Interleukin (IL)-1β Receptor Type II (Gene Therapy), IL-1β Gene,Nitric Oxide Synthase (NOS), Cyclo-Oxygenase (COX)-2, Tumour Necrosis Factor (TNF)-α Convertase,IL-17, Superoxide Dismutase (SOD), Differential Display of Novel Genes Expressed in Human Osteoarthritis-Affected Cartilage,Human Arthritis-Affected Cartilage Proteases

Introduction: Neuropathic pain and chronic inflammatory pain are large unmet medical needs. Over the past two decades, numerous ’pain targets’ have been identified for analgesic drug discovery. Despite promising results in rodent pain models, many compounds modulating such targets lacked efficacy in clinical trials. An exception is oral EMA401, a small-molecule angiotensin II type 2 receptor (AT₂R) antagonist.

Areas covered: Herein, angiotensin II/AT₂R signaling-induced hyperexcitability and abnormal sprouting of cultured dorsal root ganglion neurons, together with radioligand binding, pharmacokinetics, analgesic efficacy and mode of action of small-molecule AT₂R antagonists in rodent models of peripheral neuropathic and chronic inflammatory pain, are reviewed. The findings of a successful Phase IIa clinical trial of EMA401 in patients with neuropathic pain are presented in brief.

Expert opinion: The functional importance of angiotensin II/AT₂R signaling has remained enigmatic for decades, and there are no clinically available medications that target the AT₂R. However, on the basis of preclinical findings and recent clinical trial data showing that the peripherally restricted, small-molecule AT₂R antagonist, EMA401, successfully alleviated neuropathic pain in a Phase II clinical trial, the AT₂R is receiving considerable attention as a new therapeutic target with human validation for the relief of peripheral neuropathic and chronic inflammatory pain conditions.     

Emerging drugs for diabetic peripheral neuropathy and neuropathic pain

Introduction: Diabetic sensorimotor polyneuropathy (DSPN) is a common complication of diabetes.

Areas covered: In this review, the authors discuss the emerging drugs for DSPN, which aim either at improving alleviation of neuropathic pain or addressing the putative mechanisms underlying diabetic neuropathy.

Expert Opinion: Current treatment does not address the sensory deficits and pathogenesis underlying DSPN, so there is an unmet need for treatment options targeting the natural history of the condition. Some of these pathogenetic therapies have demonstrated clinically relevant improvements in neuropathic endpoints in recent randomised controlled trials. Since any effective analgesic monotherapy is known to induce a clinically meaningful response in only some 50% of the patients, there remains a substantial unmet need in patients with neuropathic pain. Advanced knowledge in the neurobiology of neuropathic pain and improved phenotypic profiling have led to a burst of research into novel pharmaceutical approaches. An array of promising molecular entities have reached the clinical stage of development, which should improve our therapeutic armamentarium in the fight against DSPN and neuropathic pain in the foreseeable future.     

How do we choose the appropriate animal model for antiseizure therapy development?

ABSTRACT

Introduction: Epilepsy affects over 65 million people worldwide, and despite the numerous therapies that are currently available for the symptomatic management of chronic seizures, a substantial proportion of the population has not achieved adequate seizure control. Developing more effective and better-tolerated therapies will benefit patients worldwide.

Areas covered: This article will discuss the relevant preclinical models that have been instrumental to the development of over 20 antiseizure drugs (ASDs) currently on the market today. While there have been meaningful therapies already developed over the last several decades, this article will highlight remaining areas of unmet medical need. Innovative models of pharmacoresistant epilepsy may advance therapies for patients who currently do not attain sufficient seizure control in the absence of adverse effects. There also remains a need to identify improved therapies for special patient populations, including the very young and old.

Expert opinion: ASD development will still find utility in the established models that have been instrumental to the identification of impactful therapies. However, there should now be greater emphasis to implement those models in young and aged rodents to advance novel therapies for patients who are still in need of better tolerated or more effective therapies, such as pediatric and elderly patients.     

Combined oral prolonged-release oxycodone and naloxone in opioid-induced bowel dysfunction: review of efficacy and safety data in the treatment of patients experiencing chronic pain

Importance of the field: Despite proven analgesic efficacy, opioid use is associated with frequently dose-limiting bowel dysfunction that seriously impacts patients' quality of life (QoL). Agents used at present to manage opioid-induced constipation do not address the underlying opioid receptor-mediated cause of bowel dysfunction and are often ineffective. There is, therefore, a significant need for more effective treatment options. The combination of the strong opioid oxycodone and the opioid antagonist naloxone has the potential to prevent opioid-induced bowel dysfunction (OIBD) while maintaining analgesic efficacy.

