Definium Therapeutics CEO sells 31,550 shares

The sale used sell-to-cover elections for withholding taxes on vested restricted stock units under a plan adopted June 15, 2022.

Rhea-AI Filing Summary

Definium Therapeutics, Inc. CEO Robert Barrow sold 31,550 Common Shares on September 25, 2026, at a weighted average price of $36.57 per share. The shares were sold through sell-to-cover elections to meet withholding tax obligations on vested restricted stock units under a Rule 10b5-1 plan adopted June 15, 2022. Prices ranged from $36.24 to $36.98 across the transactions. Barrow directly held 2,213,090 shares following the sale.

Insider Trade Summary 10b5-1

Net Seller: 31,550 shares

Net Sell 1 txn

Insider Barrow Robert

Role Chief Executive Officer

Sold 31,550 shs ($1.15M)

Type	Security	Shares	Price	Value
Sale	Common Shares F1, F2	31,550	$36.57	$1.15M

Holdings After Transaction: Common Shares — 2,213,090 shares (Direct)

Footnotes (2)

1. F1. Represents the number of Common Shares sold to satisfy withholding tax obligations in connection with the settlement of vested restricted stock units, pursuant to sell-to-cover elections under a Rule 10b5-1 plan adopted on June 15, 2022.
2. F2. The reported price is a weighted average sales price. These shares were sold in multiple transactions on September 25, 2026 at prices ranging from $36.24 to $36.98. The Reporting Person undertakes to provide the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote.

Key Figures

Common Shares sold: 31,550 shares Weighted average sales price: $36.57 per share Transaction price range: $36.24 to $36.98 per share +2 more

5 metrics

Common Shares sold 31,550 shares September 25, 2026

Weighted average sales price $36.57 per share September 25, 2026

Transaction price range $36.24 to $36.98 per share Multiple transactions on September 25, 2026

Direct shares held after sale 2,213,090 shares Following the September 25, 2026 sale

Rule 10b5-1 plan adoption date June 15, 2022 Plan associated with the sell-to-cover elections

Key Terms

sell-to-cover elections, vested restricted stock units, Rule 10b5-1 plan, weighted average sales price

4 terms

sell-to-cover elections financial

"pursuant to sell-to-cover elections"

vested restricted stock units financial

"in connection with the settlement of vested restricted stock units"

Rule 10b5-1 plan regulatory

"under a Rule 10b5-1 plan adopted on June 15, 2022"

A Rule 10b5-1 plan is a prearranged, written schedule that lets corporate insiders buy or sell company stock at set times or amounts, even if they later learn material nonpublic information. Think of it like setting an automatic thermostat for trades: it creates a clear record that trades were planned in advance, reducing the risk of insider-trading accusations and helping investors trust that insider transactions are routine rather than based on secret information.

weighted average sales price financial

"The reported price is a weighted average sales price"

FAQ

AI-generated questions and answers. How Rhea-AI works. Not financial advice.

How many DFTX shares did CEO Robert Barrow sell, and at what price?

Robert Barrow sold 31,550 Common Shares on September 25, 2026, at a weighted average of $36.57 per share. The reported sales occurred in multiple transactions at prices from $36.24 to $36.98. Following the sale, he directly held 2,213,090 shares.

AI-generated analysis. How Rhea-AI works. Not financial advice.

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Available on EDGAR 09/29/2026 - 09:14 PM Accepted by SEC EDGAR 09/29/2026 - 09:14 PM Learn about SEC filing dates

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).

X

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^*

Barrow Robert

(Last) (First) (Middle)

C/O DEFINIUM THERAPEUTICS, INC.

ONE WORLD TRADE CENTER, SUITE 8500

(Street)

NEW YORK NEW YORK 10007

(City) (State) (Zip)

UNITED STATES

(Country)

2. Issuer Name and Ticker or Trading Symbol
Definium Therapeutics, Inc. [ DFTX ]

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

X	Director		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)
09/25/2026

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

X	Form filed by One Reporting Person
	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 Shares	09/25/2026		S(1)		31,550	D	$36.57(2)	2,213,090	D

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

Explanation of Responses:

1. Represents the number of Common Shares sold to satisfy withholding tax obligations in connection with the settlement of vested restricted stock units, pursuant to sell-to-cover elections under a Rule 10b5-1 plan adopted on June 15, 2022.

2. The reported price is a weighted average sales price. These shares were sold in multiple transactions on September 25, 2026 at prices ranging from $36.24 to $36.98. The Reporting Person undertakes to provide the Issuer, any security holder of the Issuer, or the staff of the Securities and Exchange Commission, upon request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote.

	/s/ Mark Sullivan, Attorney-in-Fact for Robert Barrow	09/29/2026
	** 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)