Safe administration of anti-PD-1 immunotherapy in a patient with pre-existing primary biliary cholangitis.

A 63-year-old female presented with cholestatic liver function tests in November 2016. Screening tests were negative for other causes and liver biopsy revealed primary biliary cholangitis (PBC) with autoimmune hepatitis (AIH) overlap. Ursodeoxycholic acid and azathioprine was initiated. In September 2018 she was diagnosed with Stage III BRAF wild-type melanoma. Azathioprine was ceased and adjuvant immunotherapy was not recommended due to the risk of worsening PBC/AIH. Surveillance PET revealed metastatic disease and she commenced pembrolizumab. Restaging PET after 4 cycles showed a complete metabolic response, with no hepatitis or other significant toxicity. We believe this is the first reported case of the safe administration of pembrolizumab in a patient with known PBC/AIH. Treatment duration in such high risk patients needs further investigation.