Notice2025-16646
Amylyx Pharmaceuticals, Inc.; Withdrawal of Approval of New Drug Application for RELYVRIO (Sodium Phenylbutyrate and Taurursodiol) for Suspension, 3 Gram/Packet and 1 Gram/Packet
Primary source
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Published
August 29, 2025
Issuing agencies
Health and Human Services DepartmentFood and Drug Administration
Abstract
The Food and Drug Administration (FDA or Agency) is withdrawing approval of the new drug application (NDA) for RELYVRIO (sodium phenylbutyrate and taurursodiol) for suspension, 3 gram (g)/ packet and 1 g/packet, held by Amylyx Pharmaceuticals, Inc. (Amylyx), 43 Thorndike St., Cambridge, MA 02141. Amylyx has voluntarily requested that FDA withdraw approval of this application and has waived its opportunity for a hearing.
Full Text
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<title>Federal Register, Volume 90 Issue 166 (Friday, August 29, 2025)</title>
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[Federal Register Volume 90, Number 166 (Friday, August 29, 2025)]
[Notices]
[Page 42251]
From the Federal Register Online via the Government Publishing Office [<a href="http://www.gpo.gov">www.gpo.gov</a>]
[FR Doc No: 2025-16646]
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DEPARTMENT OF HEALTH AND HUMAN SERVICES
Food and Drug Administration
[Docket No. FDA-2025-N-2654]
Amylyx Pharmaceuticals, Inc.; Withdrawal of Approval of New Drug
Application for RELYVRIO (Sodium Phenylbutyrate and Taurursodiol) for
Suspension, 3 Gram/Packet and 1 Gram/Packet
AGENCY: Food and Drug Administration, HHS.
ACTION: Notice.
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SUMMARY: The Food and Drug Administration (FDA or Agency) is
withdrawing approval of the new drug application (NDA) for RELYVRIO
(sodium phenylbutyrate and taurursodiol) for suspension, 3 gram (g)/
packet and 1 g/packet, held by Amylyx Pharmaceuticals, Inc. (Amylyx),
43 Thorndike St., Cambridge, MA 02141. Amylyx has voluntarily requested
that FDA withdraw approval of this application and has waived its
opportunity for a hearing.
DATES: Approval is withdrawn as of August 29, 2025.
FOR FURTHER INFORMATION CONTACT: Kimberly Lehrfeld, Center for Drug
Evaluation and Research, Food and Drug Administration, 10903 New
Hampshire Ave., Bldg. 51, Rm. 6250, Silver Spring, MD 20993-0002, 301-
796-3137, <a href="/cdn-cgi/l/email-protection#d398babeb1b6a1bfaafd9fb6bba1b5b6bfb793b5b7b2fdbbbba0fdb4bca5"><span class="__cf_email__" data-cfemail="3c7755515e594e5045127059544e5a5950587c5a585d1254544f125b534a">[email protected]</span></a>.
SUPPLEMENTARY INFORMATION: On September 29, 2022, FDA approved NDA
216660 for RELYVRIO (sodium phenylbutyrate and taurursodiol) for
suspension, 3 g/packet and 1 g/packet, for the treatment of amyotrophic
lateral sclerosis (ALS) in adults.
On April 30, 2024, Amylyx reported to the Agency that a Phase 3
Trial of AMX0035 for Amyotrophic Lateral Sclerosis Treatment (Study
A35-004, also known as PHOENIX), a global, 48-week, randomized,
placebo-controlled clinical trial of sodium phenylbutyrate and
taurursodiol in patients living with ALS, did not meet its prespecified
primary and secondary endpoints. On September 30, 2024, Amylyx notified
the Agency they planned to discontinue marketing of RELYVRIO as of
October 31, 2024. On October 31, 2024, FDA requested that the applicant
submit a letter to voluntarily request withdrawal of approval of
RELYVRIO (sodium phenylbutyrate and taurursodiol) for suspension, 3 g/
packet and 1 g/packet, according to Sec. 314.150(d) (21 CFR
314.150(d)) based on the results of the Phase 3 PHOENIX trial.
On February 28, 2025, Amylyx submitted a letter asking FDA to
withdraw approval of NDA 216660 for RELYVRIO (sodium phenylbutyrate and
taurursodiol) for suspension, 3 g/packet and 1 g/packet, according to
Sec. 314.150(d) and waiving its opportunity for a hearing. In its
letter requesting withdrawal of approval, Amylyx stated that it is
voluntarily requesting withdrawal based on results from the Phase 3
PHOENIX trial.
For the reasons discussed above, and in accordance with the
applicant's request, approval of NDA 216660 for RELYVRIO (sodium
phenylbutyrate and taurursodiol) for suspension, 3 g/packet and 1 g/
packet, and all amendments and supplements thereto, is withdrawn under
Sec. 314.150(d). Distribution of RELYVRIO (sodium phenylbutyrate and
taurursodiol) for suspension, 3 g/packet and 1 g/packet, into
interstate commerce without an approved application is illegal and
subject to regulatory action (see sections 505(a) and 301(d) of the
Federal Food, Drug, and Cosmetic Act (21 U.S.C. 355(a) and 331(d)).
Grace R. Graham,
Deputy Commissioner for Policy, Legislation, and International Affairs.
[FR Doc. 2025-16646 Filed 8-28-25; 8:45 am]
BILLING CODE 4164-01-P
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