Rigosertib

Rigosertib is a dual inhibitor of phosphoinositide 3-kinase (PI3K) and polo-like kinase 1 (PLK1) [1].

In vitro studies show that rigosertib inhibits the PI3K/AKT pathway, down-regulates cyclin D1, induces NOXA and BIM and activates the JNK pathway in human leukemic cells. Rigosertib induces apoptosis of a variety of human tumor cell lines including breast, prostate, ovarian, pancreatic, SCLC, colorectal, melanoma and et al. For instant, it shows anti-tumor efficacy in BT20, MCF-7, BT474, OV-CAR-3, A549 and HCT-116 with IC50 values of 80nM, 75nM, 50nM, 75nM, 90nM and 75nM, respectively. In addition, rigosertib is also effective against the drug resistant tumor cell lines. It potently inhibits tumor growth with IC50 values of 100nM and 50nM against MES-SA/DX5 and CEM/C2, respectively. Moreover, it is reported that rigosertib can affect the cell cycle of both normal cells and tumor cells. Rigosertib leads to a blockade of cell cycle progression in the G1 and G2/M phases in normal diploid human fetal lung cells. When treated with DU145 cells, rigosertib induces cell cycle arrest in G2/M phase [2].

References:
[1] Anderson R T, Keysar S B, Bowles D W, et al. The Dual Pathway Inhibitor Rigosertib Is Effective in Direct Patient Tumor Xenografts of Head and Neck Squamous Cell Carcinomas. Molecular cancer therapeutics, 2013, 12(10): 1994-2005.
[2] Reddy M V R, Venkatapuram P, Mallireddigari M R, et al. Discovery of a clinical stage multi-kinase inhibitor sodium (E)-2-{2-Methoxy-5-[(2′, 4′, 6′-trimethoxystyrylsulfonyl) methyl] phenylamino} acetate (ON 01910. Na): synthesis, structure–activity relationship, and biological activity. Journal of medicinal chemistry, 2011, 54(18): 6254-6276.

The safety and efficacy of rigosertib in the treatment of myelodysplastic syndromes.[Pubmed:27400247]

Expert Rev Anticancer Ther. 2016 Aug;16(8):805-10.

INTRODUCTION: Hypomethylating agents (HMAs) are the standard of care for patients with higher-risk myelodysplastic syndromes (MDS), but patients who relapse or are refractory have a poor prognosis with an estimated survival of 4-6 months. Rigosertib, a Ras mimetic that inhibits the phophoinositide 3-kinase and polo-like kinase pathways, has been tested in patients with higher-risk MDS following treatment with HMAs, where there are no approved second-line therapies. AREAS COVERED: This review will provide an overview of Rigosertib, including safety and efficacy demonstrated in clinical trials. Expert commentary: There is an urgent need for new treatment options for patients who have failed or progressed on HMAs. Rigosertib is currently undergoing testing as a single agent in certain subsets of higher-risk MDS patients as well as in combination with azacitidine, where preliminary data show efficacy in patients with de novo MDS as well as HMA failures.

Rigosertib versus best supportive care for patients with high-risk myelodysplastic syndromes after failure of hypomethylating drugs (ONTIME): a randomised, controlled, phase 3 trial.[Pubmed:26968357]

Lancet Oncol. 2016 Apr;17(4):496-508.

