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RARE Stock Down 46% as Phase III Angelman Syndrome Study Misses Goals
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Key Takeaways
Ultragenyx Pharmaceutical's phase III Aspire study failed its primary and key secondary endpoints.
The study found no meaningful efficacy differences in cognition or MDRI response incorporating five domains.
RARE will assess apazunersen's future and plans major cost cuts while supporting its commercial business.
Ultragenyx Pharmaceutical (RARE - Free Report) stock is down 46% in premarket trading today after the company reported that the late-stage study evaluating its investigational antisense oligonucleotide candidate, apazunersen (GTX-102), for Angelman syndrome (AS) failed to achieve the key goals.
The phase III Aspire study enrolled 129 patients aged four to 17 years with a genetically confirmed diagnosis of AS involving a full maternal UBE3A gene deletion. Patients were randomized equally to receive either apazunersen through an intrathecal injection via lumbar puncture or a sham procedure. Treatment consisted of three monthly 8 mg loading doses followed by a maintenance regimen increasing to a maximum quarterly dose of 14 mg of the candidate. The study assessed outcomes over 48 weeks.
Detailed Results From RARE's Phase III AS Study
Ultragenyx’s phase III Aspire study failed to demonstrate a meaningful treatment benefit of apazunersen on its primary endpoint, which measured the change from baseline in the Bayley-4 cognitive raw score. RARE also reported that the study missed its key secondary endpoint of net response on the Multidomain Responder Index (MDRI). The MDRI incorporates five areas considered relevant to AS – cognition, receptive communication, behavior, gross motor function and sleep.
Year to date, RARE stock has gained 15.3% compared with the industry’s 9.7% growth.
Image Source: Zacks Investment Research
Per Ultragenyx, the randomized treatment and control groups were comparable at baseline and consistent with the population previously evaluated in phase II. However, no differences between the groups supported efficacy on Bayley-4 cognition or the MDRI. RARE further reported that there were no meaningful differences in either net response or mean changes across the five individual MDRI domains. At the same time, the safety profile of apazunersen observed in the Aspire study remained consistent with that seen in earlier phase I/II development.
AS is a rare neurogenetic disorder associated with loss of function of the maternally inherited UBE3A gene. The disorder can cause severe cognitive and motor impairment, balance problems, seizures, limited speech, anxiety and sleep disturbances, while individuals generally require lifelong care. Per RARE, AS is estimated to affect approximately 60,000 people in commercially accessible geographies. There are no currently approved therapies for this indication.
Following the setback, Ultragenyx will evaluate the apazunersen program and decide its future disposition. The company also plans to assess its operations and implement significant expense reductions while maintaining support for its commercial business. RARE currently markets Crysvita for X-linked hypophosphatemia and tumor-induced osteomalacia, Dojolvi for long-chain fatty-acid oxidation disorders, Evkeeza for homozygous familial hypercholesterolemia (under partnership with Regeneron), Mepsevii for mucopolysaccharidosis type VII and the newly approved Genglycos (DTX401) for glycogen storage disease type Ia.
Ultragenyx Pharmaceutical Inc. Price and Consensus
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Precigen’s earnings beat estimates in three of the trailing four quarters and missed in the remaining one, with the average surprise being 108.96%.
Over the past 30 days, estimates for AC Immune’s 2026 loss per share have narrowed from 84 cents to 60 cents. Over the same period, earnings estimates for 2027 remained unchanged at 17 cents. ACIU shares have lost 9.6% year to date.
AC Immune’s earnings beat estimates in each of the trailing four quarters, with the average surprise being 33.25%.
Over the past 30 days, loss per share estimates for Aldeyra Therapeutics have narrowed from 43 cents to 39 cents for 2026. Over the same period, estimates for 2027 loss per share have narrowed from 22 cents to 16 cents. ALDX shares have plunged 71.1% year to date.
Aldeyra Therapeutics’ earnings beat estimates in each of the trailing four quarters, delivering an average surprise of 29.25%.
View the Zacks #1 Rank List
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RARE Stock Down 46% as Phase III Angelman Syndrome Study Misses Goals
Key Takeaways
Ultragenyx Pharmaceutical (RARE - Free Report) stock is down 46% in premarket trading today after the company reported that the late-stage study evaluating its investigational antisense oligonucleotide candidate, apazunersen (GTX-102), for Angelman syndrome (AS) failed to achieve the key goals.
