 · Balance 0

F5: Each share of preferred stock is convertible into one share of Common Stock and has no expiration date. Immediately prior to the completion of the IPO, all shares of preferred stock automatically converted into shares of Common Stock.

F6: Each share of Class A Common Stock was reclassified into one share of Common Stock immediately prior to the completion of the IPO.

F2: Shares held directly by Westlake BioPartners Fund II, L.P., or Westlake Fund II. Westlake BioPartners GP II, LLC, or Westlake GP II, is the general partner of Westlake Fund II. Westlake GP II may be deemed to have sole voting and dispositive power with regard to the shares held directly by Westlake Fund II. Beth C. Seidenberg and Sean E. Harper are the Managing Directors of Westlake GP II and share voting and dispositive power over the shares held by Westlake Fund II, each of whom disclaims beneficial ownership of the shares held by Westlake Fund II except to the extent of such person's pecuniary interest therein, if any.

F3: This report on Form 4 is jointly filed by Westlake Fund II, Westlake GP II and Sean E. Harper. Each of the Reporting Persons disclaims beneficial ownership of the securities reported herein for purposes of Rule 16a-1(a) under the Securities Exchange Act of 1934, as amended (the "Exchange Act"), except to the extent of such person's or entity's pecuniary interest therein, if any. Westlake Fund II has designated a representative, Beth C. Seidenberg, a Managing Director of Westlake GP II, to serve on the Issuer's board of directors. This report shall not be deemed an admission that any such entity or person is a beneficial owner of such securities for the purposes of Section 16 of the Exchange Act, or for any other purpose.

Series B Redeemable Convertible Preferred StockSEC Table II · derivative / convertible securityDirect0 Reported balance After 2023-05-09 transaction · row 4 Instrument identity requires review; Table II rows are not merged.
1 source row

Row 4 · 2023-05-09 · Conversion · Disposed 2,445,786 · Balance 0

F5: Each share of preferred stock is convertible into one share of Common Stock and has no expiration date. Immediately prior to the completion of the IPO, all shares of preferred stock automatically converted into shares of Common Stock.

F6: Each share of Class A Common Stock was reclassified into one share of Common Stock immediately prior to the completion of the IPO.

F2: Shares held directly by Westlake BioPartners Fund II, L.P., or Westlake Fund II. Westlake BioPartners GP II, LLC, or Westlake GP II, is the general partner of Westlake Fund II. Westlake GP II may be deemed to have sole voting and dispositive power with regard to the shares held directly by Westlake Fund II. Beth C. Seidenberg and Sean E. Harper are the Managing Directors of Westlake GP II and share voting and dispositive power over the shares held by Westlake Fund II, each of whom disclaims beneficial ownership of the shares held by Westlake Fund II except to the extent of such person's pecuniary interest therein, if any.

F3: This report on Form 4 is jointly filed by Westlake Fund II, Westlake GP II and Sean E. Harper. Each of the Reporting Persons disclaims beneficial ownership of the securities reported herein for purposes of Rule 16a-1(a) under the Securities Exchange Act of 1934, as amended (the "Exchange Act"), except to the extent of such person's or entity's pecuniary interest therein, if any. Westlake Fund II has designated a representative, Beth C. Seidenberg, a Managing Director of Westlake GP II, to serve on the Issuer's board of directors. This report shall not be deemed an admission that any such entity or person is a beneficial owner of such securities for the purposes of Section 16 of the Exchange Act, or for any other purpose.

Series C Redeemable Convertible Preferred StockSEC Table II · derivative / convertible securityDirect0 Reported balance After 2023-05-09 transaction · row 5 Instrument identity requires review; Table II rows are not merged.
1 source row

Row 5 · 2023-05-09 · Conversion · Disposed 2,038,148 · Balance 0

F5: Each share of preferred stock is convertible into one share of Common Stock and has no expiration date. Immediately prior to the completion of the IPO, all shares of preferred stock automatically converted into shares of Common Stock.

F6: Each share of Class A Common Stock was reclassified into one share of Common Stock immediately prior to the completion of the IPO.

F2: Shares held directly by Westlake BioPartners Fund II, L.P., or Westlake Fund II. Westlake BioPartners GP II, LLC, or Westlake GP II, is the general partner of Westlake Fund II. Westlake GP II may be deemed to have sole voting and dispositive power with regard to the shares held directly by Westlake Fund II. Beth C. Seidenberg and Sean E. Harper are the Managing Directors of Westlake GP II and share voting and dispositive power over the shares held by Westlake Fund II, each of whom disclaims beneficial ownership of the shares held by Westlake Fund II except to the extent of such person's pecuniary interest therein, if any.

F3: This report on Form 4 is jointly filed by Westlake Fund II, Westlake GP II and Sean E. Harper. Each of the Reporting Persons disclaims beneficial ownership of the securities reported herein for purposes of Rule 16a-1(a) under the Securities Exchange Act of 1934, as amended (the "Exchange Act"), except to the extent of such person's or entity's pecuniary interest therein, if any. Westlake Fund II has designated a representative, Beth C. Seidenberg, a Managing Director of Westlake GP II, to serve on the Issuer's board of directors. This report shall not be deemed an admission that any such entity or person is a beneficial owner of such securities for the purposes of Section 16 of the Exchange Act, or for any other purpose.

Filing footnotes · ownership attribution and instrument terms

F1: Represents shares of Common Stock received upon conversion of shares of the reported series of preferred stock on a one-for-one basis without payment of further consideration.

F2: Shares held directly by Westlake BioPartners Fund II, L.P., or Westlake Fund II. Westlake BioPartners GP II, LLC, or Westlake GP II, is the general partner of Westlake Fund II. Westlake GP II may be deemed to have sole voting and dispositive power with regard to the shares held directly by Westlake Fund II. Beth C. Seidenberg and Sean E. Harper are the Managing Directors of Westlake GP II and share voting and dispositive power over the shares held by Westlake Fund II, each of whom disclaims beneficial ownership of the shares held by Westlake Fund II except to the extent of such person's pecuniary interest therein, if any.

F3: This report on Form 4 is jointly filed by Westlake Fund II, Westlake GP II and Sean E. Harper. Each of the Reporting Persons disclaims beneficial ownership of the securities reported herein for purposes of Rule 16a-1(a) under the Securities Exchange Act of 1934, as amended (the "Exchange Act"), except to the extent of such person's or entity's pecuniary interest therein, if any. Westlake Fund II has designated a representative, Beth C. Seidenberg, a Managing Director of Westlake GP II, to serve on the Issuer's board of directors. This report shall not be deemed an admission that any such entity or person is a beneficial owner of such securities for the purposes of Section 16 of the Exchange Act, or for any other purpose.

F4: Represents shares of Common Stock purchased in the Issuer's initial public offering of Common Stock (the "IPO").

F5: Each share of preferred stock is convertible into one share of Common Stock and has no expiration date. Immediately prior to the completion of the IPO, all shares of preferred stock automatically converted into shares of Common Stock.

F6: Each share of Class A Common Stock was reclassified into one share of Common Stock immediately prior to the completion of the IPO.

Electra Therapeutics, Inc.

Report date September 21, 2026 · Filed September 22, 2026

Jointly reported with Westlake BioPartners Fund I, L.P., Westlake BioPartners GP I, LLC, Westlake BioPartners GP II, LLC

Security / awardOwnership accountDisclosed shares / unitsDisclosure context
Common StockSEC Table I · non-derivativeIndirectSee footnote3,527,136 Reported balance Holding disclosure · report date 2026-09-21 · row 1 Holding and transaction disclosures are not merged.
1 source row

Row 1 · Balance 3,527,136

F3: Shares acquired upon the automatic conversion of redeemable preferred stock on a 1:1 basis upon the closing of the Issuer's initial public offering without the payment of further consideration. Each Reporting Person had previously waived its right to voluntarily convert such redeemable preferred stock.

F1: Shares held directly by Westlake BioPartners Fund I, L.P. (Fund I). The general partner of Fund I is Westlake BioPartners GP I, LLC (GP I). GP I may be deemed to share voting and dispositive power with regard to the shares held directly by Fund I. Beth Seidenberg (Seidenberg) is the sole managing director of GP I and has voting and dispositive power over the shares held by Fund I. Seidenberg disclaims Section 16 beneficial ownership of the shares reported herein except to the extent of her pecuniary interest therein, if any, and the inclusion of these shares in this report shall not be deemed an admission of beneficial ownership of any of the reported shares for purposes of Section 16 or any other purpose.

Common StockSEC Table I · non-derivativeIndirectSee footnote2,820,403 Reported balance Holding disclosure · report date 2026-09-21 · row 2 Holding and transaction disclosures are not merged.
1 source row

Row 2 · Balance 2,820,403

F3: Shares acquired upon the automatic conversion of redeemable preferred stock on a 1:1 basis upon the closing of the Issuer's initial public offering without the payment of further consideration. Each Reporting Person had previously waived its right to voluntarily convert such redeemable preferred stock.

F2: Shares held directly by Westlake BioPartners Fund II, L.P. (Fund II). The general partner of Fund II is Westlake BioPartners GP II, LLC (GP II). GP II may be deemed to share voting and dispositive power with regard to the shares held directly by Fund II. Seidenberg is the sole managing director of GP II and has voting and dispositive power over the shares held by Fund II. Seidenberg disclaims Section 16 beneficial ownership of the shares reported herein except to the extent of her pecuniary interest therein, if any, and the inclusion of these shares in this report shall not be deemed an admission of beneficial ownership of any of the reported shares for purposes of Section 16 or any other purpose.

Filing footnotes · ownership attribution and instrument terms

F1: Shares held directly by Westlake BioPartners Fund I, L.P. (Fund I). The general partner of Fund I is Westlake BioPartners GP I, LLC (GP I). GP I may be deemed to share voting and dispositive power with regard to the shares held directly by Fund I. Beth Seidenberg (Seidenberg) is the sole managing director of GP I and has voting and dispositive power over the shares held by Fund I. Seidenberg disclaims Section 16 beneficial ownership of the shares reported herein except to the extent of her pecuniary interest therein, if any, and the inclusion of these shares in this report shall not be deemed an admission of beneficial ownership of any of the reported shares for purposes of Section 16 or any other purpose.

