Onset and maintenance of efficacy of subcutaneous tanezumab in patients with moderate to severe osteoarthritis of the knee or hip: A 16-week dose-titration study.

OBJECTIVE: To examine the onset and maintenance of efficacy of subcutaneous tanezumab for pain relief and functional improvement in difficult-to-treat patients with moderate-to-severe osteoarthritis (OA) in a 16-week dose-titration study (NCT02697773). METHODS: Patients were randomized to placebo (placebo group) or tanezumab 2.5 mg at baseline and week 8 (tanezumab 2.5 mg group), or tanezumab 2.5 mg at baseline and tanezumab 5 mg at week 8 (tanezumab 2.5/5 mg group). Analyses included change from baseline in average daily index joint pain and Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) Pain and Physical Function, and treatment responses (WOMAC Pain improvement criteria and Outcome Measures in Rheumatology-Osteoarthritis Research Society International [OMERACT-OARSI] criteria). RESULTS: The 696 patients received placebo (n = 232), tanezumab 2.5 mg (n = 231), or tanezumab 2.5/5 mg (n = 233). Average daily index joint pain was statistically significantly improved within the first week (day 3-5) with tanezumab 2.5 mg compared with placebo. On first post-randomization WOMAC measurement (week 2), both tanezumab groups had statistically significant improvements compared with placebo in WOMAC Pain and Physical Function, and more tanezumab-treated patients achieved treatment response criteria (≥30%, ≥50%, or ≥70% reduction in WOMAC Pain or OMERACT-OARSI response). Efficacy was generally maintained throughout the 16-week treatment period. CONCLUSION: Subcutaneous tanezumab provided statistically significant improvements compared with placebo in average daily index joint pain within the first week and WOMAC Pain and Physical Function (week 2) that were generally maintained throughout the 16-week treatment period. Tanezumab 5 mg provided only modest additional efficacy over tanezumab 2.5 mg.

Results from clinical trials of a selective ionotropic glutamate receptor 5 (iGluR5) antagonist, LY5454694 tosylate, in 2 chronic pain conditions.

This article reports results of 2 studies investigating LY545694 in pain due to osteoarthritis (OA) of the knee and diabetic peripheral neuropathic pain (DPNP). Study I randomized patients to either of 2 doses of LY545694 or to placebo, and study II randomized patients to either of 3 doses of LY545694, to pregabalin, or to placebo. No significant differences between LY545694 groups and placebo were observed on the primary (average pain severity) or secondary efficacy measures in either study. Notably, study I lacked an active control, and, in study II, pregabalin, did not separate from placebo. Treatment-emergent nausea, vomiting, and dizziness were significantly more frequent in the LY545694 groups in both trials (P⩽.05), and significantly more LY545694-treated patients discontinued because of adverse events (P<.001). Steady-state concentrations of LY545694 were comparable in patients in both studies but were lower than exposures required for efficacy in animal models of pain behavior. Because the active control did not separate from placebo in the DPNP study, the study was potentially failed, rather than negative. Without an active control, it is unknown whether the OA study was negative or failed. Consequently, efficacy of selective ionotropic glutamate receptor antagonism in chronic pain conditions may warrant further investigation. Future trials should consider different pain conditions, contain a positive control with larger patient numbers per arm, and be conducted within a single region.

Safety, tolerability, pharmacokinetics, and effects on human experimental pain of the selective ionotropic glutamate receptor 5 (iGluR5) antagonist LY545694 in healthy volunteers.

The objective of this study was to establish in healthy volunteers the maximally tolerated multiple dose (MTMD) of the ionotropic glutamate receptor 5 antagonist LY545694 (part A), and to investigate whether that dose had analgesic or antihyperalgesic effects in the brief thermal stimulation (BTS) pain model (Part B). Part A was a double-blind, placebo-controlled study in 3 groups of 10 healthy men. To simulate an extended-release formulation, study drug was administered orally over 6hours (12 equally divided aliquots at 30-minute intervals). Part B was a double-blind, placebo-controlled, double-dummy, 3-way crossover study in 27 healthy men. At each of the 3 study periods, subjects received either LY545694 (MTMD; as determined during part A) as a simulated, twice daily extended-release formulation for 4 doses over 3days, gabapentin (600mg 8hours apart; 6 doses over 3days; positive control), or matching placebo. The BTS model was induced twice with a 1-hour interval on each of the 2 study days, before drug administration and at the time of expected peak analgesia of LY545694. Plasma exposure for LY545694 was approximately linear over the 25- to 75-mg dose range. The MTMD of LY545694 was 25mg twice daily. Areas of secondary hyperalgesia were significantly smaller after administration of LY545694 and gabapentin compared with placebo (P<.0001 and P=.0004, respectively), but there was no difference between areas after administration of gabapentin and LY545694 (P=.400). Neither gabapentin nor LY545694 reduced the painfulness of skin heating during BTS model induction. The most common treatment-emergent adverse event was dizziness. The results of this study suggest that LY545694 should be explored further as a potential treatment for chronic pain involving neuronal sensitization.

Signal detection and placebo response in schizophrenia: parallels with depression.

OBJECTIVE: Placebo response and the rate of failed clinical trials are increasing in schizophrenia, resembling previous experience with antidepressant clinical trials. In depression, the percent of patients randomized to placebo was shown to be strongly associated with drug-placebo differences (signal detection).We hypothesized that this factor would also be important in recent schizophrenia clinical trials. To test this hypothesis a database of acute schizophrenia placebo-controlled studies conducted between 1997 and 2008 was constructed. The database contained 27 studies, with 79 active treatment arms. As percentage of patients randomized to placebo increased, mean placebo improvement decreased (p = 0.047) and mean drug-placebo differences tended to increase (p = 0.166). The frequency of significant contrasts from studies with ≥ 25% randomized to placebo was 83.3%, compared with 58.3% in studies with <25% randomized to placebo. Caveats to these findings include limited data and confounding of potentially influential factors. These limitations prevent definitive conclusions. However, results are consistent with previous findings in depression where having a higher percent of patients randomized to placebo increased drug-placebo differences.