Inclusion criteria:

Dose escalation (Part 1A and Part 1B)

• • Patients with histologically confirmed, advanced unresectable or metastatic solid tumor whom in the opinion of the Investigator does not have a suitable alternative therapy.

Dose expansion (Part 2A)

• • Patients with histologically confirmed, advanced unresectable or metastatic melanoma whom in the opinion of the Investigator does not have a suitable alternative therapy.
• • Patients must have failed a prior therapy based on anti-PD-1 or anti-PD-L1 as defined by disease progression confirmed radiologically within 12 weeks of commencing treatment without any evidence of a response.
• • Patients must have a site of disease amenable to biopsy and be a candidate for tumor biopsy. Patients must be able to provide mandatory tumor biopsies prior to and during study treatment.

Dose expansion (Part 2B)

• • Patients with histologically confirmed advanced unresectable or metastatic melanoma or colorectal adenocarcinoma or patients with urothelial cancer.
• • Melanoma patients must have failed one prior therapy based on anti-PD-1 or anti-PD-L1.
• • Patients with colorectal cancer must have progressed after last line of therapy.
• • Patients with urothelial cancer must have disease progression during or following platinum-containing chemotherapy or within 12 months of neoadjuvant or adjuvant treatment with platinum-containing chemotherapy. Patients must not have received >2 prior lines therapy. Patients must not have received prior treatment with anti-PD1 or anti-PDL1.
• • Patients with histologically confirmed, advanced unresectable or metastatic melanoma, colorectal cancer or metastatic urothelial cancer whom in the opinion of the Investigator does not have a suitable alternative therapy.

Dose expansion parts 2A and 2B

• • At least 1 measurable lesion by RECIST v1.1.

All cohorts

• • Patient understands and has signed Informed Consent form and is willing and able to comply with the requirements of the trial.

Exclusion criteria:

• • Age <18 years.
• • Eastern Cooperative Oncology Group (ECOG) performance status >1.
• • Concurrent treatment with any other anticancer therapy (including radiotherapy or investigational agents) or participation in another clinical study.
• • Washout period of less than 3 weeks to prior anticancer therapy.
• • Women of reproductive potential and male subjects with female partners of childbearing potential who are not willing to avoid pregnancy by using effective contraceptive.
• • Pregnant or breast-feeding women.
• • Unwillingness and inability to comply with scheduled visits, drug administration plan, laboratory tests, other study procedures, and study restrictions.
• • Significant and uncontrolled concomitant illness, including any psychiatric condition.
• • Active infections, including unexplained fever (temperature >38.1ºC), or antibiotic therapy within 1 week prior to enrollment.
• • Any prior organ transplant including allogeneic bone marrow transplant.
• • History within the last 5 years of an invasive malignancy other than the one treated in this study, with the exception of resected/ablated basal or squamous-cell carcinoma of the skin or carcinoma in situ of the cervix, or other local tumors considered cured by local treatment.
• • History of known human immunodeficiency virus (HIV), unresolved viral hepatitis.
• • Any major surgery within the last 28 days.
• • Patients with primary central nervous system (CNS) tumors and/or CNS metastases of non-CNS primary tumors that are untreated.
• • History of severe, congestive heart failure, myocardial infarction with reduced ejection fraction, symptomatic coronary artery disease, documented uncontrolled hypertension, major clinically significant Electrocardiography (ECG) and echocardiogram abnormalities, significant ventricular arrhythmias, significant valvular heart disease (including valve replacement), vascular malformation, aneurysm, significant pulmonary conditions such as idiopathic pulmonary hypertension, uncontrolled chronic lung disease.
• • History of severe, acute or chronic renal diseases.
• • Any of the following within 6 months prior to study enrollment: pulmonary embolism, deep vein thrombosis, active uncontrolled bleeding, infectious or inflammatory bowel disease, diverticulitis, intestinal obstruction or perforation and gastrointestinal hemorrhage.
• • Inadequate hematological, renal or liver function.
• • Non-resolution of any prior treatment related toxicity to Grade <2.
• • Prior treatment with any anti-transforming growth factor β (anti-TGFβ) inhibitors.
• • Known allergies to any component of SAR439459 and/or cemiplimab.
• • Patients with uveal melanoma and patients with prior or ongoing uveitis.
• • Patients who received prior immunotherapy who developed toxicity leading to a permanent discontinuation of immunotherapy.
• • Ongoing or recent (within 5 years) evidence of significant autoimmune disease that required treatment with systemic immunosuppressive treatments.
• • Immunosuppressive corticosteroid doses (>10 mg prednisone daily or equivalent) within 4 weeks prior to the first dose of SAR439459 and/or cemiplimab (occasional use of inhaled, intraocular, nasal or topical steroids for symptomatic relief allowed).
• • History of interstitial lung disease or active non-infectious pneumonitis that required immune-suppressive doses of glucocorticoids to assist with management.
• • Patients with underlying cancer predisposition syndromes.
• • Receipt of a live vaccine within 30 days of planned start of study medication.
• • Therapeutic doses of anticoagulants or antiplatelet agents within 7 days prior the first dose of SAR439459.
• • Prothrombin time (PT) or international normalized ratio (INR) > 1.5 × upper limit of normal (ULN).

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