This is a randomized, double-blind, multi-center phase II/III study to evaluate the efficacy and safety of Recombinant Botulinum Toxin Type A (YY001) for injection in the treatment of upper limb spasticity in adults

Inclusion Criteria:

1. Age between 18 and 75 years old inclusive, at the time of signing the informed consent, regardless of gender.
2. Subjects with unilateral hemiplegia due to stroke (with a time interval of ≥ 3 months from stroke onset to randomized enrollment) exhibiting upper limb spasticity.
3. Subjects with Disability Assessment Scale score of at least 2 on the Principal Target of Treatment (one of four functional domains: hygiene, dressing, limb position and pain).
4. If taking oral antispasticity, the dosage must be stable for at least 1 month prior to randomized enrollment.
5. If the study limb receives physical therapy or occupational therapy, the frequency, type, and intensity must be stable for at least 3 weeks prior to randomized enrollment.

Exclusion Criteria:

1. History of allergy to any component of the experimental drugs.
2. Previous use of any botulinum toxin within 6 months prior to randomized enrollment, or plan to use other botulinum toxins not specified in the study protocol during the study.
3. Fixed contractures of the studied limb.
4. Any medical condition that may increase the risk to the subject when using Botulinum Toxin Type A.
5. Need for treatment with drugs that interfere with neuromuscular function during the study.
6. Plan or anticipate to use new antispasticity drugs during the study.
7. History of epilepsy.
8. Pregnant or breastfeeding women.
9. Participation in other drug/device clinical trials within 1 month prior to randomized enrollment.

Double-blind