[SCHEDULE 13D/A] Zenas BioPharma, Inc. SEC Filing

Rhea-AI Filing Summary

Amendment discloses additional purchases and updated holdings by Leon O. Moulder, Jr., Tellus BioVentures, LLC and a related trust in Zenas BioPharma common stock. Together the reporting persons now beneficially own 2,594,662 shares, representing 4.8% of the company on a post-transaction basis. The aggregate includes 266,155 shares held directly by Mr. Moulder, 619,540 shares issuable under options exercisable within 60 days, 1,672,039 shares held by Tellus, and 36,928 shares held by the Revocable Trust.

On October 7, 2025 Zenas entered into a PIPE purchase agreement selling an aggregate of 6,311,030 PIPE Shares (split: 6,262,112 to institutional investors at $19.00 per share and 48,918 to directors/officers at $20.85 per share). The Trust purchased 36,928 director/officer PIPE Shares for $769,948.80. The PIPE closed on October 9, 2025, and a registration rights agreement requires a resale registration filing within 15 days of the PIPE closing subject to customary delays.

Positive

• Increased disclosed alignment: CEO and affiliated entities hold 2,594,662 shares (4.8%), signalling substantial insider economic exposure
• PIPE closing completed: The Private Placement closed on October 9, 2025, providing committed capital of institutional and director/officer investors
• Registration rights granted: PIPE investors received a registration rights agreement requiring a resale registration filing within 15 days of closing

Negative

• Dilution impact: Ownership percentages are calculated on a post-transaction base that includes 11,311,030 newly issued shares (InnoCare + PIPE), diluting existing holders
• Potential near-term selling pressure: Registered resale of PIPE Shares after the registration becomes effective could increase float and supply
• Concentration through affiliated entities: 1,672,039 shares are held via Tellus, where Mr. Moulder is Managing Member, consolidating control influence

Insights

Securities Structuring Analyst

TL;DR: Reporting persons increased disclosed economic exposure via exercisable options and participation in the PIPE.

The filing shows an aggregate beneficial position of 2,594,662 shares (4.8%) composed of direct holdings, options exercisable within 60 days (619,540) and holdings through Tellus and a Trust. Inclusion of exercisable options means the reported stake counts both current and near-term potential shares when computing percentage ownership.

Key dependencies include the issuer's post-transaction share base (which incorporates the 5,000,000 InnoCare issuance and the 6,311,030 PIPE shares) and the timing of option exercises. Monitor the registration timetable required within 15 days of the PIPE closing for resale liquidity over the near term.

Corporate Finance Counsel

TL;DR: The PIPE includes customary registration and indemnity provisions; the Trust funded a director/officer allotment.

The Securities Purchase Agreement allocated 6,262,112 shares to institutional PIPE investors at $19.00 and 48,918 shares to director/officer investors at $20.85. The Registration Rights Agreement obligates the company to file a resale registration within 15 days of the PIPE closing, subject to allowable delays, and contains reciprocal indemnities.

Material legal milestones to watch are the filing and effectiveness of the PIPE Registration Statement and any permitted delays; these affect when PIPE investors may freely resell shares, with near-term effects on float and potential selling pressure.

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)

10/07/2025

(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).

SCHEDULE 13D

CUSIP No. 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 885,695.00
8	Shared Voting Power 1,708,967.00
9	Sole Dispositive Power 885,695.00
10	Shared Dispositive Power 1,708,967.00

11

Aggregate amount beneficially owned by each reporting person

2,594,662.00

12

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

13

Percent of class represented by amount in Row (11)

4.8 %

14

Type of Reporting Person (See Instructions)

IN

Comment for Type of Reporting Person:

