THE DUAL SYK/JAK INHIBITOR CERDULATINIB DEMONSTRATES RAPID TUMOR RESPONSES IN a PHASE 2 STUDY IN PATIENTS WITH RELAPSED/REFRACTORY B-CELL MALIGNANCIES

Relapsed CLL: sequencing, combinations, and novel agents

Although the therapy of chronic lymphocytic leukemia (CLL) has changed rapidly over the last 5 years, the key considerations in selecting a therapy for a previously treated patient with CLL continue to include the nature of the prior therapy and the duration of prior remission to that therapy, the prognostic features of the disease, and the health and comorbidities of the patient in question. For patients treated initially with chemoimmunotherapy, randomized trials have demonstrated the benefit of targeted therapy. Retrospective data suggest that ibrutinib is preferred as a first kinase inhibitor, whereas recent data with venetoclax and rituximab may challenge the choice of ibrutinib as a first novel agent in the relapsed setting. Data on sequencing of novel agents remain quite sparse, consisting of 1 prospective trial that demonstrated the efficacy of venetoclax in patients who have experienced progression with a kinase inhibitor, as well as a retrospective real-world analysis supporting this observation. Novel agents in advanced clinical development include primarily next-generation Bruton's tyrosine kinase and phosphatidylinositol 3-kinase δ inhibitors, with other classes still in phase 1 trials. Clinical trials of combination time-limited therapies with the goal of deep remission and discontinuation are also in progress.

Anti-adult T‑cell leukemia/lymphoma activity of cerdulatinib, a dual SYK/JAK kinase inhibitor

Adult T‑cell leukemia/lymphoma (ATLL) constitutes an aggressive malignancy caused by human T‑cell leukemia virus type 1 (HTLV‑1) that is resistant to available chemotherapeutics. The constitutive activation of Janus kinase (JAK)-signal transducer and activator of transcription (STAT) signaling is an important feature of ATLL, and spleen tyrosine kinase (SYK) is overexpressed in HTLV‑1-transformed T‑cell lines. In this study, we evaluated the effects of SYK- (PRT060318) or JAK- (JAK inhibitor 1) selective inhibitors and the dual SYK/JAK inhibitor, cerdulatinib, on the viability of HTLV‑1-transformed and ATLL-derived T‑cell lines. Cell proliferation, viability, cell cycle, apoptosis and intracellular signaling cascades were analyzed by the water-soluble tetrazolium-8 assay, flow cytometry and western blot analysis. HTLV‑1-infected T‑cell lines were sensitive to both SYK-selective and pan-JAK inhibitors, whereas cerdulatinib more potently suppressed cell proliferation and reduced cell viability than either of these agents alone. By contrast, the cytotoxic effects of cerdulatinib on uninfected T‑cell lines and peripheral blood mononuclear cells from a healthy donor were less pronounced. Cerdulatinib induced cell cycle arrest in the G2/M phase, which was associated with a decreased cyclin-dependent kinase 1 and cyclin B1, and an increased p21 and p27 expression. Hoechst staining revealed chromatin condensation and nuclear fragmentation in the cells treated with cerdulatinib, and an increased fraction of apoptotic APO2.7-stained cells was detected by flow cytometry. This corresponded to the activation of caspase-8, -9 and -3, and decreased levels of the anti-apoptotic factors, Bcl-xL, survivin, X-linked inhibitor of apoptosis (XIAP) and c‑FLIP. The cerdulatinib-induced decrease in cell viability was partly reversed by the caspase inhibitor, z‑VAD‑FMK. These anti-ATLL effects were associated with the suppression of SYK and JAK/STAT signaling, along with that of the downstream factors, AKT, ERK, activator protein‑1 and nuclear factor-κB. Finally, oral dosing with cerdulatinib lowered the tumor burden in a murine model of ATLL. Thus, our findings indicate that the simultaneous inhibition of therapeutically relevant targets, such as SYK and JAK is a more effective approach than single-agent therapy for the treatment of ATLL.