Sangamo shares surge 24.33% premarket after FDA grants Fast Track for ST-503 to treat small fiber neuropathy.

Sangamo Therapeutics (SGMO) surged 24.33% in premarket trading following the U.S. FDA’s Fast Track Designation for its investigational epigenetic regulator ST-503, targeting intractable pain from small fiber neuropathy (SFN). The designation accelerates regulatory engagement, enabling more frequent FDA interactions and potential pathways for Accelerated Approval or Priority Review, underscoring the unmet medical need for SFN treatments. The company highlighted positive nonclinical data from September 2025, showing ST-503’s durability, potency, and safety in nonhuman primates, alongside plans to initiate its Phase 1/2 STAND study in the coming months. This regulatory milestone and the drug’s potential to address a high-unmet-need chronic pain condition likely drove investor optimism.