Lenalidomide in chronic lymphocytic leukemia: the present and future in the era of tyrosine kinase inhibitors

The role of phosphoric acid in the crystallization of lenalidomide form DH–water system

In this work, we studied the effect of phosphoric acid (0–10 v%), acting as an additive, on the thermodynamics and nucleation kinetics of the lenalidomide (LDM) latest form (DH).

IRF4 modulates the response to BCR activation in chronic lymphocytic leukemia regulating IKAROS and SYK

Interferon regulatory factor 4 (IRF4) is a transcriptional regulator of immune system development and function. Here, we investigated the role of IRF4 in controlling responsiveness to B-cell receptor (BCR) stimulation in chronic lymphocytic leukemia (CLL). We modulated IRF4 levels by transfecting CLL cells with an IRF4 vector or by silencing using small-interfering RNAs. Higher IRF4 levels attenuated BCR signaling by reducing AKT and ERK phosphorylation and calcium release. Conversely, IRF4 reduction improved the strength of the intracellular cascade activated by BCR engagement. Our results also indicated that IRF4 negatively regulates the expression of the spleen tyrosine kinase SYK, a crucial protein for propagation of BCR signaling, and the zinc finger DNA-binding protein IKAROS. We modulated IKAROS protein levels both by genetic manipulation and pharmacologically by treating CLL cells with lenalidomide and avadomide (IMIDs). IKAROS promoted BCR signaling by reducing the expression of inositol 5-phosphatase SHIP1. Lastly, IMIDs induced IRF4 expression, while down-regulating IKAROS and interfered with survival advantage mediated by BCR triggering, also in combination with ibrutinib. Overall, our findings elucidate the mechanism by which IRF4 tunes BCR signaling in CLL cells. Low IRF4 levels allow an efficient transmission of BCR signal throughout the accumulation of SYK and IKAROS.

Treatment of Lymphoid and Myeloid Malignancies by Immunomodulatory Drugs

Thalidomide and its derivatives (lenalidomide, pomalidomide, avadomide, iberdomide hydrochoride, CC-885 and CC-90009) form the family of immunomodulatory drugs (IMiDs). Lenalidomide (CC5013, Revlimid®) was approved by the US FDA and the EMA for the treatment of multiple myeloma (MM) patients, low or intermediate-1 risk transfusion-dependent myelodysplastic syndrome (MDS) with chromosome 5q deletion [del(5q)] and relapsed and/or refractory mantle cell lymphoma following bortezomib. Lenalidomide has also been studied in clinical trials and has shown promising activity in chronic lymphocytic leukemia (CLL) and non-Hodgkin lymphoma (NHL). Lenalidomide has anti-inflammatory effects and inhibits angiogenesis. Pomalidomide (CC4047, Imnovid® [EU], Pomalyst® [USA]) was approved for advanced MM insensitive to bortezomib and lenalidomide. Other IMiDs are in phases 1 and 2 of clinical trials. Cereblon (CRBN) seems to have an important role in IMiDs action in both lymphoid and myeloid hematological malignancies. Cereblon acts as the substrate receptor of a cullin-4 really interesting new gene (RING) E3 ubiquitin ligase CRL4CRBN. This E3 ubiquitin ligase in the absence of lenalidomide ubiquitinates CRBN itself and the other components of CRL4CRBN complex. Presence of lenalidomide changes specificity of CRL4CRBN which ubiquitinates two transcription factors, IKZF1 (Ikaros) and IKZF3 (Aiolos), and casein kinase 1α (CK1α) and marks them for degradation in proteasomes. Both these transcription factors (IKZF1 and IKZF3) stimulate proliferation of MM cells and inhibit T cells. Low CRBN level was connected with insensitivity of MM cells to lenalidomide. Lenalidomide decreases expression of protein argonaute-2, which binds to cereblon. Argonaute-2 seems to be an important drug target against IMiDs resistance in MM cells. Lenalidomide decreases also basigin and monocarboxylate transporter 1 in MM cells. MM cells with low expression of Ikaros, Aiolos and basigin are more sensitive to lenalidomide treatment. The CK1α gene (CSNK1A1) is located on 5q32 in commonly deleted region (CDR) in del(5q) MDS. Inhibition of CK1α sensitizes del(5q) MDS cells to lenalidomide. CK1α mediates also survival of malignant plasma cells in MM. Though, inhibition of CK1α is a potential novel therapy not only in del(5q) MDS but also in MM. High level of full length CRBN mRNA in mononuclear cells of bone marrow and of peripheral blood seems to be necessary for successful therapy of del(5q) MDS with lenalidomide. While transfusion independence (TI) after lenalidomide treatment is more than 60% in MDS patients with del(5q), only 25% TI and substantially shorter duration of response with occurrence of neutropenia and thrombocytopenia were achieved in lower risk MDS patients with normal karyotype treated with lenalidomide. Shortage of the biomarkers for lenalidomide response in these MDS patients is the main problem up to now.

