Several clinical-stage biotechnology companies experienced significant after-hours trading surges on Friday, driven by anticipation of upcoming trial data releases and positive pipeline developments across multiple therapeutic areas.
MBX Biosciences Leads Rally Ahead of Hypoparathyroidism Data
MBX Biosciences Inc. (MBX) saw the most dramatic movement, with shares surging 33% in after-hours trading from $10.00 to $13.77. The spike followed the company's announcement that it will release topline results from its Phase 2 trial of Canvuparatide on Monday, September 22. Canvuparatide represents a potential once-weekly therapy for chronic hypoparathyroidism, addressing a significant unmet medical need in this rare endocrine disorder.
The company scheduled a webcast presentation of the trial results for 8:00 AM ET, indicating the high level of investor and clinical interest in the data. Despite closing down 0.70% during regular trading hours, the after-hours surge of 37.70% demonstrates strong market anticipation surrounding the upcoming results.
Structure Therapeutics Gains on Obesity Pipeline Progress
Structure Therapeutics Inc. (GPCR) jumped 11.37% to $26.26 in after-hours trading, building on a 1.51% gain during the regular session. The movement reflects growing attention around the company's lead candidate, aleniglipron (GSBR-1290), currently being evaluated in two Phase 2b trials called ACCESS and ACCESS II for obesity and related metabolic conditions.
Topline results from these pivotal studies are expected by the end of 2025, representing a major milestone for the company's obesity program. Structure Therapeutics also plans to initiate Phase 1 trials for ACCG-2671, an oral amylin receptor agonist designed to complement GLP-1 therapies in the competitive obesity treatment landscape. With approximately $786.5 million in cash, the company has sufficient runway to support its pipeline development through 2027.
Autoimmune and Neurological Programs Drive Additional Gains
Cartesian Therapeutics Inc. (RNAC) rose 5.51% to $9.96 in extended trading, despite an 8.34% decline during regular hours. The company is advancing Descartes-08 in a Phase 2 open-label trial for systemic lupus erythematosus (SLE), with preliminary data expected in the second half of 2025. The trial is evaluating outpatient administration without preconditioning chemotherapy in patients with this incurable autoimmune disease characterized by systemic inflammation affecting multiple organ systems.
Cartesian maintains $162.1 million in cash as of June 30, 2025, sufficient to support operations including completion of the ongoing Phase 3 AURORA trial for Descartes-08 in myasthenia gravis into mid-2027.
Epilepsy and Metabolic Programs Show Momentum
Rapport Therapeutics Inc. (RAPP) gained 3.60% to $27.31 after-hours, following positive developments with RAP-219 for focal onset seizures. The company recently announced positive topline results from its Phase 2a trial, demonstrating significant seizure reduction and favorable tolerability. RAP-219 represents a potential first-in-class TARP γ8-specific AMPAR negative allosteric modulator, with Phase 3 trials expected to initiate in 2026.
Rezolute Inc. (RZLT) rose 3.77% to $7.99 in extended trading, despite a 6.10% decline during regular hours. The company recently reported alignment with the FDA on a streamlined design for its Phase 3 trial in tumor hyperinsulinism, reducing study size and removing the need for a placebo-controlled arm. Topline data from the Phase 3 sunRIZE trial for congenital hyperinsulinism is expected in December 2025.
Market Dynamics and Clinical Development Landscape
The after-hours rally reflects strong investor appetite for clinical-stage biotechnology companies with near-term data catalysts. Trading volumes across these companies exceeded their daily averages, with Structure Therapeutics seeing over 1 million shares traded and Rapport Therapeutics reaching more than 1.5 million shares, more than double its average daily volume.
The diverse therapeutic areas represented—from rare endocrine disorders to obesity, autoimmune diseases, and neurological conditions—demonstrate the breadth of innovation in the current biotech pipeline. With multiple companies positioned with substantial cash reserves and clear regulatory pathways, the sector appears well-positioned for continued clinical progress through 2025 and beyond.
