This is a double-blind, randomized, 4-way crossover, pharmacokinetic and pharmacodynamic (PK/PD) study to compare the cutaneous vasoreactive intensity to intradermal injections of Substance P in healthy volunteers receiving oral doses of 20 mg, 50 mg or 100 mg VLY-686 or a matching placebo. Twelve healthy male subjects satisfying the selection criteria for the study will be enrolled. Each subject will participate in a screening period (up to 21 days prior to dosing), four one-day treatment periods each separated by a 7 (±2 days) day washout period, and an end-of-study evaluation prior to discharge from the study. This protocol also includes an option of subjects administered daily doses of study medication between Periods 3 and 4. The treatment periods will be in a randomized sequence consisting of 1) 20 mg VLY-686, 2) 50 mg VLY-686, 100 mg VLY-686 and 4) placebo. In each of the study periods, Substance P will be injected 5 times: pre-dose (the night before), 2, 4, 8 and 12 hours (± 10 minutes) after study medication administration. A dose of 100 μL of a 2.5 nmol/mL sterile solution of Substance P will be injected each time. Overall, subjects will be administered 1.25 nmol of Substance P in around 24 hours (5 doses). Substance P injections will be given in the volar of the forearm, alternating right and left and avoiding injections in an area adjacent to the area previously injected. The subject's forearm will be covered during and after each injection to avoid potential biases in the scoring of the Verbal Rating Scale (VRS) and Visual Analog Scale (VAS). Additionally, blood samples for VLY-686 pharmacokinetic (PK) analysis will be collected each period at pre-dose, 1, 3, 6, 10, and 24 hours after study medication administration.