Objective: To review the safety and efficacy of oral prolonged-release (PR) oxycodone/naloxone in the treatment of patients experiencing chronic pain.

Areas covered in this review: A MEDLINE search was done (January 2002 – July 2009) for available literature for prolonged release oxycodone and naloxone in different patient groups. Results were limited to English-language and clinical trials. Data were also obtained from congress materials.

What knowledge the reader will gain: Unmet needs of opioid pain treatment in terms of OIBD, reduced QoL and low treatment compliance, leading to reduced efficacy. A data overview demonstrates the efficacy and tolerability of PR oxycodone/naloxone in the management of severe chronic pain without the burden of severe gastrointestinal adverse events. The combined formulation of a highly effective opioid and an antagonist that acts locally to reduce gastrointestinal side effects is expected to simplify pain management.

Take home message: The combination of PR oxycodone/naloxone offers the potential of maintaining normal bowel function in patients requiring opioid therapy – it is a strong analgesic that is well tolerated.     

Chronic orofacial pain animal models - progress and challenges

ABSTRACT

Introduction: Chronic orofacial pain is one of the most common pain conditions experienced by adults. Animal models are often selected as the most useful scientific methodology to explore the pathophysiology of the disorders that cause this disabling pain to facilitate the development of new treatments. The creation of new models or the improvement of existing ones is essential for finding new ways to approach the complex neurobiology of this type of pain.

Areas covered: The authors describe and discuss a variety of animal models used in chronic orofacial pain (COFP). Furthermore, they examine in detail the mechanisms of action involved in orofacial neuropathic pain and orofacial inflammatory pain.

Expert opinion: The use of animal models has several advantages in chronic orofacial pain drug discovery. Choosing an animal model that most closely represents the human disease helps to increase the chances of finding effective new therapies and is key to the successful translation of preclinical research to clinical practice. Models using genetically modified animals seem promising but have not yet been fully developed for use in chronic orofacial pain research. Although animal models have provided significant advances in the pharmacological treatment of orofacial pain, several barriers still need to be overcome for better treatment options.     

The preclinical discovery and development of ezogabine for the treatment of epilepsy

Introduction: The weak anticonvulsant activity of the analgesic flupirtine led to the creation of ezogabine; an analogue which demonstrated both stronger antiepileptic activity and weaker analgesic effects. It's use as an anticonvulsant has been particularly effective in treating patients who have therapy-resistant epilepsy. Ezogabine binds to the KCNQ potassium channel, thereby decreasing the membrane potential threshold for its activation and increasing the probability of its maximum opening.

Areas covered: This drug discovery case history provides an overview of the history of the anticonvulsant, ezogabine, and presents relevant information pertaining to its discovery and preclinical development. The article helps explain the methods of discovery through the explanation of ezogabine's mechanism of action. Further, the authors also highlight the drugs clinical development and its postlaunch developments.

Expert opinion: More intense investment in research on the molecular mechanism of action early in the preclinical development of a drug could allow for the more suitable planning of preclinical studies and for the early discovery of specific, but important drug toxicities. This investment would make transitioning from the preclinical to the clinical phase easier and could result in better planning for what will be more productive clinical studies.     

Expert opinion on emerging drugs: chronic low back pain

Introduction: It is difficult to overestimate the personal and socioeconomic impact of chronic low back pain (CLBP). It is the leading cause of years lost to disability and poses the highest economic toll among chronic illnesses. Despite the strong need for extensive research efforts, few drugs have consistently demonstrated effectiveness for this condition.

Areas covered: In this review, the epidemiology, rationale for mechanism-based treatment, competitive environment and market trends, and the preclinical and clinical evidence supporting over 15 different classes of analgesic medications studied for CLBP or related pain conditions are discussed. Treatments are divided by drug category, type of CLBP they are likely to treat (e.g., neuropathic or mechanical), and whether they are new formulations of existing treatments, new indications for existing treatments or represent novel mechanisms of action. Databases searched included MEDLINE, Embase, Pharmaprojects and various clinical trial registries.

Expert opinion: Many barriers exist for the development of medications for CLBP including difficulties in identifying pathophysiological mechanisms, biologic resiliency secondary to multiple concurrent pain pathways and off-target and sometimes serious side effects. Nevertheless, the volume and diversity of novel molecular entities has continued to surge and includes possible disease-modifying therapies such as gene and stem cell therapy.     

