The MDM2 small-molecule inhibitor RG7388 leads to potent tumor inhibition in p53 wild-type neuroblastoma

Abstract

Neuroblastoma is an aggressive pediatric malignancy which is >98% p53 wild-type at diagnosis. As a primary repressor of p53 activity and part of a p53-activated negative feedback loop, targeting of mouse double minute 2 homolog (MDM2) is an attractive therapeutic approach to reactivation of p53. Since development of the first selective MDM2 inhibitor, Nutlin-3a, newer compounds have been developed for increased potency and improved bioavailability. Herein, we sought to determine the efficacy and specificity of a second-generation MDM2 inhibitor, RG7388, in neuroblastoma cell lines and xenografts and examine its effect on the p53-independent pathway of hypoxia-inducible factor-1 alpha (HIF-1α)/vascular endothelial growth factor (VEGF). Cell viability and apoptosis studies were performed on the neuroblastoma cell lines, NGP, SH-SY5Y, LAN-5, LAN-5 si-p53 (p53 silenced), and SK-N-AS (p53 null). RG7388 potently decreased cell proliferation and activated p53-dependent apoptosis. Tumor-bearing mice treated with RG7388 demonstrated significant tumor inhibition by 59% in NGP (P = 0.003), 67% in SH-SY5Y (P = 0.006), and 75% in LAN-5 (P = 0.0019) p53 wild-type xenograft tumors, but no inhibitory effect on LAN-5 si-p53 or SK-N-AS p53-silenced/null xenograft tumors. Moreover, RG7388 was found to inhibit the p53-independent pathway of HIF-1α/VEGF with decreased gene expression and alteration of angiogenesis. Our study supports the further evaluation of RG7388 as a novel treatment option in p53 wild-type neuroblastoma at diagnosis and relapse.

Preclinical evaluation of the first intravenous small molecule MDM2 antagonist alone and in combination with temozolomide in neuroblastoma

“…The PD profile was consistent with the PK profile, mechanism of action, and previous studies. 11,25,27,32 The analysis of PD biomarkers of response to RO6839921 alone showed changes in MIC-1, p21, p53 and Ki67, consistent with our previous in vitro observations of idasanutlin mediated anti-tumour activity. 10 Our study is the only preclinical study of idasanutlin in neuroblastoma so far to include MIC-1 as a PD biomarker, and demonstrated that in response to combination treatment MIC-1 was the most responsive biomarker in the SHSY5Y-Luc model and p21 in the NB1691-Luc model.…”

“…5 TP53 mutations are rare in neuroblastoma even at relapse, however upstream p53 pathway inactivation through MDM2 amplification (2.5-7%) and p14 ARF abnormalities (2-22% homozygous deletion; 7% methylation), have been reported particularly at relapse and support the use of MDM2 antagonists. [6][7][8][9] We and others have demonstrated highly potent anti-tumour effects of idasanutlin in preclinical neuroblastoma models, alone and in combination with chemotherapy currently used in the treatment of high-risk neuroblastoma, namely cisplatin, doxorubicin, topotecan (induction), busulfan (consolidation) and temozolomide (relapse), 10,11 and recently combinations with other targeted agents have been reported. 12,13 In addition, another MDM2 antagonist in clinical trials, MI-773 (SAR405838), has been shown to enhance doxorubicin mediated cytotoxicity in neuroblastoma cell lines.…”

Analysis ofMDM2Amplification: Next-Generation Sequencing of Patients With Diverse Malignancies

“…39 Zhou et al 10 reported that MDM2-overexpressed/ TP53 -null cancer cells are associated with increased VEGF mRNA expression compared with MDM2-negative/ TP53 -null cells. Furthermore, Lakoma et al 11 showed that pharmacologic inhibition of MDM2 is associated with a decrease in hypoxia-inducible factor 1α and VEGF expression in cancer cell lines. TP53 alterations also have been reported to be associated with increased VEGF expression in preclinical models as well as in patients with lung adenocarcinoma.…”

“…10 In addition, suppression of MDM2 activity with a small-molecule inhibitor leads to decreased hypoxia-inducible factor 1α and VEGF expression, which support a role for MDM2 in angiogenesis. 11 TP5 3 mutations also lead to increased VEGF-A expression 12,13 and have been associated with increased responsiveness to VEGF/ VEGF receptor inhibitor therapy. 14–16 Taken together, these data suggest that MDM2 promotes angiogenesis through either inhibition of p53 or mechanisms independent of p53.…”

Reviving the guardian of the genome: Small molecule activators of p53

“…In addition to preclinical assessment of RG7338 as therapy for neuroblastoma (L. Chen et al, 2015; Lakoma et al, 2015), childhood sarcoma (Phelps et al, 2015), and ovarian carcinoma(Zanjirband, Edmondson, & Lunec, 2016), RG7338 is involved in five other phase I/II studies currently recruiting participants: in combination with obinutuzumab, a novel anti-CD20 mAB, for relapsed or refractory follicular lymphoma or diffuse large B-cell lymphoma (Illidge et al, 2015) (NCT02624986), in combination with Venetoclax, a novel BH3-mimetic/Bcl-2 inhibitor, for patients over 60 with relapsed or refractory AML who are ineligible for cytotoxic therapy (Woyach & Johnson, 2015) (NCT02670044), in combination with dexamethasone and ixazomib citrate, a novel proteasome inhibitor, for refractory multiple myeloma (P. G. Richardson et al, 2015) (NCT02633059), as a standalone drug for polycythemia vera and essential thrombocythemia (NCT02407080), and in a study designed to compare oral vs intravenous administration of RG7388 in terms of excretion balance, pharmacokinetics, metabolism, and bioavailability in patients with solid tumors (NCT02828930).…”