Messenger RNA for Immune Cells Targeting CD19 to Treat Hard-to-Treat Low Platelet Counts

ABO2203 achieved complete B cell depletion in a first-in-human study involving three patients with refractory secondary immune thrombocytopenia.

• In transgenic mice, ABO2203 induced complete B cell depletion with less cytokine release than traditional T cell engagers.
• Patients experienced rapid and complete depletion of peripheral B cells, with sustained depletion observed in bone marrow.
• Durable platelet recovery, improved serology, and reduced disease activity were noted through 6 months of follow-up.
• ABO2203 was well tolerated, with only grade 1 and 2 adverse events and no cases of cytokine release syndrome.
• B cell reconstitution was noted, primarily consisting of transitional and naive B cells.

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