Sarath Kanekal

In vivo and in vitro cytotoxicity of R-etodolac with dexamethasone in glucocorticoid-resistant multiple myeloma cells

Glucocorticoids have been widely used in the treatment of multiple myeloma (MM) both as single agents and in combination with other drugs. However, primary or acquired glucocorticoid resistance occurs in most cases. It was recently reported that R‐etodolac induced in vitro cytotoxicity in MM cell lines and in primary MM cells, as well as synergistically enhanced dexamethasone (Dex)‐induced apoptosis in Dex‐sensitive MM.1S cells. This study examined the in vitro and in vivo effects of combination treatment with R‐etodolac and Dex on Dex‐resistant OPM1 cells. Treatment with R‐etodolac and Dex was found to enhance cytotoxicity, inhibit nuclear factor κB activity via upregulation of IκBα, as well as enhance Dex‐induced caspase activation and poly (ADP)‐ribose polymerase cleavage in OPM1 cells. R‐etodolac also enhanced Dex cytotoxicity in patient MM cells that were resistant to glucocorticoids. The in vivo anti‐tumour effect of this combination on MM cells was evaluated by using severe combined immunodeficient mice engrafted with OPM1. Treatment with R‐etodolac or Dex alone did not induce a significant reduction of tumour volume; in contrast, combination treatment with R‐etodolac and Dex induced significant synergistic inhibition of tumour growth. These data indicate that R‐etodolac overcomes resistance to Dex in glucocorticoid‐resistant MM cells, providing the framework for clinical trials of R‐etodolac combined with Dex, to improve patient outcome in MM.

S110, a novel decitabine dinucleotide, increases fetal hemoglobin levels in baboons (P. anubis)

BackgroundS110 is a novel dinucleoside analog that could have advantages over existing DNA methyltransferase (DNMT) inhibitors such as decitabine. A potential therapeutic role for S110 is to increase fetal hemoglobin (HbF) levels to treat β-hemoglobinopathies. In these experiments the effect of S110 on HbF levels in baboons and its ability to reduce DNA methylation of the γ-globin gene promoter in vivo were evaluated.MethodsThe effect of S110 on HbF and γ-globin promoter DNA methylation was examined in cultured human erythroid progenitors and in vivo in the baboon pre-clinical model. S110 pharmacokinetics was also examined in the baboon model.ResultsS110 increased HbF and reduced DNA methylation of the γ-globin promoter in human erythroid progenitors and in baboons when administered subcutaneously. Pharmacokinetic analysis was consistent with rapid conversion of S110 into the deoxycytosine analog decitabine that binds and depletes DNA.ConclusionS110 is rapidly converted into decitabine, hypomethylates DNA, and induces HbF in cultured human erythroid progenitors and the baboon pre-clinical model.

Circadian pharmacology of l-alanosine (SDX-102) in mice

l-Alanosine (SDX-102) exerts its cytotoxicity through inhibition of de novo purine biosynthesis, an effect potentiated by methylthioadenosine phosphorylase (MTAP) deficiency. The relevance of circadian dosing time was investigated for chronotherapeutic optimization of SDX-102. Toxicity was assessed in healthy mice following single (1,150, 1,650, or 1,850 mg/kg/d) or multiple doses (250 or 270 mg/kg/d). Efficacy was tested in mice with P388 leukemia receiving multiple doses (225 or 250 mg/kg/d). SDX-102 was administered at six circadian times 4 hours apart in mice synchronized with 12 hours of light alternating with 12 hours of darkness. MTAP expression was determined in liver, bone marrow, small intestinal mucosa, and P388 cells. Dosing at 19 hours after light onset reduced lethality 5-fold after single administration and 3-fold after multiple doses as compared with worst time [P < 0.001 and P < 0.01, respectively (χ2 test)]. Neutropenia, lymphopenia, and bone marrow hemorrhagic lesions were significantly less in mice dosed at 19 hours after light onset as compared with 7 hours after light onset. SDX-102 at 7 hours after light onset transiently ablated the 24-hour patterns in body temperature and activity. A circadian rhythm characterized small intestinal MTAP expression with a maximum at 6:30 hours after light onset (P = 0.04). A minor survival improvement was found in MTAP-deficient P388 mice receiving SDX-102 at 7 or 23 hours after light onset as compared with other times (P = 0.03, log-rank test). In conclusion, the therapeutic index of SDX-102 was improved by the delivery of SDX-102 in the mid to late activity span. These results support the concept of chronomodulated infusion of SDX-102 in cancer patients. [Mol Cancer Ther 2006;5(2):337–46]

