MStone affiliate of Polaryx Therapeutics (PLYX) buys 88K common shares

Rhea-AI Filing Summary

Polaryx Therapeutics, Inc. reported an insider-related open-market purchase of common stock. On May 27, 2026, MStone Partners Healthcare Limited bought 88,453 shares of Polaryx common stock at $4.07 per share, in a private placement that generated $360,000 in gross proceeds for the company. After this transaction, MStone held 24,233,249 shares of common stock indirectly. Polaryx CEO Alex Keun Mo Yang is the founder and Chief Executive Officer of MStone and disclaims beneficial ownership of these securities except to the extent of his pecuniary interest.

Insights

Equity capital markets analyst

MStone affiliate of Polaryx’s CEO added shares in a $360,000 private placement.

The transaction shows MStone Partners Healthcare Limited purchasing 88,453 shares of Polaryx common stock at $4.07 per share in a private placement, providing $360,000 in gross proceeds to the company. It is classified as an open-market or private purchase.

Following the trade, MStone’s holdings increased to 24,233,249 shares, according to the filing. Alex Keun Mo Yang, Polaryx’s CEO and MStone’s founder and CEO, formally disclaims beneficial ownership beyond his pecuniary interest, which limits direct attribution of this position to him personally.

The filing does not reference any Rule 10b5-1 trading plan, suggesting this was a discretionary transaction by MStone. Future company filings may clarify how frequently Polaryx raises capital via similar private placements and how that interacts with its broader financing strategy.

Insider Trade Summary

Net Buyer: 88,453 shares ($360,004)

Net Buy 1 txn

Insider Yang Alex Keun Mo, Mstone Partners Healthcare Ltd

Role Chief Executive Officer | null

Bought 88,453 shs ($360K)

Type	Security	Shares	Price	Value
Purchase	Common Stock	88,453	$4.07	$360K

Holdings After Transaction: Common Stock — 24,233,249 shares (Indirect, By Mstone Partners Healthcare Limited)

Footnotes (1)

1. As disclosed in the Issuer's Form 8-K filed with the Securities and Exchange Commission on May 28, 2026, MStone Partners Healthcare Limited ("Mstone") purchased 88,453 shares of common stock in a private placement transaction, for gross proceeds to the Issuer of $360,000. 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.

Key Figures

Shares purchased: 88,453 shares Purchase price: $4.07 per share Gross proceeds to issuer: $360,000 +1 more

4 metrics

Shares purchased 88,453 shares Common stock bought by MStone on May 27, 2026

Purchase price $4.07 per share Price paid by MStone in private placement

Gross proceeds to issuer $360,000 Cash received by Polaryx from private placement

Post-transaction holdings 24,233,249 shares MStone’s indirect Polaryx common stock holdings after purchase

Key Terms

private placement, gross proceeds, beneficial ownership, pecuniary interest

4 terms

private placement financial

"MStone Partners Healthcare Limited purchased 88,453 shares of common stock in a private placement transaction"

A private placement is a way for companies to raise money by selling securities directly to a small group of investors instead of through a public offering. This process is often quicker and less regulated, making it similar to offering a special, exclusive investment opportunity to select individuals or institutions. For investors, it can provide access to unique investment options that are not available on public markets.

gross proceeds financial

"purchased 88,453 shares of common stock in a private placement transaction, for gross proceeds to the Issuer of $360,000"

The total amount of cash a company receives from a financing event or sale before any fees, expenses, taxes or deductions are taken out. Investors watch gross proceeds because it shows the raw scale of new capital being raised—think of it as the paycheck amount before withholdings—which helps assess how much funding is available for operations, growth, debt payoff or how much shareholder dilution might occur once costs are removed.

beneficial ownership financial

"Mr. Yang disclaims beneficial ownership over any of the reported securities"

Beneficial ownership means the person or entity that actually enjoys the benefits of owning shares or other assets — such as receiving dividends, voting rights, or price gains — even if the legal title is held in another name. For investors it matters because knowing who truly controls and profits from a company reveals who can influence decisions, exposes potential conflicts of interest or hidden concentration of power, and affects transparency and risk in the stock.

pecuniary interest financial

"Mr. Yang disclaims beneficial ownership over any of the reported securities, except to the extent of his pecuniary interest therein"

Form 4 Insider Transactions: What Each Field Means →

SEC Form 4

FORM 4

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

STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP

Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934
or Section 30(h) of the Investment Company Act of 1940

OMB APPROVAL

OMB Number:			3235-0287
Estimated average burden
hours per response:			0.5

Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

Check this box to indicate that a transaction was made pursuant to a contract, instruction or written plan for the purchase or sale of equity securities of the issuer that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c). See Instruction 10.

