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Purpose: To determine the pharmacokinetics (PK), maximum tolerated dose (MTD), safety, and antitumor activity of an oral formulation of rigosertib, a dual phosphoinositide 3-kinase (PI3K) and polo-like kinase 1 (Plk1) pathway inhibitor, in patients with advanced solid malignancies.Experimental Design: Patients with advanced solid malignancies received rigosertib twice daily continuously in 21-day cycles. Doses were escalated until intolerable grade ≥2 toxicities, at which point the previous dose level was expanded to define the MTD. All patients were assessed for safety, PK, and response. Urinary PK were performed at the MTD. Archival tumors were assessed for potential molecular biomarkers with multiplex mutation testing. A subset of squamous cell carcinomas (SCC) underwent exome sequencing.Results: Forty-eight patients received a median of 2 cycles of therapy at 5 dose levels. Rigosertib exposure increased with escalating doses. Dose-limiting toxicities were hematuria and dysuria. The most common grade ≥2 drug-related toxicities involved urothelial irritation. The MTD is 560 mg twice daily. Activity was seen in head and neck SCCs (1 complete response, 1 partial response) and stable disease for ≥12 weeks was observed in 8 additional patients. Tumors experiencing ≥partial response had PI3K pathway activation, inactivated p53, and unique variants in ROBO3 and FAT1, two genes interacting with the Wnt/β-catenin pathway.Conclusions: The recommended phase II dose of oral rigosertib is 560 mg twice daily given continuously. Urinary toxicity is the dose-limiting and most common toxicity. Alterations in PI3K, p53, and Wnt/β-catenin pathway signaling should be investigated as potential biomarkers of response in future trials. Clin Cancer Res; 20(6); 1656–65. ©2014 AACR.

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Supplemental Figure S1: Supplemental Figure 1 shows the pharmacokinetic plasma concentration curve following a single dose of oral rigosertib, revealing dose-dependent pharmacokinetics; Supplemental Table S1: This file provides individual patient characteristics, including demographics, time on study, best response, and duration of response; Supplemental Table S2: Adverse events, including the result of the adverse event (drug holding or dose reduction) are described for each patient; Supplemental Table S3: All serious adverse events are described in this file according to patient identification number, as is the relationship to rigosertib; Supplemental Table S4: This file gives the detailed results of multiplex mutation testing for each patient enrolled in this study whose tumor was analyzed; Supplemental Table S5: Validated exome sequencing results for patients with sensitive and resistant squamous cell carcinomas are described, including gene, position, and nucleotide affected; Supplemental Table S6: This file shows the exome sequencing coverage for each assessed squamous cell carcinoma.

Purpose: Rigosertib, a dual non-ATP inhibitor of polo-like kinase 1 (Plk1) and phosphoinositide 3-kinase pathways (PI3K), and gemcitabine have synergistic antitumor activity when combined in preclinical studies. This phase I study aimed to determine the recommended phase II dose (RPTD) of the combination of rigosertib and gemcitabine in patients with cancer.Experimental Design: Patients with solid tumors who failed standard therapy or were candidates for gemcitabine-based therapy were eligible. Gemcitabine was administered on days 1, 8, and 15 on a 28-day cycle and rigosertib on days 1, 4, 8, 11, 15, and 18. Pharmacokinetic studies were conducted during an expansion cohort of patients with advanced pancreatic ductal adenocarcinoma (PDA).Results: Forty patients were treated, 19 in the dose-escalation phase and 21 in the expansion cohort. Dose levels evaluated were (gemcitabine/rigosertib mg/m2): 750/600 (n = 4), 750/1,200 (n = 3), 1,000/600 (n = 3), 1,000/1,200 (n = 3), and 1,000/1,800 (n = 6 + 21). One dose-limiting toxicity (death) occurred at the highest dose level (1,000/1,800) tested. Non–dose-limiting ≥grade II/III toxicities included neutropenia, lymphopenia, thrombocytopenia, fatigue, and nausea. Grade III/IV neutropenia, thrombocytopenia, and fatigue were seen in two, one, and two patients in the expansion cohort. Partial responses were observed in PDA, thymic cancer, and Hodgkin lymphoma, including gemcitabine-pretreated PDA. The pharmacokinetic profile of rigosertib was not affected by gemcitabine.Conclusion: The RPTD established in this study is rigosertib 1,800 mg/m2 and gemcitabine 1,000 mg/m2. This regimen is well tolerated with a toxicity profile of the combination similar to the profile of gemcitabine alone. Antitumor efficacy was observed in patients who previously progressed on gemcitabine-based therapy. Clin Cancer Res; 18(7); 2048–55. ©2012 AACR.

Aim: To study Effect of β-cyclodextrin and hydroxypropyl β-cyclodextrin on aqueous stability, solubility and dissolution of novel anti-cancer drug Rigosertib. Methods: β-cyclodextrin and hydroxypropyl β-cyclodextrin were used to form complex with Rigosertib. The effect of cyclodextrins on drug solubility was studied using phase solubility method. Physico-chemical characterization of drug cyclodextrin complex was performed using differential scanning calorimeter, X-Ray diffraction, Infrared spectroscopy and Scanning electron microscopy. Dissolution profiles of drug-cyclodextrin complexes showed better drug release compared to untreated drug in pH 1, 2, 4 and 5.5 dissolution medium. Results: Rigosertib exhibits poor solubility and chemical instability in acidic solutions. Poor aqueous stability along with limited solubility in acidic conditions can result in limited oral bioavailability of the drug. Both analogues showed positive effect on drug solubility. Hydroxypropyl β-cyclodextrin performed better compared to β-cyclodextrin to improve drug solubility. In addition, presence of both cyclodextrin analogues improved drug stability in acidic solutions. Physico-chemical characterization of drug cyclodextrin complex was performed using differential scanning calorimeter, X-Ray diffraction, Infrared spectroscopy and Scanning electron microscopy. Dissolution profiles of drug-cyclodextrin complexes showed better drug release compared to untreated drug in pH 1, 2, 4 and 5.5 dissolution medium. Conclusion: Improved drug solubility and chemical stability in acidic conditions can be attributed to complex formation between drug and cyclodextrin.

Phase 1 results from a Phase 1/2 study comprise 18 patients with myelodysplastic syndromes (MDS; n = 9), acute myeloid leukemia (AML; n = 8), and chronic myelomonocytic leukemia (CMML; n = 1) who were either hypomethylating agent naive (n = 10) or relapsed/refractory following prior hypomethylating agent therapy (n = 8) (NCT01926587). Patients received oral rigosertib, an inhibitor of Ras-effector pathways, in 3 successive cohorts (140 mg twice daily, 280 mg twice daily, or 840 mg/day [560 mg morning/280 mg evening]) for 3 weeks of a 4-week cycle. Patients received parenteral azacitidine (75 mg/m2/day × 7 days) during the second week; the cycle repeated every 4 weeks. The combination was well tolerated for a median of 4 (range 1–41) cycles, with 72% of patients experiencing ≥1 serious adverse events. No dose-limiting toxicities were observed. Thus, no maximum tolerated dose was reached. The most frequently reported adverse events were diarrhea (50%), constipation, fatigue, and nausea (each 44%), and pneumonia and back pain (each 33%). Sequential administration demonstrated an overall response rate of 56% in evaluable patients, with responses observed in 7/9 MDS/CMML patients (78%) and 2/7 AML patients (29%). Further clinical studies are warranted to investigate this doublet therapy in patients with myeloid malignancies.

Rigosertib (ON 01910.Na) is an inhibitor of the phosphoinositide 3-kinase and polo-like kinase pathways that induces mitotic arrest and apoptosis in neoplastic cells, while sparing normal cells. Our purpose is to summarize the clinical activity and safety of intravenous (IV) rigosertib delivered by an external ambulatory infusion pump in patients with refractory anemia with excess blasts-1, -2, or, -t myelodysplastic syndromes (MDS) following prior treatment with DNA methyltransferase (DNMT) inhibitors. A total of 39 patients with MDS who fulfilled these criteria were enrolled in four phase 1-2 clinical trials of IV rigosertib. Thirty five (88%) had higher risk disease according to the Revised International Prognostic Scoring System. Median overall survival for this group of 39 patients was 35 weeks. Of 30 evaluable patients with follow-up bone marrow biopsies, 12 (40%) achieved complete (n = 5) or partial (n = 7) bone marrow blast responses. In addition, 15 patients achieved stabilization of bone marrow blasts. One patient with a complete bone marrow response also achieved a complete cytogenetic response. A second patient with stable bone marrow blasts achieved a partial cytogenetic response. Two of the responding patients and three patients with stable disease had hematological improvements. Rigosertib-induced bone marrow blast decreases and stability appeared to be predictive of prolonged survival. IV rigosertib had a favorable safety profile without significant myelosuppression. Most common drug-related toxicities included fatigue, diarrhea, nausea, dysuria, and hematuria. In summary, IV rigosertib is well tolerated and has clinical activity in patients with higher risk MDS following DNMT inhibitor treatment. A multinational pivotal phase 3 randomized clinical trial of rigosertib versus best supportive care for patients with MDS with excess blasts following prior treatment with DNMT inhibitors (ONTIME: ON 01910.Na Trial In Myelodysplastic SyndromE) has recently completed enrollment.

Purpose: To determine the pharmacokinetics (PK), maximum tolerated dose (MTD), safety, and antitumor activity of an oral formulation of rigosertib, a dual phosphoinositide 3-kinase (PI3K) and polo-like kinase 1 (Plk1) pathway inhibitor, in patients with advanced solid malignancies. Experimental Design: Patients with advanced solid malignancies received rigosertib twice daily continuously in 21-day cycles. Doses were escalated until intolerable grade ≥2 toxicities, at which point the previous dose level was expanded to define the MTD. All patients were assessed for safety, PK, and response. Urinary PK were performed at the MTD. Archival tumors were assessed for potential molecular biomarkers with multiplex mutation testing. A subset of squamous cell carcinomas (SCC) underwent exome sequencing. Results: Forty-eight patients received a median of 2 cycles of therapy at 5 dose levels. Rigosertib exposure increased with escalating doses. Dose-limiting toxicities were hematuria and dysuria. The most common grade ≥2 drug-related toxicities involved urothelial irritation. The MTD is 560 mg twice daily. Activity was seen in head and neck SCCs (1 complete response, 1 partial response) and stable disease for ≥12 weeks was observed in 8 additional patients. Tumors experiencing ≥partial response had PI3K pathway activation, inactivated p53, and unique variants in ROBO3 and FAT1, two genes interacting with the Wnt/β-catenin pathway. Conclusions: The recommended phase II dose of oral rigosertib is 560 mg twice daily given continuously. Urinary toxicity is the dose-limiting and most common toxicity. Alterations in PI3K, p53, and Wnt/β-catenin pathway signaling should be investigated as potential biomarkers of response in future trials. Clin Cancer Res; 20(6); 1656–65. ©2014 AACR.

