Mstone Partners Healthcare Ltd - 29 Jan 2026 SCHEDULE 13D Report for Polaryx Therapeutics, Inc. Common stock, par value $0.0001 per share ("Common Stock")

Filing manager
Mstone Partners Healthcare Ltd
Reporting owner
Alex Keun Mo Yang
Security
Polaryx Therapeutics, Inc. Common stock, par value $0.0001 per share ("Common Stock")
Beneficially owned shares
22,744,796 shares
Ownership signal CIK-linked ownership evidence from parsed SEC filings. 2 signals
Large-stake signal

Form

SCHEDULE 13D

Active or control-oriented beneficial ownership filing.

Ownership

48%

Beneficial ownership of this reported class.

Shares

22,744,796 shares

Shares beneficially owned as disclosed.

Event date

29 Jan 2026

Date tied to the ownership event or amendment.

Accepted by SEC

05 Feb 2026

EDGAR acceptance date.

How to read this large-stake filing
  • Schedule 13D/G filings focus on beneficial ownership stakes, not a full portfolio.
  • Compare this filing with the holder history and issuer page before treating the percentage as a current position.
  • Use amendments to understand whether the disclosed stake increased, decreased, or changed reporting status.
Class ownership
48%
Subject security Names, identifiers, and filing context for this profile. 1 source field
Shares outstanding
47,384,992 shares
Source evidence Original filing metadata and source links for verification. 4 source fields
SEC form
SCHEDULE 13D
Accepted by SEC
05 Feb 2026, 16:05:20 UTC
Event date
29 Jan 2026
Source filing
View source filing

Key filing fact

Mstone Partners Healthcare Ltd disclosed 48% ownership in Polaryx Therapeutics, Inc. Common stock, par value $0.0001 per share ("Common Stock") on 29 Jan 2026.

Key facts

  • Mstone Partners Healthcare Ltd filed SCHEDULE 13D for Polaryx Therapeutics, Inc. Common stock, par value $0.0001 per share ("Common Stock").
  • Disclosed ownership: 48%.
  • Date of event: 29 Jan 2026.

Change

  • No earlier schedule filing is available for direct comparison.
  • Current filing was accepted on 05 Feb 2026, 16:05.

Research use

  • This page turns one Schedule 13D/G filing into a quick large-stake read before the raw reporting-person rows.
  • Use the linked SEC filing as the source of truth for ownership percentages, shares, and reporting-party details.

Evidence

Backed by Schedule 13D/13G

Beneficial ownership values are sourced from the original SEC Schedule 13D/13G filing.

View source filing

Reporting persons

Disclosed reporting parties (4)

Names, ownership percentages, voting power, signatures, titles, and CIKs as disclosed in this Schedule 13D/G filing.

Name Ownership Shares owned Sole voting power Shared voting power Signature Title CIK
Mstone Partners Healthcare Limited 47% 22,452,954 0 22,452,954 /s/ Alex Keun Mo Yang Chief Executive Officer 0002104809
MBstone Biotech Flagship Limited 0.4% 183,560 0 183,560 /s/ Alex Keun Mo Yang Chief Executive Officer
Mstone Pediaorphan Singapore I Pte. Limited 0.2% 108,282 0 108,282 /s/ Alex Keun Mo Yang Chief Executive Officer
Alex Keun Mo Yang 48% 22,744,796 0 22,744,796 /s/ Alex Keun Mo Yang Reporting person 0002103399
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