Tasquinimod (ABR-215050), a quinoline-3-carboxamide anti-angiogenic agent, modulates the expression of thrombospondin-1 in human prostate tumors

Thrombospondin-1 in urological cancer: pathological role, clinical significance, and therapeutic prospects

Angiogenesis is an important process for tumor growth and progression of various solid tumors including urological cancers. Thrombospondins (TSPs), especially TSP-1, are representative “anti”-angiogenic molecules and many studies have clarified their pathological role and clinical significance in vivo and in vitro. In fact, TSP-1 expression is associated with clinicopathological features and prognosis in many types of cancers. However, TSP-1 is a multi-functional protein and its biological activities vary according to the specific tumor environments. Consequently, there is no general agreement on its cancer-related function in urological cancers, and detailed information regarding regulative mechanisms is essential for a better understanding of its therapeutic effects and prognostic values. Various “suppressor genes” and “oncogenes” are known to be regulators and TSP-1-related factors under physiological and pathological conditions. In addition, various types of fragments derived from TSP-1 exist in a given tissue microenvironment and TSP-1 derived-peptides have specific activities. However, a detailed pathological function in human cancer tissues is not still understood. This review will focus on the pathological roles and clinical significance of TSP-1 in urological cancers, including prostate cancer, renal cell carcinoma, and urothelial cancer. In addition, special attention is paid to TSP-1-derived peptide and TSP-1-based therapy for malignancies.

Common interactions between S100A4 and S100A9 defined by a novel chemical probe

S100A4 and S100A9 proteins have been described as playing roles in the control of tumor growth and metastasis. We show here that a chemical probe, oxyclozanide (OX), selected for inhibiting the interaction between S100A9 and the receptor for advanced glycation end-products (RAGE) interacts with both S100A9 and S100A4. Furthermore, we show that S100A9 and S100A4 interact with RAGE and TLR4; interactions that can be inhibited by OX. Hence, S100A4 and S100A9 display similar functional elements despite their primary sequence diversity. This was further confirmed by showing that S100A4 and S100A9 dimerize both in vitro and in vivo. All of these interactions required levels of Zn⁺⁺ that are found in the extracellular space but not intracellularly. Interestingly, S100A4 and S100A9 are expressed by distinct CD11b⁺ subpopulations both in healthy animals and in animals with either inflammatory disease or tumor burden. The functions of S100A9 and S100A4 described in this paper, including heterodimerization, may therefore reflect S100A9 and S100A4 that are released into the extra-cellular milieu.

A review of tasquinimod in the treatment of advanced prostate cancer

Castration resistant prostate cancer remains a major clinical burden and novel therapeutic options are urgently required to improve survival. Tasquinimod is an orally administered quinoline-3-carboxamide with potent antiangiogenic and antitumorigenic action that has shown promise in the treatment of advanced prostate cancers. This review explores both preclinical and clinical findings to date. In summary, tasquinimod has been shown to demonstrate a potent in vitro and in vivo anticancer action and completed early phase clinical trials have demonstrated good drug tolerance and prolonged progression-free survival. Although Phase III clinical trials are on-going, the findings to date highlight the promise of this drug in the treatment of advanced prostate cancer.

Current and emerging treatments in the management of castration-resistant prostate cancer

Historically, patients diagnosed with castration-resistant prostate cancer (CRPC) have had poor survival rates. In recent years there have been significant advances in the treatment of CRPC. In addition to cytotoxic chemotherapy, treating physicians and their patients now have the option of several new agents that target not only androgen- and cytotoxic-mediated pathways, but also the patient's own immune system. In this review, we discuss the existing US FDA-approved therapies, a wide range of experimental treatments that are currently in development, and also palliative options for patients with symptoms secondary to metastatic disease. We also discuss the progression-free survival, overall survival, PSA levels and other end points used in clinical trials in order to evaluate and compare novel therapeutic options for CRPC. Currently, docetaxel and sipuleucel-T are the first line treatment options for patients with CRPC; approved second-line treatments for first line treatment failure are limited to cabazitaxel and abiraterone acetate. Recently, a few experimental agents, MDV3100 and radium-223, have demonstrated efficacy in improving overall survival in patients who had previously failed chemotherapy. These agents, and possibly others introduced in this review, are positioned to change the treatment landscape for CRPC.