F2: Shares held directly by Westlake BioPartners Fund II, L.P. (Fund II). The general partner of Fund II is Westlake BioPartners GP II, LLC (GP II). GP II may be deemed to share voting and dispositive power with regard to the shares held directly by Fund II. Seidenberg is the sole managing director of GP II and has voting and dispositive power over the shares held by Fund II. Seidenberg disclaims Section 16 beneficial ownership of the shares reported herein except to the extent of her pecuniary interest therein, if any, and the inclusion of these shares in this report shall not be deemed an admission of beneficial ownership of any of the reported shares for purposes of Section 16 or any other purpose.

F3: Shares acquired upon the automatic conversion of redeemable preferred stock on a 1:1 basis upon the closing of the Issuer's initial public offering without the payment of further consideration. Each Reporting Person had previously waived its right to voluntarily convert such redeemable preferred stock.

Security / awardOwnership accountDisclosed shares / unitsDisclosure context
Common StockSEC Table I · non-derivativeIndirectSee footnote1,368,532 Reported balance After 2026-08-10 transaction · row 1 Joint disclosure: continuity of the reported position is unresolved; see ownership footnotes.
1 source row

Row 1 · 2026-08-10 · Conversion · Acquired 938,979 · Balance 1,368,532

F1: Each share of Series Seed Convertible Preferred Stock, Series A Convertible Preferred Stock, Series A-2 Convertible Preferred Stock and Series B Convertible Preferred Stock (collectively, the "Preferred Stock") converted automatically into 1 share of Common Stock upon the closing of the Issuer's initial public offering without payment of further consideration. Share numbers give effect to such conversion. The Preferred Stock had no expiration date.

F2: Shares held directly by Westlake BioPartners Fund I, L.P. ("Fund I"). The general partner of Fund I is Westlake BioPartners GP I, LLC ("GP I"). GP I may be deemed to share voting and dispositive power with regard to the shares held directly by Fund I. Beth Seidenberg ("Seidenberg") is the sole managing director of GP I and has voting and dispositive power over the shares held by Fund I. Seidenberg disclaims Section 16 beneficial ownership of the shares reported herein except to the extent of her pecuniary interest therein, if any, and the inclusion of these shares in this report shall not be deemed an admission of beneficial ownership of any of the reported shares for purposes of Section 16 or any other purpose.

Common StockSEC Table I · non-derivativeIndirectSee footnote4,916,374 Reported balance After 2026-08-10 transaction · row 2 Joint disclosure: continuity of the reported position is unresolved; see ownership footnotes.
1 source row

Row 2 · 2026-08-10 · Conversion · Acquired 3,547,842 · Balance 4,916,374

F1: Each share of Series Seed Convertible Preferred Stock, Series A Convertible Preferred Stock, Series A-2 Convertible Preferred Stock and Series B Convertible Preferred Stock (collectively, the "Preferred Stock") converted automatically into 1 share of Common Stock upon the closing of the Issuer's initial public offering without payment of further consideration. Share numbers give effect to such conversion. The Preferred Stock had no expiration date.

F2: Shares held directly by Westlake BioPartners Fund I, L.P. ("Fund I"). The general partner of Fund I is Westlake BioPartners GP I, LLC ("GP I"). GP I may be deemed to share voting and dispositive power with regard to the shares held directly by Fund I. Beth Seidenberg ("Seidenberg") is the sole managing director of GP I and has voting and dispositive power over the shares held by Fund I. Seidenberg disclaims Section 16 beneficial ownership of the shares reported herein except to the extent of her pecuniary interest therein, if any, and the inclusion of these shares in this report shall not be deemed an admission of beneficial ownership of any of the reported shares for purposes of Section 16 or any other purpose.

Common StockSEC Table I · non-derivativeIndirectSee footnote5,944,009 Reported balance After 2026-08-10 transaction · row 3 Joint disclosure: continuity of the reported position is unresolved; see ownership footnotes.
1 source row

Row 3 · 2026-08-10 · Conversion · Acquired 1,027,635 · Balance 5,944,009

F1: Each share of Series Seed Convertible Preferred Stock, Series A Convertible Preferred Stock, Series A-2 Convertible Preferred Stock and Series B Convertible Preferred Stock (collectively, the "Preferred Stock") converted automatically into 1 share of Common Stock upon the closing of the Issuer's initial public offering without payment of further consideration. Share numbers give effect to such conversion. The Preferred Stock had no expiration date.

F2: Shares held directly by Westlake BioPartners Fund I, L.P. ("Fund I"). The general partner of Fund I is Westlake BioPartners GP I, LLC ("GP I"). GP I may be deemed to share voting and dispositive power with regard to the shares held directly by Fund I. Beth Seidenberg ("Seidenberg") is the sole managing director of GP I and has voting and dispositive power over the shares held by Fund I. Seidenberg disclaims Section 16 beneficial ownership of the shares reported herein except to the extent of her pecuniary interest therein, if any, and the inclusion of these shares in this report shall not be deemed an admission of beneficial ownership of any of the reported shares for purposes of Section 16 or any other purpose.

Common StockSEC Table I · non-derivativeIndirectSee footnote3,510,927 Reported balance After 2026-08-10 transaction · row 4 Joint disclosure: continuity of the reported position is unresolved; see ownership footnotes.
1 source row

Row 4 · 2026-08-10 · Conversion · Acquired 3,464,072 · Balance 3,510,927

F1: Each share of Series Seed Convertible Preferred Stock, Series A Convertible Preferred Stock, Series A-2 Convertible Preferred Stock and Series B Convertible Preferred Stock (collectively, the "Preferred Stock") converted automatically into 1 share of Common Stock upon the closing of the Issuer's initial public offering without payment of further consideration. Share numbers give effect to such conversion. The Preferred Stock had no expiration date.

F3: Shares held directly by Westlake BioPartners Fund II, L.P. ("Fund II"). The general partner of Fund II is Westlake BioPartners GP II, LLC ("GP II"). GP II may be deemed to share voting and dispositive power with regard to the shares held directly by Fund II. Seidenberg is the sole managing director of GP II and has voting and dispositive power over the shares held by Fund II. Seidenberg disclaims Section 16 beneficial ownership of the shares reported herein except to the extent of her pecuniary interest therein, if any, and the inclusion of these shares in this report shall not be deemed an admission of beneficial ownership of any of the reported shares for purposes of Section 16 or any other purpose.

Common StockSEC Table I · non-derivativeIndirectSee footnote4,995,328 Reported balance After 2026-08-10 transaction · row 5 Joint disclosure: continuity of the reported position is unresolved; see ownership footnotes.
1 source row

Row 5 · 2026-08-10 · Conversion · Acquired 1,484,401 · Balance 4,995,328

F1: Each share of Series Seed Convertible Preferred Stock, Series A Convertible Preferred Stock, Series A-2 Convertible Preferred Stock and Series B Convertible Preferred Stock (collectively, the "Preferred Stock") converted automatically into 1 share of Common Stock upon the closing of the Issuer's initial public offering without payment of further consideration. Share numbers give effect to such conversion. The Preferred Stock had no expiration date.

F3: Shares held directly by Westlake BioPartners Fund II, L.P. ("Fund II"). The general partner of Fund II is Westlake BioPartners GP II, LLC ("GP II"). GP II may be deemed to share voting and dispositive power with regard to the shares held directly by Fund II. Seidenberg is the sole managing director of GP II and has voting and dispositive power over the shares held by Fund II. Seidenberg disclaims Section 16 beneficial ownership of the shares reported herein except to the extent of her pecuniary interest therein, if any, and the inclusion of these shares in this report shall not be deemed an admission of beneficial ownership of any of the reported shares for purposes of Section 16 or any other purpose.

Common StockSEC Table I · non-derivativeIndirectSee footnote5,160,847 Reported balance After 2026-08-10 transaction · row 6 Joint disclosure: continuity of the reported position is unresolved; see ownership footnotes.
1 source row

Row 6 · 2026-08-10 · Conversion · Acquired 165,519 · Balance 5,160,847

F4: Reflects a convertible note that was convertible into shares of Common Stock of the Issuer. The convertible note had a maturity date of June 17, 2027. The principal amount of the convertible note together with any accrued but unpaid interest automatically converted into shares of Common Stock of the Issuer upon the closing of the Issuer's initial public offering at a conversion price equal to the initial public offering price of the Issuer's common stock.

F3: Shares held directly by Westlake BioPartners Fund II, L.P. ("Fund II"). The general partner of Fund II is Westlake BioPartners GP II, LLC ("GP II"). GP II may be deemed to share voting and dispositive power with regard to the shares held directly by Fund II. Seidenberg is the sole managing director of GP II and has voting and dispositive power over the shares held by Fund II. Seidenberg disclaims Section 16 beneficial ownership of the shares reported herein except to the extent of her pecuniary interest therein, if any, and the inclusion of these shares in this report shall not be deemed an admission of beneficial ownership of any of the reported shares for purposes of Section 16 or any other purpose.

Common StockSEC Table I · non-derivativeIndirectSee footnote2,094,813 Reported balance After 2026-08-10 transaction · row 7 Joint disclosure: continuity of the reported position is unresolved; see ownership footnotes.
1 source row

Row 7 · 2026-08-10 · Conversion · Acquired 2,066,857 · Balance 2,094,813

F1: Each share of Series Seed Convertible Preferred Stock, Series A Convertible Preferred Stock, Series A-2 Convertible Preferred Stock and Series B Convertible Preferred Stock (collectively, the "Preferred Stock") converted automatically into 1 share of Common Stock upon the closing of the Issuer's initial public offering without payment of further consideration. Share numbers give effect to such conversion. The Preferred Stock had no expiration date.

F5: Shares held directly by Westlake BioPartners Opportunity Fund I, L.P. ("Opportunity Fund"). The general partner of Opportunity Fund is Westlake BioPartners Opportunity GP I, LLC ("Opportunity GP"). Opportunity GP may be deemed to share voting and dispositive power with regard to the shares held directly by Opportunity Fund. Seidenberg is the sole managing director of Opportunity GP and has voting and dispositive power over the shares held by Opportunity Fund. Seidenberg disclaims Section 16 beneficial ownership of the shares reported herein except to the extent of her pecuniary interest therein, if any, and the inclusion of these shares in this report shall not be deemed an admission of beneficial ownership of any of the reported shares for purposes of Section 16 or any other purpose.

Series Seed Convertible Preferred StockSEC Table II · derivative / convertible securityIndirectSee footnote0 Reported balance After 2026-08-10 transaction · row 8 Instrument identity requires review; Table II rows are not merged.
1 source row

Row 8 · 2026-08-10 · Conversion · Disposed 938,979 · Balance 0

F1: Each share of Series Seed Convertible Preferred Stock, Series A Convertible Preferred Stock, Series A-2 Convertible Preferred Stock and Series B Convertible Preferred Stock (collectively, the "Preferred Stock") converted automatically into 1 share of Common Stock upon the closing of the Issuer's initial public offering without payment of further consideration. Share numbers give effect to such conversion. The Preferred Stock had no expiration date.

