Capstan Therapeutics begins Phase 1 trial of CPTX2309 in healthy volunteers; first participants dosed

AbbVie/CPTX2309

Capstan (now part of AbbVie) announced the dosing of the first participants in a Phase 1 trial of CPTX2309 for B cell-mediated autoimmune diseases. The trial will assess safety, tolerability, pharmacokinetics and B cell depletion and recovery in multiple dose cohorts of healthy volunteers.

• Phase 1 trial began in June 2025 with healthy volunteers.
• Trial will evaluate safety, tolerability, and B cell depletion kinetics across dose levels.
• Preclinical studies demonstrated robust CAR-T engineering, profound B cell depletion, and predominantly naïve B cell repopulation.
• CPTX2309 uses a targeted lipid nanoparticle platform to achieve CD8+ T cell selectivity.
• Results expected to guide pivotal trial design for autoimmune indications in 2026.