Efficacy of the kinase inhibitor CHZ868 against JAK2 rearrangements in pediatric acute lymphoblastic leukemia

B-cell precursor acute lymphoblastic leukemia (BCP-ALL) is the most frequent subtype of acute lymphoblastic leukemia (ALL), the most common pediatric cancer.¹ Nowadays the improvement of chemotherapy protocols led patients to an event-free survival of 85%, while 15% of patients still relapse, with only 20-45% cure rate by second line therapies.² The group named Philadelphia-like (Ph-like) or BCR::ABL1-like³, recently included in the World Health Organization as associated to high-risk of relapse,⁴ has been defined to have a genetic expression pattern similar to Philadelphia-positive ALL, despite not having the underlying BCR::ABL1 fusion. In 90% of cases alterations of ABL1/ABL2, PDGFRB/A, CSF1R, CRLF2, PAX5, EPOR, and JAK2 genes are included in this subgroup.^5-6

JAK2 is a non-receptor tyrosine kinase, involved in hematopoiesis, signaling pathways and cellular processes, and known to be deregulated in leukemias, lymphomas and myeloproliferative neoplasms.^4,7 JAK2 rearrangements (JAK2r) are found in 5% of pediatric Ph-like ALL,^4,5,8 representing an appealing target of tyrosine kinase inhibitors (TKI).⁴ In the last few years, the production of type-II TKI has increased, as they can overcome the limits of type-I TKI by targeting the active form of JAK2. Ruxolitinib is the most used type-I TKI, but despite its efficacy, also in combination approaches, it has shown some limitations, as hyperphosphorylation of JAK2/STAT and loss of response that determine the “paradoxical effect” of increasing JAK2 activation.^9-10 Vice versa, type-II TKI bind their target in the inactive conformation, covering regions adjacent to the ATP-binding site, with an advantage in efficacy.¹¹ Interestingly, the novel type-II TKI CHZ868 showed promising results in vitro and in vivo, in the presence of CRLF2 rearrangements in BCP-ALL patient-derived xenografts (PDX).^{9 ,1 1} The preliminary CHZ868 efficacy prompted us to develop the present preclinical study with the aim of targeting JAK2r in pediatric BCP-ALL.

Primary samples of pediatric patients affected by BCP-ALL have been collected and analyzed, in accordance with the ethical standards of the Declaration of Helsinki and following national and international guidelines. We applied the next-generation sequencing (NGS) RNA target capture strategy implementing either the Illumina TruSight RNA Pan-Cancer Library Prep or the Nugen Custom Panel, as previously described.¹² An in vivo PDX model has been set up in immunodeficient NOD.Cg-Prkdc^scid Il2rg^tm1Wjl/SzJ (NSG) mice to expand primary patients’ bone marrow (BM) samples. Cells derived from PDX were both co-cultured on a layer of human bone marrow stroma (HBMS) for apoptosis/viability assays and analyzed by HTP drug screening, as previously described.^6,13 Phosphoflow on PDX-derived blasts was performed at basal level or after drugs treatment.⁶ We treated PDX with leukemic blasts carrying PAX5::JAK2, ATF7IP::JAK2 or ZEB2::JAK2 fusions, with either CHZ868 or vehicle. After in vivo treatment, whole transcriptome analysis has been performed by Universal RNAseq kit and FASTQ files are available in the BioStudies database (https://www.ebi.ac.uk/biostudies/) under accession E-MTAB-15657.

Twelve pediatric JAK2r cases (mean age 9.6 years) were identified by RNA sequencing screening of 895 (1.3%) BCP-ALL pediatric patients at diagnosis (Online Supplementary Figure S1A). ZEB2::JAK2, GIT2::JAK2, TLE4::JAK2 and MPRIP::JAK2 were validated as novel fusions, beside the known BCR::JAK2, ATF7IP::JAK2 and PAX5::JAK2 (6/12 cases). In all cases, JAK2 maintains its kinase domain at the 3’, joined with the 5’ partner gene (data not shown). We developed PDX from three representative patients, carrying PAX5::JAK2 (patient 1), ATF7IP::JAK2 (patient 2) and ZEB2::JAK2 (patient 3) fusion, respectively (Online Supplementary Figure S1B, C).

