SR One's stake in Zenas BioPharma (ZBIO) drops over 1 point without selling

Rhea-AI Filing Summary

An amendment to Schedule 13D reports the current ownership of Zenas BioPharma, Inc. common stock by SR One-affiliated investment vehicles and Simeon George, M.D. Together, the reporting persons beneficially own 5,037,854 shares, representing 7.7% of Zenas’ 65,176,723 outstanding shares as of July 31, 2026. All voting and dispositive authority is reported as shared rather than sole. The change triggering this amendment reflects a decrease of more than 1 percentage point in beneficial ownership percentage due to an increase in Zenas’ shares outstanding, not because of recent share transactions, as no trades in the last 60 days are reported.

Key Figures

Shares beneficially owned (group total): 5,037,854 shares Ownership percentage (group total): 7.7% Shares outstanding: 65,176,723 shares +4 more

7 metrics

Shares beneficially owned (group total) 5,037,854 shares Common stock of Zenas BioPharma, Inc. beneficially owned by the reporting persons

Ownership percentage (group total) 7.7% Percent of Zenas BioPharma common stock beneficially owned by SR One group

Shares outstanding 65,176,723 shares Zenas BioPharma common shares outstanding as of July 31, 2026

SR One Capital Fund II Aggregator holdings 1,946,564 shares Beneficially owned with 3.0% of class

AMZL holdings 1,917,895 shares Beneficially owned with 2.9% of class

SR One Capital Opportunities Fund I holdings 1,173,395 shares Beneficially owned with 1.8% of class

Simeon George beneficial ownership 5,037,854 shares Same 7.7% of class reported through control of SR One Capital Management

Key Terms

beneficial ownership, shared voting power, shared dispositive power, Schedule 13D, +1 more

5 terms

beneficial ownership financial

"This Amendment No. 2 is being filed to report that the beneficial ownership"

Beneficial ownership means the person or entity that actually enjoys the benefits of owning shares or other assets — such as receiving dividends, voting rights, or price gains — even if the legal title is held in another name. For investors it matters because knowing who truly controls and profits from a company reveals who can influence decisions, exposes potential conflicts of interest or hidden concentration of power, and affects transparency and risk in the stock.

shared voting power financial

"Number of Shares Beneficially Owned... Shared Voting Power 5,037,854.00"

Shared voting power occurs when two or more parties jointly have the right to vote or decide how a block of company shares is cast, like co-owners who must agree before moving a piece of furniture. Investors care because who controls voting rights affects board elections, major corporate decisions and takeover outcomes, and shared control can alter regulatory disclosures and the practical influence any holder has over a company’s direction and value.

shared dispositive power financial

"Number of Shares Beneficially Owned... Shared Dispositive Power 5,037,854.00"

Schedule 13D regulatory

"This Amendment No. 2 to amends and supplements the statement on"

A Schedule 13D is a legal document that investors file with regulators when they buy a large enough stake in a company to potentially influence its management or decisions. It provides details about the investor’s intention, ownership stake, and plans, helping other investors understand who is gaining control and what their motives might be.

attorney-in-fact regulatory

"Signature: /s/ Sasha Keough, as attorney-in-fact for Simeon George, M.D."

An attorney-in-fact is the person or entity given legal authority through a power of attorney to act on behalf of another for specific tasks, such as signing documents, voting shares, or handling transactions. For investors, this matters because it lets a trusted representative make timely decisions or complete paperwork when the owner cannot, much like handing keys to someone to run errands on your behalf—so checks on scope and limits of that authority are important.

FAQ

What percentage of ZBIO does SR One currently report owning in this Schedule 13D/A?

SR One-affiliated entities and Simeon George, M.D. report beneficial ownership of 7.7% of Zenas BioPharma (ZBIO). This corresponds to 5,037,854 common shares, based on 65,176,723 shares outstanding as of July 31, 2026.

How many Zenas BioPharma (ZBIO) shares are beneficially owned by the SR One reporting group?

