Keith Dredge

Protective antitumor immunity induced by a costimulatory thalidomide analog in conjunction with whole tumor cell vaccination is mediated by increased Th1-type immunity.

Thalidomide and its novel T cell costimulatory analogs (immunomodulatory drugs) are currently being assessed in the treatment of patients with advanced cancer. However, neither tumor-specific T cell costimulation nor effective antitumor activity has been demonstrated in vivo. In this study, we assessed the ability of an immunomodulatory drug (CC-4047/ACTIMID) to prime a tumor-specific immune response following tumor cell vaccination. We found that the presence of CC-4047 during the priming phase strongly enhanced antitumor immunity in the vaccinated group, and this correlated with protection from subsequent live tumor challenge. Protection was associated with tumor-specific production of IFN-γ and was still observed following a second challenge with live tumor cells 60 days later. Furthermore, CD8+ and CD4+ splenocyte fractions from treated groups secreted increased IFN-γ and IL-2 in response to tumor cells in vitro. Coculture of naive splenocytes with anti-CD3 mAb in the presence of CC-4047 directly costimulated T cells and increased Th1-type cytokines. Our results are the first to demonstrate that a costimulatory thalidomide analog can prime protective, long-lasting, tumor-specific, Th1-type responses in vivo and further support their ongoing clinical development as novel anti-cancer agents.

Thalidomide and its analogues have distinct and opposing effects on TNF-α and TNFR2 during co-stimulation of both CD4+ and CD8+ T cells

Thalidomide (Thd) is clinically useful in a number of conditions where its efficacy is probably related to its anti‐TNF‐α activity. More recently, Thd has also been shown to co‐stimulate T cells and second generation co‐stimulatory (IMiD™) analogues are currently being assessed in the treatment of cancer patients. However, in contrast to their known suppressive effects during inflammatory stimuli, the effects of Thd/IMiDs on TNF‐α and TNF receptors (TNFRs) during T cell co‐stimulation are not known. We sought to determine the effect of Thd, two clinically relevant IMiDs (CC‐4047, ACTIMID™ and CC‐5013, REVIMID™) and a non‐stimulatory SelCID analogue (CC‐3052) on TNF‐α production and on the expression and shedding of TNFRs during co‐stimulation. We found that co‐stimulation of PBMC with Thd/IMiDs, but not CC‐3052, prevented αCD3‐induced T cell surface expression of TNFR2 and thereby reduced soluble TNFR2 (sTNFR2) levels. However, there was no effect on total (surface/intracellular) TNFR2 protein expression, suggesting inhibition of trafficking to the cell membrane. The extent of co‐stimulation by Thd/IMiDs (assessed by CD69/CD25 expression and IL‐2/sIL‐2Rα production) was similar for CD4+ and CD8+ T lymphocytes and correlated with TNFR2 inhibition. Co‐stimulation, but not the early inhibitory effect on TNFR2, was IL‐2‐dependent and led to increased TNF‐α production by both CD4+ and CD8+ T lymphocytes. The clinical relevance of this observation was confirmed by the elevation of serum TNF‐α during REVIMID™ treatment of patients with advanced cancer. Together, these results suggest a possible role for TNF‐mediated events during co‐stimulation and contrast with the TNF inhibitory effects of Thd and its analogues during inflammatory stimuli.

Recent developments in antiangiogenic therapy

The use of antiangiogenic therapy is gaining momentum as a novel treatment for a number of conditions, ranging from cancer to psoriasis. This has stemmed from research in the early 1970s showing that the formation of new blood vessels by pre-existing endothelial cells is essential in tumour growth and progression. However, although antiangiogenic therapy was hailed as a new avenue of treatment for cancer, initial clinical data have been disappointing. This has led to the reassessment of antiangiogenic therapy for cancer, and new strategies have been proposed to increase the efficacy of these agents in this setting. Angiogenesis has also been implicated in other conditions that are notoriously difficult to treat, such as arteriosclerosis, arthritis, psoriasis and diabetic retinopathy. Increased understanding of the angiogenic process, the diversity of its inducers and mediators, appropriate drug schedules and the use of these agents with other modalities may lead to radically new treatment regimens for many of these conditions. The role of angiogenesis in different pathological settings, and emerging antiangiogenic agents currently in preclinical and clinical studies are discussed in this review. However, while potential benefits are profound, limitations of antiangiogenic therapy have also been identified, suggesting that there is also a need for caution in applying these compounds to the clinical setting.

The Role of Heparanase and Sulfatases in the Modification of Heparan Sulfate Proteoglycans within the Tumor Microenvironment and Opportunities for Novel Cancer Therapeutics.

