A Study of Varlilumab (Anti-CD27) and Ipilimumab and CDX-1401 in Patients With Unresectable Stage III or IV Melanoma

Varlilumab is a fully human monoclonal antibody that binds to a molecule called CD27 found
on certain immune cells and may act to promote anti-tumor effects.

Yervoy™ (Ipilimumab) is a human monoclonal antibody that blocks CTLA-4, a protein receptor
that downregulates the immune system.

CDX-1401 is a vaccine made of a fully human monoclonal antibody linked to NY-ESO-1 and is
designed to deliver NY-ESO-1 to professional antigen presenting cells for generating robust
immune responses against cancer cells expressing NY-ESO-1. CDX-1401 is administered with
poly-ICLC, an adjuvant that enhances vaccine-induced immune responses.

This study will evaluate the safety, tolerability and efficacy of varlilumab and ipilimumab,
with or without the addition of CDX-1401/poly-ICLC, in patients with melanoma.

Eligible patients that enroll in the Phase I portion of the study will be assigned to one of
two possible dose levels of varlilumab in combination with 3 mg/kg ipilimumab. The first
phase of the study will test the safety profile of the combination and determine which dose
of varlilumab will be studied in Phase II of the study.

During Phase II, up to 48 patients whose tumors do not express NY-ESO-1, will receive the
recommended dose of varlilumab determined from Phase I with 3 mg/kg ipilimumab. Up to 24
patients whose tumors express NY-ESO-1 will receive the recommended dose of varlilumab
combined with 3 mg/kg ipilimumab and 1 mg CDX-1401 along with 2 mg poly-ICLC.

All patients enrolled in the study will be closely monitored to determine if there is a
response to the treatment as well as for any side effects that may occur.

Key Inclusion Criteria:

1. Histologic diagnosis of melanoma.

2. Unresectable Stage III or IV disease

3. Documented progressive disease based on radiographic, clinical or pathologic
assessment.

4. No more than three prior anticancer regimens (BRAF/MEK inhibitors, IL-2 or
investigational agents) including no more than one chemotherapy-containing regimen
for advanced (recurrent, locally advanced or metastic) disease.

5. Measurable disease.

6. Life expectancy ≥ 12 weeks.

7. If of childbearing potential (male or female), agrees to practice an effective form
of contraception during study treatment and for at least 70 days following last
treatment.

8. Availability of tumor tissue for central laboratory analyses.

Key Exclusion Criteria:

1. Previous treatment with anti-CD27 antibody, ipilimumab or other anti-CTLA-4 targeted
therapies. Previous therapy with other checkpoint blockers such as anti-PD-1 or
anti-PD-L1 is acceptable, unless treatment was discontinued for intolerance.

2. For patients enrolled to Phase II Cohort B: Previous administration of vaccine
therapy targeting NY-ESO-1.

3. BRAF/MEK inhibitors within 2 weeks prior to first dose of study treatment.

4. Chemotherapy within 21 days or at least 5 half-lives (whichever is shorter) prior to
first dose of study treatment.

5. Monoclonal based therapies within 4 weeks and all other immunotherapy within 2 weeks
prior to first dose of study treatment.

6. Systemic radiation therapy within 4 weeks, focal radiotherapy within 2 weeks and
radiopharmaceuticals (strontium, samarium) within 8 weeks prior to first dose of
study treatment.

7. Ocular Melanoma

8. Other prior malignancy, except for adequately treated basal or squamous cell skin
cancer or in situ cancers; or any other cancer from which the patient has been
disease-free for at least 3 years.

9. Active, untreated central nervous system metastases.

10. Active autoimmune disease or documented history of autoimmune disease.

11. Active diverticulitis

12. Significant cardiovascular disease including CHF or poorly controlled hypertension.