The phase III Aspire study enrolled 129 patients aged four to 17 years with a genetically confirmed diagnosis of AS involving a full maternal UBE3A gene deletion. Patients were randomized equally to receive either apazunersen through an intrathecal injection via lumbar puncture or a sham procedure. Treatment consisted of three monthly 8 mg loading doses followed by a maintenance regimen increasing to a maximum quarterly dose of 14 mg of the candidate. The study assessed outcomes over 48 weeks.
Detailed Results From RARE's Phase III AS Study
Ultragenyx’s phase III Aspire study failed to demonstrate a meaningful treatment benefit of apazunersen on its primary endpoint, which measured the change from baseline in the Bayley-4 cognitive raw score. RARE also reported that the study missed its key secondary endpoint of net response on the Multidomain Responder Index (MDRI). The MDRI incorporates five areas considered relevant to AS – cognition, receptive communication, behavior, gross motor function and sleep.
Year to date, RARE stock has gained 15.3% compared with the industry’s 9.7% growth.
Image Source: Zacks Investment Research
Per Ultragenyx, the randomized treatment and control groups were comparable at baseline and consistent with the population previously evaluated in phase II. However, no differences between the groups supported efficacy on Bayley-4 cognition or the MDRI. RARE further reported that there were no meaningful differences in either net response or mean changes across the five individual MDRI domains. At the same time, the safety profile of apazunersen observed in the Aspire study remained consistent with that seen in earlier phase I/II development.
AS is a rare neurogenetic disorder associated with loss of function of the maternally inherited UBE3A gene. The disorder can cause severe cognitive and motor impairment, balance problems, seizures, limited speech, anxiety and sleep disturbances, while individuals generally require lifelong care. Per RARE, AS is estimated to affect approximately 60,000 people in commercially accessible geographies. There are no currently approved therapies for this indication.
Following the setback, Ultragenyx will evaluate the apazunersen program and decide its future disposition. The company also plans to assess its operations and implement significant expense reductions while maintaining support for its commercial business. RARE currently markets Crysvita for X-linked hypophosphatemia and tumor-induced osteomalacia, Dojolvi for long-chain fatty-acid oxidation disorders, Evkeeza for homozygous familial hypercholesterolemia (under partnership with Regeneron), Mepsevii for mucopolysaccharidosis type VII and the newly approved Genglycos (DTX401) for glycogen storage disease type Ia.
Ultragenyx Pharmaceutical Inc. Price and Consensus
Ultragenyx Pharmaceutical Inc. price-consensus-chart | Ultragenyx Pharmaceutical Inc. Quote
RARE’s Zacks Rank & Stocks to Consider
Ultragenyx currently carries a Zacks Rank #3 (Hold).
Some better-ranked stocks in the biotech sector are Precigen (PGEN - Free Report) , which currently sports a Zacks Rank #1 (Strong Buy), and AC Immune (ACIU - Free Report) and Aldeyra Therapeutics (ALDX - Free Report) carry a Zacks Rank #2 (Buy) each. You can see the complete list of today’s Zacks #1 Rank stocks here.
Over the past 30 days, estimates for Precigen’s 2026 loss per share have improved from a loss of 2 cents to earnings per share of 25 cents. Over the same period, earnings estimates for 2027 have risen from 25 cents to 86 cents. PGEN shares have increased 68% year to date.
Precigen’s earnings beat estimates in three of the trailing four quarters and missed in the remaining one, with the average surprise being 108.96%.
Over the past 30 days, estimates for AC Immune’s 2026 loss per share have narrowed from 84 cents to 60 cents. Over the same period, earnings estimates for 2027 remained unchanged at 17 cents. ACIU shares have lost 9.6% year to date.
AC Immune’s earnings beat estimates in each of the trailing four quarters, with the average surprise being 33.25%.
Over the past 30 days, loss per share estimates for Aldeyra Therapeutics have narrowed from 43 cents to 39 cents for 2026. Over the same period, estimates for 2027 loss per share have narrowed from 22 cents to 16 cents. ALDX shares have plunged 71.1% year to date.
Aldeyra Therapeutics’ earnings beat estimates in each of the trailing four quarters, delivering an average surprise of 29.25%.