The Efficacy and Safety of Penpulimab in the Treatment of Metastatic PPGL Patients Who Fail to Other Systemic Treatment

Inclusion Criteria: * Provide written informed consent. * Age 18-75 years old * Eastern Cooperative Oncology Group (ECOG) performance status 0, 1, or 2. * Patients with histologically or radiologically confirmed MPP and fail to other systemic therapy. * Estimated life expectancy longer than 6 months. * Confirmed non-pregnancy and lactation. During the entire study period and within 6 months after the last administration, the subjects and their spouses are willing to use efficient contraceptive measures. * Laboratory requirements: * Absolute granulocyte count (AGC) greater than 1.5 x 109/L; * Platelet count greater than 80 x 109/L; * Hemoglobin greater than 90g/L; * Serum bilirubin less than 1.5 x upper limit of normal (ULN); --)Serum aspartate aminotransferase (AST) and alanine aminotransferase (ALT) less than 2.5 x ULN; * Serum creatinine less than 1.5 x ULN or creatinine clearance (CCr)≥60ml/min; * Doppler ultrasound assessment: left ventricular ejection fraction (LVEF) ≥ lower limit of normal value (50%). Exclusion Criteria: * Patients who had been previously treated with anti-PD1, anti-PD-L1, or anti-PD-L2 medications were excluded from this trial. * Has a diagnosis of immunodeficiency or is receiving systemic steroid therapy or any other form of immunosuppressive therapy within 14 days prior to the first dose of trial treatment. * Has a known history of active TB (Bacillus Tuberculosis). * Has a known history of Human Immunodeficiency Virus (HIV). * Has known active Hepatitis B (e.g., HBsAg reactive) or Hepatitis C (e.g., HCV RNA \[qualitative\] is detected). * Has an active infection requiring systemic therapy. * Didn't meet eligibility for organ function. * Abnormal coagulation (INR \>1.5 or prothrombin time (PT) \> ULN 4 seconds or APTT \>1.5 ULN), bleeding tendency or being treated with thrombolytic or anticoagulant therapy. * Uncontrolled congestive heart failure .