Abstract 2562: Dianhydrogalactitol inhibits the growth of glioma stem and non-stem cultures, including temozolomide-resistant cell lines, in vitro and in vivo

2562 The standard of care for glioblastoma multiforme (GBM) patients is surgical resection followed by temozolomide (TMZ) and radiation (XRT). However, TMZ-resistance has emerged as a significant unmet medical need, as DNA repair enzyme 0-6-methylguanine DNA methyltransferase (MGMT) removes the methyl-group adducts caused by TMZ. Dianhydrogalactitol (VAL-083) is a structurally unique alkylating agent causing DNA crosslinks at N7 position of guanine. Because VAL-083’s N7 adducts are not subject to MGMT mediated repair, it may be an effective chemotherapeutic in the treatment of TMZresistant GBM. VAL-083 crosses the blood brain barrier and accumulates in brain tumor tissue. We have recently shown that TMZ activity is similar in cancer stem cells (CSC) and their paired non-CSC from primary GBM tissues, and that the activity is MGMT-dependent1. We thus sought to investigate how our CSC and non-CSC panel would respond to VAL-083 alone or in combination with XRT. We further investigated the activity of VAL-083 in in vivo models of drug-resistant GBM in comparison to TMZ. Rag2 mice bearing intracranial human GBM xenograft tumors of either MGMT-positive and TMZresistant origin (BT74), or MGMT-negative and TMZ-sensitive origin (U251) were treated. VAL-083 was given i.p. 3 times/week x 3 weeks, and the efficacy of VAL-083 in controlling tumor growth compared to TMZ (30 mg/kg). Disease progression was evaluated by overall survival, clinical observations and body weight measurements. Our in vitro results show that VAL-083 is a potent inhibitor of all tested primary GBM cultures, irrespective of MGMT status. VAL-083 causes cell cycle arrest and loss of cell viability in TMZ-resistant cells, and at lower concentrations than TMZ in TMZ-sensitive cells. Furthermore, VAL-083 is not affected by cell culture condition (Stem vs. Non-Stem). Low dose VAL-083 combined with XRT exhibited an additive effect in all cultures tested, suggesting that VAL-083 might act as a radiosensitizer. In the in vivo U251 model, the median survival time for mice treated with 4 mg/kg VAL-083 was significantly increased to 72 days compared to 48 days for controls (p<0.0001). Median survival time for 3 mg/kg VAL-083 was 54 days. Body weight loss was observed in mice treated with 5 mg/kg and treatment was stopped after 4 doses after which the animals recovered and their median survival was 57 days. Animals treated with TMZ were terminated at day 102 at the end of the study. BT74: study is ongoing, data will be presented at the meeting.In conclusion, VAL-083 is highly efficacious against both stem and non-stem GBM cell cultures in vitro, the activity is independent of MGMT and VAL-083 appears to act as a radiosensitizer in GBM. In vivo xenograft GBM models further validate the benefits of VAL-083 in the treatment of GBM and support ongoing clinical research with VAL-083, which is currently in a clinical trial for GBM patients with recurrent disease. VAL-083 functions as a radiosensitizer with potential superiority to temozolomide VAL-083 causes cell cycle arrest in TMZ-resistant cultures, including CSCs

Abstract 824: In vivo efficacy of VAL-083 in the treatment of non-small cell lung cancer

