Janus Henderson Group (MIRM) reports 5.9M Mirum Pharma shares under management

Rhea-AI Filing Summary

Janus Henderson Group Ltd., a Jersey-organized asset management group, reports beneficial ownership in Mirum Pharmaceuticals, Inc. common stock. Through its various investment adviser subsidiaries managing client accounts referred to as Managed Portfolios, it may be deemed to beneficially own 5,909,184 shares of Mirum common stock, representing 9.7% of the class as of June 30, 2026. Janus Henderson has no sole voting or dispositive power over these shares but holds shared voting and shared dispositive power over all 5,909,184 shares. The Managed Portfolios, not Janus Henderson or its parent owners, have the right to receive all dividends and sale proceeds, and no single Managed Portfolio holds more than five percent of Mirum’s common stock.

Key Figures

Shares beneficially owned: 5,909,184 shares Percent of class: 9.7% Sole voting power: 0 shares +3 more

6 metrics

Shares beneficially owned 5,909,184 shares Common stock of Mirum Pharmaceuticals, Inc. beneficially owned via Managed Portfolios

Percent of class 9.7% Portion of Mirum Pharmaceuticals common stock class attributed to Janus Henderson

Sole voting power 0 shares Shares of Mirum common stock over which Janus Henderson has sole voting power

Shared voting power 5,909,184 shares Shares of Mirum common stock over which Janus Henderson has shared voting power

Sole dispositive power 0 shares Shares of Mirum common stock over which Janus Henderson has sole dispositive power

Shared dispositive power 5,909,184 shares Shares of Mirum common stock over which Janus Henderson has shared dispositive power

Key Terms

beneficial owner, dispositive power, Managed Portfolios, parent holding company, +1 more

5 terms

beneficial owner financial

"may be deemed to be the beneficial owner of 5,909,184 common stock"

A beneficial owner is the person who ultimately owns or controls a financial asset or property, even if their name isn't directly on official documents. Think of it like someone who secretly holds the keys to a safe deposit box—others may appear to have access, but the true owner is the one who benefits from what's inside. Identifying beneficial owners helps ensure transparency and prevent illegal activities like money laundering or fraud.

dispositive power financial

"Shared Dispositive Power 5,909,184.00"

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.

Managed Portfolios financial

"collectively referred to herein as Managed Portfolios"

parent holding company financial

"If a parent holding company has filed this schedule"

Schedule 13G financial

"If a parent holding company has filed this schedule, pursuant to (ii)(G)"

A Schedule 13G is a formal document that investors file with the government when they acquire a large ownership stake in a company, usually for investment purposes rather than control. It helps keep the public informed about who owns significant parts of a company's shares, which can influence how the company is managed and how investors make decisions. Filing this schedule is important for transparency and understanding the ownership landscape of publicly traded companies.

FAQ

What percentage of Mirum Pharmaceuticals (MIRM) does Janus Henderson Group Ltd. report owning?

Janus Henderson Group Ltd. reports beneficial ownership of 9.7% of Mirum Pharmaceuticals’ common stock. This ownership is held through various Managed Portfolios for which its asset manager subsidiaries exercise investment and/or voting discretion on behalf of clients.

How many Mirum Pharmaceuticals (MIRM) shares does Janus Henderson Group Ltd. beneficially own?

Janus Henderson Group Ltd. may be deemed to beneficially own 5,909,184 shares of Mirum Pharmaceuticals common stock. These shares are held in client accounts (Managed Portfolios) managed by its investment adviser subsidiaries, which exercise investment and/or voting discretion.

Does Janus Henderson have sole or shared voting power over its Mirum (MIRM) shares?

Janus Henderson reports 0 shares with sole voting power and 5,909,184 shares with shared voting power. Its asset manager subsidiaries share voting authority through their discretion over the Managed Portfolios holding Mirum shares.

Who receives dividends and sale proceeds from the Mirum (MIRM) shares managed by Janus Henderson?

All dividends and sale proceeds from the Mirum shares are received by the respective Managed Portfolios. Janus Henderson and its asset managers expressly disclaim ownership of these economic rights, which belong to their underlying clients.

Do any individual Managed Portfolios hold more than 5% of Mirum Pharmaceuticals (MIRM)?

No individual Managed Portfolio holds more than 5% of Mirum Pharmaceuticals’ common stock. The reported 9.7% beneficial ownership reflects aggregate holdings across multiple client accounts managed by Janus Henderson’s asset manager subsidiaries.

What type of securities of Mirum Pharmaceuticals (MIRM) are covered in this ownership report?

The report covers Mirum Pharmaceuticals’ Common Stock with CUSIP 604749101. Janus Henderson’s beneficial ownership arises through shares of this class held in various client accounts managed by its investment adviser subsidiaries.

