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 after any prior therapy based on anti-PD-1 or anti-PD-L1 as
             defined by disease progression within 26 weeks of initiating anti-PD-1 or anti-PD-L1
             based therapy without any evidence of a response (primary resistance to anti-PD-1 or
             anti-PD-L1).

          -  Patients must have a site of disease amenable to biopsy and be a candidate for tumor
             biopsy. Patients must be able and willing to provide mandatory tumor biopsies prior to
             and during study treatment.

        Dose expansion (Part 2B)

          -  Patients with disease location amenable to mandatory tumor biopsy at baseline with
             histologically confirmed advanced unresectable or metastatic melanoma, colorectal
             adenocarcinoma, urothelial cancer, hepatocellular carcinoma (HCC), or non-small cell
             lung cancer (NSCLC).

          -  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
             lines of therapy for advanced disease. Patients must not have received prior treatment
             with anti-PD-1 or anti-PD-L1.

          -  Patients with HCC must have failed after 1 prior therapy based on anti-PD-1 or
             anti-PD-L1.

          -  Patients with NSCLC must have failed during or after 1 prior therapy based on
             anti-PD-1 or anti-PD-L1.

          -  Patients with histologically confirmed, advanced unresectable or metastatic melanoma,
             or colorectal cancer or NSCLC whom in the opinion of the Investigator do 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 or < the country's legal age of majority if the legal age is more than
             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 highly 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), HIV serology at screening will be
             conducted only for patients in German study sites.

          -  Known uncontrolled hepatitis B virus (HBV) infection.

          -  Known untreated current hepatitis C virus (HCV) infection.

          -  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.

          -  History of 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).

          -  Patients accommodated in an institution because of regulatory or legal order;
             prisoners or patients who are legally institutionalized.

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