Page 238 - 2021_10-Haematologica-web

Letters to the Editor
ALL PDX mice were randomized upon >1% peripheral blood engraftment to treatment with vehicle, ponatinib 25 mg/kg orally once daily for 5 days/week, rux- olitinib 2 g/kg chow orally ad libitum, or both ponatinib and ruxolitinib for 2-4 weeks depending upon rate of leukemia progression in control animals requiring sacrifice. Human CD10+/CD19+/CD45+ ALL cells were assessed weekly in murine retro-orbital venous peripheral blood (left panels) and end-study spleens by quantitative flow cytometry analysis as described.9-11 Combination ponatinib and ruxolitinib treatment induced superior inhibition of leukemia proliferation ver- sus tyrosine kinase inhibitors (TKI) monotherapies in all three tested models. Flow cytometry analysis was performed in Cytobank. Statistical analysis and data display were performed in Prism (*P<0.05, **P<0.01, ***P<0.001, ****P<0.0001 by two-way [blood] or one-way [spleen] ANOVA with Dunnett’s post-test for multiple comparisons).
and viability analyses of banked diagnostic ALL cells demonstrating preferential sensitivity to ponatinib and ruxolitinib (Figure 1C and D). Ponatinib was increased to 30 mg twice-daily given persistent mid-induction 1B/consolidation MRD 3.4%, which did not improve by end-1B/consolidation (TP2) with MRD 3% (Figure 1B). Chemotherapy-associated complications included vin- cristine-induced peripheral neuropathy, steroid-induced hyperglycemia, and mild transaminitis and coagulation parameter impairment. The patient then received one cycle of blinatumomab with continued ponatinib and achieved negative MRD (<10-5) prior to receipt of MSD allogeneic HSCT in May 2019, which was complicated by mild chronic oral and vaginal GvHD. Ponatinib 30 mg daily was begun at day +80 post-HSCT. She remains in continued MRD-negative remission and completed pona- tinib maintenance therapy in May 2021 at 2 years post- transplant.
Given observed decreased MRD in these three high- risk patients treated with ruxolitinib or ponatinib and post-induction chemotherapy or immunotherapy, we conducted additional in vitro and in vivo laboratory studies to confirm and isolate the therapeutic potential of the specific TKI without multi-agent chemotherapy in IGH-EPOR Ph-like ALL PDX models (performed as described9-11). Primary B-ALL specimens used in these studies were obtained via COG or institutional biobank- ing research protocols via informed consent in accor- dance with the Declaration of Helsinki. PDX model stud- ies were conducted via Institutional Animal Care and Use Committee-approved research protocols. We detected increased FC surface EPOR staining in two of three IGH-EPOR ALL PDX models versus non-EPOR- rearranged B-ALL NALM-6 (non-Ph-like) and MUTZ5 (CRLF2-rearranged Ph-like) cells (Figure 2A), as well as TKI-induced inhibition of erythropoietin-stimulated sig- naling in vitro via phosphoflow cytometry analyses (Figure 2B). As predicted,5,11 ponatinib or ruxolitinib monotherapy potently inhibited in vivo leukemia prolifer- ation in two pediatric IGH-EPOR ALL PDX models (PAVRCK, PAVDRS) with superior activity observed with dual TKI treatment (Figure 2C). Interestingly, we also saw partial single-agent ponatinib and ruxolitinib activity in a third PDX model (MDACC3) established from an adult with relapsed IGH-EPOR ALL who was resistant to ruxolitinib 25 mg twice-daily and hyper-CVAD (cyclophosphamide, vincristine sulfate, doxorubicin hydrochloride, and dexamethasone) chemotherapy on an institutional phase II/III clinical trial (clinicaltrials gov. Identifier: NCT02420717).12 As in the de novo pediatric ALL PDX models, combined ponatinib and ruxolitinib more potently reduced leukemia burden in end-study murine spleens versus TKI monotherapy (Figure 2C), although this relapsed adult ALL model’s lack of LDA positivity or increased FC EPOR surface staining remains puzzling given our confirmation of IGH-EPOR fusion by both FISH and ArcherDX FusionPlex analyses. The previ- ously-unknown sensitivity of IGH-EPOR Ph-like ALL to ponatinib in our preclinical PDX models and potentially clinically in patient H25648 is consistent with the
observed sensitivity of CRLF2-rearranged Ph-like ALL to the SRC/ABLi dasatinib recently reported by our group.11 We posit that IGH-EPOR Ph-like ALL may also be driven by activated BCR-like and associated downstream SRC family kinase signaling in addition to known constitutive JAK/STAT signaling that merits further study.
