BackgroundUltradian rhythms, rhythms with a period of less than 24 hours, are a widespread and fundamental aspect of life. The mechanisms underlying the control of such rhythms remain only partially understood. Defecation in C. elegans is a very tightly controlled rhythmic process. Underlying the defecation motor programme is an oscillator which functions in the intestinal cells of the animal. This mechanism includes periodic calcium release and subsequent intercellular calcium waves which in turn regulate the muscle contractions that make up the defecation motor programme. Here we investigate the role of TRPM cation channels in this process.ResultsWe use RNA interference (RNAi) to perturb TRPM channel gene expression. We show that combined knock down of two of the TRPM encoding genes, gon-2 and gtl-1, results in an increase in the variability of the cycle but no change in the mean, in normal culture conditions. By altering the mean using environmental (temperature) and genetic approaches we show that this increase in variability is separable from changes in the mean. We show that gon-2 and gtl-1 interact with components of the calcium signalling machinery (itr-1 the C. elegans inositol 1,4,5-trisphosphate receptor) and with plasma membrane ion channels (flr-1 and kqt-3) which are known to regulate the defecation oscillator. Interactions with these genes result in changes to the mean period and variability. We also show that knocking down a putative transcription factor can suppress the increased variability caused by reduction of gon-2 and gtl-1 function. We also identify a previously unrecognised tendency of the defecation cycle to compensate for cycles with aberrant length by adjusting the length of the following cycle.ConclusionThus TRPM channels regulate the variability of the defecation oscillator in C. elegans. We conclude that the mean and the variability of the defecation oscillator are separable. Our results support the notion that there is a strong underlying pacemaker which is able to function independently of the observable defecation rhythm and is not perturbed by increases in the variability of the cycle.The interaction of gon-2 and gtl-1 with other components of the oscillator shows that TRPM channels play an important role in the oscillator machinery. Such a role may be through either regulation of cation levels or membrane properties or both. Specifically our results support previous proposals that gon-2 and gtl-1 regulate IP3 signalling and that kqt-3 may act by altering calcium influx.Our results provide novel insights into the properties of the defecation oscillator and thus to our understanding of ultradian rhythms.

Glioblastoma (GBM) is the most common and aggressive primary brain cancer. Current standard-of-care includes surgery followed by chemo-radiation and temozolomide. An unmethylated promoter for O6-methylguanine-DNA-methyltransferase (MGMT) is a validated biomarker for temozolomide-resistance and is strongly correlated with poor outcomes. Unmethylated MGMT represents the majority of newly diagnosed GBM tumors. VAL-083 is a first-in-class bi-functional DNA-targeting agent that has shown activity against GBM in NCI-sponsored clinical trials both as single agent and in combination with radiotherapy. VAL-083 induces interstrand cross-links at N7-guanine, leading to DNA double-strand breaks and cell-death. VAL-083’s unique mechanism-of-action circumvents MGMT-mediated chemoresistance, and it has demonstrated cytotoxicity in MGMT-unmethylated GBM cell-lines, cancer stem cells (CSCs) and in vivo models. Furthermore, VAL-083 acts as a radiosensitizer in GBM CSCs and non-CSCs. We completed a dose-escalation trial of VAL-083 in recurrent GBM, and a generally well-tolerated dosing regimen was selected for further clinical development. The present trial is an ongoing open-label, biomarker-driven, Phase I/II study to evaluate the tolerability and efficacy of VAL-083 in combination with radiotherapy in newly diagnosed MGMT-unmethylated GBM patients. A treatment regimen, consisting of a 6-week induction period of VAL-083 and concurrent radiation (2 Gy daily, 5 days/week) followed by up to 24 weeks of maintenance therapy with single-agent VAL-083, is being evaluated. The study is being conducted in two parts. The dose-confirmation part (20, 30, and 40 mg/m2/day IV infusion on days 1-3 of a 21-day cycle) has been completed, and the expansion part has been initiated in up to 20 additional patients at 30 mg/m2/day IV infusion on days 1-3 of a 21-day cycle. Tumor response will be assessed by MRI, according to RANO criteria. Efficacy endpoints include progression-free survival (PFS) and overall survival (OS). Additional endpoints include safety evaluations and pharmacokinetic assessments of plasma and CSF samples. Trial design, enrollment and safety data update will be provided at the meeting. Clinicaltrials.gov identifier: NCT03050736. Citation Format: Zhong-ping Chen, Chengcheng Guo, Jeffrey Bacha, John Langlands, Anne Steino, Claire Kwan, Sarath Kanekal, Richard Schwartz, Lorena Lopez, Dennis Brown. Phase I/II study of dianhydrogalactitol (VAL-083) with radiation therapy in patients with newly diagnosed, MGMT-unmethylated glioblastoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr CT116.