The reporting group beneficially owns 5,037,854 Zenas BioPharma common shares. This ownership is reported as entirely subject to shared voting and shared dispositive power among the SR One entities and Simeon George, M.D.

Why was this Schedule 13D amendment filed for Zenas BioPharma (ZBIO)?

The amendment states that the reporting persons’ beneficial ownership percentage decreased by more than 1% due to an increase in Zenas’ shares outstanding. The change reflects dilution from a larger share count, not new trades.

What is the total number of Zenas BioPharma (ZBIO) shares outstanding used in this ownership calculation?

The ownership percentages are calculated using 65,176,723 Zenas BioPharma common shares outstanding. This figure comes from Zenas’ Form 10-Q, which reported that share count as of July 31, 2026.

Have the SR One reporting persons traded Zenas BioPharma (ZBIO) stock recently?

The amendment states that no reporting person has effected any transaction in Zenas BioPharma common stock during the last 60 days. The percentage change arises from a higher total share count, not recent buying or selling.

Which SR One funds are included in the ZBIO Schedule 13D/A reporting group?

The group includes SR One Capital Fund II Aggregator, LP, AMZL, LP, and SR One Capital Opportunities Fund I, LP, along with their general partners, SR One Capital Management, LLC, and Simeon George, M.D. as controlling person.

AI-generated analysis. How Rhea-AI works. Not financial advice.

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Available on EDGAR 08/17/2026 - 07:00 PM Accepted by SEC EDGAR 08/17/2026 - 06:59 PM Learn about SEC filing dates

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13D

Under the Securities Exchange Act of 1934

(Amendment No. 2)

Zenas BioPharma, Inc.

(Name of Issuer)

Common stock, par value $0.0001 per share

(Title of Class of Securities)

98937L105

(CUSIP Number)

Sasha Keough
c/o SR One Capital Management, LP, 929 Main Street, Suite 200
Redwood City, CA, 94063
(410) 800-7503

(Name, Address and Telephone Number of Person Authorized to Receive Notices and Communications)

08/13/2026

(Date of Event Which Requires Filing of This Statement)

If the filing person has previously filed a statement on Schedule 13G to report the acquisition that is the subject of this Schedule 13D, and is filing this schedule because of §§ 240.13d-1(e), 240.13d-1(f) or 240.13d-1(g), check the following box.

The information required on the remainder of this cover page shall not be deemed to be "filed" for the purpose of Section 18 of the Securities Exchange Act of 1934 ("Act") or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act (however, see the Notes).

schemaVersion:

SCHEDULE 13D

CUSIP Number(s): 98937L105

1

Name of reporting person

SR One Capital Management, LLC

2

Check the appropriate box if a member of a Group (See Instructions)

(a)
(b)

3

SEC use only

4

Source of funds (See Instructions)

AF

5

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

6

Citizenship or place of organization

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 0.00
8	Shared Voting Power 5,037,854.00
9	Sole Dispositive Power 0.00
10	Shared Dispositive Power 5,037,854.00

11

Aggregate amount beneficially owned by each reporting person

5,037,854.00

12

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

13

Percent of class represented by amount in Row (11)

7.7 %

14

Type of Reporting Person (See Instructions)

OO

SCHEDULE 13D

CUSIP Number(s): 98937L105

1

Name of reporting person

SR One Capital Fund II Aggregator, LP

2

Check the appropriate box if a member of a Group (See Instructions)

(a)
(b)

3

SEC use only

4

Source of funds (See Instructions)

WC

5

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

6

Citizenship or place of organization

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 0.00
8	Shared Voting Power 1,946,564.00
9	Sole Dispositive Power 0.00
10	Shared Dispositive Power 1,946,564.00

11

Aggregate amount beneficially owned by each reporting person

1,946,564.00

12

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

13

Percent of class represented by amount in Row (11)

3.0 %

14

Type of Reporting Person (See Instructions)