FMS-like tyrosine kinase 3 inhibitors: a patent review

Introduction: Flt3 (FMS-like tyrosine kinase 3) has been presented as a target for novel anti-leukemic drugs because Flt3 mutations have been observed in acute myeloid leukemia (AML) cells. Due to both the poor efficacy and high toxicity of current standard AML therapies, there is an unmet need for new, improved therapies. Flt3 inhibitors have great potential to address this with mutated Flt3.

Areas covered: This paper provides a comprehensive review of the Flt3 inhibitor patents currently available. Information from original research articles in peer-reviewed journals and current clinical developments from several resources is also described.

Expert opinion: Our understanding of Flt3 inhibitors has been increased by findings from recent preclinical and clinical trials. Some Flt3 inhibitors show good efficacy in AML patients, but relapse and resistance to these inhibitors are still unavoidable. To address these problems, structurally diverse inhibitors, which exhibit inhibitory activities against both wild type and mutated Flt3, should be explored.     

Chronic pain management issues in the primary care setting and the utility of long-acting opioids

Importance of the field: Chronic/persistent pain – a highly prevalent condition that places a substantial burden on patients in terms of personal suffering, reduced productivity and health care costs – remains inadequately treated in many patients. The purpose of this review is to provide an overview and evaluate the burden and undertreatment of chronic/persistent pain, considerations for choosing an analgesic and the utility of long-acting opioids.

Areas covered in this review: A PubMed search was conducted to identify randomized, placebo-controlled trials evaluating the efficacy and safety of long-acting opioids in chronic pain conditions. The following search terms were used: long-acting opioids, extended-release opioids, controlled-release opioids, sustained-release opioids, and transdermal opioids. The search was limited to randomized, controlled trials published within the last 10 years (1998 – 2008). Studies meeting the following criteria were excluded from review: those focused on a neuropathic pain condition or specific patient subpopulations (e.g., opioid-experienced patients); those conducted outside the USA; and those evaluating a long-acting opioid that is not on the US market at present.

What the reader will gain: The reader will first develop a better understanding of the individual and societal ramifications of undertreated chronic pain. Then, a critical review of safety and efficacy data from well-controlled randomized studies will help readers understand the choices and variables that should be considered when selecting appropriate treatments for patients with chronic pain.

Take home message: Successful management of chronic/persistent pain should be individually tailored to each patient, taking into account his or her pain intensity and duration, disease state, tolerance of adverse events and risk of medication abuse or diversion. The literature supports the efficacy and safety of a number of long-acting opioids for the treatment of moderate to severe chronic pain, demonstrating sustained improvements in pain intensity and pain-related sleep disturbances with these agents.     

Emerging therapies in metastatic bone pain

Introduction: Current treatment for metastatic bone pain is mainly palliative. Recent insights into the molecular mechanisms involved in bone metastases have led to the identification of promising therapeutic targets. This review offers an update of preclinical and clinical data on new drugs for metastatic bone pain.

Areas covered: Biphosphonates are the gold standard of bone-targeted therapy in bone metastases, for their anti-resorptive and analgesic effects. New drugs aim at breaking the ‘vicious cycle’ of bone metastatic disease, due to the bidirectional interaction between cancer cells and bone microenvironment. Osteoprotegerin, RANK/RANKL interaction, cathepsin K, the Wnt/beta-catenin pathway and sclerostin are emerging targets for modulation of cancer-induced bone desorption. Other promising targets are those expressed in cancer cells that metastasize to bone, including Src, nerve growth factor, endothelin A, TGF-beta and CXCR4. Interesting therapeutic options include targets on nociceptors that innervate the bone, such as TPRV1, Trk and cannabinoid receptors.

Expert opinion: Emerging therapies promise, in the next 10 years, a significant expansion in the array of therapeutic options for bone metastases. Most of these drugs are still in an early phase of development. Further clinical trials are needed to support the evidence of their efficacy and tolerability profile.     

Extended-release formulations of tramadol in the treatment of chronic pain

Introduction: Tramadol is a centrally acting analgesic available throughout the world. Its dual opioid and non-opioid mechanisms of action, favorable efficacy and safety clinical profiles and non-controlled regulatory status in most markets contribute to its widespread use. A drawback of the immediate-release formulation of tramadol (four-times-a-day dosing) might be addressed by an extended-release formulation. Extended-release formulations also can offer advantages in the management of chronic pain: convenience, reduced pill burden (possibly leading to improved compliance) and the attenuation of peaks and troughs in serum concentration (possibly leading to reduced adverse effects).

