This study will test a study drug called cemiplimab to see if it can help treat early-stage Cutaneous Squamous Cell Carcinoma (CSCC), a type of skin cancer. Cemiplimab works by helping the immune system to kill cancer cells. It binds to a protein called Programmed cell Death-1 (PD-1) on the surface of certain immune cells.

The main purpose of this study is to compare how well cemiplimab works compared to surgery, when injected into the lesion.

The study is looking at:

• The side effects cemiplimab might cause
• How well cemiplimab works compared to surgery

Key Inclusion Criteria:

1. Participants who have a histologically confirmed invasive CSCC TL, as described in the protocol
2. Participants who have CSCC TL ≥1 cm and ≤2.0 cm (longest diameter) located in either the Head or Neck (HN), hand, or pre-tibial surface, as described in the protocol
3. Participants who are judged to be eligible for surgical resection of their CSCC TL and the method of planned surgical resection would be Micrographically oriented histographic surgery (Mohs) or other surgical method of Complete Margin Assessment (CMA). Participants for whom the planned surgery is surgical excision without margin control are not eligible
4. Eastern Cooperative Oncology Group (ECOG) performance status (PS) ≤1
5. Adequate hepatic, renal and bone marrow functions, as described in the protocol

Key Exclusion Criteria:

1. Participant in which the TL is a keratoacanthoma (KA), adenosquamous carcinoma, desmoplastic carcinoma, sarcomatoid carcinoma, basal cell carcinoma, basosquamous carcinoma, Bowen's disease, or CSCC in situ without an invasive component. (Note: For participants with invasive CSCC with a minor basaloid component, the patient may be eligible after discussion with the sponsor medical director.)
2. 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), as described in the protocol
3. History of non-infectious pneumonitis within the last 5 years
4. TL (lesion planned for intralesional therapy) or other non-target CSCC lesion in dry red lip (vermillion), oral cavity, or nasal mucosa

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