PN

SCHEDULE 13D

CUSIP Number(s): 98937L105

1

Name of reporting person

SR One Capital Partners II, LP

2

Check the appropriate box if a member of a Group (See Instructions)

(a)
(b)

3

SEC use only

4

Source of funds (See Instructions)

AF

5

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

6

Citizenship or place of organization

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 0.00
8	Shared Voting Power 1,946,564.00
9	Sole Dispositive Power 0.00
10	Shared Dispositive Power 1,946,564.00

11

Aggregate amount beneficially owned by each reporting person

1,946,564.00

12

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

13

Percent of class represented by amount in Row (11)

3.0 %

14

Type of Reporting Person (See Instructions)

PN

SCHEDULE 13D

CUSIP Number(s): 98937L105

1

Name of reporting person

AMZL, LP

2

Check the appropriate box if a member of a Group (See Instructions)

(a)
(b)

3

SEC use only

4

Source of funds (See Instructions)

WC

5

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

6

Citizenship or place of organization

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 0.00
8	Shared Voting Power 1,917,895.00
9	Sole Dispositive Power 0.00
10	Shared Dispositive Power 1,917,895.00

11

Aggregate amount beneficially owned by each reporting person

1,917,895.00

12

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

13

Percent of class represented by amount in Row (11)

2.9 %

14

Type of Reporting Person (See Instructions)

PN

SCHEDULE 13D

CUSIP Number(s): 98937L105

1

Name of reporting person

SR One Capital SMA Partners, LP

2

Check the appropriate box if a member of a Group (See Instructions)

(a)
(b)

3

SEC use only

4

Source of funds (See Instructions)

AF

5

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

6

Citizenship or place of organization

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 0.00
8	Shared Voting Power 1,917,895.00
9	Sole Dispositive Power 0.00
10	Shared Dispositive Power 1,917,895.00

11

Aggregate amount beneficially owned by each reporting person

1,917,895.00

12

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

13

Percent of class represented by amount in Row (11)

2.9 %

14

Type of Reporting Person (See Instructions)

PN

SCHEDULE 13D

CUSIP Number(s): 98937L105

1

Name of reporting person

SR One Capital Opportunities Fund I, LP

2

Check the appropriate box if a member of a Group (See Instructions)

(a)
(b)

3

SEC use only

4

Source of funds (See Instructions)

WC

5

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

6

Citizenship or place of organization

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 0.00
8	Shared Voting Power 1,173,395.00
9	Sole Dispositive Power 0.00
10	Shared Dispositive Power 1,173,395.00

11

Aggregate amount beneficially owned by each reporting person

1,173,395.00

12

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

13

Percent of class represented by amount in Row (11)

1.8 %

14

Type of Reporting Person (See Instructions)

PN

SCHEDULE 13D

CUSIP Number(s): 98937L105

1

Name of reporting person

SR One Capital Opportunities Partners I, LP

2

Check the appropriate box if a member of a Group (See Instructions)

(a)
(b)

3

SEC use only

4

Source of funds (See Instructions)

AF

5

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

6

Citizenship or place of organization

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 0.00
8	Shared Voting Power 1,173,395.00
9	Sole Dispositive Power 0.00
10	Shared Dispositive Power 1,173,395.00

11

Aggregate amount beneficially owned by each reporting person

1,173,395.00

12

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

13

Percent of class represented by amount in Row (11)

1.8 %

14

Type of Reporting Person (See Instructions)

PN

SCHEDULE 13D

CUSIP Number(s): 98937L105

1

Name of reporting person

Simeon George

2

Check the appropriate box if a member of a Group (See Instructions)

(a)
(b)

3

SEC use only

4

Source of funds (See Instructions)

AF

5

Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)

6

Citizenship or place of organization

UNITED STATES

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 0.00
8	Shared Voting Power 5,037,854.00
9	Sole Dispositive Power 0.00
10	Shared Dispositive Power 5,037,854.00

