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FDA Grants Orphan Drug Status to Cellenkos’ CK0804 for Myelofibrosis

The designation provides development incentives for a planned phase 2 trial following early activity signals.

Overview

  • Myelofibrosis affects an estimated 25,000 people in the U.S., and current JAK inhibitor treatments ease symptoms but generally do not alter the underlying disease.
  • CK0804 is an allogeneic, off-the-shelf CXCR4hi regulatory T-cell therapy designed to home to CXCL12-rich bone marrow and spleen and deliver IL-10 to modulate inflammation.
  • In a 13-patient study presented at ASH 2025, 45% of 11 evaluable patients saw more than a 10% spleen volume reduction and 78% of 9 evaluable patients reported over a 50% symptom reduction.
  • Responders exhibited biomarker changes consistent with immune modulation, including increased IL-10, decreased TGFβ, reductions in pathogenic monocytes, and normalization of the bone marrow myeloid-to-erythroid ratio.
  • The phase 1 trial evaluated CK0804 as an add-on to stable-dose ruxolitinib, and the company says it intends to advance the program into phase 2 after this orphan designation.