Gabriel Kremmidiotis

Discovery of 7-Hydroxy-6-methoxy-2-methyl-3-(3,4,5- trimethoxybenzoyl)benzo[b]furan (BNC105), a Tubulin Polymerization Inhibitor with Potent Antiproliferative and Tumor Vascular Disrupting Properties

A structure-activity relationship (SAR) guided design of novel tubulin polymerization inhibitors has resulted in a series of benzo[b]furans with exceptional potency toward cancer cells and activated endothelial cells. The potency of early lead compounds has been substantially improved through the synergistic effect of introducing a conformational bias and additional hydrogen bond donor to the pharmacophore. Screening of a focused library of potent tubulin polymerization inhibitors for selectivity against cancer cells and activated endothelial cells over quiescent endothelial cells has afforded 7-hydroxy-6-methoxy-2-methyl-3-(3,4,5-trimethoxybenzoyl)benzo[b]furan (BNC105, 8) as a potent and selective antiproliferative. Because of poor solubility, 8 is administered as its disodium phosphate ester prodrug 9 (BNC105P), which is rapidly cleaved in vivo to return the active 8. 9 exhibits both superior vascular disrupting and tumor growth inhibitory properties compared with the benchmark agent combretastatin A-4 disodium phosphate 5 (CA4P).

BNC105: A novel tubulin polymerization inhibitor that selectively disrupts tumor vasculature and displays single-agent antitumor efficacy

Vascular disruption agents (VDA) cause occlusion of tumor vasculature, resulting in hypoxia-driven tumor cell necrosis. Tumor vascular disruption is a therapeutic strategy of great potential; however, VDAs currently under development display a narrow therapeutic margin, with cardiovascular toxicity posing a dose-limiting obstacle. Discovery of new VDAs, which display a wider therapeutic margin, may allow attainment of improved clinical outcomes. To identify such compounds, we used an in vitro selectivity screening approach that exploits the fact that tumor endothelial cells are in a constant state of activation and angiogenesis and do not undergo senescence. Our effort yielded the compound BNC105. This compound acts as a tubulin polymerization inhibitor and displays 80-fold higher potency against endothelial cells that are actively proliferating or are engaged in the formation of in vitro capillaries compared with nonproliferating endothelial cells or endothelium found in stable capillaries. This selectivity was not observed with CA4, a VDA currently under evaluation in phase III clinical trials. BNC105 is more potent and offers a wider therapeutic window. CA4 produces 90% vascular disruption at its no observed adverse event level (NOAEL), whereas BNC105 causes 95% vascular disruption at 1/8th of its NOAEL. Tissue distribution analysis of BNC105 in tumor-bearing mice showed that while the drug is cleared from all tissues 24 hours after administration, it is still present at high concentrations within the solid tumor mass. Furthermore, BNC105 treatment causes tumor regressions with complete tumor clearance in 20% of treated animals. Mol Cancer Ther; 9(6); 1562–73. ©2010 AACR.

A phase II clinical trial of the vascular disrupting agent BNC105P as second line chemotherapy for advanced Malignant Pleural Mesothelioma.

BNC105P is a tubulin polymerisation inhibitor that selectively disrupts tumour vasculature and suppresses cancer cell proliferation. This agent has exhibited preclinical and phase I activity in Malignant Pleural Mesothelioma (MPM). This phase II, single arm trial investigated the efficacy and safety of BNC105P as second line therapy in MPM. Participants had progressive MPM after first line pemetrexed/platinum chemotherapy, ECOG PS 0-1, adequate organ function, and measurable disease. BNC105P 16 mg/m(2) was administered intravenously on day 1 and 8 every 21 days until progression or undue toxicity. The primary endpoint was centrally reviewed objective response rate (RR). Tumour response was assessed every two cycles using modified RECIST. 30 patients were enrolled in 10 months, predominantly male (90%), ECOG PS 1 (77%), epithelioid histology (67%), and non-metastatic disease (67%). All patients received at least one dose of study drug, with a median of 2 cycles. No significant haematologic, biochemical, or cardiac adverse events (AEs) were observed. Grade 3 or 4 AEs occurred in 10 patients (33%). There were 2 deaths on study: 1 cardiorespiratory, the other to pneumonia. We observed 1 partial response (3%); 13 patients had stable disease (43%). Median progression free survival was 1.5 months (95% CI 1.4-2.4); median overall survival was 8.2 months (95% CI 3.8-11.9). BNC105P was safe and tolerable. The sole response was insufficient to warrant further research as a single agent.

