GSK Stock Surges 1.59% to 2025 Peak on AnaptysBio Partnership, Jemperli Royalty Outlook

The share price rose to its highest level so far this month today, with an intraday gain of 1.59%.

GlaxoSmithKline’s (GSK) stock climbed to a 2025 peak amid optimism surrounding its partnership with AnaptysBio and the commercial trajectory of Jemperli, a key oncology asset. The biologics royalty stream from Jemperli, projected to generate over $2.7 billion in annual sales by 2031, underpins investor confidence in GSK’s long-term revenue visibility. AnaptysBio’s planned 2026 separation of biopharma and royalty assets, including Jemperli royalties, has sparked speculation about potential structural changes to the partnership. While the move could complicate royalty flows if restructuring disrupts terms, it also signals AnaptysBio’s focus on streamlining operations, which may indirectly bolster Jemperli’s market performance.

The stock’s rally reflects broader confidence in GSK’s strategic positioning in high-growth therapeutic areas. Jemperli’s strong safety profile, with no reported malignancies or major adverse cardiovascular events in clinical trials, reinforces its appeal as a differentiated treatment. However, the 2026 separation introduces uncertainty about the longevity of royalty payments, which account for a material portion of GSK’s portfolio returns. Investors are balancing near-term optimism with caution over how AnaptysBio’s reorganization might reshape the partnership’s financial dynamics. For now, the market appears to price in Jemperli’s peak sales potential, with the stock’s record high signaling a positive near-term outlook despite structural risks ahead.