Olverembatinib for myeloid/lymphoid neoplasm associated with eosinophilia and FGFR1 rearrangement

aState key Laboratory of experimental hematology, National Clinical Research Center for Blood Diseases, haihe Laboratory of Cell ecosystem, institute of hematology & Blood Diseases hospital, Chinese academy of medical Sciences & peking union medical College, Tianjin, p.R. China; bTianjin institutes of health Science, Tianjin, p.R. China; cmDS and mpN Centre, institute of hematology and Blood Diseases hospital, Chinese academy of medical Sciences & peking union medical College, Tianjin, p.R. China; dhematologic pathology Center, institute of hematology and Blood Diseases hospital, Chinese academy of medical Sciences & peking union medical College, Tianjin, p.R. China; eDepartment of hematology, The First affiliated hospital of Ningbo university, Ningbo Clinical Research Center for hematologic malignancies, Ningbo, p.R. China; fCentre for hematology, Department of immunology and inflammation, imperial College of Science, Technology and medicine, London, united kingdom

8p11(eight-p-eleven) myeloproliferative syndrome (eMS), which is an uncommon neoplasm characterized by translocations involving the fibroblast growth factor receptor-1 (FGFR1). this entity is included in myeloid/lymphoid neoplasms with eosinophilia and tyrosine kinase gene fusions (MLN-tK) in the World health organization (Who) classification [1]. Seventeen FGFR1 translocation partners are reported. the three most prevalent are zinc finger MYM-type containing 2 (ZMYM2), centriolin (CNTRL) and FGFR1 oncogene partner (FGFR1OP). their N-terminal self-association motifs are fused to the C-terminal tyrosine kinase domain of FGFR1 resulting in constitutive activation of the FGFR1 kinase and downstream signaling pathways [2].
the clinical course is aggressive with rapid progression to acute leukemia. Most people are resistant to tyrosine kinase-inhibitors (tKis). in persons with CNTRL::FGFR1 the complete remission rate is only 20% with chemotherapy [3] and 1-year survival is only 40% [4].
Subsequent he was started on induction therapy with combination of olverembatinib(40 mg orally every other day) plus 5-drugs (etoposide, vindesine, cytarabine, cyclophosphamide, dexamethasone) regimen. Upon taking o l v e r e m b a t i n i b, h e p a t o s p l e n o m e g a l y a n d  lymphadenopathy rapidly resolved. A rapid decrease in WBC was achieved. Bone marrow aspirate demonstrated 0.79% B-cell lymphoblasts and 0.34% t-cell lymphoblasts. the percentage of positive FGFR1 signals reduced to 50%. he achieved complete hematologic remission (Chr) with 4 weeks (Figure 1(B)). thereafter he continued the same regimen one more cycle. end-of-consolidation bone marrow revealed 9.14% t-cell lymphoblasts and 0.05% B-cell lymphoblasts. there was a major cytogenetic response (MCyr) (the percentage of positive FGFr1 probe signals reduced from 92% to 22%) (Figure 1(B)). Qrt-PCr revealed a reduction of CNTRL::FGFR1 transcript in bone marrow (Figure 1(C)). there was no adverse event during treatment. however, two months later, bone marrow aspirate revealed hypercellularity and an increased proportion of blasts (Supplementary Figure S1(B)). Cytogenetic analysis suggested clonal evolution with additional chromosomal aberrations (ACA), 46, XY, t (8;9) (p11.2; q33.2) [3]/46, idem, del (7) Figure S1(d)). Subsequent he received salvage therapy with pemigatinib(9 mg orally once a day) plus a 5-drug induction containing high dose cytarabine (mitoxantrone, vindesine, cytarabine, etoposide, dexamethasone). however, the patient rapidly progressed to blast phase with 24.56% t-cell lymphoblasts, and 0.25% B-cell lymphoblasts. ACA clone was expanded ( Figure  1(d)). he died from septic shock two months later.