Proceedings: AACR Annual Meeting 2014; April 5-9, 2014; San Diego, CA The median overall survival time for patients with stage IV non-small cell lung cancer (NSCLC) is 4 months, and 1- and 5-year survival is less than 16% and 2%, respectively. NSCLC is usually treated with surgery followed by treatment with either Tyrosine Kinase Inhibitors (TKIs) (e.g. erlotonib, gefitinib) or platinum-based regimens (e.g. cisplatin). TKIs have resulted in vastly improved outcomes for patients with EGFR mutations; however, TKI resistance has emerged as a significant unmet medical need, and long-term prognosis with platinum-based therapies is poor. Additionally, the incidence of brain metastases is high in patients with NSCLC with a poor prognosis. VAL-083 is a structurally unique bi-functional alkylating agent mediating interstrand DNA crosslinks at targeting N7 of guanine, thus differing in mechanism of action from TKIs and cisplatin. VAL-083 further crosses the blood-brain barrier and accumulates in tumor tissue. VAL-083 has demonstrated activity against NSCLC in preclinical and clinical trials, both as a single agent and in combination with other treatment regimens, suggesting VAL-083 may be a therapeutic option for drug-resistant NSCLC and NSCLC patients with brain metastasis. VAL-083 is approved for treatment of lung cancer in China and has documented activity against NSCLC in historical NCI-sponsored clinical trials; however, specific questions regarding the efficacy of VAL-083 in comparison to cisplatin and in TKI-resistant NSCLC have to our knowledge not been addressed before. The purpose of this study is to evaluate the activity of VAL-083 in in vivo models of drug-resistant NSCLC in comparison to other drugs, including cisplatin. Rag2 mice bearing subcutaneous human lung adenocarcinoma xenograft tumors of either TKI-resistant (H1975) or TKI-sensitive (A549) origin were treated. The results will provide direction to clinical research aimed at influencing practice patterns under VAL-083s current label and support expanded global development. Two human NSCLC cell lines, A549 (TKI-sensitive) and H1975 (TKI-resistant), were used for xenograft tumor models in female Rag2 mice. VAL-083 was given i.p. 3 times/week for 3 weeks, and the in vivo efficacy of VAL-083 in controlling tumor growth compared to cisplatin. Saline was used as control treatment. Disease progression is evaluated by tumor volume, clinical observations and body weight measurements. Blood samples are analyzed for CBC/differential analyses to assess myelosuppression or other changes in blood chemistry. On study day 51, the mean tumor volume of the A549 tumor bearing control mice (saline solution) was 338 mm3, while the mean tumor volume of the cisplatin-treated (5 mg/kg) and the VAL-083-treated (6 mg/kg) mice was 260 mm3 and 156 mm3, respectively (study ongoing). Further results will be reported at AACR in April 2014. Citation Format: Anne Steino, Jeffrey Bacha, William J. Garner, Sarath Kanekal, Dawn Waterhouse, Nancy Dos Santos, Dennis M. Brown. In vivo efficacy of VAL-083 in the treatment of non-small cell lung cancer. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 824. doi:10.1158/1538-7445.AM2014-824

Abstract B252: The unique mechanism of action of VAL-083 may provide a new treatment option for some chemo-resistant cancers.

