STSP-0902 eye drops for neurotrophic keratitis (Phase II)

Inclusion Criteria:

1. Male or female patients aged between 18 to 85 years (inclusive).
2. Diagnosed with NK in one or both eyes, with the study eye classified as Mackie Stage 2 (PED) or Stage 3 (corneal ulcer), and with a maximum corneal defect diameter ≥2 mm.
3. Reduced or absent corneal sensitivity in the defect area and at least 1 adjacent corneal quadrant, confirmed by: ≤40 mm using the aesthesiometer or cotton swab test demonstrating marked reduction or absence of corneal sensitivity.
4. NK duration \>2 weeks in the study eye, as confirmed by the investigator based on medical history.
5. No improvement in the study eye for ≥7 days prior to randomization.
6. Effective non-pharmacological contraception used by the subject (and partner, if applicable) throughout the trial and for 3 months after the last dose, with no plans for pregnancy or gamete donation.
7. Voluntarily sign informed consent, with willingness and ability to comply with study procedures, follow-ups, and assessments.

Exclusion Criteria:

1. Any eye with corneal stromal ulceration involving \>1/3 of corneal thickness or at risk of corneal melting/perforation.
2. Active infection (bacterial, viral, fungal, amoebic, chlamydial) in any eye, or active ocular inflammation unrelated to NK.
3. Study eye with other ocular diseases requiring topical medication apart from the prescribed adjunctive treatments during the trial.
4. Bilateral vision loss severely impacting daily life, as assessed by the investigator.
5. Study eye with Schirmer I test ≤3 mm/5 minutes.
6. Severe lagophthalmos, eyelid margin disease, or meibomian gland dysfunction in the study eye that may impair corneal healing or trial outcomes.
7. Study eye with any surgery within 3 months prior to randomization (including corneal/non-corneal surgeries affecting trial assessments, except surgeries related to NK etiology), or planned ocular surgery during the trial.
8. Study eye with prior surgical intervention for NK (e.g., tarsorrhaphy, conjunctival flap) that may confound efficacy assessments, or amniotic membrane transplantation within 6 weeks prior to randomization.
9. Study eye with botulinum toxin injections to the levator muscle within 3 months prior to randomization or planned during the trial.
10. Requirement to wear contact lenses during the trial.
11. History of inefficacy or poor response to nerve growth factor (NGF) eye drops in any eye.
12. Use of autologous serum eye drops, deproteinized calf blood extracts, or other growth factor-containing ocular medications in the study eye(s) planned during the trial.
13. Use of NSAIDs, or corticosteroids in the study eye within 1 week prior to randomization or planned during the trial.
14. Use of neurotoxic drugs (e.g., antipsychotics, antiepileptics, antihistamines) or systemic immunosuppressants within 4 weeks prior to randomization or planned during the trial, excluding those who have been using it stably for at least 4 weeks before enrollment.
15. Poorly controlled systemic or ocular conditions (e.g., diabetic retinopathy, uveitis, autoimmune diseases, malignancies, psychiatric disorders) that may confound efficacy assessments or compliance, as judged by the investigator.
16. Known hypersensitivity to the study drug, its excipients, or components of trial-related ophthalmic tests (e.g., fluorescein).
17. History of drug abuse or alcohol dependence.
18. Participation in another interventional trial (drugs, devices, or vaccines) within 3 months prior to randomization or planned during this trial.
19. Female subjects who are pregnant, breastfeeding, or test positive for serum pregnancy; or who are failure to use effective contraception for 2 weeks prior to screening, during the trial, or for 3 months post-dosing.
20. Difficulty administering eye drops, venous blood sampling, or history of needle phobia/vasovagal syncope.
21. Any other condition deemed unsuitable for trial participation by the investigator.