A Schedule 13G filed with the SEC, with a triggering event date of September 30, 2026, discloses that Dr. Beth C. Seidenberg and affiliated Westlake BioPartners entities collectively hold beneficial ownership of 13,199,669 shares of Latigo Biotherapeutics, Inc. common stock, representing 19.9% of the class.

Key Highlights

  • Total beneficial ownership: Dr. Beth C. Seidenberg reported aggregate beneficial ownership of 13,199,669 shares of Latigo Biotherapeutics, Inc. common stock, equal to 19.9% of the class.
  • Fund I position: Westlake BioPartners Fund I, L.P. directly holds 5,944,009 shares, representing 9.0% of the class.
  • Fund II position: Westlake BioPartners Fund II, L.P. directly holds 5,160,847 shares, representing 7.8% of the class.
  • Opportunity Fund I position: Westlake BioPartners Opportunity Fund I, L.P. directly holds 2,094,813 shares, representing 3.2% of the class.
  • Triggering event date: The filing identifies September 30, 2026 as the date of the event requiring this statement.
  • Security reported: Common Stock, par value $0.0001 per share, CUSIP 517954103.

Westlake BioPartners Entities and Seidenberg Ownership Structure in Latigo Biotherapeutics

According to the Schedule 13G, Dr. Beth C. Seidenberg is identified as the sole managing director of three general partner entities: Westlake BioPartners GP I, LLC, Westlake BioPartners GP II, LLC, and Westlake BioPartners Opportunity GP I, LLC. Each of these general partners controls a corresponding limited partnership that directly holds shares in Latigo Biotherapeutics, Inc. The filing states that the shares held by each fund "may be deemed" to be subject to sole voting and dispositive power by both the relevant general partner and by Seidenberg in her capacity as sole managing director.

The filing reports that Westlake BioPartners Fund I, L.P. holds 5,944,009 shares (9.0%), Westlake BioPartners Fund II, L.P. holds 5,160,847 shares (7.8%), and Westlake BioPartners Opportunity Fund I, L.P. holds 2,094,813 shares (3.2%). Taken together, these positions account for the 13,199,669 aggregate shares attributed to Seidenberg, representing 19.9% of the outstanding common stock of Latigo Biotherapeutics, Inc. All six reporting entities listed in the filing are organized in Delaware, while Seidenberg is identified as a United States citizen.

Each of the three fund-level reporting persons is classified as a limited partnership (type "PN"), and each corresponding general partner entity is classified as type "OO" (other). Seidenberg is classified as an individual (type "IN"). The filing does not specify a purchase price, transaction date, or total consideration paid for the shares disclosed.

What Was Disclosed

The Schedule 13G discloses that three Westlake BioPartners funds, their general partners, and Dr. Beth C. Seidenberg hold a combined 13,199,669 shares, or 19.9%, of Latigo Biotherapeutics, Inc. common stock as of September 30, 2026.