FDA Grants Orphan Status to Cellenkos’ CK0804 in Myelofibrosis

Cellenkos Inc., a clinical-stage biotechnology company developing off-the-shelf regulatory T cell (Treg) therapies, has received Orphan Drug Designation from the U.S. Food and Drug Administration for its investigational therapy CK0804 for the treatment of myelofibrosis. The designation highlights the potential of CK0804 to address a significant unmet medical need in a rare and life-threatening blood cancer that affects an estimated 25,000 patients in the United States.

Myelofibrosis is a chronic and progressive myeloproliferative neoplasm characterized by bone marrow fibrosis, abnormal blood cell production, and debilitating symptoms such as anemia, splenomegaly, and fatigue. Despite available treatments, including JAK inhibitors, many patients eventually fail therapy or experience limited and short-lived benefits, underscoring the need for novel disease-modifying approaches.

CK0804 is an allogeneic, off-the-shelf cell therapy composed of CXCR4-high regulatory T cells designed to home preferentially to tissues expressing the CXCL12 ligand. In myelofibrosis, CXCL12 is overexpressed in the bone marrow and in sites of extramedullary hematopoiesis, such as the spleen. Once localized to these disease-relevant tissues, CK0804 Tregs interact with antigen-presenting cells, proliferate in vivo, and secrete the anti-inflammatory cytokine interleukin-10 (IL-10). Through these mechanisms, the therapy aims to resolve inflammation and modulate platelet-derived growth factor–driven pathways involved in disease remodeling, without reliance on major histocompatibility complex (MHC) matching.

Dr. Simrit Parmar, founder of Cellenkos, said the Orphan Drug Designation represents a key milestone in the development of CK0804 and supports the company’s plans to advance the program into Phase 2 clinical trials. She noted that biological signals observed in treated patients, including increased IL-10 and reduced levels of pro-fibrotic cytokines such as TGFβ, point to the disease-modifying potential of Treg-based therapies in myelofibrosis.

Early clinical data have shown encouraging signs of activity. In a 13-patient study involving individuals with advanced myelofibrosis who had failed a median of two prior therapies, CK0804 demonstrated meaningful clinical benefits. Results presented at the 67th Annual Meeting of the American Society of Hematology in December 2025 showed spleen volume reductions greater than 10% in nearly half of evaluable patients and symptom burden reductions greater than 50% in the majority of those assessed. Improvements in transfusion burden were also observed in all evaluable patients requiring transfusions.

At a median follow-up of 195 days, most patients remained alive, with several proceeding to stem cell transplantation or continuing on background therapy. Responders to CK0804 showed reductions in circulating pro-inflammatory and pro-fibrotic mediators, decreased pathogenic monocytes in plasma and bone marrow, and normalization of bone marrow cell ratios, further supporting its potential as a novel therapeutic option.

The Orphan Drug Designation provides Cellenkos with development incentives and regulatory support as it continues to advance CK0804 toward later-stage trials for patients with myelofibrosis.