Alex Keun Mo Yang - 29 Jan 2026 Form 3 Insider Report for Polaryx Therapeutics, Inc. (PLYX)

Reporting relationship: Chief Executive Officer, Director, 10%+ Owner
Issuer ticker: PLYX
Reported as of: 29 Jan 2026
Net transaction value: $0
SEC form: 3
Accepted by SEC: 29 Jan 2026, 18:07:38 UTC
Next SEC filing: 28 May 2026
Source filing: View source filing
Reporting owner signature: /s/ Alex Keun Mo Yang

Key filing fact

Alex Keun Mo Yang filed Form 3 for Polaryx Therapeutics, Inc. (PLYX) on 29 Jan 2026.

Key facts

This page summarizes Alex Keun Mo Yang's Form 3 filing for Polaryx Therapeutics, Inc. (PLYX).
0 reported transactions and 0 derivative rows are listed below.
Accepted by SEC: 29 Jan 2026, 18:07.

Change

No earlier filing in this sequence is available for direct comparison.
Current net transaction value: $0.

Research use

This tells you what this filing adds before you inspect full transaction and derivative tables.
You can trace every row back to the original SEC filing document.

Evidence

Official SEC source

Ownership activity is grounded in SEC Form 3 disclosures.

View source filing

Reporting Owners (2)

CIK 0002103399 Primary reporting owner

Yang Alex Keun Mo

Relationship: Chief Executive Officer, Director, 10%+ Owner
Address: SOUTH TOWER, 140 E RIDGEWOOD AVENUE,, SUITE 415, PARAMUS
Signature: /s/ Alex Keun Mo Yang
Signature date: 29 Jan 2026

CIK 0002104809

Mstone Partners Healthcare Ltd

Relationship: Director, 10%+ Owner
Address: 7/F, 80 GLOUCESTER ROAD, WANCHAI, HONG KONG
Signature: /s/ Alex Keun Mo Yang, Chief Executive Officer of Mstone Partners Healthcare Limited
Signature date: 29 Jan 2026

Reported non-derivative transactions

Shares, units, or other non-derivative securities reported in this filing.

PLYX holding

Common Stock

No transaction description listed

Transaction value
Shares
Change %
Price
Shares after: 1,400,000
Date: 29 Jan 2026
Ownership: Direct
Footnotes: F1

PLYX holding

Common Stock

No transaction description listed

Transaction value
Shares
Change %
Price
Shares after: 22,452,954
Date: 29 Jan 2026
Ownership: By Mstone Partners Healthcare Limited
Footnotes: F2

PLYX holding

Common Stock

No transaction description listed

Transaction value
Shares
Change %
Price
Shares after: 183,560
Date: 29 Jan 2026
Ownership: By MBstone Biotech Flagship Limited
Footnotes: F3

PLYX holding

Common Stock

No transaction description listed

Transaction value
Shares
Change %
Price
Shares after: 108,282
Date: 29 Jan 2026
Ownership: By Mstone Pediaorphan Singapore I Pte. Limited
Footnotes: F4

^* marks a reported price that did not pass the local price check.

Additional SEC filing notes

Filing notes and footnotes

Explanation of responses 4 footnotes

Footnote F1

Includes (i) 148,500 restricted stock units ("RSUs"), which will vest on March 1, 2026, (ii) 330,000 RSUs, which will vest in two equal installments on November 1, 2026 and November 1, 2027 and (iii) 450,000 RSUs, which will vest in four equal installments on September 1, 2026, September 1, 2027, September 1, 2028 and September 1, 2029, in each case subject to the Reporting Person's continued service to the Issuer or its subsidiaries, Mstone Partners Healthcare Limited ("Mstone") or its affiliates, or Curestone Partners Platform Limited or its affiliates. The RSUs are not deliverable unless and until the Issuer consummates a change in control within seven years of the grant date of such RSUs.

Footnote F2

Alex Keun Mo Yang is the founder and Chief Executive Officer of Mstone. Mr. Yang disclaims beneficial ownership over any of the reported securities, except to the extent of his pecuniary interest therein.

Footnote F3

Mr. Yang is the Chief Executive Officer of MBstone Biotech Flagship Limited. Mr. Yang disclaims beneficial ownership over any of the reported securities, except to the extent of his pecuniary interest therein.

Footnote F4

Mr. Yang is the Chief Executive Officer of Mstone Pediaorphan Singapore I Pte. Limited. Mr. Yang disclaims beneficial ownership over any of the reported securities owned, except to the extent of his pecuniary interest therein.

SEC remarks

Exhibit 24 - Power of Attorney Mstone, MBstone Biotech Flagship Limited and Mstone Pediaorphan Singapore I Pte. Limited may each be deemed a director by deputization of the Issuer by virtue of the fact that Mr. Yang serves on the board of directors of the Issuer and is the Chief Executive Officer of each of the entities.