FDA grants Priority Review to Ultragenyx (NASDAQ: RARE) DTX401 gene therapy

Rhea-AI Filing Summary

Ultragenyx Pharmaceutical Inc. reported that the U.S. Food and Drug Administration has accepted for review its Biologics License Application for DTX401 AAV gene therapy (pariglasgene brecaparvovec) to treat Glycogen Storage Disease Type Ia. The FDA granted the application Priority Review and set a Prescription Drug User Fee Act action date of August 23, 2026. This step marks an important U.S. regulatory milestone for DTX401, though the company highlights that approval is not assured and development and regulatory risks remain.

Positive

• FDA Priority Review granted for DTX401 BLA in Glycogen Storage Disease Type Ia, with a defined PDUFA action date of August 23, 2026, representing a major regulatory milestone for this gene therapy candidate.

Negative

• None.

Insights

Biotech regulatory analyst

FDA Priority Review of DTX401 is a key regulatory milestone but approval and commercialization remain uncertain.

The FDA’s acceptance of the Biologics License Application for DTX401 in Glycogen Storage Disease Type Ia and grant of Priority Review signals that the agency views this gene therapy as potentially offering significant benefit for a serious condition.

A Priority Review with a PDUFA action date of August 23, 2026 provides a defined timeline for a decision, which can focus attention on DTX401’s prospects. However, Ultragenyx explicitly notes substantial risks around clinical outcomes, regulatory approval, manufacturing, competition and market size, so the ultimate impact depends on the FDA’s decision and subsequent commercialization.

0001515673false00015156732026-02-232026-02-23

UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
WASHINGTON, D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934

Date of Report (Date of earliest event reported): February 23, 2026

Ultragenyx Pharmaceutical Inc.

(Exact name of Registrant as Specified in Its Charter)

Delaware			001-36276	27-2546083
(State or Other Jurisdiction of Incorporation)			(Commission File Number)	(IRS Employer Identification No.)
60 Leveroni Court
Novato, California				94949
(Address of Principal Executive Offices)				(Zip Code)

Registrant’s Telephone Number, Including Area Code: 415 483-8800

(Former Name or Former Address, if Changed Since Last Report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

☐Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

☐Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

☐Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

☐Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

Securities registered pursuant to Section 12(b) of the Act:

Title of each class		Trading Symbol(s)		Name of each exchange on which registered
Common Stock, $0.001 par value		RARE		Nasdaq Global Select Market

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§ 230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§ 240.12b-2 of this chapter).

Emerging growth company ☐

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐

Item 8.01 Other Events.

On February 23, 2026, Ultragenyx Pharmaceutical Inc. (the “Company”) issued a press release announcing that the U.S. Food and Drug Administration (the “FDA”) has accepted for review the Biologics License Application (the “BLA”) seeking approval of DTX401 AAV gene therapy (pariglasgene brecaparvovec) for the treatment of Glycogen Storage Disease Type Ia (GSDIa). The FDA granted the BLA Priority Review and assigned a Prescription Drug User Fee Act (PDUFA) action date of August 23, 2026.

Cautionary Note Regarding Forward-Looking Statements

This Current Report on Form 8-K contains forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995. These statements may be identified by the use of words such as, but not limited to, “anticipates,” “continue,” “will,” or other similar terms or expressions that concern the Company’s expectations, plans and intentions. Forward-looking statements including, without limitation, statements related to the development, timing and progress of DTX401, including the timing of FDA review of the DTX401 BLA, the timing and outcome of any FDA inspections related to the company’s gene therapy manufacturing facility, the timing of future regulatory interactions related to DTX401, including the outcome of the BLA submission, business plans and objectives for DTX401, expectations regarding the tolerability and safety of DTX401, and future clinical and regulatory developments for DTX401, are forward-looking statements within the meaning of the "safe harbor" provisions of the Private Securities Litigation Reform Act of 1995. Such forward-looking statements involve substantial risks and uncertainties that could cause our clinical development programs, collaboration with third parties, future results, performance or achievements to differ significantly from those expressed or implied by the forward-looking statements. Such risks and uncertainties include, among others, the uncertainty of clinical drug development and unpredictability and lengthy process for obtaining regulatory approvals, the ability of the Company to successfully develop DTX401 and receive FDA approval of the BLA for DTX401, the Company’s ability to achieve its projected development goals in its expected timeframes, risks related to adverse side effects, risks related to reliance on third party partners to conduct certain activities on the Company’s behalf, smaller than anticipated market opportunities for the Company’s products and product candidates, manufacturing risks, the Company’s limited experience in operating its own manufacturing facility, the ability of the Company and its third party manufacturers to comply with regulatory requirements, competition from other therapies or products, and other matters that could affect sufficiency of existing cash, cash equivalents and short-term investments to fund operations, the company’s future operating results and financial performance, the timing of clinical trial activities and reporting results from same, and the availability or commercial potential of Ultragenyx’s products and drug candidates. The Company undertakes no obligation to update or revise any forward-looking statements. For a further description of the risks and uncertainties that could cause actual results to differ from those expressed in these forward-looking statements, as well as risks relating to the business of the Company in general, see the Company's Annual Report on Form 10-K filed with the Securities and Exchange Commission (SEC) on February 18, 2026, and its subsequent periodic reports filed with the SEC.

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

			Ultragenyx Pharmaceutical Inc.
Date:	February 23, 2026	By:	/s/ Howard Horn
			Howard Horn Executive Vice President, Chief Financial Officer, Corporate Strategy

FAQ

What did Ultragenyx (RARE) announce about its DTX401 gene therapy?

Ultragenyx announced that the FDA accepted for review its Biologics License Application for DTX401 AAV gene therapy to treat Glycogen Storage Disease Type Ia. The application also received Priority Review, highlighting potential importance for this serious inherited metabolic disorder.

What is the FDA PDUFA action date for Ultragenyx (RARE) DTX401?

The FDA set a Prescription Drug User Fee Act (PDUFA) action date of August 23, 2026 for Ultragenyx’s DTX401 Biologics License Application. This date marks when the FDA aims to complete its review and issue a decision on the gene therapy application.

What FDA review status did Ultragenyx (RARE) receive for DTX401?

Ultragenyx received FDA Priority Review for the DTX401 Biologics License Application. Priority Review shortens the standard review timeline for therapies that could provide significant improvements in treatment, underscoring the potential importance of DTX401 for Glycogen Storage Disease Type Ia patients.

Which disease is Ultragenyx (RARE) targeting with DTX401?

DTX401 is being developed to treat Glycogen Storage Disease Type Ia, a rare inherited metabolic disorder. Ultragenyx’s Biologics License Application for this AAV gene therapy has been accepted by the FDA and is under Priority Review for potential U.S. approval.

What risks did Ultragenyx (RARE) highlight regarding DTX401’s FDA review?

Ultragenyx cautioned that substantial risks remain, including uncertainties in clinical development, the lengthy and unpredictable regulatory process, potential adverse side effects, manufacturing challenges, competition, and smaller-than-expected market opportunities, all of which could affect the outcome of the DTX401 Biologics License Application.

Does FDA Priority Review guarantee approval of Ultragenyx (RARE) DTX401?

FDA Priority Review does not guarantee approval of DTX401. It accelerates the review timeline for therapies addressing serious conditions, but Ultragenyx notes that significant clinical, regulatory, manufacturing and market risks could still lead to a negative decision or affect commercial prospects.

Filing Exhibits & Attachments

1 document

Other Documents

• EX-101 XBRL TAXONOMY EXTENSION SCHEMA WITH EMBEDDED LINKBASES DOCUMENT 23.3 KB