# EDGAR Filing Document

**Accession Number:** 0002075320
**File Stem:** 0001213900-26-012759
**Filing Date:** 2026-2
**Character Count:** 15870
**Document Hash:** f491c0cde16307d0a05cd961c45dadc3
**Contains OCR:** False
**Source Format:** 

## Filing Content

## Filing Summary
**0001213900-26-012759.hdr.sgml**: 20260205

**ACCESSION NUMBER**: 0001213900-26-012759

**CONFORMED SUBMISSION TYPE**: SCHEDULE 13D

**PUBLIC DOCUMENT COUNT**: 2

**FILED AS OF DATE**: 20260205

**DATE AS OF CHANGE**: 20260205

**SUBJECT COMPANY**: 

**COMPANY DATA:**
- **COMPANY CONFORMED NAME:** Polaryx Therapeutics, Inc.
- **CENTRAL INDEX KEY:** 0002075320
- **STANDARD INDUSTRIAL CLASSIFICATION:** PHARMACEUTICAL PREPARATIONS [2834]
- **ORGANIZATION NAME:** 03 Life Sciences
- **EIN:** 000000000
- **STATE OF INCORPORATION:** WY
- **FISCAL YEAR END:** 1231

**FILING VALUES:**
- **FORM TYPE:** SCHEDULE 13D
- **SEC ACT:** 1934 Act
- **SEC FILE NUMBER:** 005-95464
- **FILM NUMBER:** 26602866

**BUSINESS ADDRESS:**
- **STREET 1:** 140 EAST RIDGEWOOD AVENUE
- **STREET 2:** SUITE 415, SOUTH TOWER
- **CITY:** PARAMUS
- **STATE:** NJ
- **ZIP:** 07652
- **BUSINESS PHONE:** 201-940-7236

**MAIL ADDRESS:**
- **STREET 1:** SOUTH TOWER, 140 E RIDGEWOOD AVENUE
- **STREET 2:** SUITE 415
- **CITY:** PARAMUS
- **STATE:** NJ
- **ZIP:** 07652
**FILED BY**: 

**COMPANY DATA:**
- **COMPANY CONFORMED NAME:** Mstone Partners Healthcare Ltd
- **CENTRAL INDEX KEY:** 0002104809

**ORGANIZATION NAME:**
- **EIN:** 000000000
- **STATE OF INCORPORATION:** K3
- **FISCAL YEAR END:** 1231

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

**BUSINESS ADDRESS:**
- **ADDRESS IS A NON US LOCATION:** YES
- **STREET 1:** 7/F 80 GLOUCESTER ROAD
- **CITY:** WANCHAI
- **PROVINCE COUNTRY:** K3
- **ZIP:** 00000
- **BUSINESS PHONE:** 852 2155 9599

**MAIL ADDRESS:**
- **ADDRESS IS A NON US LOCATION:** YES
- **STREET 1:** 7/F 80 GLOUCESTER ROAD
- **CITY:** WANCHAI
- **PROVINCE COUNTRY:** K3
- **ZIP:** 00000

## Exhibit 99.1

**Exhibit 99.1**

AGREEMENT REGARDING JOINT FILING

OF STATEMENT ON SCHEDULE 13D OR 13G

In accordance with Rule 13d-1(k) under the Securities Exchange Act of 1934, as amended, the undersigned agree to the joint filing on behalf of each of them of a Statement on Schedule 13D (including any and all amendments thereto) with respect to the Common stock, par value $0.0001 per share, of Polaryx Therapeutics, Inc. and further agree that this Joint Filing Agreement shall be included as an exhibit to such joint filing.

The undersigned further agree that each party hereto is responsible for the timely filing of such Statement on Schedule 13D and any amendments thereto, and for the accuracy and completeness of the information concerning such party contained therein; provided, however, that no party is responsible for the accuracy or completeness of the information concerning any other party, unless such party knows or has reason to believe that such information is inaccurate.

This Joint Filing Agreement may be signed in counterparts with the same effect as if the signature on each counterpart were upon the same instrument.