Although MLN-tK with alternations involving PDGFRα and platelet-derived growth factor receptor β (PDGFRβ) usually respond exquisitely to imatinib, some cases may still develop drug resistance due to acquired mutations in the kinase domain. our previous report described a 28-year-old man with FIP1-like-1(FIP1L1)::PDGFRα fusion who acquired a PDGFRα t674i mutation one year after receiving imatinib [8]. in addition, we also report for the first time a 46-year-old male patient with tuberous sclerosis complex subunit 1(TSC1)::PDGFRβ fusion who achieved molecular remission for up to 15 years after imatinib treatment. In vitro experiments revealed that Ba/ F3 cells expressing TSC1::PDGFRβ t681i were refractory to imatinib and nilotinib [9]. PDGFRα t674i and PDGFRβ t681i are analogous to t315i in BCR::ABL1, which directly affect the binding of tKi [10]. therefore, we explored whether olverembatinib and FGFrs inhibitors (pemigatinib) could target these gatekeeper mutations.
to further ascertain the efficacy of olverembatinib, cell cycle and apoptosis assay were performed in Ba/F3 models. At the same concentration as pemigatinib and ponatinib, olverembatinib caused a significant arrest in cell cycle progression in G0/G1 phase and an increased proportion in apoptosis. Although pemigatinib increased apoptosis rate and cell cycle arrest in Ba/F3-CNTRL::FGFR1, it was still less effective than olverembatinib in the presence of the other two mutations (Figure 2(B,C)). Consistent with these findings, olverembatinib dose-dependently inhibited tyrosine phosphorylation of CNTRL::FGFR1 and its downstream targets StAt5, StAt3 with a concentration of approximately 3 nM, whereas inhibition of K656e and V561M required higher concentrations of olverembatinib (30 and 100 nM, respectively) (Figure 2(d)). olverembatinib also decreased the total level of FGFR1 protein in Ba/ F3-CNTRL::FGFR1. Under the same conditions, imatinib and dasatinib could not inhibit the phosphorylation of signal pathway while ponatinib and pemigatinib could also efficiently inhibit the signal pathway only in CNTRL::FGFR1 and CNTRL::FGFR1 K656e (Supplementary Figure S3(A-C)). As for CNTRL::FGFR1 V561M , only olverembatinib can strongly inhibit its signal pathway at lower nanomolar concentration.
our eMS patient achieved Chr and MCyr within 8 weeks with olverembatinib. FGFR1 K656e and V561M mutations were detected at relapse, along with the acquisition of new ACA. our results showed that compared with CNTRL::FGFR1, the K656e mutation had no significant effect on drug sensitivity to tKis and pemigatinib, but enhanced phosphorylation levels in signaling pathways. this is not the same as the research that BaF3-FGFR1 K656e were insensitive to pemigatinib with 9.3 fold increase in iC 50 [12]. Accordingly, same mutations of fusion genes and single genes may possess different mechanisms that ultimately affect drug sensitivity. V561M mutation conferred resistance to pemigatinib while still be sensitive to olverembatinib. this is consistent with previous study that pemigatinib had less potency against FGFR1 V561M [13] and olverembatinib can overcome V561M mutation of fusion gene and single gene of FGFR1 [12]. thus, clonal evolution to acquire new ACA and other somatic mutations may be the main cause of relapse. Additional chromosomal translocations like t(10;11) (p12;q23) which leads to the formation of mixed lineage leukemia(MLL)::AF10 fusion. Acute myeloid leukemia(AML) patients harboring MLL::AF10 have a particularly poor prognosis compared to those not carrying it [14]. Although clones harboring CNTRL::FGFR1 fusion preserved sensitivity, clones with ACA were resistant to olverembatinib. Previous study found that multiple oncogenes and several signaling pathways contribute cooperatively to the pathogenesis of CNTRL::FGFR1 in their mouse model [15]. these indicate CNTRL::FGFR1 may induce the genomic instability to alter multiple oncogenes, disrupting signaling pathways to drive the disease progression. So, earlier treatment with olverembatinib may have the potential to achieve complete remission for eMS patients.
in conclusion, olverembatinib is a potent inhibitor against CNTRL::FGFR1, CNTRL::FGFR1 K656e , and CNTRL::FGFR1 V561M . that may be efficacious in treatment for patients with FGFR1 rearrangements. Given the first approval of olverembatinib in China for treatment of chronic phase CML (CML-CP) and accelerated phase CML (CML-AP) with mutation t315i, our findings warrant that olverembatinib can serve as a bridge to allogeneic hematopoietic stem cell transplantation which is the only curative option for eMS patients to prolong survival [3].