Top Stock Market Losers: Ultragenyx Trial Failure, Polestar Outlook Cut, and Inverse ETFs Lead Declines

• Ultragenyx Pharmaceutical Inc. (NASDAQ: RARE) plunged after its experimental Angelman syndrome treatment failed a Phase 3 trial.
• Polestar Automotive Holding UK PLC (NASDAQ: PSNY) declined after reporting weaker first-half results and reducing its full-year volume-growth forecast.
• Inverse leveraged ETFs tied to Strategy Inc. (NASDAQ: MSTR) and Coinbase Global, Inc. (NASDAQ: COIN)fell as their underlying stocks rallied.

Several stocks recorded substantial declines on September 3, 2026, even as the broader U.S. market finished sharply higher. Ultragenyx Pharmaceutical Inc. (NASDAQ: RARE) led the losers, falling 44.06%, or $11.69, to $14.85. Trading volume exceeded 27 million shares, compared with a much lower average volume.

The decline followed disappointing Phase 3 results for apazunersen, previously known as GTX-102, in patients with Angelman syndrome. The treatment failed to meet the trial’s primary and secondary endpoints, prompting several analysts to downgrade the stock or lower their price targets, according to Barron’s.

Research Alliance Corporation III (NASDAQ: RACC) dropped 36.76% to $12.37 on volume of approximately 833,000 shares. The proposed merger with Oak Hill Bio was announced on July 27. The transaction is expected to provide the combined company with approximately $175 million in gross proceeds and result in its shares trading under the ticker OAKH, according to Oak Hill Bio. The latest decline appeared to be a reversal of an earlier speculative rally rather than an immediate reaction to a new merger announcement.

Polestar Automotive Holding UK PLC (NASDAQ: PSNY) fell 28.11% to $8.69, trading between $8.03 and $12.49. First-half vehicle sales were nearly unchanged at 30,423 units, while revenue declined approximately 4% to $1.4 billion.

Polestar reduced its 2026 volume-growth forecast from low-double-digit growth to the low-to-mid-single-digit range. The company cited competitive market conditions, model transitions, and U.S. restrictions affecting China-linked vehicle technology. These restrictions have forced Polestar to stop selling certain vehicles in the United States, according to Reuters.

Inverse leveraged ETFs also posted major declines. The Defiance Daily Target 2X Short MSTR ETF (NASDAQ: SMST) fell 34.90% to $17.96 as Strategy Inc. (NASDAQ: MSTR) surged 17.57%. The GraniteShares 2x Short COIN Daily ETF (NASDAQ: CONI) declined 20.30% to $26.01 as Coinbase Global, Inc. (NASDAQ: COIN) gained 10.13%.

These inverse ETFs seek to deliver approximately twice the opposite of their underlying stocks’ daily performance. Their losses reflected strong gains in Strategy and Coinbase during a broad cryptocurrency rally.