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Available on EDGAR 08/13/2026 - 12:48 PM Accepted by SEC EDGAR 08/13/2026 - 12:47 PM Learn about SEC filing dates

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13G

UNDER THE SECURITIES EXCHANGE ACT OF 1934

(Amendment No. 10)

MIRUM PHARAMACEUTICALS, INC.

(Name of Issuer)

Common Stock

(Title of Class of Securities)

604749101

(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): 604749101

1

Names of Reporting Persons

JANUS HENDERSON GROUP Ltd.

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

JERSEY

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 0.00
6	Shared Voting Power 5,909,184.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 5,909,184.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

5,909,184.00

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)

9.7 %

12

Type of Reporting Person (See Instructions)

HC

SCHEDULE 13G

Item 1.
(a)	Name of issuer: MIRUM PHARAMACEUTICALS, INC.
(b)	Address of issuer's principal executive offices: 989 EAST HILLSDALE BOULEVARD, SUITE 300 FOSTER CITY, CA 94404
Item 2.
(a)	Name of person filing: Janus Henderson Group Ltd. In accordance with SEC Release No. 34-39538 (January 12, 1998), this Schedule 13G reflects the securities beneficially owned, or deemed to be beneficially owned, by Janus Henderson Group Ltd. It does not include securities, if any, beneficially owned by Janus Henderson Group Ltd.s ultimate parent Jupiter Topco LLC, the direct or indirect owners of Jupiter Topco LLC, or other persons that may be deemed under control of such owners. Any beneficial ownership by such persons has been disaggregated from that of Janus Henderson Group Ltd. in accordance with the release.
(b)	Address or principal business office or, if none, residence: 201 Bishopsgate EC2M 3AE, United Kingdom
(c)	Citizenship: Y9
(d)	Title of class of securities: Common Stock
(e)	CUSIP No.: 604749101
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: Janus Henderson Group Ltd. (JHG) is the ultimate parent of a number of SEC-registered investment advisers and foreign equivalents thereof, including but not limited to Janus Henderson Investors US LLC, Janus Henderson Investors UK Limited, Janus Henderson Investors Australia Institutional Funds Management Limited, Janus Henderson Investors Middle East Limited, Janus Henderson Investors (Jersey) Limited, Janus Henderson Investors (Japan) Limited, Janus Henderson Investors (Singapore) Limited, Kapstream Capital Pty Limited, Privacore Capital Advisors LLC, Tabula Investment Management Limited, Victory Park Capital Advisors LLC, and Richard Berstein Advisors LLC (each, an Asset Manager and together, the Asset Managers). The Asset Managers generally exercise investment and/or voting discretion on behalf of their clients which include investment companies, other investment advisers, institutional separate accounts and retail separate accounts (collectively referred to herein as Managed Portfolios). As a result of their exercise of investment and/or voting discretion on behalf of the Managed Portfolios, the Asset Managers may be deemed to be the beneficial owner of 5,909,184 common stock of Mirum Pharmaceuticals, Inc. However, the Asset Managers do not have the right to receive any dividends from, or the proceeds from the sale of, the securities held in the Managed Portfolios and disclaim any ownership associated with such rights.
(b)	Percent of class: 9.7 %
(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: 5909184
	(iii) Sole power to dispose or to direct the disposition of: 0
	(iv) Shared power to dispose or to direct the disposition of: 5909184
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 Managed Portfolios have the right to receive all dividends from, and the proceeds from the sale of, the securities held in their respective accounts. Of the Managed Portfolios, none own more than five percent of the common stock of Mirum Pharmaceuticals, Inc.
Item 7.	Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on by the Parent Holding Company or Control Person.
	If a parent holding company has filed this schedule, pursuant to Rule 13d-1(b)(ii)(G), so indicate under Item 3(g) and attach an exhibit stating the identity and the Item 3 classification of the relevant subsidiary. If a parent holding company has filed this schedule pursuant to Rule 13d-1(c) or Rule 13d-1(d), attach an exhibit stating the identification of the relevant subsidiary. Please refer to Exhibit 99.
Item 8.	Identification and Classification of Members of the Group.
	If a group has filed this schedule pursuant to §240.13d-1(b)(1)(ii)(J), so indicate under Item 3(j) and attach an exhibit stating the identity and Item 3 classification of each member of the group. If a group has filed this schedule pursuant to §240.13d-1(c) or §240.13d-1(d), attach an exhibit stating the identity of each member of the group. N/A
Item 9.	Notice of Dissolution of Group.
	Notice of dissolution of a group may be furnished as an exhibit stating the date of the dissolution and that all further filings with respect to transactions in the security reported on will be filed, if required, by members of the group, in their individual capacity. See Item 5. N/A

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.

JANUS HENDERSON GROUP Ltd.

Signature:	Kristin Mariani
Name/Title:	Head of North America Compliance
Date:	08/13/2026

Exhibit Information

Exhibit 24: Power of Attorney Exhibit 99: Item 7