Heparan sulfate proteoglycans (HSPGs) are an integral and dynamic part of normal tissue architecture at the cell surface and within the extracellular matrix. The modification of HSPGs in the tumor microenvironment is known to result not just in structural but also functional consequences, which significantly impact cancer progression. As substrates for the key enzymes sulfatases and heparanase, the modification of HSPGs is typically characterized by the degradation of heparan sulfate (HS) chains/sulfation patterns via the endo-6-O-sulfatases (Sulf1 and Sulf2) or by heparanase, an endo-glycosidase that cleaves the HS polymers releasing smaller fragments from HSPG complexes. Numerous studies have demonstrated how these enzymes actively influence cancer cell proliferation, signaling, invasion, and metastasis. The activity or expression of these enzymes has been reported to be modified in a variety of cancers. Such observations are consistent with the degradation of normal architecture and basement membranes, which are typically compromised in metastatic disease. Moreover, recent studies elucidating the requirements for these proteins in tumor initiation and progression exemplify their importance in the development and progression of cancer. Thus, as the influence of the tumor microenvironment in cancer progression becomes more apparent, the focus on targeting enzymes that degrade HSPGs highlights one approach to maintain normal tissue architecture, inhibit tumor progression, and block metastasis. This review discusses the role of these enzymes in the context of the tumor microenvironment and their promise as therapeutic targets for the treatment of cancer.

PG545, a heparan sulfate mimetic, reduces heparanase expression in vivo, blocks spontaneous metastases and enhances overall survival in the 4T1 breast carcinoma model

PG545 is a clinically relevant heparan sulfate (HS) mimetic which, in addition to possessing anti-angiogenic properties, also acts as a heparanase inhibitor which may differentiate its mechanism(s) of action from approved angiogenesis inhibitors. The degradation of HS by heparanase has been strongly implicated in cell dissemination and the metastatic process. Thus, the anti-metastatic activity of PG545 has been linked to the enzymatic function of heparanase – the only endoglycosidase known to cleave HS, an important component of the extracellular matrix (ECM) which represents a potential avenue for therapeutic intervention for certain metastatic cancer indications. Recent concerns raised about the paucity of overall survival as an endpoint in mouse models of clinically relevant metastasis led us to examine the effect of PG545 on the progression of both primary tumor growth and the spontaneously metastasizing disease in the 4T1 syngeneic breast carcinoma model in a non-surgical and surgical (mastectomy) setting. PG545 significantly inhibited primary tumor growth but importantly also inhibited lung metastasis in treated mice, an effect not observed with the tyrosine kinase inhibitor sorafenib. Importantly, PG545 significantly enhanced overall survival compared to vehicle control and the sorafenib group, suggesting PG545’s inhibitory effect on heparanase is indeed a critical attribute to induce anti-metastatic activity. In addition to blocking a common angiogenic signalling pathway in tumor cells, the expression of heparanase in the primary tumor and lung was also significantly reduced by PG545 treatment. These results support the ongoing development of PG545 and highlight the potential utility in metastatic disease settings.

PG545, an Angiogenesis and Heparanase Inhibitor, Reduces Primary Tumor Growth and Metastasis in Experimental Pancreatic Cancer

Aggressive tumor progression, metastasis, and resistance to conventional therapies lead to an extremely poor prognosis for pancreatic ductal adenocarcinoma (PDAC). Heparanase, an enzyme expressed by multiple cell types, including tumor cells in the tumor microenvironment, has been implicated in angiogenesis and metastasis, and its expression correlates with decreased overall survival in PDAC. We evaluated the therapeutic potential of PG545, an angiogenesis and heparanase inhibitor, in experimental PDAC. PG545 inhibited the proliferation, migration, and colony formation of pancreatic cancer cells in vitro at pharmacologically relevant concentrations. Heparanase inhibition also reduced the proliferation of fibroblasts but had only modest effects on endothelial cells in vitro. Furthermore, PG545 significantly prolonged animal survival in intraperitoneal and genetic models (mPDAC: LSL-KrasG12D; Cdkn2alox/lox; p48Cre) of PDAC. PG545 also inhibited primary tumor growth and metastasis in orthotopic and genetic endpoint studies. Analysis of tumor tissue revealed that PG545 significantly decreased cell proliferation, increased apoptosis, reduced microvessel density, disrupted vascular function, and elevated intratumoral hypoxia. Elevated hypoxia is a known driver of collagen deposition and tumor progression; however, tumors from PG545-treated animals displayed reduced collagen deposition and a greater degree of differentiation compared with control or gemcitabine-treated tumors. These results highlight the potent antitumor activity of PG545 and support the further exploration of heparanase inhibitors as a potential clinical strategy for the treatment of PDAC. Mol Cancer Ther; 12(7); 1190–201. ©2013 AACR.

