The introduction of PD-1/PD-L1 pathway inhibitors is an important landmark in solid oncology with unprecedented practice-changing activity in various types of solid tumours. Among haematological malignancies, PD-1/PD-L1 inhibitors have been successful, so far, only in the treatment of classical Hodgkin lymphoma, which typically exhibits an over-expression of PD-1 ligands (PD-L1, PD-L2) due to alterations in chromosome 9p24.1. Such positive outcomes led to the US Food and Drug Administration approval of nivolumab use in relapsed Hodgkin lymphoma in 2016 as the first haematological indication. Although the results in other lymphoid malignancies have not been so striking, blockade of the PD-1/PD-L1 axis has led to meaningful responses in other lymphoma types such as diffuse large B-cell lymphoma, follicular lymphoma or several T-cell lymphomas. Monotherapy with PD-1/PD-L1 inhibitors in chronic lymphocytic leukaemia and multiple myeloma has been unsatisfactory, suggesting that a combinational approach with other synergistic drugs is needed. In the case of multiple myeloma, immunomodulatory agents together with corticosteroids represent the most promising combinations. Among myeloid malignancies, the anti-PD-1 monoclonal antibodies are examined dominantly in acute myeloid leukaemia and myelodysplastic syndromes in combination with potentially synergistic hypomethylating drugs such as 5-azacitidine, resulting in promising outcomes that warrant further investigation. We have described all available clinical results of PD-1/PD-L1 inhibitors in haematological malignancies and discussed related toxicities, as well as highlighted crucial preclinical studies in this review.
For patients with indolent non-Hodgkin lymphoma who fail initial anti-CD20–based immunochemotherapy or develop relapsed or refractory disease, there remains a significant unmet clinical need for new therapeutic approaches to improve outcomes and quality of life. 177Lu-lilotomab satetraxetan is a next-generation single-dose CD37-directed radioimmunotherapy (RIT) which was investigated in a phase 1/2a study in 74 patients with relapsed/refractory indolent non-Hodgkin B-cell lymphoma, including 57 patients with follicular lymphoma (FL). To improve targeting of 177Lu-lilotomab satetraxetan to tumor tissue and decrease hematologic toxicity, its administration was preceded by the anti-CD20 monoclonal antibody rituximab and the “cold” anti-CD37 antibody lilotomab. The most common adverse events (AEs) were reversible grade 3/4 neutropenia (31.6%) and thrombocytopenia (26.3%) with neutrophil and platelet count nadirs 5 to 7 weeks after RIT. The most frequent nonhematologic AE was grade 1/2 nausea (15.8%). With a single administration, the overall response rate was 61% (65% in patients with FL), including 30% complete responses. For FL with ≥2 prior therapies (n = 37), the overall response rate was 70%, including 32% complete responses. For patients with rituximab-refractory FL ≥2 prior therapies (n = 21), the overall response rate was 67%, and the complete response rate was 24%. The overall median duration of response was 13.6 months (32.0 months for patients with a complete response). 177Lu-lilotomab satetraxetan may provide a valuable alternative treatment approach in relapsed/refractory non-Hodgkin lymphoma, particularly in patients with comorbidities unsuitable for more intensive approaches. This trial was registered at www.clinicaltrials.gov as #NCT01796171.
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