Initial testing of the investigational NEDD8-activating enzyme inhibitor MLN4924 by the pediatric preclinical testing program

BACKGROUND

MLN4924 is an investigational first-in-class small molecule inhibitor of NEDD8-activating enzyme (NAE). NAE is an essential component of the NEDD8 conjugation pathway, controlling the activity of a subset of ubiquitin-proteasome system (UPS) E3 ligases, multiprotein complexes that transfer ubiquitin molecules to substrate proteins.

PROCEDURES

MLN4924 was tested against the PPTP in vitro panel using 96-hour exposure time at concentrations ranging from 1.0 nM to 10 µM. It was tested in vivo at a dose of 100 mg/kg [66 mg/kg for the acute lymphoblastic leukemia (ALL) xenografts] administered orally twice daily × 5 days. Treatment duration was 3 weeks.

RESULTS

The median relative IC(50) for MLN4924 against the PPTP cell lines was 143 nM, (range: 15-678 nM) with that for the Ewing panel being significantly lower (31 nM). MLN4924 induced significant differences in EFS distribution compared to control in 20 of 34 (59%) evaluable solid tumor xenografts. MLN4924 induced intermediate activity (EFS T/C values >2) in 9 of the 33 evaluable xenografts (27%), including 4 of 4 glioblastoma xenografts, 2 of 3 Wilm's tumor xenografts, 2 of 5 rhabdomyosarcoma xenografts, and 1 of 4 neuroblastoma xenografts. For the ALL panel, 5 of 8 evaluable xenografts showed intermediate activity for the EFS T/C measure. MLN4924 did not induce objective responses in the PPTP solid tumor or ALL panels.

CONCLUSIONS

MLN4924 showed potent activity in vitro and in vivo showed tumor growth inhibitory activity against a subset of the PPTP solid tumor and ALL xenografts.

MLN4924: a novel first-in-class inhibitor of NEDD8-activating enzyme for cancer therapy

INTRODUCTION

The small ubiquitin-like molecule NEDD8 has been identified as an essential regulator of the activity of the cullin-RING E3 ubiquitin ligases (CRLs), which control the turnover of multiple proteins with fundamental roles in cancer biology. The aberrant function of the NEDD8 cascade within the context of malignancy makes it an attractive target for the development of novel anticancer agents. MLN4924 is a first-in-class inhibitor of the proximal regulator of the NEDD8 system (NEDD8-activating enzyme, NAE) that has entered Phase-I trials for cancer therapy and has established that significant therapeutic benefit can be achieved by antagonizing NEDD8-mediated protein degradation.

AREAS COVERED

This review provides a detailed overview of the NEDD8 system and discusses the mechanisms of action of MLN4924, a novel small molecule NAE inhibitor. Key findings from preclinical investigations of MLN4924 in a broad range of cancer models and preliminary findings from ongoing Phase-I clinical trials with MLN4924 are also discussed.

EXPERT OPINION

Targeting protein NEDDylation represents an exciting new anticancer strategy with demonstrable therapeutic benefit. Ongoing and future studies focused on dissecting the functional status/regulation of the NEDD8 system in individual tumor types will facilitate the design of novel approaches that yield optimal therapeutic benefit.