Thalidomide Derived Immunomodulatory Drugs (IMiDs) as Potential Therapeutic Agents

Thalidomide is known to be effective in the treatment of a number of conditions, including leprosy and various cancers. The exact mechanisms of action remain unclear although these are known to include anti-tumour necrosis factor (TNF)-alpha, T cell costimulatory, anti-angiogenic and anti-tumour activities. However, thalidomide is being superceded by novel structural derivatives which have been designed to have improved immunomodulatory activity and side effect profiles. These are currently being characterised and some are entering the clinic in phase I/II studies. One novel group of structural analogues are classified as the Immunomodulatory Drugs (IMiDs). This review describes the emerging immunological, anti-angiogenic and direct anti-tumour properties of thalidomide and the characterisation and clinical application of its IMiD analogues. We describe the laboratory studies which have led to the characterisation and development of IMiDs into potentially clinically relevant drugs. Early trial data suggests that these compounds may themselves become established therapies, particularly in certain cancers. Furthermore, ongoing studies will determine how best to apply these compounds to the appropriate clinical settings. We will describe the various clinical studies of lead compounds that are in progress and speculate as to the potential and future development of these exciting compounds.

Abstract A18: The dual angiogenesis/heparanase inhibitor PG545, but not the tyrosine kinase inhibitor sorafenib, inhibits spontaneous metastasis in models of breast and lung cancer

PG545 is a fully synthetic heparan sulfate (HS) mimetic selected as the lead oncology candidate for formal preclinical development. PG545 inhibits key processes in tumor progression (a) neovascularization ‐ by interfering with growth factor binding and (b) metastasis ‐ presumably by inhibition of heparanase activity. PG545 was assessed for anti‐angiogenic activity in vivo and for antitumor and anti‐metastatic activity in the T41 breast cancer and the Lewis Lung Carcinoma (LL/2) models using the tyrosine kinase inhibitor sorafenib as an anti‐angiogenic reference compound. Both PG545 (daily or twice weekly) and sorafenib (daily) significantly reduced CD31 staining in the AngioSponge™ model. Twice weekly treatment with 25 mg/kg PG545, but not daily treatment with 60mg/kg sorafenib, significantly inhibited solid tumor growth in the T41 model. Moreover, PG545 significantly inhibited spontaneous lung metastases in a dose‐dependent manner, whereas sorafenib significantly increased the number of metastases. In the LL/2 model, once weekly treatment with PG545 at 20 mg/kg significantly reduced solid tumor growth to a similar extent as sorafenib while the 40mg/kg dose appeared more efficacious than sorafenib. A significant reduction in spontaneous lung metastases was again associated with PG545 following either a single injection or once weekly treatment while sorafenib had no appreciable effect on metastases. PG545 was well tolerated with no significant loss in bodyweight noted. Taken together, the data demonstrate that PG545 is an effective angiogenesis inhibitor with anti‐metastatic activity ‐ an envious property for an anti‐cancer compound, allaying recently publicized concerns that angiogenesis inhibitors and even chemotherapeutic agents may have the potential to aggravate metastatic development. Citation Information: Mol Cancer Ther 2009;8(12 Suppl):A18.

Abstract 1135: Loss of HSulf-1 promotes defective autophagy and increased lipid droplet biogenesis in ovarian cancer