Targeting angiogenesis as a promising modality for the treatment of prostate cancer

Antiangiogenic therapy has been successful for the treatment of solid tumors. Several strategies have been used to target angiogenesis in prostate cancer. These strategies include blocking proangiogenic factors via monoclonal antibodies or small molecule inhibitors targeting downstream signaling effector pathways, or using agents with immune-modulatory effects. This review examines the general concepts of tumor angiogenesis and the key clinical trials that have used these agents and other novel biologics in prostate cancer. Targeting angiogenesis is still a promising treatment strategy in prostate cancer with a rational trial design and combination approach.

Tasquinimod Is an Allosteric Modulator of HDAC4 survival signaling within the compromised cancer microenvironment

Tasquinimod is an orally active antiangiogenic drug that is currently in phase III clinical trials for the treatment of castration-resistant prostate cancer. However, the target of this drug has remained unclear. In this study, we applied diverse strategies to identify the histone deacetylase HDAC4 as a target for the antiangiogenic activity of tasquinimod. Our comprehensive analysis revealed allosteric binding (Kd 10-30 nmol/L) to the regulatory Zn(2+) binding domain of HDAC4 that locks the protein in a conformation preventing HDAC4/N-CoR/HDAC3 complex formation. This binding inhibited colocalization of N-CoR/HDAC3, thereby inhibiting deacetylation of histones and HDAC4 client transcription factors, such as HIF-1α, which are bound at promoter/enhancers where epigenetic reprogramming is required for cancer cell survival and angiogenic response. Through this mechanism, tasquinimod is effective as a monotherapeutic agent against human prostate, breast, bladder, and colon tumor xenografts, where its efficacy could be further enhanced in combination with a targeted thapsigargin prodrug (G202) that selectively kills tumor endothelial cells. Together, our findings define a mechanism of action of tasquinimod and offer a perspective on how its clinical activity might be leveraged in combination with other drugs that target the tumor microenvironment. Cancer Res; 73(4); 1386-99. ©2012 AACR.

Progress in emerging therapies for advanced prostate cancer

The landscape of prostate cancer treatment is rapidly changing as extensive research into potential therapies yields new options. In this article, the literature is reviewed to identify emerging therapies for advanced prostate cancer. Emphasis is placed on agents that have been approved in the United States of America (USA) and the European Union, or that have reached phase III clinical studies. Several new therapies have been approved in recent years across different stages of the natural history of the disease. Degarelix, a luteinizing hormone-releasing hormone antagonist, has been approved for reducing testosterone to castrate levels in hormone-sensitive disease. No new agents have been approved for use in combination with docetaxel chemotherapy, the current standard of care for metastatic castration-resistant prostate cancer. One immunotherapy, sipuleucel-T, has been approved (USA only) in the pre-docetaxel setting. Cabazitaxel, a next-generation taxane, and abiraterone acetate, an inhibitor of androgen biosynthesis, have both been approved as second-line agents following chemotherapy. Enzalutamide (MDV3100), an androgen receptor antagonist, has been shown to increase overall survival in the post-chemotherapy setting in metastatic disease. Denosumab, an antibody-based bone-targeted agent, has been approved for the prevention of skeletal-related events in patients with bone metastases. Radium-223 chloride, an α-emitting radiopharmaceutical, is likely to gain approval soon following promising results in a phase III trial. Clinical studies involving other promising agents are ongoing. The emergence of these therapies adds to the growing armamentarium against prostate cancer.

Inhibition of metastasis in a castration resistant prostate cancer model by the quinoline-3-carboxamide tasquinimod (ABR-215050)

BACKGROUND

Tasquinimod (ABR-215050) is an orally active quinoline-3-carboxamide analog that has completed phase II clinical trial in patients with castration resistant prostate cancer, showing promising inhibiting effects on the occurrence of metastasis and delayed disease progression. Its mechanism of action is not fully elucidated, but previous studies show anti-angiogenic effects and strong interaction with the S100A9 protein.

METHODS

This study was performed to evaluate if tasquinimod inhibits prostate cancer metastasis, by using both orthotopic and intratibial xenograft models. Animals were treated with tasquinimod, and tumor growth characteristics as well as molecular markers for metastasis and angiogenesis were analyzed.

