A multiplex UPLC-MS/MS method for the quantification of three PD-L1 checkpoint inhibitors, atezolizumab, avelumab, and durvalumab, in human serum.

BACKGROUND AND AIM: To support pharmacokinetic studies, a multiplex UPLC-MS/MS assay was developed and validated to quantify PD-L1 checkpoint inhibitors atezolizumab, avelumab, and durvalumab in serum. METHODS: A bottom-up sample pre-treatment procedure was developed to determine atezolizumab, avelumab, and durvalumab in serum. This procedure consisted of (1) precipitation of the monoclonal antibody with ammonium sulfate, (2) reduction with dithiothreitol, (3) denaturation with methanol, and (4) tryptic digestion of the protein. The unique signature peptides resulting after sample pre-treatment of the antibodies were measured using UPLC-MS/MS with a total run time of 11 minutes. The clinical application was evaluated by analyzing 114 atezolizumab patient samples. RESULTS: The developed method was found to be accurate and precise for all three analytes over a concentration range of 3.00-150 µg/mL. No endogenous interference was present in serum samples. Cross-interference experiments showed no cross-analyte interference and acceptable cross-internal standard interference. In addition, no substantial carry-over was observed. The stable isotopically labeled signature peptides were most effective in compensating for matrix effects. Recovery based on back-calculated concentrations of calibration standards and quality control samples was found to be high. The analytes were stable for at least three freeze-thaw cycles, for 42 hours at processing conditions, for at least two days at 2-8°C in the final extract, for five days before re-injection analysis at 4°C, and long-term for at least 11 months at -70°C. The assay was tested for its applicability in clinical practice. For this purpose, 114 atezolizumab patient samples were measured. CONCLUSION: A multiplex UPLC-MS/MS assay was developed and validated to quantify atezolizumab, avelumab, and durvalumab in human serum. The applicability of this method was demonstrated by the analysis of clinical atezolizumab samples. The method is suitable to support clinical pharmacokinetic studies involving atezolizumab, avelumab, or durvalumab.

Severe Immune-Related Enteritis after In Utero Exposure to Pembrolizumab.

Immune checkpoint blockade has become standard treatment for many types of cancer. Such therapy is indicated most often in patients with advanced or metastatic disease but has been increasingly used as adjuvant therapy in those with early-stage disease. Adverse events include immune-related organ inflammation resembling autoimmune diseases. We describe a case of severe immune-related gastroenterocolitis in a 4-month-old infant who presented with intractable diarrhea and failure to thrive after in utero exposure to pembrolizumab. Known causes of the symptoms were ruled out, and the diagnosis of pembrolizumab-induced immune-related gastroenterocolitis was supported by the results of histopathological assays, immunophenotyping, and analysis of the level of antibodies against programmed cell death protein 1 (PD-1). The infant's condition was successfully treated with prednisolone and infliximab.