F2: Shares held directly by Westlake BioPartners Fund I, L.P. ("Fund I"). The general partner of Fund I is Westlake BioPartners GP I, LLC ("GP I"). GP I may be deemed to share voting and dispositive power with regard to the shares held directly by Fund I. Beth Seidenberg ("Seidenberg") is the sole managing director of GP I and has voting and dispositive power over the shares held by Fund I. Seidenberg disclaims Section 16 beneficial ownership of the shares reported herein except to the extent of her pecuniary interest therein, if any, and the inclusion of these shares in this report shall not be deemed an admission of beneficial ownership of any of the reported shares for purposes of Section 16 or any other purpose.

Series A Convertible Preferred StockSEC Table II · derivative / convertible securityIndirectSee footnote0 Reported balance After 2026-08-10 transaction · row 9 Instrument identity requires review; Table II rows are not merged.
1 source row

Row 9 · 2026-08-10 · Conversion · Disposed 3,547,842 · Balance 0

F1: Each share of Series Seed Convertible Preferred Stock, Series A Convertible Preferred Stock, Series A-2 Convertible Preferred Stock and Series B Convertible Preferred Stock (collectively, the "Preferred Stock") converted automatically into 1 share of Common Stock upon the closing of the Issuer's initial public offering without payment of further consideration. Share numbers give effect to such conversion. The Preferred Stock had no expiration date.

F2: Shares held directly by Westlake BioPartners Fund I, L.P. ("Fund I"). The general partner of Fund I is Westlake BioPartners GP I, LLC ("GP I"). GP I may be deemed to share voting and dispositive power with regard to the shares held directly by Fund I. Beth Seidenberg ("Seidenberg") is the sole managing director of GP I and has voting and dispositive power over the shares held by Fund I. Seidenberg disclaims Section 16 beneficial ownership of the shares reported herein except to the extent of her pecuniary interest therein, if any, and the inclusion of these shares in this report shall not be deemed an admission of beneficial ownership of any of the reported shares for purposes of Section 16 or any other purpose.

Series A-2 Convertible Preferred StockSEC Table II · derivative / convertible securityIndirectSee footnote0 Reported balance After 2026-08-10 transaction · row 10 Instrument identity requires review; Table II rows are not merged.
1 source row

Row 10 · 2026-08-10 · Conversion · Disposed 1,027,635 · Balance 0

F1: Each share of Series Seed Convertible Preferred Stock, Series A Convertible Preferred Stock, Series A-2 Convertible Preferred Stock and Series B Convertible Preferred Stock (collectively, the "Preferred Stock") converted automatically into 1 share of Common Stock upon the closing of the Issuer's initial public offering without payment of further consideration. Share numbers give effect to such conversion. The Preferred Stock had no expiration date.

F2: Shares held directly by Westlake BioPartners Fund I, L.P. ("Fund I"). The general partner of Fund I is Westlake BioPartners GP I, LLC ("GP I"). GP I may be deemed to share voting and dispositive power with regard to the shares held directly by Fund I. Beth Seidenberg ("Seidenberg") is the sole managing director of GP I and has voting and dispositive power over the shares held by Fund I. Seidenberg disclaims Section 16 beneficial ownership of the shares reported herein except to the extent of her pecuniary interest therein, if any, and the inclusion of these shares in this report shall not be deemed an admission of beneficial ownership of any of the reported shares for purposes of Section 16 or any other purpose.

Series A-2 Convertible Preferred StockSEC Table II · derivative / convertible securityIndirectSee footnote0 Reported balance After 2026-08-10 transaction · row 11 Instrument identity requires review; Table II rows are not merged.
1 source row

Row 11 · 2026-08-10 · Conversion · Disposed 3,464,072 · Balance 0

F1: Each share of Series Seed Convertible Preferred Stock, Series A Convertible Preferred Stock, Series A-2 Convertible Preferred Stock and Series B Convertible Preferred Stock (collectively, the "Preferred Stock") converted automatically into 1 share of Common Stock upon the closing of the Issuer's initial public offering without payment of further consideration. Share numbers give effect to such conversion. The Preferred Stock had no expiration date.

F3: Shares held directly by Westlake BioPartners Fund II, L.P. ("Fund II"). The general partner of Fund II is Westlake BioPartners GP II, LLC ("GP II"). GP II may be deemed to share voting and dispositive power with regard to the shares held directly by Fund II. Seidenberg is the sole managing director of GP II and has voting and dispositive power over the shares held by Fund II. Seidenberg disclaims Section 16 beneficial ownership of the shares reported herein except to the extent of her pecuniary interest therein, if any, and the inclusion of these shares in this report shall not be deemed an admission of beneficial ownership of any of the reported shares for purposes of Section 16 or any other purpose.

Series A-2 Convertible Preferred StockSEC Table II · derivative / convertible securityIndirectSee footnote0 Reported balance After 2026-08-10 transaction · row 13 Instrument identity requires review; Table II rows are not merged.
1 source row

Row 13 · 2026-08-10 · Conversion · Disposed 2,066,857 · Balance 0

F1: Each share of Series Seed Convertible Preferred Stock, Series A Convertible Preferred Stock, Series A-2 Convertible Preferred Stock and Series B Convertible Preferred Stock (collectively, the "Preferred Stock") converted automatically into 1 share of Common Stock upon the closing of the Issuer's initial public offering without payment of further consideration. Share numbers give effect to such conversion. The Preferred Stock had no expiration date.

F5: Shares held directly by Westlake BioPartners Opportunity Fund I, L.P. ("Opportunity Fund"). The general partner of Opportunity Fund is Westlake BioPartners Opportunity GP I, LLC ("Opportunity GP"). Opportunity GP may be deemed to share voting and dispositive power with regard to the shares held directly by Opportunity Fund. Seidenberg is the sole managing director of Opportunity GP and has voting and dispositive power over the shares held by Opportunity Fund. Seidenberg disclaims Section 16 beneficial ownership of the shares reported herein except to the extent of her pecuniary interest therein, if any, and the inclusion of these shares in this report shall not be deemed an admission of beneficial ownership of any of the reported shares for purposes of Section 16 or any other purpose.

Series B Convertible Preferred StockSEC Table II · derivative / convertible securityIndirectSee footnote0 Reported balance After 2026-08-10 transaction · row 12 Instrument identity requires review; Table II rows are not merged.
1 source row

Row 12 · 2026-08-10 · Conversion · Disposed 1,484,401 · Balance 0

F1: Each share of Series Seed Convertible Preferred Stock, Series A Convertible Preferred Stock, Series A-2 Convertible Preferred Stock and Series B Convertible Preferred Stock (collectively, the "Preferred Stock") converted automatically into 1 share of Common Stock upon the closing of the Issuer's initial public offering without payment of further consideration. Share numbers give effect to such conversion. The Preferred Stock had no expiration date.

F3: Shares held directly by Westlake BioPartners Fund II, L.P. ("Fund II"). The general partner of Fund II is Westlake BioPartners GP II, LLC ("GP II"). GP II may be deemed to share voting and dispositive power with regard to the shares held directly by Fund II. Seidenberg is the sole managing director of GP II and has voting and dispositive power over the shares held by Fund II. Seidenberg disclaims Section 16 beneficial ownership of the shares reported herein except to the extent of her pecuniary interest therein, if any, and the inclusion of these shares in this report shall not be deemed an admission of beneficial ownership of any of the reported shares for purposes of Section 16 or any other purpose.

Convertible Promissory NoteSEC Table II · derivative / convertible securityIndirectSee footnote0 Reported balance After 2026-08-10 transaction · row 14 Instrument identity requires review; Table II rows are not merged.
1 source row

Row 14 · 2026-08-10 · Conversion · Disposed 165,519 · Balance 0

F4: Reflects a convertible note that was convertible into shares of Common Stock of the Issuer. The convertible note had a maturity date of June 17, 2027. The principal amount of the convertible note together with any accrued but unpaid interest automatically converted into shares of Common Stock of the Issuer upon the closing of the Issuer's initial public offering at a conversion price equal to the initial public offering price of the Issuer's common stock.

F3: Shares held directly by Westlake BioPartners Fund II, L.P. ("Fund II"). The general partner of Fund II is Westlake BioPartners GP II, LLC ("GP II"). GP II may be deemed to share voting and dispositive power with regard to the shares held directly by Fund II. Seidenberg is the sole managing director of GP II and has voting and dispositive power over the shares held by Fund II. Seidenberg disclaims Section 16 beneficial ownership of the shares reported herein except to the extent of her pecuniary interest therein, if any, and the inclusion of these shares in this report shall not be deemed an admission of beneficial ownership of any of the reported shares for purposes of Section 16 or any other purpose.

Filing footnotes · ownership attribution and instrument terms

F1: Each share of Series Seed Convertible Preferred Stock, Series A Convertible Preferred Stock, Series A-2 Convertible Preferred Stock and Series B Convertible Preferred Stock (collectively, the "Preferred Stock") converted automatically into 1 share of Common Stock upon the closing of the Issuer's initial public offering without payment of further consideration. Share numbers give effect to such conversion. The Preferred Stock had no expiration date.

F2: Shares held directly by Westlake BioPartners Fund I, L.P. ("Fund I"). The general partner of Fund I is Westlake BioPartners GP I, LLC ("GP I"). GP I may be deemed to share voting and dispositive power with regard to the shares held directly by Fund I. Beth Seidenberg ("Seidenberg") is the sole managing director of GP I and has voting and dispositive power over the shares held by Fund I. Seidenberg disclaims Section 16 beneficial ownership of the shares reported herein except to the extent of her pecuniary interest therein, if any, and the inclusion of these shares in this report shall not be deemed an admission of beneficial ownership of any of the reported shares for purposes of Section 16 or any other purpose.

F3: Shares held directly by Westlake BioPartners Fund II, L.P. ("Fund II"). The general partner of Fund II is Westlake BioPartners GP II, LLC ("GP II"). GP II may be deemed to share voting and dispositive power with regard to the shares held directly by Fund II. Seidenberg is the sole managing director of GP II and has voting and dispositive power over the shares held by Fund II. Seidenberg disclaims Section 16 beneficial ownership of the shares reported herein except to the extent of her pecuniary interest therein, if any, and the inclusion of these shares in this report shall not be deemed an admission of beneficial ownership of any of the reported shares for purposes of Section 16 or any other purpose.