The constitutive basal phosphorylation of Y1007-1008 residues in the loop of activation of JAK2 in all three JAK2r cases was significantly higher than the negative controls. PAX5::JAK2 and ZEB2::JAK2 had also higher pJAK2 than positive controls, known to have an active JAK/STAT pathway, while in ATF7IP::JAK2 pJAK2 was comparable to positive controls (range +17%/+70%; 0.05<P<0.01) (Online Supplementary Figure S1D). JAK2 constitutive activation induced the basal activation of pSTAT5(Y694) in all JAK2r, while no difference in pSTAT3(S727) expression was found among PAX5::JAK2, positive and negative controls, whereas pSTAT3 was unexpectedly significantly higher in ATF7IP::-JAK2 and ZEB2::JAK2 (Online Supplementary Figure S1D). CHZ868 monotherapy treatment (up to 60 minutes), given at 50% lethal dose (LD₅₀) patient-specific doses (Figure 1A), showed a higher specificity and efficacy towards pJAK2(Y1007-1008) than ruxolitinib monotherapy treatment (30 minutes: CHZ868-33%/-71%; 0.01<P<0.001 vs. ruxolitinib 5%/-24%; not significant [NS]<P<0.05). Vice versa, ruxolitinib showed higher efficacy on pSTAT5 than CHZ868 (30 minutes: ruxolitinib -27%/-62%; 0.05<P<0.01 vs. CHZ868-12%/-52%; 0.05<P<0.01). Interestingly, both drugs had a comparable significant effect on pSTAT3. The percent of reduction is indicated as a range of the three patients analyzed.

Figure 1.Targeting of JAK2-rearranged patient-derived xenografts with tyrosine kinase inhibitors from short time points to 48 hours in co-culture on human bone marrow stroma, to evaluate both the phosphorylation levels on JAK2/STAT and PI3K-AKT pathways by phosphoflow, and ex vivo apoptosis/viability of drug pair combinations, given at three different dosages for 48 hours on PAX5::JAK2 blasts in co-culture with human bone marrow stroma. Viability was assessed by Annexin V/7AAD staining (Annexin V/7AAD double-negative hCD10⁺ blasts). (A) Heatmap representing the ratios of mean fluorescence intensity (MFI) of CHZ868-treated (LD₅₀ dosage) or ruxolitinib-treated (50% lethal dose [LD₅₀] dosage) on vehicle-treated hCD10⁺ blasts of pJAK2 (Y1007-1008), pSTAT5 (Y694) and pSTAT3 (S727), at short time points (5-60 minutes [min]) of treatment on patient-derived xenograft (PDX)-derived blasts carrying a PAX5::JAK2 fusion (left 3 columns), on PDX-derived blasts carrying a ATF7IP::JAK2 fusion (central 3 columns) and on PDX-derived blasts carrying a ZEB2::JAK2 fusion (right 3 columns). N=3 experiments. Error bars represent standard deviation (SD). Student’s t test is shown as P values: *P<0.05; **P<0.01; ***P<0.001. Statistics reported in white refers to a significant reduction of phosphorylation in treated blasts compared to untreated blasts, while statistics reported in black refers to a significant increase of phosphorylation in treated blasts compared to untreated blasts. The internal control is represented by untreated cells (0 min). (B) Heatmap representing MFI ratios of 48-hour (h) tyrosine kinase inhibitor (TKI)-treated on vehicle-treated hCD10⁺ PDX-derived blasts on human bone marrow stroma (HBMS) co-culture carrying a PAX5::JAK2 fusion (left 3 columns), on PDX-derived blasts carrying a ATF7IP::JAK2 fusion (central 3 columns) and on PDX-derived blasts carrying a ZEB2::JAK2 fusion (right 3 columns) reporting the inhibition of pJAK2 (Y1007-1008), pSTAT5 (Y694) and pSTAT3 (S727). N=3 experiments, in technical duplicate. Error bars represent SD. Student’s t test is shown as P values: *P<0.05; **P<0.01; ***P<0.001. Statistics reported in white refers to a significant reduction of phosphorylation in treated blasts compared to untreated blasts, while statistics reported in black refers to a significant increase of phosphorylation in treated blasts compared to untreated blasts. The internal control is represented by untreated cells. (C) Heatmap representing MFI ratios of 48-h TKI-treated on vehicle-treated hCD10⁺ PDX-derived blasts on HBMS co-culture carrying a PAX5::JAK2 fusion (left 5 columns), on PDX-derived blasts carrying a ATF7IP::JAK2 fusion (central 5 columns) and on PDX-derived blasts carrying a ZEB2::JAK2 fusion (right 5 columns) reporting the inhibition of PI3K-AKT pathway effectors (PDPK1, pAKT [S473], pAKT [T308], 4pEBP1, pS6). N=3 experiments, in technical duplicate. Error bars represent SD. Student’s t test is shown as P values: *P<0.05; **P<0.01; ***P<0.001, ****P<0.0001. The internal control is represented by untreated cells. Statistics reported in white refers to a significant reduction of phosphorylation in treated blasts compared to untreated blasts, while statistics reported in black refers to a significant increase of phosphorylation in treated blasts compared to untreated blasts. The internal control is represented by untreated cells. (D) Ex vivo viability of hCD10⁺ PDX-derived blasts on HBMS co-culture after 48-h drug combinations on PAX5::JAK2-positive blasts, indicating the decrease of viable blasts while increasing the dosages (CHZ868: 0.193 μM, 0.270 μM, 0.347 μM; ruxolitinib: 24 μM, 32 μM, 40 μM; dexamethasone: 5 ng/mL, 7 ng/mL, 9 ng/mL). Viability was assessed from apoptosis and necrosis after staining with Annexin V-PE/7AAD and expressed as decrease of the percentage of hCD10⁺ viable blasts (Annexin V-PE/7AAD double-negative cells) and expressed as percentage of viability on untreated cells. N=3 experiments, in technical duplicate. Error bars represent SD. The internal control is represented by untreated (ut) cells. Student’s t test is shown as P values: *P<0.05; **P<0.01; ***P<0.001; ****P<0.0001. (E) Ex vivo viability of hCD10⁺ PAX5::JAK2 blasts in co-culture on HBMS after 48 h of treatment of BIBF1120-CHZ868 (left graph) and BIBF1120-ruxolitinib (right graph) combinations. Viability was assessed from apoptosis and necrosis after staining with Annexin V-PE/7AAD and expressed as decrease of the percentage of hCD10⁺ viable blasts (Annexin V-PE/7AAD double-negative cells) and expressed as percentage of viability on untreate cells. N=3 experiments, in technical duplicate. Error bars represent standard deviation. The internal control is represented by untreated (ut) cells. Student’s t test is shown as P values: *P<0.05; **P<0.01; ***P<0.001.