Dated: February 5, 2026

---

| | | | |
|:---|:---|:---|:---|
| **MSTONE PARTNERS HEALTHCARE LIMITED** | **MSTONE PARTNERS HEALTHCARE LIMITED** | **MBSTONE BIOTECH FLAGSHIP LIMITED** | **MBSTONE BIOTECH FLAGSHIP LIMITED** |
| By: | /s/ *Alex Keun Mo Yang* | By: | /s/ *Alex Keun Mo Yang* |
| Alex Keun Mo Yang | Alex Keun Mo Yang | Alex Keun Mo Yang | Alex Keun Mo Yang |
| Chief Executive Officer | Chief Executive Officer | Chief Executive Officer | Chief Executive Officer |
| **MSTONE PEDIAORPHAN SINGAPORE I PTE. LIMITED** | **MSTONE PEDIAORPHAN SINGAPORE I PTE. LIMITED** |  |  |
| By: | /s/ *Alex Keun Mo Yang* | By: | /s/ *Alex Keun Mo Yang* |
| Alex Keun Mo Yang | Alex Keun Mo Yang | Alex Keun Mo Yang | Alex Keun Mo Yang |
| Chief Executive Officer | Chief Executive Officer |  |  |

---

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

## SCHEDULE 13D

### Under the Securities Exchange Act of 1934

**Polaryx Therapeutics, Inc.**

*(Name of Issuer)*

**Common stock, par value $0.0001 per share ("Common Stock")**

*(Title of Class of Securities)*

**73110F100**

*(CUSIP Number)*

**Alex Keun Mo Yang**<br>c/o Mstone Partners Healthcare Limited<br>7/F, 80 Gloucester Road<br>Wan Chai K3 00000<br>852-2155-0487

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

**01/29/2026**

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

| **CUSIP No.** | **73110F100** |

---

| | | | |
|:--|:--|:--|:--|
| 1 | Name of reporting person<br>**Mstone Partners Healthcare Limited** | Name of reporting person<br>**Mstone Partners Healthcare Limited** | |
| 2 | Check the appropriate box if a member of a Group (See Instructions)<br>[ ] (a)<br>[x] (b) | Check the appropriate box if a member of a Group (See Instructions)<br>[ ] (a)<br>[x] (b) | |
| 3 | SEC use only | SEC use only | |
| 4 | Source of funds (See Instructions)<br>**WC** | Source of funds (See Instructions)<br>**WC** | |
| 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>**HONG KONG** | Citizenship or place of organization<br>**HONG KONG** | |
| 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>**22452954.00** |
| 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>**22452954.00** |
| 11 | Aggregate amount beneficially owned by each reporting person<br>**22452954.00** | Aggregate amount beneficially owned by each reporting person<br>**22452954.00** | |
| 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>**47.4%** | Percent of class represented by amount in Row (11)<br>**47.4%** | |
| 14 | Type of Reporting Person (See Instructions)<br>**CO** | Type of Reporting Person (See Instructions)<br>**CO** | |

---

**Comment for Reporting Person:** Based on 47,343,297 shares of common stock outstanding as of January 12, 2026.

| **CUSIP No.** | **73110F100** |

---

| | | | |
|:--|:--|:--|:--|
| 1 | Name of reporting person<br>**MBstone Biotech Flagship Limited** | Name of reporting person<br>**MBstone Biotech Flagship Limited** | |
| 2 | Check the appropriate box if a member of a Group (See Instructions)<br>[ ] (a)<br>[x] (b) | Check the appropriate box if a member of a Group (See Instructions)<br>[ ] (a)<br>[x] (b) | |
| 3 | SEC use only | SEC use only | |
| 4 | Source of funds (See Instructions)<br>**WC** | Source of funds (See Instructions)<br>**WC** | |
| 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>**HONG KONG** | Citizenship or place of organization<br>**HONG KONG** | |
| 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>**183560.00** |
| 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>**183560.00** |
| 11 | Aggregate amount beneficially owned by each reporting person<br>**183560.00** | Aggregate amount beneficially owned by each reporting person<br>**183560.00** | |
| 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>**0.4%** | Percent of class represented by amount in Row (11)<br>**0.4%** | |
| 14 | Type of Reporting Person (See Instructions)<br>**CO** | Type of Reporting Person (See Instructions)<br>**CO** | |

