pyrimidinones and Leukemia--Lymphocytic--Chronic--B-Cell

Purine nucleoside phosphorylase (PNP) catalyzes the reversible phosphorolysis of ribonucleosides and 2'-deoxyribonucleosides to their respective bases. Endogenous PNP deficiency leads to specific T-cell immunodeficiency, a genetic disease that has prompted the development of PNP inhibitors as potential therapies for T-cell-mediated diseases. PNP inhibition leads to the elevation of 2'-deoxyguanosine levels and accumulation of intracellular deoxyguanosine 5'-triphosphate, inducing cellular apoptosis. Forodesine is a highly potent, orally active, rationally designed PNP inhibitor that has shown activity in preclinical studies with malignant cells and clinical utility against T-cell acute lymphoblastic leukemia and cutaneous T-cell lymphoma. Additional preliminary findings support its use for the management of some B-cell malignancies.

Topics: Clinical Trials, Phase I as Topic; Clinical Trials, Phase II as Topic; Deoxyguanine Nucleotides; Humans; Leukemia, B-Cell; Leukemia, Lymphocytic, Chronic, B-Cell; Purine Nucleosides; Purine-Nucleoside Phosphorylase; Pyrimidinones

Forodesine is a new and potent purine nucleoside phosphorylase (PNP) inhibitor. Patients with chronic lymphocytic leukemia (CLL) with primary resistance to fludarabine-based therapy or with progressive disease were eligible for oral forodesine (200 mg/d) for up to 24 weeks. Eight patients with median lymphocyte count of 35.9 x 10(9)/L and median serum beta2 microglobulin level of 6.45 mg/L were treated. Six had Rai stage III to IV and were previously heavily treated (median prior therapy = 5). Two had transient decrease in lymphocyte count to normal, whereas in 5, disease progressed. Adverse events were mild. Steady-state level of forodesine ranged from 200 to 1300 nM and did not reach desired 2 microM level. PNP inhibition ranged from 57% to 89% and steady-state 2'-deoxyguanosine (dGuo) concentration median was 1.8 microM. Intracellular deoxyguanosine triphosphate (dGTP) increase was very modest, from median of 6 microM to 10 microM. Compared with in vivo, in vitro incubations of CLL lymphocytes with 10 or 20 microM dGuo and forodesine (2 microM) resulted in accumulation of higher levels of dGTP (40-250 microM) which resulted in increase in apoptosis. Forodesine has biologic activity in CLL; pharmacodynamic parameters suggest that an alternate dosing schedule and/or higher doses to achieve greater intracellular dGTP may be beneficial in this patient population.

Topics: Administration, Oral; Aged; Antineoplastic Agents; Apoptosis; Drug Administration Schedule; Drug Therapy, Combination; Enzyme Inhibitors; Female; Follow-Up Studies; Humans; Leukemia, Lymphocytic, Chronic, B-Cell; Lymphocyte Count; Lymphocytes; Male; Middle Aged; Phosphoric Monoester Hydrolases; Purine Nucleosides; Purine-Nucleoside Phosphorylase; Pyrimidinones; Severity of Illness Index; Vidarabine

Topics: Aged; Antineoplastic Combined Chemotherapy Protocols; Cell Transdifferentiation; Head and Neck Neoplasms; Histiocytic Sarcoma; Humans; Imidazoles; Leukemia, Lymphocytic, Chronic, B-Cell; Male; Oximes; Proto-Oncogene Proteins B-raf; Proto-Oncogene Proteins p21(ras); Pyridones; Pyrimidinones

The anti-leukemia agent forodesine causes cytotoxic overload of intracellular deoxyguanosine triphosphate (dGTP) but is efficacious only in a subset of patients. We report that SAMHD1, a phosphohydrolase degrading deoxyribonucleoside triphosphate (dNTP), protects cells against the effects of dNTP imbalances. SAMHD1-deficient cells induce intrinsic apoptosis upon provision of deoxyribonucleosides, particularly deoxyguanosine (dG). Moreover, dG and forodesine act synergistically to kill cells lacking SAMHD1. Using mass cytometry, we find that these compounds kill SAMHD1-deficient malignant cells in patients with chronic lymphocytic leukemia (CLL). Normal cells and CLL cells from patients without SAMHD1 mutation are unaffected. We therefore propose to use forodesine as a precision medicine for leukemia, stratifying patients by SAMHD1 genotype or expression.