Rigosertib is a novel anticancer drug in clinical development by Onconova therapeutics, Inc. Currently, it is in pivotal phase III clinical trials for myelodysplastic syndrome (MDS) patients. Chemically, it is a sodium salt of weak acid with low solubility in lower pH solutions. In the preliminary studies, it was found that rigosertib is unstable in acidic conditions and forms multiple degradation products. In this research, drug degradation kinetics of rigosertib were studied in acidic conditions. Rigosertib follows pseudo-first-order general acid catalysis reaction. Cholestyramine, which is a strong anion exchange resin, was used to form complex with drug to improve stability and dissolution in acidic conditions. Drug complex with cholestyramine showed better dissolution profile compared to drug alone. Effect of polyethylene glycol was investigated on the release of drug from the drug resin complex. Polyethylene glycol further improved dissolution profile by improving drug solubility in acidic medium.

We previously demonstrated upregulation of c-myc, survivin, and cyclin D1 in CD34+ bone marrow mononuclear cells (BMMNCs) of patients with trisomy 8 and monosomy 7 myelodysplastic syndromes (MDS). "Knockdown" of cyclin D1 by RNA interference decreased trisomy 8 cell growth, suggesting that this might be a therapeutic target in MDS.We performed preclinical studies using BMMNCs from patients with MDS and AML to examine the effects of the styryl sulfone ON 01910.Na on cyclin D1 accumulation, aneuploidy, and CD34+ blast percentage. We next treated twelve patients with higher risk MDS and two trisomy 8 AML patients with ON 01910.Na on a phase I clinical protocol (NCT00533416).ON 01910.Na inhibited cyclin D1 expression, and was selectively toxic to trisomy 8 cells in vitro. Flow cytometry studies demonstrated increased mature CD15+ myeloid cells and decreased CD34+ blasts. Three patients treated with ON 01910.Na on a clinical had decreased bone marrow blasts by ≥ 50%, and three patients had hematologic improvements, one of which was sustained for 33 months. Patients with hematologic responses to ON 01910.Na had decreased cyclin D1 expression in their CD34+ cells.The preclinical results and responses of patients on a clinical trial warrant further investigation of ON 01910.Na as a potential novel targeted therapy for higher risk MDS patients.

The aim of the present study was to assess recovery from hematopoietic and gastrointestinal damage by Ex-RAD , also known as ON01210.Na (4-carboxystyryl-4-chlorobenzylsulfone, sodium salt), after total body radiation. In our previous study, we reported that Ex-RAD, a small-molecule radioprotectant, enhances survival of mice exposed to gamma radiation, and prevents radiation-induced apoptosis as measured by the inhibition of radiation-induced protein 53 (p53) expression in cultured cells. We have expanded this study to determine best effective dose, dose-reduction factor (DRF), hematological and gastrointestinal protection, and in vivo inhibition of p53 signaling. A total of 500 mg/kg of Ex-RAD administered at 24 h and 15 min before radiation resulted in a DRF of 1.16. Ex-RAD ameliorated radiation-induced hematopoietic damage as monitored by the accelerated recovery of peripheral blood cells, and protection of granulocyte macrophage colony-forming units (GM-CFU) in bone marrow. Western blot analysis on spleen indicated that Ex- RAD treatment inhibited p53 phosphorylation. Ex-RAD treatment reduces terminal deoxynucleotidyl transferase mediated dUTP nick end labeling assay (TUNEL)-positive cells in jejunum compared with vehicletreated mice after radiation injury. Finally, Ex-RAD preserved intestinal crypt cells compared with the vehicle control at 13 and 14 Gy. The results demonstrated that Ex-RAD ameliorates radiation-induced peripheral blood cell depletion, promotes bone marrow recovery, reduces p53 signaling in spleen and protects intestine from radiation injury.

Purpose: Rigosertib, a dual non-ATP inhibitor of polo-like kinase 1 (Plk1) and phosphoinositide 3-kinase pathways (PI3K), and gemcitabine have synergistic antitumor activity when combined in preclinical studies. This phase I study aimed to determine the recommended phase II dose (RPTD) of the combination of rigosertib and gemcitabine in patients with cancer. Experimental Design: Patients with solid tumors who failed standard therapy or were candidates for gemcitabine-based therapy were eligible. Gemcitabine was administered on days 1, 8, and 15 on a 28-day cycle and rigosertib on days 1, 4, 8, 11, 15, and 18. Pharmacokinetic studies were conducted during an expansion cohort of patients with advanced pancreatic ductal adenocarcinoma (PDA). Results: Forty patients were treated, 19 in the dose-escalation phase and 21 in the expansion cohort. Dose levels evaluated were (gemcitabine/rigosertib mg/m2): 750/600 (n = 4), 750/1,200 (n = 3), 1,000/600 (n = 3), 1,000/1,200 (n = 3), and 1,000/1,800 (n = 6 + 21). One dose-limiting toxicity (death) occurred at the highest dose level (1,000/1,800) tested. Non–dose-limiting ≥grade II/III toxicities included neutropenia, lymphopenia, thrombocytopenia, fatigue, and nausea. Grade III/IV neutropenia, thrombocytopenia, and fatigue were seen in two, one, and two patients in the expansion cohort. Partial responses were observed in PDA, thymic cancer, and Hodgkin lymphoma, including gemcitabine-pretreated PDA. The pharmacokinetic profile of rigosertib was not affected by gemcitabine. Conclusion: The RPTD established in this study is rigosertib 1,800 mg/m2 and gemcitabine 1,000 mg/m2. This regimen is well tolerated with a toxicity profile of the combination similar to the profile of gemcitabine alone. Antitumor efficacy was observed in patients who previously progressed on gemcitabine-based therapy. Clin Cancer Res; 18(7); 2048–55. ©2012 AACR.

ON 01210.Na (Ex-RAD), a chlorobenzylsulfone derivative was investigated for its pharmacologic and radioprotective properties when administered via oral and subcutaneous (SC) routes. The goals of the study were to assess the comparative bioavailability of ON 01210.Na when administered by oral versus SC routes and to demonstrate that the oral drug delivery of ON 01210.Na afforded survival advantage similar to SC dosing. Pharmacokinetics was studied after two doses, 24 h apart, of ON 01210.Na (500 mg/kg) administered to male C3H/Hen mice (7-9 weeks) via SC injection or oral route. The dose response (100 to 750 mg/kg) and survival advantage of ON 01210.Na administered at 24 h and 15 min prior to 7.5 or 8 Gy whole body irradiation from a ¹³⁷Cs source (dose rate 1 Gy/min) were studied in these mice. Effects on the hematopoietic system were investigated by complete blood count and granulocyte-macrophage colony forming unit assay. A significant survival advantage and hematopoietic protection were observed after prophylactic oral ON 01210.Na and results were comparable to SC administration. These findings correlated well with pharmacokinetic data. Both SC and oral ON 01210.Na showed significant survival advantage against radiation toxicity and ON 01210.Na mediated hematopoietic protection plays key role in enhanced survival of mice. Oral administration holds better clinical promise as an effective countermeasure not only for early-responders in a nuclear accident, but also for the at-risk civilian population.

Introduction: Rigosertib is a small molecule inhibitor of cellular signaling pathways in cancer cells by acting as a Ras mimetic. The inhibitory effect is mediated by Rigosertib binding to the Ras-binding domain found in many Ras effector proteins (Athuluri-Divakar SK, Cell 2016). Oral administration of Rigosertib was initially evaluated in lower risk MDS patients. The drug, administered as 560 mg BID (q12hr; 2/3 wks), was associated with high rates of transfusion independence but with significant GU AEs (Raza, et al, Blood 2017 130:1689). Subsequently, a reduction in the PM dose to 280 mg led to a decrease in GU AEs, suggesting a causal relationship with nocturnal bladder drug concentration. When oral administration of Rigosertib was tested with standard dose of parenteral Azacitidine in a Phase I/II trial (NCT01926587) at a dose of 560/280 mg (Q12hrs, 3/4 weeks), the ORR was 77%; with 60% for the HMA relapsed/refractory group for the high risk MDS patients. The impressive response rate, in the combination treatment, was also associated with significant GU AEs. Hence, it is important to understand the underlying cause and devise ways to maximize response rates with minimization of GU AEs. Previously, it was established that GU AEs were unlikely to be related to the higher systemic exposure of the drug (Maniar, et al ASH 2018, Abstract submitted) but attributed to the nocturnal dwell time of high drug concentration in the bladder of patients treated with continuous oral administration (3/4 weeks). In this investigation, we developed a pharmacokinetic model to simulate the systemic and bladder exposure of Rigosertib after repeated oral dosing. The overall aim was to identify and implement an oral dosing regimen for Rigosertib that would maximize the systemic exposure with minimization of nocturnal bladder concentration, thereby potentially mitigating or eliminating the GU AE's. Methods: A 2-compartment model with 1st order absorption and elimination (Figure 1) was fitted to data collected from patients with solid malignancies at a 560 mg dose (n=25). Model parameter estimates were then used to generate a virtual population of 100 patients. Each virtual patient was randomly assigned parameter values based on the 95% confidence interval for each parameter estimate obtained through the modeling analysis. Model simulations were then performed to evaluate the steady state systemic and urinary exposure of Rigosertib in the virtual population after treatment with different dosing schedules (Figure 2). Besides plasma exposure (Cmax, AUC), the predicted rigosertib bladder concentration during the sleep-cycle was also assessed. From this analysis, optimal dosing regimens were selected for evaluation in a Phase 2 study in HR-MDS patients in combination with Azacitidine. The model was validated by comparing the predicted systemic exposure with observed data using these optimal dosing regimens, and by comparing Grade 3 GU AE's events from the pre- and post-optimization of dosing regimen (NCT01926587). Results: The model-predicted steady state plasma concentration-time profile of Rigosertib for different dosing regimens is shown in Figure 3. The duration of exposure of drug above minimum effective concentration (MEC, 0.175 ug/ml) was not changed by varying the dosing regimen. Importantly, model simulations demonstrated that BID dosing, with the dosing interval of 8 hours, would reduce the bladder concentration of Rigosertib by as much as 70% during sleep without compromising systemic drug exposure (Table 1). As illustrated in Table 2, model simulated Rigosertib exposure (Cmax, AUC) compared favorably with data from patients treated with the novel twice daily dosing regimens (560mg/560mg and 840 mg/280mg, dosing interval of 8 hours), thereby validating the model. Preliminary safety data from the on-going trial demonstrates that the Grade 3 GU AEs were significantly reduced (12%) with the optimized dosing regimen compared to the pre-optimized dosing regimen (29%) despite using a higher total dose of drug (1120 mg vs 840 mg). Conclusions: This study demonstrates the utility of pharmacokinetic modeling for designing a dosing regimen directed at reducing the incidence of toxicity. The identified dosing regimen, along with mitigation strategies, successfully reduced the risk of Grade 3 GU AEs of rigosertib without compromising the duration of systemic exposure of Rigosertib above MEC in HR MDS patients. Disclosures Taft: Onconova Therapeutics, Inc: Research Funding. Ren:Onconova Therapeutics, Inc: Employment, Equity Ownership. Zbyszewski:Onconova Therapeutics, Inc: Employment, Equity Ownership. Morgan:Onconova Therapeutics, Inc: Consultancy. Petrone:Onconova Terapeutics Inc.: Employment, Equity Ownership. Fruchtman:Onconova Therapeutic Inc: Employment, Equity Ownership. Maniar:Onconova Therapeutics, Inc: Employment, Equity Ownership.

