[8-K] Ultragenyx Pharmaceutical Inc. Reports Material Event

Rhea-AI Filing Summary

Ultragenyx (Nasdaq: RARE) filed an 8-K disclosing receipt of FDA Breakthrough Therapy Designation for GTX-102 (apazunersen) to treat Angelman syndrome.

The decision is supported by positive Phase 1/2 data in 74 children (ages 4-17) showing rapid, sustained and continuing developmental gains over up to three years.

Breakthrough status grants intensive FDA guidance, rolling review and potential priority review, which could materially shorten development timelines and lower regulatory risk.

The filing includes customary forward-looking statements covering clinical, regulatory and manufacturing uncertainties but announces no new financial terms.

Positive

• FDA Breakthrough Therapy Designation for GTX-102 expedites development and review, materially increasing probability and speed of potential approval for the Angelman syndrome program.

Negative

• None.

Insights

Regulatory Affairs Analyst

TL;DR: Breakthrough designation de-risks GTX-102 and accelerates its FDA path.

Breakthrough Therapy Designation (BTD) is reserved for drugs showing preliminary evidence of substantial improvement over existing treatments. It provides earlier, more frequent FDA interaction, eligibility for rolling submissions and priority review. For Ultragenyx, BTD materially shortens regulatory timelines—often by 6-12 months—and signals agency confidence in the Phase 1/2 data set. Angelman syndrome lacks approved disease-modifying therapies, so an expedited path strengthens GTX-102’s competitive position and potential orphan pricing power. While safety and efficacy must still be confirmed in larger trials, the designation reduces approval risk and enhances the asset’s strategic value for partnerships or financing.

Biotech Equity Analyst

TL;DR: Milestone is clearly positive but commercial value hinges on pivotal data.

From a valuation lens, BTD adds a meaningful catalyst: it increases assumed probability of approval and brings cash-flow visibility forward, supporting a higher risk-adjusted NPV for GTX-102. Ultragenyx now holds multiple late-stage rare-disease assets, improving portfolio diversification. However, Phase 1/2 enrolled only 74 patients; pivotal trial design, durability of response and manufacturing scale remain open questions. Investors should watch for guidance on Phase 3 initiation timing and confirm whether the company will require additional capital to complete trials. Nonetheless, today’s disclosure is incrementally accretive to sentiment and justifies near-term multiple expansion.

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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): June 27, 2025

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 June 27, 2025, Ultragenyx Pharmaceutical Inc. (the “Company”) issued a press release announcing that it has received Breakthrough Therapy Designation from the U.S. Food and Drug Administration (the "FDA") for GTX-102 (apazunersen) as a treatment for Angelman syndrome.

The FDA’s decision is based on preliminary clinical evidence including positive data from the Phase 1/2 study in 74 patients (4-17 years of age) with a full maternal UBE3A gene deletion, that showed participants have made consistent developmental gains with rapid, sustained and continuing improvements across multiple symptom domains when treated for up to three years. Breakthrough Therapy Designation aims to expedite the development and review of drugs that are intended to treat serious or life-threatening diseases and whose preliminary clinical evidence indicates that the drug may demonstrate substantial improvement on one or more clinically significant endpoints over existing therapies.

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 include, without limitation, statements regarding the clinical benefit, tolerability and safety of GTX-102 and the corresponding impact on patients and timing for clinical development or regulatory review of GTX-102. Such forward-looking statements involve substantial risks and uncertainties that could cause the Company’s 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 GTX-102, the Company’s ability to achieve its projected development goals in its expected timeframes, the risk that results from earlier studies may not be predictive of future study results, 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, competition from other therapies or products, and other matters that could affect the 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 the Company’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 Quarterly Report on Form 10-Q filed with the Securities and Exchange Commission (SEC) on May 7, 2025, 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:	June 27, 2025	By:	/s/ Howard Horn
			Executive Vice President, Chief Financial Officer, Corporate Strategy

FAQ

What milestone did RARE announce in its June 27 2025 8-K?

Ultragenyx received FDA Breakthrough Therapy Designation for GTX-102 (apazunersen) targeting Angelman syndrome.

How many patients were included in the supporting Phase 1/2 study for GTX-102?

The preliminary data cited involved 74 pediatric patients aged 4-17 with full maternal UBE3A deletions.

Why is Breakthrough Therapy Designation important for RARE investors?

It offers accelerated FDA interactions, rolling submissions and priority review, potentially shortening time-to-market and lowering regulatory risk.

Does the 8-K disclose new financial commitments or revenues for GTX-102?

No. The filing is limited to the regulatory milestone and includes only standard forward-looking risk statements.

What are the next steps for GTX-102 after receiving Breakthrough status?

Ultragenyx must finalize pivotal trial design and engage the FDA under the Breakthrough program before submitting a BLA.