Upstream Bio, Inc. reports a Schedule 13G/A amendment disclosing shared beneficial ownership by Decheng entities. The amendment states that 2,724,868 shares of Common Stock were beneficially owned by Decheng Capital Global Life Sciences Fund IV, L.P. as of March 31, 2026, representing 5.0% of the class based on 54,419,986 shares outstanding as of March 20, 2026. The filing explains that voting and dispositive authority over those shares is shared by GP entities and that Dr. Xiangmin Cui holds managerial authority.
Positive
None.
Negative
None.
Insights
Large passive stake disclosed by Decheng group; governance influence is shared.
The filing shows 2,724,868 shares held directly by Fund IV with shared voting and dispositive power among affiliated GP entities and Dr. Xiangmin Cui. This identifies the chain of control without asserting unilateral control.
Implications depend on future filings or transactions; subsequent disclosures would clarify whether this position remains passive or leads to active engagement.
Amendment clarifies beneficial ownership and authority roles under Schedule 13G/A rules.
The amendment incorporates cover-page figures and ties percentages to the issuer's reported 54,419,986 shares outstanding as of March 20, 2026. It states the Reporting Persons disclaim ‘‘group’’ status and documents shared authorities, aligning with Form disclosure mechanics.
Filing signatures dated May 15, 2026 complete the amendment; future Forms (13D/13G) would reflect any change in intent or control.
Key Figures
Decheng shares held:2,724,868 sharesPercent of class:5.0%Shares outstanding (issuer):54,419,986 shares
3 metrics
Decheng shares held2,724,868 sharesBeneficial ownership as of March 31, 2026
Percent of class5.0%Calculated using 54,419,986 shares outstanding as of March 20, 2026
Shares outstanding (issuer)54,419,986 sharesAs reported in issuer's Form 10-K on March 26, 2026 (as of March 20, 2026)
Key Terms
Schedule 13G/A, beneficially owned, shared dispositive power
3 terms
Schedule 13G/Aregulatory
"Amendment No. 1 and Schedule 13G/A references the beneficial ownership filing"
A Schedule 13G/A is an amended public filing with the U.S. securities regulator that updates a previous Schedule 13G, disclosing when an individual or group holds a substantial (typically over 5%) stake in a company and is claiming a passive, non‑controlling intent. Investors monitor these updates because rising or falling holdings can signal changing confidence, potential future moves, or shifts in voting power — like watching a public ledger where large shareholders quietly adjust their positions.
beneficially ownedfinancial
"Amount beneficially owned: Row 9 of each Reporting Person's cover page"
Beneficially owned describes securities or assets where a person has the economic rights and control—such as the right to receive dividends and to direct voting—even if legal title is held in another name. Think of it like having the keys and using a car that’s registered to someone else: you get the benefits and make decisions. Investors care because beneficial ownership reveals who truly controls value and voting power, affecting corporate decisions and takeover dynamics.
shared dispositive powerregulatory
"Shared Dispositive Power 2,724,868.00 listed on the cover page"
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SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549
SCHEDULE 13G
UNDER THE SECURITIES EXCHANGE ACT OF 1934
(Amendment No. 1)
Upstream Bio, Inc.
(Name of Issuer)
Common Stock, par value $0.001 per share
(Title of Class of Securities)
91678A107
(CUSIP Number)
03/31/2026
(Date of Event Which Requires Filing of this Statement)
Check the appropriate box to designate the rule pursuant to which this Schedule is filed:
Rule 13d-1(b)
Rule 13d-1(c)
Rule 13d-1(d)
schemaVersion:
SCHEDULE 13G
CUSIP Number(s):
91678A107
1
Names of Reporting Persons
Decheng Capital Global Life Sciences Fund IV, L.P.