Introduction: Oncogenic mutations of Ras genes have been implicated in number of human cancers whereby the cells grow uncontrollably, and evade death signals (Ledford, Nature, 520, 278, 2015). Rigosertib is a small molecule that inhibits cellular signaling in cancer cells by acting as a Ras mimetic (Athuluri-Divakar SK, Cell 2016). Rigosertib, as a single agent, was evaluated in a Phase III clinical trial in refractory MDS patients where the drug was administered as a 3 day continuous IV infusion every other week (NCT01241500). Rigosertib has also been evaluated in Phase I/II trials via oral route of administration in patients with solid malignancies (NCT01168011); and with myelodysplastic syndromes (NCT01926587). We performed pharmacokinetic and safety analysis of 253 patients across three different trials. The pharmacokinetics and safety profile of orally administered Rigosertib was evaluated in patients with MDS and solid malignancies. The results were compared to data obtained from high risk MDS patients receiving intravenous rigosertib therapy. In this investigation, we present evidence that differential GU toxicity of Rigosertib is probably related to the route of administration and dosing regimen; and independent of the underlying disease state. Methods: Data was analyzed from three clinical studies. Study NCT01241500 was conducted with MDS patients (n = 184) who were administered Rigosertib by continuous IV infusion (1800 mg/day for 72 hours) every 2 weeks. Blood samples were collected at 6, 24, 30, 48, 56 and 72 hours after infusion initiation. In Study NCT01168011, patients with advanced solid tumors (n=33) received oral Rigosertib (560 mg) Q12 hours of a 28-day cycle (3 weeks on, 1 week off). Study NCT01926587, conducted in MDS patients (n=36) with oral administration Rigosertib in combination with parenteral Azacitidine, evaluated the same AM dose but a lower 280 mg PM dose. In both studies, pharmacokinetic assessment was conducted after administration of the AM dose (560 mg) on day 1 of cycle 1. Blood samples were collected predose and 0.5, 1, 1.5, 2, 4, 6 and 8 hours after administration. For Study NCT01168011, urine was collected for 24 hours (0-4, 4-8 and 8-24 hrs) to determine the percent of dose excreted in urine. Rigosertib concentrations in plasma and urine were determined by a validated LC/MS-MS method. Rigosertib pharmacokinetic parameters were estimated using non-compartmental analysis. Treatment emergent adverse events were recorded throughout each study. Results: There was no difference in Rigosertib pharmacokinetic parameters between the two patient populations (Table 1) upon oral administration, and the plasma concentration-time profiles were super imposable (Figure 1). Approximately 2% of the orally administered dose was recovered in the urine. In both studies, the most common AEs observed were GU AEs (dysuria, hematuria). The incidence of grade ≥2 GU toxicity observed with oral dosing was 17 of 33 (52%) and 17 of 36 (47%) in Study NCT01168011 and NCT01926587, respectively. The incidence of GU AEs in both the studies was comparable even though the PM dose was lower (560 mg vs 280mg) in study NCT01926587. Peak plasma concentration and AUC0-∞ were similar in patients with or without urinary symptoms. Compared to oral dosing, the incidences of GU AEs were dramatically lower (10%) following IV infusion despite 8-fold higher and more prolonged systemic exposure (Table 2). Conclusions: This study demonstrates that the urinary adverse events and systemic exposure are similar in patients with either solid malignancies or MDS treated with orally administered rigosertib. The incidence of GU AEs is relatively high in spite of the very low amount (2%) of the administered dose eliminated through the renal route. In contrast, the GU AEs are significantly lower when Rigosertib is administered by IV infusion despite of 8 fold higher exposure. This is probably due to the short half-life of drug and dosing holiday of 12 days between two doses within the cycle. The higher incidence of GU AE upon oral administration is likely related to the dwell time of high concentration of drug in the bladder at night in patients treated daily for 3/4 weeks. This was successfully addressed in the clinical trial, NCT01926587 expansion with risk mitigation strategies, by deploying a novel dosing regimen derived through pharmacokinetic modeling and simulation (Taft, et al; ASH 2018 Abstract Submitted). Disclosures Maniar: Onconova Therapeutics, Inc: Employment, Equity Ownership. Ren:Onconova Therapeutics, Inc: Employment, Equity Ownership. Zbyszewski:Onconova Therapeutics, Inc: Employment, Equity Ownership. Petrone:Onconova Terapeutics Inc.: Employment, Equity Ownership. Fruchtman:Onconova Therapeutic Inc: Employment, Equity Ownership. Taft:Onconova Therapeutics, Inc: Research Funding.

Background: AZA is first line therapy for pts with HR-MDS with an overall response rate (ORR) between 35 and 60% in various publications; with CR/PR rates ranging between 23 and 29% in 3 randomized phase II/III studies (Silverman et al., JCO 2002; Fenaux et al., Lancet Oncol 2009; Sekeres, JCO 2017). AZA also has demonstrated efficacy in older pts with AML (Dombret et al., Blood 2015; Fenaux et al., JCO 2010). Rigosertib interferes with the RAS-binding domains of RAF kinases and inhibits the RAS-RAF-MEK and the PI3Ks pathways (Athuluri-Divakar, Cell 2016). RAS and other genes in this pathway are frequently mutated in HR MDS and putatively drive the malignant clone (Sperling et al., Nat Rev CA 2017). In vitro, the combination of rigosertib with AZA synergistically inhibits growth and induces apoptosis of leukemic cells in a sequence-dependent fashion (Skidan et al; AACR 2006 Abstract 1310). In a trial in lower-risk MDS, oral rigosertib was studied as a single agent at various doses including 560 mg BID for 14-21 days in 28 day cycles and yielded a transfusion independence (TI) rate of 44% - the highest reported TI rate (Raza, ASH Abstract #108660 2017). Based on this observation we expanded the ongoing Phase I/II trial and tested rigosertib at a total of 1120 mg per day with standard dose parenteral AZA (75mg/m2 x 7 days q28 days) in two different schemes as described in methods (NCT01926587). At a dose of 560 mg AM, 280 mg evening the ORR was 77%; 88% for the HMA naïve group and importantly 60% for the HMA Rel/Ref group. Of note, adverse events of interest have been genitourinary (GU) toxicities, particularly hematuria and dysuria. Thus, risk-mitigation strategies (Table 1) were employed to minimize hematuria with higher dose rigosertib at 1120 mg; including the rationale for the lower afternoon (280 mg) dose. We report here the initial results of efficacy and safety. Methods: In the Phase II Expansion cohort, up to 45 pts with HR MDS/RAEB-t/non-proliferative AML were randomized 1:1 into 2 cohorts both to receive 1120 mg of rigosertib over 24 hours: either 560 mg in the morning and 560 mg in the afternoon, or 840 mg in the morning and 280 mg in the afternoon (part of hematuria/dysuria risk mitigation; moving second dose from evening to afternoon to minimize overnight bladder dwell time as permitted by PK analysis (Maniar, ASH Abstract 2018). Each cohort is stratified among HMA naïve and HMA Rel/Ref pts. Hematologic response is determined per IWG 2006. Results: As of July 2018 in the rigosertib 1120 mg cohort in combination with AZA, 45 pts were enrolled; 43 treated, 31 evaluable for response; 14 pts continue on treatment, and 31 pts discontinued (includes 2 enrolled but not treated). To be evaluable for response, a minimum of 12 weeks of the doublet was required. Of the 31 pts evaluable for response, 17 pts are prior Rel/Ref, 14 pts are HMA naïve. The # of prior HMA cycles is 2-15; 13 failed AZA; 1 failed DAC; 2 failed both; and 1 failed other (experimental). The median duration of treatment at this time point for the overall population is 5 months (1-14+). The ORR (Table 2) for the all patients is 68%; 59% for the prior Rel/Ref cohort and 79% for the HMA naïve cohort. For responding patients, responses are seen in both 1120 mg cohorts as shown. Safety: In 43 patients treated with oral rigosertib at 1120 mg and AZA, with risk-mitigating strategies to minimize hematuria, Grade 1 & 2 hematuria = 16%; ≥3 Grade Hematuria = 5% have been seen to date (Table 3). This compares to an incidence of 12 % Gr 3 hematuria at a lower dose of rigosertib (840 mg); and prior to risk mitigation strategies. Incidence of hematuria of any grade with single agent AZA is 6.3 % & Grade ≥3 2.3% (VIDAZA, package insert 2004). Conclusion: The combination of oral rigosertib and AZA in HMA naïve patients with HR-MDS is encouraging compared to single agent AZA. The combination also has activity and reverses the HMA clinical resistance in a substantial number of patients after Rel/Ref, a finding with potentially significant clinical implications. Dose exploration with a higher dose of oral rigosertib (1120mg) administered in different dosing schemes in combination with standard dose AZA continues to be studied to optimize safety and efficacy. By employing risk mitigation strategies, the incidence of GU AEs, including hematuria, has been substantially reduced. We will update the safety and efficacy data at the time of presentation. Based on this data a pivotal trial is planned. Disclosures Navada: Onconova: Research Funding. Atallah:Pfizer: Consultancy; Abbvie: Consultancy; Jazz: Consultancy; BMS: Consultancy; Novartis: Consultancy. Shammo:Incyte: Consultancy, Honoraria, Research Funding; Onconova: Other: research support; Alexion: Honoraria, Other: research support; Novartis: Consultancy, Honoraria; Celgene: Other: research support. Griffiths:Novartis, Inc.: Research Funding; Celgene, Inc: Honoraria, Research Funding; Astex/Otsuka Pharmaceuticals: Honoraria, Research Funding; Pfizer, Inc.: Research Funding; Alexion Inc.: Honoraria, Research Funding. Khaled:Juno: Other: Travel Funding; Alexion: Consultancy, Speakers Bureau; Daiichi: Consultancy. Pemmaraju:abbvie: Research Funding; stemline: Consultancy, Honoraria, Research Funding; celgene: Consultancy, Honoraria; Affymetrix: Research Funding; samus: Research Funding; SagerStrong Foundation: Research Funding; cellectis: Research Funding; daiichi sankyo: Research Funding; novartis: Research Funding; plexxikon: Research Funding. Zbyszewski:Onconova Therapeutics, Inc: Employment, Equity Ownership. Maniar:Onconova Therapeutics, Inc: Employment, Equity Ownership. Petrone:Onconova Terapeutics Inc.: Employment, Equity Ownership. Fruchtman:Onconova Therapeutic Inc: Employment, Equity Ownership. Silverman:Johnson and Johnson: Research Funding; Onconova Therapeutics Inc.: Patents & Royalties, Research Funding; Bayer: Research Funding; Celgene: Research Funding; Medimmune: Research Funding; Mount Sinai School of Medicine: Employment.

