Driehaus Capital discloses 6.64% stake in Definium Therapeutics (DFTX)

Rhea-AI Filing Summary

Driehaus Capital Management LLC, a Delaware investment adviser, reported beneficial ownership of Definium Therapeutics, Inc. common stock. Driehaus has shared voting and dispositive power over 6,537,202 shares, representing 6.64% of the company’s common stock as of the event date.

The shares are held in numerous fully discretionary client accounts managed by Driehaus, which reports potential voting and dispositive power, while clients generally do not hold more than 5% of the class individually. Driehaus states the holdings are maintained in the ordinary course of business and not for the purpose of changing or influencing control of Definium Therapeutics.

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13G

UNDER THE SECURITIES EXCHANGE ACT OF 1934

Definium Therapeutics, Inc.

(Name of Issuer)

Common Stock

(Title of Class of Securities)

24477V105

(CUSIP Number)

12/31/2025

(Date of Event Which Requires Filing of this Statement)

Check the appropriate box to designate the rule pursuant to which this Schedule is filed:

Rule 13d-1(b)

Rule 13d-1(c)

Rule 13d-1(d)

SCHEDULE 13G

CUSIP No. 24477V105

1

Names of Reporting Persons

DRIEHAUS CAPITAL MANAGEMENT LLC

2

Check the appropriate box if a member of a Group (see instructions)

(a)
(b)

3

Sec Use Only

4

Citizenship or Place of Organization

DELAWARE

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 0.00
6	Shared Voting Power 6,537,202.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 6,537,202.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

6,537,202.00

10

Check box if the aggregate amount in row (9) excludes certain shares (See Instructions)

11

Percent of class represented by amount in row (9)

6.64 %

12

Type of Reporting Person (See Instructions)

IA

Comment for Type of Reporting Person: The issuer changed its name from Mind Medicine (MindMed), Inc. to Definium Therapeutics, Inc. on January 12, 2026.

SCHEDULE 13G

Item 1.
(a)	Name of issuer: Definium Therapeutics, Inc.
(b)	Address of issuer's principal executive offices: One World Trade Center, Suite 8500, New York, New York, 10007
Item 2.
(a)	Name of person filing: Driehaus Capital Management LLC
(b)	Address or principal business office or, if none, residence: 25 East Erie Street, Chicago, Illinois 60611
(c)	Citizenship: USA
(d)	Title of class of securities: Common Stock
(e)	CUSIP No.: 24477V105
Item 3.	If this statement is filed pursuant to §§ 240.13d-1(b) or 240.13d-2(b) or (c), check whether the person filing is a:
(a)	Broker or dealer registered under section 15 of the Act (15 U.S.C. 78o);
(b)	Bank as defined in section 3(a)(6) of the Act (15 U.S.C. 78c);
(c)	Insurance company as defined in section 3(a)(19) of the Act (15 U.S.C. 78c);
(d)	Investment company registered under section 8 of the Investment Company Act of 1940 (15 U.S.C. 80a-8);
(e)	An investment adviser in accordance with § 240.13d-1(b)(1)(ii)(E);
(f)	An employee benefit plan or endowment fund in accordance with § 240.13d-1(b)(1)(ii)(F);
(g)	A parent holding company or control person in accordance with § 240.13d-1(b)(1)(ii)(G);
(h)	A savings associations as defined in Section 3(b) of the Federal Deposit Insurance Act (12 U.S.C. 1813);
(i)	A church plan that is excluded from the definition of an investment company under section 3(c)(14) of the Investment Company Act of 1940 (15 U.S.C. 80a-3);
(j)	A non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J). If filing as a non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J), please specify the type of institution:
(k)	Group, in accordance with Rule 240.13d-1(b)(1)(ii)(K).
Item 4.	Ownership
(a)	Amount beneficially owned: 6537202
(b)	Percent of class: 6.64 %
(c)	Number of shares as to which the person has:
	(i) Sole power to vote or to direct the vote: 0
	(ii) Shared power to vote or to direct the vote: 6537202
	(iii) Sole power to dispose or to direct the disposition of: 0
	(iv) Shared power to dispose or to direct the disposition of: 6537202
Item 5.	Ownership of 5 Percent or Less of a Class.
	Not Applicable
Item 6.	Ownership of more than 5 Percent on Behalf of Another Person.
	If any other person is known to have the right to receive or the power to direct the receipt of dividends from, or the proceeds from the sale of, such securities, a statement to that effect should be included in response to this item and, if such interest relates to more than 5 percent of the class, such person should be identified. A listing of the shareholders of an investment company registered under the Investment Company Act of 1940 or the beneficiaries of employee benefit plan, pension fund or endowment fund is not required. The shares reported by Driehaus Capital Management LLC (DCM) are held by numerous clients on a fully discretionary basis in accounts managed by DCM. Securities held in these clients' accounts are included in this report to reflect that DCM may have voting power and has dispositive power. To the best of DCM's knowledge, none of the referenced clients have the right to receive dividends or direct proceeds from the sale of interests relating to more than 5% of the class.
Item 7.	Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on by the Parent Holding Company or Control Person.
	Not Applicable
Item 8.	Identification and Classification of Members of the Group.
	Not Applicable
Item 9.	Notice of Dissolution of Group.
	Not Applicable