2
Check the appropriate box if a member of a Group (see instructions)
(a)
(b)
3
Sec Use Only
4
Citizenship or Place of Organization
CAYMAN ISLANDS
Number of Shares Beneficially Owned by Each Reporting Person With:
5
Sole Voting Power
0.00
6
Shared Voting Power
2,724,868.00
7
Sole Dispositive Power
0.00
8
Shared Dispositive Power
2,724,868.00
9
Aggregate Amount Beneficially Owned by Each Reporting Person
2,724,868.00
10
Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)
11
Percent of class represented by amount in row (9)
5.0 %
12
Type of Reporting Person (See Instructions)
PN
SCHEDULE 13G
CUSIP Number(s):
91678A107
1
Names of Reporting Persons
Decheng Capital Management IV (Cayman), LLC
2
Check the appropriate box if a member of a Group (see instructions)
(a)
(b)
3
Sec Use Only
4
Citizenship or Place of Organization
CAYMAN ISLANDS
Number of Shares Beneficially Owned by Each Reporting Person With:
5
Sole Voting Power
0.00
6
Shared Voting Power
2,724,868.00
7
Sole Dispositive Power
0.00
8
Shared Dispositive Power
2,724,868.00
9
Aggregate Amount Beneficially Owned by Each Reporting Person
2,724,868.00
10
Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)
11
Percent of class represented by amount in row (9)
5.0 %
12
Type of Reporting Person (See Instructions)
OO
SCHEDULE 13G
CUSIP Number(s):
91678A107
1
Names of Reporting Persons
Decheng Capital Global Healthcare Fund (Master), LP
2
Check the appropriate box if a member of a Group (see instructions)
(a)
(b)
3
Sec Use Only
4
Citizenship or Place of Organization
CAYMAN ISLANDS
Number of Shares Beneficially Owned by Each Reporting Person With:
5
Sole Voting Power
0.00
6
Shared Voting Power
0.00
7
Sole Dispositive Power
0.00
8
Shared Dispositive Power
0.00
9
Aggregate Amount Beneficially Owned by Each Reporting Person
0.00
10
Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)
11
Percent of class represented by amount in row (9)
0.0 %
12
Type of Reporting Person (See Instructions)
PN
SCHEDULE 13G
CUSIP Number(s):
91678A107
1
Names of Reporting Persons
Decheng Capital Global Healthcare GP, LLC
2
Check the appropriate box if a member of a Group (see instructions)
(a)
(b)
3
Sec Use Only
4
Citizenship or Place of Organization
CAYMAN ISLANDS
Number of Shares Beneficially Owned by Each Reporting Person With:
5
Sole Voting Power
0.00
6
Shared Voting Power
0.00
7
Sole Dispositive Power
0.00
8
Shared Dispositive Power
0.00
9
Aggregate Amount Beneficially Owned by Each Reporting Person
0.00
10
Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)
11
Percent of class represented by amount in row (9)
0.0 %
12
Type of Reporting Person (See Instructions)
OO
SCHEDULE 13G
CUSIP Number(s):
91678A107
1
Names of Reporting Persons
Xiangmin Cui
2
Check the appropriate box if a member of a Group (see instructions)
(a)
(b)
3
Sec Use Only
4
Citizenship or Place of Organization
UNITED STATES
Number of Shares Beneficially Owned by Each Reporting Person With:
5
Sole Voting Power
0.00
6
Shared Voting Power
2,724,868.00
7
Sole Dispositive Power
0.00
8
Shared Dispositive Power
2,724,868.00
9
Aggregate Amount Beneficially Owned by Each Reporting Person
2,724,868.00
10
Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)
11
Percent of class represented by amount in row (9)
5.0 %
12
Type of Reporting Person (See Instructions)
IN
SCHEDULE 13G
Item 1.
(a)
Name of issuer:
Upstream Bio, Inc.
(b)
Address of issuer's principal executive offices:
890 Winter Street, Suite 200, Waltham, MA, 02451.
Item 2.
(a)
Name of person filing:
The names of the persons filing this report (collectively, the "Reporting Persons") are:
Decheng Capital Global Life Sciences Fund IV, L.P. ("Fund IV")
Decheng Capital Management IV (Cayman), LLC ("GP IV")
Decheng Capital Global Healthcare Fund (Master), LP ("Healthcare")
Decheng Capital Global Healthcare GP, LLC ("Healthcare GP")
Xiangmin Cui ("Dr. Cui")
The Reporting Persons expressly disclaim status as a "group" for purposes of this Schedule 13G.
(b)
Address or principal business office or, if none, residence:
3000 Sand Hill Road, Building 2, Suite 110
Menlo Park, CA 94025
(c)
Citizenship:
Fund IV Cayman Islands
GP IV Cayman Islands
Healthcare Cayman Islands
Healthcare GP Cayman Islands
Dr. Cui United States
(d)
Title of class of securities:
Common Stock, par value $0.001 per share
(e)
CUSIP No.:
91678A107
Item 3.
If this statement is filed pursuant to §§ 240.13d-1(b) or 240.13d-2(b) or (c), check whether the person filing is a:
(a)
Broker or dealer registered under section 15 of the Act (15 U.S.C. 78o);
(b)
Bank as defined in section 3(a)(6) of the Act (15 U.S.C. 78c);
(c)
Insurance company as defined in section 3(a)(19) of the Act (15 U.S.C. 78c);
(d)
Investment company registered under section 8 of the Investment Company Act of 1940 (15 U.S.C. 80a-8);
(e)
An investment adviser in accordance with § 240.13d-1(b)(1)(ii)(E);
(f)
An employee benefit plan or endowment fund in accordance with § 240.13d-1(b)(1)(ii)(F);
(g)
A parent holding company or control person in accordance with § 240.13d-1(b)(1)(ii)(G);
(h)
A savings associations as defined in Section 3(b) of the Federal Deposit Insurance Act (12 U.S.C. 1813);
(i)
A church plan that is excluded from the definition of an investment company under section 3(c)(14) of the Investment Company Act of 1940 (15 U.S.C. 80a-3);
(j)
A non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J). If filing as a non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J),
please specify the type of institution:
(k)
Group, in accordance with Rule 240.13d-1(b)(1)(ii)(K).