---

**Comment for Reporting Person:** Based on 47,343,297 shares of common stock outstanding as of January 12, 2026.

| **CUSIP No.** | **73110F100** |

---

| | | | |
|:--|:--|:--|:--|
| 1 | Name of reporting person<br>**Mstone Pediaorphan Singapore I Pte. Limited** | Name of reporting person<br>**Mstone Pediaorphan Singapore I Pte. Limited** | |
| 2 | Check the appropriate box if a member of a Group (See Instructions)<br>[ ] (a)<br>[x] (b) | Check the appropriate box if a member of a Group (See Instructions)<br>[ ] (a)<br>[x] (b) | |
| 3 | SEC use only | SEC use only | |
| 4 | Source of funds (See Instructions)<br>**WC** | Source of funds (See Instructions)<br>**WC** | |
| 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>**U0** | Citizenship or place of organization<br>**U0** | |
| 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>**108282.00** |
| 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>**108282.00** |
| 11 | Aggregate amount beneficially owned by each reporting person<br>**108282.00** | Aggregate amount beneficially owned by each reporting person<br>**108282.00** | |
| 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>**0.2%** | Percent of class represented by amount in Row (11)<br>**0.2%** | |
| 14 | Type of Reporting Person (See Instructions)<br>**CO** | Type of Reporting Person (See Instructions)<br>**CO** | |

---

**Comment for Reporting Person:** Based on 47,343,297 shares of common stock outstanding as of January 12, 2026.

| **CUSIP No.** | **73110F100** |

---

| | | | |
|:--|:--|:--|:--|
| 1 | Name of reporting person<br>**Alex Keun Mo Yang** | Name of reporting person<br>**Alex Keun Mo Yang** | |
| 2 | Check the appropriate box if a member of a Group (See Instructions)<br>[ ] (a)<br>[x] (b) | Check the appropriate box if a member of a Group (See Instructions)<br>[ ] (a)<br>[x] (b) | |
| 3 | SEC use only | SEC use only | |
| 4 | Source of funds (See Instructions)<br>**WC** | Source of funds (See Instructions)<br>**WC** | |
| 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>**M5** | Citizenship or place of organization<br>**M5** | |
| 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>**22744796.00** |
| 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>**22744796.00** |
| 11 | Aggregate amount beneficially owned by each reporting person<br>**22744796.00** | Aggregate amount beneficially owned by each reporting person<br>**22744796.00** | |
| 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>**48.0%** | Percent of class represented by amount in Row (11)<br>**48.0%** | |
| 14 | Type of Reporting Person (See Instructions)<br>**IN** | Type of Reporting Person (See Instructions)<br>**IN** | |

---

**Comment for Reporting Person:** Based on 47,343,297 shares of common stock outstanding as of January 12, 2026.

**Item 1. Security and Issuer**

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

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

**(c) Address of Issuer's Principal Executive Offices:**
South Tower, 140 E Ridgewood Avenue, Suite 415, Paramus, NJ, 07652

**Item 4. Purpose of Transaction**

The Reporting Persons own 48.0% of the Company in the aggregate, based on 47,343,297 shares of Common Stock outstanding as of January 12, 2026.

Mr. Yang serves as Chief Executive Officer and as a member of the board of directors of the Company (the "Board"), and, in such capacity, may have influence over the corporate activities of the Company, including activities which may relate to items described in subparagraphs (a) through (j) of Item 4 of Schedule 13D.

Except as described in this Schedule 13D, the Reporting Persons do not have any present plans or proposals that relate to or would result in any of the actions described in subparagraphs (a) through (j) of Item 4 of Schedule 13D, although, the Reporting Persons, at any time and from time to time, may review, reconsider and change their position and/or change their purpose and/or develop such plans and may seek to influence management or the Board with respect to the business and affairs of the Company and may from time to time consider pursuing or proposing such matters with advisors, the Company or other persons.

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

**(a)**
The information set forth in Items 2 and 3 and on the cover pages of this Schedule 13D is incorporated by reference in its entirety into this Item 5. The percentages used in this Schedule 13D are calculated based on 47,343,297 shares of Common Stock outstanding as of January 12, 2026.

**(b)**
See Item 5(a) hereof.

**(c)**
N/A.

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

None.

### 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:** Mstone Partners Healthcare Limited

**Signature:** /s/ Alex Keun Mo Yang

**Name/Title:** Chief Executive Officer

**Date:** 02/05/2026

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:** MBstone Biotech Flagship Limited

**Signature:** /s/ Alex Keun Mo Yang

**Name/Title:** Chief Executive Officer

**Date:** 02/05/2026

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:** Mstone Pediaorphan Singapore I Pte. Limited

**Signature:** /s/ Alex Keun Mo Yang

**Name/Title:** Chief Executive Officer

**Date:** 02/05/2026

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:** Alex Keun Mo Yang

**Signature:** /s/ Alex Keun Mo Yang

**Name/Title:** Reporting person

**Date:** 02/05/2026