A multicenter, randomized, double-blind, controlled study of NGX-4010, a high-concentration capsaicin patch, for the treatment of postherpetic neuralgia

Interventional management of cancer pain

PURPOSE OF REVIEW

Interventional techniques were the mainstay for cancer pain management before the WHO ladder and opioids were freely available. The three-step WHO ladder has its limitations, and cancer pain is often under treated. Advances in treatment options mean that cancer patients are living longer and pain interventions may have a role to play even early in the cancer diagnosis for better quality of analgesia. The role of high doses of opioids in pain management is also currently under scrutiny.

RECENT FINDINGS

Recent advances in intrathecal analgesia, radiofrequency techniques, both in tumour ablation and neurotomies, are being widely used for palliation. Vertebroplasty techniques have been used not only for pain relief, but also for stabilization. Improved imaging and thoracoscopic techniques have made coeliac plexus and splanchnic blockade safer and more efficacious. There has been recent interest in percutaneous cordotomy with newer techniques using computed tomography/MRI and endoscopy guidance. Percutaneous electrical nerve stimulation and 8% capsaicin patches have been successfully used for managing neuropathic pain in cancer.

SUMMARY

Interventions form an integral part in providing pain relief in complex cancer pains. Oncologists and palliative care physicians are to be educated on the usefulness and timing of interventions in the management of complex cancer pain.

NGX-4010, a capsaicin 8% dermal patch, administered alone or in combination with systemic neuropathic pain medications, reduces pain in patients with postherpetic neuralgia

OBJECTIVES

Analyses of integrated data from 4 controlled postherpetic neuralgia studies evaluated the effect of NGX-4010, a capsaicin 8% patch, administered alone or together with systemic neuropathic pain medications.

METHODS

Patients recorded their “average pain for the past 24 hours” daily for 12 weeks using an 11-point Numeric Pain Rating Scale (NPRS). Efficacy assessment included the percentage NPRS score reduction from baseline during weeks 2 to 8 and 2 to 12, the proportion of patients responding during weeks 2 to 8 and 2 to 12 and the Patient Global Impression of Change (PGIC) at weeks 8 and 12.

RESULTS

During the studies, 302 NGX-4010 and 250 control (capsaicin, 0.04% wt/wt) patients were using at least 1 systemic neuropathic pain medication; 295 NGX-4010 and 280 control patients were not. During weeks 2 to 8, NGX-4010 patients reported greater reductions in NPRS scores compared with control both in patients using systemic neuropathic pain medications (26.1% vs. 18.1%, P=0.0011) and in patients not using these medications (36.5% vs. 26.2%, P=0.0002). Patients not using systemic neuropathic pain medications reported a greater reduction in pain compared with patients using these medications in both, NGX-4010 and control groups, resulting in comparable treatment differences between NGX-4010 and control regardless of systemic neuropathic pain medication use. Similar results were seen during weeks 2 to 12, for the responder and PGIC analyses. Transient, capsaicin-related application site reactions were the most common adverse events and not affected by systemic neuropathic pain medication use.

CONCLUSION

A single 60-minute NGX-4010 treatment reduces PHN for up to 12 weeks regardless of concomitant systemic neuropathic pain medication use.

Considerations for improving assay sensitivity in chronic pain clinical trials: IMMPACT recommendations

A number of pharmacologic treatments examined in recent randomized clinical trials (RCTs) have failed to show statistically significant superiority to placebo in conditions in which their efficacy had previously been demonstrated. Assuming the validity of previous evidence of efficacy and the comparability of the patients and outcome measures in these studies, such results may be a consequence of limitations in the ability of these RCTs to demonstrate the benefits of efficacious analgesic treatments vs placebo ("assay sensitivity"). Efforts to improve the assay sensitivity of analgesic trials could reduce the rate of falsely negative trials of efficacious medications and improve the efficiency of analgesic drug development. Therefore, an Initiative on Methods, Measurement, and Pain Assessment in Clinical Trials consensus meeting was convened in which the assay sensitivity of chronic pain trials was reviewed and discussed. On the basis of this meeting and subsequent discussions, the authors recommend consideration of a number of patient, study design, study site, and outcome measurement factors that have the potential to affect the assay sensitivity of RCTs of chronic pain treatments. Increased attention to and research on methodological aspects of clinical trials and their relationships with assay sensitivity have the potential to provide the foundation for an evidence-based approach to the design of analgesic clinical trials and expedite the identification of analgesic treatments with improved efficacy and safety.

