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 Estimated average burden hours per response: 0.5
	Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

1. Name and Address of Reporting Person* Crombez Eric (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) EVP and Chief Medical Officer
	3. Date of Earliest Transaction (Month/Day/Year) 03/01/2024
	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
	Rule 10b5-1(c) Transaction Indication Check this box to indicate that a transaction was made pursuant to a contract, instruction or written plan that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c). See Instruction 10.

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	03/01/2024		A		19,400(1)	A	$0	49,912	D
Common Stock	03/01/2024		S		1,238(2)	D	$53.76	48,927(3)(4)	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
Stock Option (Right to Buy)	$53.69	03/01/2024		A		34,200		(5)	03/01/2034	Common Stock	34,200	$0	34,200	D
Stock Option (Right to Buy)	$67.37	03/01/2024		A		2,351		(6)	03/01/2027	Common Stock	2,351	$0	2,351	D

Explanation of Responses:

1. Award of Restricted Stock Units ("RSUs") under the Company's 2023 Incentive Plan. The RSUs shall vest with respect to 1/4th of the underlying shares on each anniversary of the grant date, such that the RSUs are fully vested on the fourth anniversary of the grant date

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

3. Includes 253 shares acquired under the Company's Amended and Restated Employee Stock Purchase Plan on October 31, 2023.

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

5. On the first anniversary of the grant date of the option (the "Option Anniversary Date"), 1/4th of the shares initially subject to the option shall vest; thereafter, 1/48th of the shares initially subject to the option shall vest on each month as measured from the Option Anniversary Date.

6. On March 1, 2022, the Reporting Person was granted an option to purchase 2,351 shares of common stock. The option vests upon the achievement of specified performance criteria. Upon achievement of the performance criteria, 1/3 of the option vests on the date of certification by the Issuer's compensation committee of achievement of the performance criteria, 1/3 of the option vests on March 1, 2024 and 1/3 of the option vests on March 1, 2025. On March 1, 2024, the Issuer's compensation committee certified achievement of the performance criteria for the option, resulting in the vesting of the option of 1,568 shares on that date.

	/s/ Karah Parschauer, attorney-in-fact	03/05/2024
	** 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).
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