Areas covered: The authors review tramadol's mechanisms of action and the clinical literature regarding the use of tramadol extended-release formulations for the management of conditions involving chronic pain, such as neuropathic pain syndromes, osteoarthritis and cancer pain.

Expert opinion: Based on the literature cited, extended-release formulations of tramadol seem to offer a rational and important addition to the analgesic armamentarium. As is true for all such options, the benefits and risks must be assessed for each patient.     

Emerging topical treatments for psoriasis

Introduction: Psoriasis is an immune-mediated chronic inflammatory skin disease which classically presents as erythematous, scaly plaques affecting extensor surfaces of the limbs, scalp and trunk. Approximately 80% of patients have a mild-to-moderate form routinely treated with topical medications, whereas phototherapy, systemic and biological therapies are typically reserved for treatment of moderate-to-severe psoriasis.

Areas covered: The major advances in psoriasis therapy in the past 15 years have been in new immunomodulatory and biological molecules, with a significant unmet need to have new, efficient and safe topical treatment options for the large percentage of patients for whom systemic therapy is not indicated. The available topical therapies (corticosteroids and vitamin D3 analogs) have remained relatively unchanged over the past several decades. This article reviews emerging topical drugs and formulations currently under evaluation in clinical trials.

Expert opinion: The time is right for a revolution in our topical therapy armamentarium. It has lagged significantly behind the systemic biological evolution of new drug development. Our large psoriasis population with mild-to-moderate psoriasis certainly deserves potent but safe and innovative topical agents with a new mode of action as well as with long-lasting clinical efficacy.     

Targeting 5-lipoxygenase-activating protein in asthma and chronic obstructive pulmonary disease

Introduction: In asthma and chronic obstructive pulmonary disease (COPD), there is an unmet therapeutic need for the anti-inflammatory therapies, and the identification of therapeutic targets and potent corresponding therapies is necessary. Although inhaled corticosteroids and leukotriene modifiers are most effective in asthma they are still not always capable of appropriately controlling the disease. In COPD, the therapeutic gap is even larger because inhaled corticosteroids and other anti-inflammatory therapies are not beneficial in all disease subsets.

Areas covered: The role of the 5-lipoxygenase-activating protein (FLAP) in generating proinflammatory molecules such as leukotrienes is discussed, highlighting, in particular, its potential as a therapeutic target in asthma and COPD. The preclinical data on FLAP inhibitors are discussed. The clinical data on the FLAP inhibitors investigated so far for these diseases are analyzed.

Expert opinion: FLAP inhibitors have emerged during the past decade as a promising therapeutic class in asthma and COPD, but there exists only a limited amount of data supporting their efficacy in these diseases. This might be due to the fact that the development of some of the molecules discussed was abandoned. Such therapies might be of particular interest in COPD and in asthma-COPD overlap syndrome.     

Co-crystal of tramadol-celecoxib: preclinical and clinical evaluation of a novel analgesic

Introduction: Pain management is a major unmet need due to the suboptimal efficacy and undesirable side effects of current analgesics. Multimodal therapies recruiting complementary mechanisms of action may help address this. Co-crystals incorporating two active pharmaceutical ingredients (APIs) constitute an innovative approach to multimodal therapy, particularly if modification of the physicochemical properties of constituent APIs can be translated into clinical benefits.

Areas covered: The preclinical and clinical profiles of Co-Crystal of Tramadol-Celecoxib (CTC), a novel API–API co-crystal (1:1 molecular ratio of rac-tramadol.hydrochloride and celecoxib) are described.

Expert opinion: CTC may provide a relevant addition to pain therapy due to its: i) unique co-crystal structure conferring differentiated intrinsic dissolution profiles on constituent APIs, ii) modified clinical pharmacokinetics (slower absorption of tramadol and faster absorption of celecoxib) compared with commercially available single-entity reference products (in agreement with modified dissolution rates), iii) superior benefit–risk ratio compared with reference products (suggested by preclinical synergistic antinociceptive effects, without potentiation of adverse effects), and iv) efficacy in a phase 2 trial of moderate to severe pain following extraction of ≥2 impacted third molars requiring bone removal, where CTC doses containing low doses of APIs exerted a significant effect. Phase 3 studies are currently ongoing.     