IMiDs mobilize acute myeloid leukemia blasts to peripheral blood through downregulation of CXCR4 but fail to potentiate AraC/Idarubicin activity in preclinical models of non del5q/5q- AML

Treatment for acute myeloid leukemia (AML) remains suboptimal and many patients remain refractory or relapse upon standard chemotherapy based on nucleoside analogs plus anthracyclines. The crosstalk between AML cells and the BM stroma is a major mechanism underlying therapy resistance in AML. Lenalidomide and pomalidomide, a new generation immunomodulatory drugs (IMiDs), possess pleiotropic anti-leukemic properties including potent immune-modulating effects and are commonly used in hematological malignances associated with intrinsic dysfunctional BM such as myelodysplastic syndromes and multiple myeloma. Whether IMiDs may improve the efficacy of current standard treatment in AML remains understudied. Here, we have exploited in vitro and in vivo preclinical AML models to analyze whether IMiDs potentiate the efficacy of AraC/Idarubicin-based standard AML chemotherapy by interfering with the BM stroma-mediated chemoresistance. We report that IMiDs do not exert cytotoxic effects on either non-del5q/5q- AML cells nor BM-MSCs, but they enhance the immunomodulatory properties of BM-MSCs. When combined with AraC/Idarubicin, IMiDs fail to circumvent BM stroma-mediated resistance of non-del5q/5q- AML cells in vitro and in vivo but induce robust extramedullary mobilization of AML cells. When administered as a single agent, lenalidomide specifically mobilizes non-del5q/5q- AML cells, but not healthy CD34⁺ cells, to peripheral blood (PB) through specific downregulation of CXCR4 in AML blasts. Global gene expression profiling supports a migratory/mobilization gene signature in lenalidomide-treated non-del5q/5q- AML blasts but not in CD34⁺ cells. Collectively, IMiDs mobilize non-del5q/5q- AML blasts to PB through CXCR4 downregulation, but fail to potentiate AraC/Idarubicin activity in preclinical models of non-del5q/5q- AML.

Increased SHISA3 expression characterizes chronic lymphocytic leukemia patients sensitive to lenalidomide

Lenalidomide is a therapeutically effective drug in chronic lymphocytic leukemia (CLL). Twenty-seven CLL patients were treated with lenalidomide in a phase II clinical trial. Ten patients were grouped as responders (R) and 6 as nonresponders (NR). We evaluated T lymphocytes, NK, monocytes and dendritic cells at baseline and after treatment. A gene expression analysis was performed on 16 CLL samples collected before treatment. The levels of immune cells or immune-related cytokines are not different between R and NR patients. However, CLL patients sensitive to lenalidomide clearly show a peculiar gene expression profile in leukemic cells. The most up-regulated gene (fold change =  +23 in R vs. NR) is Wnt inhibitor SHISA homolog 3 (SHISA3). SHISA3^highCLL are characterized by a restrained activation of Wnt signaling and sensibility to lenalidomide-induced apoptosis. In conclusion, SHISA3 is a candidate gene for the identification of CLL patients who will benefit of lenalidomide treatment as single agent.