Approximately 60% of glioblastoma multiforme (GBM) patients possess an unmethylated methylguanine DNA-methyltransferase (MGMT gene, which confers a limited response to standard of care treatment with temozolomide (TMZ) resulting in a lower survival. VAL-083 is a novel bi-functional DNA targeting agent that induces interstrand cross-links at N7-guanine, leading to DNA double-strand breaks and ultimately cell death. VAL-083 circumvents MGMT-mediated repair of the O6 guanine alkylator TMZ. A Phase 2 study has been initiated for VAL-083 in newly diagnosed MGMT unmethylated GBM. The study has 2 stages: Stage 1 is a dose-escalation and induction format to confirm the recommended dose of VAL-083 when administered concurrently with radiation therapy (RT) based on safety and tolerability. The subjects received VAL-083 at 20, 30, or 40 mg/m2/day x 3 days every 21 days along with standard radiation treatment. Stage 2 comprises an expansion phase to enroll up to 30 patients. The dose escalation stage is complete and 30 mg/m2/day of VAL-083 in combination with RT was generally safe and well-tolerated. As of 17 May, 2019, 18 patients have been enrolled. Fifteen patients have completed their prospectively planned MRI scans and had their initial assessment for tumor progression. Of these 15 patients, seven were assessed as a complete response (CR), and eight patients as having stable disease (SD). Of the remaining three patients, one died prior to their post-cycle 3 MRI and two have not been on study long enough to reach their planned post-cycle 3 MRI. As of the data cutoff, 14 of the 18 patients were still alive. Consistent with our prior experience, myelosuppression was the most common adverse event. Three dose-limiting toxicities have been reported - one at the 40 mg/m2/day and two at the 30 mg/m2/day dose. Further enrollment, safety & study updates will be presented at the meeting. Clinicaltrials.gov identifier: NCT03050736.

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Glioblastoma (GBM) is the most common and aggressive primary brain cancer. Current standard-of-care includes surgery followed by concomitant chemo-radiation and adjuvant temozolomide (TMZ). Unmethylated promoter status for O6-methylguanine-DNA-methyltransferase (MGMT), a validated biomarker for TMZ-resistance, is strongly correlated with TMZ-resistance. In addition, defective DNA mismatch repair (MMR) has been identified as a secondary mechanism of TMZ resistance. MGMT-unmethylated tumors represent a majority of newly diagnosed GBM patients demonstrating significantly inferior progression free and overall survival compared to MGMT-methylated GBM patients. VAL-083 is a first-in-class bi-functional DNA-targeting agent that has shown activity against GBM in NCI-sponsored clinical trials both as a single agent and in combination with radiotherapy. VAL-083 rapidly induces interstrand DNA cross-links at N7-guanine, leading to persistent DNA double-strand breaks and cell death in GBM cell lines and GBM cancer stem cells (CSCs). VAL-083's unique cytotoxic mechanism circumvents MGMT-mediated chemoresistance and maintains cytotoxic activity in cancer cells deficient in MMR. Furthermore, VAL-083 acts as a radiosensitizer in GBM CSCs and non-CSCs, in vitro. We completed a 3:3 dose-escalation trial of VAL-083 in temozolomide- and bevacizumab-refractory rGBM. 40mg/m2/day given on days 1, 2, and 3 of a 21-day cycle was well-tolerated with 6% grade 3 or 4 thrombocytopenia. This dose was selected for further clinical development in a pivotal Phase 3 study in bevacizumab refractory