Poor outcomes in cancer therapy due to chemo-resistance remain a significant unmet clinical problem for many solid tumors and leukemias. VAL-083 (dianhydrogalactitol) represents a structurally unique first-in-class N7-bifunctional DNA alkylating agent. VAL-083 primarily mediates guanine N7 DNA cross-links, which separates it from other DNA alkylating chemotherapeutics (e.g. temozolomide) that have their primary cytotoxicity by targeting DNA at the O6 position of guanine. As expected from its mechanism, VAL-083 overcomes resistance associated with O6-methylguanine-DNA methyltransferase (MGMT) overexpression in vitro. Furthermore, unlike other N7-acting drugs, such as cisplatin which primarily induces intrastrand crosslinks, VAL-083 mediates interstrand DNA crosslinks. When tested side-by-side in a standard syngeneic mouse fibrosarcoma model (RIF-1 cell-line in C3H mice), VAL-083 demonstrated superiority to cisplatin in tumor growth delay. For mice treated with a single injection of cisplatin of 4 mg/kg, the tumor growth delay was 1.45 days compared to untreated controls. Single IP injection of VAL-083 at a dose of 10 mg/kg delayed tumor growth by 5.6 days. Combination treatment of VAL-083 followed immediately by cisplatin produced a more than additive effect by delaying growth 8.65 days. VAL-083 readily crosses the blood-brain barrier, accumulates in brain tissue and is effective against brain tumor cells both in vitro and in vivo, and against brain cancer stem cells in vitro. VAL-083 is currently in Phase I/II clinical trials for glioblastoma and recurrent metastatic brain tumors. Studies are underway to further characterize the efficacy of VAL-083 in various tumor cell-lines resistant to chemotherapy. Previous clinical studies showing VAL-083 activity in several tumor models, combined with the new data on MGMT-chemo-resistance and synergy with cisplatin makes VAL-083 a promising alternative for both primary and secondary brain tumors as well as cisplatin-resistant tumors. Citation Information: Mol Cancer Ther 2013;12(11 Suppl):B252. Citation Format: Anne Steino, Jeffrey A. Bacha, William J. Garner, Sarath Kanekal, Zahid H. Siddik, Dennis M. Brown. The unique mechanism of action of VAL-083 may provide a new treatment option for some chemo-resistant cancers. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2013 Oct 19-23; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(11 Suppl):Abstract nr B252.

Abstract CT054: Phase II study of dianhydrogalactitol in patients withMGMT-unmethylated bevacizumab-naive recurrent glioblastoma

Glioblastoma (GBM) is the most common and aggressive primary brain cancer. Current standard of care includes surgery, radiation and treatment with temozolomide (TMZ), however nearly all tumors recur and the prognosis for recurrent GBM is dismal. Most GBM tumors have unmethylated promoter status for O6-methylguanine-DNA-methyltransferase (MGMT); a validated biomarker for TMZ-resistance. Second-line treatment with anti-angiogenic agent bevacizumab has not improved overall survival (OS) and 5-year survival is less than 3%. Dianhydrogalactitol (VAL-083) is a bi-functional alkylating agent targeting N7-Guanine and inducing interstrand cross-links, DNA double-strand breaks and cell-death in GBM cell-lines and GBM cancer stem cells. VAL-083’s cytotoxicity is independent of MGMT status and VAL-083 overcomes TMZ-resistance in vitro. Our recent phase I/II clinical trial in recurrent GBM patients failing both TMZ and bevacizumab, suggested VAL-083 offers clinically meaningful survival benefits for patients with recurrent GBM and pinpointing a new dosing regimen (40 mg/m2/d on days 1,2,3 of a 21-day cycle). A pivotal Phase 3 study in recurrent GBM after failing both TMZ and bevacizumab is being planned. If successful, this study will serve as the basis for a New Drug Application (NDA) submission for VAL-083. In addition, a single-arm Phase 2 study to confirm the tolerability of the new dosing regimen in combination with radiotherapy and to explore the activity of VAL-083 in newly diagnosed MGMT-unmethylated GBM patients whose tumors are known to express high MGMT levels is proceeding. In the present Phase 2 clinical trial, the main goal is to assess the overall survival (OS) in MGMT-unmethylated, recurrent, bevacizumab-naive GBM. RATIONALE: The vast majority of GBM patients experience recurrent/progressive disease within a year from initial diagnosis and median survival after recurrence is 3-9 months. Chemotherapy regimens for these patients are lacking and there is a significant unmet medical need. Given VAL-083’s novel alkylating mechanism, promising clinical benefit, and favorable safety profile, a trial studying VAL-083 in MGMT-unmethylated recurrent GBM is warranted. METHOD: Open label, single-arm, biomarker-driven Phase 2 clinical trial in MGMT-unmethylated adult GBM patients at first recurrence/progression, prior to bevacizumab. 48 patients will be enrolled to determine if treatment with VAL-083 will improve OS at 9-months compared to historical control with lomustine. The patients will receive VAL-083 40mg/m2/day on days 1,2,3 of a 21-day cycle. Patients will be followed until death or for at least 9 months from enrollment, whichever occurs earlier. Survival will be compared to recently published EORTC26101 for recurrent MGMT-unmethylated GBM patients treated with lomustine. Secondary outcome measures include progression-free survival and overall response rate. Clinicaltrials.gov identifier: NCT02717962. Citation Format: Barbara J. O9Brien, Jeffrey A. Bacha, Dennis M. Brown, Anne Steino, Richard Schwartz, Sarath Kanekal, Lorena Lopez, Marta Penas-Prado. Phase II study of dianhydrogalactitol in patients with MGMT-unmethylated bevacizumab-naive recurrent glioblastoma [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 CT054. doi:10.1158/1538-7445.AM2017-CT054

