Targeting BTK in B Cell Malignancies: From Mode of Action to Resistance Mechanisms.

The B cell receptor (BCR) signaling pathway plays a crucial role in B cell development and contributes to the pathogenesis of B cell neoplasms. In B cell malignancies, the BCR is constitutively active through both ligand-dependent and ligand-independent mechanisms, resulting in continuous Bruton tyrosine kinase (BTK) signaling activation, which provides a survival and proliferation advantage to the neoplastic clone. Among B cell malignancies, those in which the most significant results were obtained by treatment with BTK inhibitors (BTKi) include chronic lymphocytic leukemia, mantle cell lymphoma, lymphoplasmacytic lymphoma, and diffuse large B cell lymphoma. Covalent BTKi (namely ibrutinib, acalabrutinib, and zanubrutinib) functions by irreversibly blocking BTK through covalent binding to the cysteine residue 481 (Cys-481) in the ATP-binding domain. Despite the high efficacy and safety of BTKi treatment, a significant fraction of patients affected by B cell malignancies who are treated with these drugs experience disease relapse. Several mechanisms of resistance to covalent BTKi, including Cys-481 mutations of BTK, have been investigated in B cell malignancies. Non-covalent BTKi, such as pirtobrutinib, have been developed and proven effective in patients carrying both Cys-481-mutated and unmutated BTK. Moreover, targeting BTK with proteolysis-targeting chimeras (PROTACs) represents a promising strategy to overcome resistance to BTKi in B cell neoplasms.

Treatment Refractoriness in Chronic Lymphocytic Leukemia: Old and New Molecular Biomarkers.

Chronic lymphocytic leukemia (CLL) is the most common leukemia in adults. Despite its indolent clinical course, therapy refractoriness and disease progression still represent an unmet clinical need. Before the advent of pathway inhibitors, chemoimmunotherapy (CIT) was the commonest option for CLL treatment and is still widely used in areas with limited access to pathway inhibitors. Several biomarkers of refractoriness to CIT have been highlighted, including the unmutated status of immunoglobulin heavy chain variable genes and genetic lesions of TP53, BIRC3 and NOTCH1. In order to overcome resistance to CIT, targeted pathway inhibitors have become the standard of care for the treatment of CLL, with practice-changing results obtained through the inhibitors of Bruton tyrosine kinase (BTK) and BCL2. However, several acquired genetic lesions causing resistance to covalent and noncovalent BTK inhibitors have been reported, including point mutations of both BTK (e.g., C481S and L528W) and PLCG2 (e.g., R665W). Multiple mechanisms are involved in resistance to the BCL2 inhibitor venetoclax, including point mutations that impair drug binding, the upregulation of BCL2-related anti-apoptotic family members, and microenvironmental alterations. Recently, immune checkpoint inhibitors and CAR-T cells have been tested for CLL treatment, obtaining conflicting results. Potential refractoriness biomarkers to immunotherapy were identified, including abnormal levels of circulating IL-10 and IL-6 and the reduced presence of CD27+CD45RO- CD8+ T cells.

Assessment of regulatory T cells (Tregs) and Foxp3 methylation level in chronic myeloid leukemia patients on tyrosine kinase inhibitor therapy.

The key cell population permits cancer cells to avoid immune-surveillance is regulatory T cells (Tregs). This study evaluates the level of Tregs in chronic myeloid leukemia (CML) patients and the effect of Tyrosine kinase inhibitor (TKI) on Treg levels, as a pathway to understand the immune response and behavior among advance stage and optimal response CML patients using imatinib therapy. Blood samples were collected from 30 CML patients (optimal response to TKI), 30 CML patients (failure response to TKI), and 30 age- and gender-matched controls. Analysis involved measuring percentages of Tregs (CD4 + CD25 + FOXP3 +) by flow cytometer and demethylation levels of FOXP3 Treg-specific demethylated region (TSDR) by PCR. The data revealed that Tregs and the FOXP3-TSDR demethylation percentages significantly increased in failure response group in comparison to the optimal response and control groups, while no significant difference between optimal response and control groups. Tregs and FOXP3 TSDR demethylation percentages showed high sensitivity and specificity, suggesting powerful discriminatory biomarkers between failure and optimal groups. An assessment of the Tregs and demethylation percentage among different BCR-ABL levels of CML patients on TKI revealed no significant differences in parameter percentage in the optimal response to TKI patients with different molecular responses (log 3 reduction or other deeper log 4.5 and 5 reduction levels). Our findings demonstrate an effective role of functional Tregs among different CML stages. Also, the study suggests that the major molecular response to therapy at level 0.1% of BCR-ABL transcript could be enough to induce immune system restoration in patients.

The Efficacy of Fludarabine, High Dose Cytosine Arabinoside with Granulocyte Colony Stimulating Factor (FLAG) Protocol as Salvage Therapy for Refractory/Relapsed Acute Leukemias in Adult Iraqi Patients.

