CRLF2 overexpression

The utilization of RNA-seq enables the identification of clinically significant genetic abnormalities that may go undetected through conventional detection methods. Its robust analytical performance might bring great application value for clinical diagnosis, prognosis, and therapy in ALL.

High Resolution Melting analysis unveiled concurrent CRLF2 or JAK2 variants in 8.19% of samples, as well as a dynamic nature of CRLF2 alterations during disease progression. Overall, this approach provides an accurate identification of CRLF2 alterations, enabling improved diagnostic and facilitating therapeutic decision-making.

Such heterogeneity was attributed to the different molecular mechanisms leading to CLRF2 upregulation, where the CRLF2 overexpression level was high in Ph-like B-ALL and medium in high hyperdiploid B-ALL. This study highlights the importance of the molecular mechanisms of the upregulation of CRLF2 expression in predicting the prognosis of pediatric B-ALL patients.

Pts received hyper-CVAD alternating with high-dose methotrexate (MTX) and cytarabine (Ara-C) for up to 4 cycles, followed by 4 cycles of blinatumomab at standard doses. Pts with CD20+ disease (≥1% cells) received 8 doses of ofatumumab (2000 mg) or rituximab (375 mg/m2)...One pt discontinued blinatumomab due to a related adverse event (grade 2 encephalopathy and dysphasia). No pts discontinued INO due to toxicity, and no cases of veno-occlusive disease have been observed.

Cell apoptosis assays demonstrated the CRLF2-dependent potency of CRLF2-DM1 LIP in Ph-like ALL cell lines. This study is the first to highlight the therapeutic potential of a CRLF2-directed scFv-Fc-liposomal conjugate for targeting Ph-like ALL.

Patients with DS-ALL exhibit an increased rate of relapse and particularly of treatment-related mortality. Novel, less-toxic therapeutic strategies are needed to improve outcomes.

Furthermore, concomitant CNA of IKZF1 in CRLF2 positive patients was associated with a greater hazard for poor overall and event free survival, compared to patients without these alterations or presence of any one of them. Our findings demonstrate that the surface CRLF2 expression in association with IKZF1 copy number alteration can be used to risk stratify pediatric B-ALL patients.

With this practical approach, we reported a high incidence of BCR::ABL1-like ALLs, and a lower frequency of CRLF2 alteration & associated CGFs. Recognising this entity, early at diagnosis is crucial to optimise personalised treatment strategies.

However, long-term efficacy remains to be determined and it is under evaluation in clinical trials.1,22,23 Preclinical and more recent clinical studies have shown variable activity of JAK inhibitors in JAK-STAT activating ALL17,24 and the need to simultaneously inhibit multiple pathways, including phosphoinositide 3-kinase (PI3K)/mTOR or mitogen-activated protein kinase (MEK)/ receptor tyrosine kinases (e.g. FLT3) to block the growth of leukemic blasts.25–27 Promising alternative approaches to TKIs are represented by antibody-based (e.g. blinatumomab or inozutumab) and cellular (CAR T-cell therapy) immunotherapy which have shown discernable efficacy in BCR::ABL1-like ALL among other subtypes.28–30 Moreover, the efficacy of proteolysis-targeting chimeras (PROTACs) directed against JAK231 or GSPT1/2 degraders32 has been recently reported in preclinical models of CRLF2-rearranged and other JAK-activated BCR::ABL1-like ALL. Conclusions BCR::ABL1-like ALL is driven by numerous targetable kinase fusions whose diagnosis requires the use of comprehensive assays. The incorporation of TKIs and/or different immunotherapies is reversing the historically poor outcome of this ALL subtype.

Notably, ex vivo drug screening revealed sensitivity of IKZF1plus blasts for drugs active against Ph-like ALL such as Birinapant and histone deacetylase inhibitors. We provided data in a large setting of a rare condition (DS-ALL) supporting that these patients, not associated with other high-risk features, need tailored therapeutic strategies.