• Participant must be 18 to 70 years of age inclusive (except for dose escalation must be 18 to 65 years of age) at the time of signing the informed consent.

• Has spastic hemiparesis following stroke or Traumatic brain injury (TBI)

• Is at least 6 months post-stroke or TBI

• Has never received BoNT or if previously treated, should have received their last injection of any commercialized BoNT-A or B at least 4 months prior to study Baseline

• Has a MAS score ≥2 in the (PTMG) to be injected

• Is eligible to receive a total recommended dose 1000 U Dysport in the upper limb when applicable.

• Has angle of spasticity ≥5° in the PTMG to be injected.

• Does not have any fixed contractures as defined by:

‣ Complete fingers extension with Angle of arrest at slow speed (Tardieu Scale) (XV1) ≥160°

⁃ Complete wrist extension with XV1 ≥90°

⁃ Complete elbow extension with XV1 ≥160°

• Physiotherapy, occupational therapy, splinting, use of benzodiazepine, and muscle relaxants had to be stable from at least 30 days preceding the study Baseline up to the Month 3 visit, and whenever possible until the end of the study.

⁃ In good health (i.e. absence of any uncontrolled systemic disease or other significant medical condition) as determined by medical history, physical and neurological examinations, clinical laboratory studies, electrocardiograms (ECGs), vital signs, and Investigator's judgment prior to randomization

⁃ Male and female participants Contraceptive use by men or women should be consistent with local regulations regarding the methods of contraception for those participating in clinical studies.

∙ Male participants must agree that, if their partner is at risk of becoming pregnant, they will use an effective method of contraception. The participants must agree to use the contraception during the whole period of the study.

∙ A female participant is eligible to participate if she is not pregnant or breastfeeding, and one of the following conditions applies: Is a woman of non-childbearing potential (WONCBP) or is a woman of childbearing potential (WOCBP) and using an acceptable contraceptive method (until the end of the study). The investigator should evaluate the potential for contraceptive method failure in relationship to the first dose of study intervention. A WOCBP must have a negative highly sensitive pregnancy test.