Pharmacotherapy of relapsed/refractory chronic lymphocytic leukemia

INTRODUCTION

The treatment of relapsed/refractory (RR) CLL has been revolutionized by the advent of the new oral inhibitors of B-cell receptor (BCR) signaling and the pro-survival protein, B-cell lymphoma 2 (BCL2). Additionally, new and more potent monoclonal antibodies against CD20 have replaced/may replace rituximab in many settings. Areas covered: Herein, we review the entire therapeutic landscape of RR CLL, with particular attention to the new small-molecule kinase inhibitors and BH3-mimetics. We discuss preclinical data with these agents in CLL, cover available efficacy and safety information, and examine potential resistance mechanisms and possible rational combinations to circumvent them. Expert opinion: The availability of potent and selective inhibitors of BCR signaling and of the anti-apoptotic functions of BCL2 has enormously enhanced our therapeutic armamentarium, with unprecedented efficacy now observed in patients who historically had poor outcomes with chemoimmunotherapy (CIT), e.g., those with deletion 17p/11q and/or IGHV-unmutated disease. The next challenge is to optimally sequence these agents and develop rational combinations that will hopefully lead to deeper and more durable remissions than ever seen before. Indeed, long term relapse free survival, already achievable with CIT in patients with genetically favorable-risk disease, now appears to be a realistic possibility for most patients with CLL.

Phase I-II study of lenalidomide and alemtuzumab in refractory chronic lymphocytic leukemia (CLL): effects on T cells and immune checkpoints

This phase I–II study explored safety, immunomodulatory and clinical effects of lenalidomide (weeks 1–16) and alemtuzumab (weeks 5–16) in 23 patients with refractory chronic lymphocytic leukemia. Most patients had Rai stage III/IV disease and were heavily pretreated (median 4 prior therapies), and 61% had del(17p)/del(11q). Eleven of 19 evaluable patients (58%) responded, with a median response duration of 12 months (1–29+); time to progression was short in non-responders. Lenalidomide had a narrow therapeutic dose range, 2.5 mg/day was not efficient, and maximum tolerated dose was 5 mg/day. Grade 3–4 neutropenia and thrombocytopenia occurred in 84 and 55%, 30% had febrile neutropenia, and CMV-reactivation requiring valganciclovir occurred in 30% of patients. The frequency of proliferating (Ki67⁺) CD8⁺ T cells was increased at week 4, with further increase in both the CD4⁺ and CD8⁺ subsets (p < 0.01 and <0.05), which was accompanied by significant upregulation of HLA-DR after addition of alemtuzumab. Antigen-experienced cells increased at week 4 as the frequency of effector memory cells increased in the CD8⁺ subset (p < 0.003), while effector cells decreased in both the CD8⁺ and CD4⁺ subsets (p < 0.0001 and p < 0.01). The Th1/Th2 balance was unchanged at week 4 but shifted toward a Th2 profile after combination therapy. At end of treatment, the frequency of Th17 and regulatory T cells was reduced (p < 0.01), naïve T cells decreased, and effector memory T cells increased (p < 0.05 and p < 0.01). Granzyme B⁺ T cells increased at 30-week follow-up (p < 0.05). PD-1 expression was unaffected. In conclusion, low-dose lenalidomide and alemtuzumab induced major perturbations of T cells, including increased proliferative activity and cytotoxic potential.

Alvocidib (flavopiridol) for the treatment of chronic lymphocytic leukemia

INTRODUCTION

Alvocidib, which has orphan drug designation in chronic lymphocytic leukemia (CLL) from the FDA and the EMA, is a plant-derived semisynthetic flavone that acts as a cyclin-dependent kinase inhibitor. It induces apoptosis in CLL cells in vitro and was introduced into clinical trials in CLL as an intravenous infusion in 1997, which proved disappointing. Since the drug avidly binds to plasma proteins, higher serum concentrations were required for clinical antileukemia activity than those suggested by in vitro studies. Subsequent studies utilizing bolus plus infusional doses revealed significant activity against CLL, even in patients with unfavorable characteristics. However, significant toxicity including high rates of major tumor lysis syndrome, cytokine release syndrome and secretory diarrhea were also observed.

AREAS COVERED

The chemistry, pharmacodynamics, pharmacokinetics and metabolism of alvocidib are briefly discussed and phase I-II studies in CLL are discussed in detail. To date, no phase III studies in CLL have been reported.

EXPERT OPINION

A number of much less toxic drugs with similar efficacy against CLL both with and without unfavorable cytogenetics have come to market. Furthermore, enthusiasm for the development of alvocidib as a single agent for the treatment of CLL has waned, primarily due to its toxicity.