After 48 hours (h) of treatment with CHZ868 or ruxolitinib of blasts in co-culture on a layer of HBMS, ruxolitinib showed no effect on pJAK2 on both PAX5::JAK2 and ATF7IP::JAK2, while inhibiting pSTAT5 only in ATF7IP::JAK2 and ZEB2::JAK2. Instead, ATF7IP::JAK2 and ZEB2::JAK2 showed a significant decrease in pJAK2 (-25%/-50%; 0.01<P<0.001) and pSTAT5 (-20%/-65%; 0.001<P<0.0001) after CHZ868 treatment. Even though pJAK2 was significantly reduced (-40%; P<0.001), pSTAT5 became hyperphosphorylated in PAX5::JAK2 after both CHZ868 (+200%; P<0.001) and ruxolitinib (+50%; P<0.001) treatment. To note, both drugs had a strong effect on pSTAT3 (-50%; P<0.0001) only in ATF7IP::JAK2, a new observation for JAK2 inhibition in BCP-ALL (Figure 1B). Overall, CHZ868 and ruxolitinib significantly (and similarly) inhibited PI3K-AKT pathway’s effectors (Figure 1C).

After 48 h of CHZ868 treatment in combination with dexamethasone and ruxolitinib, a statistically significant and synergistic effect was assessed at LD₅₀ dosage with ruxolitinib in ATF7IP::JAK2 and ZEB2::JAK2, while the combination was additive in PAX5::JAK2 (-62%/-90%; 0.01<P<0.001). While ATF7IP::JAK2 and ZEB2::JAK2 showed resistance to dexamethasone, PAX5::JAK2 resulted sensitive, as also supported by the statistically significant synergy between dexamethasone and CHZ868 (-95%; P<0.001). While CHZ868 did not overcome dexamethasone resistance in ATF7IP::-JAK2, a synergistic effect was observed in ZEB2::JAK2, as in ruxolitinib and dexamethasone combination (Figure 1D; Online Supplementary Figure S1E).

