# EDGAR Filing Document

**Accession Number:** 0002132038
**File Stem:** 0001193125-26-216973
**Filing Date:** 2026-5
**Character Count:** 23814
**Document Hash:** b1916af7d1b918fed9eb8cc851353a18
**Contains OCR:** False
**Source Format:** 

## Filing Content

## Filing Summary
**0001193125-26-216973.hdr.sgml**: 20260511

**ACCESSION NUMBER**: 0001193125-26-216973

**CONFORMED SUBMISSION TYPE**: SCHEDULE 13D

**PUBLIC DOCUMENT COUNT**: 5

**FILED AS OF DATE**: 20260511

**DATE AS OF CHANGE**: 20260511

**SUBJECT COMPANY**: 

**COMPANY DATA:**
- **COMPANY CONFORMED NAME:** Hemab Therapeutics Holdings, Inc.
- **CENTRAL INDEX KEY:** 0002114044
- **STANDARD INDUSTRIAL CLASSIFICATION:** BIOLOGICAL PRODUCTS (NO DIAGNOSTIC SUBSTANCES) [2836]
- **ORGANIZATION NAME:** 03 Life Sciences
- **EIN:** 414241952
- **STATE OF INCORPORATION:** DE
- **FISCAL YEAR END:** 1231

**FILING VALUES:**
- **FORM TYPE:** SCHEDULE 13D
- **SEC ACT:** 1934 Act
- **SEC FILE NUMBER:** 005-95667
- **FILM NUMBER:** 26963997

**BUSINESS ADDRESS:**
- **STREET 1:** 101 MAIN STREET
- **STREET 2:** SUITE 1220
- **CITY:** CAMBRIDGE
- **STATE:** MA
- **ZIP:** 02142
- **BUSINESS PHONE:** 45 2138 7627

**MAIL ADDRESS:**
- **STREET 1:** 101 MAIN STREET
- **STREET 2:** SUITE 1220
- **CITY:** CAMBRIDGE
- **STATE:** MA
- **ZIP:** 02142
**FILED BY**: 

**COMPANY DATA:**
- **COMPANY CONFORMED NAME:** AI DEN-MAB LLC
- **CENTRAL INDEX KEY:** 0002132038

**ORGANIZATION NAME:**
- **EIN:** 000000000
- **STATE OF INCORPORATION:** DE
- **FISCAL YEAR END:** 1231

**FILING VALUES:**
- **FORM TYPE:** SCHEDULE 13D

**BUSINESS ADDRESS:**
- **STREET 1:** C/O ACCESS INDUSTRIES, INC.
- **STREET 2:** 40 WEST 57TH STREET, 28TH FLOOR
- **CITY:** NEW YORK
- **STATE:** NY
- **ZIP:** 10019
- **BUSINESS PHONE:** 2122476400

**MAIL ADDRESS:**
- **STREET 1:** C/O ACCESS INDUSTRIES, INC.
- **STREET 2:** 40 WEST 57TH STREET, 28TH FLOOR
- **CITY:** NEW YORK
- **STATE:** NY
- **ZIP:** 10019

