Identification of U937JAK3-M511I Acute Myeloid Leukemia Cells as a Sensitive Model to JAK3 Inhibitor

Mutated JAK3 has been considered a promising target for cancer therapy. Activating mutations of JAK3 are observed in 3.9%–10% of acute myeloid leukemia (AML) patients, but it is unclear whether AML cells are sensitive to JAK3 inhibitors, and no disease-related human AML cell model has been reported. We have identified U937 as the first human AML cell line expressing the JAK3M511I activated mutation and confirmed that JAK3 inhibitors sensitively suppress the proliferation of U937 AML cells.

Molecular modeling on the identification of potential Janus Kinase 3 (JAK3) inhibitor based on the Indonesian Medicinal Plant Database

The Janus tyrosine kinases (JAKs) have shown great promise as therapeutic protein targets in the treatment of cancer and inflammation diseases. This study used pharmacophore modeling to identify potential inhibitors of Janus kinase 3 (JAK3). A pharmacophore model was developed based on a known JAK3 inhibitor (1NX) and was employed to search for potential JAK3 inhibitors against Indonesian herbal compounds. Among 28 hit molecules that were identified and subjected to a molecular docking protocol against JAK3, the three compounds that had the highest affinities toward JAK3 were camelliaside B, 3-O-galloylepicatechin-(4beta-6)-epicatechin-3-O-gallate, and mesuaferrone B. These were then each subjected to a 50-ns molecular dynamics (MD) simulation. Analysis of RMSD and RMSF values indicated that the three compounds reached stability during the MD simulation. Interestingly, all three compounds had lower binding energies than 1NX against JAK3, as predicted by the MM-PBSA binding energy calculation.

Hair Growth Effect of Emulsion Extracted Brevilin A, a JAK3 Inhibitor, from Centipeda minima

Janus kinase 3 (JAK3) inhibitors have been used effectively in the treatment of several cases of alopecia universalis and its variants. Our study aims to evaluate whether the emulsion extract of brevilin A from Centipeda minima (CMX) stimulates hair regrowth in a clinical trial, as a JAK3 inhibitor, combined with network pharmacology-based analysis. CMX showed potent inhibition of JAK3 in a concentration-dependent manner. Significant differences in total hair count, terminal hair count, and anagen hair count from the baseline to 24 weeks were observed between the placebo and CMX subjects. The gene set enrichment analysis showed that the targets of CMX are mainly associated with the JAK-STAT signaling pathway, cytokine–cytokine receptor interactions, and the MAPK signaling pathway. This study suggests that the medicinal herbal extract CMX is useful in the treatment of mild to moderate vertex balding that contribute to the visible improvements in hair growth observed in treated patients.

Current Status in the Discovery of Covalent Janus Kinase 3 (JAK3) Inhibitors

The search for inhibitors of the Janus kinase family (JAK1, JAK2, JAK3 and TYK2) has been ongoing for several decades and has resulted in a number of JAK inhibitors being approved for use in patients, such as tofacitinib for the treatment of autoimmune diseases such as Rheumatoid Arthritis (RA). Although initially thought to be a JAK3 selective inhibitor, tofacitinib was subsequently found to possess significant activity to inhibit JAK1 and JAK2 which has contributed to some adverse side effects. A selective JAK3 inhibitor should only have an effect within the immune system since JAK3 is solely expressed in lymphoid tissue; this makes JAK3 a target of interest in the search for treatments of autoimmune diseases. A method to obtain selectivity for JAK3 over the other JAK family members, which has attracted more scientific attention recently, is the targeting of the active site cysteine residue, unique in JAK3 within the JAK family, with compounds containing electrophilic warheads which can form a covalent bond with the nucleophilic thiol of the cysteine residue. This review encompasses the historical search for a covalent JAK3 inhibitor and the most recently published research which hasn’t been reviewed to date. The most important compounds from the publications reviewed the activity and selectivity of these compounds together with some of the more important biological results are condensed in to an easily digested form that should prove useful for those interested in the field.

