Phase 1 study of intravenous rigosertib (ON 01910.Na), a novel benzyl styryl sulfone structure producing G2/M arrest and apoptosis, in adult patients with advanced cancer.

Rigosertib (ON 01910.Na), a synthetic novel benzyl styryl sulfone, was administered to 28 patients with advanced cancer in a Phase I trial in order to characterize its pharmacokinetic profile, determine the dose-limiting toxicities (DLT), define the recommended phase II dose (RPTD) and to document any antitumor activity. Patients with advanced malignant neoplasms refractory to standard therapy were given escalating doses of rigosertib (50, 100, 150, 250, 325, 400, 650, 850, 1,050, 1,375, 1,700 mg/m(2)/24h) as a 3-day continuous infusion (CI) every 2 weeks. An accelerated Fibonacci titration schedule with specified decreases for toxicities was used for escalation until grade ≥2 toxicity occurred. Intrapatient dose escalation was allowed if toxicity was grade ≤2 and the disease remained stable. Plasma pharmacokinetics (PK) and urinary PK assessments were studied in the 1st and 4th cycles. Twenty-nine patients (12 men and 17 women; age 36-87 y with a median of 63 y) were registered, but one died before study drug was given. Twenty-eight patients received a median of 3 cycles of therapy. Most common grade ≥2 toxicities attributable to rigosertib included fatigue, anorexia, vomiting and constipation. DLTs included muscular weakness, hyponatremia, neutropenia, delirium and confusional state. Risk factors for severe toxicities include pre-existing neurological dysfunction or advanced gynecologic cancer after pelvic surgery. Rigosertib pharmacokinetics showed rapid plasma distribution phases and urinary excretion. Elevations in plasma Cmax and AUC due to decreases in plasma clearance were associated with acute grade ≥3 toxicities. Of 22 evaluable patients, 9 (41%) achieved a best overall response of stable disease; all other patients (n=13; 59%) progressed. The median progression-free survival time was 50 days (95% confidence interval [CI]: 37-80 days). Nine (41%) patients survived for over 1 y. In summary, prolonged IV infusions of rigosertib were generally well tolerated. Nine (41%) patients achieved stable disease and 9 (41%) patients survived for over 1 year. The RPTD appears to be 850 mg/m(2)/24hr CI x 3 days. (ClinicalTrials.gov identifier: NCT01538537).

Effect of ON 01910.Na, an anticancer mitotic inhibitor, on cell-cycle progression correlates with RanGAP1 hyperphosphorylation.

The benzyl styryl sulfone, ON 01910.Na, is a novel anticancer agent that inhibits mitotic progression and induces apoptosis in most cancer cell lines. We examined the effect of ON 01910.Na on DNA damage-signaling molecules upstream of Cdc25C (Chk1, Chk2, and H2AX), as well as on Ran GTPase-activating protein 1 conjugated to small ubiquitin-related modifier 1 (RanGAP1·SUMO1), a mitosis coordinator. Prostate cancer, lymphoma, and leukemic cells were incubated with the drug for 4, 16, or 24 hours. Cell lysates were resolved on SDS-PAGE and analyzed by Western blot. Camptothecin and doxorubicin treatment caused activation/phosphorylation of DNA damage-responsive molecules by 4 hours, whereas ON 01910.Na did not do so. ON 01910.Na caused hyperphosphorylation of RanGAP1·SUMO1 within 4 hours that was sustained for more than 24 hours. Mild phosphorylation of Chk2 was observed only after 24-hour exposure, indicating that DNA damage response was not an initial effect of ON 01910.Na. MOLT-3 cells, synchronized by double-thymidine block, when released into a medium containing ON 01910.Na, accumulated mitotic cell number with a peak from 10 to 14 hours and remained near plateau for 20 hours, which corresponded with the time of RanGAP phosphorylation. ON 01910.Na had minimal effects on tubulin polymerization. These findings imply that ON 01910.Na neither induces DNA damage directly nor acts as a tubulin toxin. Its biological activity appears to rely on prolonged phosphorylation/hyperphosphorylation of RanGAP1·SUMO1. M-phase arrest and the consequent induction of apoptosis that follows could possibly be attributed to it. ON 01910.Na may act as an inhibitor of a RanGAP1·SUMO1 phosphatase or a stimulant of a new kinase. RanGAP1·SUMO1 appears to be a new target pathway for cancer chemotherapy.

