---
schema_version: "secwatch.filing_event.v1"
accession: "0001193125-24-237580"
form_type: "8-K"
ticker: "UPB"
cik: "0002022626"
company_name: "Upstream Bio, Inc."
filed_at: "2024-10-15T23:59:59+00:00"
generated_at: "2026-05-30T14:57:00.132577+00:00"
event_type: "other_material"
sentiment: "neutral"
materiality_score: 0.2
calibrated_materiality_score: 0.2
confidence: "high"
source: SEC EDGAR
---

# Upstream Bio files amended charter and bylaws following IPO completion

## Summary
- Authorizes 500M shares of common stock and 10M shares of undesignated preferred stock.
- Eliminates stockholder ability to act by written consent and call special meetings.
- Establishes advance notice procedures for stockholder proposals and director nominations.
- Amendments effective upon IPO completion on October 10 and October 15, 2024.

## SEC filing metadata
- accession: 0001193125-24-237580
- form_type: 8-K
- ticker: UPB
- cik: 0002022626
- company_name: Upstream Bio, Inc.
- filed_at: 2024-10-15T23:59:59+00:00
- event_type: other_material
- sentiment: neutral
- materiality_score: 0.2
- calibrated_materiality_score: 0.2
- confidence: high
- sec_items: 5.03, 9.01
- EDGAR index: https://www.sec.gov/Archives/edgar/data/2022626/000119312524237580/0001193125-24-237580-index.htm
- EDGAR primary document: https://www.sec.gov/Archives/edgar/data/2022626/000119312524237580/d897785d8k.htm

## Machine-readable alternates
- HTML: https://secwatch.observer/filing/0001193125-24-237580
- JSON: https://secwatch.observer/filing/0001193125-24-237580.json
- Plain text: https://secwatch.observer/filing/0001193125-24-237580.txt

## Key facts
- Governance Changes
  Upstream Bio, Inc.: Second amended and restated bylaws became effective, eliminating stockholder ability to act by written consent, establishing advance notice procedure for stockholder proposals, and conforming to amended certificate (effective 2024-10-10).
  - Change: bylaw amendment
  - Effective: 2024-10-10
  source text: In addition, as previously disclosed in the Registration Statement, the second amended and restated bylaws of the Company (the “Amended and Restated Bylaws”), previously approved by the Board and the Company’s stockholders, became effective as of the effectiveness of the Registration Statement on October 10, 2024. The Amended and Restated Bylaws amend and restate the Company’s bylaws in their entirety to, among other things: (i) eliminate the ability of the Company’s stockholders to take action by written consent in lieu of a meeting and call special meetings of stockholders; (ii) establish an advance notice procedure for stockholder proposals to be brought before an annual meeting of our stockholders, including proposed nominations of persons for election to our Board; and (iii) conform to the amended provisions of the Amended and Restated Certificate.
  evidence_url: https://www.sec.gov/Archives/edgar/data/2022626/000119312524237580/0001193125-24-237580-index.htm
- Governance Changes
  Upstream Bio, Inc.: Third amended and restated certificate of incorporation filed to increase authorized common stock to 500 million shares, eliminate references to previous series of preferred stock, and authorize 10 million shares of undesignated preferred stock (effective 2024-10-15).
  - Change: charter amendment
  - Effective: 2024-10-15
  source text: As previously disclosed in the Registration Statement on Form S-1, as amended (File No. 333-282197) (the “Registration Statement”), of Upstream Bio, Inc. (the “Company”), and in connection with the completion of the initial public offering of the Company’s common stock (the “IPO”), on October 15, 2024, the Company filed its third amended and restated certificate of incorporation (the “Amended and Restated Certificate”) with the Secretary of State of the State of Delaware. The Company’s board of directors (the “Board”) and the Company’s stockholders previously approved the Amended and Restated Certificate to be filed in connection with, and to be effective immediately prior to, the completion of the IPO. The Amended and Restated Certificate amends and restates the Company’s existing second amended and restated certificate of incorporation, as amended, in its entirety to, among other things: (i) authorize 500,000,000 shares of common stock; (ii) eliminate all references to the previously
  evidence_url: https://www.sec.gov/Archives/edgar/data/2022626/000119312524237580/0001193125-24-237580-index.htm

This AI-assisted summary is a reading aid. Review the linked SEC EDGAR filing before relying on any specific claim.