Moreover, we confirmed PI3K pathway activation, downstream LCK, which is a known target of PAX5,⁶ in PAX5::JAK2 (Online Supplementary Figure S1F, L). We further demonstrated that the triple kinase inhibitor nintedanib (BIBF1120)⁶ is efficacious on PAX5::JAK2 blasts on HBMS, both by the inhibition of PI3K-AKT pathway effectors (Online Supplementary Figure S2A) and by its apoptosis induction, with an additive effect in combination with both CHZ868 (-64%; P<0.001) and ruxolitinib (-50%; P<0.05) (Figure 1E). Bliss score and combination index of drugs’ combinations are reported in Online Supplementary Figure S2B. We also assessed the specific action of drugs on negative (w/o fusions) and positive controls (CRLF2r/JAK2m and CRLF2r only) (Online Supplementary Figure S2C, E).

Figure 2.High-throughput drug screening with co-culture validation on patient-derived xenografts carrying JAK2 rearrangements and in vivo CHZ868 targeting of xenotransplanted NSG mice with blasts carrying JAK2 rearrangements. (A) Unsupervised clustering of N=4 JAK2r blasts, one positive control (MUTZ5 cell line) and 6 healthy controls (N=3 T-cells, N=3 peripheral blood mononuclear cells [PBMC]) expressing their drug sensitivity score (DSS) values. DSS reported values are proportional to the efficacy of a group of standard chemotherapy drugs currently used in the AIEOP BFM 2017 protocol, a group of inhibitors known to target JAK, in addition to venetoclax and obatoclax (BLC2i) and omaveloxolone (NFKBi). Box plots represent the mean DSS ± standard deviation (SD) distribution among the samples for each column. (B) Ex vivo viability of hCD10⁺ patient-derived xenograft (PDX)-derived blasts on human bone marrow stroma (HBMS) co-culture after 48-hour (h) drugs combinations of AT9283 and CHZ868, tested at 3 different dosages including their patient-specific 50% lethal dose (LD₅₀), on PAX5::JAK2 PDX-derived blasts. Viability was assessed from apoptosis and necrosis after staining with Annexin V-PE/7AAD and expressed as decrease of the percentage of hCD10⁺ viable blasts (Annexin V-PE/7AAD double-negative cells) and expressed as percentage of viability on untreated cells. N=3 experiments, in technical duplicate. Error bars represent (SD). The internal control is represented by untreated (ut) cells. Student’s t test is shown as P values: *P<0.05; **P<0.01; ***P<0.001; ****P<0.0001. (C) Evaluation of the safety/ toxicity of standard chemotherapy, JAK inhibitors (JAKi), BCL2 inhibitors (BCL2i) and NF-κB inhibitors (NF-κBi) on CD34⁺ hematopoietic stem cells (HPSC) purified from N=3 healthy donors, expressed as DSS value. DSS<10 was set as a stringent cutoff for no toxicity. (D) Evaluation of the reduction of the percentage of hCD10⁺CD19⁺ leukemic blasts in CHZ868-treated NSG mice compared to vehicle-treated mice, in bone marrow, spleen, peripheral blood and meninges of central nervous system (CNS), and reduction of spleen weight, in the setting of PAX5::JAK2 fusion. At least N=5 mice for each group, treated for 10 days with washout at the weekend. Error bars represent SD. Student’s t test is shown as P values: *P<0.05; **P<0.01; ***P<0.001; ****P<0.0001; *****P<0.00001.