Purpose: To evaluate gender differences in the metabolism of ON 123300 in rats in vitro and in vivo. ON 123300, a novel small molecule dual inhibitor of the c-MYC activated kinases ARK5 and CDK4/6, is being developed by Onconova Therapeutics, Inc. as a novel anti-cancer drug candidate. Methods: In vitro metabolism experiments were performed in rat liver microsomes from male and female donors. ON 123300 was incubated with microsomes, and samples were withdrawn at specified times over 60 minutes and, immediately quenched and centrifuged. The supernatant was analyzed for ON 123300 and its metabolites by HPLC. An in vivo pharmacokinetic study was performed in male and female SD rats. ON 123300 was administered as a single oral dose (100 mg/kg), and blood samples were collected over 24 hours. ON 123300 concentrations were measured by LC-MS/MS. Pharmacokinetic parameters were estimated by non-compartmental analysis. Results: The results are provided in Table 1. ON 123300 displayed more rapid microsomal degradation in vitro (increase of Clint) in males compared to females. This translated into a significantly higher exposure of ON 123300 (3 fold increase of AUC) following oral administration to female rats. Based on these results, the higher plasma concentrations observed in females can be primarily attributed to reduced hepatic clearance compared to males. Conclusions: Gender differences in pharmacokinetics and pharmacodynamics can potentially impact the design of safe and effective dosing regimens for treatments. This investigation demonstrated a significantly lower metabolism of ON 123300 in female rats, which resulted in dramatically high systemic exposure. Additional testing is warranted to assess the potential clinical implications of these findings. Table 1. ON 123300 In Vitro and In Vivo Pharmacokinetic Parameters In Vitro Metabolism (n = 2/group)In Vivo Pharmacokinetics (n = 5/group)Parameter (mean)MalesFemalesParameter (mean± SD)MalesFemalest1/2 (min)10.838.2Tmax (hr)2.3 ± 1.60.6 ± 0.2Clint (ml/min/mg)13036.7Cmax (ng/ml)321 ± 66.01253 ± 660Predicted In Vivo Cl(ml/min/kg)a239.267.5AUC0-∞ (ng-hr/ml)1803 ± 7575520 ± 2163Cl/F (ml/min/kg)1116 ± 474390 ± 269t1/2 (hr)1.9 ± 0.503.0 ± 0.5 apredicted from venous equilibration model assuming rat blood flow = 13.8 ml/min, 99% protein binding and blood:plasma ratio = 1 Citation Format: Chen Ren, Jennypher Mudunuru, David Taft, Manoj Maniar. Effect of gender on the rodent pharmacokinetics of ON 123300, a dual inhibitor of ARK5 and CDK4/6, for the treatment of cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4906.

ON 01910.Na is a novel targeted anti-cancer agent under clinical investigation in Phase I and II trials. The purpose of this research was to evaluate the pharmacokinetic profile of ON 01910.Na across several species, and to evaluate the effects of protein binding and duration of exposure on its in vitro cytotoxic activity. Data were collated from several preclinical investigations, where the plasma disposition and tissue distribution of ON 01910.Na were assessed after administration (10–150 mg/kg, IP or IV) to several species (mouse, rat, and dog). Plasma protein binding was assessed using ultrafiltration. Cytotoxic activity of ON 01910.Na was determined in DU145 cells, and activity was correlated to unbound drug concentration and the duration of exposure. ON 01910.Na exhibits extensive plasma protein binding and the compound displays rapid elimination from the circulation in all three animal species (t1/2 range 0.404–0.870 h). Tissue distribution studies in mice revealed highest drug accumulation in the liver, followed by the kidneys. ON 01910.Na is not extensively metabolized in vivo and urinary excretion is predominant at higher doses. ON 01910.Na cytotoxicity in DU145 cells was adversely affected by protein binding in the incubation medium. Drug cytotoxicity was greatly enhanced upon extending the duration of exposure at reduced drug concentrations. Due to the short half-life and rapid clearance of the drug, administration of ON 01910.Na by continuous IV infusion is a likely treatment option for cancer patients.

Ex-Rad is among a series of small molecule kinase inhibitors developed for modifying cell cycle distribution patterns in cancer cells subjected to radiation therapy, and it has been identified as a potential candidate for radiation protection studies. We have investigated its radioprotective efficacy using mouse and in vitro models. Thirty-day survival studies with C3H/HeN male mice revealed 88% survival when 500 mg/kg of Ex-Rad was injected subcutaneously 24 h and 15 min before gamma irradiation with 8.0 Gy. To understand Ex-Rad's mechanism of action, we also studied its radioprotective efficacy in lung fibroblast (HFL-1), skin fibroblast (AG1522) and human umbilical vein endothelial cells (HUVECs). Colony-forming assays indicated that Ex-Rad protected cells from radiation damage after exposure to (60)Co gamma radiation. A study using single-cell gel electrophoresis (SCGE; also known as the alkaline comet assay) showed that Ex-Rad protected cells from radiation-induced DNA damage. Western blot analyses indicated that the radiation protection provided by Ex-Rad resulted in reduced levels of pro-apoptosis proteins such as p53 as well as its downstream regulators p21, Bax, c-Abl and p73, indicating that Ex-Rad could rescue cells from ionizing radiation-induced p53-dependent apoptosis. In conclusion, it appears that Ex-Rad's radioprotective mechanisms involve prevention of p53-dependent and independent radiation-induced apoptosis.

Background Rigosertib (ON 01910.Na), a first-in-class Ras mimetic and small-molecule inhibitor of multiple signaling pathways including polo-like kinase 1 (PLK1) and phosphoinositide 3-kinase (PI3K), has shown efficacy in preclinical pancreatic cancer models. In this study, rigosertib was assessed in combination with gemcitabine in patients with treatment-naive metastatic pancreatic adenocarcinoma. Materials and methods Patients with metastatic pancreatic adenocarcinoma were randomized in a 2:1 fashion to gemcitabine 1000 mg/m2 weekly for 3 weeks of a 4-week cycle plus rigosertib 1800 mg/m2 via 2-h continuous IV infusions given twice weekly for 3 weeks of a 4-week cycle (RIG + GEM) versus gemcitabine 1000 mg/m2 weekly for 3 weeks in a 4-week cycle (GEM). Results A total of 160 patients were enrolled globally and randomly assigned to RIG + GEM (106 patients) or GEM (54). The most common grade 3 or higher adverse events were neutropenia (8% in the RIG + GEM group versus 6% in the GEM group), hyponatremia (17% versus 4%), and anemia (8% versus 4%). The median overall survival was 6.1 months for RIG + GEM versus 6.4 months for GEM [hazard ratio (HR), 1.24; 95% confidence interval (CI) 0.85–1.81]. The median progression-free survival was 3.4 months for both groups (HR = 0.96; 95% CI 0.68–1.36). The partial response rate was 19% versus 13% for RIG + GEM versus GEM, respectively. Of 64 tumor samples sent for molecular analysis, 47 were adequate for multiplex genetic testing and 41 were positive for mutations. The majority of cases had KRAS gene mutations (40 cases). Other mutations detected included TP53 (13 cases) and PIK3CA (1 case). No correlation between mutational status and efficacy was detected. Conclusions The combination of RIG + GEM failed to demonstrate an improvement in survival or response compared with GEM in patients with metastatic pancreatic adenocarcinoma. Rigosertib showed a similar safety profile to that seen in previous trials using the IV formulation.

GBO-006 was shown to be a highly specific and selective PLK2 inhibitor that promoted mitotic arrest in various cancer cell lines, subsequently resulting in their apoptotic death. Intraperitoneal alternate day dosing of GBO-006 using 100 % DMSO as formulation showed significant tumor regression in xenograft models, demonstrating proof of concept of PLK2 inhibition in vivo. These studies necessitated the development of a suitable and GRAS (generally considered as safe) preformulation for pharmacokinetic and efficacy studies. GBO-006 possesses challenging physicochemical and biopharmaceutical properties like poor solubility in aqueous media, low permeability and a crystalline nature. Different methods like cosolvency, complexation and micellar solubilization were employed to improve the solubility of GBO-006. A strategy of co-solvency is used to solubilize the GBO-006 up to 10 mg/mL. A formulation with 20 % DMSO, 40 % PEG 400, 30 % of 100 mM citrate buffer (pH 3.0) and 10 % solutol displayed clear solution without any visual precipitation of the drug even after 2 weeks of storage. GBO-006 showed moderate clearance in rat and high systemic clearance in mouse and dog. It showed poor oral bioavailability across all species. Intraperitoneal dosing of GBO-006 demonstrated the linear exposure. GBO-006 showed significant inhibition of tumor progression.

