painPREDICT: first interim data from the development of a new patient-reported pain questionnaire to predict treatment response using sensory symptom profiles

Reflections from the OARSI 2022 clinical trials symposium: The pain of OA-Deconstruction of pain and patient-reported outcome measures for the benefit of patients and clinical trial design

OBJECTIVE

Osteoarthritis (OA) drug development is hampered by a number of challenges. One of the main challenges is the apparent discordance between pain and structure, which has had a significant impact on drug development programs and has led to hesitance among stakeholders. Since 2017, the Clinical Trials Symposium (CTS) has been hosted under the Osteoarthritis Research Society International (OARSI) leadership. OARSI and the CTS steering committee yearly invite and encourage discussions on selected special subject matter between regulators, drug developers, clinicians, clinical researchers, biomarker specialists, and basic scientists to progress drug development in the OA field.

METHOD

The main topic for the 2022 OARSI CTS was to elucidate the many facets of pain in OA and to enable a discussion between regulators (Food and Drug Administration (FDA) and the European Medicines Agency (EMA)) and drug developers to clarify outcomes and study designs for OA drug development.

RESULTS

Signs or symptoms indicative of nociceptive pain occur in 50-70% of OA patients, neuropathic-like pain in 15-30% of patients, and nociplastic pain in 15-50% of patients. Weight-bearing knee pain is associated with bone marrow lesions and effusions. There are currently no simple objective functional tests whose improvements correlate with patient perceptions.

CONCLUSIONS

The CTS participants, in collaboration with the FDA and EMA, raised several suggestions that they consider key to future clinical trials in OA including the need for more precise differentiation of pain symptoms and mechanisms, and methods to reduce placebo responses in OA trials.

Personalized treatment of neuropathic pain: Where are we now?

BACKGROUND

The treatment of neuropathic pain remains a major unmet need that the development of personalized and refined treatment strategies may contribute to address.

DATABASE

In this narrative review, we summarize the various approaches based on objective biomarkers or clinical markers that could be used.

RESULTS

In principle, the validation of objective biomarkers would be the most robust approach. However, although promising results have been reported demonstrating a potential value of genomics, anatomical or functional markers, the clinical validation of these markers has only just begun. Thus, most of the strategies documented to date have been based on the development of clinical markers. In particular, many studies have suggested that the identification of specific subgroups of patients presenting with specific combinations of symptoms and signs would be a relevant approach. Two main approaches have been used to identify relevant sensory profiles: quantitative sensory testing and specific patients reported outcomes based on description of pain qualities.

CONCLUSION

We discuss here the advantages and limitations of these approaches, which are not mutually exclusive.

SIGNIFICANCE

Recent data indicate that various new treatment strategies based on predictive biological and/or clinical markers could be helpful to better personalized and therefore improve the management of neuropathic pain.

Maximizing treatment efficacy through patient stratification in neuropathic pain trials

Treatment of neuropathic pain remains inadequate despite the elucidation of multiple pathophysiological mechanisms and the development of promising therapeutic compounds. The lack of success in translating knowledge into clinical practice has discouraged pharmaceutical companies from investing in pain medicine; however, new patient stratification approaches could help bridge the translation gap and develop individualized therapeutic approaches. As we highlight in this article, subgrouping of patients according to sensory profiles and other baseline characteristics could aid the prediction of treatment success. Furthermore, novel outcome measures have been developed for patients with neuropathic pain. The extent to which sensory profiles and outcome measures can be employed in routine clinical practice and clinical trials and across distinct neuropathic pain aetiologies is yet to be determined. Improvements in animal models, drawing on our knowledge of human pain, and robust public-private partnerships will be needed to pave the way to innovative and effective pain medicine in the future.

Patient Reported Outcome Measures in Chronic Neuropathic Pain Clinical Trials - A Systematic Literature Review

In neuropathic pain clinical trials, the patient's perspective is often insufficiently reflected focusing mainly on pain intensity. Comparability of outcome assessment is limited due to heterogenous patient reported outcome measures (PROMs). The MEDLINE, CENTRAL, and Embase databases and reference lists of published meta-analyses were searched. Randomized controlled studies assessing treatment efficacy of drugs for chronic neuropathic pain were included. PROMs were assigned to recommended IMMPACT/NeuPSIG domains: pain intensity, pain other aspects, physical functioning, emotional functioning, global improvement and satisfaction, adverse events, participant disposition. Domains and PROMs were compared regarding the publication year and methodological quality of the studies. Within the 251 included studies 200 PROMs were used with 27 being recommended by IMMPACT/NeuPSIG. The number of domains was higher in high/moderate quality studies. The (sub-) domains 'physical functioning', 'global improvement and satisfaction', and 'neuropathic pain quality' were assessed more frequently in high/moderate quality studies and those published after 2011. Recent studies and those of better quality more often used the recommended PROMs. Although neuropathic assessment via PROMs has improved, there is still a high heterogeneity. A standardized core set of outcome domains and should be defined to improve neuropathic pain treatment and to achieve better comparability of clinical trials. Perspective: This systematic literature review assesses the use of patient reported outcome measures (PROMs) in chronic neuropathic pain. The results show that there is still a high heterogeneity, highlighting the need for a standardized core set of outcome domains and PROMs to improve comparability of clinical trials and neuropathic pain treatment.