Abstract A01: A comparison of the mechanisms and cytotoxic activity of dianhydrogalactitol (VAL-083) to cisplatin in ovarian tumor models harboring wild-type and mutant p53.

Ovarian cancers are usually treated with platinum-based therapies, which produce a 70% response rate. However, many patients relapse as tumors become resistant to cisplatin and carboplatin, resulting in a 5-year survival rate of about 20%. Onset of drug resistance is a major factor limiting the clinical utility of platinum-based therapeutic regimens drugs and, therefore, new agents are needed to circumvent resistance. Dianhydrogalactitol (VAL-083) is a bi-functional alkylating agent, whose cytotoxic activity is due to the formation of DNA cross links at the N7 position of guanine. Unlike cisplatin and carboplatin, which predominantly form intrastrand DNA cross-links, VAL-083 derives its anti-cancer activity interstrand DNA cross-links. More importantly, VAL-083 has demonstrated clinical activity against a range of tumor types, including ovarian cancer in historical NCI-sponsored clinical studies. Platinum drug resistance is normally ascribed to several mechanisms, with mutation in wild-type p53 playing a critical role, particularly in high-grade ovarian serous carcinoma (HGOSC), where the incidence of this mutation can be substantial. However, recent analysis of the TCGA database indicates that the survival rate in wild-type p53 HGOSC is no better or perhaps even worse. Using a 5-day MTT assay and fitting a sigmoidal curve to the dose-response data to determine IC 50 values, we have similarly found that resistance to cisplatin in a panel of ovarian tumor models is greater when p53 is wild-type (median IC 50 : 4-7 µM vs. 1-2 µM for mutant/null p53 models; in comparison, sensitive wild-type p53 A2780 cells have an IC 50 of 0.2-0.3 μM). Previous studies in our lab suggest that factors downstream from p53, including MDM4 and p21, may contribute to cisplatin-resistance in ovarian cancer models with high cisplatin-resistance and wild-type 53, like 2780CP-16. We thus sought to investigate the potential of VAL-083 to circumvent cisplatin-resistance in five p53 wild-type ovarian cancer models: one cisplatin-sensitive A2780, and four cisplatin-resistant 2780CP-16, OVCAR-10, Hey and OVCA-433. IC 50 values of VAL-083 were generated using the MTT assay and sigmoidal curve fitting of data, as described above. The baseline IC 50 for VAL-083 against A2780 cell was about 0.5 μM. The IC 50 for VAL-083 in the cisplatin-resistant cell-lines 2780CP-16, OVCAR-10, Hey and OVCA-433 were 4- to 7-fold greater; however, VAL-083 was substantially more potent in comparison to cisplatin in these models where corresponding IC 50 values were 10- to over 25-fold greater. These results demonstrate that there is only partial cross-resistance between cisplatin and VAL-083 further suggesting distinct modes of action for the two drugs. In order to examine whether the partial circumvention of cisplatin-resistance was p53-dependent, cytotoxicity was determined in isogenic HCT-116 p53-/- and HCT-116 p53+/+ models. These studies demonstrated that loss of p53 increased resistance to cisplatin by 2-5-fold whereas loss of p53 only increased resistance to VAL-083 about 1.7-fold. These results suggest that VAL-083 is less dependent on p53 for its cytotoxic activity. Immunoblots confirmed this in 2780CP-16 cells, where VAL-083 was more effective than cisplatin at increasing p53 and p21 levels, and induced relatively greater Ser-15 and Ser-20 phosphorylations, further supporting different modes of action for the two drugs. In contrast, both drugs were equally effective in inducing these markers of DNA damage in A2780 cells. The non-overlapping mechanisms of action suggested a potential therapeutic benefit for combinations of VAL-083 with cisplatin. We have previously reported that the combination of VAL-083 with cisplatin in wild-type p53 NSCLC models H460 and A549, and mutant p53 NSCLC H1975 demonstrated significant super-additivity (p Citation Format: Jeffrey A. Bacha, Michelle Martinez-Rivera, Guanghan He, Xiaolei Xie, Anne Steino, Sarath Kanekal, Dennis M. Brown, Zahid H. Siddik. A comparison of the mechanisms and cytotoxic activity of dianhydrogalactitol (VAL-083) to cisplatin in ovarian tumor models harboring wild-type and mutant p53. [abstract]. In: Proceedings of the AACR Special Conference on Advances in Ovarian Cancer Research: Exploiting Vulnerabilities; Oct 17-20, 2015; Orlando, FL. Philadelphia (PA): AACR; Clin Cancer Res 2016;22(2 Suppl):Abstract nr A01.