To resolve the ruxolitinib efficacy limited to high dosages, with loss of specificity towards pJAK2, we applied an ex vivo high-throughput drug screening with alternative 174 inhibitors, including 110 Food and Drug Administration/ European Medicines Agency-approved drugs, as previously described.¹³ PAX5::JAK2, ATF7IP::JAK2, ZEB2::JAK2 and GIT2::JAK2 PDX were tested, aiming to identify additional compounds to be combined with CHZ868 with synergistic effect. After 72 h of treatment (8 nM to 25 uM), we compared the differential drug sensitivity score (dDSS)¹⁴ of the JAK2r PDX with MUTZ5 cell line (CRLF2r and JAK2m) and healthy donors (T cells and PBMC). As reported in Figure 2A, among JAK2r PDX, PAX5::JAK2 PDX-derived blasts were the most sensitive to several drugs, including currently used drugs in the AIEOP-BFM ALL 2017 pediatric protocol, and JAK TKI. We identified drugs not belonging to selective JAK inhibitors, but specific for the JAK2r cohort and safe on healthy controls, such as birinapant (Smac mimetic; P<0.05). Among the JAK TKI, ruxolitinib was not effective on JAK2r, while AT9283 was the most specific and effective on JAK2r (P<0.05), with no effect either on MUTZ5 or healthy controls. In 48 h ex vivo HBMS co-culture of three JAK2r PDX, AT9283 combined with CHZ868 exerted a significant increase in the apoptotic effect compared to monotherapy (P<0.0001; Figure 2B; Online Supplementary Figure S2F) with synergistic (in PAX5::JAK2, ZEB2::JAK2) or additive (in ATF7IP::JAK2) effect at LD₅₀ (Online Supplementary Figure S2G). To note, not only CHZ868 (range, 8 nM to 25 µM) demonstrated to be non-toxic on hematopoietic stem and progenitor cells (HSPC, CD34⁺) (Online Supplementary Figure S2H), but we also demonstrated the safety of AT9283, ruxolitinib and birinapant, on HSPC purified from healthy donors, having a DSS<10, determined as cut-off for safety/toxicity evaluation¹³ (Figure 2C).

We also demonstrated the in vivo efficacy of CHZ868 in three JAK2r PDX models. First, all three JAK2r CHZ868-treated mice groups showed a significant reduction of pJAK2 (-18%/-30%; P<0.05) and pSTAT5 (-23%/-45%; P<0.05) (Online Supplementary Figure S2I), while PI3K pathway was not affected (Online Supplementary Figure S2L). Importantly, after 2 weeks of treatment at 30 mg/kg, we detected a statistically significant reduction of the hCD10⁺CD19⁺ percentage of blasts in the hematopoietic organs, as bone marrow (-43%/-85%; 0.05<P<0.01), spleen (-72%/-89%; 0.05<P<0.00001) associated with spleen weight reduction (-37%/-60%; 0.001<P<0.00001), and peripheral blood (-46%/-80%; P<0.05) (Figure 2D; Online Supplementary Figure S3A).

To deeply understand the CHZ868 mechanism of action downstream JAK2r, we performed whole transcriptome NGS on RNA extracted from CHZ868-treated versus vehicle-treated mice (Online Supplementary Figure S3B). The TKI treatment reduced JAK2 expression in CHZ868-treated mice (Online Supplementary Figure S3C) and KEGG analysis indeed confirmed downregulation of JAK/STAT signaling and pluripotency of stem cells pathways; however, different metabolic pathways were activated, as part of the metabolic rewiring of blasts (Figure 3A). By Hallmark gene set enrichment analysis (GSEA), we observed an enrichment in MYC targets and metabolic rewiring (MTORC1 signaling, glycolysis and unfolded protein response), while JAK/ STAT3/STAT5 signaling, KRAS signaling, and inflammatory responses resulted downregulated (Figure 3B). We confirmed a cell cycle arrest of CHZ868-treated blasts as a consequence of proliferation suppression (downregulation of RB1, E2F7/8, CCNE1/2, CDC25B and MKI67) due to DNA damage (upregulation of TP53 and CDKN1A) induced by JAK/ STAT inhibition, conferring a quiescent state (upregulation of ORC5 and CCND3) (Figure 3C; Online Supplementary Figure S3D). Since DNA damage was previously demonstrated to induce strong NF-κB activation, we indeed confirmed that CHZ868 treatment led to upregulation of canonical NF-κB pathway (upregulation of IKBKB and TNFRSF1A; downregulation of CYLD, NFKBIE and RELB), denoted by immune evasion or reduced inflammation (downregulation of TLR2/7, IL1RAP and TNFRSF11A) with dominance of anti-apoptotic stimuli (upregulation of BCL2 and BIRC3) (Figure 3D; Online Supplementary Figure S3E). Furthermore, we confirmed that the differentially expressed genes were indeed more correlated to anaerobic metabolic rewiring in stress conditions (ribosomal machinery, mitochondrial biogenesis, amino acids metabolism) rather than proliferation (Online Supplementary Figure S3F).