Precision Medicine in Neuropathic Pain

Neuropathic pain is a common chronic pain condition that is caused by a lesion or disease of the somatosensory nervous system. The multitude of sensory negative and positive sensations and associated comorbidities have a major impact on quality of life of affected patients. Current treatment options often only lead to a partial pain relief or are even completely ineffective. In addition, many clinical trials for the development of new drugs have not met the primary endpoint. Therefore, there is still an unmet clinical need in neuropathic pain syndromes. One reason for this therapeutic dilemma could be the heterogeneity of neuropathic pain with a variety of pathophysiological pain mechanisms that are expressed differently in each patient regardless of the underlying disease etiology. Reclassification of neuropathic pain syndromes therefore focuses on the underlying mechanisms of pain development rather than the disease etiology. A priori stratification of patients based on these individual mechanisms could allow the identification of potential treatment responders and thus realize the concept of a mechanism-based treatment. As no biomarkers for pain mechanisms have been discovered yet, one has to rely on surrogate markers that are thought to be closely related to these mechanisms. In this chapter, we present promising predictive biomarkers, focusing in particular on sensory symptoms and signs assessed by patient-reported outcome measures and sensory testing, and discuss how these tools might be used in clinical trials in the future.

Cannabis-Based Medicines and Medical Cannabis for Chronic Neuropathic Pain

Neuropathic pain represents a broad category of pain syndromes that include a wide variety of peripheral and central disorders. The overall prevalence of neuropathic pain in the general population is reported to be between 7 and 10%. Management of neuropathic pain presents an unmet clinical need, with less than 50% of patients achieving substantial pain relief with medications currently recommended such as pregabalin, gabapentin, duloxetine and various tricyclic antidepressants. It has been suggested that cannabis-based medicines (CbMs) and medical cannabis (MC) may be a treatment option for those with chronic neuropathic pain. CbMs/MC are available in different forms: licensed medications or medical products (plant-derived and/or synthetic products such as tetrahydrocannabinol or cannabidiol); magistral preparations of cannabis plant derivatives with defined molecular content such as dronabinol (tetrahydrocannabinol); and herbal cannabis with a defined content of tetrahydrocannabinol and/or cannabidiol, together with other active ingredients (phytocannabinoids other than cannabidiol/tetrahydrocannabinol, terpenes and flavonoids). The availability of different types of CbMs/MC varies between countries worldwide. Systematic reviews of available randomised controlled trials have stated low-quality evidence for CbMs and MC for chronic neuropathic pain. Depending on the studies included in the various quantitative syntheses, authors have reached divergent conclusions on the efficacy of CbMs/MC for chronic neuropathic pain (from not effective to a clinically meaningful benefit). Clinically relevant side effects of CbMs/MC, especially for central nervous system and psychiatric disorders, have been reported by some systematic reviews. Recommendations for the use of CbMs/MC for chronic neuropathic pain by various medical associations also differ, from negative recommendations, no recommendation possible, recommended as third-line therapy, or recommended as an alternative in selected cases failing standard therapies within a multimodal concept. After reading this paper, readers are invited to formulate their own conclusions regarding the potential benefits and harms of CbMs/MC for the treatment of chronic neuropathic pain.

Bedside testing for precision pain medicine

PURPOSE OF REVIEW

In recent years, the identification of therapy responders has become an increasing focus of pain research. On the basis of laboratory quantitative sensory testing, subgroups of patients were identified, which have been shown to predict treatment response. However, the high cost and time expenditure limits the use of these lab-QST protocols in clinical practice and large clinical trials.

RECENT FINDINGS

Recently, different bedside testing protocols were developed as easy-to-use alternative for lab-QST. In addition, patients can be subgrouped based on their symptoms by use of patient-reported outcome measures. First results suggest that these approaches can be used to stratify patients into pathophysiological-plausible subgroups predictive for treatment response.

SUMMARY

This review presents recently developed bedside approaches that can be implemented as stratification tools in future clinical trials to realize individualized pain medicine. Being complementary rather than replaceable, future studies should combine questionnaires and sensory testing and apply them prospectively in large clinical trials.