Item 10.

Certifications:

By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were acquired and are held in the ordinary course of business and were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect, other than activities solely in connection with a nomination under ?? 240.14a-11.

SIGNATURE

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.

DRIEHAUS CAPITAL MANAGEMENT LLC

Signature:	Janet McWilliams
Name/Title:	Janet McWilliams/General Counsel
Date:	02/17/2026

FAQ

What percentage of Definium Therapeutics (DFTX) does Driehaus Capital Management own?

Driehaus Capital Management reports beneficial ownership of 6.64% of Definium Therapeutics’ common stock. This corresponds to 6,537,202 shares over which it has shared voting and dispositive power through client accounts it manages on a fully discretionary basis.

How many Definium Therapeutics (DFTX) shares are beneficially owned by Driehaus Capital Management?

Driehaus Capital Management reports beneficial ownership of 6,537,202 shares of Definium Therapeutics common stock. These shares are held across numerous discretionary client accounts for which Driehaus may exercise voting and dispositive power, resulting in an aggregate 6.64% stake in the company.

Does Driehaus Capital Management seek to influence control of Definium Therapeutics (DFTX)?

Driehaus Capital Management states the securities were acquired and are held in the ordinary course of business. It certifies they were not acquired for the purpose of changing or influencing control of Definium Therapeutics and are not held in connection with any such control-related transaction.

In whose accounts are the Definium Therapeutics (DFTX) shares held for Driehaus?

The Definium Therapeutics shares reported by Driehaus are held in numerous client accounts managed on a fully discretionary basis. Driehaus includes these securities because it may have voting and dispositive power, while no individual client is known to hold more than 5% of the class.

What voting and dispositive powers does Driehaus have over Definium Therapeutics (DFTX) shares?

Driehaus Capital Management reports zero sole voting and dispositive power, and 6,537,202 shares of shared voting and shared dispositive power. This reflects its authority, as investment adviser, over securities held in client accounts it manages.

When was Driehaus’s Definium Therapeutics (DFTX) ownership position measured?

The reported beneficial ownership position of Driehaus in Definium Therapeutics is tied to an event date of December 31, 2025. As of that date, Driehaus held shared voting and dispositive power over 6,537,202 common shares, representing 6.64% of the outstanding class.

What name change related to Definium Therapeutics (DFTX) is disclosed?

The document notes that the issuer changed its name from Mind Medicine (MindMed), Inc. to Definium Therapeutics, Inc. on January 12, 2026. The Schedule 13G ownership information therefore relates to the issuer under its current Definium Therapeutics name.