Ultragenyx Pharmaceutical (NASDAQ: RARE) saw its stock plummet 5.98% in after-hours trading on Tuesday, following the announcement of a significant royalty sale agreement. The biopharmaceutical company, known for developing treatments for rare genetic diseases, disclosed that it had sold an additional 25% of its future North American royalties on Crysvita® (burosumab) to OMERS, a Canadian pension plan, for $400 million.

The deal, which takes effect in January 2028, grants OMERS an increased share of the royalties from Crysvita sales in the United States and Canada. This arrangement is an extension of a previous agreement between the two parties. While Ultragenyx frames the transaction as a means to bolster its balance sheet with non-dilutive capital, investors appear to be concerned about the long-term implications of giving up a larger portion of future revenues from one of the company's key products.

Howard Horn, Ultragenyx's CFO, emphasized that the proceeds would fund four expected product launches and support the company's path to full-year GAAP profitability in 2027. However, the market's negative reaction suggests that investors may be worried about the company's need for immediate cash and the potential impact on future earnings. The sharp stock decline indicates that shareholders are reassessing the value of Ultragenyx's future revenue streams in light of this royalty sale, despite management's assurances of strategic benefits.