1. Name and Address of Reporting Person^*

Yang Alex Keun Mo

(Last) (First) (Middle)

SOUTH TOWER, 140 E RIDGEWOOD AVENUE,

SUITE 415

(Street)

PARAMUS NEW JERSEY 07652

(City) (State) (Zip)

UNITED STATES

(Country)

2. Issuer Name and Ticker or Trading Symbol
Polaryx Therapeutics, Inc. [ PLYX ]

5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)

X	Director	X	10% Owner
X	Officer (give title below)		Other (specify below)
	Chief Executive Officer

2a. Foreign Trading Symbol

3. Date of Earliest Transaction (Month/Day/Year)
05/27/2026

6. Individual or Joint/Group Filing (Check Applicable Line)

	Form filed by One Reporting Person
X	Form filed by More than One Reporting Person

4. If Amendment, Date of Original Filed (Month/Day/Year)

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1. Title of Security (Instr. 3)	2. Transaction Date (Month/Day/Year)	2A. Deemed Execution Date, if any (Month/Day/Year)	3. Transaction Code (Instr. 8)		4. Securities Acquired (A) or Disposed Of (D) (Instr. 3, 4 and 5)			5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4)	6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	7. Nature of Indirect Beneficial Ownership (Instr. 4)
			Code	V	Amount	(A) or (D)	Price
Common Stock	05/27/2026		P		88,453(1)	A	$4.07	24,233,249	I	By Mstone Partners Healthcare Limited(2)

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security (Instr. 3)	2. Conversion or Exercise Price of Derivative Security	3. Transaction Date (Month/Day/Year)	3A. Deemed Execution Date, if any (Month/Day/Year)	4. Transaction Code (Instr. 8)		5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5)		6. Date Exercisable and Expiration Date (Month/Day/Year)		7. Title and Amount of Securities Underlying Derivative Security (Instr. 3 and 4)		8. Price of Derivative Security (Instr. 5)	9. Number of derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4)	10. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	11. Nature of Indirect Beneficial Ownership (Instr. 4)
				Code	V	(A)	(D)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares

1. Name and Address of Reporting Person^*

Yang Alex Keun Mo

(Last) (First) (Middle)

SOUTH TOWER, 140 E RIDGEWOOD AVENUE,

SUITE 415

(Street)

PARAMUS NEW JERSEY 07652

(City) (State) (Zip)

UNITED STATES

(Country)

Relationship of Reporting Person(s) to Issuer

X	Director	X	10% Owner
X	Officer (give title below)		Other (specify below)
	Chief Executive Officer

1. Name and Address of Reporting Person^*

Mstone Partners Healthcare Ltd

(Last) (First) (Middle)

7/F, 80 GLOUCESTER ROAD

(Street)

WANCHAI

(City) (State) (Zip)

HONG KONG

(Country)

Relationship of Reporting Person(s) to Issuer

X	Director	X	10% Owner
	Officer (give title below)		Other (specify below)

Explanation of Responses:

1. As disclosed in the Issuer's Form 8-K filed with the Securities and Exchange Commission on May 28, 2026, MStone Partners Healthcare Limited ("Mstone") purchased 88,453 shares of common stock in a private placement transaction, for gross proceeds to the Issuer of $360,000.

2. 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.

	/s/ Alex Keun Mo Yang	05/28/2026
	/s/ Alex Keun Mo Yang, Chief Executive Officer of Mstone Partners Healthcare Limited.	05/28/2026
	** Signature of Reporting Person	Date
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
* If the form is filed by more than one reporting person, see Instruction 4 (b)(v).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.
Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB Number.
* Form 4: SEC 1474 (03-26)

FAQ

What insider-related transaction did Polaryx Therapeutics (PLYX) report on this Form 4?

Polaryx reported that MStone Partners Healthcare Limited bought 88,453 common shares. The purchase was part of a private placement, classified as an open-market or private transaction, and increased MStone’s total indirect holdings to 24,233,249 shares of Polaryx common stock.

How much stock did MStone Partners Healthcare Limited buy in Polaryx (PLYX)?

MStone Partners Healthcare Limited purchased 88,453 shares of Polaryx common stock. The shares were acquired in a private placement at $4.07 per share, and the transaction is recorded as an open-market or private purchase in the Form 4 insider filing.

What cash did Polaryx Therapeutics (PLYX) receive from this insider-related share purchase?

Polaryx received gross proceeds of $360,000 from the private placement. MStone Partners Healthcare Limited bought 88,453 common shares, and the company’s Form 4 footnote states these proceeds flowed to Polaryx as part of the private placement transaction.

What are MStone’s total Polaryx (PLYX) holdings after this Form 4 transaction?

After the transaction, MStone Partners Healthcare Limited held 24,233,249 shares of Polaryx common stock indirectly. This figure reflects the updated position reported in the Form 4 and provides context for the scale of MStone’s ownership stake in the company.

What is CEO Alex Keun Mo Yang’s relationship to MStone in the Polaryx (PLYX) filing?

Alex Keun Mo Yang is the founder and Chief Executive Officer of MStone Partners Healthcare Limited. In the Form 4 footnote, he disclaims beneficial ownership of the reported securities, except to the extent of his pecuniary interest, clarifying how his economic exposure is viewed legally.

Was the Polaryx (PLYX) insider-related share purchase made under a Rule 10b5-1 plan?

The Form 4 footnotes do not state that the transaction occurred under a Rule 10b5-1 trading plan. Instead, they describe a private placement where MStone purchased 88,453 shares for $360,000 in gross proceeds, implying a discretionary capital-raising transaction for Polaryx.