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

Date of Report (Date of earliest event reported): September 27, 2021



Ultragenyx Pharmaceutical Inc.

(Exact name of Registrant as Specified in Its Charter)






(State or Other Jurisdiction
of Incorporation)

(Commission File Number)

(IRS Employer
Identification No.)






60 Leveroni Court


Novato, California



(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




Name of each exchange on which registered

Common Stock, $0.001 par value




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 September 27, 2021, Ultragenyx Pharmaceutical Inc. (the “Company”) and GeneTx Biotherapeutics LLC (“GeneTx”) issued a press release (the “Press Release”) announcing that the U.S. Food and Drug Administration has removed the clinical hold and GeneTx may begin dosing naïve patients in the Phase 1/2 study of GTX-102,an investigational treatment for Angelman syndrome, in pediatric patients with Angelman syndrome. GeneTx previously received clearance, under a separate amendment, to begin the Phase 1/2 study in the United Kingdom and Canada. A copy of the Press Release is filed as Exhibit 99.1.


Item 9.01

Financial Statements and Exhibits


(d) Exhibits


Exhibit No.



Press Release, dated September 27, 2021.


The cover page from the Company’s Current Report on Form 8-K dated September 27, 2021 formatted in Inline XBRL.



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 thereunto duly authorized.




Ultragenyx Pharmaceutical Inc.






September 27, 2021


/s/ Mardi C. Dier




Mardi C. Dier
Executive Vice President & Chief Financial Officer



Exhibit 99.1









GeneTx and Ultragenyx Announce FDA has Removed Clinical Hold on Phase 1/2 Clinical Study of GTX-102 for the Treatment of Angelman Syndrome in the U.S.


SARASOTA, Fla. and NOVATO, Calif — September 27, 2021 — GeneTx Biotherapeutics LLC and Ultragenyx Pharmaceutical Inc. (NASDAQ: RARE), companies partnered in the development of GTX-102, an investigational treatment for Angelman syndrome, today announced that the U.S. Food and Drug Administration (FDA) has removed the clinical hold and GeneTx may begin dosing naïve patients in the Phase 1/2 study of GTX-102 in pediatric patients with Angelman syndrome. GeneTx previously received clearance, under a separate amendment, to begin the Phase 1/2 study in the United Kingdom and Canada.


“The dosing protocol across the three regions is designed to provide a broad picture on dose response to inform loading and maintenance regimens as we move to the next phase of development,” said Scott Stromatt, M.D., Chief Medical Officer of GeneTx. “We are working with urgency to begin treating study participants in all three regions over the next several months recognizing that there is no approved therapy available for the Angelman community.”


Phase 1/2 study design in the United States

The Phase 1/2 open-label, multiple-dose study evaluates the safety, tolerability, and plasma and cerebrospinal fluid concentrations of GTX-102 in pediatric patients with Angelman syndrome with a genetically confirmed diagnosis of full maternal UBE3A gene deletion.


Naïve Patient Dose-loading Phase

Under the amended U.S. protocol, eight patients (4 to < 8 years of age) who were not previously treated with GTX-102 will be enrolled into two groups, an active group and an age-matched comparator group. The active group will receive four monthly 2 mg doses of GTX-102, while the comparator group will have limited assessments at baseline and Day 128. Patients in the comparator group will then be eligible to receive GTX-102 under the same dosing strategy as the active group.


Maintenance Phase

All U.S. patients who have completed the dose-loading phase will then move to a maintenance phase during which they will receive 2 mg of GTX-102 every three months and continue to be monitored for response and safety.









Phase 1/2 study design in U.K. and Canada


Under the protocol approved in the U.K. and Canada, approximately 12 patients will be enrolled into two cohorts split by age: patients ages 4 to < 8 years will be enrolled into Cohort 4, and patients ages 8 to < 18 years will be enrolled into Cohort 5. Two in the younger cohort and two in the older cohort will be enrolled first and assessed after two doses by a data safety monitoring board. If recommended, then an additional four patients can be enrolled in each of the two cohorts.


The starting doses in Cohorts 4 and 5 will be 3.3 and 5 mg, respectively. Patients will receive three to four monthly doses, titrated individually through smaller steps than the first three cohorts in the original study with dose increases based on response and enhanced safety monitoring. Patients will then move to a maintenance phase during which they will receive GTX-102 every three months and continue to be monitored for response and safety. In this phase, individual dose titration may continue if safety is sustained, and the clinical response is not much improved in at least 2 domains up to a maximum dose of 14 mg.


