Efficacy Study With AFA-281 for the Treatment of Back Pain

The goal of this clinical trial is to evaluate if the drug candidate AFA-281 works to treat chronic low back and leg pain caused by painful lumbosacral radiculopathy (PLSR) in adults. This trial will also evaluate the safety of AFA-281. The main questions it aims to answer are: * Does AFA-281 mitigate pain? * What are the side effects (if any)? Researchers will compare AFA-281 to a placebo (a look-alike substance that contains no drug) to see if AFA-281 works to treat chronic low back and leg pain. Participants will: * Take drug AFA-281 or a placebo three times every day for 4 weeks * Visit the clinic once every 2 weeks for checkups and tests * Keep a diary of their pain scores and about mood and sleep questionnaires, and the number of times they use a rescue pain medicines.