Discontinuous drug binding to proteins: binding of an antineoplastic benzyl styryl sulfone to albumin and enzymes in vitro and in phase I clinical trials.

Sodium (E)-{N-[2-methyloxy-5-(2',4',6'-trimethoxy-styrylsulfonyl) methylenephenyl]amino}acetate (C(21)H(24)NNaO(8)S, ON 01910.Na) is a novel, synthetic benzyl styryl sulfone, currently in phase I clinical trials in cancer patients. Our objective was to use electrospray mass spectrometry to determine, in intact complexes, the number of drug molecules bound to albumin and selected enzymes. Native and recombinant albumin incubated with the drug, at various molar ratios, revealed simultaneous and discontinuous progression of drug binding, yielding intact albumin-drug complexes containing up to 22 drug molecules. Comparable complex protein-drug patterns were obtained for several enzymes, e.g., carbonic anhydrase. Intact albumin-ON 01910 complexes were also found in all patient samples. The drug-binding profiles were comparable, but not identical, for increasing sampling times and different doses (400-1700 mg/m(2)). We concluded that the techniques developed are capable of detecting the simultaneous formation of intact protein-drug complexes and of determining the number of drug molecules bound to proteins. The results enhance our hypothesis that drug binding may lead to conformational changes in proteins that, in turn, account for the exclusion of specific binding complexes and may influence protein behavior and activity. Application of these techniques reveals new insights about the nature of the antineoplastic drug ON 01910 in patient plasma, and the information obtained may have significance in understanding drug delivery to tumors.

[Adenovirus-mediated transfer of anti-MDR1 ribozyme in the treatment of multidrug-resistant human lymphoma in SCID mice].

OBJECTIVE: To evaluate the effect of adenovirus-mediated transfer of anti-MDR1 ribozyme on restoring drug sensitivity of multidrug-resistant human lymphoma both in vitro and in SCID mice. METHODS: A recombinant adenovirus expressing ribozyme against codon 196 of MDR1 mRNA (Ad-196MDR1-Rz) was developed through cotransfection of shuttle vector pCA14 containing 196MDR1-Rz and rescue vector pJM17 into human embryonic kidney cell line 293. In vitro Daudi/MDR20, a MDR1-mediated drug-resistant human lymphoma cell line, was transduced by Ad-196MDR1-Rz at MOI of 400 pfu/cell. RT-PCR and FACS analyses were used to evaluate the MDR1 expression in both transcriptional and translational levels. MTT assay was used for analysis of drug resistance. In vivo, SCID mice were inoculated subcutaneously by 5 x 10(6) Daudi/MDR20 or parental Daudi/wt cells. Adenovirus was injected locally. Vincristine (VCR) was given intraperitoneally. RESULTS: In vitro transduction of Ad-196MDR1-Rz to Daudi/MDR20 cells was able to interrupt MDR1 transcription, inhibit P-gp expression and restore drug sensitivity to VCR. Of SCID mice bearing Daudi/MDR20 cells, tumor free rate and long term survival were 66.7% (6/9) and > 120 days in the therapeutic group of Ad-196MDR1 + VCR vs 12.5% (7/8) and none survived > 120 days in the control groups of Ad-Mock + VCR or VCR alone. The difference was very statistically significant. CONCLUSION: Ad-mediated transfer of 196MDR1-Rz can revert drug resistance of MDR tumor cells both in vitro and in vivo. Ad-196MDR1-Rz may be helpful as an adjuvant in the chemotherapy of P-gp mediated MDR human tumor.