Evaluation of the Effectiveness of ST266 Ophthalmic Drops Compared to Placebo to Treat Allergic Conjunctivitis

The study is a multi-center, double-masked, randomized, placebo-controlled, modified
conjunctival allergen challenge (CAC) model. The primary endpoints of ocular itching and
conjunctival redness will be evaluated at the subject's final visit. Subjects who meet
inclusion criteria will be randomized to one of two treatment groups (1:1). Randomization
will be stratified by average post-CAC itching scores at baseline.

Subjects will be evaluated at baseline and on Days 6, 7 and 8.

Inclusion Criteria:

- be at least 18 years of age of either gender and any race;

- provide written informed consent and sign the HIPAA form;

- be willing and able to follow all instructions and attend all study visits; have a
positive history of ocular allergies and a positive skin test reaction to a seasonal
AND perennial allergen as confirmed by an allergic skin test;

- be able and willing to avoid all disallowed medication for the appropriate washout
period and during the study;

- be able and willing to discontinue wearing contact lenses for at least 72 hours prior
to and during the study trial period;

- (for females capable of becoming pregnant) agree to have urine pregnancy testing
performed at screening (must be negative) and at the study exit; must not be
lactating; and must agree to use a medically acceptable form of birth control
throughout the study duration and for at least 14 days prior to instillation of
investigational product). Women considered capable of becoming pregnant include all
females who have experienced menarche and have not experienced menopause (as defined
by amenorrhea for greater than 12 consecutive months) or have not undergone successful
surgical sterilization (hysterectomy, bilateral tubal ligation, or bilateral
oophorectomy);

- have a calculated visual acuity of 0.7 logMAR or better in each eye as measured using
an ETDRS chart;

- have a positive post-CAC reaction;

- have a positive post-CAC reaction in two out of the first three time points;

- be able to self-administer eye drops satisfactorily or have a caregiver at home
routinely available for this purpose.

Exclusion Criteria:

- have known contraindications or sensitivities to the use of the investigational
product or any of its components;

- have any ocular condition that, in the opinion of the investigator, could affect the
subject's safety or trial parameters (including but not limited to narrow angle
glaucoma, clinically significant blepharitis, follicular conjunctivitis, iritis, or
pterygium);

- have had ocular surgical intervention within 3 months prior to initiating the study or
during the study and/or a history of refractive surgery within the past 6 months;

- have a known history of retinal detachment, diabetic retinopathy, or active retinal
disease;

- have the presence of an active ocular infection (bacterial, viral or fungal) or
positive history of an ocular herpetic infection at any visit;

- use any of the disallowed medications during the period indicated prior to and during
the study;

- have any significant illness (e.g. any autoimmune disease requiring therapy, severe
cardiovascular disease [including arrhythmias]) the investigator feels could be
expected to interfere with the subject's health or with the study parameters and/or
put the subject at any unnecessary risk (includes but is not limited to: poorly
controlled hypertension or poorly controlled diabetes, a history of status
asthmaticus, organ transplants, a known history of persistent moderate or severe
asthma, or a known history of moderate to severe allergic asthmatic reactions to any
of the study allergens);

- manifest signs or symptoms of clinically active allergic conjunctivitis in either eye
at the screening visit;

- have planned surgery (ocular or systemic) during the trial period or within 30 days
after;

- have used an investigational drug or medical device within 30 days of the study or be
concurrently enrolled in another investigational product trial;

- be a female who is currently pregnant, planning a pregnancy, or lactating.

- have cancer or have a history of cancer within the last 5 years.