Pain Intensity Numerical Rating Scale: 0 = no pain & 10 = worst possible pain
Zalicus is using (PI-NRS) to measure Z160's pain reduction. On this scale, 0 = no pain & 10 = worst possible pain.
Pfizer Global R&D says a 2 point reduction on this pain scale is clinically relevant. As Dr. Corrigan said, the Placebo Effect is real, and it results in a 1 point pain scale reduction.
Can Z160 achieve 2 points of pain reduction to beat the placebo? On average, a reduction of approximately 2 points on the PI-NRS is a clinically important difference.
Keep in mind, Z160 should theoretically already be equivalent to placebo unless it somehow interferes with the biochemical basis of the placebo effect. Barring this, Z160 has the placebo effect on its side and just has to reduce pain by an additional 1 point.
Without side effects, if Z160 has any effects at all, I think it can achieve 1 additional point beyond placebo.