This is an investigator initiated single institution, open-label study to evaluate the
      antitumor activity, safety, and tolerability of durvalumab in combination with tremelimumab
      in subjects with select advanced rare solid tumors. The dose-exploration phase, conducted
      across a range of tumor types, has been completed. The dose-expansion phase is ongoing and
      includes certain soft tissue sarcomas, neuroendocrine tumors and thymic carcinoma. Therefore,
      subjects diagnosed with any of those rare tumors are excluded from this trial. Given the
      safety and tolerability data in the previous and ongoing studies (Study D4190C00010 and
      D4190C00006), the selected dose for evaluation in all subjects enrolled in this trial is as
      follows:

      Durvalumab, 1500 mg Q4W (equivalent to 20 mg/kg Q4W) intravenously for 13 doses and
      Tremelimumab 75 mg Q4W (equivalent to 1 mg/kg Q4W) intravenously for 7 doses then every 12
      weeks for 2 doses. Weight-based dosing should be utilized for patients <30 kg: durvalumab 20
      mg/kg and tremelimumab 1 mg/kg. Tremelimumab will be administered first and the infusion
      duration will be approximately 1 hour. The durvalumab infusion will start approximately 1
      hour after the end of the tremelimumab infusion and the infusion will be administered over
      approximately 1 hour.

      The project Surveillance of Rare Cancers in Europe (RARECARE) collected data on cancers from
      89 population-based cancer registries in 21 European countries, making it possible to study
      the epidemiology of these cancers as a whole in a large and heterogeneous population. Working
      from this database and the literature, a RARECARE working group produced a new list of
      cancers and developed a new definition of rare cancers (incidence < 6/100,000/year). This
      definition and working list are adopted for this rare tumor immunotherapy study.