### Attached PDF Documents

**Attachment 1:** `ck0000000000-ex99_1.pdf`

_No text found in this document._

**Attachment 2:** `ck0000000000-ex99_2.pdf`

_No text found in this document._

**Attachment 3:** `ck0000000000-ex99_4.pdf`

_No text found in this document._

**Attachment 4:** `ck0000000000-ex99_5.pdf`

_No text found in this document._

### UNITED STATES SECURITIES AND EXCHANGE COMMISSION
**Washington, D.C. 20549**

## SCHEDULE 13D

### Under the Securities Exchange Act of 1934

**Hemab Therapeutics Holdings, Inc.**

*(Name of Issuer)*

**Common stock, par value $0.0001 per share**

*(Title of Class of Securities)*

**—**

*(CUSIP Number)*

**Alejandro Moreno**<br>Access Industries, Inc.<br>40 West 57th St., 28th Floor<br>New York NY 10019<br>(212) 247-6400

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

**05/04/2026**

*(Date of Event Which Requires Filing of this Statement)*

| **CUSIP No.** | **—** |

---

| | | | |
|:--|:--|:--|:--|
| 1 | Name of reporting person<br>**AI DEN-MAB LLC** | Name of reporting person<br>**AI DEN-MAB LLC** | |
| 2 | Check the appropriate box if a member of a Group (See Instructions)<br>[x] (a)<br>[ ] (b) | Check the appropriate box if a member of a Group (See Instructions)<br>[x] (a)<br>[ ] (b) | |
| 3 | SEC use only | SEC use only | |
| 4 | Source of funds (See Instructions)<br>**AF** | Source of funds (See Instructions)<br>**AF** | |
| 5 | Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)<br>[ ] | Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)<br>[ ] | |
| 6 | Citizenship or place of organization<br>**DELAWARE** | Citizenship or place of organization<br>**DELAWARE** | |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 7 | Sole Voting Power<br>**4876344.00** |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 8 | Shared Voting Power<br>**0.00** |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 9 | Sole Dispositive Power<br>**4876344.00** |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 10 | Shared Dispositive Power<br>**0.00** |
| 11 | Aggregate amount beneficially owned by each reporting person<br>**4876344.00** | Aggregate amount beneficially owned by each reporting person<br>**4876344.00** | |
| 12 | Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)<br>[ ] | Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)<br>[ ] | |
| 13 | Percent of class represented by amount in Row (11)<br>**10.4%** | Percent of class represented by amount in Row (11)<br>**10.4%** | |
| 14 | Type of Reporting Person (See Instructions)<br>**OO** | Type of Reporting Person (See Instructions)<br>**OO** | |

---

**Comment for Reporting Person:** Row 13. Based on an aggregate of 46,705,410 shares of Common Stock outstanding immediately following the Issuer's initial public offering, which assumes full exercise of the underwriters' option to purchase additional shares of Common Stock, as reported in the Issuer's prospectdus filed pursuant to Rule 424(b)(4) with the Securities and Exchange Commission (the "SEC") on May 1, 2026.

| **CUSIP No.** | **—** |

---

| | | | |
|:--|:--|:--|:--|
| 1 | Name of reporting person<br>**Access Industries Holdings LLC** | Name of reporting person<br>**Access Industries Holdings LLC** | |
| 2 | Check the appropriate box if a member of a Group (See Instructions)<br>[x] (a)<br>[ ] (b) | Check the appropriate box if a member of a Group (See Instructions)<br>[x] (a)<br>[ ] (b) | |
| 3 | SEC use only | SEC use only | |
| 4 | Source of funds (See Instructions)<br>**AF** | Source of funds (See Instructions)<br>**AF** | |
| 5 | Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)<br>[ ] | Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)<br>[ ] | |
| 6 | Citizenship or place of organization<br>**DELAWARE** | Citizenship or place of organization<br>**DELAWARE** | |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 7 | Sole Voting Power<br>**0.00** |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 8 | Shared Voting Power<br>**4876344.00** |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 9 | Sole Dispositive Power<br>**0.00** |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 10 | Shared Dispositive Power<br>**4876344.00** |
| 11 | Aggregate amount beneficially owned by each reporting person<br>**4876344.00** | Aggregate amount beneficially owned by each reporting person<br>**4876344.00** | |
| 12 | Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)<br>[ ] | Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)<br>[ ] | |
| 13 | Percent of class represented by amount in Row (11)<br>**10.4%** | Percent of class represented by amount in Row (11)<br>**10.4%** | |
| 14 | Type of Reporting Person (See Instructions)<br>**OO** | Type of Reporting Person (See Instructions)<br>**OO** | |

---

**Comment for Reporting Person:** Row 13. Based on an aggregate of 46,705,410 shares of Common Stock outstanding immediately following the Issuer's initial public offering, which assumes full exercise of the underwriters' option to purchase additional shares of Common Stock, as reported in the Issuer's prospectdus filed pursuant to Rule 424(b)(4) with the SEC on May 1, 2026.