Clinical, Pharmacodynamic, and Pharmacokinetic Evaluation of BNC105P: A Phase I Trial of a Novel Vascular Disrupting Agent and Inhibitor of Cancer Cell Proliferation

Purpose: To determine the recommended phase II dose and evaluate the safety and toxicity profile and pharmacokinetic (PK) and pharmacodynamic (PD) effects of BNC105P, an inhibitor of tubulin polymerization that has vascular disrupting and antiproliferative effects. Experimental Design: BNC105P was administered as a 10-minute infusion on days 1 and 8 of a 21-day cycle in a first-in-human phase I study. A dynamic accelerated dose titration method was used for dose escalation. Plasma concentrations of BNC105P (phosphate prodrug) and BNC105 (active agent) were determined. PD assessments were carried out using dynamic contrast enhanced (DCE)-MRI and analysis of a blood-borne biomarker. Results: Twenty-one subjects with advanced solid tumors were enrolled on 6 dose levels (range: 2.1–18.9 mg/m2). The recommended dose level was 16 mg/m2 and was well tolerated. BNC105P (prodrug) rapidly converted to BNC105 with a half-life of 0.13 hours. Plasma concentrations of BNC105 generally increased in proportion to dose with a half-life of 0.57 hours. Pharmacodymanically active plasma levels were obtained with a dose dependant reduction in the levels of polymerized tubulin (on-target action) being observed in PBMCs. DCE-MRI also indicated blood flow changes in the tumor lesions of a number of subjects. Conclusions: BNC105P has a favorable toxicity profile at the recommended dose of 16 mg/m2 and is associated with PD changes consistent with its known mechanism of action. Phase II studies in renal cancer and mesothelioma have commenced. Clin Cancer Res; 17(15); 5152–60. ©2011 AACR.

A Phase I/II Trial of BNC105P with Everolimus in Metastatic Renal Cell Carcinoma

Purpose: BNC105P inhibits tubulin polymerization, and preclinical studies suggest possible synergy with everolimus. In this phase I/II study, efficacy and safety of the combination were explored in patients with metastatic renal cell carcinoma (mRCC). Experimental Design: A phase I study in patients with clear cell mRCC and any prior number of therapies was conducted using a classical 3 + 3 design to evaluate standard doses of everolimus with increasing doses of BNC105P. At the recommended phase II dose (RP2D), patients with clear cell mRCC and one to two prior therapies (including ≥ 1 VEGF-TKI) were randomized to BNC105P with everolimus (arm A) or everolimus alone (arm B). The primary endpoint of the study was 6-month progression-free survival (6MPFS). Secondary endpoints included response rate, PFS, overall survival, and exploratory biomarker analyses. Results: In the phase I study (N = 15), a dose of BNC105P at 16 mg/m2 with everolimus at 10 mg daily was identified as the RP2D. In the phase II study, 139 patients were randomized, with 69 and 67 evaluable patients in arms A and B, respectively. 6MPFS was similar in the treatment arms (arm A: 33.82% vs. arm B: 30.30%, P = 0.66) and no difference in median PFS was observed (arm A: 4.7 mos vs. arm B: 4.1 mos; P = 0.49). Changes in matrix metalloproteinase-9, stem cell factor, sex hormone-binding globulin, and serum amyloid A protein were associated with clinical outcome with BNC105P. Conclusions: Although the primary endpoint was not met in an unselected population, correlative studies suggest several biomarkers that warrant further prospective evaluation. Clin Cancer Res; 21(15); 3420–7. ©2015 AACR.

Phase I/II study of a BNC105P/everolimus regimen for progressive metastatic renal cell carcinoma (mRCC) following prior tyrosine kinase inhibitors (Hoosier Oncology Group).

