Ultragenyx (RARE): RTW Investments and Roderick Wong report 7.9% stake

Rhea-AI Filing Summary

RTW Investments, LP, as investment adviser to certain funds, and Roderick Wong, M.D. report beneficial ownership of Ultragenyx Pharmaceutical Inc. common stock. They report 7,796,895 Shares of common stock, representing 7.9% of the class, based on 98,489,224 Shares outstanding as of May 1, 2026.

Both RTW Investments and Dr. Wong report 0 Shares with sole voting or dispositive power and 7,796,895 Shares with shared voting and shared dispositive power. The RTW funds have the right to receive dividends and sale proceeds on these Shares. The reporting persons state that the filing is not an admission of beneficial ownership for Section 13 purposes.

Key Figures

Shares beneficially owned: 7,796,895 Shares Percent of class: 7.9% Shares outstanding: 98,489,224 Shares +2 more

5 metrics

Shares beneficially owned 7,796,895 Shares Ultragenyx common stock reported by RTW Investments and Dr. Wong

Percent of class 7.9% Ownership percentage of Ultragenyx common stock reported by each Reporting Person

Shares outstanding 98,489,224 Shares Ultragenyx Shares outstanding as of May 1, 2026 used for percentage calculation

Shared voting power 7,796,895 Shares Shares over which RTW Investments and Dr. Wong share voting power

Shared dispositive power 7,796,895 Shares Shares over which RTW Investments and Dr. Wong share dispositive power

Key Terms

beneficial owner, shared voting power, shared dispositive power, investment adviser, +1 more

5 terms

beneficial owner regulatory

"not be construed as an admission that any Reporting Person is, for the purposes of Section 13, the beneficial owner"

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.

shared voting power regulatory

"Shared Voting Power 7,796,895.00"

Shared voting power occurs when two or more parties jointly have the right to vote or decide how a block of company shares is cast, like co-owners who must agree before moving a piece of furniture. Investors care because who controls voting rights affects board elections, major corporate decisions and takeover outcomes, and shared control can alter regulatory disclosures and the practical influence any holder has over a company’s direction and value.

shared dispositive power regulatory

"Shared Dispositive Power 7,796,895.00"

investment adviser financial

"RTW Investments, LP, a Delaware limited partnership and the investment adviser to certain funds"

An investment adviser is a person or firm that professionally manages money and gives recommendations about buying, selling, or holding investments. Like a financial coach or guide, they have a legal duty to act in a client's best financial interest, so their advice, fees and potential conflicts can directly affect returns and risk — making their role important for investors who want informed, accountable help with portfolios.

Schedule 13G regulatory

"form_type: "SCHEDULE 13G""

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 Ultragenyx (RARE) does RTW Investments report owning?

RTW Investments and Dr. Roderick Wong report beneficial ownership of 7.9% of Ultragenyx Pharmaceutical Inc. common stock, representing 7,796,895 Shares out of 98,489,224 Shares outstanding as of May 1, 2026.

How many Ultragenyx (RARE) shares are reported as beneficially owned by RTW-related entities?

RTW Investments and Dr. Roderick Wong report beneficial ownership of 7,796,895 Shares of Ultragenyx common stock, held by funds advised by RTW Investments, representing 7.9% of the outstanding Shares as of May 1, 2026.

Who holds voting and dispositive power over the Ultragenyx (RARE) shares reported by RTW?

RTW Investments and Dr. Wong each report 0 Shares with sole voting or dispositive power and 7,796,895 Shares with shared voting and shared dispositive power, relating to Shares held by RTW-advised funds.

What is the Ultragenyx (RARE) share count used to calculate RTW’s 7.9% stake?

The reported 7.9% ownership is calculated using 98,489,224 Ultragenyx Shares outstanding as of May 1, 2026, as referenced from the company’s Quarterly Report on Form 10-Q filed on May 6, 2026.

Do RTW’s funds receive dividends and sale proceeds on the Ultragenyx (RARE) shares?

Yes. The RTW funds have the right to receive or direct receipt of dividends and sale proceeds from the 7,796,895 Shares of Ultragenyx common stock reported as beneficially owned.

Does Dr. Roderick Wong personally own the reported Ultragenyx (RARE) shares?

The Shares are directly held by RTW-advised funds; Dr. Wong is Managing Partner and CIO of RTW Investments. The reporting persons state that the report should not be construed as an admission of beneficial ownership for Section 13 purposes.