Leukemia-associated IGH-EPOR fusions were first reported in 2009 by Russell and colleagues in a child with newly-diagnosed B-ALL transplanted in first remission for chemoresistance and in a young adult with very early medullary-relapsed B-ALL who underwent HSCT in sec- ond remission after salvage chemotherapy.13 Recent analyses of large cohorts of often-cytogenetically-cryptic high-risk childhood and adult B-ALL cases identified 3’ EPOR rearrangements most commonly with 5’ fusion partner immunoglobulin heavy locus (IGH) and less com- monly with light chain genes immunoglobulin k (IGK) and immunoglobulin λ (IGL) or leukocyte-associated immunoglobulin-like receptor (LAIR) and associated kinase-activated Ph-like gene expression profiles.2-4 Our study confirms the clinically high-risk nature of IGH-EPOR Ph-like ALL in three AYA patients, all of whom had high end-induction MRD and two of whom required post-consolidation immunotherapy and allo- geneic HSCT to overcome chemoresistance. While cur- rent clinical trials are assessing the potential efficacy of ruxolitinib addition to chemotherapy for patients with CRLF2-re-arranged and other JAK pathway-mutant Ph- like ALL (including JAK2 or EPOR fusions), the potential success of this approach is not yet known,3 and ruxoli- tinib may also hinder desired post-HSCT graft-versus-leukemia effects.14 Ponatinib has shown early promise in adults with BCR-ABL1-rearranged (Ph+) ALL in combination with chemotherapy,15 but has not been explored specifically in Ph-like ALL. In summary, our data show that the JAKi ruxolitinib and multi-TKI ponatinib have activity against IGH-EPOR Ph-like ALL with enhanced effects of dual inhibitor treatment. Future clin- ical trials could explore the potential for combinatorial efficacy of ruxolitinib and ponatinib with chemotherapy in patients with IGH-EPOR fusions and other high-risk Ph-like ALL subtypes.
Lisa M. Niswander,1,2* Joseph P Loftus,1* Élodie Lainey,3,4 Aurélie Caye-Eude,4,5 Morgane Pondrom,6
David A. Hottman,1 Ilaria Iacobucci,7 Charles G. Mullighan,7 Nitin Jain,8 Marina Konopleva,8 Hélène Cavé,4,5
André Baruchel,9 Pierre S. Rohrlich6,10# and Sarah K. Tasian1,2,11#
1Division of Oncology and Center for Childhood Cancer Research, Children’s Hospital of Philadelphia; Philadelphia, PA, USA; 2Department of Pediatrics, University of Pennsylvania Perelman School of Medicine; Philadelphia, PA, USA; 3Service d'Hématologie Biologique, Hôpital Robert Debré, Assistance Publique des Hôpitaux de Paris (AP-HP), Paris, France; 4Institut de Recherche Saint-Louis, INSERM, UMR_S1131, Université de Paris, Paris, France; 5Département de Génétique, Hôpital Robert Debré, Assistance Publique des Hôpitaux de Paris (AP-HP), Paris, France; 6Pediatric Hematology Unit, L'Archet Hospital, CHU Nice, Nice, France; 7Department of Pathology, St Jude Children’s Research Hospital,
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