Therapeutic approaches and drug-resistance in chronic lymphocytic leukaemia.

The treatment of chronic lymphocytic leukaemia has been revolutionised in recent years, first by the introduction of chemoimmunotherapy regimens and subsequently by the development of drugs, including ibrutinib, idelalisib and venetoclax, that target components of the B-cell receptor signalling pathway or B-cell lymphoma 2 family of proteins. Despite high initial response rates in patients treated with chemoimmunotherapy or targeted agents, a significant proportion of patients relapse with progressive and refractory disease. In a subset of these patients, drug resistance has been associated with specific genetic lesions or activation of alternate pro-survival pathways. However, the mechanisms that confer drug resistance in the remainder of the patients with refractory disease have yet to be fully elucidated. In this review, we discuss our current understanding of the mechanics of drug resistance in chronic lymphocytic leukaemia and describe how this knowledge may aid in rationalising future treatment strategies to prevent the development of refractory or aggressive transformation of the disease.

Humoral immune failure defined by immunoglobulin class and immunoglobulin G subclass deficiency is associated with shorter treatment-free and overall survival in Chronic Lymphocytic Leukaemia.

Immune dysfunction attributed to hypogammaglobulinaemia is common in chronic lymphocytic leukaemia (CLL) and infection is a major contributor to morbidity and mortality. A higher incidence of multiple immunoglobulin and immunoglobulin G (IgG) subclass deficiency was associated with more advanced disease (P < 0·001 and P < 0·001, respectively) in a cohort of 147 CLL patients. Multiple immunoglobulin and IgG subclass deficiency were significantly associated with shorter treatment-free survival (TFS) (P < 0·001 and P = 0·006, respectively). The association between disease stage and immune dysfunction demonstrated by these data suggest aspects of immune deficiency correlate with disease severity and may be associated with shorter TFS in CLL.

Immunoglobulin G subclass deficiency and infection risk in 150 patients with chronic lymphocytic leukemia.

Hypogammaglobulinemia is a common complication of chronic lymphocytic leukemia (CLL), but the significance of immunoglobulin G (IgG) subclass deficiency is unknown. We analyzed the prevalence of immunoglobulins G, A and M, IgG subclass deficiency and infection in 150 patients with CLL. Low IgG, IgA and IgM levels were observed in 27.3%, 30.7% and 56.7% of patients, respectively. IgG subclass deficiency was frequent, with reduced IgG1, IgG2, IgG3 and IgG4 in 28%, 19.3%, 52% and 22.7% of patients, respectively. IgG subclass deficiency (total 64.6%) and hypogammaglobulinemia (27.3%) were more prevalent than clinically significant infection (16%). Recurrent or significant infections were seen in 24 patients (16%), of whom 50% had hypogammaglobulinemia but 100% had at least one IgG subclass deficiency, indicating that half the patients with infection had IgG subclass deficiency but normal total IgG level. Deficiencies of IgG3 and IgG4 were statistically associated with infection risk. Normal immunoglobulin and IgG subclass levels were seen in 26 patients (17%) and none had infections. IgG subclass deficiency is commonly observed in patients with CLL with both normal and reduced total IgG levels, and is associated with infection. Screening patients with CLL for IgG subclass deficiency may be a useful adjunct in stratifying their infection risk.