ON 01210.Na is a chlorobenzylsulfone derivative with potential property to mitigate the effects of accidental or intentional exposure to life threatening levels of radiation. A simple and sensitive HPLC method was developed and validated for the assay of ON 01210.Na. The isocratic system used a mobile phase consisting of acetonitrile:0.1% trifluroacetic acid in water (60:40, v/v) at a flow rate of 1 ml/min. The method used a C-18 Gemini column (250 mm x 4.6 mm) with column effluents monitored at 254 nm. Forced degradation of the drug was achieved by autoclaving ON 01210.Na with 0.05 N HCl, 0.05 N NaOH or 1.5% (v/v) hydrogen peroxide. The assay validation parameters evaluated include specificity, linearity, precision, accuracy and sensitivity. The retention time of the drug and the other effluents were well within 7 min. Standard curves were linear over the concentration range of 10-500 microg/ml. The R.S.D. values for the within-day and day-to-day precision ranged from 0.4 to 2.5 and 2.2 to 4.4%, respectively. The R.S.D. for accuracy measurement ranged from 0.85 to 1.7%. The critical level, the detection level and the determination level for this assay were 2.86+/-0.67, 5.69+/-0.67 and 15.6+/-1.8 microg/ml, respectively. A simple, sensitive and stability indicating HPLC assay was developed and validated for the analysis of a novel radioprotectant. This method was used to evaluate the aqueous as well as solid-state stability of this drug during autoclaving.

Background: The overexpression of cyclin-dependent kinases 4/6 (CDK4/6) is known to cause cell cycle dysregulation in certain cancer types, making these cell cycle kinases attractive targets for pharmacological inhibition. The effectiveness of first-generation non-selective cyclin-dependent kinases, such as roscovitine and flavopiridol, was hampered by toxicities, leading to the development of second-generation compounds like IBRANCE®/Palbociclib that specifically inhibit CDK4 and 6. ON 123300 is a third-generation potent CDK4/6 inhibitor that also inhibits ARK5 with low nanomolar potency and has the potential to improve upon second-generation compounds. Previous studies have demonstrated the inhibitory effect of single-agent ON 123300 in various pre-clinical cancer models of MM and leukemia. In this study, we investigated the comparative therapeutic potential of ON 123300 as an oral anticancer agent and a second-generation inhibitor, Palbociclib, in xenografted Rb+ve mouse models. Methods: MDA-MB-435S xenografted mice were treated once a day for 21 days with ON 123300 (125mg/kg) or Palbociclib (125mg/kg). Tumor volumes were measured and peripheral blood was gathered to evaluate the effects on hematological parameters. Separately, Western blot analyses were performed to determine the effect of CDK4/6 inhibition on p-Rb following intra-tumoral treatment with ON 123300 (2.5µM) or Palbociclib (2.5µM). Results: ON 123300 and Palbociclib reduced tumor growth with an equivalent magnitude during the 21-day treatment period, suggesting that the two compounds were equally effective in this model. Both compounds decreased RBC and platelet counts, however Palbociclib had a more prominent and statistically significant (P≤0.05) inhibitory effect on neutrophil counts when compared to ON 123300 (30.70 ± 3.55 vs. 45.10 ± 2.04). Western blot analysis of tumor tissues demonstrated equivalent effects on p-Rb for both compounds. Conclusions: Xenograft data indicates that a third-generation CDK4/6 inhibitor, ON 123300, is as effective as Palbociclib in an Rb+ve xenograft model. Moreover, this study also suggests that ON 123300 may have the added advantage of reduced neutropenia compared to Palbociclib. Prior preclinical data suggest that ON 123300 may be efficacious in Rb-ve tumors, where second-generation compounds have diminished single-agent activity, and our ongoing studies are aimed at further characterizing the in vivo activity of ON 123300 in this setting. Citation Format: Shraddha Patel, Priya Pancholi, Tanvi Visal, Amruta Samant, Dhvanir Kansara, V J. Rajadhyaksha, Benjamin S. Hoffman, Manoj Maniar, Vikas Sehdev. ON 123300, an orally administered novel CDK4/6 + ARK5 inhibitor, exhibits potent antitumor activity in vivo: comparative studies with Palbociclib [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2172. doi:10.1158/1538-7445.AM2017-2172

Fatty acid terminated polyanhydrides suitable for use as controlled release matrices in biodegradable sustained release drug delivery systems and methods for making thereof as described. The polymers are more soluble in organic solvents, and have a lower melting point than the corresponding non-fatty acid terminated polyanhydrides. The fatty acid terminated polyanhydrides are also more hydrophobic than the corresponding polyanhydrides that are not terminated with a fatty acid, and combine the properties of thermodynamic and hydrolytic stability, and easy storage. The polymers can be produced with a controlled and low molecular weight. The polyanhydrides are useful in a number of applications, including as a matrix in biodegradable drug delivery systems.

A new class of fatty acid dimer-based polyanhydride, poly(fatty acid dimer-sebacic acid) (P(FAD-SA)), was reported to have desired physicochemical and mechanical properties for a biodegradable device and believed to undergo pure surface erosion. The objectives of this study were to determine if P(FAD-SA) undergoes pure surface erosion, and to identify the factors governing the release characteristics and mechanism from polyanhydride devices at various pHs. Three model compounds, mannitol (small Mw, highly water soluble), inulin (large Mw, moderately water soluble) and stearic acid (medium Mw, extremely lipophilic) were incorporated at 10% w/w in disk-shaped P(FAD-SA, 50:50 w/w) devices and the release of the compounds studied from pH 1–9. All the three model compounds were released faster at alkaline pH than at acidic pH (pH 9>pH 7.4>pH 1–5), suggesting that the release of model compounds was dependent on the base catalyzed erosion of polyanhydride. However, erosion was not the sole release rate controlling mechanism for these model compounds. Highly water soluble mannitol and inulin were released rapidly at acidic pH, when erosion of polyanhydride is negligible. Mannitol released faster than inulin, which was released faster than lipophilic stearic acid at all pH, suggesting that the hydrophilic/hydrophobic nature of the loaded compound influenced its release significantly. The observed release profiles were significantly higher, and did not match the release profiles predicted from erosion rates of the mannitol and inulin devices, however they were closer for stearic acid devices. Although inulin was released rapidly in the initial phase (40–50%), only 60–70% inulin was released over a 6-week period compared to 100% release of mannitol. The large molecular size of inulin may have hindered its diffusion through water-filled pores and channels observed in the devices during release, which may have resulted in the majority of inulin being still trapped in the devices. Although various contributing factors in overall release were identified, a single release kinetic model could not explain the release profiles of all the loaded compounds under the different pH conditions. The complete release profiles could be described by first order kinetics, however the initial release profiles of all the model compounds were described very well by zero order kinetics. The release rates of mannitol and inulin were influenced by both the erosion rates and the intrinsic dissolution rates unlike release rates of stearic acid which correlated closely with erosion rates. This may be due to the fact that different release mechanisms, such as diffusion, dissolution and erosion all play a significant role in overall release of compound from this newly developed P(FAD-SA) device. However, the contribution of each process to overall release may vary as a function of pH, the nature of the compound and polymer erosion. In conclusion, the results suggest that P(FAD-SA, 50:50 w/w) is undergoing bulk erosion rather than the desired surface erosion. If it did undergo surface erosion, release characteristics would be independent of the physicochemical nature of the incorporated compound and release kinetics would be zero order from disk-shaped devices irrespective of the nature of the loaded compound.

Polyanhydrides are known as surface eroding biodegradable polymers since they are hydrophobic, which is believed to prevent penetration of water into the bulk and hence only the labile bonds on the surface are hydrolyzed. We wanted to test the hypothesis that polyanhydrides, specifically poly(fatty acid dimer-sebacic acid; FAD-SA) undergo pure surface erosion. If P(FAD-SA) does indeed undergo pure surface erosion, very little water should be present in the device since the polymer is hydrophobic and hydrolyzed on contact with water. An understanding of water uptake is also necessary to predict the stability and release of the incorporated drug. The specific aims of this study were to establish the rate of water uptake into P(FAD-SA) devices of cylinder and disk shapes at various pH conditions, and to study the effect of loaded model drug compounds (having different molecular size, aqueous solubility and dissolution rate) on water uptake. The model compounds included: mannitol, inulin and stearic acid, loaded at 10% (w/w) in disk-shaped devices. Water uptake was estimated from the amount of tritiated water found in the devices after they were soaked and gently mixed with buffers (pH 1–9) containing tritiated water (1 μCi/ml) at various time intervals. The results showed that water uptake by the device is a function of pH (pH 9 > pH 7.4 ⋙ pH 1–5). Significantly higher amount of water was taken up at pH 7.4 and 9.0 (8–9% (v/v) for cylindrical devices, 15–25% (v/v) for disk-shaped device in 2 weeks), compared to less than 5% (v/v) uptake between pH 1 and 5. Disk-shaped devices showed a faster uptake rate compared to cylinder-shaped devices due to their higher surface area to volume ratio. The loaded compounds had no significant effect on either the water uptake profile or water uptake kinetics at all pH values examined. From the large amount of water (up to 20% (v/v)) found in the devices at pH 7.4 and pH 9.0, it appears that P(FAD-SA) does not undergo pure surface erosion. The photomicrographs of the devices at various stages of water uptake showed channels on the rough surface indicative of bulk erosion rather than pure surface erosion.

