Leon Moulder boosts Zenas BioPharma (ZBIO) stake to 4.794% ownership

Rhea-AI Filing Summary

Leon O. Moulder, Jr. and related entities report updated ownership in Zenas BioPharma, Inc. following recent share purchases. They now beneficially own 3,029,921 shares of common stock, representing 4.794% of the class, including shares held directly, through options, and via Tellus BioVentures, LLC and a revocable trust.

On February 2, 2026, Mr. Moulder purchased 57,000 shares in open-market transactions at prices between $17.69 and $18.14 per share. Between March 30 and March 31, 2026, Tellus purchased 54,000 shares in open-market transactions at prices between $18.195 and $19.58 per share.

Key Figures

Total beneficial ownership: 3,029,921 shares Ownership percentage: 4.794% Direct and option-based holdings: 1,266,954 shares +5 more

8 metrics

Total beneficial ownership 3,029,921 shares Beneficially owned by Leon O. Moulder Jr. and related entities

Ownership percentage 4.794% Percent of Zenas BioPharma common stock class

Direct and option-based holdings 1,266,954 shares Sole voting and dispositive power for Mr. Moulder

Tellus BioVentures holdings 1,726,039 shares Common stock held of record by Tellus BioVentures, LLC

Trust holdings 36,928 shares Common stock held by Leon O. Moulder Jr. Revocable Trust

Moulder open-market purchase 57,000 shares at $17.69–$18.14 Bought on February 2, 2026

Tellus open-market purchase 54,000 shares at $18.195–$19.58 Bought between March 30–31, 2026

Exercisable options 843,799 shares Stock options exercisable within 60 days of March 31, 2026

Key Terms

beneficially owned, open-market transactions, stock options, Schedule 13D, +1 more

5 terms

beneficially owned financial

"11Aggregate amount beneficially owned by each reporting person 3,029,921.00"

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.

open-market transactions financial

"purchased 57,000 shares of Common Stock in multiple open-market transactions at prices per share"

Open-market transactions are purchases or sales of a company’s securities that take place on public exchanges rather than through private agreements. They matter to investors because these trades change the number of shares available, can move the stock price, and often signal management’s view of the company’s value—like a store restocking or clearing shelves, altering supply and the price shoppers see.

stock options financial

"843,799 shares of common stock underlying outstanding stock options exercisable within 60 days"

Stock options are agreements that give a person the right to buy or sell a company's stock at a specific price within a certain time frame. They are often used as a reward or incentive, similar to a coupon that can be used later if the stock price rises, allowing the holder to make a profit.

Schedule 13D regulatory

"This Amendment No. 1 (this "Amendment") amends and supplements the initially filed"

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.

dispositive power financial

"Sole Dispositive Power 1,266,954.00 10 | Shared Dispositive Power 1,762,967.00"

Dispositive power is the authority to decide the final outcome of an asset, legal claim, contract, or corporate action — in effect the power to dispose of or resolve something. For investors it matters because whoever holds that authority can determine who gets paid, who controls an asset or vote, and how risks and returns are allocated; think of it like holding the key that lets you lock in the winner or loser in a deal.

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SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13D

Under the Securities Exchange Act of 1934

(Amendment No. 1)

Zenas BioPharma, Inc.

(Name of Issuer)

Common Stock, $0.0001 par value per share

(Title of Class of Securities)

98937L105

(CUSIP Number)

Leon O. Moulder, Jr.
c/o Zenas BioPharma, Inc., 852 Winter Street, Suite 250
Waltham, MA, 02451
857-271-2954

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

03/31/2026

(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

Leon O. Moulder, Jr.

