A Phase 2 Randomized Study of Adjuvant Immunotherapy With the Personalized Cancer Vaccine mRNA-4157 and Pembrolizumab Versus Pembrolizumab Alone After Complete Resection of High-Risk Melanoma

The purpose of this study is to assess whether postoperative adjuvant therapy with mRNA-4157
and pembrolizumab improves recurrence free survival (RFS) compared to pembrolizumab alone in
participants with complete resection of cutaneous melanoma and a high risk of recurrence.

Key Inclusion Criteria:

- Resectable cutaneous melanoma metastatic to a lymph node and at high risk of
recurrence

- Complete resection within 13 weeks prior to the first dose of pembrolizumab

- Disease free at study entry (after surgery) with no loco-regional relapse or distant
metastasis and no clinical evidence of brain metastases

- Has an formalin fixed paraffin embedded (FFPE) tumor sample available suitable for
sequencing

- Eastern Cooperative Oncology Group (ECOG) Performance Status 0 or 1

- Normal organ and marrow function reported at screening

Key Exclusion Criteria:

- Prior malignancy, unless no evidence of that disease for at least 5 years prior to
study entry

- Prior systemic anti-cancer treatment (except surgery and interferon for thick primary
melanomas. Radiotherapy after lymph node dissection is permitted)

- Live vaccine within 30 days prior to the first dose of pembrolizumab

- Transfusion of blood or administration of colony stimulating factors within 2 weeks of
the screening blood sample

- Active autoimmune disease

- Immunodeficiency, systemic steroid therapy, or any other immunosuppressive therapy
within 7 days prior to the first dose of pembrolizumab

- Solid organ or allogeneic bone marrow transplant

- Pneumonitis or a history of (noninfectious) pneumonitis that required steroids

- Prior interstitial lung disease

- Clinically significant heart failure

- Known history of human immunodeficiency virus (HIV)

- Known active hepatitis B or C

- Active infection requiring treatment