Phase 2a Topical Sildenafil Proof-of-Concept Study in Men With Mild to Moderate ED

Initial Patient Eligibility: Visit 1 (Day 1) After the patient provides written informed
consent, the initial screening procedures will be performed. Patients who meet all
eligibility criteria will be instructed on completion of the SEP Diary, the need for a one
week washout of any ED medications before starting the Off-Site 4-Week Run-In Period and that
the use of any ED medications will be prohibited throughout the entire 4-week duration and up
until the completion of Visit 5. Site staff will contact patients by phone between 4 and 7
days following Visit 1 (on Days 4- 7) to communicate eligibility (met laboratory parameters
and the one week washout) to participate in the Off-Site 4-Week Run-In Period. Site staff
will also schedule the Topical Placebo RigiScan Qualification Visit (Visit 2) to be within
two days of completion of the 4-Week Run-In Period for eligible patients. Ineligible patients
will be instructed to discard their SEP Diary and will be discontinued from further study
participation Off-Site 4-Week Run-In Period (Day 8-35) Eligible patients will participate in
an Off-Site 4-Week Run-In Period during which time they will attempt intercourse a minimum of
4 times. Use of any ED medications will be prohibited throughout the entire 4-week duration
and up until the completion of Visit 5. Patients will be asked to maintain a Sexual Encounter
Profile (SEP) diary during the 4-Week Run-In Period to be completed after each intercourse
attempt.

Topical Placebo RigiScan Qualification: Visit 2 (Day 36 [+ 2 days]) Patients who successfully
complete the 4-Week Run-In will be instructed to complete the IIEF questionnaire at the
beginning of Visit 2. Eligible patients must have documented mild-moderate ED as demonstrated
by a score of 11-21 in the International Index of Erectile Function (IIEF) Erectile Function
domain of the IIEF questionnaire.

Eligible patients will then complete a single-blind (patient) 60 minute plethysmography
procedure using placebo cream to familiarize patients with the plethysmography device (i.e.
RigiScan) and evaluate the placebo response with Visual Sexual Stimulation (VSS).

Patients who demonstrate a topical placebo response (i.e. achieve an erection of ≥ 60%
rigidity at the base of the penis for a cumulative duration of > 4 minutes) will be
ineligible for further study participation. Any patients with an adverse dermatologic
reaction to the placebo cream will be excluded from further participation in the study but
will be followed until normalization of symptoms.

Safety data for all patients, regardless of continued eligibility, will be included in the
database as patients will have been exposed to IP (placebo cream only) during this visit.
There will be a 7 (± 1) day washout period between Visits 2 and 3.

Oral Sildenafil RigiScan Qualification: Visit 3 (Day 43 [± 2 days]) Patients who meet the
eligibility criteria will then complete the Oral Sildenafil RigiScan Qualification visit,
consisting of a single-blind (patient) plethysmography procedure with 60 minutes of VSS to
evaluate the patient's response to oral sildenafil.

Patients who do not respond to oral sildenafil (i.e., do not achieve ≥ 60% rigidity at the
base of the penis for a cumulative duration of >15 minutes and an EHS Score of 3 or 4) will
be excluded from further study participation.

There will be a 7 (± 1) day washout period between Visit 3 and Visit 4 (i.e., the first visit
in the SST-6006/Placebo Double-Blind Dosing Phase).

SST-6006/Placebo Double-Blind Dosing Phase: Visits 4 & 5 (Days 50 and 57 [± 2 days]) Eligible
patients will be randomized to a sequence of dosing (i.e., placebo cream then SST-6006 or
SST-6006 then placebo cream). The SST-6006/Placebo Double-Blind Dosing Phase will consist of
two plethysmography procedures with 60 minutes of VSS. One will evaluate the patient's
response to SST-6006 and the other will evaluate the patient's response to placebo cream.
Patients will be instructed to complete a 4-Point Erection Hardness Scale (EHS) immediately
following completion of the plethysmography procedure at each visit. There will be a 7 (± 1)
day wash-out between Visit 4 and Visit 5.

Inclusion Criteria:

1. Patient is a heterosexual male ≥ 18 and ≤ 70 years of age.

2. Patient has had a clinical diagnosis of erectile dysfunction for a minimum of 6
months.

3. Patient has a body mass index (BMI) from 18 to 30 kg/m², inclusive.

5. Patient is capable of understanding and complying with the protocol and agrees to sign
the informed consent document.

6 Patient agrees to use condoms with sexual activity for 7 days immediately following each
visit that involves application of SST-6006 or placebo cream (i.e. Visit 2, Visit 4 and
Visit 5).

7. Patient has a testosterone level ≥ 300 ng/dL (either naturally or through androgen
replacement therapy; if on androgen replacement therapy, must have been taking for ≥ 6
months).

8. Patient is willing to undergo plethysmography procedure with VSS during the trial

Exclusion Criteria:

Subject is unfamiliar with or unwilling to watch visual sexual stimulation (VSS).