Is treatment of postherpetic neuralgia in the community consistent with evidence-based recommendations?

Few studies have examined the extent to which treatment of patients with neuropathic pain in the community is consistent with evidence-based treatment recommendations. U.S. health care claims were used to identify patients who received a diagnosis of postherpetic neuralgia (PHN). The initial pharmacologic treatments and changes to these treatment regimens were categorized according to the International Association for the Study of Pain Neuropathic Pain Special Interest Group recommendations for first-, second-, and third-line treatment of neuropathic pain. The results indicated that the treatment of PHN was only partially consistent with these treatment recommendations. Of the patients diagnosed with PHN who were not already on a specified treatment, 70% began treatment with either a first-, second-, or third-line treatment or a not-recommended treatment, and 30% did not begin treatment with any of these medications. Only one-quarter of patients began treatment with a first-line medication, the same percentage that began treatment with either a third-line medication or a not-recommended treatment. There was a wide range of initial treatment durations, but the means and medians suggest that patients and clinicians often decide to change the initial treatment within 2 months, either by discontinuing it, replacing it with a new medication, or adding a new medication. Although there were generally shorter treatment durations with opioid analgesics and tramadol, these medications were more frequently used in beginning treatment than the other treatments. The results suggest that a considerable number of patients with PHN in the community are not receiving evidence-based treatment.

Tolerability of NGX-4010, a capsaicin 8% patch, in conjunction with three topical anesthetic formulations for the treatment of neuropathic pain

BACKGROUND

The objective of this study was to assess the safety, tolerability, and preliminary efficacy of NGX-4010, a capsaicin 8% patch, following pretreatment with three different topical anesthetics in patients with peripheral neuropathic pain.

METHODS

This open-label, multicenter study enrolled 117 patients with post-herpetic neuralgia, HIV-associated distal sensory polyneuropathy, or painful diabetic neuropathy. Patients received pretreatment with one of three lidocaine 4%-based topical anesthetics (L.M.X.4(®) [Ferndale Laboratories Inc, Ferndale, MI], Topicaine(®) Gel [Estela Basso, Jupiter, FL], or Betacaine Enhanced Gel 4 [Tiberius Inc, Tampa, FL]) for 60 minutes followed by a single 60- or 90-minute NGX-4010 application, and were followed for 12 weeks. Tolerability and safety measures included "pain now" Numeric Pain Rating Scale (NPRS) scores, dermal assessments, medication use for treatment-related pain, adverse events (AEs), clinical laboratory parameters, physical examinations, and vital signs. The primary efficacy variable was the percentage change in mean NPRS scores for "average pain for the past 24 hours" from baseline to weeks 2 through 12.

RESULTS

Treatment with NGX-4010 following pretreatment with any of the three topical anesthetics was generally safe and well tolerated. Nearly all patients completed ≥90% of the planned NGX-4010 application duration. The most common treatment-related AEs, application-site burning and application-site pain, were transient, mostly mild or moderate, and could be adequately managed by local cooling or short-acting oral opioid analgesics. Although slightly more patients used medication for treatment-related discomfort following pretreatment with Topicaine compared with L.M.X.4 or Betacaine, there were no statistical differences between the topical anesthetics. Neuropathic pain reduction from baseline to weeks 2 through 12 was approximately 30% and was similar among the topical anesthetics; the proportion of responders ranged from 45% to 50%.

CONCLUSION

Treatment with NGX-4010 following pretreatment with any of the three topical anesthetics was generally safe and well tolerated; no significant differences in the parameters measured were noted between the pretreatment groups.

