Was the Definium (DFTX) CEO’s share sale under a Rule 10b5-1 plan?

Yes. The footnote explains the transactions were executed pursuant to sell-to-cover elections under a Rule 10b5-1 plan adopted on June 15, 2022. Such pre-arranged trading plans automate sales for specific purposes like tax withholding on equity compensation.

Definium (DFTX) CEO sells 29,208 shares to cover RSU tax obligations

Filing Impact

(Very High)

Filing Sentiment

(Negative)

Form Type

Rhea-AI Filing Summary

Definium Therapeutics, Inc. Chief Executive Officer Robert Barrow sold 29,208 Common Shares at $45.03 per share on June 25, 2026. According to the disclosure, these shares were sold to satisfy withholding tax obligations tied to vested restricted stock units under a sell-to-cover election in a Rule 10b5-1 plan. Following this tax-related transaction, Barrow directly holds 1,098,246 Common Shares.

Insider Trade Summary 10b5-1

Net Seller: 29,208 shares ($1,315,236)

Net Sell 1 txn

Insider Barrow Robert

Role Chief Executive Officer

Sold 29,208 shs ($1.32M)

Type	Security	Shares	Price	Value
Sale	Common Shares	29,208	$45.03	$1.32M

Holdings After Transaction: Common Shares — 1,098,246 shares (Direct, null)

Footnotes (1)

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Key Figures

Shares sold: 29,208 shares Sale price per share: $45.03 per share Shares held after transaction: 1,098,246 shares +2 more

5 metrics

Shares sold 29,208 shares Common Shares sold on June 25, 2026

Sale price per share $45.03 per share Average price for Common Shares sold

Shares held after transaction 1,098,246 shares Direct Common Share ownership after sale

Net shares sold 29,208 shares Net-sell direction per transaction summary

Transaction date June 25, 2026 Date of Common Share sale

Key Terms

restricted stock units, Rule 10b5-1 plan, sell-to-cover elections, withholding tax obligations, +1 more

5 terms

restricted stock units financial

"in connection with the settlement of vested restricted stock units, pursuant to sell-to-cover elections"

Restricted stock units are a type of company reward where employees are promised shares of stock, but they only fully own these shares after meeting certain conditions, like staying with the company for a set time. They matter because they can become valuable assets and are often used to motivate employees to help the company succeed.

Rule 10b5-1 plan regulatory

"pursuant to sell-to-cover elections 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.

sell-to-cover elections financial

"sold to satisfy withholding tax obligations in connection with the settlement of vested restricted stock units, pursuant to sell-to-cover elections"

withholding tax obligations financial

"sold to satisfy withholding tax obligations in connection with the settlement of vested restricted stock units"

open-market sale financial

"transaction_action": "open-market sale", "transaction_code_description": "Sale in open market or private transaction""

An open-market sale is when a shareholder sells existing shares directly on a public exchange to any willing buyer, rather than through a private deal. Think of it like putting goods on a busy market stall where price is set by supply and demand; for investors it matters because such sales increase available supply, can put short-term downward pressure on the stock price, and signal changes in liquidity or investor confidence.

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Form 4 Insider Transactions: What Each Field Means →

Available on EDGAR 06/26/2026 - 04:30 PM Accepted by SEC EDGAR 06/26/2026 - 04:30 PM

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^*

Barrow Robert

(Last)

(First)

(Middle)

C/O DEFINIUM THERAPEUTICS, INC.

ONE WORLD TRADE CENTER, SUITE 8500

(Street)

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)
06/25/2026

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)
1. Title of Security (Instr. 3)	2. Transaction Date (Month/Day/Year)	2A. Deemed Execution Date, if any (Month/Day/Year)	Code	V	Amount	(A) or (D)	Price		6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	7. Nature of Indirect Beneficial Ownership (Instr. 4)
Common Shares	06/25/2026		S⁽¹⁾		29,208	D	$45.03	1,098,246	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)
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)	Code	V	(A)	(D)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares	8. Price of Derivative Security (Instr. 5)		10. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	11. Nature of Indirect Beneficial Ownership (Instr. 4)

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.

	/s/ Mark Sullivan, Attorney-in-Fact for Robert Barrow	06/26/2026
	** 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)

Source: View Original Filing on SEC EDGAR

FAQ

What did Definium (DFTX) CEO Robert Barrow report in this Form 4?

Robert Barrow reported selling 29,208 Common Shares of Definium Therapeutics. The sale was used to cover withholding taxes from vested restricted stock units, executed under a pre-arranged Rule 10b5-1 sell-to-cover plan rather than a discretionary open-market trade.

How many Definium (DFTX) shares did the CEO sell and at what price?

The CEO sold 29,208 Common Shares at an average price of $45.03 per share. These sales were specifically designated to satisfy tax withholding obligations related to restricted stock unit vesting, rather than representing an ordinary portfolio reallocation or directional bet.

Why were Definium (DFTX) shares sold according to this filing?

The filing states the shares were sold to satisfy withholding tax obligations from vested restricted stock units. The sales occurred under sell-to-cover elections within a Rule 10b5-1 plan, indicating a structured, compensation-related transaction rather than a purely discretionary market sale.

How many Definium (DFTX) shares does the CEO hold after the transaction?

After the tax-related sale, Robert Barrow directly owns 1,098,246 Common Shares of Definium Therapeutics. This post-transaction figure shows he retains a substantial equity position in the company despite selling shares to meet tax obligations tied to restricted stock unit vesting.