This study is researching an experimental drug called cemiplimab. The study is focused on Cutaneous Squamous Cell Carcinoma (CSCC) and Basal Cell Carcinoma (BCC).

The aim of the study is to evaluate the safety and tolerability (how your body reacts to the drug) of cemiplimab (also known as REGN2810).

The first part of the study tested several different doses of cemiplimab given weekly for 12 weeks.

The study is also looking at several other research questions, including:

• What side effects may happen from taking the study drug
• To see effect of cemiplimab on the tumor
• How much study drug is in the blood at different times

Key Inclusion Criteria

1. Dose Escalation: History of recurrent resectable CSCC or BCC (Cohort C and I only) that satisfies conditions as defined in the protocol
2. Patients must have measurable disease in the index lesion, defined as 1-2 cm in the longest diameter
3. Eastern Cooperative Oncology Group (ECOG) performance status ≤1

Key Exclusion Criteria

1. Ongoing or recent (within 5 years) evidence of significant autoimmune disease that required treatment with systemic immunosuppressive treatments, which may suggest risk for immune-mediated adverse events (imAEs)
2. Prior treatment with an agent that blocks the programmed cell death 1 (PD-1)/ programmed cell death 1 ligand (PD-L1) pathway.
3. Prior treatment with other systemic immune modulating agent as defined in the protocol
4. M1 or N1, N2 (a, b, or c), or N3 CSCC or BCC. Patients with history of metastatic CSCC (distant or nodal), or metastatic BCC (distant or nodal) are excluded unless the disease-free interval is at least 3 years
5. Concurrent malignancies, other than those with negligible risk of metastasis or death. Patients with hematologic malignancies, including chronic lymphocytic leukemia (CLL), are excluded.
6. Patients with a history of solid organ transplant
7. Has received a Coronavirus induced disease of 2019 (COVID-19) vaccination (initial series and booster) within 1 week of planned start of study medication

Note: Other protocol defined Inclusion/Exclusion criteria apply.

All Individual Patient Data (IPD) that underlie publicly available results will be considered for sharing

When Regeneron has:

• received marketing authorization from major health authorities (e.g., FDA, European Medicines Agency (EMA), Pharmaceuticals and Medical Devices Agency (PMDA), etc.) for the product and indication or has globally discontinued development of the product for all indications on or after April 2020 and has no plans for future development
• made the study results publicly available (e.g., scientific publication, scientific conference, clinical trial registry)
• the legal authority to share the data, and
• ensured the ability to protect participant privacy

Qualified researchers can submit a proposal for access to individual patient or aggregate level data from a Regeneron-sponsored clinical trial through Vivli. Regeneron's Independent Research Request Evaluation Criteria can be found at: https://www.regeneron.com/sites/default/files/Regeneron-External-Data-Sharing-Policy-and-Independent-Research-Request-Evaluation-Criteria.pdf