11

Aggregate amount beneficially owned by each reporting person

5,037,854.00

12

Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)

13

Percent of class represented by amount in Row (11)

7.7 %

14

Type of Reporting Person (See Instructions)

IN

SCHEDULE 13D

Item 1.	Security and Issuer
(a)	Title of Class of Securities: Common stock, par value $0.0001 per share
(b)	Name of Issuer: Zenas BioPharma, Inc.
(c)	Address of Issuer's Principal Executive Offices: 852 Winter Street, Suite 250, Waltham, MASSACHUSETTS , 02451.
Item 1 Comment: This Amendment No. 2 ("Amendment No. 2") to Schedule 13D amends and supplements the statement on Schedule 13D originally filed on September 23, 2024 (the "Schedule 13D") and Amendment No. 1 thereto filed on October 14, 2025 ("Amendment No. 1") relating to the Common Stock of the Issuer. Certain terms used but not defined in this Amendment No. 2 have the meanings assigned thereto in the Schedule 13D (and Amendment No. 1 thereto). Except as specifically provided herein, this Amendment No. 2 does not modify any of the information previously reported on the Schedule 13D (and Amendment No. 1 thereto). This Amendment No. 2 is being filed to report that the beneficial ownership of Common Stock by the Reporting Persons (as defined below) has decreased by more than 1% as a result of an increase in the number of Common Stock outstanding.
Item 2.	Identity and Background
(a)	SR One Capital Management, LLC ("SR One Capital Management"); SR One Capital Fund II Aggregator, LP ("SR One Fund II Aggregator"); SR One Capital Partners II, LP ("SR One Partners II"); AMZL, LP ("AMZL"); SR One Capital SMA Partners, LP ("SMA Partners"); SR One Capital Opportunities Fund I, LP ("SR One Opportunities Fund I"); SR One Capital Opportunities Partners I, LP ("SR One Opportunities Partners I"); and Simeon George, M.D. ("Dr. George"). SR One Fund II Aggregator is directly controlled by its general partner, SR One Partners II. AMZL is directly controlled by its general partner, SMA Partners. SR One Opportunities Fund I is directly controlled by its general partner, SR One Opportunities Partners I. SR One Partners II, SMA Partners and SR One Opportunities Partners I are directly controlled by their general partners, SR One Capital Management, and Dr. George controls SR One Capital Management. Accordingly, each of SR One Capital Management and Dr. George may be deemed to have voting and dispositive power with respect to the SR One Fund II Aggregator Shares, the AMZL Shares and the SR One Opportunities Fund I Shares (each as defined below). The persons named in this Item 2 are referred to individually herein as a "Reporting Person" and collectively as the "Reporting Persons." SR One Fund II Aggregator, AMZL and SR One Opportunities Fund I are referred to collectively as the "Funds."
(b)	The address of each Reporting Person for purposes of this filing is c/o SR One Capital Management, LP, 929 Main Street, Suite 200, Redwood City, CA 94063.
(c)	The principal business of the Funds is to invest in and assist growth-oriented businesses. The principal business of SR One Partners II is to act as the sole general partner of SR One Fund II Aggregator. The principal business of SMA Partners is to act as the sole general partner of AMZL. The principal business of SR One Opportunities Partners I is to act as the sole general partner of SR One Opportunities Fund I. The principal business of SR One Capital Management is to act as the sole general partner of SR One Partners II, SMA Partners, SR One Opportunities Partners I and a number of affiliated partnerships with similar businesses. The principal business of Dr. George is to manage SR One Capital Management.
(d)	During the five years prior to the date hereof, none of the Reporting Persons has been convicted in a criminal proceeding or has been a party to a civil proceeding ending in a judgment, decree or final order enjoining future violations of, or prohibiting activities subject to, federal or state securities laws or finding any violation with respect to such laws.
(e)	During the five years prior to the date hereof, none of the Reporting Persons has been convicted in a criminal proceeding or has been a party to a civil proceeding ending in a judgment, decree or final order enjoining future violations of, or prohibiting activities subject to, federal or state securities laws or finding any violation with respect to such laws.
(f)	SR One Fund II Aggregator, SR One Partners II, AMZL, SMA Partners, SR One Opportunities Fund I, and SR One Opportunities Partners I are limited partnerships organized under the laws of the State of Delaware. SR One Capital Management is a limited liability company organized under the laws of the State of Delaware. Dr. George is a United States citizen.
Item 3.	Source and Amount of Funds or Other Consideration
	Not applicable.
Item 4.	Purpose of Transaction
	Not applicable.
Item 5.	Interest in Securities of the Issuer
(a)	The percentage of outstanding shares of Common Stock which may be deemed to be beneficially owned by each Reporting Person is set forth on Line 13 of such Reporting Person's cover sheet. Such percentage was calculated based on 65,176,723 shares of Common Stock reported by the Issuer to be outstanding as of July 31, 2026, on the Issuer's Form 10-Q filed with the Securities Exchange Commission on August 13, 2026.
(b)	Regarding the number of shares as to which such person has: (i) sole power to vote or to direct the vote: See line 7 of cover sheets (ii) shared power to vote or to direct the vote: See line 8 of cover sheets (iii) sole power to dispose or to direct the disposition: See line 9 of cover sheets (iv) shared power to dispose or to direct the disposition: See line 10 of cover sheets
(c)	None of the Reporting Persons has effected any transaction in shares of Common Stock during the last 60 days.
(d)	No other person is known to have the right to receive or the power to direct the receipt of dividends from, or any proceeds from the sale of, Common Stock beneficially owned by any of the Reporting Persons.
(e)	Not applicable.
Item 6.	Contracts, Arrangements, Understandings or Relationships With Respect to Securities of the Issuer
	Not applicable.
Item 7.	Material to be Filed as Exhibits.
	Exhibit 1 - Agreement regarding filing of joint Schedule 13D. Exhibit 2 - Power of Attorney regarding filings under the Securities Exchange Act of 1934, as amended.