| **CUSIP No.** | **—** |

---

| | | | |
|:--|:--|:--|:--|
| 1 | Name of reporting person<br>**AI Biotechnology LLC** | Name of reporting person<br>**AI Biotechnology LLC** | |
| 2 | Check the appropriate box if a member of a Group (See Instructions)<br>[x] (a)<br>[ ] (b) | Check the appropriate box if a member of a Group (See Instructions)<br>[x] (a)<br>[ ] (b) | |
| 3 | SEC use only | SEC use only | |
| 4 | Source of funds (See Instructions)<br>**AF** | Source of funds (See Instructions)<br>**AF** | |
| 5 | Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)<br>[ ] | Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)<br>[ ] | |
| 6 | Citizenship or place of organization<br>**DELAWARE** | Citizenship or place of organization<br>**DELAWARE** | |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 7 | Sole Voting Power<br>**0.00** |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 8 | Shared Voting Power<br>**4876344.00** |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 9 | Sole Dispositive Power<br>**0.00** |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 10 | Shared Dispositive Power<br>**4876344.00** |
| 11 | Aggregate amount beneficially owned by each reporting person<br>**4876344.00** | Aggregate amount beneficially owned by each reporting person<br>**4876344.00** | |
| 12 | Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)<br>[ ] | Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)<br>[ ] | |
| 13 | Percent of class represented by amount in Row (11)<br>**10.4%** | Percent of class represented by amount in Row (11)<br>**10.4%** | |
| 14 | Type of Reporting Person (See Instructions)<br>**OO** | Type of Reporting Person (See Instructions)<br>**OO** | |

---

**Comment for Reporting Person:** Row 13. Based on an aggregate of 46,705,410 shares of Common Stock outstanding immediately following the Issuer's initial public offering, which assumes full exercise of the underwriters' option to purchase additional shares of Common Stock, as reported in the Issuer's prospectdus filed pursuant to Rule 424(b)(4) with the SEC on May 1, 2026.

| **CUSIP No.** | **—** |

---

| | | | |
|:--|:--|:--|:--|
| 1 | Name of reporting person<br>**Access Industries Management LLC** | Name of reporting person<br>**Access Industries Management LLC** | |
| 2 | Check the appropriate box if a member of a Group (See Instructions)<br>[x] (a)<br>[ ] (b) | Check the appropriate box if a member of a Group (See Instructions)<br>[x] (a)<br>[ ] (b) | |
| 3 | SEC use only | SEC use only | |
| 4 | Source of funds (See Instructions)<br>**AF** | Source of funds (See Instructions)<br>**AF** | |
| 5 | Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)<br>[ ] | Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)<br>[ ] | |
| 6 | Citizenship or place of organization<br>**DELAWARE** | Citizenship or place of organization<br>**DELAWARE** | |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 7 | Sole Voting Power<br>**0.00** |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 8 | Shared Voting Power<br>**4876344.00** |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 9 | Sole Dispositive Power<br>**0.00** |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 10 | Shared Dispositive Power<br>**4876344.00** |
| 11 | Aggregate amount beneficially owned by each reporting person<br>**4876344.00** | Aggregate amount beneficially owned by each reporting person<br>**4876344.00** | |
| 12 | Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)<br>[ ] | Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)<br>[ ] | |
| 13 | Percent of class represented by amount in Row (11)<br>**10.4%** | Percent of class represented by amount in Row (11)<br>**10.4%** | |
| 14 | Type of Reporting Person (See Instructions)<br>**OO** | Type of Reporting Person (See Instructions)<br>**OO** | |

---

**Comment for Reporting Person:** Row 13. Based on an aggregate of 46,705,410 shares of Common Stock outstanding immediately following the Issuer's initial public offering, which assumes full exercise of the underwriters' option to purchase additional shares of Common Stock, as reported in the Issuer's prospectdus filed pursuant to Rule 424(b)(4) with the SEC on May 1, 2026.

| **CUSIP No.** | **—** |

---

| | | | |
|:--|:--|:--|:--|
| 1 | Name of reporting person<br>**Len Blavatnik** | Name of reporting person<br>**Len Blavatnik** | |
| 2 | Check the appropriate box if a member of a Group (See Instructions)<br>[x] (a)<br>[ ] (b) | Check the appropriate box if a member of a Group (See Instructions)<br>[x] (a)<br>[ ] (b) | |
| 3 | SEC use only | SEC use only | |
| 4 | Source of funds (See Instructions)<br>**AF** | Source of funds (See Instructions)<br>**AF** | |
| 5 | Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)<br>[ ] | Check if disclosure of legal proceedings is required pursuant to Items 2(d) or 2(e)<br>[ ] | |
| 6 | Citizenship or place of organization<br>**X1** | Citizenship or place of organization<br>**X1** | |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 7 | Sole Voting Power<br>**0.00** |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 8 | Shared Voting Power<br>**4876344.00** |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 9 | Sole Dispositive Power<br>**0.00** |
| Number of Shares<br>Beneficially Owned by<br>Each Reporting Person With: | 10 | Shared Dispositive Power<br>**4876344.00** |
| 11 | Aggregate amount beneficially owned by each reporting person<br>**4876344.00** | Aggregate amount beneficially owned by each reporting person<br>**4876344.00** | |
| 12 | Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)<br>[ ] | Check if the aggregate amount in Row (11) excludes certain shares (See Instructions)<br>[ ] | |
| 13 | Percent of class represented by amount in Row (11)<br>**10.4%** | Percent of class represented by amount in Row (11)<br>**10.4%** | |
| 14 | Type of Reporting Person (See Instructions)<br>**IN** | Type of Reporting Person (See Instructions)<br>**IN** | |