Methods to discriminate between mechanism-based categories of pain experienced in the musculoskeletal system: a systematic review

ABSTRACT

Mechanism-based classification of pain has been advocated widely to aid tailoring of interventions for individuals experiencing persistent musculoskeletal pain. Three pain mechanism categories (PMCs) are defined by the International Association for the Study of Pain: nociceptive, neuropathic, and nociplastic pain. Discrimination between them remains challenging. This study aimed to build on a framework developed to converge the diverse literature of PMCs to systematically review methods purported to discriminate between them; synthesise and thematically analyse these methods to identify the convergence and divergence of opinion; and report validation, psychometric properties, and strengths/weaknesses of these methods. The search strategy identified articles discussing methods to discriminate between mechanism-based categories of pain experienced in the musculoskeletal system. Studies that assessed the validity of methods to discriminate between categories were assessed for quality. Extraction and thematic analysis were undertaken on 184 articles. Data synthesis identified 200 methods in 5 themes: clinical examination, quantitative sensory testing, imaging, diagnostic and laboratory testing, and pain-type questionnaires. Few methods have been validated for discrimination between PMCs. There was general convergence but some disagreement regarding findings that discriminate between PMCs. A combination of features and methods, rather than a single method, was generally recommended to discriminate between PMCs. Two major limitations were identified: an overlap of findings of methods between categories due to mixed presentations and many methods considered discrimination between 2 PMCs but not others. The results of this review provide a foundation to refine methods to differentiate mechanisms for musculoskeletal pain.

Diabetic Neuropathy: a Critical, Narrative Review of Published Data from 2019

PURPOSE OF REVIEW

This manuscript is a systematic, narrative review that compiles and describes all data available from 2019 related to epidemiologic, diagnostic, and therapeutic advances in diabetic neuropathy (DN).

RECENT FINDINGS

Epidemiology of DN is discussed. Diagnostic modalities include predictive models, electrodiagnostics, imaging, and biomarkers. A majority of studies on the treatment of diabetic peripheral neuropathy (DPN) involve pharmacotherapy, but complementary and alternative medicine, exercise, modalities, psychological, interventional, and surgical options are also explored. DN is a highly prevalent and debilitating consequence of diabetes that can present challenges to the clinician as the assessment is largely subjective with different phenotypic presentations among patients. Treatment of DN is largely symptomatic as the pathogenesis of DN is not fully understood and is likely multifactorial. It is evident from the broad range of treatments that too often provide unsatisfactory relief that there is no consensus about a single most effective treatment for DN, and monotherapy rarely proves to be successful.

When to consider "mixed pain"? The right questions can make a difference!

The term "mixed pain" is increasingly applied for specific clinical scenarios, such as low back pain, cancer pain and postsurgical pain, in which there "is a complex overlap of the different known pain types (nociceptive, neuropathic, nociplastic) in any combination, acting simultaneously and/or concurrently to cause pain in the same body area." Whether mixed pain is the manifestation of neuropathic and nociceptive mechanisms operating simultaneously or concurrently, or the result of an entirely independent pathophysiological mechanism - distinct from nociceptive, nociplastic and neuropathic pain - is currently unknown. At present, the diagnosis of mixed pain is made based on clinical judgement following detailed history-taking and thorough physical examination, rather than by formal confirmation following explicit screening or diagnostic criteria; this lack of formalized screening or diagnostic tools for mixed pain is problematic for physicians in primary care, who encounter patients with probable mixed pain states in their daily practice. This article outlines a methodical approach to clinical evaluation of patients presenting with acute, subacute or chronic pain, and to possibly identifying those who have mixed pain. The authors propose the use of nine simple key questions, which will provide the practicing clinician a framework for identifying the predominant pain mechanisms operating within the patient. A methodical, fairly rapid, and comprehensive assessment of a patient in chronic pain - particularly one suffering from pain with both nociceptive and neuropathic components - allows validation of their experience of chronic pain as a specific disease and, importantly, allows the institution of targeted treatment.

Cancer Pain Assessment and Classification

More than half of patients affected by cancer experience pain of moderate-to-severe intensity, often in multiple sites, and of different etiologies and underlying mechanisms. The heterogeneity of pain mechanisms is expressed with the fluctuating nature of cancer pain intensity and clinical characteristics. Traditional ways of classifying pain in the cancer population include distinguishing pain etiology, clinical characteristics related to pain and the patient, pathophysiology, and the use of already validated classification systems. Concepts like breakthrough, nociceptive, neuropathic, and mixed pain are very important in the assessment of pain in this population of patients. When dealing with patients affected by cancer pain it is also very important to be familiar to the characteristics of specific pain syndromes that are usually encountered. In this article we review methods presently applied for classifying cancer pain highlighting the importance of an accurate clinical evaluation in providing adequate analgesia to patients.