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

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Available on EDGAR 08/14/2026 - 08:16 AM Accepted by SEC EDGAR 08/14/2026 - 08:15 AM Learn about SEC filing dates

SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

SCHEDULE 13G

UNDER THE SECURITIES EXCHANGE ACT OF 1934

Ultragenyx Pharmaceutical Inc.

(Name of Issuer)

Common Stock, $0.001 par value

(Title of Class of Securities)

90400D108

(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): 90400D108

1

Names of Reporting Persons

RTW Investments, LP

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 7,796,895.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 7,796,895.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

7,796,895.00

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)

7.9 %

12

Type of Reporting Person (See Instructions)

IA, PN

SCHEDULE 13G

CUSIP Number(s): 90400D108

1

Names of Reporting Persons

Roderick Wong

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

UNITED STATES

Number of Shares Beneficially Owned by Each Reporting Person With:

5	Sole Voting Power 0.00
6	Shared Voting Power 7,796,895.00
7	Sole Dispositive Power 0.00
8	Shared Dispositive Power 7,796,895.00

9

Aggregate Amount Beneficially Owned by Each Reporting Person

7,796,895.00

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)

7.9 %

12

Type of Reporting Person (See Instructions)

HC, IN

SCHEDULE 13G

Item 1.
(a)	Name of issuer: Ultragenyx Pharmaceutical Inc.
(b)	Address of issuer's principal executive offices: 60 Leveroni Court, Novato, CA, 94949.
Item 2.
(a)	Name of person filing: This statement is filed by: (i) RTW Investments, LP ("RTW Investments"), a Delaware limited partnership and the investment adviser to certain funds (the "RTW Funds"), with respect to shares of Common Stock, par value $0.001 per share (the "Shares") of Ultragenyx Pharmaceutical Inc. (the "Company") directly held by the RTW Funds; and (ii) Roderick Wong, M.D. ("Dr. Wong"), the Managing Partner and Chief Investment Officer of RTW Investments, with respect to the Shares directly held by the RTW Funds. The foregoing persons are hereinafter sometimes collectively referred to as the "Reporting Persons." The filing of this statement should not be construed as an admission that any of the foregoing persons or any Reporting Person is, for the purposes of Section 13 of the Securities Exchange Act of 1934, as amended, the beneficial owner of the Shares reported herein.
(b)	Address or principal business office or, if none, residence: The address of the business office of each of the Reporting Persons is 40 10th Avenue, Floor 7, New York, New York 10014.
(c)	Citizenship: RTW Investments is a Delaware limited partnership. Dr. Wong is a citizen of the United States.
(d)	Title of class of securities: Common Stock, $0.001 par value
(e)	CUSIP Number(s): 90400D108
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: The information required by Item 4(a) is set forth in Rows 5 - 9 of the cover page for each of the Reporting Persons and is incorporated herein by reference. The percentages set forth in Row 11 of the cover pages are calculated based upon 98,489,224 Shares outstanding as of May 1, 2026 as reported in the Company's Quarterly Report on Form 10-Q filed with the Securities and Exchange Commission on May 6, 2026.
(b)	Percent of class: RTW Investments: 7.9% Dr. Wong: 7.9%
(c)	Number of shares as to which the person has:
	(i) Sole power to vote or to direct the vote: RTW Investments: 0 Dr. Wong: 0
	(ii) Shared power to vote or to direct the vote: RTW Investments: 7,796,895 Shares Dr. Wong: 7,796,895 Shares
	(iii) Sole power to dispose or to direct the disposition of: RTW Investments: 0 Dr. Wong: 0
	(iv) Shared power to dispose or to direct the disposition of: RTW Investments: 7,796,895 Shares Dr. Wong: 7,796,895 Shares
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. See Item 2. The RTW Funds have the right to receive or the power to direct the receipt of dividends from, or the proceeds from the sale of, the Shares reported herein.
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.

RTW Investments, LP

Signature:	/s/ Roderick Wong, M.D.
Name/Title:	Roderick Wong, M.D., Managing Partner
Date:	08/14/2026

Roderick Wong

Signature:	/s/ Roderick Wong, M.D.
Name/Title:	Roderick Wong, M.D.
Date:	08/14/2026

Exhibit Information

Exhibit 99.1 Joint Filing Agreement