Although nivolumab is administered every two or four weeks, high programmed cell death-1 (PD-1) binding of nivolumab on T cells lasting for several months has been reported. A relationship between the PD-1 occupancy rate on T-cells and the efficacy of nivolumab is not yet fully understood. The present study used flow cytometric analyses to determine the time-dependence of PD-1 occupancy in five patients who discontinued nivolumab. The relationship between PD-1 occupancy at relapse and the efficacy of re-challenge was also studied. Occupancies after discontinuation were measured at a total of 32 points. The data indicated that it took 32.4 and 48.9 weeks to decrease occupancy by 50 and 70%, respectively. Subsequently, two patients had recurrence and were re-challenged with nivolumab. At that time, one patient had 70.8% occupancy while the other had 6.6%. Treatment was effective only for the patient with lower occupancy. Overall, the present study suggests that re-challenge with nivolumab may be efficacious in patients with low occupancy at recurrence.

Context The occurrence of multiple endocrinopathies due to immune checkpoint inhibitors (ICIs) is relatively common as an adverse event. However, the occurrence of a combination of hypophysitis and type 1 diabetes mellitus (T1DM) is extremely rare, and its clinical features are unclear. Objective To comparatively analyze the clinical features of this combination and each individual ICI-induced endocrinopathy. Methods We reported three cases that we encountered and reviewed previously reported cases of patients with combined hypophysitis and T1DM due to ICIs. Results Anti-programmed cell death-1 (anti-PD-1) antibodies were prescribed to all the three cases. The duration from ICI initiation to the onset of these endocrine disease was 12–48 weeks. Several human leukocyte antigen (HLA) haplotypes that have disease susceptibility to hypophysitis were detected in all three patients. Combining the 17 previously reported cases, combined endocrinopathies were more common in men (85%). The onset age was 60 s for both combined and single endocrinopathies. Anti-PD-1 antibodies were used in most of the cases (90%). The time from ICI initiation to the onset of endocrinopathies was 24 [8-76] weeks for hypophysitis and 32 [8-76] weeks for T1DM in patients with combined endocrinopathies, which was not significantly different from that for each single endocrinopathy. Conclusions We presented three cases of patients with combined endocrinopathies of hypophysitis and T1DM that may have been caused by anti-PD-1 antibodies. There was no difference in the time from ICI initiation to the onset of endocrinopathies between combined and single endocrinopathies. Further case accumulation and pathogenic investigations are required.

Context: There is an increasing demand for appropriate preclinical mice models for evaluating the efficacy of cancer immunotherapies. Aims: Therefore, we established a humanized patient-derived xenograft (PDX) model using microsatellite instability-high (MSI-H) colorectal cancer (CRC) tissues and patient-derived peripheral blood mononuclear cells (PBMCs). Subjects and Methods: The CRC tissues of patients scheduled for surgery were tested for MSI status, and CRC tumors were transplanted into NOD/LtSz-scid/IL-2Rg-/-(NSG) mice to establish MSI-H PDX models. PDX tumors were compared to the original patient tumors in terms of histological and genetic characteristics. To humanize the immune system of MSI-H PDX models, patient PBMCs were injected through the tail vein. Results: PDX models were established from two patients with MSI-H CRC; one patient had a germline mutation in MLH1 (c.1990-2A > G), and the other patient had MLH1 promoter hypermethylation. PDX with the germline mutation was histologically similar to the patient tumor, and retained the genetic characteristics, including MSI-H, deficient mismatch repair (dMMR), and MLH1 mutation. In contrast, the histological features of the other PDX from a tumor with MLH1 promoter hypermethylation were clearly different from those of the original tumor, and MLH1 promoter hypermethylation and MSI-H/dMMR were lost in the PDX. When T cells from the same patient with MLH1 mutation were injected into the PDX through the tail vein, they were detected in the PDX tumor. Conclusions: The MSI-H tumor with an MMR mutation is suitable for MSI-H PDX model generation. The PBMC humanized MSI-H PDX has the potential to be used as an efficient model for cancer immunotherapy research.