CALR mutation

A first-in-class neutralizing antibody targeting SCUBE3, which was developed using a sophisticated antibody discovery platform and engineered with specific mutations in the heavy chain for enhanced specificity and efficacy, demonstrated profound therapeutic potential across various cancer types in preclinical models, including breast and ovarian cancer patient-derived xenografts. This discovery marks an advancement toward developing a targeted therapy for cancers characterized by hyperactive SCUBE3-associated signaling pathways.

Loss of CXCR4+ HSCs skewed lineage differentiation of HSCs toward the myeloid lineage, whereas restoring this subset delayed the onset of ET. Altogether, this study reveals both the shared and distinct molecular features of mutant HSCs in ET and provides novel insights into the pathogenesis and potential therapeutic strategies of ET.

Early-phase clinical trials with fully human anti-CALR monoclonal antibodies (e.g., INCA033989) have shown very promising hematologic and molecular responses with manageable toxicity...At the same time, the complexity of CALR-driven disease raises key questions, including whether anti-CALR therapies can shift treatment goals beyond thrombotic risk reduction, how best to monitor clonal burden, and how to address immune escape. In this review, we highlight the latest therapeutic advances in CALR-mutated MPNs while outlining the critical unmet needs that will shape the future of care for these patients.

CH-defined by the JAK2V617F and CALR mutations-was associated with cancer, MPN, all-cause mortality-even with VAF < 1%-and vascular diseases at VAF ≥ 1%. These are novel findings, indicating that the JAK2V617F and CALR mutations confer an oncogenic potential with a VAF below the current CH of indeterminate potential definition.

Furthermore, CALR WTΔKDEL conferred mutant CALR sensitivity to MPL by recognizing the N-glycans of MPL while maintaining it in an immature form, which may bind to mutant CALR. In conclusion, deletion of the ER retention signal KDEL from CALR is a prerequisite for the expression of the immature form of MPL, which can interact with secreted mutant CALR.

Multivariate analysis indicated that in ruxolitinib-treated patients with myelofibrosis, poor overall survival was independently predicted by increased age, reduced hemoglobin, percentage of bone marrow blasts ≥ 1%, absence of JAK2 mutations, chromosomal abnormalities, ≥2 high-molecular-risk mutations, and TP53 mutations. Patients with myelofibrosis stratified by age exhibited heterogeneous clinical features and gene mutation profiles but similar efficacy of ruxolitinib treatment and occurrence of adverse events.

This study provides comprehensive regulatory mechanisms of CALR across various cancer types and introduces research advances of wild-type and mutant CALR-binding compounds. By critically evaluating structural binding motifs, pharmacological efficacy and clinical limitations of existing ligands, our research offers new perspectives to guide future CALR-directed therapeutic discovery and optimization.

Finally, we review ongoing clinical and preclinical experimental approaches for targeting mutant CALR in MPN in a clonally selective manner using monoclonal antibodies, bispecific antibodies, cancer vaccination, chimeric antigen receptor T cells, and antibody-drug conjugates. Taken together, we expect that ongoing developments in mutant CALR-targeted therapeutics will lead to promising novel strategies for long-term disease control.

One patient affected by CALR mutated essential thrombocytopenia, had a small clone (0.52%), clinically irrelevant; one patient affected by JAK2V617F primary myelofibrosis (PMF) showed a PNH clone of 89.8%, severe anemia and hemoglobinuria and started eculizumab therapy; the third patient affected by CALR mutated PMF showed a PNH clone of 92.6% but without severe anemia and breakthrough hemolysis and eculizumab therapy was not undertaken. PIGA deletion was detected in PNH-positive cases along with mutations of myeloid-related genes. These data seem to suggest an association of CALR mutation and JAK2V617F mutation with PNH positive clones suggesting that the worsening of malignant process may be associated with the acquisition of multiple genetic mutations.Clinical Trial Registration: NCT06159816.

MPN transformation involves complex clonal evolution, with frequent clonal hematopoiesis-related mutations preceding driver mutations, preserved CALR, acquisition of TP53, RUNX1 and signaling mutations, and JAK2-V617F loss linked to poorer survival during BP transformation, which may influence therapeutic decisions.

Created in BioRender. Bauer, M. (2025) https://BioRender.com/h133y7w .

Additionally, cMPL mutation was not found among our patients. The four analyzed mutations are among the diagnostic criteria established by the World Health Organization, which enable a quick and reliable diagnosis of MPN.