Gossamer Bio (GOSS) investor relations material

Executive summary

• Special Meeting called to approve share issuances related to a private placement and to allow adjournment if needed.

• Private placement involves pre-funded warrants and preferred stock convertible to common stock, contingent on stockholder approval.

• Reverse stock split (1-for-80) was effected on September 10, 2026, impacting all share calculations.

• Board unanimously recommends voting in favor of both proposals.

Voting matters and shareholder proposals

• Proposal 1 seeks approval for issuance of common stock upon exercise/conversion of warrants and preferred stock, exceeding 20% of pre-transaction shares.

• Proposal 2 allows adjournment of the meeting to solicit more proxies if necessary.

• Only stockholders of record as of September 14, 2026, are eligible to vote.

• Stockholder proposals for the 2027 annual meeting must be received by December 25, 2026, for inclusion.

Board of directors and corporate governance

• Board includes recent appointee Gregory A. Ciongoli, who is also a purchaser in the private placement.

• Board members and certain executives are participating in the private placement through controlled entities.

• Board recommends voting “FOR” both proposals.