Polyanhydrides are known as surface eroding biodegradable polymers since they are hydrophobic, which is believed to prevent penetration of water into the bulk and hence only the labile bonds on the surface are hydrolyzed. We studied the effects of pH of the erosion medium and incorporation of model compounds of various molecular size and aqueous solubility on erosion of polyanhydride, specifically P(fatty acid dimer-sebacic acid; FAD-SA), as measured by weight loss of the device. The model compounds included: mannitol, inulin and stearic acid, loaded at 10% w/w in disk shaped devices. The devices were prepared by the melt-casting technique and weight loss accurately measured after agitating the devices in buffers (pH 1–9), and removing the device at selected time intervals and freeze-drying the device. All the devices, irrespective of the nature of the model compounds loaded, eroded rapidly at pH 9, 8–10 times faster than at pH 1–5 and 1.3–2 faster than at pH 7.4. The pH-dependent nature of erosion was attributed primarily to the lability of the anhydride linkages to the alkaline pH and higher solubility of the degradation product, SA, resulting in rapid diffusion and dissolution of SA out of the devices. Loading water-soluble compounds such as mannitol and inulin even at 10% w/w accelerated erosion rates at all pH however, the effect was more significant at alkaline pH. In contrast, loading poorly water-soluble compounds such as stearic acid retarded the erosion rates of devices at all pH except at pH 9, where stearic acid is ionized and has higher aqueous solubility. The photomicrographs of the surface of the devices showed pores and channels surrounding island of material believed to be FAD, the pores and channels being bigger for the mannitol- and inulin-loaded devices. Based on these observations, it appears that water-soluble compounds will be released rapidly creating pores and channels in the device, which will be penetrated by water rapidly resulting in accelerated erosion. While poorly water-soluble compound such as stearic acid retards erosion. Therefore, erosion of biodegradable polyanhydride device is not simply a function of polyanhydride chemistry but also involves water uptake, diffusion and dissolution of the degradation products and hence is a function of both pH and the nature of the compounds incorporated into the device. From product development standpoint, influence of the drug's physicochemical characteristics on device erosion should be considered to determine its release characteristics and in vivo lifetime of the device.

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).

The multi-kinase inhibitor rigosertib (ON 01910.Na) induces mitotic arrest and apoptosis in myeloblasts, while sparing normal cells. The purpose of this study was to determine the pharmacokinetic profile, maximum-tolerated dose (MTD), safety, and clinical activity of an oral formulation of rigosertib in patients with myelodysplastic syndromes (MDS). For pharmacokinetic studies, patients received rigosertib in single escalating weekly doses. To determine the MTD, patient cohorts received escalating doses of rigosertib twice daily for 14 d of a 21-d cycle. Overall, 37 patients were treated. Rigosertib exposure increased with escalating oral doses. Mean absolute oral bioavailability ranged from 13·9% (fed) to 34·8% (fasting) in 12 patients treated at the 560 mg b.i.d. dose level. Dose-limiting toxicity (grade 3 dysuria and shortness of breath) occurred at the 700 mg b.i.d. dose. Five patients experienced grade 3 non-haematological toxicity, including symptoms of urothelial inflammation, hypotension and syncope, fatigue and abdominal pain. Encouraging signs of clinical activity included two bone marrow complete remissions in refractory anaemia with excess blasts type 1 patients previously treated with azacitidine. In addition, four patients each achieved transfusion independence and haematological improvements. In conclusion, oral rigosertib is bioavailable and well tolerated, and has clinical activity in patients with MDS.

Background: Rigosertib (RIG) is a RAS-mimetic interacting with the RAS-binding domains of RAF kinases, preventing their binding to RAS and inhibiting the RAS-RAF-MEK pathway. Rigosertib also binds to the RAS-binding domains of Ral-GDS and PI3Ks (Athuluri-Divakar, et al, Cell 165:643, 2016). Mutations of RAS are involved in proliferative processes important in neoplastic transformation (Gil-Bazo, et.al, Cancer Biology and Therapy 17:719, 2016). As of May 2016, 557 patients with MDS or AML received IV (N=335) or oral (N=222) rigosertib. All IV rigosertib was administered as monotherapy. Oral rigosertib was administered as monotherapy (N=168) or in combination with injectable azacitidine (AZA; N=54). Safety results across this rigosertib development program have not been presented. Methods: We reviewed all treatment-emergent adverse events (TEAEs) among patients with MDS/AML treated with rigosertib IV monotherapy, rigosertib oral monotherapy, or in combination therapy, overall and by grade of severity, and serious TEAEs and TEAEs leading to discontinuation. Due to the unexpected observation of urinary AEs, including occasional gross hematuria, we analyzed urinary AEs in greater detail. Results: Rigosertib IV monotherapy: The most common TEAEs were fatigue (33%), nausea (33%), diarrhea (27%), constipation (25%), anaemia (24%) and pyrexia (24%). The most common ≥Grade 3 AEs were anaemia (21%), febrile neutropenia (13%), pneumonia (12%) and thrombocytopenia (11%). The most common serious AEs were febrile neutropenia (10%), pneumonia (9%), and sepsis (7%). The most common AEs leading to discontinuation of IV rigosertib were sepsis and pneumonia (3% each) (Table 1). Rigosertib oral monotherapy: The most common TEAEs were pollakiuria (increased urinary frequency) (35-%), fatigue (32%), diarrhoea (26%), dysuria (29%) and haematuria (24%). The most common ≥Grade 3 AEs were anaemia (17%), thrombocytopenia (5%), haematuria (4%) and urinary tract infection (4%). The most common serious AE was pneumonia (6%). The most common AEs leading to discontinuation of patients receiving oral rigosertib as monotherapy were (dysuria [8%], urinary tract pain [7%], haematuria [5%] and urinary frequency [5%] (Table 2). Rigosertib oral in combination with azacitidine (AZA): The most common TEAEs were nausea (41%), fatigue (39%), diarrhea (37%), constipation (37%) and dysuria (28%). The most common serious AEs were pneumonia (11%) and febrile neutropenia (7%). The most common AEs leading to discontinuation were AML (4%) and pneumonia (4%) (Table 3). In patients fully evaluable for gross hematuria the cause of bleeding was bladder inflammation. Urinary and plasma concentration of RIG were examined to assess dose relationship. According to the azacitidine package insert, the incidence of gross hematuria of any grade with single agent azacitidine is 6.3 % and Grade 3-4 of 2.3%. Evaluations performed of hematuria among 5 studies of oral rigosertib (4 monotherapy and 1 in combination with AZA) in patients with MDS/AML (Table 4). Conclusions: Rigosertib IV or oral formulations were generally well tolerated in clinical trials in over 500 patients with MDS/AML. Gastrointestinal AEs were most frequently reported with IV rigosertib and genitourinary AEs were seen more often with oral than IV dosing. The greater rate of urinary AEs in the oral than in the IV studies indicates a need for close monitoring of these patients and proactive risk management, such as adequate hydration, timing of administration of the second dose, and bladder emptying prior to sleep. Studies are being designed to optimize dosing and schedule to maximize efficacy and minimize hematuria of single agent oral rigosertib. A randomized trial of oral rigosertib/azacitidine versus azacitidine will be required to optimize the clinical benefit and safety in the management of higher-risk patients with MDS. Disclosures Fenaux: Celgene: Honoraria, Research Funding; Janssen: Research Funding; Novartis: Honoraria, Research Funding; Astex: Research Funding; Teva: Honoraria, Research Funding. Al-Kali:Celgene: Research Funding; Onconova Therapeutics, Inc.: Research Funding. Navada:Onconova Therapeutics, Inc.: Research Funding. Roboz:Agios, Amgen, Amphivena, Astex, AstraZeneca, Boehringer Ingelheim, Celator, Celgene, Genoptix, Janssen, Juno, MEI Pharma, MedImmune, Novartis, Onconova, Pfizer, Roche/Genentech, Sunesis, Teva: Consultancy; Cellectis: Research Funding. Santini:Celgene: Consultancy, Honoraria, Research Funding; Janssen: Consultancy, Honoraria; Novartis: Consultancy, Honoraria; Onconova: Consultancy; Amgen: Consultancy; Astex: Consultancy. Platzbecker:Onconova, Teva, Celgene, Janssen, Novartis, Amgen: Honoraria, Research Funding. Petrone:Onconova Therapeutics, Inc.: Employment. Brownstein:Onconova Therapeutics, Inc.: Consultancy. Zbyszewski:Onconova Therapeutics, Inc.: Employment. Maniar:Onconova Therapeutics, Inc.: Employment. Silverman:Onconova Therapeutics, Inc.: Patents & Royalties: Co-Patent holder for the combination of azacitidine and rigosertib, Research Funding.

Background: Upper Gastrointestinal Cancers (UGCs) respond poorly to conventional chemotherapy due to overactive intrinsic mechanisms that mediate drug resistance.] Rigosertib is an investigational anticancer agent, that inhibits cellular signaling by acting as a Ras mimetic to effect the activation of multiple pathways associated with oncogenic transformation and drug resistance. Previous studies have demonstrated the inhibitory effect of rigosertib with conventional platinum based anticancer agents in various pre-clinical cancer models. We hypothesized that the novel mechanism of action of rigosertib would complement the DNA-damaging activity of Cisplatin (CDDP), the standard of care in UGC. To test this hypothesis, we investigated the potential therapeutic benefit of rigosertib alone and in combination with CDDP in P53 wild type and mutant models of UGCs. Methods: For this study, we evaluated the effect of rigosertib treatment alone and/or in combination with CDDP on AGS (P53 wild type) and FLO-1 (P53 mutant) UGC cell viability, survival, and expression of apoptotic markers. The MTT cell viability assay and Compusyn mediated median effect plot analysis (MEPA)(Chou and Talaly) were used to determine synergistic drug combinations of rigosertib and CDDP in AGS and FLO-1 UGC cells, respectively. Results: The cell viability data and MEPA indicated that rigosertib and CDDP show optimal synergistic anticancer activity in both AGS and FLO-1 UGC cells at a ratio of 1:10, respectively. The clonogenic cell survival assay data showed that in comparison to treatment with Rigosertib (AGS: 100nM; FLO-1: 50nM) or CDDP (AGS: 1000nM; FLO-1: 500nM) alone, the combination treatment at a ratio of 1:10 significantly increased (p Citation Format: Priya Pancholi, Tanmay Dichwalkar, Samhita Bapat, V. J. Rajadhyaksha, Benjamin S. Hoffman, Manoj Maniar, Vikas Sehdev. Rigosertib synergistically enhances the anticancer activity of Cisplatin in various preclinical models of upper gastrointestinal cancers. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4687.

ON 01210.Na (Ex-RAD) is a novel benzyl styryl sulfone analog, developed as a radioprotectant by Onconova Therapeutics Inc. The objectives of this research were to evaluate the hepatobiliary disposition of ON 01210.Na in the isolated perfused rat liver (IPRL) and to determine the effect of coadministration of ethacrynic acid (EA) on the pharmacokinetic profile of ON 01210.Na. EA acid was used as a prototypical inhibitor of glutathione-S-transferase inhibitor. ON 01210.Na was highly bound in IPRL perfusate proteins, and binding was significantly lower in the presence of EA. Dose-escalation studies (bolus dose, target concentrations 10-250 μg/mL) showed that ON 01210.Na followed nonlinear pharmacokinetics with hepatic clearance decreasing from 3.14 to 1.99 mL/min with increasing dose. ON 01210.Na underwent extensive metabolic degradation to its glutathione (GSH) adduct in liver. The GSH metabolite was mainly excreted into the bile. Coadministration of EA (1 mM) significantly inhibited the conversion of ON 01210.Na to its GSH conjugate, resulting in decreased clearance (approx. fivefold lower), and prolonged elimination from the perfusate. These preclinical studies suggest that EA is a potential pharmacoenhancer that can reduce the metabolism of ON 01210.Na in vivo, thereby increasing drug exposure and boosting radioprotective activity.

