This is a seamless Phase I/II, randomized, double-masked, placebo-controlled, multicenter trial to evaluate single and multiple-dose safety and tolerability of SUM-191 in healthy participants in Parts 1 (SAD) and 2 (MAD) ; and multiple-dose efficacy and safety of SUM-191 in participants with bacterial conjunctivitis in Part 3.

Inclusion Criteria:

1. The participant is able to provide signed and dated, written informed consent prior to any trial specific procedures.

2. The participant understands and is able and willing to fully comply with trial procedures and restrictions.

3. The participant is a male or non-pregnant, non-lactating female who agrees to comply with any applicable contraceptive requirements of the protocol, or is a female of non-childbearing potential.

4. The male participant must agree not to donate sperm 90 days after last dose of IP and female participant must agree not to donate egg 30 days after last dose of IP.

5. The participant is willing to discontinue wearing a contact lens for the duration of the trial.

   Additional criteria for Parts 1 and 2:

6. The participant is a healthy male or female, aged 18 years and older.

7. The participant has triglyceride levels less than 150 mg/dL at Screening.

8. The participant is considered by the investigator to be in good general health as determined by medical history, clinical laboratory test results, vital signs, 12-lead ECG results, and physical examination findings at Screening and Day -1.

   Additional criteria for Part 3:

9. The participant is a male or female, aged 18 years and older.

10. The participant has a clinical diagnosis of bacterial conjunctivitis in at least one eye.

11. The participant has a BCVA of 20/200 Snellen equivalent or better in each eye as per standard of care assessment.

Exclusion Criteria:

1. The participant has a current or recurrent disease that could affect the action, absorption, or disposition of the IP, or clinical or laboratory assessments, per investigator's discretion.

2. The participant has a current or relevant history of physical or psychiatric illness, any medical disorder that may make the participant unlikely to fully complete the trial, or any condition that presents undue risk from the IP or procedures.

3. The participant has any current active infections (except bacterial conjunctivitis in Part 3), including localized infections, or any recent history (within 1 week prior to IP administration) of infections (including SARS-CoV-2), cough or fever, herpes, or a history of recurrent or chronic infections.

4. The participant has any clinically important illness, medical/surgical procedure, or trauma within 2 weeks of the first administration of IP or planned surgical procedure during the trial period.

5. The participant has a known or suspected intolerance or hypersensitivity to the IP, closely related compound, any of the stated ingredients or its vehicle.

6. The participant has any history of or active sign of any intraocular inflammation in either eye caused by autoimmune or systemic etiology OR has an active or one month prior to Check-in for Parts 1 and 2 and Visit 1 for Part 3, an infectious or allergy-induced intraocular inflammation in either eye.

7. The participant has a presence of corneal abrasion or corneal ulcer in either eye.

8. The participant has any presence of blepharoconjunctivitis in either eye.

9. The participant has an active or a history of ocular herpes (including herpetic corneal ulcer and ophthalmic herpes zoster) in the eye(s) that will receive IP.

10. The participant has a history of recurrent corneal erosion syndrome, either idiopathic or secondary to previous corneal trauma or severe dry eye syndrome or presence of corneal epithelial defect or any significant corneal opacity at Screening or at Day 1 (predose) in Parts 1 and 2 and at Visit 1 in either eye.

11. The participant has nasolacrimal duct obstruction or dacryocystitis at Screening or Day -1 in Parts 1 and 2 and at Visit 1 in Part 3, in the eye(s) that will receive IP.

12. The participant has a history of any ocular surgeries within 3 months prior to Day -1 in Parts 1 and 2 and Visit 1 in the eye(s) that will receive IP.

13. The participant has a significant, active condition of the retina requiring treatment in either eye during the trial.

14. The participant has an uncontrolled glaucoma defined as IOP ≥25 mmHg despite maximal medical therapy in either eye.

15. The participant has used any topical ocular or systemic antibiotics within 72 hours of the first dose in either eye.

16. The participant has used any topical ocular or systemic anti-inflammatory agents within 72 hours of the first dose in either eye.

17. The participant has any significant ocular disease (eg, Sjogren's syndrome) or any uncontrolled systemic disease or debilitating disease (eg, cardiovascular disease, hypertension, sexually transmitted diseases/infections, diabetes, or cystic fibrosis), that may affect the trial parameters, per investigator's discretion.

18. The participant has any known history of immunodeficiency disorder or known active conditions predisposing to immunodeficiency, such as human immunodeficiency virus, hepatitis B or C, or organ or bone marrow transplantation.

19. The participant has used any IP within 30 days or 5 half-lives, whichever is longer, prior to the first dose of IP.

20. The participant has been enrolled in a clinical trial (including vaccine studies) that, in the investigator's opinion, may impact this trial.

21. The participant is involved in the planning and/or conduct of the trial (applies to the sponsor, contract research organizations, and trial center staff, etc).

22. The participant has a positive test result for hepatitis B surface antigen, hepatitis B core antibody, hepatitis C virus antibody, hepatitis A (antihepatitic A virus IgM), or human immunodeficiency virus types 1 or 2 antibodies at Screening (Part 1 and Part 2).

23. The participant is an active smoker or has used nicotine or nicotine-containing products (eg, snuff, nicotine patch, nicotine chewing gum, mock cigarettes, or inhalers) within 6 months before IP dosing (Part 1 and Part 2).

24. The participant has a history of alcohol abuse or drug addiction within the last year or excessive alcohol consumption (regular alcohol intake >14 units per week for male participants and 7 units of alcohol per week for female participants (1 unit is equal to approximately ½ pint [200 mL] of beer, 1 small glass [100 mL] of wine, or 1 measure [25 mL] of spirits) 6 months prior to Screening in Parts 1 and 2.

25. The participant has a positive test result for drugs of abuse, alcohol, or cotinine (indicating active current nicotine use/exposure) at Screening or Day -1 in Parts 1 and 2.

26. The participant has donated blood or blood products >450 mL within 30 days before IP dosing.

27. Male participant with a QTcF >450 ms or female participants with a QTcF >470 ms at Screening or on Day -1 safety ECG in Parts 1 and 2.

    Additional exclusion criteria for Part 3:

28. The participant has a positive test result for drugs of abuse at Visit 1.

29. The participant has a positive result of a rapid adenovirus test at Visit 1.

30. The participant has a previous treatment for current bacterial conjunctivitis.