Tolerability of NGX-4010, a capsaicin 8% dermal patch, following pretreatment with lidocaine 2.5%/prilocaine 2.5% cream in patients with post-herpetic neuralgia

Background

Post-herpetic neuralgia (PHN) is a common type of neuropathic pain that can severely affect quality of life. NGX-4010, a capsaicin 8% dermal patch, is a localized treatment that can provide patients with significant pain relief for up to 3 months following a single 60-minute application. The NGX-4010 application can be associated with application-site pain and in previous clinical trials pretreatment with a topical 4% lidocaine anesthetic was used to enhance tolerability. The aim of the current investigation was to evaluate tolerability of NGX-4010 after pretreatment with lidocaine 2.5%/prilocaine 2.5% anesthetic cream.

Methods

Twenty-four patients with PHN were pretreated with lidocaine 2.5%/prilocaine 2.5% cream for 60 minutes before receiving a single 60-minute application of NGX-4010. Tolerability was assessed by measuring patch application duration, the proportion of patients completing over 90% of the intended treatment duration, application site-related pain using the Numeric Pain Rating Scale (NPRS), and analgesic medication use to relieve such pain. Safety was assessed by monitoring adverse events (AEs) and dermal irritation using dermal assessment scores.

Results

The mean treatment duration of NGX-4010 was 60.2 minutes and all patients completed over 90% of the intended patch application duration. Pain during application was transient. A maximum mean change in NPRS score of +3.0 was observed at 55 minutes post-patch application; pain scores gradually declined to near pre-anesthetic levels (+0.71) within 85 minutes of patch removal. Half of the patients received analgesic medication on the day of treatment; by Day 7, no patients required medication. The most common AEs were application site-related pain, erythema, edema, and pruritus. All patients experienced mild dermal irritation 5 minutes after patch removal, which subsequently decreased; at Day 7, no irritation was evident. The maximum recorded dermal assessment score was 2.

Conclusion

NGX-4010 was well tolerated following pretreatment with lidocaine 2.5%/prilocaine 2.5% cream in patients with PHN. The tolerability of the patch application appeared comparable with that seen in other studies that used 4% lidocaine cream as the pretreatment anesthetic. This study is registered at http://www.clinicaltrials.gov as number NCT00916942.

Tolerability of NGX-4010, a capsaicin 8% patch for peripheral neuropathic pain

BACKGROUND/PURPOSE

NGX-4010 (QUTENZA(™); NeurogesX Inc, San Mateo, CA), a capsaicin 8% dermal patch, is licensed in the European Union for the treatment of peripheral neuropathic pain (PNP) in nondiabetic adults and in the United States for the treatment of neuropathic pain associated with postherpetic neuralgia (PHN). While NGX-4010 treatment is associated with a low risk of systemic adverse events, patch application-related pain is common and may be managed with local cooling and/or oral analgesics. This article characterizes the tolerability of NGX-4010 and will help to guide any pain management.

METHODS

This integrated analysis of tolerability data collected from the NGX-4010 clinical study program included 1696 patients with PNP. Patch application-related pain on the treatment day was captured as Numeric Pain Rating Scale (NPRS) "pain now" scores while "average pain for the past 24 hours" NPRS scores were analyzed for 7 days following treatment. Other tolerability assessments included the percentage of patients completing ≥90% of the intended treatment duration and patients using medication for patch application-related pain.

RESULTS

The mean maximum change in "pain now" NPRS scores from pretreatment levels during and after patch application was 2.6 for all patients. This pain was transient and resolved following patch removal. Mean "average pain for the past 24 hours" NPRS scores returned to baseline by the evening of the treatment day for patients with PHN, and the evening of day 2 for patients with human immunodeficiency virus-associated distal sensory polyneuropathy or painful diabetic neuropathy. Repeated NGX-4010 applications did not affect the intensity of patch application-related pain. Almost all patients (≥98%) completed ≥90% of the full treatment duration, regardless of the number of treatments received.

CONCLUSION

Transient patch application-related pain with NGX-4010 can be managed with local cooling and/or oral analgesics in nearly all cases. Patient adherence to the full intended treatment duration indicated that patch application-related pain was not a barrier to NGX-4010 use.

