Promising therapies for the treatment of chronic lymphocytic leukemia

Engineering extracellular vesicles as novel treatment options: exploiting herpesviral immunity in CLL

Extracellular vesicles (EVs) are important mediators of cell–cell communication. Intriguingly, EVs can be engineered and thus exploited for the targeted transfer of functional proteins of interest. Thus, engineered EVs may constitute attractive tools for the development of novel therapeutic interventions, like cancer immunotherapies, vaccinations or targeted drug delivery. Here, we describe a novel experimental immunotherapeutic approach for the adjuvant treatment of chronic lymphocytic leukaemia (CLL) based on engineered EVs carrying gp350, the major glycoprotein of Epstein–Barr virus (EBV), CD40L, a central immune accessory molecule and pp65, an immunodominant antigen of the human cytomegalovirus (CMV). We show that these engineered EVs specifically interact with malignant B cells from CLL patients and render these cells immunogenic to allogeneic and autologous EBV- and CMV-specific CD4+ and CD8+ T cells. Collectively, co-opting engineered EVs to re-target the strong herpesviral immunity in CLL patients to malignant cells constitutes an attractive strategy for the adjuvant treatment of a still incurable disease.

Abbreviations: CLL: chronic lymphocytic leukaemia; EBV: Epstein-Barr virus; CMV: cytomegalovirus

Ibrutinib for treatment of chronic lymphocytic leukemia

PURPOSE

The pharmacology, pharmacokinetics, pharmacodynamics, clinical efficacy, and safety of ibrutinib are described.

SUMMARY

Ibrutinib is a first-in-class oral inhibitor of Bruton tyrosine kinase (BTK) approved for treatment of relapsed chronic lymphocytic leukemia (CLL). Ibrutinib blocks downstream signaling of the B-cell receptor, disrupting stromal microenvironment interactions and B-cell cytokine signaling. BTK inhibition has been shown to be effective in relapsed or refractory CLL. A recent Phase III study evaluated ibrutinib (420 mg daily) versus ofatumumab (consistent with labeling) in relapsed or refractory CLL with a primary endpoint of progression free survival (PFS, n = 391). After a median follow-up period of 9.4 months, a PFS was not attained in ibrutinib-treated individuals with and without deletion 17p. In contrast, ofatumumab-treated individuals experienced a PFS of 8.1 months and those with deletion 17p experienced a PFS of 5.8 months. Major hemorrhage was reported in 2 (1%) patients treated with ibrutinib, and a total of 8 (4%) patients discontinued treatment due to toxicity or adverse reactions. Partial response or partial response with lymphocytosis was achieved in 63% of ibrutinib-treated individuals as determined by independent assessments. Overall, ibrutinib reduced the rate of mortality by 57%.

CONCLUSION

Ibrutinib is a first-in-class, orally active, irreversible BTK inhibitor with a novel mechanism of action. This unique mechanism of action and high overall response rates observed in clinical trials make ibrutinib an attractive second-line option in patients who have disease progression while receiving monoclonal antibody therapy or chemoimmunotherapy.

Real-world clinical experience in the Connect® chronic lymphocytic leukaemia registry: a prospective cohort study of 1494 patients across 199 US centres

The clinical course of chronic lymphocytic leukaemia (CLL) is heterogeneous, and treatment options vary considerably. The Connect® CLL registry is a multicentre, prospective observational cohort study that provides a real-world perspective on the management of, and outcomes for, patients with CLL. Between 2010 and 2014, 1494 patients with CLL and that initiated therapy, were enrolled from 199 centres throughout the USA (179 community-, 17 academic-, and 3 government-based centres). Patients were grouped by line of therapy at enrolment (LOT). We describe the clinical and demographic characteristics of, and practice patterns for, patients with CLL enrolled in this treatment registry, providing patient-level observational data that represent real-world experiences in the USA. Fluorescence in situ hybridization (FISH) analyses were performed on 49·3% of patients at enrolment. The most common genetic abnormalities detected by FISH were del(13q) and trisomy 12 (45·7% and 20·8%, respectively). Differences in disease characteristics and comorbidities were observed between patients enrolled in LOT1 and combined LOT2/≥3 cohorts. Important trends observed include the infrequent use of genetic prognostic testing, and differences in patient characteristics for patients receiving chemoimmunotherapy combinations. These data represent experiences of patients with CLL in the USA, which may inform treatment decisions in everyday practice.

Histone deacetylase inhibitors interrupt HSP90•RASGRP1 and HSP90•CRAF interactions to upregulate BIM and circumvent drug resistance in lymphoma cells

Histone deacetylase (HDAC) inhibitors, which are approved for the treatment of cutaneous T cell lymphoma and multiple myeloma, are undergoing evaluation in other lymphoid neoplasms. How they kill susceptible cells is incompletely understood. Here we show that trichostatin A, romidepsin, and panobinostat induce apoptosis across a panel of malignant B cell lines, including lines that are intrinsically resistant to bortezomib, etoposide, cytarabine, and BH3 mimetics. Further analysis traces the pro-apoptotic effects of HDAC inhibitors to increased acetylation of the chaperone heat shock protein 90 (HSP90), causing release and degradation of the HSP90 client proteins RASGRP1 and CRAF, which in turn leads to downregulation of mitogen activated protein kinase pathway signaling and upregulation of the pro-apoptotic BCL2 family member BIM in vitro and in vivo. Importantly, these pro-apoptotic effects are mimicked by RASGRP1 siRNA or HSP90 inhibition and reversed by overexpression of constitutively active MEK1 or siRNA-mediated downregulation of BIM. Collectively, these observations not only identify a new HSP90 client protein, RASGRP1, but also delineate a complete signaling pathway from HSP90 acetylation through RASGRP1 and CRAF degradation to BIM upregulation that contributes to selective cytotoxicity of HDAC inhibitors in lymphoid malignancies.