Part A of this study is a double-blind, randomized, placebo-controlled, single ascending dose study of intravenous administration of LAT8881 over 5 minutes in healthy volunteers. Eight participants will be enrolled. Each participant has three treatment days, 1 infusion per dosing day, on Days 1, 4 and 7 as well as two short visits for safety blood sampling on Days 3 and 6. Participants are randomised, so on each treatment day, 6 participants receive LAT8881 and 2 receive placebo (different participants to receive placebo each treatment day). LAT8881 doses administered are 0.8 mg/kg on Day 1, 1.2 mg/kg on Day 4 and 1.8 mg/kg on Day 7.~Part B of this study is is a placebo-controlled randomized double blind cross-over safety and efficacy study of LAT8881 in up to 20 patients with lumbar radicular pain. Participants will be randomly assigned to one of two groups, to receive either LAT8881 then placebo or placebo then LAT8881. Participants will receive a either single dose of LAT8881 [the Maximum Tolerated Dose from Part A of the study] or placebo via intravenous administration over 5 minutes on two consecutive days.
The study consists of two parts. Part A will evaluate the safety and tolerability of intravenous LAT8881 in healthy volunteers using an ascending dose schedule. Part B will evaluate the analgesic efficacy of a single intravenous dose of LAT8881, compared with placebo, in patients with lumbar radicular pain.~Healthy volunteers are not accepted for Part B.