(1) Rows 7 & 9: Consists of (i) 266,155 shares of common stock held directly by Mr. Moulder, and (ii) 619,540 shares of common stock underlying outstanding stock options exercisable within 60 days of the date of October 7, 2025. (2) Rows 8 & 10: Consists of (i) 1,672,039 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) 266,155 shares of common stock held directly by Mr. Moulder, (ii) 619,540 shares of common stock underlying outstanding stock options exercisable within 60 days of October 7, 2025, (iii) 1,672,039 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 42,110,313 shares of Common Stock outstanding, as reported by the Issuer in its Quarterly Report on Form 10-Q for the three months ended June 30, 2025, as filed with the Securities and Exchange Commission (the "Commission") on August 12, 2025 (the "Q2 2025 Form 10-Q"), plus (i) 5,000,000 shares of common stock issued by the Issuer to InnoCare Pharma Inc. on October 7, 2025 (the "InnoCare Shares"), as reported by the Issuer in its Current Report on Form 8-K filed with the Commission on October 8, 2025, (ii) 6,311,030 shares of common stock issued by the Issuer to certain investors pursuant to that certain Securities Purchase Agreement, dated as of October 7, 2025 (the "PIPE Purchase Agreement" and such shares, the "PIPE Shares"), as reported by the issuer in its Registration Statement on Form S-3ASR filed with the Commission on October 8, 2025 (the "Shelf Registration Statement"), and (iii) the 619,540 shares of common stock issuable upon the exercise of the options held by Mr. Moulder that are exercisable within 60 days of October 7, 2025.

SCHEDULE 13D

CUSIP No. 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 1,672,039.00
9	Sole Dispositive Power 0.00
10	Shared Dispositive Power 1,672,039.00

11

Aggregate amount beneficially owned by each reporting person

1,672,039.00

12

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

13

Percent of class represented by amount in Row (11)

3.1 %

14

Type of Reporting Person (See Instructions)

OO

Comment for Type of Reporting Person:

(1) Rows 8, 10 & 11: Consists of 1,672,039 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 42,110,313 shares of Common Stock outstanding, as reported by the Issuer in the Q2 2025 10-Q, plus (i) the InnoCare Shares and (ii) the PIPE Shares.

SCHEDULE 13D

CUSIP No. 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)