F4: Reflects a convertible note that was convertible into shares of Common Stock of the Issuer. The convertible note had a maturity date of June 17, 2027. The principal amount of the convertible note together with any accrued but unpaid interest automatically converted into shares of Common Stock of the Issuer upon the closing of the Issuer's initial public offering at a conversion price equal to the initial public offering price of the Issuer's common stock.

F5: Shares held directly by Westlake BioPartners Opportunity Fund I, L.P. ("Opportunity Fund"). The general partner of Opportunity Fund is Westlake BioPartners Opportunity GP I, LLC ("Opportunity GP"). Opportunity GP may be deemed to share voting and dispositive power with regard to the shares held directly by Opportunity Fund. Seidenberg is the sole managing director of Opportunity GP and has voting and dispositive power over the shares held by Opportunity Fund. Seidenberg disclaims Section 16 beneficial ownership of the shares reported herein except to the extent of her pecuniary interest therein, if any, and the inclusion of these shares in this report shall not be deemed an admission of beneficial ownership of any of the reported shares for purposes of Section 16 or any other purpose.

Transaction history

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Purchases/sales include open-market and private transactions. Plan disclosure applies to the filing; individual rows may differ. “Not disclosed” is not “unplanned.”

The cutoff filters transaction history only. Company summaries and owner relationships show the latest available disclosures. Parser corrections can improve historical records.

Transaction dateCompanyActivity / securityShares / unitsReported priceReported valueDetails
August 10, 2026 Filed Aug 11, 2026 10:00 UTC Latigo Biotherapeutics, Inc. LTGO · Entity 4709 ConversionConvertible Promissory Note · Derivative 165,519 Not disclosed Not disclosed
Disclosure

SEC source: 0001104659-26-093633 · tm2622668-1_4seq1.xml · derivative · entry 14

Westlake BioPartners Fund I, L.P. · CIK 0001749591 · 10% owner

Westlake BioPartners GP I, LLC · CIK 0002007650 · 10% owner

Westlake BioPartners Fund II, L.P. · CIK 0001811947 · 10% owner

Westlake BioPartners GP II, LLC · CIK 0001811948 · 10% owner

Westlake BioPartners Opportunity Fund I, L.P. · CIK 0001811946 · 10% owner

Westlake BioPartners Opportunity GP I, LLC · CIK 0001811945 · 10% owner

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: No plan indicated

Ownership: Indirect · See footnote

Disclosed balance after: 0

Underlying: Common Stock · 165,519 shares

Expires not disclosed

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F4 · derivative.exercise_price: Reflects a convertible note that was convertible into shares of Common Stock of the Issuer. The convertible note had a maturity date of June 17, 2027. The principal amount of the convertible note together with any accrued but unpaid interest automatically converted into shares of Common Stock of the Issuer upon the closing of the Issuer's initial public offering at a conversion price equal to the initial public offering price of the Issuer's common stock.

F4 · price: Reflects a convertible note that was convertible into shares of Common Stock of the Issuer. The convertible note had a maturity date of June 17, 2027. The principal amount of the convertible note together with any accrued but unpaid interest automatically converted into shares of Common Stock of the Issuer upon the closing of the Issuer's initial public offering at a conversion price equal to the initial public offering price of the Issuer's common stock.

F4 · derivative.exercise_date: Reflects a convertible note that was convertible into shares of Common Stock of the Issuer. The convertible note had a maturity date of June 17, 2027. The principal amount of the convertible note together with any accrued but unpaid interest automatically converted into shares of Common Stock of the Issuer upon the closing of the Issuer's initial public offering at a conversion price equal to the initial public offering price of the Issuer's common stock.

F4 · derivative.expiration_date: Reflects a convertible note that was convertible into shares of Common Stock of the Issuer. The convertible note had a maturity date of June 17, 2027. The principal amount of the convertible note together with any accrued but unpaid interest automatically converted into shares of Common Stock of the Issuer upon the closing of the Issuer's initial public offering at a conversion price equal to the initial public offering price of the Issuer's common stock.

F3 · ownership.nature: Shares held directly by Westlake BioPartners Fund II, L.P. ("Fund II"). The general partner of Fund II is Westlake BioPartners GP II, LLC ("GP II"). GP II may be deemed to share voting and dispositive power with regard to the shares held directly by Fund II. Seidenberg is the sole managing director of GP II and has voting and dispositive power over the shares held by Fund II. Seidenberg disclaims Section 16 beneficial ownership of the shares reported herein except to the extent of her pecuniary interest therein, if any, and the inclusion of these shares in this report shall not be deemed an admission of beneficial ownership of any of the reported shares for purposes of Section 16 or any other purpose.

Read SEC document
August 10, 2026 Filed Aug 11, 2026 10:00 UTC Latigo Biotherapeutics, Inc. LTGO · Entity 4709 ConversionSeries A-2 Convertible Preferred Stock · Derivative 2,066,857 Not disclosed Not disclosed
Disclosure

SEC source: 0001104659-26-093633 · tm2622668-1_4seq1.xml · derivative · entry 13

Westlake BioPartners Fund I, L.P. · CIK 0001749591 · 10% owner

Westlake BioPartners GP I, LLC · CIK 0002007650 · 10% owner

Westlake BioPartners Fund II, L.P. · CIK 0001811947 · 10% owner

Westlake BioPartners GP II, LLC · CIK 0001811948 · 10% owner

Westlake BioPartners Opportunity Fund I, L.P. · CIK 0001811946 · 10% owner

Westlake BioPartners Opportunity GP I, LLC · CIK 0001811945 · 10% owner

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: No plan indicated

Ownership: Indirect · See footnote

Disclosed balance after: 0

Underlying: Common Stock · 2,066,857 shares

Expires not disclosed

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F1 · derivative.exercise_price: Each share of Series Seed Convertible Preferred Stock, Series A Convertible Preferred Stock, Series A-2 Convertible Preferred Stock and Series B Convertible Preferred Stock (collectively, the "Preferred Stock") converted automatically into 1 share of Common Stock upon the closing of the Issuer's initial public offering without payment of further consideration. Share numbers give effect to such conversion. The Preferred Stock had no expiration date.

F1 · price: Each share of Series Seed Convertible Preferred Stock, Series A Convertible Preferred Stock, Series A-2 Convertible Preferred Stock and Series B Convertible Preferred Stock (collectively, the "Preferred Stock") converted automatically into 1 share of Common Stock upon the closing of the Issuer's initial public offering without payment of further consideration. Share numbers give effect to such conversion. The Preferred Stock had no expiration date.

F1 · derivative.exercise_date: Each share of Series Seed Convertible Preferred Stock, Series A Convertible Preferred Stock, Series A-2 Convertible Preferred Stock and Series B Convertible Preferred Stock (collectively, the "Preferred Stock") converted automatically into 1 share of Common Stock upon the closing of the Issuer's initial public offering without payment of further consideration. Share numbers give effect to such conversion. The Preferred Stock had no expiration date.

F1 · derivative.expiration_date: Each share of Series Seed Convertible Preferred Stock, Series A Convertible Preferred Stock, Series A-2 Convertible Preferred Stock and Series B Convertible Preferred Stock (collectively, the "Preferred Stock") converted automatically into 1 share of Common Stock upon the closing of the Issuer's initial public offering without payment of further consideration. Share numbers give effect to such conversion. The Preferred Stock had no expiration date.

F5 · ownership.nature: Shares held directly by Westlake BioPartners Opportunity Fund I, L.P. ("Opportunity Fund"). The general partner of Opportunity Fund is Westlake BioPartners Opportunity GP I, LLC ("Opportunity GP"). Opportunity GP may be deemed to share voting and dispositive power with regard to the shares held directly by Opportunity Fund. Seidenberg is the sole managing director of Opportunity GP and has voting and dispositive power over the shares held by Opportunity Fund. Seidenberg disclaims Section 16 beneficial ownership of the shares reported herein except to the extent of her pecuniary interest therein, if any, and the inclusion of these shares in this report shall not be deemed an admission of beneficial ownership of any of the reported shares for purposes of Section 16 or any other purpose.

Read SEC document
August 10, 2026 Filed Aug 11, 2026 10:00 UTC Latigo Biotherapeutics, Inc. LTGO · Entity 4709 ConversionSeries B Convertible Preferred Stock · Derivative 1,484,401 Not disclosed Not disclosed
Disclosure

SEC source: 0001104659-26-093633 · tm2622668-1_4seq1.xml · derivative · entry 12

Westlake BioPartners Fund I, L.P. · CIK 0001749591 · 10% owner

Westlake BioPartners GP I, LLC · CIK 0002007650 · 10% owner

Westlake BioPartners Fund II, L.P. · CIK 0001811947 · 10% owner

Westlake BioPartners GP II, LLC · CIK 0001811948 · 10% owner

Westlake BioPartners Opportunity Fund I, L.P. · CIK 0001811946 · 10% owner

Westlake BioPartners Opportunity GP I, LLC · CIK 0001811945 · 10% owner

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: No plan indicated

Ownership: Indirect · See footnote

Disclosed balance after: 0

Underlying: Common Stock · 1,484,401 shares

Expires not disclosed

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F1 · derivative.exercise_price: Each share of Series Seed Convertible Preferred Stock, Series A Convertible Preferred Stock, Series A-2 Convertible Preferred Stock and Series B Convertible Preferred Stock (collectively, the "Preferred Stock") converted automatically into 1 share of Common Stock upon the closing of the Issuer's initial public offering without payment of further consideration. Share numbers give effect to such conversion. The Preferred Stock had no expiration date.

F1 · price: Each share of Series Seed Convertible Preferred Stock, Series A Convertible Preferred Stock, Series A-2 Convertible Preferred Stock and Series B Convertible Preferred Stock (collectively, the "Preferred Stock") converted automatically into 1 share of Common Stock upon the closing of the Issuer's initial public offering without payment of further consideration. Share numbers give effect to such conversion. The Preferred Stock had no expiration date.

F1 · derivative.exercise_date: Each share of Series Seed Convertible Preferred Stock, Series A Convertible Preferred Stock, Series A-2 Convertible Preferred Stock and Series B Convertible Preferred Stock (collectively, the "Preferred Stock") converted automatically into 1 share of Common Stock upon the closing of the Issuer's initial public offering without payment of further consideration. Share numbers give effect to such conversion. The Preferred Stock had no expiration date.

