Ultragenyx Pharmaceutical Inc. (NASDAQ:RARE) just added another commercial product to its portfolio. The FDA on September 17 approved Fayuvi for the treatment of neurologic manifestations of Sanfilippo syndrome Type A in pediatric patients with preserved neurodevelopmental function. Fayuvi becomes the first approved treatment for this rare and fatal childhood disorder.
Ultragenyx stock jumped more than 12% following the announcement of the Fayuvi approval. But the stock is still down nearly 40% this year.
The more important question for investors right now is what the approval changes about Ultragenyx’s earnings trajectory. The answer is that Fayuvi expands Ultragenyx’s commercial portfolio just as the company is working toward profitability in 2027.
Fayuvi Is More Than A Regulatory Milestone
Ultragenyx Pharmaceutical Inc. made a loss of $575 million on revenue of $673 million in 2025. The loss widened slightly from $569 million in 2024, and the revenue increased from $560 million. This year, the company guided for $730 million to $760 million in total revenue from its current products, excluding potential revenue from new product launches such as Fayuvi.
With Ultragenyx aiming to reach profitability in 2027, the Fayuvi approval may have just strengthened that profitability target. That makes the drug’s approval more than a regulatory milestone for the company. Ultragenyx expects Fayuvi to be available to patients within 30 to 60 days. That short availability timeline means the company will begin testing actual commercial demand relatively quickly.
The pricing offers a glimpse into Fayuvi’s potentially material contribution to earnings. Ultragenyx has set a list price of $3.95 million for a one-time treatment with Fayuvi in the US. That makes Fayuvi one of the world’s most expensive drugs.
JP Morgan estimates that Fayuvi could bring in $200 million to $250 million in peak global sales. Even at the lower end of that estimate, Fayuvi sales would represent around 26% of Ultragenyx’s 2026 revenue guidance midpoint. However, uptake, reimbursement, and the pace of patient identification will determine Fayuvi’s actual revenue contribution. That involves factors beyond Ultragenyx’s control.
Investor Positioning Signaled Caution Before the Approval
The stock’s reaction should be viewed against investor positioning before the approval. According to Insider Monkey’s database, the hedge funds holding Ultragenyx Pharmaceutical Inc. dropped to 50 in Q2 from 55 in Q1, although some major funds increased their stakes. These included the top hedge fund holder, AQR Capital Management, whose position rose 44% to about 6.6 million shares.
Meanwhile, short interest in the stock increased ahead of the FDA decision. As of August 31, 17.1 million RARE shares were shorted, with 8 days to cover. That was 18% of the stock’s public float, marking an increase of 7.9% from the previous reading.
Both longs and shorts established their positions before Fayuvi became a commercial product. The approval changes the investment case by replacing regulatory uncertainty with the more measurable risks of commercial uptake, reimbursement, and execution.
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