0.1 %

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 42,110,313 shares of Common Stock outstanding, as reported by the Issuer in the Q2 2025 10-Q, plus (i) the InnoCare Shares and (ii) the PIPE 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 and Tellus on June 6, 2025 (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 2.	Identity and Background
(a)	This Statement is being filed by Leon O. Moulder, Jr., the Issuer's Chief Executive Officer and Chairman of its Board of Directors, Tellus BioVentures, LLC, a Delaware limited liability company ("Tellus") and Leon O. Moulder, Jr. Revocable Trust U/A dtd 9/9/2008 (the "Trust" and, together with Mr. Moulder and Tellus, the "Reporting Persons"). The agreement among the Reporting Persons to file jointly in accordance with the provisions of Rule 13d-1(k)(1) under the Act is attached hereto as Exhibit 1. Each Reporting Person disclaims beneficial ownership of all securities reported in this Statement except to the extent of such Reporting Person's pecuniary interest therein, other than those securities reported herein as being held directly by such Reporting Person.
(b)	The address of the principal offices of Tellus and the Trust, and the business address of Mr. Moulder, is 10520 Trevi Isle Way, Miromar Lakes, FL 33913.
(c)	Tellus is an early-stage life sciences investment fund involved in in acquiring, holding and disposing of interests in various companies for investment purposes. Mr. Moulder is the Managing Member of Tellus and is the Issuer's Chief Executive Officer and Chairman of its Board of Directors. The Trust is an estate planning vehicle that makes and holds investments for its beneficiary, Mr. Moulder. Mr. Moulder is a trustee of the Trust.
(d)	During the past five years, no Reporting Person has been convicted in a criminal proceeding (excluding traffic violations or similar misdemeanors).
(e)	No Reporting Person is, nor during the last five years has been, a party to a civil proceeding of a judicial or administrative body of competent jurisdiction and as a result of such proceeding was or is subject to a judgment, decree or final order enjoining future violations of, or prohibiting or mandating activities subject to, federal or state securities laws or finding any violation with respect to such laws.
(f)	Tellus is a limited liability company organized under the laws of the State of Delaware. Mr. Moulder is a citizen of the United States of America. The Trust was established in Minnesota and was subsequently amended and is now situated in Florida; however, it has no designated place of organization.
Item 3.	Source and Amount of Funds or Other Consideration
	Item 3 of the Original Schedule 13D is hereby amended and supplement by adding the following to the end of Item 3: On October 7, 2025, the Issuer entered into a Securities Purchase Agreement (the "Securities Purchase Agreement") with (i) certain institutional and accredited investors (the "Institutional Investors") and (ii) certain directors and officers of the Company (the "Director and Officer Investors" and, together with the Institutional Investors, each, a "PIPE Investor" and, together, the "PIPE Investors"), pursuant to which the Company agreed to sell to (i) the Institutional Investors an aggregate of 6,262,112 shares of Common Stock (the "Institutional Investor PIPE Shares"), at a price of $19.00 per share, and (ii) the Director and Officer Investors an aggregate of 48,918 shares of Common Stock (the "Director and Officer Investor PIPE Shares" and, together with the Institutional Investor PIPE Shares, the "PIPE Shares") at a price of $20.85 per share, in each case in a private placement transaction (the "Private Placement"). The Trust purchased 36,928 of the Director and Officer Investor PIPE Shares for a total purchase price of $769,948.80, which was funded by trust assets. The Private Placement closed on October 9, 2025 (the "PIPE Closing"). The above summary of the Purchase Agreement is qualified by reference to such description and the full text of the Form of Purchase Agreement, a form of which is filed as Exhibit 3 to this Amendment and is incorporated by reference herein.
Item 4.	Purpose of Transaction
	The information set forth in Item 3 of this Statement is incorporated herein by reference. Mr. Moulder serves as the Chairman of the Issuer's Board of Directors and as its Chief Executive Officer. In such capacity, Mr. Moulder has influence over the corporate activities of the Issuer, including activities that may relate to items described in subparagraphs (a) through (j) of Item 4 of Schedule 13D. Except as described herein, the Reporting Persons have no present plans or proposals that relate to or would result in any of the transactions described in subparagraphs (a) through (j) of Item 4 of Schedule 13D. However, the Reporting Persons reserve the right to formulate in the future plans or proposals which may relate to or result in the transactions described in subparagraphs (a) through (j) of this Item 4. In addition to the foregoing, the Reporting Persons may engage in discussions from time to time with other members of the Issuer's management and/or Board of Directors and/or with other stockholders of the Issuer and/or other third parties. Such discussions may include, without limitation, discussions with respect to the governance, board composition, management, operations, business, assets, capitalization, financial condition, strategic plans and future of the Issuer, as well as other matters related to the Issuer. These discussions