Driehaus reports 5.36% stake in Definium Therapeutics

Rhea-AI Filing Summary

Definium Therapeutics, Inc. has a significant shareholder, Driehaus Capital Management LLC (DCM), which reported ownership of 6,845,276 shares of Definium common stock on a Schedule 13G/A. This position represented 5.36% of the outstanding common stock as of June 30, 2026.

DCM stated that its percentage interest was 5.36% as of June 30, 2026, compared with 6.64% as of December 31, 2025. All reported shares are held in numerous client accounts managed by DCM on a fully discretionary basis. DCM reported shared voting power and shared dispositive power over 6,845,276 shares, with no sole voting or dispositive power. The issuer changed its name from Mind Medicine (MindMed), Inc. to Definium Therapeutics, Inc. on January 12, 2026.

Key Figures

Shares beneficially owned: 6,845,276 shares Ownership percentage as of June 30, 2026: 5.36% Prior ownership percentage: 6.64% +2 more

5 metrics

Shares beneficially owned 6,845,276 shares Common stock beneficially owned by Driehaus Capital Management LLC

Ownership percentage as of June 30, 2026 5.36% Percent of Definium Therapeutics common stock class held by DCM

Prior ownership percentage 6.64% Percentage of the class owned as of December 31, 2025

Shared voting power 6,845,276 shares Shares over which DCM reported shared voting power

Shared dispositive power 6,845,276 shares Shares over which DCM reported shared dispositive power

Key Terms

beneficially owned, dispositive power, fully discretionary basis, CUSIP No.

4 terms

beneficially owned financial

"Item 4. | Ownership (a) | Amount beneficially owned: 6845276"

Beneficially owned describes securities or assets where a person has the economic rights and control—such as the right to receive dividends and to direct voting—even if legal title is held in another name. Think of it like having the keys and using a car that’s registered to someone else: you get the benefits and make decisions. Investors care because beneficial ownership reveals who truly controls value and voting power, affecting corporate decisions and takeover dynamics.

dispositive power financial

"Sole power to dispose or to direct the disposition of: 0 | (iv) Shared power to dispose or to direct the disposition of: 6845276"

Dispositive power is the authority to decide the final outcome of an asset, legal claim, contract, or corporate action — in effect the power to dispose of or resolve something. For investors it matters because whoever holds that authority can determine who gets paid, who controls an asset or vote, and how risks and returns are allocated; think of it like holding the key that lets you lock in the winner or loser in a deal.

fully discretionary basis financial

"held by numerous clients on a fully discretionary basis in accounts managed by DCM"

CUSIP No. financial

"(e) | CUSIP No.: 24477V105"

FAQ

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

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

Driehaus Capital Management LLC reported owning 5.36% of Definium Therapeutics, Inc.’s common stock as of June 30, 2026, corresponding to 6,845,276 shares held across client accounts.

How has Driehaus Capital Management’s ownership in DFTX changed over time?

Driehaus Capital Management reported a 5.36% stake in DFTX as of June 30, 2026, compared with 6.64% as of December 31, 2025, indicating a lower percentage of the company’s outstanding common stock.

Does Driehaus Capital Management have voting control over its Definium Therapeutics (DFTX) shares?

Driehaus Capital Management reported shared voting power and shared dispositive power over 6,845,276 DFTX shares, with no sole voting or dispositive power over any shares of Definium common stock.

Who actually holds the Definium Therapeutics (DFTX) shares reported by Driehaus Capital Management?

The DFTX shares are held in numerous client accounts managed by Driehaus Capital Management on a fully discretionary basis. To DCM’s knowledge, no individual client has more than 5% of the class.

Did Definium Therapeutics (DFTX) recently change its name?

Yes. The issuer’s name changed from Mind Medicine (MindMed), Inc. to Definium Therapeutics, Inc. on January 12, 2026, and the Schedule 13G/A reflects this updated corporate name.

What class of securities in Definium Therapeutics (DFTX) is Driehaus Capital Management reporting on?

Driehaus Capital Management’s Schedule 13G/A filing relates to Common Stock of Definium Therapeutics, Inc., identified by CUSIP 24477V105, held across the firm’s discretionary client accounts.

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

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Available on EDGAR 08/14/2026 - 07:35 AM Accepted by SEC EDGAR 08/14/2026 - 07:34 AM Learn about SEC filing dates

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13G

UNDER THE SECURITIES EXCHANGE ACT OF 1934

(Amendment No. 1)

Definium Therapeutics, Inc.

(Name of Issuer)

Common Stock

(Title of Class of Securities)

24477V105

(CUSIP Number)

06/30/2026

(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)

schemaVersion:

SCHEDULE 13G

CUSIP Number(s): 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 6,845,276.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 6,845,276.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

6,845,276.00

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)

5.36 %

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. This amendment is filed to reflect the change in our percentage of ownership of Definium Therapeutics, Inc. (DFTX). DCM owned 5.36% of DFTX as of June 30, 2026, down from 6.64% as of December 31, 2025.

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: 6845276
(b)	Percent of class: 5.36 %
(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: 6845276
	(iii) Sole power to dispose or to direct the disposition of: 0
	(iv) Shared power to dispose or to direct the disposition of: 6845276
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:	08/14/2026