BACKGROUND: Hypomethylating drugs are the standard treatment for patients with high-risk myelodysplastic syndromes. Survival is poor after failure of these drugs; there is no approved second-line therapy. We compared the overall survival of patients receiving Rigosertib and best supportive care with that of patients receiving best supportive care only in patients with myelodysplastic syndromes with excess blasts after failure of azacitidine or decitabine treatment. METHODS: We did this randomised controlled trial at 74 hospitals and university medical centres in the USA and Europe. We enrolled patients with diagnosis of refractory anaemia with excess blasts (RAEB)-1, RAEB-2, RAEB-t, or chronic myelomonocytic leukaemia based on local site assessment, and treatment failure with a hypomethylating drug in the past 2 years. Patients were randomly assigned (2:1) to receive Rigosertib 1800 mg per 24 h via 72-h continuous intravenous infusion administered every other week or best supportive care with or without low-dose cytarabine. Randomisation was stratified by pretreatment bone marrow blast percentage. Neither patients nor investigators were masked to treatment assignment. The primary outcome was overall survival in the intention-to-treat population. This study is registered with ClinicalTrials.gov, NCT01241500. FINDINGS: From Dec 13, 2010, to Aug 15, 2013, we enrolled 299 patients: 199 assigned to Rigosertib, 100 assigned to best supportive care. Median follow-up was 19.5 months (IQR 11.9-27.3). As of Feb 1, 2014, median overall survival was 8.2 months (95% CI 6.1-10.1) in the Rigosertib group and 5.9 months (4.1-9.3) in the best supportive care group (hazard ratio 0.87, 95% CI 0.67-1.14; p=0.33). The most common grade 3 or higher adverse events were anaemia (34 [18%] of 184 patients in the Rigosertib group vs seven [8%] of 91 patients in the best supportive care group), thrombocytopenia (35 [19%] vs six [7%]), neutropenia (31 [17%] vs seven [8%]), febrile neutropenia (22 [12%] vs ten [11%]), and pneumonia (22 [12%] vs ten [11%]). 41 (22%) of 184 patients in the Rigosertib group and 30 (33%) of 91 patients in the best supportive care group died due to adverse events and three deaths were attributed to Rigosertib treatment. INTERPRETATION: Rigosertib did not significantly improve overall survival compared with best supportive care. A randomised phase 3 trial of Rigosertib (NCT 02562443) is underway in specific subgroups of patients deemed to be at high risk, including patients with very high risk per the Revised International Prognostic Scoring System criteria. FUNDING: Onconova Therapeutics, Leukemia & Lymphoma Society.

ON 01910.Na (rigosertib) inhibits PI3K/Akt pathway and activates oxidative stress signals in head and neck cancer cell lines.[Pubmed:27764820]

Oncotarget. 2016 Nov 29;7(48):79388-79400.

Squamous cell carcinoma of the head and neck (HNSCC) is characterized by high morbidity and mortality. Treatment failure, drug resistance and chemoradiation toxicity have necessitated the development of alternative treatment strategies. Styryl benzyl sulfones, a family of novel small molecule inhibitors, are being evaluated as anti-neoplastic agents in multiple clinical trials. The activity of these compounds has been well characterized in several preclinical tumor studies, but their activity has yet to be fully examined in HNSCC. We tested ON 01910.Na (Rigosertib), a styryl benzyl sulfone in late-stage development, in HNSCC preclinical models. Rigosertib induced cytotoxicity in both HPV(+) and HPV(-) HNSCC cells in a dose-dependent manner. Characterization of the underlying molecular mechanism indicated that Rigosertib induced inhibition of the PI3K/Akt/mTOR pathway, induced oxidative stress resulting in increased generation of reactive oxygen species (ROS), and activated extracellular signal-regulated kinases (ERK1/2) and c-Jun NH2-terminal kinase (JNK). Increased phosphorylation and cytoplasmic translocation of ATF-2 were also observed following Rigosertib treatment. These changes in cell signaling led us to consider combining Rigosertib with HNSCC standard-of-care therapies, such as cisplatin and radiation. Our study highlights the promising preclinical activity of Rigosertib in HNSCC irrespective of HPV status and provides a molecular basis for Rigosertib in combination with standard of care agents for HNSCC.

Rigosertib (ON-01910) is a multi-kinase inhibitor and a selective anti-cancer agent, which induces apoptosis by inhibition the PI3 kinase/Akt pathway, promots the phosphorylation of histone H2AX and induces G2/M arrest in cell cycle. Rigosertib is a selective and non-ATP-competitive inhibitor of PLK1 with an IC50 of 9 nM.

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