[Form 4] Ultragenyx Pharmaceutical Inc. Insider Trading Activity

Rhea-AI Filing Summary

Theodore A. Huizenga, SVP and Chief Accounting Officer of Ultragenyx Pharmaceutical Inc. (RARE), reported a sale of company common stock on 09/05/2025. The Form 4 shows a sale (Code S) of 84 shares at $31.39 per share. After the reported transaction the reporting person beneficially owned 50,306 shares directly. The filing explains the sale represents shares sold to pay required tax withholdings upon vesting of restricted stock units, and also notes the reporting person acquired 266 shares under the company’s Employee Stock Purchase Plan on April 30, 2025. Previously reported RSU-related shares subject to vesting are included in the total.

Insights

Securities Analyst

TL;DR: Small, routine insider sale to cover tax withholding; not indicative of major change in ownership or control.

The Form 4 discloses a modest disposition of 84 shares at $31.39 by the company’s SVP and Chief Accounting Officer on 09/05/2025. The explanatory note explicitly states the sale financed tax withholdings from RSU vesting, which is a common administrative transaction and typically has limited informational value about management’s view of the business. The reporting person continues to hold 50,306 shares after the sale, and the filing also confirms participation in the company’s ESPP with 266 shares purchased earlier in 2025.

Corporate Governance Expert

TL;DR: Transaction appears routine and compliant; documentation of tax-withholding sale and ESPP purchase is transparent.

The filing clearly identifies the reporting person, relationship to the issuer, and the nature of the transaction as a tax-withholding sale tied to RSU vesting. Such disclosures align with Section 16 reporting obligations and help maintain transparency around insider movements. No amendment date was indicated and the Form 4 is signed via attorney-in-fact, consistent with standard practice for timely filings.

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
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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^*

Huizenga Theodore Alan

(Last) (First) (Middle)

C/O ULTRAGENYX PHARMACEUTICAL INC.

60 LEVERONI COURT

(Street)

NOVATO CA 94949

(City) (State) (Zip)

2. Issuer Name and Ticker or Trading Symbol
Ultragenyx Pharmaceutical Inc. [ RARE ]

5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)

	Director		10% Owner
X	Officer (give title below)		Other (specify below)
	SVP, Chief Accounting Officer

3. Date of Earliest Transaction (Month/Day/Year)
09/05/2025

4. If Amendment, Date of Original Filed (Month/Day/Year)

6. Individual or Joint/Group Filing (Check Applicable Line)

X	Form filed by One Reporting Person
	Form filed by More than One Reporting Person

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)
			Code	V	Amount	(A) or (D)	Price
Common Stock	09/05/2025		S		84(1)	D	$31.39	50,306(2)(3)	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)
				Code	V	(A)	(D)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares

Explanation of Responses:

1. Represents shares sold to pay required tax withholdings due to the vesting of RSUs.

2. Includes 266 shares acquired under the Company's A&R 2014 Employee Stock Purchase Plan on April 30, 2025.

3. Includes previously reported shares of common stock underlying RSUs granted to the Reporting Person, which are subject to certain vesting conditions.

	/s/ Karah Parschauer, attorney-in-fact	09/08/2025
	** 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.

FAQ

What insider transaction did Theodore A. Huizenga report for RARE on 09/05/2025?

The Form 4 reports a sale of 84 shares of Ultragenyx common stock at $31.39 per share on 09/05/2025.

Why were the shares sold according to the Form 4?

The filing states the shares were sold to pay required tax withholdings related to the vesting of restricted stock units (RSUs).

How many Ultragenyx shares does the reporting person own after the sale?

The reporting person beneficially owned 50,306 shares following the reported transaction.

Did the filing disclose any purchases by the reporting person earlier in 2025?

Yes, the filing notes the reporting person acquired 266 shares under the company’s Amended & Restated 2014 Employee Stock Purchase Plan on April 30, 2025.

What is the reporting person’s role at Ultragenyx?

The Form 4 identifies Theodore A. Huizenga as a Director and an Officer with the title SVP, Chief Accounting Officer.