Proceedings: AACR 106th Annual Meeting 2015; April 18-22, 2015; Philadelphia, PA Dysregulation of autophagy and altered metabolic pathways are frequently observed in cancer. Due to these alterations, pharmacological targeting of these two pathways simultaneously could provide a viable therapeutic option. Although the association between these two pathways is well characterized in metabolic disorders, it is not well defined in ovarian cancer (OVCA). In this regard, we found that loss of endosulfatase HSulf-1, a known putative tumor suppressor, suppresses LC3-GFP foci formation and promotes increased lipid droplet (LD) biogenesis suggesting that absence of HSulf-1 in OVCA affects both autophagy and lipid metabolism. While isogenic cells with genetic ablation of HSulf-1 (OV202Sh1/2 and TOV2223Sh1 cells) displayed LDs, the nontargeted control transduced (NTC) OV202 and TOV2223 cells had significantly less LDs. In contrast, Transmission Electron Micrographs (TEMs) showed that OV202 and TOV2223 NTC cells had significantly more autophagic vacuoles (AVs) compared to their isogenic ShRNA targeted cells. Conversely, ectopic expression of HSulf-1 in SKOV3 cells decreased the number of LDs and increased the number of AVs compared to vector transfected controls. Here we report that OV202Sh1 cells and HSulf-1 deficient OV2008 cells have increased p-cPLA2α(ser505) levels that are associated with biogenesis of large number of LDs with reduced AVs. Interestingly, pharmacological inhibition of cPLA2α with AACOCF3 in OV202Sh1 cells resulted in reduced LD biogenesis, inhibited colony formation and reduced tumorigenesis in vivo. More importantly, treatment of HSulf-1 deficient cells with HS mimetic PG545 which can compensate for loss of HSulf-1, reduced LD biogenesis, promoted autophagy and inhibited tumor growth in vivo. Collectively, these results show a critical role of HSulf-1 in regulating both autophagy and LD biogenesis in ovarian cancer. Citation Format: Debarshi Roy, Susmita Mondal, Ashwani Khurana, Xiaoping He, Edward Hammond, Keith Dredge, Viji Shridhar. Loss of HSulf-1 promotes defective autophagy and increased lipid droplet biogenesis in ovarian cancer. [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 1135. doi:10.1158/1538-7445.AM2015-1135

Abstract 3695: The utility of plasma vascular endothelial growth factor and heparanase as pharmacodynamic markers following treatment with PG545, a heparan sulfate mimetic: preliminary evidence from preclinical and clinical settings

Proceedings: AACR Annual Meeting 2014; April 5-9, 2014; San Diego, CA Background: The heparan sulfate mimetic PG545 has been demonstrated to inhibit the function of vascular endothelial growth factor (VEGF) and heparanase (HPSE) in vitro whilst downregulating HPSE expression in tumor and metastatic tissue in vivo. Although there are reports of consistent drug-induced increases in plasma VEGF with VEGF inhibitors such as bevacizumab, similar data are lacking for HS mimetics. Given PG545s mechanism of action which involves inhibition of both angiogenesis and metastasis, the evaluation of plasma VEGF and HPSE may represent pharmacodynamic (PD) biomarkers for each of these key processes. Materials and Methods: The levels of plasma VEGF and HPSE were measured using ELISA in samples from preclinical models of ovarian cancer (syngeneic ID8 and xenogeneic A2780 models) and a small cohort of patients (dosed with PG545 by the subcutaneous route) with advanced solid tumors from a Phase I clinical study. In tumor models, PG545 was administered once weekly by intravenous or intraperitoneal routes and efficacy was determined by quantifying tumor burden using the following methods: measurement of palpable solid tumors, abdominal circumference, ascites volume and/or by tracking cells using bioluminescent reporter imaging (depending on the model). In the A2780 model and the clinical samples, the pharmacokinetics of PG545 was also evaluated using LC-MS/MS, which ensured multiple samples to facilitate the measurement of VEGF and HPSE in plasma over the duration of the dosing interval following treatment with PG545. Results: PG545 demonstrated potent antitumor and antimetastatic activity when administered once weekly via intravenous or intraperitoneal routes in preclinical studies. These studies also indicated that PG545 treatment led to increases in plasma VEGF and HPSE. Importantly, plasma samples from advanced cancer patients treated with PG545 also revealed increases in these PD markers with initial peaks often correlating with Cmax of PG545 but longer-term gradual increases also noted in some instances. We consider that these increases in plasma levels result from PG545 binding to, thereby inhibiting, VEGF and HPSE in the tumor microenvironment. Conclusion: Given the questionable utility of single time point measures of plasma PD markers (including VEGF), these preliminary data suggest that kinetic profiling can reveal the previously undetermined dynamics of circulating VEGF and HPSE following treatment with PG545. Thus, the measurement of VEGF and HPSE appears to represent potential markers of pharmacodynamic activity. A new Phase I trial with intravenously-administered PG545 has recently commenced and should further clarify the potential utility of these basic PD biomarker responses in advanced cancer patients. Citation Format: Keith Dredge, Edward Hammond, Boris Winterhoff, Shailendra Giri, Attila Teoman, Darryn Bampton, Michael Millward, Viji Shridhar. The utility of plasma vascular endothelial growth factor and heparanase as pharmacodynamic markers following treatment with PG545, a heparan sulfate mimetic: preliminary evidence from preclinical and clinical settings. [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 3695. doi:10.1158/1538-7445.AM2014-3695