rGBM. The present trial is an ongoing open-label, biomarker-driven, Phase 1/2 study to evaluate the tolerability and efficacy of VAL-083 in combination with radiotherapy in newly diagnosed MGMT-unmethylated GBM patients. A treatment regimen, consisting of a 6-week induction period of VAL-083 and concurrent radiation (2 Gy given daily, 5 days/week) followed by up to 24 weeks of adjuvant maintenance therapy with single-agent VAL-083, is being evaluated as an alternative to standard-of-care in MGMT-unmethylated GBM. The study is being conducted in two parts: 1) a dose-escalation part (20, 30, and 40 mg/m2/day IV infusion on days 1, 2, and 3 of a 21-day cycle) in up to 10 patients, to assess safety and activity of VAL-083 when administered concurrently with radiation therapy; 2) an expansion phase, in which VAL-083 will be studied in up to 20 additional patients at the determined well-tolerated dose. Tumor response will be assessed by MRI, according to RANO criteria. Efficacy endpoints include progression-free survival (PFS) and overall survival (OS). Additional endpoints include safety evaluations and pharmacokinetic assessments of plasma and CSF samples (when available). Enrollment and safety data update will be provided at the meeting. Clinicaltrials.gov identifier: NCT03050736. Citation Format: Zhong-ping Chen, Chengcheng Guo, Jeffrey Bacha, Anne Steino, John Langlands, Claire Kwan, Sarath Kanekal, Richard Schwartz, Lorena Lopez, Dennis M. Brown. Phase I/II study of dianhydrogalactitol (VAL-083) with radiation therapy in patients with newly diagnosed glioblastoma, MGMT-unmethylated [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 CT168.

Approximately 60% of glioblastoma multiforme (GBM) patients possess an unmethylated methylguanine DNA-methyltransferase (MGMT) promoter region, which confers a limited response to standard-of-care treatment with temozolomide (TMZ), resulting in shorter median survival when compared to patients with methylated MGMT promoter. VAL-083 is a novel bi-functional DNA targeting agent that induces inter-strand cross-links at N7-guanine, leading to DNA double-strand breaks and ultimately cell death. VAL-083 circumvents MGMT-mediated TMZ resistance in vitro and in vivo. A Phase 2 study has been initiated for VAL-083 in newly diagnosed MGMT unmethylated GBM. The study has 2 stages: Stage 1 is a dose-escalation safety and tolerability phase to confirm the phase 2 dose of VAL-083 when administered concurrently with radiation therapy (RT). Patients received VAL-083 at 20, 30, or 40 mg/m2/day x 3 days every 21 days along with standard radiation treatment (RT) (2 Gy/day, 5 days/week). The dose escalation stage is complete, and 30 mg/m2/day of VAL-083 in combination with RT was generally safe and well-tolerated. Stage 2 comprises an expansion phase to enroll up to 20 additional patients at the 30 mg/m2/day of VAL-083 in combination with RT. As of June 2, 2020, all patients have been enrolled, with a total of 29 patients in the study, and 25 patients receiving 30 mg/m2/day VAL-083. Of the 29 patients enrolled, 27 have completed their prospectively planned MRI scans and had their initial assessment for tumor response. Two additional patients died prior to their post-cycle 3 MRI. Consistent with our prior experience, myelosuppression was the most common adverse event. Three patients have experienced dose-limiting toxicities - one (1/3; 33%) at the 40 mg/m2/day and two (2/25; 8%) at the 30 mg/m2/day dose. Further safety and efficacy updates will be presented at the meeting. Clinicaltrials.gov identifier: NCT03050736.