Abstract CT074: Phase I/II study of VAL-083 in patients with recurrent glioblastoma

Glioblastoma (GBM) is the most common brain cancer. Front-line systemic therapy with temozolomide (TMZ) is often ineffective due to O6-methylguanine-DNA-methyltransferase (MGMT)-mediated resistance and patients with recurrent glioma have limited treatment options and very poor prognosis. Dianhydrogalactitol (VAL-083) is a bi-functional alkylating agent that readily crosses the blood-brain barrier and has demonstrated activity against GBM in prior NCI-sponsored clinical trials. VAL-083 induces cross-links at N7 of guanine causing double-strand DNA breaks and apoptosis independent of MGMT expression against multiple GBM cell lines and cancer stem cells in vitro. VAL-083 cytotoxic activity also appears to be less dependent on wild type p53 compared to other alkylating agents. The main goal of this clinical trial was to determine an appropriate dose for VAL-083 for advancement to Phase II/III trials as a potential new treatment for refractory GBM. METHOD: Open-label, single-arm Phase I dose-escalation study (3+3 design) of IV treatment with VAL-083 on days 1, 2, 3 of a 21-day cycle, until MTD was reached. In Phase II, additional patients with GBM are treated at the MTD to gather further safety and outcomes data. Patients must have histologically confirmed GBM, previously treated with surgery and radiation and must have failed both TMZ and bevacizumab, unless contraindicated. RESULTS: Phase I has been completed and 40 mg/m2/d confirmed as the MTD. 29 GBM patients were enrolled in Phase I across 9 dose cohorts (1.5 - 50 mg/m2/d). Myelosuppression was mild; no drug-related serious adverse events were reported at doses ?40 mg/m2/d. Dose limiting toxicities (DLT), consisting of thrombocytopenia, were observed at 50 mg/m2/d and at an interim 45 mg/m2/d cohort. Platelet nadir occurred around day 20 and resolved rapidly and spontaneously. Pharmacokinetic analyses show dose-dependent linear systemic exposure with a short 1-2h plasma terminal half-life; average Cmax 781 ng/mL (5.3μM) at 40 mg/m2/d resulting in estimated CNS concentrations within the IC50 range observed for GBM cell-lines in vitro. A 14 patient Phase II expansion cohort was enrolled at 40 mg/m2/d. Safety observations in the Phase II expansion cohort to date are consistent with Phase I: Observed myelosuppression is mild, with the exception of 1 patient previously treated with CCNU who developed grade 4 thrombocytopenia. To date, 20 GBM patients (6 patients in Phase I and 14 patients in Phase II) have been treated with VAL-083 at therapeutic doses of 30 or 40 mg/m2/d. CONCLUSIONS: VAL-083 at 40 mg/m2/d on days 1, 2, 3 of a 21-day cycle exhibits a favorable safety profile and the Phase I part of the study showed a trend toward clinically meaningful improved survival in refractory GBM patients. Updated safety and outcomes data from the Phase II expansion cohort will be presented. ClinicalTrials.gov Identifier NCT01478178. Citation Format: Kent C. Shih, Manish R. Patel, Nicholas Butowski, Gerald S. Falchook, Sani H. Kizilbash, Jeffrey A. Bacha, Dennis M. Brown, Anne Steino, Richard Schwartz, Sarath Kanekal, Lorena M. Lopez, Howard A. Burris. Phase I/II study of VAL-083 in patients with recurrent glioblastoma. [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 CT074.