---

**Comment for Reporting Person:** Row 13. Based on an aggregate of 46,705,410 shares of Common Stock outstanding immediately following the Issuer's initial public offering, which assumes full exercise of the underwriters' option to purchase additional shares of Common Stock, as reported in the Issuer's prospectdus filed pursuant to Rule 424(b)(4) with the SEC on May 1, 2026.

**Item 1. Security and Issuer**

**(a) Title of Class of Securities:**
Common stock, par value $0.0001 per share

**(b) Name of Issuer:**
Hemab Therapeutics Holdings, Inc.

**(c) Address of Issuer's Principal Executive Offices:**
101 Main Street, Suite 1220, Cambridge, MA, 02142

This Schedule 13D is being filed by AI DEN-MAB LLC ("AI DMAB"), AI Biotechnology LLC ("AI Biotechnology"), Access Industries Holdings LLC ("AIH"), Access Industries Management, LLC ("AIM") and Len Blavatnik (collectively, the Reporting Persons", and each, a "Reporting Person"), in respect of the common stock, par value $0.0001 per share (the "Common Stock") of Hemab Therapeutics Holdings, Inc. (the "Issuer").

**Item 4. Purpose of Transaction**

The Reporting Persons who hold Common Stock directly acquired those securities as an investment in the regular course of their businesses. The Reporting Persons may engage in discussions with management, the Issuer's board of directors, other stockholders of the Issuer and other relevant parties concerning the business, operations, board composition, management, strategy and future plans of the Issuer. Subject to the terms of the Investors' Rights Agreement (as defined below), the Reporting Persons intend to re-examine their investment from time to time and, depending on prevailing market conditions, other investment opportunities, liquidity requirements or other investment considerations the Reporting Persons deem material, the Reporting Persons may from time to time acquire additional Common Stock in the open market, block trades, negotiated transactions, or otherwise and may also dispose of all or a portion of the Issuer's securities, in open market or privately negotiated transactions, and/or enter into derivative transactions with institutional counterparties with respect to the Issuer's securities, in each case, subject to limitations under applicable law. The Reporting Persons have not yet determined which, if any, of the above courses of action they may ultimately take. The Reporting Persons' future actions with regard to the Issuer are dependent on their evaluation of the factors listed above, circumstances affecting the Issuer in the future, including prospects of the Issuer, general market and economic conditions and other factors deemed relevant. The Reporting Persons reserve the right to determine in the future whether to change the purpose or purposes described above or whether to adopt plans or proposals of the type specified above or otherwise.

**Item 5. Interest in Securities of the Issuer**

**(a)**
The responses of each of the Reporting Persons with respect to Rows 11, 12, and 13 of the cover pages of this Schedule 13D that relate to the aggregate number of shares and percentage of Common Stock (including but not limited to footnotes to such information) are incorporated herein by reference.

**(b)**
The responses of each of the Reporting Persons with respect to Rows 7, 8, 9, and 10 of the cover pages of this Schedule 13D that relate to the number of shares of Common Stock as to which each of the persons or entities referenced in Item 2 above has sole or shared power to vote or to direct the vote of and sole or shared power to dispose of or to direct the disposition of (including but not limited to footnotes to such information) are incorporated herein by reference.

**(c)**
The following transactions in the Issuer's securities have been effected by the Reporting Persons within the 60 days prior to this filing: The information set forth in Item 3 of this Schedule 13D is incorporated herein by reference.

