Unexpected Toxicities When Nivolumab Was Given after Allogeneic Stem Cell Transplantation
Authors: Wang Amy , Kline Justin , Stock Wendy , Kosuri Satyajit , Artz Andrew S. , Larson Richard A. , Riedell Peter A. , Bishop Michael R. , Liu Hongtao 
Published: November 2019

Background:Treatment options are limited for patients (pts) with hematologic malignancies who relapse after allogeneic stem cell transplantation (allo-SCT). We hypothesized that checkpoint inhibitors may offer a novel approach for maintaining remission after allo-SCT. Data from pre-clinical studies have suggested a potential role for PD-1/PD-L1 inhibitors in acute myeloid leukemia (AML) (Zhang et al., Blood 2009), so it is possible that immunomodulation with checkpoint inhibitors could stimulate the donor anti-leukemia immune response and prevent disease relapse. However, the safety of checkpoint blockade early after allografting remains to be established.
Methods:We conducted a pilot study to assess the tolerability and efficacy of Nivolumab, a PD-1 inhibitor, as maintenance therapy after allo-SCT (NCT02985554). Pts were eligible if they were post allo-SCT without evidence of relapse or active graft-vs-host disease (GVHD) or history of prior greater than stage I skin acute GVHD. Nivolumab was to be administered intravenously at 1mg/kg every 2 weeks for 4 doses followed by dosing every 12 weeks. Treatment started 4 weeks after routine immunosuppression was discontinued until 2 years after the transplant. The primary objective was to determine the tolerability of Nivolumab on this schedule. Secondary objectives were evaluation of adverse events, relapse, and overall survival.
Results:Four pts were enrolled from December 2017 through November 2018. (Table 1)All pts experienced immune-related adverse events (irAE) from Nivolumab, and 2 (50%) pts experienced serious adverse events. (Table 2)One pt developed grade (G) 4 neutropenia soon after the first dose. (Figure 1)The absolute neutrophil count nadired at 20 cells/µL, at which point pegfilgrastim was administered. An interim bone marrow biopsy (BMBx) confirmed no evidence of relapsed disease. Full neutrophil recovery occurred approximately 3 months after the initial dose, and no subsequent toxicities occurred. Another pt developed G3 autoimmune encephalopathy concurrently with G2 transaminitis and G2 thrombocytopenia after one dose of Nivolumab. (Figure 2)Intravenous methylprednisolone (1mg/kg daily for 3 days) and immunoglobulin (2g/kg in 4 divided doses) were administered, followed by a 7-week steroid taper with full resolution of symptoms. Relapsed disease was ruled out by a BMBx. A third pt developed G2 skin rash approximately 10 days after the first dose of Nivolumab. Skin biopsy demonstrated drug hypersensitivity reaction vs GVHD, and the pt was treated with a 3-week prednisone course (starting at 1mg/kg followed by a taper). A mild flare recurred 2 weeks later, which was treated with topical steroids only. However, Nivolumab was not resumed. The fourth pt developed G2 elevated TSH approximately 2 months into therapy and after 4 doses of Nivolumab. Thyroid hormone replacement was initiated with subsequent symptom improvement and normalization of TSH over a 4-month period. As a result of these unexpected severe toxicities, the study was closed to further enrollment, and further Nivolumab administration ceased. Thus far, one pt (#1) relapsed after a total remission duration of 530 days; the remission duration after starting Nivolumab was 318 days. One pt has mild chronic skin GVHD. All 4 patients remain alive with a median overall survival of 2.3 years (range, 1.9-4.7).
Conclusions:Even at low doses, the use of Nivolumab as maintenance therapy in the post allo-SCT setting was not tolerable at the current dosing and schedule due to an unexpected number of high grade irAEs. Additional studies of dose and timing after allo-SCT are needed to improve safety and tolerability, in conjunction with correlative studies to better understand the immunomodulatory processes in the post-transplant setting.

Disclosures
Kline: Merck: Honoraria; Merck: Research Funding. Stock:Kite, a Gilead Company: Membership on an entity's Board of Directors or advisory committees; Pfizer: Membership on an entity's Board of Directors or advisory committees; Daiichi: Membership on an entity's Board of Directors or advisory committees; Astellas: Membership on an entity's Board of Directors or advisory committees; Agios: Membership on an entity's Board of Directors or advisory committees; UpToDate: Honoraria; Research to Practice: Honoraria. Artz:Miltenyi: Research Funding. Larson:Agios: Consultancy; Novartis: Honoraria, Other: Contracts for clinical trials; Celgene: Consultancy. Riedell:Novartis: Research Funding; Verastem: Membership on an entity's Board of Directors or advisory committees; Celgene: Membership on an entity's Board of Directors or advisory committees, Research Funding; Bayer: Honoraria, Speakers Bureau; Kite/Gilead: Honoraria, Research Funding, Speakers Bureau. Bishop:CRISPR Therapeutics: Consultancy, Membership on an entity's Board of Directors or advisory committees; Novartis: Consultancy, Membership on an entity's Board of Directors or advisory committees, Research Funding; Kite: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau; Juno: Consultancy, Membership on an entity's Board of Directors or advisory committees; Celgene: Consultancy, Membership on an entity's Board of Directors or advisory committees, Speakers Bureau. Liu:Arog: Other: PI of clinical trial; BMS: Research Funding; Agios: Honoraria; Novartis: Other: PI of clinical trial; Karyopharm: Research Funding.

OffLabel Disclosure:
Nivolumab used as maintenance therapy in the post-transplant setting