BX-1 in Spasticity Due to Multiple Sclerosis

Inclusion Criteria: 1. Male or female patients aged 18 to 65 years 2. Presence of MS according to 2010 or 2017 revised McDonald criteria 3. Patients with stable MS for at least 3 months before enrolment in the opinion of the treating physician Note: Patients with a MS relapse during 3 month prior to enrolment are not considered to have stable MS 4. Ongoing spasticity for at least 3 months before enrolment 5. Spasticity in at least 2 lower limb muscles 6. Expanded Disability Status Scale (EDSS) score ≥ 3.0 and ≤ 6.5 7. Previous treatment with at least two different optimized oral MS anti-spasticity therapies before inclusion. Both treatment attempts must include at least baclofen or oral tizanidine, which can be combined with other anti-spasticity drugs. AND Patients currently receiving an optimized treatment corresponding to the last treatment attempt with stable dosage for at least 30 days prior to Visit 0. 8. Female patients of non-childbearing potential or if of childbearing potential using highly effective contraceptive methods or double barrier contraception. For men: no specific contraception methods need to be used. 9. Willingness to follow the study procedure for the whole duration of the trial and signed informed consent at screening prior to any trial-related procedure Exclusion Criteria: 1. Any present disease other than MS that could affect spasticity (e.g. traumatic brain injury, spinal cord injury, brain damage due to a lack of oxygen, stroke, encephalitis, meningitis) 2. Intake of not permitted concomitant medication prior to screening and concomitant medication which should be unaltered prior to screening in an unstable dosage regimen 3. Significant fixed tendon contractures 4. History of epileptic seizures 5. History of or existing relevant CNS disorder (other than MS) 6. History of or existing relevant psychiatric disorders (e.g. schizophrenia, psychosis, manic disorders, severe depressive disorders, suicidal ideations, drug and/or alcohol abuse etc.) 7. Patients with a positive drug abuse screening test, except for medications used to treat a medical condition and reported as such by the patient; all patients with a positive result for cannabis/THC 8. History of or existing cardiac diseases or pathological findings (e.g. chronic insufficiency NYHA III/IV, severe arrhythmia, unstable angina pectoris, myocardial infarction within the past 6 months, QT prolongation) 9. Known HIV, and/or active Hepatitis B or C infection 10. History of or existing malignancy during the 5 years before screening except history of basal cell carcinoma and melanoma in situ 11. Significantly impaired renal function (estimated Glomerular Filtration Rate (eGFR) \< 60 mL/min/1.73m2) 12. Significant impaired hepatic function (Alanine Aminotransferase \> 3 times upper limit of normal or bilirubin \> 2 times upper limit of normal, except Gilbert syndrome) 13. Known allergic reactions to the active ingredients used or to constituents of the IMP 14. Chronic or active infection requiring a systemic therapy 15. Pregnancy, breastfeeding or planned pregnancy 16. Any condition that interferes with the participation in the clinical trial at the discretion of the investigator 17. Patients not able to follow study instructions, not able to follow the study assessments defined by the protocol, unable to understand the written and verbal instructions, in particular regarding the risks and inconveniences they will be exposed to during their participation in the clinical trial 18. Patients in custody by judicial or official order 19. Patients who are members of the staff of the trial centre, staff of the sponsor or CRO, the investigator him/herself or close relatives of the investigator 20. Parallel participation in another clinical trial, participation in another trial within less than 30 days or five half-lives of IMP (whatever is longer) to screening, or previous participation in this trial (except one time screening failures). A patient may be re-screened once, if any inclusion criterion is not met or any exclusion criterion is met during the first screening attempt.