Abstract A51: Dianhydrogalactitol (VAL-083) offers potential therapeutic alternatives in the treatment of pediatric brain tumors

Background: Medulloblastoma (MB) is the most common malignant pediatric brain tumor, accounting for 15-30% of all childhood intracranial neoplasms. High grade gliomas (HGG) are much rarer in children than in adults, comprising only 5%-10% of childhood brain tumors. Although multidisciplinary treatment has improved the 5-year survival rates in children significantly, the prognosis for recurrent MB and HGG remains poor with median overall survival 6 -methylguanine-DNA methyltransferase (MGMT), which is correlated with TMZ resistance, have been reported. Dianhydrogalactitol (VAL-083) is a structurally unique bi-functional alkylating agent causing DNA crosslinks at N 7 position of guanine. VAL-083 readily crosses the blood brain barrier and has been shown to accumulate in brain tumor tissue. Furthermore, VAL-083 demonstrated clinical activity against MB and HGG in historical NCI-sponsored clinical studies. We have recently shown that VAL-083 demonstrates cytotoxic activity in GBM independent of MGMT expression in vitro and in vivo . We have further shown that VAL-083 is highly effective against GBM cancer stem cells (CSC) and non-CSC and that it acts as a radiosensitizer in GBM cell lines, in vitro . VAL-083 is currently in phase II clinical trials for recurrent GBM in adults. In the current adult GBM clinical trial VAL-083 displayed a favorable safety-profile and preliminary analysis supports a survival benefit at doses chosen for further investigation. Based on these recent results and data supporting VAL-0839s clinical activity in historical MB and HGG studies, we sought to investigate the cytotoxic activity of VAL-083 as a potential therapeutic alternative for pediatric brain tumors by studying the drug against MB and pediatric HGG cell lines in vitro . Methods: Human MB cell lines DAOY, UW228, ONS-76 and UW426 and pediatric HGG cell line SF188 were treated with VAL-083 at concentrations of 0.1 100 μM for 72 h. Growth inhibition was measured by high content screening analysis. Neurosphere formation of DAOY and SF188 cells was determined by neurosphere colony assay. Results: VAL-083 inhibited growth of all cell lines (DAOY, UW228, ONS-76 UW426 and SF188) with IC 50 at low micro-molar concentrations. DAOY, UW228 and SF188 cells were most sensitive to VAL-083. Primary neurosphere formation of DAOY cells was completely inhibited at 5 μM VAL-083 and VAL-083 was superior to TMZ against primary neurospheres formation of SF-188 cells; complete inhibition of SF-188 neurospheres was observed with the combination of VAL-083 and TMZ. Conclusion: These results suggest that VAL-083 is active against MB and pediatric HGG cells as well as CSC in vitro . Taken together with the results of historical NCI-sponsored clinical trials, these data warrant further investigations of VAL-083 as a possible therapeutic alternative for the treatment of recurrent pediatric MB and HGG. Citation Format: Jeffrey A. Bacha, Abbas Fotovati, Kaiji Hu, Anne Steino, Sarath Kanekal, Dennis M. Brown. Dianhydrogalactitol (VAL-083) offers potential therapeutic alternatives in the treatment of pediatric brain tumors. [abstract]. In: Proceedings of the AACR Special Conference on Advances in Pediatric Cancer Research: From Mechanisms and Models to Treatment and Survivorship; 2015 Nov 9-12; Fort Lauderdale, FL. Philadelphia (PA): AACR; Cancer Res 2016;76(5 Suppl):Abstract nr A51.