The Combination of Venetoclax and Tofacitinib Induced Hematological Responses in Patients with Relapse/ Refractory T-ALL with BCL2 Expression and Surface IL7R Expression or IL7R-Pathway Mutations (On behalf of the GRAALL)

Background. We previously reported that IL7R-pathway genes are mutated in 29% of T-ALL and that surface IL7R is expressed in 53% of T-ALL (Rathana K et al. abstract S131, EHA 2019). In these samples, in vitro and in vivo (IL7R+PDX T-ALL) sensitivity to JAK inhibitors is determined by the expression of IL7R regardless of the IL7Rp genomic status. BCL2 inhibition has been shown to be synergistic with the IL7R pathway inhibition (Degrise S et al., Leukemia 2018;32(3):788-800). We therefore explored whether the combination of tofacitinib, a potent JAK3 inhibitor, with venetoclax may improve the hematological status of patients with relapse/refractory T-ALL. Methods. Patients with relapse/refractory T-ALL, with surface IL7R expression or IL7R-pathway mutations and BCL2 expression were eligible if they had failed all available therapeutic options (including clofarabine and/or allogenic HSCT if eligible). Patients were offered to be treated with venetoclax, 100 mg/d day1; 200 mg/d day2; 300 mg/d day3 and 400 mg/day thereafter and for subsequent 28 days cycles combined with tofacitinib, 10mg twice a day started from day 5 cycle 1 (off-label use). Responses were assessed after cycle 1 and cycle 3. Responding patients may continue therapy until relapse, death or allogenic HSCT if eligible. Results. Eight patients were treated including 7 ETP-ALL and 1 T-cell lymphoblastic lymphoma. Median age was 56 years (27-69) and sex ratio (M/F) was 4/4. Four patients were refractory to at least 2 lines of therapy and 4 patients relapsed, all on therapy. Relapsing patients were in failure after at least one salvage therapy. All patients expressed BCL2. A mutation of JAK3 L857P was found in 5 cases including one patient with both JAK3 and JAK1 mutations. except one with a mutation of IL7-R. Other patients expressed IL7R. A response to therapy was observed in 5 out of seven evaluable cases (71%) including 2 CR associated with a negative MRD (sensitivity 10-4) and 3 partial responses (medullar blasts less than 15%). The remaining patient has just started the first cycle of therapy. Duration of responses was 10 months and +6 months (allo HSCT planned) for the 2 patients in CR and 3 months or less for the partial responders. No serious adverse event related to therapy was observed. Conclusion. IL7-pathway is a possible target for therapy with JAK inhibitors in patients with T-ALL in relapse or refractory to conventional therapy. A combination of venetoclax and tofacitinib may offer a potential savage for these patients with limited therapeutic options. Disclosures Chevallier: Daiichi Sankyo: Honoraria; Incyte: Consultancy, Honoraria; Jazz Pharmaceuticals: Honoraria. Dombret:Institut de Recherches Internationales Servier (IRIS): Research Funding; AGIOS: Honoraria; CELGENE: Consultancy, Honoraria. Boissel:NOVARTIS: Consultancy. Rousselot:Pfizer: Research Funding; Incyte: Research Funding. OffLabel Disclosure: Venetoclax in T-ALL Tofacitinib in T-ALL

Targeting Upstream Kinases of STAT3 in Human Medulloblastoma Cells

Background:Medulloblastoma is the most common malignant brain tumor in children. Despite improvement in overall survival rate, it still lacks an effective targeted treatment strategy. The Janus family of cytoplasmic tyrosine kinases (JAKs) and Src kinases, upstream protein kinases of signal transducer and activator of transcription 3 (STAT3), play important roles in medulloblastoma pathogenesis and therefore represent potential therapeutic targets.Methods:In this report, we examined the inhibitory efficacy of the JAK1/2 inhibitor, ruxolitinib, the JAK3 inhibitor, tofacitinib and two Src inhibitors, KX2-391 and dasatinib.Results:These small molecule drugs significantly reduce cell viability and inhibit cell migration and colony formation in human medulloblastoma cells in vitro. Src inhibitors have more potent efficacy than JAK inhibitors in inhibiting medulloblastoma cell migration ability. The Src inhibitors can inhibit both phosphorylation of STAT3 and Src while JAK inhibitors reduce JAK/STAT3 phosphorylation. We also investigated the combined effect of the Src inhibitor, dasatinib with cisplatin. The results show that dasatinib exerts synergistic effects with cisplatin in human medulloblastoma cells through the inhibition of STAT3 and Src.Conclusion:Our results suggest that the small molecule inhibitors of STAT3 upstream kinases, ruxolitinib, tofacitinib, KX2-391, and dasatinib could be novel and attractive candidate drugs for the treatment of human medulloblastoma.