RESULTS

The results show that formation of lung and lymph node metastases from orthotopic castration resistant prostate tumors was inhibited by tasquinimod treatment. Importantly, establishment of tumors in the bone after intratibial implantation was suppressed by tasquinimod. In addition, establishment and growth of subcutaneous tumors were affected. Both in primary tumors and serum from treated mice an upregulation of thrombospondin 1 was observed. Further, downregulation of the hypoxia driven genes VEGF, CXCR4, and LOX was detected in the primary tasquinimod-treated tumors and decreased expression of chemotactic ligand SDF-1 was demonstrated in the lungs. Thus, these molecular changes could contribute to the anti-angiogenic and anti-metastatic effects of tasquinimod.

CONCLUSIONS

In conclusion, this study and clinical data show that tasquinimod interferes with the metastatic process, presumably by inhibition of tumor establishment. Therefore, tasquinimod is an interesting treatment option for patients with prostate cancer prone to metastasis.

Tasquinimod prevents the angiogenic rebound induced by fractionated radiation resulting in an enhanced therapeutic response of prostate cancer xenografts

BACKGROUND

Tasquinimod is a novel inhibitor of tumor angiogenesis which enhances therapeutic efficacy when combined with androgen ablation and/or taxane-based chemotherapies in pre-clinical prostate cancer models. It has entered registration Phase III evaluation for the treatment of castration resistant prostate cancer. Since tasquinimod suppresses the angiogenic switch induced by tumor hypoxia as prostate cancers outgrow their blood supply, this raises the issue of whether tasquinimod also suppresses the angiogenic rebound induced by fractionated radiation thereby enhancing therapeutic response to fractionated radiation.

METHODS

Human endothelial and prostate cancer cells in culture and human prostate cancer xenografts growing in castrated male nude mice were evaluated for their response to radiation alone and in combination with tasquinimod.

RESULTS

At clinically relevant drug levels, tasquinimod significantly (P < 0.05) enhances anti-cancer efficacy of fractionated radiation with optimal timing for initiating daily tasquinimod treatment being after completion of the fractionated radiation.

CONCLUSIONS

Based upon cell culture studies and tumor tissue oxygenation (i.e., pO(2)), tumor vascular volume, and tumor blood vessel density measurements, the mechanism for such enhancement and optimal timing involves tasquinimod's ability to prevent the angiogenic rebound induced by fractionated radiation.

Antiangiogenic and anticancer molecules in cartilage

Cartilage is one of the very few naturally occurring avascular tissues where lack of angiogenesis is the guiding principle for its structure and function. This has attracted investigators who have sought to understand the biochemical basis for its avascular nature, hypothesising that it could be used in designing therapies for treating cancer and related malignancies in humans through antiangiogenic applications. Cartilage encompasses primarily a specialised extracellular matrix synthesised by chondrocytes that is both complex and unique as a result of the myriad molecules of which it is composed. Of these components, a few such as thrombospondin-1, chondromodulin-1, the type XVIII-derived endostatin, SPARC (secreted protein acidic and rich in cysteine) and the type II collagen-derived N-terminal propeptide (PIIBNP) have demonstrated antiangiogenic or antitumour properties in vitro and in vivo preclinical trials that involve several complicated mechanisms that are not completely understood. Thrombospondin-1, endostatin and the shark-cartilage-derived Neovastat preparation have also been investigated in human clinical trials to treat several different kinds of cancers, where, despite the tremendous success seen in preclinical trials, these molecules are yet to show success as anticancer agents. This review summarises the current state-of-the-art antiangiogenic characterisation of these molecules, highlights their most promising aspects and evaluates the future of these molecules in antiangiogenic applications.

S100A9 interaction with TLR4 promotes tumor growth

By breeding TRAMP mice with S100A9 knock-out (S100A9^−/−) animals and scoring the appearance of palpable tumors we observed a delayed tumor growth in animals devoid of S100A9 expression. CD11b⁺ S100A9 expressing cells were not observed in normal prostate tissue from control C57BL/6 mice but were readily detected in TRAMP prostate tumors. Also, S100A9 expression was observed in association with CD68⁺ macrophages in biopsies from human prostate tumors. Delayed growth of TRAMP tumors was also observed in mice lacking the S100A9 ligand TLR4. In the EL-4 lymphoma model tumor growth inhibition was observed in S100A9^−/− and TLR4^−/−, but not in RAGE^−/− animals lacking an alternative S100A9 receptor. When expression of immune-regulating genes was analyzed using RT-PCR the only common change observed in mice lacking S100A9 and TLR4 was a down-regulation of TGFβ expression in splenic CD11b⁺ cells. Lastly, treatment of mice with a small molecule (ABR-215050) that inhibits S100A9 binding to TLR4 inhibited EL4 tumor growth. Thus, S100A9 and TLR4 appear to be involved in promoting tumor growth in two different tumor models and pharmacological inhibition of S100A9-TLR4 interactions is a novel and promising target for anti-tumor therapies.