F1 · derivative.expiration_date: Each share of Series Seed Convertible Preferred Stock, Series A Convertible Preferred Stock, Series A-2 Convertible Preferred Stock and Series B Convertible Preferred Stock (collectively, the "Preferred Stock") converted automatically into 1 share of Common Stock upon the closing of the Issuer's initial public offering without payment of further consideration. Share numbers give effect to such conversion. The Preferred Stock had no expiration date.

F3 · ownership.nature: Shares held directly by Westlake BioPartners Fund II, L.P. ("Fund II"). The general partner of Fund II is Westlake BioPartners GP II, LLC ("GP II"). GP II may be deemed to share voting and dispositive power with regard to the shares held directly by Fund II. Seidenberg is the sole managing director of GP II and has voting and dispositive power over the shares held by Fund II. Seidenberg disclaims Section 16 beneficial ownership of the shares reported herein except to the extent of her pecuniary interest therein, if any, and the inclusion of these shares in this report shall not be deemed an admission of beneficial ownership of any of the reported shares for purposes of Section 16 or any other purpose.

Read SEC document
August 10, 2026 Filed Aug 11, 2026 10:00 UTC Latigo Biotherapeutics, Inc. LTGO · Entity 4709 ConversionSeries A-2 Convertible Preferred Stock · Derivative 3,464,072 Not disclosed Not disclosed
Disclosure

SEC source: 0001104659-26-093633 · tm2622668-1_4seq1.xml · derivative · entry 11

Westlake BioPartners Fund I, L.P. · CIK 0001749591 · 10% owner

Westlake BioPartners GP I, LLC · CIK 0002007650 · 10% owner

Westlake BioPartners Fund II, L.P. · CIK 0001811947 · 10% owner

Westlake BioPartners GP II, LLC · CIK 0001811948 · 10% owner

Westlake BioPartners Opportunity Fund I, L.P. · CIK 0001811946 · 10% owner

Westlake BioPartners Opportunity GP I, LLC · CIK 0001811945 · 10% owner

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: No plan indicated

Ownership: Indirect · See footnote

Disclosed balance after: 0

Underlying: Common Stock · 3,464,072 shares

Expires not disclosed

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F1 · derivative.exercise_price: Each share of Series Seed Convertible Preferred Stock, Series A Convertible Preferred Stock, Series A-2 Convertible Preferred Stock and Series B Convertible Preferred Stock (collectively, the "Preferred Stock") converted automatically into 1 share of Common Stock upon the closing of the Issuer's initial public offering without payment of further consideration. Share numbers give effect to such conversion. The Preferred Stock had no expiration date.

F1 · price: Each share of Series Seed Convertible Preferred Stock, Series A Convertible Preferred Stock, Series A-2 Convertible Preferred Stock and Series B Convertible Preferred Stock (collectively, the "Preferred Stock") converted automatically into 1 share of Common Stock upon the closing of the Issuer's initial public offering without payment of further consideration. Share numbers give effect to such conversion. The Preferred Stock had no expiration date.

F1 · derivative.exercise_date: Each share of Series Seed Convertible Preferred Stock, Series A Convertible Preferred Stock, Series A-2 Convertible Preferred Stock and Series B Convertible Preferred Stock (collectively, the "Preferred Stock") converted automatically into 1 share of Common Stock upon the closing of the Issuer's initial public offering without payment of further consideration. Share numbers give effect to such conversion. The Preferred Stock had no expiration date.

F1 · derivative.expiration_date: Each share of Series Seed Convertible Preferred Stock, Series A Convertible Preferred Stock, Series A-2 Convertible Preferred Stock and Series B Convertible Preferred Stock (collectively, the "Preferred Stock") converted automatically into 1 share of Common Stock upon the closing of the Issuer's initial public offering without payment of further consideration. Share numbers give effect to such conversion. The Preferred Stock had no expiration date.

F3 · ownership.nature: Shares held directly by Westlake BioPartners Fund II, L.P. ("Fund II"). The general partner of Fund II is Westlake BioPartners GP II, LLC ("GP II"). GP II may be deemed to share voting and dispositive power with regard to the shares held directly by Fund II. Seidenberg is the sole managing director of GP II and has voting and dispositive power over the shares held by Fund II. Seidenberg disclaims Section 16 beneficial ownership of the shares reported herein except to the extent of her pecuniary interest therein, if any, and the inclusion of these shares in this report shall not be deemed an admission of beneficial ownership of any of the reported shares for purposes of Section 16 or any other purpose.

Read SEC document
August 10, 2026 Filed Aug 11, 2026 10:00 UTC Latigo Biotherapeutics, Inc. LTGO · Entity 4709 ConversionSeries A-2 Convertible Preferred Stock · Derivative 1,027,635 Not disclosed Not disclosed
Disclosure

SEC source: 0001104659-26-093633 · tm2622668-1_4seq1.xml · derivative · entry 10

Westlake BioPartners Fund I, L.P. · CIK 0001749591 · 10% owner

Westlake BioPartners GP I, LLC · CIK 0002007650 · 10% owner

Westlake BioPartners Fund II, L.P. · CIK 0001811947 · 10% owner

Westlake BioPartners GP II, LLC · CIK 0001811948 · 10% owner

Westlake BioPartners Opportunity Fund I, L.P. · CIK 0001811946 · 10% owner

Westlake BioPartners Opportunity GP I, LLC · CIK 0001811945 · 10% owner

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: No plan indicated

Ownership: Indirect · See footnote

Disclosed balance after: 0

Underlying: Common Stock · 1,027,635 shares

Expires not disclosed

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F1 · derivative.exercise_price: Each share of Series Seed Convertible Preferred Stock, Series A Convertible Preferred Stock, Series A-2 Convertible Preferred Stock and Series B Convertible Preferred Stock (collectively, the "Preferred Stock") converted automatically into 1 share of Common Stock upon the closing of the Issuer's initial public offering without payment of further consideration. Share numbers give effect to such conversion. The Preferred Stock had no expiration date.

F1 · price: Each share of Series Seed Convertible Preferred Stock, Series A Convertible Preferred Stock, Series A-2 Convertible Preferred Stock and Series B Convertible Preferred Stock (collectively, the "Preferred Stock") converted automatically into 1 share of Common Stock upon the closing of the Issuer's initial public offering without payment of further consideration. Share numbers give effect to such conversion. The Preferred Stock had no expiration date.

F1 · derivative.exercise_date: Each share of Series Seed Convertible Preferred Stock, Series A Convertible Preferred Stock, Series A-2 Convertible Preferred Stock and Series B Convertible Preferred Stock (collectively, the "Preferred Stock") converted automatically into 1 share of Common Stock upon the closing of the Issuer's initial public offering without payment of further consideration. Share numbers give effect to such conversion. The Preferred Stock had no expiration date.

F1 · derivative.expiration_date: Each share of Series Seed Convertible Preferred Stock, Series A Convertible Preferred Stock, Series A-2 Convertible Preferred Stock and Series B Convertible Preferred Stock (collectively, the "Preferred Stock") converted automatically into 1 share of Common Stock upon the closing of the Issuer's initial public offering without payment of further consideration. Share numbers give effect to such conversion. The Preferred Stock had no expiration date.

F2 · ownership.nature: Shares held directly by Westlake BioPartners Fund I, L.P. ("Fund I"). The general partner of Fund I is Westlake BioPartners GP I, LLC ("GP I"). GP I may be deemed to share voting and dispositive power with regard to the shares held directly by Fund I. Beth Seidenberg ("Seidenberg") is the sole managing director of GP I and has voting and dispositive power over the shares held by Fund I. Seidenberg disclaims Section 16 beneficial ownership of the shares reported herein except to the extent of her pecuniary interest therein, if any, and the inclusion of these shares in this report shall not be deemed an admission of beneficial ownership of any of the reported shares for purposes of Section 16 or any other purpose.

Read SEC document
August 10, 2026 Filed Aug 11, 2026 10:00 UTC Latigo Biotherapeutics, Inc. LTGO · Entity 4709 ConversionSeries A Convertible Preferred Stock · Derivative 3,547,842 Not disclosed Not disclosed
Disclosure

SEC source: 0001104659-26-093633 · tm2622668-1_4seq1.xml · derivative · entry 9

Westlake BioPartners Fund I, L.P. · CIK 0001749591 · 10% owner

Westlake BioPartners GP I, LLC · CIK 0002007650 · 10% owner

Westlake BioPartners Fund II, L.P. · CIK 0001811947 · 10% owner

Westlake BioPartners GP II, LLC · CIK 0001811948 · 10% owner

Westlake BioPartners Opportunity Fund I, L.P. · CIK 0001811946 · 10% owner

Westlake BioPartners Opportunity GP I, LLC · CIK 0001811945 · 10% owner

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: No plan indicated

Ownership: Indirect · See footnote

Disclosed balance after: 0

Underlying: Common Stock · 3,547,842 shares

Expires not disclosed

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F1 · derivative.exercise_price: Each share of Series Seed Convertible Preferred Stock, Series A Convertible Preferred Stock, Series A-2 Convertible Preferred Stock and Series B Convertible Preferred Stock (collectively, the "Preferred Stock") converted automatically into 1 share of Common Stock upon the closing of the Issuer's initial public offering without payment of further consideration. Share numbers give effect to such conversion. The Preferred Stock had no expiration date.

F1 · price: Each share of Series Seed Convertible Preferred Stock, Series A Convertible Preferred Stock, Series A-2 Convertible Preferred Stock and Series B Convertible Preferred Stock (collectively, the "Preferred Stock") converted automatically into 1 share of Common Stock upon the closing of the Issuer's initial public offering without payment of further consideration. Share numbers give effect to such conversion. The Preferred Stock had no expiration date.

F1 · derivative.exercise_date: Each share of Series Seed Convertible Preferred Stock, Series A Convertible Preferred Stock, Series A-2 Convertible Preferred Stock and Series B Convertible Preferred Stock (collectively, the "Preferred Stock") converted automatically into 1 share of Common Stock upon the closing of the Issuer's initial public offering without payment of further consideration. Share numbers give effect to such conversion. The Preferred Stock had no expiration date.

F1 · derivative.expiration_date: Each share of Series Seed Convertible Preferred Stock, Series A Convertible Preferred Stock, Series A-2 Convertible Preferred Stock and Series B Convertible Preferred Stock (collectively, the "Preferred Stock") converted automatically into 1 share of Common Stock upon the closing of the Issuer's initial public offering without payment of further consideration. Share numbers give effect to such conversion. The Preferred Stock had no expiration date.