**Item 6. Contracts, Arrangements, Understandings or Relationships With Respect to Securities of the Issuer.**

Lock-up Agreement

In connection with the Issuer's initial public offering, on March 17, 2026, AI DMAB entered into a lock-up agreement (the "Lock-up Agreement") with Goldman Sachs & Co. LLC, Jefferies LLC and Evercore Group L.L.C., as representatives of the underwriters. Pursuant to the Lock-up Agreement, AI DMAB has agreed that it will not, directly or indirectly, offer, sell, contract to sell, pledge, grant any option, right or warrant to purchase, purchase any option or contract to sell, lend or otherwise transfer or dispose of any ordinary shares or preference shares of Hemab ApS, any shares of Common Stock, or any options or warrants to purchase any shares of Common Stock, or any securities convertible into, exchangeable for or that represent the right to receive shares of Common Stock, enter into any hedging, swap or other arrangement that transfers, in whole or in part, the economic consequences of ownership of Common Stock, make any demand for or exercise any right with respect to the registration of any such equity securities, or make any public announcement of an intention to do any of the foregoing for a period of 180 days following April 30, 2026, the date of the Issuer's prospectus filed pursuant to Rule 424(b)(4) with the SEC, without the prior written consent of Goldman Sachs & Co. LLC, Jefferies LLC and Evercore Group L.L.C., subject to certain exceptions. Goldman Sachs & Co. LLC, Jefferies LLC and Evercore Group L.L.C., on behalf of the underwriters, may release all or any portion of the securities subject to the Lock-up Agreement at any time and without notice before the termination of the 180-day period.

The foregoing description of the Lock-up Agreement does not purport to be complete and is qualified in its entirety by reference to such, which is filed as an exhibit and incorporated herein by reference.

Investors' Rights Agreement

AI DMAB is party to an investors' rights agreement (the "Investors' Rights Agreement"), dated March 30, 2026, by and among the Issuer and certain of its stockholders named therein. Pursuant to the terms of the Investors' Rights Agreement, beginning 180 days after April 30, 2026, the effective date of the registration statement for the Issuer's initial public offering, holders who are party to the Investors' Rights Agreement and who collectively hold at least 30% of the then outstanding Registrable Securities (as defined therein) have the right to require the Issuer to file a registration statement on Form S-1 to register at least 25% of the then outstanding Registrable Securities, or a lesser percent if the anticipated aggregate offering price, net of selling expenses, would exceed $10 million, subject to customary terms and conditions. At any time the Issuer is eligible to use a Form S-3 registration statement, holders who are party to the Investors' Rights Agreement and who collectively hold at least 20% of the then outstanding Registrable Securities have the right to require the Issuer to file a registration statement on Form S-3 to register outstanding Registrable Securities of such holders having an anticipated aggregate offering price, net of selling expenses, of at least $5 million, subject to customary terms and conditions. Pursuant to the Investors' Rights Agreement, AI DMAB and its permitted transferees have customary piggyback registration rights, subject to customary terms and conditions.

The foregoing description of the Investors' Rights Agreement does not purport to be complete and is qualified in its entirety by reference to such, which is filed as an exhibit and incorporated herein by reference.

Joint Filing Agreement

A Joint Filing Agreement, dated May 11, 2026, by and among the Reporting Persons has been executed by the Reporting Persons, a copy of which is attached hereto as Exhibit 99.4 and is incorporated herein by reference.

### 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.

**Reporting Person:** AI DEN-MAB LLC

**Signature:** /s/ Alejandro Moreno

**Name/Title:** By: Access Industries Management, LLC, its manager; its Executive Vice President, General Counsel/Alejandro Moreno

**Date:** 05/11/2026

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.

**Reporting Person:** Access Industries Holdings LLC

**Signature:** /s/ Alejandro Moreno

**Name/Title:** By: Access Industries Management, LLC, its manager; its Executive Vice President, General Counsel/Alejandro Moreno

**Date:** 05/11/2026

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.

**Reporting Person:** AI Biotechnology LLC

**Signature:** /s/ Alejandro Moreno

**Name/Title:** By: Access Industries Management, LLC, its manager; its Executive Vice President, General Counsel/Alejandro Moreno

**Date:** 05/11/2026

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.

**Reporting Person:** Access Industries Management LLC

**Signature:** /s/ Alejandro Moreno

**Name/Title:** By: Executive Vice President, General Counsel/Alejandro Moreno

**Date:** 05/11/2026

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.

**Reporting Person:** Len Blavatnik

**Signature:** */s/ Alejandro Moreno

**Name/Title:** By: Alejandro Moreno as Attorney-in-Fact for Len Blavatnik

**Date:** 05/11/2026