Prolonged reversible nerve blockade has broad applications in a number of clinical areas involving acute or chronic pain. The desired periods of reversible nerve blockade could vary from as little as one day to as long as one week. Implantation of a biodegradable controlled release local anesthetic device adjacent to nerves could potentially be a valuable dosage form. Therefore, controlled release devices based on polyanhydride polymers were prepared which would release the local anesthetic bupivacaine hydrochloride with varying rates. The parameters affecting the release of drug were studied in order to optimize the formulation. The studies were conducted with rectangular devices consisting of bupivacaine HCl dispersed homogeneously in the polymer at a loading of 10% w/w. Devices fabricated from three different copolymers, synthesized from fatty acid dimer and sebacic acid, were studied to determine the effect of comonomer on the release kinetics of the drug. Release studies were conducted at pH 7.4, 37°C, and the release profiles were analysed to determine the mechanism of release. The release of bupivacaine HCl could be best described by first order release kinetics from all the three copolymers and the release rate constant, k r , was directly proportional to the hydrophilicity of the polymer. The first order release rate constants were linearly proportional to both, the erosion rate and drug release rate ( r 2 = 0.999). Release profiles from all the three copolymers could also be described by an equation derived for a surface eroding cylindrical device. The erosion rate, B in cm/day, was obtained by fitting the release profile to the equation using a nonlinear regression method. The results showed that the drug release is controlled by erosion for the three copolymers, P(FAD-SA) 30:70, 20:80, and 10:90 and the release rates were 0.0004, 0.00066 and 0.0012 g/cm 2 /day, respectively. In addition, release profiles expressed as m t / m ∞ (fractional agent release profile) versus t / t ∞ fitted the theoretical equation for all the three copolymers. These results suggest that polyanhydrides undergo pure surface erosion at pH 7.4 and therefore the device geometry and erosion rate determine the release kinetics. Thus, knowing the erosion rate of the fatty acid dimer based polyanhydride, would help in achieving the appropriate drug release kinetics by manipulating the geometry of the device.

A new class of aliphatic copolyanhydrides was synthesized from nonlinear hydrophobic dimers (FAD) of erucic acid and sebacic acid which possessed the desired physico-chemical and mechanical properties for use as a carrier for drugs. The polymers were synthesized by melt condensation to yield film-forming polymers with molecular weights of 250,000. The copolymer composition was determined by 1H-NMR and gravimetric methods. In vitro degradation studies showed that these polymers degrade following a first-order kinetics with a rapid degradation in the first 10 days leaving a residue which is mostly the FAD comonomer. The drug release from the polymer also followed a first-order kinetics which correlates with the degradation process of the polymer. Drugs like carboplatin, methotrexate, tetracycline, and gentamicin were released in vitro for over 2 weeks and in some cases over 6 weeks. In vivo biocompatibility tests in rats and rabbits in the brain, muscle, and subcutaneously, demonstrated their toxicological inertness and biodegradability. The 1 : 1 copolymer of FAD : SA was selected as a carrier for various applications including a gentamicin-releasing implant which is now undergoing human clinical trials for the treatment of osteomyelitis. © 1993 John Wiley & Sons, Inc.

Bupivacaine, a local anesthetic is currently being formulated into a biodegradable drug delivery system for prolonged analgesic effect in conditions such as post surgical pain due to herniorrhaphy and thoracotomy. Preformulation studies were conducted to investigate the solubility and dissolution properties of the free base and the hydrochloride salt to select an appropriate drug form for formulation development. The pH solubility profiles showed that the solubility of the unionized form was about 0.15–0.25 mg/ml at pH 8–12, while solubility of the ionized form was 40–50 mg/ml between pH 1.8 to 6. Below pH 1.8, the solubility decreased due to the common ion effect. Overall the pH solubility profiles of the base and salt form were similar. pKa of 8.24 estimated from the pH solubility profile agree with the literature value of 8.17 determined potentiometrically. The intrinsic dissolution rates (IDR) of the base and the HCl salt were determined at 37°C using the Wood's methodology. The IDRs of the base and the HCl salt differed significantly at each pH value and there was no similarity in their pH-dependence despite very similar pH solubility profiles. To explain this anomalous behavior, the solubility of both forms was determined in the dissolution medium at 37°C, and the change in pH of the dissolution medium due to ionization and saturation was monitored. The solubility in the dissolution medium is the solubility in the diffusion layer pH ( C sh = 0). The IDRs of both forms correlated very well with the solubility in the dissolution medium and followed similar pH dependence as expected based on the Noyes-Whitney equation. However, the solubility in the dissolution medium was considerably different from the solubility value of the pH solubility profile at each pH value studied from pH 1 to pH 9 for both the base and the HCl salt form of drug. It was observed that when the dissolving species was undergoing a reaction during dissolution, ionization or unionization; i.e. base at pH 1–5 and salt at pH 5–9, the pH of the dissolution medium was altered and appeared to buffer between pH 4–7. This altered pH has been defined as the diffusion layer pH in the literature. It is the solubility of the dissolving species in the diffusion layer at pH h = 0, which determines the IDR, rather than the solubility in medium at bulk pH. Thus, pH-dependent behavior of IDR of the base and the HCl salt was explained on the basis of self-buffering action of the dissolving species in the diffusion layer. The IDR of base at pH 7.4 was very low and 1.2% of that at pH 1, thus base may not be suitable for the biodegradable device, from which predominant release mechanism is erosion. In contrast, the HCl salt had higher IDRs in the pH range of 1–7.4. The results also suggested that an alteration of the microclimate environment such as pH due to bioerosion of the device can have significant influence on the dissolution and hence the release properties of the drug delivery system. Therefore, these types of preformulation studies are necessary to select an appropriate form of drug to obtain the desired release properties from controlled release product.

ON 01210.Na (Ex-RAD®) is a novel small molecule under development by Onconova Therapeutics, Inc. as a radiation protection agent. The purpose of this investigation was to evaluate the effect of various formulation approaches on the systemic exposure of ON 01210.Na. In vitro experiments were used to characterize the plasma binding and metabolic stability of ON 01210.Na using hepatocytes from several animal species (mouse, rat, rabbit, dog, monkey and human). In vivo studies were performed in rats, rabbits, dogs and monkeys, and involved several routes of administration (intravenous, subcutaneous, oral). Plasma protein binding was high across species (>83%), and the rate of ON 01210.Na metabolism was highest in rat and mouse hepatocytes. After intravenous administration, ON 01210.Na demonstrated biphasic elimination from the plasma. Systemic exposure parameters (Cmax, AUC) were dose-proportional up to 100 mg/kg. Following subcutaneous dosing, ON 01210.Na showed relatively low bioavailability upon administration of the suspension formulation. Developing a solution formulation significantly increased the bioavailability of the drug. This solution formulation demonstrated significant oral bioavailability in rabbit (70%) and monkey (30%). The findings from these preclinical studies provide an overview of the systemic disposition of ON 01210.Na, aiding in the development of optimal formulations and routes of administration for pivotal animal efficacy and clinical safety studies. A solution formulation of ON 01210.Na for s.c. administration is being developed, in addition to an oral dosage form for potential use of the compound as a radioprotectant and a radiation-mitigating agent in wider military and civilian populations. Copyright © 2011 John Wiley & Sons, Ltd.

The biodegradable polymers used in controlled release applications are primarily insoluble polymers which undergo chemical or enzymatic hydrolysis to form soluble monomeric or oligomeric units. To determine the endurance of the polymer after implantation or injection into the body it is important to determine the rate of elimination of the intermediates formed upon the hydrolysis of the polymer. It is essential to identify these intermediates before its elimination rate can be determined. Identification of these intermediates is a problem because they are difficult to isolate, and are thermally and hydrolytically unstable. A new technique is proposed, taking advantage of the neighboring group effect on the hydrolysis of ionic and non-ionic oligomers, to determine the molecular weight of unknown species that are formed upon hydrolysis of the polymer. The technique involves the determination of the specific acid and base catalytic rate constants. To demonstrate the technique, a time sequence synthesis was carried out to synthesize several oligomers that would be forming upon the hydrolysis of poly(butylene tartrate). Hydrolysis studies were conducted with these oligomers and the samples were analyzed by liquid chromtography. The observed rate constant for the hydrolysis under acidic and alkaline pH medium were calculated from the terminal slopes of the first order plot. The observed rate constants were further utilized to calculate the specific acid and base catalytic rate constants. These specific rate constants, along with the micro-hydrogen and -hydroxyl ion catalytic rate constants, were used to determine the molecular weight of the intermediate species. The molecular weight obtained from the kinetic parameters was in excellent agreement with the results obtained from fast atom bombardment mass spectrometry. The same type of analysis can be extended to any multifunctional group compound which has repeat units and can undergo a specific reaction which can be accurately measured.

The present article was aimed to review the properties and applications of the actually available biodegradable polymers that have been used as targetable drug carriers and site-specific delivery systems. We have mainly focused on microparticulate or carrier-based drug delivery systems with little emphasis on implants as site-specific delivery systems. The review was divided into two major sections. The first section includes a brief description of the properties and applications of the existing biodegradable polymers for site-specific drug delivery classified in two main categories: synthetic biopolymers (as polyesters, polyanhydrides, polyorthoesters, polyphosphazenes, polycaprolactones), and natural biomaterials (as collagen, albumin and gelatin), which still remains an active area of research in spite of the extensive development of new biodegradable polymers. The second section discusses the mechanistic approaches for the selection of polymeric carriers. General guidelines for the ideal drug carrier complex were summarized. The importance of knowing and understanding the physicochemical properties of the polymer for the optimization of the final formulation and its eventual application were emphasized. The factors governing the effective drug concentration at the specific target site were reviewed. Some of the equations describing the release kinetics of a drug from a polymeric matrix were also examined. The last section of the review describes the preparation and use of polymeric macromolecular prodrugs. A diagrammatic representation of possible polymeric prodrug systems for use in site-specific delivery was described. The basic requirements from a polymeric prodrug system were also discussed. Finally, clinical applications of polymeric prodrugs as for cancer therapy and colonic delivery were considered.