Figure 3.Pathways enrichment and differential gene expression analyses in CHZ868-treated mice. (A) KEGG pathway gene set enrichment analysis (GSEA) performed on transcriptomic data from CHZ868-treated (CHZ) mice. The dot plots display significantly activated (left column) or suppressed (right column) pathways expressed by gene ratio based on normalized enriched score (NES<0 downregulation, NES>0 upregulation) and ranked by adjusted P value (color scale), with dot size representing the number of genes per pathway (count). Pathways with adjusted stringent P value<0.02 were considered significantly enriched. GSEA was performed using the R clusterProfiler package. (B) Hallmark pathway GSEA performed on transcriptomic data from CHZ868-treated mice. The dot plots display significantly activated (left column) or suppressed (right column) pathways expressed by gene ratio based on normalized enriched score (NES<0 downregulation, NES>0 upregulation) and ranked by adjusted P value (color scale), with dot size representing the number of genes per pathway (count). Pathways with adjusted P value <0.05 were considered significantly enriched. GSEA was performed using the R clusterProfiler package. (C) Differential gene expression analysis between CHZ868-treated mice (box plots in red, 4 samples each) and vehicle-treated mice (box plots in blue, 4 samples each) on genes associated with proliferation. Six of the top significantly upregulated and downregulated genes (adjusted P value<0.05), with expression levels represented as log₂(FPKM+1), are reported in the figure. P values are derived from permutation-based Wilcoxon tests (10,000 permutations). (D) Differential gene expression analysis between CHZ868-treated mice (box plots in red, 4 samples each) and vehicle-treated mice (box plots in blue, 4 samples each) on genes associated with NF-κB pathway. Nine of the top significantly upregulated and downregulated genes (adjusted P value<0.05), with expression levels represented as log₂(FPKM+1), are reported in the figure. P values are derived from permutation-based Wilcoxon tests (10,000 permutations).

In this study on a limited cohort of JAK2-rearraged cases, we aimed at exploring the targeting of JAK2 rearrangements in leukemia by using the murine expansion of primary blasts from patients as a preferential model over cell lines, a limiting and confounding model. We demonstrated in our preclinical model that JAK2r PDX have constitutive basal activation of JAK2/STAT5 pathway, that can be efficiently targeted both in ex vivo and in vivo treatment by CHZ868, a novel type-II TKI, in addition to a not usually described pSTAT3 downregulation after JAK2 inhibition in JAK2r. CHZ868, already effective ex vivo at 100-fold lower dosages than ruxolitinib, the most used TKI, proved to induce apoptosis in synergic or additive combination with other kinase inhibitors, standard chemotherapy or chimeric antigen receptor T-cell therapy.¹⁵ CHZ868 was even able to overcome dexamethasone monotherapy resistance in a model recapitulating 2D BM niche.

Moreover, our HTP drug screening showed JAK2r PDX sensitivity to other classes of drugs, as venetoclax (BCL2i) and omaveloxolone (NF-κBi), which may be used to target activated vulnerabilities (BCL2, effectors of NF-κB pathway) due to CHZ868-induced DNA damage. Combinatorial approaches of type-II JAK2i would be beneficial in clinics to overcome eventual limitations or resistance mechanisms induced by TKI treatment. Importantly, the proposed drugs and compounds proved to be non-toxic on healthy cells, including HSPC, thus supporting their potential use in JAK2r BCP-ALL in combination with clinically optimized type-II TKI, not included in this study.

Although CHZ868 itself cannot be clinically developed due to its unfavorable pharmacokinetic properties, our findings provide proof-of-principle evidence that type-II JAK2 inhibition is highly effective in JAK2-rearranged pediatric BCP-ALL. Our data support further preclinical and clinical development of clinically suitable type-II JAK2 inhibitors for this high-risk subgroup.

Footnotes

• Received May 8, 2025
• Accepted April 9, 2026

Correspondence

G. CAZZANIGA - giovanni.cazzaniga@unimib.it

G. FAZIO - grazia.fazio@unimib.it

Disclosures

No conflicts of interest to disclose.

Contributions

Funding

This work was supported by Fondazione AIRC per la ricerca sul cancro (project numbers 2022-28342 [to MQ] and IG2023-29191 [to GF]), the Italian Ministry of Health, Fondazione Cariplo (project number 2018-0339 [to CP] and supporting MQ fellow). SB was supported by the “Elterninitiative Kinderkrebsklinik e.V.”. ABo was supported by the “Katharina-Hardt-Foundation, Bad Homburg, Germany”.

Acknowledgments

We deeply thank “Fondazione Maria Letizia Verga” for supporting MQ and the research project. We thank Novartis that signed the MTA to provide us with CHZ868.