Emerging treatment options for patients with castration-resistant prostate cancer

BACKGROUND

Most prostate cancer-related deaths occur in patients with castration-resistant prostate cancer (CRPC). Recent preclinical and clinical studies have identified intracellular signaling pathways and changes in the tumor and bone microenvironment as potential key drivers of CRPC. This increased understanding of mechanisms associated with CRPC has driven the development of numerous new agents, many of which are poised to alter the current CRPC treatment landscape.

METHODS

A review of literature was conducted to identify ongoing and planned phase III studies of novel agents to treat CRPC.

RESULTS

Multiple studies were identified, including novel androgen biosynthesis inhibitors (abiraterone, TAK-700), androgen-receptor inhibitors (MDV3100), angiogenesis inhibitors (aflibercept, tasquinimod), endothelin antagonists (zibotentan, atrasentan), a Src tyrosine kinase inhibitor (dasatinib), a novel radiotherapy (radium-223), and new immunotherapies (ipilimumab and ProstVac). In addition, both sipuleucel-T (an immunotherapy) and cabazitaxel (third-generation taxane) and the RANK-L inhibitor, denosumab, have recently been approved by the US Food and Drug Administration.

CONCLUSIONS

Various combinations of these agents could theoretically be used to treat future patients with CRPC by targeting multiple signaling pathways as well as aspects of the tumor and bone microenvironments. Additional research will be needed to understand how to best use these agents and individualize care to optimize CRPC patient outcomes.

Novel therapeutics for the management of castration-resistant prostate cancer (CRPC)

Androgen-deprivation therapy is the initial treatment for metastatic prostate cancer. Although highly effective, all men who live long enough will eventually experience disease progression and develop castration resistance. Patients who have castration-resistant prostate cancer (CRPC) have a median survival of ≈1-3 years. When evaluating novel therapies for CRPC, one must consider the endpoints measured for determination of response. We will discuss PSA, circulating tumour cells, progression-free survival, overall survival, and other endpoints used in clinical trials. Docetaxel and sipuleucel-T are currently the preferred first-line treatment options for patients with CRPC; cabazitaxel is a new option for patients after docetaxel failure. Patients with CRPC historically have very poor survival, underscoring the unmet need for novel therapeutics. Although many agents appear promising, well-designed randomized phase III trials are necessary to establish their impact on survival and health-related quality of life. Promising new therapies include hormonal agents, such as abiraterone and MDV3100, as well as other novel immunotherapeutics and anti-prostate-specific membrane antigen therapies. In the future, we anticipate therapies tailored to individual patients' malignancies using various molecular analyses.

Phase II randomized, double-blind, placebo-controlled study of tasquinimod in men with minimally symptomatic metastatic castrate-resistant prostate cancer

PURPOSE

The activity of the novel antitumor agent tasquinimod (TASQ) with S100A9 as a molecular target was investigated in men with metastatic castration-resistant prostate cancer (CRPC) and minimal symptoms.

PATIENTS AND METHODS

We conducted a randomized, double-blind, placebo-controlled phase II trial in men assigned (at a ratio of two to one) to either oral once-daily TASQ 0.25 mg/d escalating to 1.0 mg/d over 4 weeks or placebo. The primary end point was the proportion of patients without disease progression at 6 months, defined by Response Evaluation Criteria in Solid Tumors Group, Prostate Cancer Working Group (PCWG2), or pain criteria, excluding prostate-specific antigen.