F2 · ownership.nature: Shares held directly by Westlake BioPartners Fund I, L.P. ("Fund I"). The general partner of Fund I is Westlake BioPartners GP I, LLC ("GP I"). GP I may be deemed to share voting and dispositive power with regard to the shares held directly by Fund I. Beth Seidenberg ("Seidenberg") is the sole managing director of GP I and has voting and dispositive power over the shares held by Fund I. Seidenberg disclaims Section 16 beneficial ownership of the shares reported herein except to the extent of her pecuniary interest therein, if any, and the inclusion of these shares in this report shall not be deemed an admission of beneficial ownership of any of the reported shares for purposes of Section 16 or any other purpose.

Read SEC document
August 10, 2026 Filed Aug 11, 2026 10:00 UTC Latigo Biotherapeutics, Inc. LTGO · Entity 4709 ConversionSeries Seed Convertible Preferred Stock · Derivative 938,979 Not disclosed Not disclosed
Disclosure

SEC source: 0001104659-26-093633 · tm2622668-1_4seq1.xml · derivative · entry 8

Westlake BioPartners Fund I, L.P. · CIK 0001749591 · 10% owner

Westlake BioPartners GP I, LLC · CIK 0002007650 · 10% owner

Westlake BioPartners Fund II, L.P. · CIK 0001811947 · 10% owner

Westlake BioPartners GP II, LLC · CIK 0001811948 · 10% owner

Westlake BioPartners Opportunity Fund I, L.P. · CIK 0001811946 · 10% owner

Westlake BioPartners Opportunity GP I, LLC · CIK 0001811945 · 10% owner

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: No plan indicated

Ownership: Indirect · See footnote

Disclosed balance after: 0

Underlying: Common Stock · 938,979 shares

Expires not disclosed

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F1 · derivative.exercise_price: Each share of Series Seed Convertible Preferred Stock, Series A Convertible Preferred Stock, Series A-2 Convertible Preferred Stock and Series B Convertible Preferred Stock (collectively, the "Preferred Stock") converted automatically into 1 share of Common Stock upon the closing of the Issuer's initial public offering without payment of further consideration. Share numbers give effect to such conversion. The Preferred Stock had no expiration date.

F1 · price: Each share of Series Seed Convertible Preferred Stock, Series A Convertible Preferred Stock, Series A-2 Convertible Preferred Stock and Series B Convertible Preferred Stock (collectively, the "Preferred Stock") converted automatically into 1 share of Common Stock upon the closing of the Issuer's initial public offering without payment of further consideration. Share numbers give effect to such conversion. The Preferred Stock had no expiration date.

F1 · derivative.exercise_date: Each share of Series Seed Convertible Preferred Stock, Series A Convertible Preferred Stock, Series A-2 Convertible Preferred Stock and Series B Convertible Preferred Stock (collectively, the "Preferred Stock") converted automatically into 1 share of Common Stock upon the closing of the Issuer's initial public offering without payment of further consideration. Share numbers give effect to such conversion. The Preferred Stock had no expiration date.

F1 · derivative.expiration_date: Each share of Series Seed Convertible Preferred Stock, Series A Convertible Preferred Stock, Series A-2 Convertible Preferred Stock and Series B Convertible Preferred Stock (collectively, the "Preferred Stock") converted automatically into 1 share of Common Stock upon the closing of the Issuer's initial public offering without payment of further consideration. Share numbers give effect to such conversion. The Preferred Stock had no expiration date.

F2 · ownership.nature: Shares held directly by Westlake BioPartners Fund I, L.P. ("Fund I"). The general partner of Fund I is Westlake BioPartners GP I, LLC ("GP I"). GP I may be deemed to share voting and dispositive power with regard to the shares held directly by Fund I. Beth Seidenberg ("Seidenberg") is the sole managing director of GP I and has voting and dispositive power over the shares held by Fund I. Seidenberg disclaims Section 16 beneficial ownership of the shares reported herein except to the extent of her pecuniary interest therein, if any, and the inclusion of these shares in this report shall not be deemed an admission of beneficial ownership of any of the reported shares for purposes of Section 16 or any other purpose.

Read SEC document
August 10, 2026 Filed Aug 11, 2026 10:00 UTC Latigo Biotherapeutics, Inc. LTGO · Entity 4709 ConversionCommon Stock 2,066,857 Not disclosed Not disclosed
Disclosure

SEC source: 0001104659-26-093633 · tm2622668-1_4seq1.xml · nonDerivative · entry 7

Westlake BioPartners Fund I, L.P. · CIK 0001749591 · 10% owner

Westlake BioPartners GP I, LLC · CIK 0002007650 · 10% owner

Westlake BioPartners Fund II, L.P. · CIK 0001811947 · 10% owner

Westlake BioPartners GP II, LLC · CIK 0001811948 · 10% owner

Westlake BioPartners Opportunity Fund I, L.P. · CIK 0001811946 · 10% owner

Westlake BioPartners Opportunity GP I, LLC · CIK 0001811945 · 10% owner

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: No plan indicated

Ownership: Indirect · See footnote

Disclosed balance after: 2,094,813

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F1 · price: Each share of Series Seed Convertible Preferred Stock, Series A Convertible Preferred Stock, Series A-2 Convertible Preferred Stock and Series B Convertible Preferred Stock (collectively, the "Preferred Stock") converted automatically into 1 share of Common Stock upon the closing of the Issuer's initial public offering without payment of further consideration. Share numbers give effect to such conversion. The Preferred Stock had no expiration date.

F5 · ownership.nature: Shares held directly by Westlake BioPartners Opportunity Fund I, L.P. ("Opportunity Fund"). The general partner of Opportunity Fund is Westlake BioPartners Opportunity GP I, LLC ("Opportunity GP"). Opportunity GP may be deemed to share voting and dispositive power with regard to the shares held directly by Opportunity Fund. Seidenberg is the sole managing director of Opportunity GP and has voting and dispositive power over the shares held by Opportunity Fund. Seidenberg disclaims Section 16 beneficial ownership of the shares reported herein except to the extent of her pecuniary interest therein, if any, and the inclusion of these shares in this report shall not be deemed an admission of beneficial ownership of any of the reported shares for purposes of Section 16 or any other purpose.

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August 10, 2026 Filed Aug 11, 2026 10:00 UTC Latigo Biotherapeutics, Inc. LTGO · Entity 4709 ConversionCommon Stock 165,519 Not disclosed Not disclosed
Disclosure

SEC source: 0001104659-26-093633 · tm2622668-1_4seq1.xml · nonDerivative · entry 6

Westlake BioPartners Fund I, L.P. · CIK 0001749591 · 10% owner

Westlake BioPartners GP I, LLC · CIK 0002007650 · 10% owner

Westlake BioPartners Fund II, L.P. · CIK 0001811947 · 10% owner

Westlake BioPartners GP II, LLC · CIK 0001811948 · 10% owner

Westlake BioPartners Opportunity Fund I, L.P. · CIK 0001811946 · 10% owner

Westlake BioPartners Opportunity GP I, LLC · CIK 0001811945 · 10% owner

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: No plan indicated

Ownership: Indirect · See footnote

Disclosed balance after: 5,160,847

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F4 · price: Reflects a convertible note that was convertible into shares of Common Stock of the Issuer. The convertible note had a maturity date of June 17, 2027. The principal amount of the convertible note together with any accrued but unpaid interest automatically converted into shares of Common Stock of the Issuer upon the closing of the Issuer's initial public offering at a conversion price equal to the initial public offering price of the Issuer's common stock.

F3 · ownership.nature: Shares held directly by Westlake BioPartners Fund II, L.P. ("Fund II"). The general partner of Fund II is Westlake BioPartners GP II, LLC ("GP II"). GP II may be deemed to share voting and dispositive power with regard to the shares held directly by Fund II. Seidenberg is the sole managing director of GP II and has voting and dispositive power over the shares held by Fund II. Seidenberg disclaims Section 16 beneficial ownership of the shares reported herein except to the extent of her pecuniary interest therein, if any, and the inclusion of these shares in this report shall not be deemed an admission of beneficial ownership of any of the reported shares for purposes of Section 16 or any other purpose.

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August 10, 2026 Filed Aug 11, 2026 10:00 UTC Latigo Biotherapeutics, Inc. LTGO · Entity 4709 ConversionCommon Stock 1,484,401 Not disclosed Not disclosed
Disclosure

SEC source: 0001104659-26-093633 · tm2622668-1_4seq1.xml · nonDerivative · entry 5

Westlake BioPartners Fund I, L.P. · CIK 0001749591 · 10% owner

Westlake BioPartners GP I, LLC · CIK 0002007650 · 10% owner

Westlake BioPartners Fund II, L.P. · CIK 0001811947 · 10% owner

Westlake BioPartners GP II, LLC · CIK 0001811948 · 10% owner

Westlake BioPartners Opportunity Fund I, L.P. · CIK 0001811946 · 10% owner

Westlake BioPartners Opportunity GP I, LLC · CIK 0001811945 · 10% owner

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: No plan indicated

Ownership: Indirect · See footnote

Disclosed balance after: 4,995,328

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F1 · price: Each share of Series Seed Convertible Preferred Stock, Series A Convertible Preferred Stock, Series A-2 Convertible Preferred Stock and Series B Convertible Preferred Stock (collectively, the "Preferred Stock") converted automatically into 1 share of Common Stock upon the closing of the Issuer's initial public offering without payment of further consideration. Share numbers give effect to such conversion. The Preferred Stock had no expiration date.

F3 · ownership.nature: Shares held directly by Westlake BioPartners Fund II, L.P. ("Fund II"). The general partner of Fund II is Westlake BioPartners GP II, LLC ("GP II"). GP II may be deemed to share voting and dispositive power with regard to the shares held directly by Fund II. Seidenberg is the sole managing director of GP II and has voting and dispositive power over the shares held by Fund II. Seidenberg disclaims Section 16 beneficial ownership of the shares reported herein except to the extent of her pecuniary interest therein, if any, and the inclusion of these shares in this report shall not be deemed an admission of beneficial ownership of any of the reported shares for purposes of Section 16 or any other purpose.