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 1,266,954.00
8	Shared Voting Power 1,762,967.00
9	Sole Dispositive Power 1,266,954.00
10	Shared Dispositive Power 1,762,967.00

11

Aggregate amount beneficially owned by each reporting person

3,029,921.00

12

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

13

Percent of class represented by amount in Row (11)

4.794 %

14

Type of Reporting Person (See Instructions)

IN

Comment for Type of Reporting Person:

(1) Rows 7 & 9: Consists of (i) 423,155 shares of common stock held directly by Mr. Moulder, and (ii) 843,799 shares of common stock underlying outstanding stock options exercisable within 60 days of the date of March 31, 2026. (2) Rows 8 & 10: Consists of (i) 1,726,039 shares of common stock held by Tellus BioVentures, LLC ("Tellus") and (ii) 36,928 shares of common stock held by Leon O. Moulder, Jr. Revocable Trust U/A dtd 9/9/2008 (the "Trust"). Mr. Moulder is the Managing Member of Tellus and may be deemed to have sole voting and dispositive power over the shares held by Tellus, and Mr. Moulder is a trustee of the Trust and may be deemed to have sole voting and dispositive power of the shares held by the Trust. (3) Row 11: Consists of (i) 423,155 shares of common stock held directly by Mr. Moulder, (ii) 843,799 shares of common stock underlying outstanding stock options exercisable within 60 days of March 31, 2026, (iii) 1,726,039 shares of common stock held by Tellus and (iv) 36,928 shares of common stock held by the Trust. Mr. Moulder is the Managing Member of Tellus and may be deemed to have sole voting and dispositive power over the shares held by Tellus, and Mr. Moulder is a trustee of the Trust and may be deemed to have sole voting and dispositive power of the shares held by the Trust. (4) Row 13: Calculated based on 57,361,260 shares of Common Stock outstanding, as reported by the Issuer in its Annual Report on Form 10-K for the year ended December 31, 2025, as filed with the Securities and Exchange Commission (the "Commission") on March 16, 2026 (the "2025 10-K"), plus (i) 5,000,000 shares of common stock issued by the Issuer in a registered public offering on March 31, 2026 (the "Equity Offering Shares"), as reported by the Issuer in its Current Report on Form 8-K filed with the Commission on March 31, 2026 and (ii) the 843,799 shares of common stock issuable upon the exercise of the options held by Mr. Moulder that are exercisable within 60 days of March 31, 2026.

SCHEDULE 13D

CUSIP Number(s): 98937L105

1

Name of reporting person

Tellus BioVentures, 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)

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 1,726,039.00
9	Sole Dispositive Power 0.00
10	Shared Dispositive Power 1,726,039.00

11

Aggregate amount beneficially owned by each reporting person

1,726,039.00

12

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

13

Percent of class represented by amount in Row (11)

2.77 %

14

Type of Reporting Person (See Instructions)

OO

Comment for Type of Reporting Person:

(1) Rows 8, 10 & 11: Consists of 1,726,039 shares of common stock held of record by Tellus. Mr. Moulder is the Managing Member of Tellus and may be deemed to have sole voting and dispositive power over the shares held by Tellus. (2) Row 13: Calculated based on 57,361,260 shares of Common Stock outstanding, as reported by the Issuer in the 2025 10-K, plus the Equity Offering Shares.

SCHEDULE 13D

CUSIP Number(s): 98937L105

1

Name of reporting person

Leon O. Moulder, Jr. Revocable Trust U/A dtd 9/9/2008

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

FLORIDA

Number of Shares Beneficially Owned by Each Reporting Person With:

7	Sole Voting Power 0.00
8	Shared Voting Power 36,928.00
9	Sole Dispositive Power 0.00
10	Shared Dispositive Power 36,928.00

11

Aggregate amount beneficially owned by each reporting person

36,928.00

12

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

13

Percent of class represented by amount in Row (11)

0.06 %

14

Type of Reporting Person (See Instructions)

OO

Comment for Type of Reporting Person:

(1) Rows 8, 10 & 11: Consists of 36,928 shares of common stock held of record by Leon O. Moulder, Jr. Revocable Trust U/A dtd 9/9/2008 (the "Trust"). Mr. Moulder is a Trustee of the Trust and may be deemed to have sole voting and dispositive power over the shares held by the Trust. (2) Row 13: Calculated based on 57,361,260 shares of Common Stock outstanding, as reported by the Issuer in the 2025 10-K, plus the Equity Offering Shares.