2. Subject has any disorder or a history of any disorder that may prevent the successful
completion of the study.

3. Subjects with an abnormal physical exam, that in the opinion of the Investigator, would
interfere with study participation.

4. Subject has a significant cardiovascular, hepatic, renal, respiratory, gastrointestinal,
endocrine, immunologic, dermatologic, hematologic, neurologic, genitourinary, or
psychiatric disease or other unstable medical condition that would contraindicate
administration of study medication, interfere with study evaluation, limit study
participation, contraindicate sexual activity, or confound the interpretation of study
results.

5. Subject has an active ulcer or clinically significant bleeding disorder. 6. Subject has
a history of myocardial infarction, stroke, or life-threatening arrhythmia within 6 months
prior to Visit 1; a history of coronary disease causing angina; or congestive heart failure
requiring medical intervention.

7. Subject has uncontrolled hypertension or untreated hypertension. 8. Subject has a
history of orthostatic hypotension or orthostatic hypotension.

9. Subject is unable to walk up and down two flights of stairs briskly without chest pain.

10. Subject is using alpha blockers. 11. Subject is using or has possession of nitrate
containing medication(s). 12. Subject has retinitis pigmentosa or sickle cell anemia or
related anemias, even if the subject feels clinically well at the time of screening.
Subjects with retinitis pigmentosa will be identified by specifically asking whether they
have the condition, if there are visual signs and symptoms of the condition (including
questioning subjects as to whether they have difficulty seeing at night or in low light,
and if they have any visual field deficits that indicate a loss of peripheral or central
vision), or if there is a family history.

13. Subject has anatomical deformation of the penis such as angulation, cavernosal
fibrosis, or Peyronie¡-s disease, or history of genital surgery.

14. Subject has a history of prostate surgery. 15. Subject has a history of pelvic
radiation. 16. Subject has type 1 or type 2 diabetes. 17. Subject has a history of cancer
other than basal cell carcinoma. 18. Subject has any surgical or medical condition that may
interfere with the absorption, distribution, metabolism, or excretion of the test article.

19. Subject has a history of drug abuse within 1 year before Visit 1. 20. Subject has a
history of alcoholism within 1 year before Visit 1, admitted alcohol abuse, or has an
average consumption of more than 2 standard units of alcohol per day (a standard unit
equals 12 ounces of beer, 1¨ö ounces of 80-proof alcohol, or 6 ounces of wine).

21. Subject has had treatment currently or within 1 month (28 days) of Visit 1 with any of
the following: weak, moderate, and strong inhibitors and inducers of CYP3A4 and CYP2C9
enzymes (e.g., CYP3A4: ketoconazole, clarithromycin, verapamil, diltiazem, St. John¡-s Wort
/ CYP2C9: fluconazole, oxandrolone, fluvastatin, and metronidazole). Any prescription,
over-the-counter (OTC) medications, or herbal products taken recently or currently being
taken will be screened by study personnel prior to study enrollment to confirm such drugs
do not inhibit or induce the two enzymes listed above. If the subject takes any
prescription or OTC drugs at the direction of a health care provider that are inhibitors or
inducers of CYP3A4 and CYP2C9, that provider should be consulted before medications are
stopped for the purposes of study participation.

22. Subject is unwilling to refrain from using any medication for erectile dysfunction,
with the exception of study medication, after Visit 1 and throughout the duration of the
study up until the completion of Visit 5.

23. Subject has positive findings from urine drug screen (e.g., amphetamines, barbiturates,
benzodiazepines, cannabinoids, cocaine, methadone, and opiates).

24. Subjects with a positive alcohol breath test. 25. Subject participated in any clinical
research study evaluating another investigational drug or therapy within 30 days before the
Visit 1.

26. Subject is unwilling to refrain from ingesting grapefruit, grapefruit-containing
products, Seville oranges, or products containing Seville oranges (e.g., orange marmalade)
three days prior to each dosing visit.

27. Subject has any skin breaks, irritation, dermatoses, or lesions in the penile area to
which the study cream will be applied.

28. Subject has a known hypersensitivity or allergy to any of the ingredients in the IP.

29. Subject has a significant cardiovascular, hepatic, renal, respiratory,
gastrointestinal, endocrine, immunologic, dermatologic, hematologic, neurologic,
genitourinary, or other unstable medical condition indicated by the laboratory results that
would contraindicate administration of study medication, interfere with study evaluation,
limit study participation, contraindicate sexual activity, or confound the interpretation
of study results.

30. Subjects who have abnormal laboratory parameters that, in the opinion of the
Investigator, could confound interpretation of the study results.

31. Subjects who have positive serology findings for a sexually transmitted infection (i.e.
syphilis, gonorrhea, chlamydia, HIV antibodies, hepatitis b surface antigen (HBsAg) or
hepatitis c (HCV) antibodies.

32. Subjects with abnormal vital signs and/or ECG results that, in the opinion of the
Investigator, would affect the interpretation of study results.