Topical capsaicin for pain management: therapeutic potential and mechanisms of action of the new high-concentration capsaicin 8% patch

Topical capsaicin formulations are used for pain management. Safety and modest efficacy of low-concentration capsaicin formulations, which require repeated daily self-administration, are supported by meta-analyses of numerous studies. A high-concentration capsaicin 8% patch (Qutenza™) was recently approved in the EU and USA. A single 60-min application in patients with neuropathic pain produced effective pain relief for up to 12 weeks. Advantages of the high-concentration capsaicin patch include longer duration of effect, patient compliance, and low risk for systemic effects or drug-drug interactions. The mechanism of action of topical capsaicin has been ascribed to depletion of substance P. However, experimental and clinical studies show that depletion of substance P from nociceptors is only a correlate of capsaicin treatment and has little, if any, causative role in pain relief. Rather, topical capsaicin acts in the skin to attenuate cutaneous hypersensitivity and reduce pain by a process best described as 'defunctionalization' of nociceptor fibres. Defunctionalization is due to a number of effects that include temporary loss of membrane potential, inability to transport neurotrophic factors leading to altered phenotype, and reversible retraction of epidermal and dermal nerve fibre terminals. Peripheral neuropathic hypersensitivity is mediated by diverse mechanisms, including altered expression of the capsaicin receptor TRPV1 or other key ion channels in affected or intact adjacent peripheral nociceptive nerve fibres, aberrant re-innervation, and collateral sprouting, all of which are defunctionalized by topical capsaicin. Evidence suggests that the utility of topical capsaicin may extend beyond painful peripheral neuropathies.

Emerging drugs for osteoarthritis

INTRODUCTION

Osteoarthritis (OA), the most prevalent form of joint disease, affects as much as 13% of the world's population. In the USA, it is the leading cause of disability in people over age 65 and is characterized by progressive cartilage loss, bone remodeling, osteophyte formation and synovial inflammation with resultant joint pain and disability. There are no treatments marketed for structural disease modification; current treatments mainly target symptoms, with > 75% of patients reporting need for additional symptomatic treatment.

AREAS COVERED

Drugs in later development (Phase II - III) for OA pain and joint structural degeneration are reviewed. Topics that are not covered in this article are procedural-based (e.g., arthrocentesis, physical therapy), behavioral-based (e.g., weight loss, pain coping techniques) or device-based (e.g., knee braces, surgical implants) treatments.

EXPERT OPINION

More in-depth understanding of the pathophysiology of the disease, as well as elucidation of the link between clinical symptomatology and structural changes in the joint will likely lead to the development of novel target classes with promising efficacy in the future. Efficacy notwithstanding, there remain significant hurdles to overcome in clinical development of these therapeutics, inherent in the progression pattern of the disease as well as challenges with readouts for both pain and structure modification trials.

Efficacy, safety, and tolerability of NGX-4010, capsaicin 8% patch, in an open-label study of patients with peripheral neuropathic pain

AIMS

To assess efficacy, safety, and tolerability of NGX-4010, capsaicin 8% patch, in patients with peripheral neuropathic pain.

METHODS

This open-label, uncontrolled, 12-week study enrolled 25 patients with postherpetic neuralgia (PHN), one with HIV-distal sensory polyneuropathy, and 91 with painful diabetic neuropathy (PDN). Patients received pre-treatment with one of three 4% lidocaine topical anesthetics (L.M.X.4¹, Topicaine Gel², or Betacaine Enhanced Gel 4³) followed by a single 60- or 90-min NGX-4010 application. The primary efficacy variable was the percentage change in Numeric Pain Rating Scale scores from baseline to Weeks 2-12. Adverse events (AEs), laboratory parameters, vital signs, neurosensory examinations, dermal assessments, treatment-related pain scores, and medication use for treatment-related pain were collected.

RESULTS

PDN and PHN patients achieved a 31% and 28% mean pain decrease from baseline during Weeks 2-12, respectively, and 47% and 44%, respectively, were responders (≥30% pain decrease). Mild or moderate treatment-site-related burning and pain were the most common AEs and there was no evidence of impaired neurosensory function.

CONCLUSIONS

NGX-4010 in conjunction with any of the three topical anesthetics tested was generally safe and well tolerated and reduced pain over a 12-week period in patients with PDN and PHN.