373 Background: BNC105P is a Vascular Disruption Agent (VDA) that destabilizes tubulin polymers leading to selective damage of tumor vasculature, hypoxia and associated tumor necrosis. BNC105P also has a direct anti-proliferative action on cancer cells. Up regulation of the mTOR pathway has been identified as a survival response by the tumor to hypoxic insult. Preclinical investigations demonstrated that BNC105P is effective at selectively damaging the vasculature in primary and metastatic lesions. Furthermore, BNC105P monotherapy compared well with sunitinib in mice bearing kidney tumors. It follows that the combined use of this VDA with an agent active against mTOR may improve clinical outcome in patients with progressive mRCC who are refractory to tyrosine kinase inhibitors (TKI). METHODS A phase I/II study in mRCC patients who have received 1-2 prior TKIs was undertaken. Using a classic 3+3 design, the phase I component of this study enrolled 12 subjects at 4 dose levels of BNC105P (4.2, 8.4, 12.6 and 16 mg/m2; IV infusion Days 1 & 8, 21-day repeating cycle). Everolimus was administered concurrently (10 mg p.o.). PK analysis was performed during Cycle 1. RESULTS In the clinic the BNC105P / everolimus combination was well tolerated and no DLTs were observed in any of the phase I patients. Toxicities deemed to be drug-related included single events of Grade 2 anemia, thrombocytopenia and mucositis. Of the 12 patients enrolled to the phase I, 7 remain on treatment. The medium number of cycles is 3 (range: 1-14) and 3 patients have been administered >6 cycles of treatment. The randomized phase II component of the study continues and will compare everolimus given in combination with BNC105P to a sequential approach (everolimus followed by BNC105P). CONCLUSIONS The MTD of BNC105P (16 mg/m2) can be combined with full dose everolimus and is being evaluated in the randomized phase II study.

Updated phase I results of a phase I/II trial of BNC105P with everolimus in patients with metastatic renal cell carcinoma (mRCC).

397 Background: BNC105P is an inhibitor of tubulin polymerization. In vivo exposure to BNC105P leads to selective damage of tumor vasculature in both primary and metastatic lesions, causing disruption of blood flow to tumors, hypoxia and associated tumor necrosis. BNC105P also has a direct anti-proliferative action on cancer cells. Up regulation of the mTOR pathway has been identified as a cellular response to hypoxic stress. The combined use of BNC105P with an agent active against mTOR may improve clinical outcome in patients with progressive mRCC who are refractory to VEGFR-directed tyrosine kinase inhibitors (TKI). METHODS A phase I/II study in mRCC patients who have received 1-2 prior TKIs was undertaken. The phase I component enrolled 12 subjects at 4 dose levels of BNC105P (4.2, 8.4, 12.6, 16 mg/m2; IV infusion Days 1 and 8, 21-day repeating cycle). Everolimus was administered concurrently (10 mg p.o.). PK analysis was performed during cycle 1. RESULTS Updated results from the completed phase I component confirm the BNC105P/everolimus combination was well tolerated. No DLTs (drug-related, during cycle 1) were observed in any of the phase I subjects. Toxicities on study deemed to be drug-related (either single agent or combination) included single grade 3 events of anemia and pericardial effusion. Grade 2 events (more than 1 occurrence) of fatigue, anemia, and oral mucositis were also observed. 8 of the 12 phase I subjects achieved disease stabilization (7 of these subjects had a minimum time on therapy of 18 weeks, 6 cycles). Across all subjects a median of 6 cycles (range: 1-21) was administered, with removal from study predominantly due to disease progression. PK analysis confirmed no drug-drug interaction. The randomized phase II component of the study continues and will compare everolimus given concomitantly with BNC105P to a sequential approach (everolimus followed by BNC105P). CONCLUSIONS BNC105P (16 mg/m2) can be combined with full dose everolimus and is being evaluated in a randomized phase II study. CLINICAL TRIAL INFORMATION NCT01034631.

Discovery and validation of drug targets for tumour angiogenesis

The formation of blood vessels is a key process in the progression of solid tumours, providing the means for tumour growth and metastasis. A number of drugs are currently being developed to exploit inhibition of angiogenesis in the therapy of cancer. An even greater number of genes that are regulated in models of invitro angiogenesis have been identified. These genes present potential drug targets for the development of novel, more efficient, drugs that will enable the judicious design of drug cocktails that may be able to account for the many different cancer pathologies and their drug resistance properties. Dealing with the validation of hundreds of potential angiogenesis drug targets requires the utilisation of experimental technology platforms that enable concomitant and dynamic target selection filtering and validation. Such platforms should act as a funnel-like medium-to-low throughput processes that enable the sequential short-listing of hundreds of candidates culminating in the selection of only a small number of well-vali-dated targets that are manageable by drug screening regimes.