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August 10, 2026 Filed Aug 11, 2026 10:00 UTC Latigo Biotherapeutics, Inc. LTGO · Entity 4709 ConversionCommon Stock 3,464,072 Not disclosed Not disclosed
Disclosure

SEC source: 0001104659-26-093633 · tm2622668-1_4seq1.xml · nonDerivative · entry 4

Westlake BioPartners Fund I, L.P. · CIK 0001749591 · 10% owner

Westlake BioPartners GP I, LLC · CIK 0002007650 · 10% owner

Westlake BioPartners Fund II, L.P. · CIK 0001811947 · 10% owner

Westlake BioPartners GP II, LLC · CIK 0001811948 · 10% owner

Westlake BioPartners Opportunity Fund I, L.P. · CIK 0001811946 · 10% owner

Westlake BioPartners Opportunity GP I, LLC · CIK 0001811945 · 10% owner

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: No plan indicated

Ownership: Indirect · See footnote

Disclosed balance after: 3,510,927

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F1 · price: Each share of Series Seed Convertible Preferred Stock, Series A Convertible Preferred Stock, Series A-2 Convertible Preferred Stock and Series B Convertible Preferred Stock (collectively, the "Preferred Stock") converted automatically into 1 share of Common Stock upon the closing of the Issuer's initial public offering without payment of further consideration. Share numbers give effect to such conversion. The Preferred Stock had no expiration date.

F3 · ownership.nature: Shares held directly by Westlake BioPartners Fund II, L.P. ("Fund II"). The general partner of Fund II is Westlake BioPartners GP II, LLC ("GP II"). GP II may be deemed to share voting and dispositive power with regard to the shares held directly by Fund II. Seidenberg is the sole managing director of GP II and has voting and dispositive power over the shares held by Fund II. Seidenberg disclaims Section 16 beneficial ownership of the shares reported herein except to the extent of her pecuniary interest therein, if any, and the inclusion of these shares in this report shall not be deemed an admission of beneficial ownership of any of the reported shares for purposes of Section 16 or any other purpose.

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August 10, 2026 Filed Aug 11, 2026 10:00 UTC Latigo Biotherapeutics, Inc. LTGO · Entity 4709 ConversionCommon Stock 1,027,635 Not disclosed Not disclosed
Disclosure

SEC source: 0001104659-26-093633 · tm2622668-1_4seq1.xml · nonDerivative · entry 3

Westlake BioPartners Fund I, L.P. · CIK 0001749591 · 10% owner

Westlake BioPartners GP I, LLC · CIK 0002007650 · 10% owner

Westlake BioPartners Fund II, L.P. · CIK 0001811947 · 10% owner

Westlake BioPartners GP II, LLC · CIK 0001811948 · 10% owner

Westlake BioPartners Opportunity Fund I, L.P. · CIK 0001811946 · 10% owner

Westlake BioPartners Opportunity GP I, LLC · CIK 0001811945 · 10% owner

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: No plan indicated

Ownership: Indirect · See footnote

Disclosed balance after: 5,944,009

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F1 · price: Each share of Series Seed Convertible Preferred Stock, Series A Convertible Preferred Stock, Series A-2 Convertible Preferred Stock and Series B Convertible Preferred Stock (collectively, the "Preferred Stock") converted automatically into 1 share of Common Stock upon the closing of the Issuer's initial public offering without payment of further consideration. Share numbers give effect to such conversion. The Preferred Stock had no expiration date.

F2 · ownership.nature: Shares held directly by Westlake BioPartners Fund I, L.P. ("Fund I"). The general partner of Fund I is Westlake BioPartners GP I, LLC ("GP I"). GP I may be deemed to share voting and dispositive power with regard to the shares held directly by Fund I. Beth Seidenberg ("Seidenberg") is the sole managing director of GP I and has voting and dispositive power over the shares held by Fund I. Seidenberg disclaims Section 16 beneficial ownership of the shares reported herein except to the extent of her pecuniary interest therein, if any, and the inclusion of these shares in this report shall not be deemed an admission of beneficial ownership of any of the reported shares for purposes of Section 16 or any other purpose.

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August 10, 2026 Filed Aug 11, 2026 10:00 UTC Latigo Biotherapeutics, Inc. LTGO · Entity 4709 ConversionCommon Stock 3,547,842 Not disclosed Not disclosed
Disclosure

SEC source: 0001104659-26-093633 · tm2622668-1_4seq1.xml · nonDerivative · entry 2

Westlake BioPartners Fund I, L.P. · CIK 0001749591 · 10% owner

Westlake BioPartners GP I, LLC · CIK 0002007650 · 10% owner

Westlake BioPartners Fund II, L.P. · CIK 0001811947 · 10% owner

Westlake BioPartners GP II, LLC · CIK 0001811948 · 10% owner

Westlake BioPartners Opportunity Fund I, L.P. · CIK 0001811946 · 10% owner

Westlake BioPartners Opportunity GP I, LLC · CIK 0001811945 · 10% owner

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: No plan indicated

Ownership: Indirect · See footnote

Disclosed balance after: 4,916,374

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F1 · price: Each share of Series Seed Convertible Preferred Stock, Series A Convertible Preferred Stock, Series A-2 Convertible Preferred Stock and Series B Convertible Preferred Stock (collectively, the "Preferred Stock") converted automatically into 1 share of Common Stock upon the closing of the Issuer's initial public offering without payment of further consideration. Share numbers give effect to such conversion. The Preferred Stock had no expiration date.

F2 · ownership.nature: Shares held directly by Westlake BioPartners Fund I, L.P. ("Fund I"). The general partner of Fund I is Westlake BioPartners GP I, LLC ("GP I"). GP I may be deemed to share voting and dispositive power with regard to the shares held directly by Fund I. Beth Seidenberg ("Seidenberg") is the sole managing director of GP I and has voting and dispositive power over the shares held by Fund I. Seidenberg disclaims Section 16 beneficial ownership of the shares reported herein except to the extent of her pecuniary interest therein, if any, and the inclusion of these shares in this report shall not be deemed an admission of beneficial ownership of any of the reported shares for purposes of Section 16 or any other purpose.

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August 10, 2026 Filed Aug 11, 2026 10:00 UTC Latigo Biotherapeutics, Inc. LTGO · Entity 4709 ConversionCommon Stock 938,979 Not disclosed Not disclosed
Disclosure

SEC source: 0001104659-26-093633 · tm2622668-1_4seq1.xml · nonDerivative · entry 1

Westlake BioPartners Fund I, L.P. · CIK 0001749591 · 10% owner

Westlake BioPartners GP I, LLC · CIK 0002007650 · 10% owner

Westlake BioPartners Fund II, L.P. · CIK 0001811947 · 10% owner

Westlake BioPartners GP II, LLC · CIK 0001811948 · 10% owner

Westlake BioPartners Opportunity Fund I, L.P. · CIK 0001811946 · 10% owner

Westlake BioPartners Opportunity GP I, LLC · CIK 0001811945 · 10% owner

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: No plan indicated

Ownership: Indirect · See footnote

Disclosed balance after: 1,368,532

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F1 · price: Each share of Series Seed Convertible Preferred Stock, Series A Convertible Preferred Stock, Series A-2 Convertible Preferred Stock and Series B Convertible Preferred Stock (collectively, the "Preferred Stock") converted automatically into 1 share of Common Stock upon the closing of the Issuer's initial public offering without payment of further consideration. Share numbers give effect to such conversion. The Preferred Stock had no expiration date.

F2 · ownership.nature: Shares held directly by Westlake BioPartners Fund I, L.P. ("Fund I"). The general partner of Fund I is Westlake BioPartners GP I, LLC ("GP I"). GP I may be deemed to share voting and dispositive power with regard to the shares held directly by Fund I. Beth Seidenberg ("Seidenberg") is the sole managing director of GP I and has voting and dispositive power over the shares held by Fund I. Seidenberg disclaims Section 16 beneficial ownership of the shares reported herein except to the extent of her pecuniary interest therein, if any, and the inclusion of these shares in this report shall not be deemed an admission of beneficial ownership of any of the reported shares for purposes of Section 16 or any other purpose.

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May 09, 2023 Filed May 11, 2023 21:16 UTC ACELYRIN, Inc. SLRN · Entity 79310 ConversionSeries C Redeemable Convertible Preferred Stock · Derivative 2,038,148 Not disclosed Not disclosed
Disclosure

SEC source: 0001209191-23-028886 · doc4.xml · derivative · entry 5

Westlake BioPartners Fund II, L.P. · CIK 0001811947 · 10% owner

Westlake BioPartners GP II, LLC · CIK 0001811948 · 10% owner

Harper Sean E · CIK 0001541946 · 10% owner

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 0

Underlying: Common Stock · 2,038,148 shares

Expires not disclosed

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F5 · derivative.exercise_price: Each share of preferred stock is convertible into one share of Common Stock and has no expiration date. Immediately prior to the completion of the IPO, all shares of preferred stock automatically converted into shares of Common Stock.

F5 · price: Each share of preferred stock is convertible into one share of Common Stock and has no expiration date. Immediately prior to the completion of the IPO, all shares of preferred stock automatically converted into shares of Common Stock.

F5 · derivative.exercise_date: Each share of preferred stock is convertible into one share of Common Stock and has no expiration date. Immediately prior to the completion of the IPO, all shares of preferred stock automatically converted into shares of Common Stock.

F5 · derivative.expiration_date: Each share of preferred stock is convertible into one share of Common Stock and has no expiration date. Immediately prior to the completion of the IPO, all shares of preferred stock automatically converted into shares of Common Stock.

F6 · derivative.underlying: Each share of Class A Common Stock was reclassified into one share of Common Stock immediately prior to the completion of the IPO.

F2 · ownership.direct: Shares held directly by Westlake BioPartners Fund II, L.P., or Westlake Fund II. Westlake BioPartners GP II, LLC, or Westlake GP II, is the general partner of Westlake Fund II. Westlake GP II may be deemed to have sole voting and dispositive power with regard to the shares held directly by Westlake Fund II. Beth C. Seidenberg and Sean E. Harper are the Managing Directors of Westlake GP II and share voting and dispositive power over the shares held by Westlake Fund II, each of whom disclaims beneficial ownership of the shares held by Westlake Fund II except to the extent of such person's pecuniary interest therein, if any.

F3 · ownership.direct: This report on Form 4 is jointly filed by Westlake Fund II, Westlake GP II and Sean E. Harper. Each of the Reporting Persons disclaims beneficial ownership of the securities reported herein for purposes of Rule 16a-1(a) under the Securities Exchange Act of 1934, as amended (the "Exchange Act"), except to the extent of such person's or entity's pecuniary interest therein, if any. Westlake Fund II has designated a representative, Beth C. Seidenberg, a Managing Director of Westlake GP II, to serve on the Issuer's board of directors. This report shall not be deemed an admission that any such entity or person is a beneficial owner of such securities for the purposes of Section 16 of the Exchange Act, or for any other purpose.

