The efficacy of QUTENZA was established in two 12-week, double-blind, randomized, dose-controlled, multicenter clinical trials. These studies enrolled patients with postherpetic neuralgia (PHN) persisting for at least 6 months following healing of herpes zoster rash and a baseline score of 3-9 on an 11-point Numerical Pain Rating Scale (NPRS) ranging from 0 (no pain) to 10 (worst possible pain). QUTENZA and a control topical system were each applied as a single, 60-minute application. The control used in these studies looked similar to QUTENZA but contained a low concentration of the active ingredient, capsaicin (3.2 mcg/cm2, 0.04% w/w), to retain blinding regarding the known application site reactions of capsaicin (such as burning and erythema). The baseline mean pain score across the 2 studies was approximately 6.0. Patients who entered the study on stable doses of pain-control medications were required to keep dosing stable throughout the duration of the study. Approximately half of the patients were taking concomitant medications, including anticonvulsants, non-SSRI antidepressants, or opioids for their PHN at study entry. Prior to application, a topical anesthetic was applied to the treatment area for 60 minutes. Patients were permitted to use local cooling and additional analgesic medications for treatment-related discomfort as needed through Day 5. Patients recorded their pain daily in a diary.

PHN Study 1: In this 12-week study, the QUTENZA group demonstrated a greater reduction in pain compared to the control group during the primary assessment at Week 8. The percent change in average pain from baseline to Week 8 was -18% (±2%) for the low-dose control and -29% (±2%) for QUTENZA.

For various degrees of improvement in pain from baseline to study endpoint, Figure 2 shows the fraction of patients achieving that degree of improvement. The figure is cumulative, so that patients whose change from baseline is, for example, 50%, are also included at every level of improvement below 50%. Patients who did not complete the study through Week 12 or who showed no improvement at Week 12 were assigned 0% improvement. Some patients experienced a decrease in pain as early as Week 1, which persisted throughout the study. The proportion of patients experiencing ≥30% reduction in pain intensity from baseline for each week through Week 12 is shown in Figure 3.

FIGURE 2: Patients Achieving Various Percentages of Reduction in Pain Intensity at Week 12 – Study 1

FIGURE 3: Weekly Proportion of Patients Achieving ≥30% Pain Intensity Reduction – Study 1*

PHN Study 2: In this 12-week study, the QUTENZA group demonstrated a greater reduction in pain compared to the control group during the primary assessment at Week 8. The percent change in average pain from baseline to Week 8 was -26% (±2%) for the low-dose control and -33% (±2%) for QUTENZA.

For various degrees of improvement in pain from baseline to study endpoint, Figure 4 shows the fraction of patients achieving that degree of improvement. The figure is cumulative, so that patients whose change from baseline is, for example, 50%, are also included at every level of improvement below 50%. Patients who did not complete the study through Week 12 or who showed no improvement at Week 12 were assigned 0% improvement. Some patients experienced a decrease in pain as early as Week 1, which persisted throughout the study. The proportion of patients achieving ≥30% reduction in pain intensity from baseline for each week through Week 12 is shown in Figure 5.

FIGURE 4: Patients Achieving Various Percentages of Reduction in Pain Intensity at Week 12 – Study 2

FIGURE 5: Weekly Proportion of Patients Achieving ≥ 30% Pain Intensity Reduction – Study 2*