Real-time nanoscale proteomic analysis of the novel multi-kinase pathway inhibitor rigosertib to measure the response to treatment of cancer

INTRODUCTION

Rigosertib (ON01910.Na), is a targeted therapeutic that inhibits multiple kinases, including PI3K and PIk-1. Rigosertib has been found to induce the proliferative arrest and apoptosis of myeloblasts but not of other normal hematopoietic cells. Rigosertib has significant clinical activity as a therapy for patients with high-risk myelodysplastic syndrome who are otherwise refractory to DNA methyltransferase inhibitors. Moreover, rigosertib has potential clinical activity in a multitude of solid tumors.

AREAS COVERED

The objective of this review is to evaluate the mechanism of activity, efficacy and dosing of rigosertib. Furthermore, the challenge in the clinical development of rigosertib, to identify the specific patients that are most likely to benefit from this therapeutic agent, is discussed. A PubMed search was performed using the following key words: rigosertib and ON01910.Na.

EXPERT OPINION

We describe the application of a novel nanoscale proteomic assay, the nanoimmunoassay, a tractable approach for measuring the activity and predicting the efficacy of rigosertib, in real-time, using limited human clinical specimens. Our strategy suggests a possible paradigm where proteomic analysis during the pre-clinical and clinical development of a therapy can be used to uncover biomarkers for the analysis and prediction of efficacy in human patients.

Antimitotic agents for the treatment of patients with metastatic castrate-resistant prostate cancer

INTRODUCTION

Metastatic castrate-resistant prostate cancer (mCRPC) is the second deadliest cancer in men. The group of taxanes, which target microtubules of mitotic cells, is currently the only chemotherapy which has proven to increase overall survival in mCRPC patients. Other mitotic inhibitors are being explored for their clinical potential in mCRPC treatment.

AREAS COVERED

In this review, we summarize recent developments in the application of mitotic inhibitors for mCRPC from a clinical perspective. The four main groups of mitotic inhibitors currently being tested in clinical trials are microtubule-inhibitors, polo-like kinase 1 inhibitors, aurora kinase inhibitors and kinesin-spindle protein inhibitors. Compounds of these groups of inhibitors that are in clinical development for mCRPC are discussed. For this extensive overview, relevant literature was searched in PubMed and retrieved from clinicaltrials.gov and presentations at ASCO/AACR meetings.

EXPERT OPINION

In general, mitotic inhibitors are clinically well tolerated but exert limited antitumor activity compared to preclinical study results. However, efficacy of mitotic inhibitors is improving, either by personalizing treatment, by introducing more active compounds, by decreasing resistance of cancer cells against mitotic inhibitors or by using mitotic inhibitors in combination therapies.

Determination of intestinal permeability of rigosertib (ON 01910.Na, Estybon): correlation with systemic exposure

Objectives

Rigosertib (ON 01910.Na, Estybon) is a novel, anticancer agent undergoing phase 3 clinical trials for a lead indication against myelodysplastic syndromes (MDS). In this research, the permeability of rigosertib was evaluated using the in-situ perfused rat intestine (IPRI) model to support development of an oral formulation for rigosertib for treating cancer patients.

Methods

Experiments (n = 6 per group) were conducted using male Sprague-Dawley rats. Studies evaluated permeability across various intestinal segments and assessed the dose-linearity of absorption over the entire intestinal length. Drug concentrations in the portal and jugular vein were collected to correlate permeability parameters with presystemic and systemic exposure.

Key findings

Rigosertib permeability was highest in the jejunum, although parameter estimates indicated that rigosertib was a medium permeability compound. The compound displayed nonlinear absorption in the IPRI model, suggesting a saturable transport process. Transport inhibition studies using Caco-2 cells demonstrated that rigosertib was a P-glycoprotein (P-gp) substrate. Absolute bioavailability of rigosertib (10 and 20 mg/kg, 1-h infusion) in rats was estimated to be 10–15%. However, the fraction absorbed in humans predicted from IPRI data (52%) was consistent with published clinical data for rigosertib (35% oral bioavailability).

Conclusions

The results of this research indicated that rigosertib is a promising candidate for oral delivery. Further studies are needed to evaluate the potential impact of P-gp and other intestinal transporters on the oral absorption of this promising anticancer agent.