A Study of SAR444245 Combined With Cemiplimab for the Treatment of Participants With Various Advanced Skin Cancers (Pegathor Skin 201)

Inclusion Criteria:

* Participant must be ≥18 years of age (or country's legal age of majority if \>18 years), at the time of signing the informed consent.
* Participants with:
* Cohort A: Histologically confirmed unresectable locally advanced or metastatic melanoma that are not amenable to local therapy
* Cohort B: Histologically confirmed metastatic CSCC or locally advanced
* CSCC that are not candidates for curative surgery or radiation. Special considerations for the following categories:

Participants with tumors arising on the cutaneous hair (non-glabrous) bearing lip with extension onto dry red lip (vermillion) may be eligible after communication with and approval from the Sponsor

Participants with the primary site is nose are only eligible if the primary site was skin, not nasal mucosa with outward extension to skin (the Investigator confirmed)

Participants with mixed histology in which the predominant histology is invasive CSCC may be eligible after communication with and approval from the Sponsor

* Participants in both cohorts must have at least one measurable lesion
* Provision of tumor tissue:

For participants in the dose escalation:

16 µg/kg: at screening, biopsy is optional but highly recommended; and on-treatment not required

24 µg/kg: at screening, biopsy is mandatory and on-treatment, optional but highly recommended

* For the other participants : Mandatory baseline biopsy for the participants to enroll in cohort A with skin metastasis and in cohort B. Mandatory on-treatment biopsy for participants in Cohort A with skin metastasis and participants in Cohort B.
* Females are eligible to participate if they are not pregnant or breastfeeding, not a woman of childbearing potential (WOCBP) or are a WOCBP that agrees: to use approved contraception method and submit to regular pregnancy testing prior to treatment and for at least 180 days after discontinuing study treatment and to refrain from donating or cryopreserving eggs for 180 days after discontinuing study treatment.
* Males are eligible to participate if they agree to refrain from donating or cryopreserving sperm, and either abstain from heterosexual intercourse OR use approved contraception during study treatment and for at least 210 days after discontinuing study treatment.
* Capable of giving signed informed consent

Exclusion Criteria:

* Participants are excluded from the study if any of the following criteria apply:
* Eastern Cooperative Oncology Group (ECOG) performance status of ≥2
* Poor organ function
* Participants with baseline SpO2 ≤92%
* Active brain metastases or leptomeningeal disease.
* History of allogenic tissue/solid organ transplant.
* Last administration of prior antitumor therapy or any investigational treatment within 28 days or less than 5 times the half-life, whichever is shorter; major surgery or local intervention within 28 days.
* History of lung disease
* Comorbidity requiring corticosteroid therapy
* Antibiotic use (excluding topical antibiotics) ≤14 days prior to first dose of IMP
* Severe or unstable cardiac condition within 6 months prior to starting study treatment
* Active, known, or suspected autoimmune disease that has required systemic treatment in the past 2 years
* Known second malignancy either progressing or requiring active treatment within the last 3 years

For both cohorts:

* Prior immune checkpoint inhibitors except in the context of adjuvant or neoadjuvant; Participants who were on control arm of a study with an investigational anti-PD-1/PD-L1 are eligible.
* Received adjuvant or neoadjuvant therapy during the 6 months prior to development of metastatic disease.
* For Cohort A: any prior systemic treatment for advanced/metastatic disease
* For Cohort B: \>2 prior lines of any systemic treatment for advanced/metastatic disease
* Inability to undergo any contrast-enhanced radiologic response assessment
* Receipt of a live-virus vaccination within 28 days of planned treatment start. Seasonal flu vaccines that do not contain live virus are permitted

The above information is not intended to contain all considerations relevant to a patient's potential participation in a clinical trial.