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May 09, 2023 Filed May 11, 2023 21:16 UTC ACELYRIN, Inc. SLRN · Entity 79310 ConversionSeries B Redeemable Convertible Preferred Stock · Derivative 2,445,786 Not disclosed Not disclosed
Disclosure

SEC source: 0001209191-23-028886 · doc4.xml · derivative · entry 4

Westlake BioPartners Fund II, L.P. · CIK 0001811947 · 10% owner

Westlake BioPartners GP II, LLC · CIK 0001811948 · 10% owner

Harper Sean E · CIK 0001541946 · 10% owner

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 0

Underlying: Common Stock · 2,445,786 shares

Expires not disclosed

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F5 · derivative.exercise_price: Each share of preferred stock is convertible into one share of Common Stock and has no expiration date. Immediately prior to the completion of the IPO, all shares of preferred stock automatically converted into shares of Common Stock.

F5 · price: Each share of preferred stock is convertible into one share of Common Stock and has no expiration date. Immediately prior to the completion of the IPO, all shares of preferred stock automatically converted into shares of Common Stock.

F5 · derivative.exercise_date: Each share of preferred stock is convertible into one share of Common Stock and has no expiration date. Immediately prior to the completion of the IPO, all shares of preferred stock automatically converted into shares of Common Stock.

F5 · derivative.expiration_date: Each share of preferred stock is convertible into one share of Common Stock and has no expiration date. Immediately prior to the completion of the IPO, all shares of preferred stock automatically converted into shares of Common Stock.

F6 · derivative.underlying: Each share of Class A Common Stock was reclassified into one share of Common Stock immediately prior to the completion of the IPO.

F2 · ownership.direct: Shares held directly by Westlake BioPartners Fund II, L.P., or Westlake Fund II. Westlake BioPartners GP II, LLC, or Westlake GP II, is the general partner of Westlake Fund II. Westlake GP II may be deemed to have sole voting and dispositive power with regard to the shares held directly by Westlake Fund II. Beth C. Seidenberg and Sean E. Harper are the Managing Directors of Westlake GP II and share voting and dispositive power over the shares held by Westlake Fund II, each of whom disclaims beneficial ownership of the shares held by Westlake Fund II except to the extent of such person's pecuniary interest therein, if any.

F3 · ownership.direct: This report on Form 4 is jointly filed by Westlake Fund II, Westlake GP II and Sean E. Harper. Each of the Reporting Persons disclaims beneficial ownership of the securities reported herein for purposes of Rule 16a-1(a) under the Securities Exchange Act of 1934, as amended (the "Exchange Act"), except to the extent of such person's or entity's pecuniary interest therein, if any. Westlake Fund II has designated a representative, Beth C. Seidenberg, a Managing Director of Westlake GP II, to serve on the Issuer's board of directors. This report shall not be deemed an admission that any such entity or person is a beneficial owner of such securities for the purposes of Section 16 of the Exchange Act, or for any other purpose.

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May 09, 2023 Filed May 11, 2023 21:16 UTC ACELYRIN, Inc. SLRN · Entity 79310 ConversionSeries A Redeemable Convertible Preferred Stock · Derivative 4,056,795 Not disclosed Not disclosed
Disclosure

SEC source: 0001209191-23-028886 · doc4.xml · derivative · entry 3

Westlake BioPartners Fund II, L.P. · CIK 0001811947 · 10% owner

Westlake BioPartners GP II, LLC · CIK 0001811948 · 10% owner

Harper Sean E · CIK 0001541946 · 10% owner

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 0

Underlying: Common Stock · 4,056,795 shares

Expires not disclosed

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F5 · derivative.exercise_price: Each share of preferred stock is convertible into one share of Common Stock and has no expiration date. Immediately prior to the completion of the IPO, all shares of preferred stock automatically converted into shares of Common Stock.

F5 · price: Each share of preferred stock is convertible into one share of Common Stock and has no expiration date. Immediately prior to the completion of the IPO, all shares of preferred stock automatically converted into shares of Common Stock.

F5 · derivative.exercise_date: Each share of preferred stock is convertible into one share of Common Stock and has no expiration date. Immediately prior to the completion of the IPO, all shares of preferred stock automatically converted into shares of Common Stock.

F5 · derivative.expiration_date: Each share of preferred stock is convertible into one share of Common Stock and has no expiration date. Immediately prior to the completion of the IPO, all shares of preferred stock automatically converted into shares of Common Stock.

F6 · derivative.underlying: Each share of Class A Common Stock was reclassified into one share of Common Stock immediately prior to the completion of the IPO.

F2 · ownership.direct: Shares held directly by Westlake BioPartners Fund II, L.P., or Westlake Fund II. Westlake BioPartners GP II, LLC, or Westlake GP II, is the general partner of Westlake Fund II. Westlake GP II may be deemed to have sole voting and dispositive power with regard to the shares held directly by Westlake Fund II. Beth C. Seidenberg and Sean E. Harper are the Managing Directors of Westlake GP II and share voting and dispositive power over the shares held by Westlake Fund II, each of whom disclaims beneficial ownership of the shares held by Westlake Fund II except to the extent of such person's pecuniary interest therein, if any.

F3 · ownership.direct: This report on Form 4 is jointly filed by Westlake Fund II, Westlake GP II and Sean E. Harper. Each of the Reporting Persons disclaims beneficial ownership of the securities reported herein for purposes of Rule 16a-1(a) under the Securities Exchange Act of 1934, as amended (the "Exchange Act"), except to the extent of such person's or entity's pecuniary interest therein, if any. Westlake Fund II has designated a representative, Beth C. Seidenberg, a Managing Director of Westlake GP II, to serve on the Issuer's board of directors. This report shall not be deemed an admission that any such entity or person is a beneficial owner of such securities for the purposes of Section 16 of the Exchange Act, or for any other purpose.

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May 09, 2023 Filed May 11, 2023 21:16 UTC ACELYRIN, Inc. SLRN · Entity 79310 PurchaseCommon Stock 1,250,000 $18.00 $22,500,000.00
Disclosure

SEC source: 0001209191-23-028886 · doc4.xml · nonDerivative · entry 2

Westlake BioPartners Fund II, L.P. · CIK 0001811947 · 10% owner

Westlake BioPartners GP II, LLC · CIK 0001811948 · 10% owner

Harper Sean E · CIK 0001541946 · 10% owner

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 9,790,729

F4 · kind: Represents shares of Common Stock purchased in the Issuer's initial public offering of Common Stock (the "IPO").

F2 · ownership.direct: Shares held directly by Westlake BioPartners Fund II, L.P., or Westlake Fund II. Westlake BioPartners GP II, LLC, or Westlake GP II, is the general partner of Westlake Fund II. Westlake GP II may be deemed to have sole voting and dispositive power with regard to the shares held directly by Westlake Fund II. Beth C. Seidenberg and Sean E. Harper are the Managing Directors of Westlake GP II and share voting and dispositive power over the shares held by Westlake Fund II, each of whom disclaims beneficial ownership of the shares held by Westlake Fund II except to the extent of such person's pecuniary interest therein, if any.

F3 · ownership.direct: This report on Form 4 is jointly filed by Westlake Fund II, Westlake GP II and Sean E. Harper. Each of the Reporting Persons disclaims beneficial ownership of the securities reported herein for purposes of Rule 16a-1(a) under the Securities Exchange Act of 1934, as amended (the "Exchange Act"), except to the extent of such person's or entity's pecuniary interest therein, if any. Westlake Fund II has designated a representative, Beth C. Seidenberg, a Managing Director of Westlake GP II, to serve on the Issuer's board of directors. This report shall not be deemed an admission that any such entity or person is a beneficial owner of such securities for the purposes of Section 16 of the Exchange Act, or for any other purpose.

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May 09, 2023 Filed May 11, 2023 21:16 UTC ACELYRIN, Inc. SLRN · Entity 79310 ConversionCommon Stock 8,540,729 Not disclosed Not disclosed
Disclosure

SEC source: 0001209191-23-028886 · doc4.xml · nonDerivative · entry 1

Westlake BioPartners Fund II, L.P. · CIK 0001811947 · 10% owner

Westlake BioPartners GP II, LLC · CIK 0001811948 · 10% owner

Harper Sean E · CIK 0001541946 · 10% owner

Joint disclosure: these amounts are not allocated separately to each reporting owner.

10b5-1 filing: No plan indicated

Ownership: Direct

Disclosed balance after: 8,540,729

Exercise/conversion can include RSU settlement. Transaction price and option strike are different fields; a missing price is not zero. Derivative and underlying rows can describe the same event.

F1 · kind: Represents shares of Common Stock received upon conversion of shares of the reported series of preferred stock on a one-for-one basis without payment of further consideration.

F1 · price: Represents shares of Common Stock received upon conversion of shares of the reported series of preferred stock on a one-for-one basis without payment of further consideration.

F2 · ownership.direct: Shares held directly by Westlake BioPartners Fund II, L.P., or Westlake Fund II. Westlake BioPartners GP II, LLC, or Westlake GP II, is the general partner of Westlake Fund II. Westlake GP II may be deemed to have sole voting and dispositive power with regard to the shares held directly by Westlake Fund II. Beth C. Seidenberg and Sean E. Harper are the Managing Directors of Westlake GP II and share voting and dispositive power over the shares held by Westlake Fund II, each of whom disclaims beneficial ownership of the shares held by Westlake Fund II except to the extent of such person's pecuniary interest therein, if any.

F3 · ownership.direct: This report on Form 4 is jointly filed by Westlake Fund II, Westlake GP II and Sean E. Harper. Each of the Reporting Persons disclaims beneficial ownership of the securities reported herein for purposes of Rule 16a-1(a) under the Securities Exchange Act of 1934, as amended (the "Exchange Act"), except to the extent of such person's or entity's pecuniary interest therein, if any. Westlake Fund II has designated a representative, Beth C. Seidenberg, a Managing Director of Westlake GP II, to serve on the Issuer's board of directors. This report shall not be deemed an admission that any such entity or person is a beneficial owner of such securities for the purposes of Section 16 of the Exchange Act, or for any other purpose.

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Value uses the disclosed total when available, otherwise shares × reported transaction price. It is not an estimate of exercise cash cost or investment performance.