AZ64 inhibits TrkB and enhances the efficacy of chemotherapy and local radiation in neuroblastoma xenografts

Abstract

Neuroblastoma is a common pediatric tumor characterized by clinical heterogeneity. Because it is derived from sympathetic neuroblasts, the NTRK family of neurotrophin receptors plays an integral role in neuroblastoma cell survival, growth, and differentiation. Indeed, high expression of NTRK1 is associated with favorable clinical features and outcome, whereas expression of NTRK2 and its ligand, brain-derived neurotrophic factor (BDNF), are associated with unfavorable features and outcome. AZ64 (Astra Zeneca) is a potent and selective inhibitor of the NTRK tyrosine kinases that blocks phosphorylation at nanomolar concentrations. To determine the preclinical activity of AZ64, we performed intervention trials in a xenograft model with NTRK2-overexpressing neuroblastomas. AZ64 alone significantly inhibited tumor growth compared to vehicle-treated animals (p = 0.0006 for tumor size). Furthermore, the combination of AZ64 with conventional chemotherapeutic agents, irinotecan and temozolomide (irino–temo), showed significantly enhanced anti-tumor efficacy compared to irino–temo alone [(p < 0.0001 for tumor size, p < 0.0005 for event-free survival (EFS)]. We also assessed the combination of AZ64 and local radiation therapy (RT) on a neuroblastoma hindlimb xenograft model, and the efficacy of local RT was significantly increased when animals were treated simultaneously with AZ64 (p < 0.0001 for tumor size, p = 0.0006 for EFS). We conclude that AZ64 can inhibit growth of NTRK-expressing neuroblastomas both in vitro and in vivo. More importantly, it can significantly enhance the efficacy of conventional chemotherapy as well as local RT, presumably by inhibition of the NTRK2/BDNF autocrine survival pathway.

Trk inhibitor attenuates the BDNF/TrkB-induced protection of neuroblastoma cells from etoposidein vitroandin vivo

“…Our results and the previous studies 14,15 provide compelling evidence that the combination of a Trk inhibitor with current cytotoxic therapies will improve treatment efficacy.…”

“…13 Other Trk inhibitors, AZ623 and AZ64, were found to inhibit activation of TrkB in vitro and had a synergistic effect on tumor growth with topotecan in vivo. 14,15 In our current study, we found that while AZD6918 may not be sufficient to inhibit tumor growth or increase mice survival as a single agent at the tested doses (70 mg/kg, 100 mg/ kg), it did increase the sensitivity of TB3 xenograft tumors to etoposide, a topoisomerase II inhibitor that is currently used in the treatment of NB. This result is consistent with the studies of other Trk inhibitors Lestaurtinib or AZ623 and AZ64.…”

“…14 Previously, Trk inhibitors have been shown to increase the sensitivity of NB cells to a topoisomerase I inhibitor (topotecan) alone 14 or in combination with an alkylating agent (irinotecan and temozolimide). 15 In this study we show that inhibition of the Trk activity can also increase the cytotoxic activity of etoposide, a topoisomerase II inhibitor. This study extends the spectrum of cytotoxic agents whose in vivo activity in pre-clinical models can be increased by inhibition of Trk activity.…”

“…This result is consistent with the studies of other Trk inhibitors Lestaurtinib or AZ623 and AZ64. [13][14][15] While CEP-701 has shown activity against a range of in vivo models including prostate, pancreatic and thyroid cancer xenografts, [16][17][18] CEP-701 inhibits several additional tyrosine kinase targets such as PDGFR, VEGFR, RET and PKC, 18,19 and remains active in trials in clinical settings in which Trk kinases are not believed to pathogenic, such as acute myeloid leukemia and myeloproliferative disease. 20,21 Therefore, development of potent and selective Trk kinase inhibitors remains critical to evaluate the role of Trk signaling pathway inhibition in treatment of patients with NB.…”

Management of high-grade gliomas in the pediatric patient: Past, present, and future

“…90 There are small molecule inhibitors available for the neurotrophin receptors. 91,92 AZ64 is an active, orally available, small molecule kinase inhibitor with nanomolar potency against all 3 NTRK receptors shown to inhibit growth of NTRK-expressing neuroblastomas, both in vitro and in vivo in animal models. 91 AZ64 enhances the efficacy of conventional chemotherapy and RT.…”