may also include a review of options for enhancing stockholder value through, among other things, various strategic alternatives (including acquisitions and divestitures) or operational or management initiatives. The Reporting Persons hold the securities of the Issuer for general investment purposes. The Reporting Persons may, from time to time, depending on prevailing market, economic and other conditions, acquire additional shares of Common Stock or other securities of the Issuer, dispose of any such securities, or engage in discussions with the Issuer concerning such acquisitions or dispositions or further investments in the Issuer. The Reporting Persons intend to review their investment in the Issuer on a continuing basis and, depending upon the price and availability of shares of Common Stock or other securities of the Issuer, subsequent developments affecting the Issuer, the Issuer's business and prospects, other investment and business opportunities available to the Reporting Persons, general stock market and economic conditions, tax considerations and other factors considered relevant, may decide at any time to increase or to decrease the size of their investment in the Issuer in the open market, in privately negotiated transactions, pursuant to 10b5-1 trading plans or otherwise. Mr. Moulder, in his capacity as Chief Executive Officer of the Issuer, may be entitled to receive cash compensation and equity compensation, including stock option or other equity awards, including pursuant to the Issuer's 2024 Equity Incentive Plan (the "2024 Plan"). Mr. Moulder does not receive any additional compensation for his service on the Board of Directors of the Issuer. The terms and provisions of the 2024 Plan are described in the Issuer's definitive proxy statement relating to its 2025 annual meeting of stockholders, which was filed with the Commission on March 11, 2025 (the "2025 Proxy").
Item 5.	Interest in Securities of the Issuer
(a)	See Items 7-11 of the cover pages of this Statement and Item 2 above.
(b)	See Items 7-11 of the cover pages of this Statement and Item 2 above.
(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)	October 7, 2025
Item 6.	Contracts, Arrangements, Understandings or Relationships With Respect to Securities of the Issuer
	Item 6 of the Original Schedule 13D is hereby amended and supplement by adding the following to the end of Item 6: In connection with the Private Placement, on October 7, 2025, the Issuer entered into a Registration Rights Agreement (the "PIPE Registration Rights Agreement") with the PIPE Investors, pursuant to which the Issuer will prepare and file, within 15 days of the PIPE Closing and subject to certain allowable delays, an initial registration statement (the "PIPE Registration Statement") with the Commission to register for resale the PIPE Shares. The Issuer granted the PIPE Investors customary indemnification rights in connection with the PIPE Registration Rights Agreement. The PIPE Investors have also granted the Issuer customary indemnification rights in connection with the PIPE Registration Rights Agreement. The above summary of the PIPE Registration Rights Agreement is qualified by reference to such description and the full text of the PIPE Registration Rights Agreement, a form of which is filed as Exhibit 4 to this Amendment and is incorporated by reference herein.
Item 7.	Material to be Filed as Exhibits.
	Exhibit 1: Joint Filing Agreement, dated October 9, 2025, by and among the Reporting Persons (filed herewith). Exhibit 2: Fourth Amended and Restated Shareholders Agreement, dated May 3, 2024, by and among the Issuer and certain of its stockholders (filed as Exhibit 4.2 to the Issuer's Registration Statement on Form S-1/A as filed with the Commission on September 6, 2024 (SEC File No. 333-281713)). Exhibit 3: Form of Securities Purchase Agreement, dated October 7, 2025, by and among the Issuer and the investors party thereto (filed as Exhibit 10.3 to the Issuer's Current Report on Form 8-K as filed with the Commission on October 8, 2025 (SEC File No. 001-42270)). Exhibit 4: Form of Registration Rights Agreement, dated October 7, 2025, by and among the Issuer and the investors party thereto (filed as Exhibit 10.4 to the Issuer's Current Report on Form 8-K as filed with the Commission on October 8, 2025 (SEC File No. 001-42270)).

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:	10/09/2025

Tellus BioVentures, LLC

Signature:	/s / Leon O. Moulder, Jr.
Name/Title:	Leon O. Moulder, Jr., Managing Member
Date:	10/09/2025

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:	10/09/2025

FAQ

What stake does Leon O. Moulder (ZBIO) report after this amendment?

The reporting persons beneficially own 2,594,662 shares, representing 4.8% on a post-transaction basis (includes exercisable options).

How many shares and at what prices were sold in the PIPE?

The PIPE comprised 6,262,112 institutional shares at $19.00 per share and 48,918 director/officer shares at $20.85 per share.

Did the Trust participate in the PIPE (ZBIO)?

Yes. The Trust purchased 36,928 director/officer PIPE Shares for a total of $769,948.80, funded by trust assets.

When did the PIPE close and what follows on registration?

The PIPE closed on October 9, 2025. The company agreed to file a resale registration within 15 days of the PIPE closing, subject to customary delays.

Do the reported holdings include options?

Yes. The aggregate includes 619,540 common shares issuable upon exercise of stock options exercisable within 60 days of October 7, 2025.