Item 4.
Ownership
(a)
Amount beneficially owned:
Row 9 of each Reporting Person's cover page to this Schedule 13G sets forth the aggregate number of securities of the Issuer beneficially owned by such Reporting Person as of March 31, 2026 and is incorporated by reference.
The Reporting Persons' ownership of the Issuer's securities consists of 2,724,868 shares of common stock held directly by Fund IV. GP IV is the general partner of Fund IV and shares voting and investment authority over the shares held by Fund IV. Dr. Cui is the manager of GP IV. Dr. Cui shares voting and investment authority over the shares held by Fund IV.
(b)
Percent of class:
Row 11 of each Reporting Person's cover page to this Schedule 13G sets forth the percentages of the securities of the Issuer beneficially owned by such Reporting Person as of March 31, 2026 and is incorporated by reference. The percentage set forth in each row 11 is based upon 54,419,986 shares of the Issuer's common stock outstanding as of March 20, 2026, as reported in the Issuer's Annual Report on Form 10-K filed with the Securities and Exchange Commission (the "SEC") on March 26, 2026.
(c)
Number of shares as to which the person has:
(i) Sole power to vote or to direct the vote:
Row 5 of each Reporting Person's cover page to this Schedule 13G sets forth the sole power to vote or to direct the vote of securities of the Issuer beneficially owned by such Reporting Person as of March 31, 2026 and is incorporated by reference.
(ii) Shared power to vote or to direct the vote:
Row 6 of each Reporting Person's cover page to this Schedule 13G sets forth the shared power to vote or to direct the vote of securities of the Issuer beneficially owned by such Reporting Person as of March 31, 2026 and is incorporated by reference.
(iii) Sole power to dispose or to direct the disposition of:
Row 7 of each Reporting Person's cover page to this Schedule 13G sets forth the sole power to dispose or to direct the disposition of securities of the Issuer beneficially owned by such Reporting Person as of March 31, 2026 and is incorporated by reference.
(iv) Shared power to dispose or to direct the disposition of:
Row 8 of each Reporting Person's cover page to this Schedule 13G sets forth the shared power to dispose or to direct the disposition of securities of the Issuer beneficially owned by such Reporting Person as of March 31, 2026 and is incorporated by reference.
Item 5.
Ownership of 5 Percent or Less of a Class.
Not Applicable
Item 6.
Ownership of more than 5 Percent on Behalf of Another Person.
Not Applicable
Item 7.
Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on by the Parent Holding Company or Control Person.
Not Applicable
Item 8.
Identification and Classification of Members of the Group.
Not Applicable
Item 9.
Notice of Dissolution of Group.
Not Applicable
Item 10.
Certifications:
Not Applicable
SIGNATURE
After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.
Decheng Capital Global Life Sciences Fund IV, L.P.
Signature:
/s/ Xiangmin Cui
Name/Title:
By Decheng Capital Management IV (Cayman), LLC, its General Partner, By Xiangmin Cui, Manager
Date:
05/15/2026
Decheng Capital Management IV (Cayman), LLC
Signature:
/s/ Xiangmin Cui
Name/Title:
By Xiangmin Cui, Manager
Date:
05/15/2026
Decheng Capital Global Healthcare Fund (Master), LP
Signature:
/s/ Xiangmin Cui
Name/Title:
By Decheng Capital Global Healthcare GP, LLC, its General Partner, By Decheng Capital LLC, its Manager, By Xiangmin Cui, Manager
Date:
05/15/2026
Decheng Capital Global Healthcare GP, LLC
Signature:
/s/ Xiangmin Cui
Name/Title:
By Decheng Capital LLC, its Manager, By Xiangmin Cui, Manager
Date:
05/15/2026
Xiangmin Cui
Signature:
/s/ Xiangmin Cui
Name/Title:
Xiangmin Cui
Date:
05/15/2026
Exhibit Information
Exhibit 99.1 Joint Filing Agreement (incorporated by reference to Exhibit 99.1 to the Reporting Persons' Schedule 13G filed with the SEC on February 14, 2025).
The filing discloses 2,724,868 shares held by Decheng's Fund IV, representing 5.0% of UPB's common stock using 54,419,986 shares outstanding as of March 20, 2026. Ownership is reported as of March 31, 2026.
Who holds voting and investment authority over the UPB shares?
Decheng Capital Management IV (GP) is the general partner of Fund IV and shares voting and investment authority; Dr. Xiangmin Cui is manager of GP IV and shares that authority per the amendment.
Does the amendment say Decheng is a 'group' under SEC rules?
No. The Reporting Persons explicitly disclaim status as a 'group' in the filing while describing shared authority among affiliated entities and Dr. Cui.
What dates anchor the ownership and outstanding-share figures in the filing?
Beneficial ownership is stated as of March 31, 2026. The percentage uses 54,419,986 shares outstanding reported as of March 20, 2026 in the issuer's 10-K filed March 26, 2026.