Controlled polymeric release of chemotherapeutic agents has shown promise in the management of malignant gliomas. 4-Hydroperoxycyclophosphamide (4HC), loaded on the fatty acid dimer–sebacic acid copolymer (FAD:SA, 1:1), significantly prolonged survival in rats implanted with F98 and 9L gliomas. Here, we studied the in vitro and in vivo release kinetics in phosphate-buffered saline and rat brain of 20% 4HC/FAD:SA (wt:wt), the optimal dose for treatment of rat gliomas. In vitro release under infinite sink conditions was steady over the initial 12 hr to a peak of 20–35% of impregnated drug, consistent with early phase control via surface erosion. Release over the next 3 weeks was minimal, consistent with barrier formation around the polymer by an oily fatty acid dimer degradation product and consequent slowing of release. However, the polymer started to disintegrate by day 4, and there were minimal visible remnants by 3 weeks. Thus, a considerable amount of polymer-carried drug was probably lost in the disintegrating fragments. Also, drug loss is expected from its inherent hydrolytic instability. In vivo release into brain revealed two peak levels of drug at 0–1 hr and 5–20 days. With loaded polymer implanted intraperitoneally or cyclophosphamide injected systemically, peak brain drug levels were measured in 2–8 hr, with substantial decrease by 48 hr without a second peak. Brain levels were substantially higher than blood levels at all time periods. We conclude that FAD:SA (1:1) adequately protects the otherwise labile 4HC, allowing effective and substained drug release in vivo. Furthermore, it should be possible to modify the polymer to adjust the time of peak release for more beneficial therapeutic effects.

Purpose We conducted a first-in-man (to our knowledge) phase I study to determine the dose-limiting toxicities (DLTs), characterize the pharmacokinetic profile, and document any antitumor activity of ON 01910.Na, a new chemical entity that arrests cancer cells in G2/M by modulating mitotic regulatory pathways including polo-like kinase 1 (Plk1). Patients and Methods Patients had solid tumors refractory to standard therapy. ON 01910.Na was administered as a 2-hour infusion on days 1, 4, 8, 11, 15, and 18 in 28-day cycles. The starting dose was 80 mg, and an accelerated titration schedule (single-patient cohorts) was used for escalation. Pharmacokinetics were studied on days 1 and 15 of cycle 1. Results Twenty patients (11 women and nine men; age 46 to 73 years) were enrolled onto the study. Dose levels of 80, 160, 320, 480, 800, 1,280, 2,080, and 3,120 mg were evaluated in single-patient cohorts. A DLT and additional grade 2 toxicities made the 4,370-mg dose (n = 6) not tolerable, and the next lower dose cohort (3,120 mg) was expanded to six assessable patients. Toxicities were skeletal, abdominal, and tumor pain; nausea; urge to defecate; and fatigue. Hematologic toxicity was infrequent and mild. ON 01910.Na pharmacokinetics were characterized by a rapid distribution phase (distribution half-life, 1 hour) and a relatively slow elimination phase (elimination half-life, 27 hours). A refractory ovarian cancer patient had an objective response after four cycles and remained progression free for 24 months. Conclusion ON 01910.Na showed a distinct but moderate toxicity pattern. The recommended phase II dose of ON 01910.Na with this schedule of administration is 3,120 mg. Single-agent activity was documented in an ovarian cancer patient.

The objective of the present study was to investigate the properties of branched polyanhydrides and compare them to the corresponding linear polymers. Sebacic acid was polymerized with 1,3,5 benzenetricarboxylic acid and poly(acrylic acid) to yield random and graft-type branched polyanhydrides. The polymerization was followed until the gel point and the resulting polymers were evaluated for their physico-chemical properties and degradation behaviour. Drug release from these polymers was studied using morphine as a model drug. The experiment showed that the molecular weights of branched polyanhydride were significantly higher (mol wt 250 000) than the molecular weight of linear poly(sebacic anydride) (mol wt 80 000). In the case of poly(acrylic acid) branched polymers, the molecular weight increased linearly with increasing concentration of poly(acrylic acid). The specific viscosities of the branched polyanhydrides were lower than linear polyanhydrides with similar molecular weights. Except for the difference in molecular weights, there were no noticeable changes in the physico-chemical or thermal properties of the branched polymers and the linear poly(sebacic anhydride). The degradation of the branched polyanhydride was triphasic and the degradation rates were faster than for linear poly(sebacic anhydride). The release of morphine from the branched polymers was lower than the corresponding poly(sebacic anydride). Release of morphine was much higher from the poly(acrylic acid) branched polymers compared to the 1,3,5 benzenetricarboxylic acid branched polymers and increased with increasing concentrations of the branching agent. However, in both cases the release rates and the total amounts of morphine released approached that of poly(sebacic anhydride).

Introduction: Recent proof-of-concept for targeting cyclin dependent kinases 4 and 6 (CDK4/6) culminated in the approval for breast cancer of the first-in-class CDK4/6 inhibitor, palbociclib (Ibrance®). Palbociclib and other potent but narrowly targeted CDK4/6 inhibitors are cytostatic rather than cytotoxic (Leonard et al, 2012), and require combination therapy for optimal activity. ON 123300 is a next-generation CDK4/6 inhibitor with improved single-agent cytotoxicity. This novel compound is a potent CDK4 and CDK6 inhibitor (IC50 = 3.9 nM and 9.8 nM, respectively) that is cytotoxic against breast and other cancer cell lines (Reddy et al, 2014). We present pre-IND profiling pharmacology, physicochemical and ADME studies to support ON 123300 as a clinical candidate and next-generation CDK4/6 inhibitor. Methods and Results: Non-clinical studies were conducted in order to assess the drug-like properties of ON 123300 and its pharmaceutical salts. Physicochemical parameters were determined for the compound. ON 123300 was highly soluble below pH 4.0, with reduced solubility in more basic conditions. Predicted intestinal absorption, as measured by Caco-2 permeability, was 1.95×10-5 cm/s with a low efflux ratio. Based on these characteristics, the compound was advanced to lead profiling against 68 primary molecular targets. Radioligand binding studies revealed limited receptor inhibition (11/68 targets) with 10 μM of ON 123300. Human Ether-a-go-go (hERG) inhibition testing revealed no significant effect (IC50 > 25 μM). In vitro metabolism studies indicated metabolism through CYP3A4 and CYP2C8. Finally, in silico based modeling (Cloe® PK) integrating all key non-clinical parameters was carried out in order to estimate the potential for oral absorption in humans. Preliminary analysis suggests good oral bioavailability and the potential to establish an acceptable therapeutic window. Conclusions: The well differentiated biochemical, anticancer and pharmaceutical properties of ON 123300 provide the basis for pre-clinical toxicology testing, leading to an investigational new drug (IND) filing and clinical exploration of this compound across tumor types that share targets accessed by this next-generation CDK inhibitor. Citation Format: Benjamin Hoffman, Ramana Reddy, Muralidhar Mallireddigari, Daniel Fox, Chen Ren, Manoj Maniar. Single-agent activity and favorable pharmaceutical properties of orally bioavailable next-generation CDK4/6 inhibitor, ON 123300. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2015 Nov 5-9; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2015;14(12 Suppl 2):Abstract nr LB-A21.

Introduction: Eukaryotic translation initiation factor 4E (eIF4E) is a master regulator that controls translation of mRNA in mammalian cells. eIF4E is a proto-oncogene that promotes translation of several genes essential for cellular proliferation (cyclin D1, c-Myc, mTOR), survival (Akt, survivin), angiogenesis (VEGF), and metastasis (MMP9). Overexpression of eIF4E has been observed in almost all major groups of cancers and has been shown to induce increased expression of cyclin D1 and c-Myc. Briciclib is a small molecule, water soluble derivative of ON 013100 that binds to eIF4E. An intravenous formulation of briciclib is currently being investigated in a Phase 1 clinical trial. Recent advancements in formulation technology have made feasible a stable, orally bioavailable version of ON 013100, which may allow for more convenient administration. In this study we investigated and compared the anticancer activity of briciclib to ON 013100. We determined the susceptibility of various breast, mantle cell leukemia (MCL), gastric, and esophageal cancer cell lines to treatment with briciclib or ON 013100. In addition, we investigated the effect of briciclib and ON 013100 on expression of markers associated with eIF4E activity (cyclin D1 and c-Myc) and apoptosis (P53 and Cleaved Caspase 3). Methods: MTT cell viability assays, Western blot analysis, and ELISA assays were used to evaluate cellular viability, survival, and protein expression levels. Results: Briciclib and ON 013100 inhibited the proliferation of MCL (JEKO-1 and MINO), breast (MCF7 and MDA-MB-231), gastric (AGS), and esophageal (OE19, OE33, and FLO-1) cancer cell lines at nanomolar concentrations (Briciclib: GI50 = 9.8 - 12.2 nM; ON 013100 GI50 = 6.7 - 11.2 nM). By comparison, briciclib and ON 013100 were relatively non-toxic to normal endothelial cells. Western blot analysis indicated that treatment with briciclib or ON 013100 significantly reduced the expression of cyclin D1 and c-Myc in breast and MCL cancer cell lines within 8 hours and in a dose-dependent manner. These observations were supported by ELISA analysis of cyclin D1 and c-Myc protein levels. Furthermore, treatment with these agents enhanced the expression of P53 and Cleaved Caspase 3 pro-apoptotic proteins in breast and MCL cancer cell lines. Our ongoing tumor xenograft experiments are in agreement with the aforementioned in vitro observations. Conclusions: Our findings suggest that both an orally bioavailable ON 013100, and its water soluble derivative, briciclib, have the same novel mechanism of action involving translation. Our in vitro and in vivo data demonstrate the potential of briciclib in targeting eIF4E for hematopoietic and solid cancers and the possibility for developing an oral version of this promising clinical agent. Citation Format: Neel Jasani, Bina Desai, Justine M. Betzu, Tanmay Dichwalkar, Samhita Bapat, V. J. Rajadhayksha, Benjamin S. Hoffman, Manoj Maniar, Vikas Sehdev. Potent anticancer activity of an orally bioavailable small molecule, ON 013100, and its water soluble derivative, briciclib, a clinical-stage eIF4E-targeted agent. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 1649. doi:10.1158/1538-7445.AM2015-1649