Refractory/relapsed acute leukemia has always been a challenging problem for hematologist. Over the past decade emphasis has been made in the development of regimens containing fludarabine, combined with cytosine arabinoside for the treatment of refractory/relapsed acute leukemias. The aim of this study is to evaluate the efficacy and toxicity of the combination of fludarabine, high dose cytarabine, and granulocyte colony stimulating factor in refractory relapsed cases of acute leukaemia, a prospective study is being conducted at the National Center of Hematology and hematology unit/Baghdad teaching hospital from July 2008 to July 2010. Twenty Patients with refractory/relapsed acute leukemia were treated with fludarabine 30 mg/m(2) and cytosine arabinoside (Ara-C) 2 g/m(2) for 5 days, and granulocyte colony stimulating factor G-CSF 300 µg/day from day 0 till neutrophil recovery (ANC > 1.0 × 10(9)/L). Response was evaluated by bone marrow examination on day 30 post chemotherapy. Patients included were refractory acute lymphoblastic leukemia (ALL) (five patients), relapsed ALL (four patients), refractory acute myeloid leukemia (AML) (eight patients), relapsed AML (three patients). Complete remission (CR) was achieved in nine (45 %) patients, while three (15 %) patients got partial remission. Three (15 %) patients died because of post chemotherapy complications and five (25 %) patient failed to achieve remission. Major complications encountered were: anemia, fever, bleeding, mucositis and bacterial infections. FLAG protocol is well tolerated and effective regimen in relapsed/refractory acute leukemias. The toxicity is acceptable, enabling most patients to receive further treatment, including transplantation procedures.

Assessment of interleukin 1ß serum level in different responder groups and stages of chronic myeloid leukemia patients on imatinb mesylate therapy.

Chronic myeloid leukemia (CML) is a myeloproliferative disorder characterized by the presence of an acquired mutation which affects the hematopoietic stem cell, leading to a striking overproduction of immature granulocytes. The first important clue to its pathogenesis the Philadelphia chromosome created by a reciprocal translocation between chromosomes 9 and 22 (t [9; 22] [q34; q11]). The development of the BCR-ABL-targeted imatinib mesylate represents a paradigm shift in the treatment of CML. Imatinib displays inhibitory activity against other kinase(s) that play a role in monocyte/macrophage development. Accordingly many studies revealed the role of cytokines in pathophysiology of myeloid neoplasia including participation of IL-1ß in the pathogenesis of CML. This study designed to assess the behavior of IL-1ß through newly diagnosed patients, different responders groups (optimal, suboptimal and failure cytogenetic response) and advanced stages (acceleration and crisis groups) of CML Iraqi patients whom receiving Imatinib mesylate (tyrosine kinase inhibitor), trying to elucidate the role of immunity in pathophysiology of CML disease development and treatments. In this study 96 Iraqi CML patients under imatinib mesylate treatment categorized by complete blood picture and fluorescent in situ hybridization analysis into different response groups and stages, then used an enzyme linked immunosorbent assay technique to assess serum level of IL-1ß in each response group and advance stage (acceleration and transformed) of CML patients, in comparison to level in 32 healthy control subjects and 32 newly diagnosed CML. Out of 128 patients the mean serum of interleukin 1ß level (pg/ml) for the newly diagnosed, optimal responded, suboptimal responded, failure cytogenetic and advance stage of CML were 6.53 ± 3.81, 18.47 ± 4.29, 18.69 ± 3.03, 5.73 ± 2.44, and 18.10 ± 3.10, respectively. While healthy was 12.17 ± 3.44. The measurement of IL-1ß before and during treatment of CML patients may contribute to the early identification of responder and non responder patients, and help in the earlier choice and/or design of alternative therapeutic strategies.

Evaluation of the safety of imatinib mesylate in 200 iraqi patients with chronic myeloid leukemia in the chronic phase: single-center study.

OBJECTIVE: Imatinib mesylate, a tyrosine kinase inhibitor, is presently the drug of choice for chronic myeloid leukemia (CML). During therapy, a few patients may develop hematological and non-hematological adverse effects. MATERIALS AND METHODS: The aim of this study was to evaluate the safety of imatinib therapy in patients with CML. Between December 2007 and October 2009 two hundred patients with CML in chronic phase were included in the study. Written informed consent was obtained from all patients prior to the start of the study. Imatinib was started at 400 mg orally daily. Patients were monitored carefully for any adverse effects. Complete blood count, liver, and renal function tests were done once in 2 weeks during the first month and on a monthly basis during follow-up. Toxicities that encountered were graded as per the National Cancer Institute common toxicity criteria version 2. Both hematologic and non-hematologic toxicities were managed with short interruptions of treatment and supportive measures, but the daily dose of imatinib was not reduced below 300 mg/day. RESULTS: Two hundred CML patients in chronic phase were included in this study; the male:female ratio was 0.7:1 with mean age 39.06±13.21 years (ranged from 15-81 years). The study showed that the commonest hematological side effects were grade 2 anemia (12.5%) followed by leukopenia (8%) and thrombocytopenia (4%), while the most common non-hematological adverse effects were superficial edema and weight gain (51.5%), followed by musculoskeletal pain (35.5%), then gastro-intestinal symptoms (vomiting, diarrhea) (19%). Fluid retention was the commonest side effect, which responded to low-dose diuretics. The drug was safe and well tolerated. There were no deaths due to toxicity. CONCLUSION: Imatinib mesylate a well-tolerated drug, and all undesirable effects could be ameliorated easily. The most common hematological and non-hematological side effects were anemia and fluid retention, respectively Conflict of interest:None declared.