SCHEDULE 13D

Item 1.	Security and Issuer
(a)	Title of Class of Securities: Common Stock, $0.0001 par value 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. 1 (this "Amendment") amends and supplements the Schedule 13D initially filed by Mr. Moulder, Tellus and the Trust on January 14, 2026 (the "Original Schedule 13D"). Only those items that are hereby reported are amended; all other items reported in the Original Schedule 13D remain unchanged. Information given in response to each item shall be deemed incorporated by reference in all other items, as applicable. Capitalized terms not defined in this Amendment have the meanings ascribed to them in the Original Schedule 13D. This Amendment is filed with respect to the Common Stock, par value $0.0001 per share ("Common Stock"), of Zenas BioPharma, Inc., a Delaware corporation (the "Issuer"). The address of the principal executive offices of the Issuer is 852 Winter Street, Suite 250, Waltham, MA 02451.
Item 3.	Source and Amount of Funds or Other Consideration
	Item 3 of the Original Schedule 13D is hereby amended and supplemented by adding the following to the end of Item 3: On February 2, 2026, Mr. Moulder purchased 57,000 shares of Common Stock in multiple open-market transactions at prices per share ranging from $17.69 to $18.14, inclusive. Between March 30, 2026 and March 31, 2026, Tellus purchased 54,000 shares of Common Stock in multiple open-market transactions at prices per share ranging from $18.195 to $19.58, inclusive.
Item 5.	Interest in Securities of the Issuer
(a)	See Items 7-11 of the cover pages of this Statement.
(b)	See Items 7-11 of the cover pages of this Statement.
(c)	Except as reported in this Statement, no Reporting Person has effected any transactions in the Issuer's securities within the past 60 days.
(d)	Not applicable.
(e)	March 31, 2026

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.

Leon O. Moulder, Jr.

Signature:	/s/ Leon O. Moulder, Jr.
Name/Title:	Leon O. Moulder, Jr.
Date:	04/02/2026

Tellus BioVentures, LLC

Signature:	/s / Leon O. Moulder, Jr.
Name/Title:	Leon O. Moulder, Jr., Managing Member
Date:	04/02/2026

Leon O. Moulder, Jr. Revocable Trust U/A dtd 9/9/2008

Signature:	/s / Leon O. Moulder, Jr.
Name/Title:	Leon O. Moulder, Jr., Trustee
Date:	04/02/2026

FAQ

How many Zenas BioPharma (ZBIO) shares does Leon O. Moulder now beneficially own?

Leon O. Moulder, Jr. and affiliated entities report beneficial ownership of 3,029,921 Zenas BioPharma common shares, representing 4.794% of the outstanding class. This total includes directly held shares, exercisable stock options, and shares held by Tellus BioVentures and a revocable trust.

What recent Zenas BioPharma (ZBIO) share purchases did Leon O. Moulder make?

On February 2, 2026, Leon O. Moulder, Jr. bought 57,000 Zenas BioPharma shares in open-market transactions at prices ranging from $17.69 to $18.14 per share, increasing his direct economic exposure to the company’s common stock.

What Zenas BioPharma (ZBIO) purchases were made by Tellus BioVentures, LLC?

Between March 30 and March 31, 2026, Tellus BioVentures, LLC purchased 54,000 Zenas BioPharma shares in open-market transactions at prices from $18.195 to $19.58 per share, contributing to Tellus’s total of 1,726,039 shares held of record.

What percentage of Zenas BioPharma (ZBIO) does Tellus BioVentures, LLC own?

Tellus BioVentures, LLC reports beneficial ownership of 1,726,039 Zenas BioPharma shares, equal to 2.77% of the company’s common stock. This percentage is calculated using outstanding share figures from the 2025 Form 10-K plus additional equity offering shares.

How is the 4.794% ownership in Zenas BioPharma (ZBIO) for Leon O. Moulder calculated?

The 4.794% ownership is based on 57,361,260 shares of common stock outstanding, plus 5,000,000 equity offering shares and 843,799 shares issuable upon exercisable options held by Mr. Moulder, as described in the company’s 2025 Form 10-K and subsequent disclosures.

What role do stock options play in Leon O. Moulder’s Zenas BioPharma (ZBIO) holdings?

Mr. Moulder’s beneficial ownership includes 843,799 shares of Zenas BioPharma common stock underlying outstanding stock options exercisable within 60 days of March 31, 2026. These options significantly increase his potential equity position beyond currently issued and outstanding shares.