Cost-effectiveness analysis of a new 8% capsaicin patch compared to existing therapies for postherpetic neuralgia

OBJECTIVE

The purpose of this study was to compare the cost effectiveness of a new 8% capsaicin patch, compared to the current treatments for postherpetic neuralgia (PHN), including tricyclic antidepressants (TCAs), topical lidocaine patches, duloxetine, gabapentin, and pregabalin.

METHODS

A 1-year Markov model was constructed for PHN with monthly cycles, including dose titration and management of adverse events. The perspective of the analysis was from a payer perspective, managed-care organization. Clinical trials were used to determine the proportion of patients achieving at least a 30% improvement in PHN pain, the efficacy parameter. The outcome was cost per quality-adjusted life-year (QALY); second-order probabilistic sensitivity analyses were conducted.

RESULTS

The effectiveness results indicated that 8% capsaicin patch and topical lidocaine patch were significantly more effective than the oral PHN products. TCAs were least costly and significantly less costly than duloxetine, pregabalin, topical lidocaine patch, 8% capsaicin patch, but not gabapentin. The incremental cost-effectiveness ratio for the 8% capsaicin patch overlapped with the topical lidocaine patch and was within the accepted threshold of cost per QALY gained compared to TCAs, duloxetine, gabapentin, and pregablin. The frequency of the 8% capsaicin patch retreatment assumption significantly impacts its cost-effectiveness results. There are several limitations to this analysis. Since no head-to-head studies were identified, this model used inputs from multiple clinical trials. Also, a last observation carried forward process was assumed to have continued for the duration of the model. Additionally, the trials with duloxetine may have over-predicted its efficacy in PHN. Although a 30% improvement in pain is often an endpoint in clinical trials, some patients may require greater or less improvement in pain to be considered a clinical success.

CONCLUSIONS

The effectiveness results demonstrated that 8% capsaicin and topical lidocaine patches had significantly higher effectiveness rates than the oral agents used to treat PHN. In addition, this cost-effectiveness analysis found that the 8% capsaicin patch was similar to topical lidocaine patch and within an accepted cost per QALY gained threshold compared to the oral products.

Effect of duration of postherpetic neuralgia on efficacy analyses in a multicenter, randomized, controlled study of NGX-4010, an 8% capsaicin patch evaluated for the treatment of postherpetic neuralgia

BACKGROUND

Postherpetic neuralgia (PHN) is a painful and difficult to treat complication of acute herpes zoster. Current treatment options provide only partial relief and are often limited by poor tolerability. We evaluated the safety and efficacy of a single 60-minute application of NGX-4010, an 8% capsaicin patch, in patients with PHN.

METHODS

This multicenter, double-blind, controlled study randomized 155 patients 2:1 to receive either NGX-4010 or a 0.04% capsaicin control patch. Patients were at least 18 years old with PHN for at least 3 months, and an average Numeric Pain Rating Scale (NPRS) score of 3 to 9. The primary efficacy endpoint was the percentage change in NPRS score from baseline to weeks 2-8.

RESULTS

The mean percent reduction in "average pain for the past 24 hours" NPRS scores from baseline to weeks 2-8 was greater in the NGX-4010 group (36.5%) compared with control (29.9%) although the difference was not significant (p = 0.296). PGIC analysis demonstrated that more NGX-4010 recipients considered themselves improved (much, or very much) compared with control at weeks 8 and 12, but the differences did not reach statistical significance. Post hoc analyses of patients with PHN for at least 6 months showed significantly greater reductions in "average pain for the past 24 hours" NPRS scores from baseline to weeks 2-8 in NGX-4010 patients compared to controls (37.6% versus 23.4%; p = 0.0291). PGIC analysis in this subgroup demonstrated that significantly more NGX-4010 recipients considered themselves much or very much improved compared with control at week 12 (40% versus 20%; p = 0.0403;).

CONCLUSIONS

Although treatment appeared to be safe and well tolerated, a single 60-minute application of NGX-4010 failed to show efficacy in this study which included patients with PHN for less than 6 months. Large reductions in pain observed among control patients with pain for less than 6 months may have been due to spontaneous resolution of PHN, may have confounded the results of the prespecified analyses, and should be taken into account when designing PHN studies.

TRIAL REGISTRATION

NCT00068081.