About Angelman Syndrome


Angelman syndrome is a rare, neurogenetic disorder caused by loss-of-function of the maternally inherited allele of the UBE3A gene. The maternal-specific inheritance pattern of Angelman syndrome is due to genomic imprinting of UBE3A in neurons of the central nervous system, a naturally occurring phenomenon in which the maternal UBE3A allele is expressed and the paternal UBE3A is not. Silencing of the paternal UBE3A allele is regulated by the UBE3A antisense transcript (UBE3A-AS), the intended target of GTX-102. In almost all cases of Angelman syndrome, the maternal UBE3A allele is either missing or mutated, resulting in limited to no protein expression. This condition is typically not inherited but instead occurs spontaneously. It is estimated to affect 1 in 12,000 to 1 in 20,000 people globally.


Individuals with Angelman syndrome have developmental delay, balance issues, motor impairment, and debilitating seizures. Some individuals with Angelman syndrome are unable to walk and most do not speak. Anxiety and disturbed sleep can be serious challenges in individuals with Angelman syndrome. While individuals with Angelman syndrome have a normal lifespan, they require continuous care and are unable to live independently. Angelman syndrome is not a degenerative disorder, but the loss of the UBE3A protein expression in neurons results in abnormal communications between neurons. Angelman syndrome is often misdiagnosed as autism or cerebral palsy. There are no currently approved therapies for Angelman syndrome; however, several symptoms of








this disorder can be reversed in adult animal models of Angelman syndrome suggesting that improvement of symptoms can potentially be achieved at any age.


About GTX-102


GTX-102 is an investigational antisense oligonucleotide delivered via intrathecal administration and designed to target and inhibit expression of UBE3A-AS. Nonclinical studies show that GTX-102 reduces the levels of UBE3A-AS and reactivates expression of the paternal UBE3A allele in neurons of the CNS. Reactivation of paternal UBE3A expression in animal models of Angelman syndrome has been associated with improvements in some of the neurological symptoms associated with the condition. GTX-102 has been granted Orphan Drug Designation, Rare Pediatric Disease Designation, and Fast Track Designation from the U.S. Food and Drug Administration (FDA). In August 2019, GeneTx and Ultragenyx announced a partnership to develop GTX-102, with Ultragenyx receiving an exclusive option to acquire GeneTx.


About GeneTx Biotherapeutics


GeneTx Biotherapeutics LLC is a startup biotechnology company singularly focused on developing and commercializing a safe and effective antisense therapeutic for the treatment of Angelman syndrome. GeneTx was launched by FAST, a patient advocacy organization and the largest non-governmental funder of Angelman syndrome research. GeneTx licensed the rights to antisense technology intellectual property from the Texas A&M University System in December 2017.


About Ultragenyx Pharmaceutical Inc.


Ultragenyx is a biopharmaceutical company committed to bringing novel therapies to patients for the treatment of serious rare and ultra-rare genetic diseases. The company has built a diverse portfolio of approved medicines and treatment candidates aimed at addressing diseases with high unmet medical need and clear biology, for which there are typically no approved therapies treating the underlying disease.


The company is led by a management team experienced in the development and commercialization of rare disease therapeutics. Ultragenyx’s strategy is predicated upon time- and cost-efficient drug development, with the goal of delivering safe and effective therapies to patients with the utmost urgency.


For more information on Ultragenyx, please visit the company's website at: www.ultragenyx.com.









Forward-Looking Statements


Except for the historical information contained herein, the matters set forth in this press release, including statements related to Ultragenyx's expectations and projections regarding its business plans and objectives for GTX-102, the therapeutic potential and clinical benefits of GTX-102, expectations regarding the safety and tolerability of GTX-102, and future clinical developments for GTX-102 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 ability of the company and GeneTx to successfully develop GTX-102 at lower doses, including the resolution of adverse events that were seen at higher doses, whether lower doses of GTX-102 are sufficiently effective to support the continued development of the program, the effects from the COVID-19 pandemic on the company’s clinical activities, business and operating results, risks related to reliance on third party partners to conduct certain activities on the company’s behalf, uncertainty and potential delays related to clinical drug development, 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 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. Ultragenyx 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 Ultragenyx in general, see Ultragenyx's Quarterly Report on Form 10-Q filed with the Securities and Exchange Commission on August 3, 2021, and its subsequent periodic reports filed with the Securities and Exchange Commission.






Ultragenyx Pharmaceutical Inc.


Joshua Higa












Carolyn Wang




Paula Evans