Predicting Treatment Response with Sensory Phenotyping in Post-Traumatic Neuropathic Pain.

Objective Currently available treatments for neuropathic pain are only modestly efficacious when assessed in randomized clinical trials and work for only some patients in the clinic. Induced-pain or gain-of-function phenotypes have been shown to predict response to analgesics (vs placebos) in patients with neuropathic pain. However, the predictive value of these phenotypes has never been studied in post-traumatic neuropathic pain. Methods Mixed-effects models for repeated measures were used to evaluate the efficacy of pregabalin vs placebo in subgroups with induced-pain phenotypes (i.e. hyperalgesia or allodynia) in data from a recent, multinational randomized clinical trial (N = 539) that identified phenotypic subgroups through the use of a structured clinical exam. Results The difference in mean pain score between the active and placebo groups (i.e. delta) after 15 weeks of treatment for the subgroup with hyperalgesia was –0.76 (P  = 0.001), compared with 0.19 (P  = 0.47) for the subgroup that did not have hyperalgesia. The treatment-by-phenotype interaction, which tests whether subgroups have statistically different treatment responses, was significant (P  = 0.0067). The delta for the subgroup with allodynia was –0.31 (P  = 0.22), compared with –0.30 (P  = 0.22) for the subgroup that did not have allodynia (treatment-by-phenotype interaction P  = 0.98). Conclusions These data suggest that hyperalgesia, but not allodynia, predicts response to pregabalin in patients with chronic post-traumatic neuropathic pain. This study extends the growing data supporting the utility of induced-pain phenotypes to predict response to analgesics in post-traumatic neuropathic pain. Sensory phenotyping in large, multisite trials through the use of a structured clinical exam has the potential to accelerate the development of new analgesics and improve the generalizability of clinical trial results. [ABSTRACT FROM AUTHOR]