Advances in preclinical approaches to Chagas disease drug discovery

ABSTRACT

Introduction: Chagas disease affects 8–10 million people worldwide, mainly in Latin America. The current therapy for Chagas disease is limited to nifurtimox and benznidazole, which are effective in treating only the acute phase of the disease but with severe side effects. Therefore, there is an unmet need for new drugs and for the exploration of innovative approaches which may lead to the discovery of new effective and safe drugs for its treatment.

Areas covered: The authors report and discuss recent approaches including structure-based design that have led to the discovery of new promising small molecule candidates for Chagas disease which affect prime targets that intervene in the sterol pathway of T. cruzi. Other trypanosome targets, phenotypic screening, the use of artificial intelligence and the challenges with Chagas disease drug discovery are also discussed.

Expert opinion: The application of recent scientific innovations to the field of Chagas disease have led to the discovery of new promising drug candidates for Chagas disease. Phenotypic screening brought new hits and opportunities for drug discovery. Artificial intelligence also has the potential to accelerate drug discovery in Chagas disease and further research into this is warranted.     

An overview of early drug development for endometriosis

Introduction: Endometriosis is an estrogen-dependent chronic disease of women of fertile age requiring chronic therapy. Although available drugs have good efficacy and safety profiles, some patients experience partial or no improvement of pain with conventional treatment and recurrence of symptoms after discontinuation of the therapies. For these reasons, many new compounds are currently under investigation for the treatment of endometriosis.

Areas covered: This review offers the reader a complete and updated overview on emerging therapies for the treatment of endometriosis. The authors describe, in detail, the laboratory and clinical studies on these therapies and highlight the potential advantages and limitations associated with the administration of these new agents.

Expert opinion: Gonadotropin-releasing hormone antagonists are the most intriguing emerging agents for the treatment of patients with endometriosis. It should be noted that while there are a number of drugs under investigation, a large majority of these new compounds have only been investigated in laboratory studies with more extensive research required to better elucidate their efficacy and safety profiles.     

Learning from the failures of drug discovery in B-cell non-Hodgkin lymphomas and perspectives for the future: chronic lymphocytic leukemia and diffuse large B-cell lymphoma as two ends of a spectrum in drug development

Introduction: Despite substantial recent advances, there is still an unmet need for better therapies in B-cell non Hodgkin lymphomas (B-NHL), especially in relapsed or refractory disease. Many novel targeted drugs have been developed based on a better molecular understanding of B-NHL.

Areas covered: This article focuses on chronic lymphocytic leukemia (CLL) as a representative for indolent lymphomas and paradigmatic for the tremendous progress in treating B-NHL on the one hand and diffuse large B-cell lymphoma (DLBCL) as a representative for aggressive lymphomas and paradigmatic for many unsolved problems in lymphoma treatment or the other hand. We highlight salient points in current therapies targeting genetic, epigenetic, immunological and microenvironmental alterations. Possible reasons for drug failure in clinical trials like tumor heterogeneity, clonal evolution and drug resistance mechanisms are discussed. Based thereon, some perspectives for further drug discovery are given.

Expert opinion: In view of the pathogenetic complexity of lymphomas, therapies targeting exclusively a single alteration may fail because resistance mechanisms are present either initially or evolve during treatment. Therefore, future therapies in B-NHL may have to target the greatest possible number of genetic, immunological or epigenetic alterations still allowing tolerability and to monitor these alterations during therapy.     

Dronabinol and chronic pain: importance of mechanistic considerations

Introduction: Although medicinal cannabis has been used for many centuries, the therapeutic potential of delta-9-tetrahydrocannabinol (Δ9-THC; international non-proprietary name = dronabinol) in current pain management remains unclear. Several pharmaceutical products with defined natural or synthesized Δ9-THC content have been developed, resulting in increasing numbers of clinical trials investigating the analgesic efficacy of dronabinol in various pain conditions. Different underlying pain mechanisms, including sensitization of nociceptive sensory pathways and alterations in cognitive and autonomic processing, might explain the varying analgesic effects of dronabinol in chronic pain states.

Areas covered: The pharmacokinetics, pharmacodynamics and mechanisms of action of products with a defined dronabinol content are summarized. Additionally, randomized clinical trials investigating the analgesic efficacy of pharmaceutical cannabis based products are reviewed for the treatment of chronic nonmalignant pain.

Expert opinion: We suggest a mechanism-based approach beyond measurement of subjective pain relief to evaluate the therapeutic potential of dronabinol in chronic pain management. Development of objective mechanistic diagnostic biomarkers reflecting altered sensory and cognitive processing in the brain is essential to evaluate dronabinol induced analgesia, and to permit identification of responders and/or non-responders to dronabinol treatment.