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.

SR One Capital Management, LLC

Signature:	/s/ Sasha Keough
Name/Title:	Sasha Keough, as attorney-in-fact for Simeon George, M.D., Managing Member
Date:	08/17/2026

SR One Capital Fund II Aggregator, LP

Signature:	/s/ Sasha Keough
Name/Title:	Sasha Keough, as attorney-in-fact for Simeon George, M.D., Managing Member
Date:	08/17/2026

SR One Capital Partners II, LP

Signature:	/s/ Sasha Keough
Name/Title:	Sasha Keough, as attorney-in-fact for Simeon George, M.D., Managing Member
Date:	08/17/2026

AMZL, LP

Signature:	/s/ Sasha Keough
Name/Title:	Sasha Keough, as attorney-in-fact for Simeon George, M.D., Managing Member
Date:	08/17/2026

SR One Capital SMA Partners, LP

Signature:	/s/ Sasha Keough
Name/Title:	Sasha Keough, as attorney-in-fact for Simeon George, M.D., Managing Member
Date:	08/17/2026

SR One Capital Opportunities Fund I, LP

Signature:	/s/ Sasha Keough
Name/Title:	Sasha Keough, as attorney-in-fact for Simeon George, M.D., Managing Member
Date:	08/17/2026

SR One Capital Opportunities Partners I, LP

Signature:	/s/ Sasha Keough
Name/Title:	Sasha Keough, as attorney-in-fact for Simeon George, M.D., Managing Member
Date:	08/17/2026

Simeon George

Signature:	/s/ Sasha Keough
Name/Title:	Sasha Keough, as attorney-in-fact for Simeon George, M.D.
Date:	08/17/2026

Comments accompanying signature:

This Amendment No. 2 to Schedule 13D was executed by Sasha Keough on behalf of the individuals listed above pursuant to a Power of Attorney, a copy of which is attached as Exhibit 2.