This is an open-label study to evaluate the safety and the anti-tumor activity of the combination of nivolumab and celecoxib.

The total numbers of participants to be enrolled will be up to 68 participants, depending on the investigated dose of celecoxib during the safety run-in phase.

Inclusion Criteria:

• Men and women ≥ 18 years of age.

• Eastern Cooperative Oncology Group (ECOG) Performance Status of 0 or 1.

• Measurable disease as per RECIST 1.1.

• Adequate renal, hepatic and hematologic functions as defined by laboratory parameters within ≤ 7 days before treatment initiation.

• Metastases biopsiable on two occasions

• Recently acquired (within 90 days prior to treatment) tumor tissue from an unresectable or metastatic site of disease must be provided for biomarker analyses. In order to include only IDO1 positive (≥5% expression of tumor cells) and non T-cell infiltrated tumors (<1% T cells infiltrating the tumor bed)

• Cancer types with an indication of treatment with anti-PD1 antibodies such as

  • Melanoma non BRAF mutated in first line of treatment
  • Melanoma BRAF mutated in first or second line of treatment
  • Lung cancer (NSCLC) in second line of treatment
  • Renal cell Cancer (RCC) in second line of treatment
  • Head and Neck squamous carcinoma (HNSC) after platinum salt based chemotherapy
  • Bladder cancer after platinum salt based chemotherapy

Exclusion Criteria:

• Active brain metastases or leptomeningeal metastases.
• Ocular melanoma.
• Subjects with active, known or suspected autoimmune disease. Subjects with vitiligo, type I diabetes mellitus, residual hypothyroidism due to autoimmune condition only requiring hormone replacement therapy, psoriasis not requiring systemic treatment, or other autoimmune condition not expected to recur in the absence of an external trigger are permitted to enroll.
• Subjects must also meet other study criteria including exclusions for medical history, positive Hep B/C, HIV, and pregnancy tests, and other laboratory criteria.