RESULTS

Two hundred one men (134 assigned to TASQ; 67 to placebo) were evaluable, and baseline characteristics were well balanced. Six-month progression-free proportions for TASQ and placebo groups were 69% and 37%, respectively (P < .001), and median progression-free survival (PFS) was 7.6 versus 3.3 months (P = .0042). In PCWG2 CRPC clinical subgroups, PFS in months was as follows: nodal metastases, 6.1 versus 3.1; bone metastases, 8.8 versus 3.4; and visceral metastases, 6.0 versus 3.0 for patients receiving TASQ versus placebo, respectively. Bone alkaline phosphatase levels were stabilized in the TASQ group, whereas the impact on PSA kinetics was less pronounced. Adverse events (AEs) occurring more frequently in the TASQ arm included GI disorders, fatigue, musculoskeletal pains, and elevations of pancreatic and inflammatory biomarkers. Grade 3 to 4 AEs, including asymptomatic elevations of laboratory parameters, were reported in 40% of patients receiving TASQ versus 10% receiving placebo; deep vein thrombosis (4% v 0%) was more common in the TASQ arm.

CONCLUSION

TASQ significantly slowed progression and improved PFS in patients with metastatic CRPC with an acceptable AE profile.

A phase II study of sorafenib in combination with bicalutamide in patients with chemotherapy-naive castration resistant prostate cancer

PURPOSE

The objective of this trial was to evaluate the clinical effects of sorafenib, a multi-targeted kinase inhibitor, in combination with androgen receptor blockade in patients with castration-resistant prostate cancer.

METHODS

This was a multicenter, two-stage, phase 2 trial. Eligible patients had rising PSA, minimal symptoms and were chemotherapy-naïve. Sorafenib 400 mg twice daily was administered with bicalutamide 50 mg once daily on a 28-day cycle. The primary endpoint was PSA response (≥ 50% decline) or stable disease ≥ 6 months.

RESULTS

39 patients were enrolled including eight without clinical evidence of metastases. Eighteen (47%) patients have had either a PSA response or stable disease ≥ 6 months. PSA declines of ≥ 50% occurred in 12 (32%) of 38 assessable patients, including seven of 27 patients (26%) with prior anti-androgen use. Median time to treatment failure was 5.5 months (95%CI = 4.8.1-8.3). Grade ≥ 3 adverse events included fatigue, skin rash, and hand-foot syndrome.

CONCLUSIONS

PSA declines and stable disease were observed with a combination of sorafenib and bicalutamide including in patients previously progressing on bicalutamide. Strategies to combine multi-targeted kinase inhibitors with hormonal therapies warrant further study in patients with CRPC.

New strategies for medical management of castration-resistant prostate cancer

Although advanced prostate cancer patients respond very well to front-line androgen deprivation, failure to hormonal therapy most often occurs after a median time of 18-24 months. The care of castration-resistant prostate cancer (CRPC) has significantly evolved over the past decade, with the onset of first-line therapy with docetaxel. Although numerous therapy schedules have been investigated alongside docetaxel, in either first-line or salvage therapy, results were dismal. However, CRPC chemotherapy is currently evolving, with, on the one hand, new agents targeting androgen metabolism and, on the other hand, significant progress in chemotherapy drugs, particularly for second-line therapy. The aim of the present review is to describe the current treatments for CRPC chemotherapy alongside their challengers that might shortly become new standards. In this article, we discuss the most recent data from clinical trials to provide the reader with a comprehensive, state-of-the-art overview of CRPC chemotherapy and hormonal therapy.

The long and winding road for the development of tasquinimod as an oral second-generation quinoline-3-carboxamide antiangiogenic drug for the treatment of prostate cancer

IMPORTANCE OF THE FIELD

Prostate cancer is the mostly commonly diagnosed non-skin cancer in males. The culmination of the last 70 years of clinical drug development has documented that androgen ablation plus taxane-based systemic chemotherapy enhances survival, but is not curative, in metastatic prostate cancer. To effect curative therapy, additional drugs must be developed that enhance the response when combined with androgen ablation/taxane therapy.

AREAS COVERED IN THIS REVIEW

The history of the discovery and development of tasquinimod as a second-generation oral quinoline-3-carboxamide analogue for prostate cancer will be presented.

WHAT THE READER WILL GAIN

The mechanism for such anticancer efficacy is via tasquinimod's ability to inhibit the 'angiogenic switch' within cancer sites required for their continuous lethal growth.

TAKE HOME MESSAGE

Tasquinimod is a novel inhibitor of tumor angiogenesis that enhances the therapeutic anticancer response when combined with other standard-of-care modalities (radiation, androgen ablation, and/or taxane-based chemotherapies) in experimental animal models, but does not inhibit normal wound healing. It has successfully completed clinical Phase II testing in humans and will shortly enter registration Phase III evaluation for the treatment of metastatic prostate cancer.