Evaluation of the Safety, Tolerability, and Efficacy of Orally Administered PTL201 in MS Patients With Spasticity-related Symptoms

The study will be comprised of the following parts: 1. Pharmacokinetics (PK) sub-study: A 7-day baseline observation period. Randomized cross-over treatments (Sativex, PTL201), performed at minimum 7-day washout. Follow up - one week after the last dosing session. 2. Efficacy study: A 7-day baseline observation period. Single-blind responder phase - 4 weeks. Randomized, double-blind, placebo-controlled treatment phase - 4 weeks Follow up - two weeks. Subjects participating in the pharmacokinetic sub-study will be allowed to participate in the efficacy study and will not be required to repeat the 7-day observation period of the efficacy study. Doses will be titrated over a one-week period until reaching maximum tolerated dose (MTD) for each participant The MTD will be self administered for three weeks thereafter. Participants demonstrating response to treatment will continue self administering daily PTL201 treatment or placebo, for an additional four weeks. Participants will keep a daily diary.