Topics: Animals; Deoxyguanine Nucleotides; Drug Resistance, Neoplasm; Female; Humans; Leukemia, Lymphocytic, Chronic, B-Cell; Male; Mice; Mice, Inbred C57BL; Purine Nucleosides; Pyrimidinones; SAM Domain and HD Domain-Containing Protein 1

The CXCR4 receptor (Chemokine C-X-C motif receptor 4) is highly expressed in different hematological malignancies including chronic lymphocytic leukemia (CLL). The CXCR4 ligand (CXCL12) stimulates CXCR4 promoting cell survival and proliferation, and may contribute to the tropism of leukemia cells towards lymphoid tissues. Therefore, strategies targeting CXCR4 may constitute an effective therapeutic approach for CLL. To address that question, we studied the effect of Ulocuplumab (BMS-936564), a fully human IgG4 anti-CXCR4 antibody, using a stroma--CLL cells co-culture model. We found that Ulocuplumab (BMS-936564) inhibited CXCL12 mediated CXCR4 activation-migration of CLL cells at nanomolar concentrations. This effect was comparable to AMD3100 (Plerixafor--Mozobil), a small molecule CXCR4 inhibitor. However, Ulocuplumab (BMS-936564) but not AMD3100 induced apoptosis in CLL at nanomolar concentrations in the presence or absence of stromal cell support. This pro-apoptotic effect was independent of CLL high-risk prognostic markers, was associated with production of reactive oxygen species and did not require caspase activation. Overall, these findings are evidence that Ulocuplumab (BMS-936564) has biological activity in CLL, highlight the relevance of the CXCR4-CXCL12 pathway as a therapeutic target in CLL, and provide biological rationale for ongoing clinical trials in CLL and other hematological malignancies.

Topics: Actins; Antineoplastic Agents; Apoptosis; Benzylamines; Cell Movement; Cell Proliferation; Cell Survival; Chemokine CXCL12; Cyclams; Enzyme Activation; Heterocyclic Compounds; Humans; Imino Furanoses; Jurkat Cells; Leukemia, Lymphocytic, Chronic, B-Cell; Leukocytes, Mononuclear; Pyrimidinones; Reactive Oxygen Species; Receptors, CXCR4; Tumor Cells, Cultured; Tumor Suppressor Protein p53

Forodesine, a purine nucleoside phosphorylase inhibitor, displays in vitro activity in chronic lymphocytic leukemia (CLL) cells in presence of dGuo, which is the basis for an ongoing clinical trial in patients with fludarabine-refractory CLL. Initial clinical data indicate forodesine has significant activity on circulating CLL cells, but less activity in clearing CLL cells from tissues such as marrow. In tissue microenvironments, lymphocytes interact with accessory stromal cells that provide survival and drug-resistance signals, which may account for residual disease. Therefore, we investigated the impact of marrow stromal cells (MSCs) on forodesine-induced response in CLL lymphocytes. We demonstrate that spontaneous and forodesine-induced apoptosis of CLL cells was significantly inhibited by human and murine MSCs. Forodesine-promoted dGuo triphosphate (dGTP) accumulation and GTP and ATP depletion in CLL cells was inhibited by MSCs, providing a mechanism for resistance. Also, MSCs rescued CLL cells from forodesine-induced RNA- and protein-synthesis inhibition and stabilized and increased Mcl-1 transcript and protein levels. Conversely, MSC viability was not affected by forodesine and dGuo. Collectively, MSC-induced biochemical changes antagonized forodesine-induced CLL cell apoptosis. This provides a biochemical mechanism for MSC-derived resistance to forodesine and emphasizes the need to move toward combinations with agents that interfere with the microenvironment's protective role for improving current therapeutic efforts.

Topics: Animals; Apoptosis; Blotting, Western; Bone Marrow; Cell Proliferation; Cells, Cultured; Humans; Leukemia, Lymphocytic, Chronic, B-Cell; Lymphocytes; Mesenchymal Stem Cells; Mice; Myeloid Cell Leukemia Sequence 1 Protein; Proto-Oncogene Proteins c-bcl-2; Purine Nucleosides; Purine-Nucleoside Phosphorylase; Pyrimidinones; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Stromal Cells

We report the case of a patient with non-Hodgkin's lymphoma who, during chemotherapy according to the r-CHOP schedule (rituximab-cyclophosphamide-doxorubicin-vincristine and prednisone), showed a hepatic flare with jaundice. Given the patient's state of asymptomatic carrier of HBsAg, we began a treatment of telbivudine (600 mg/die), resulting in a regression of hepatitis flare and negativization of HBV viraemia.

Topics: Antibodies, Monoclonal, Murine-Derived; Antineoplastic Combined Chemotherapy Protocols; Antiviral Agents; Chemical and Drug Induced Liver Injury; Cholestasis, Intrahepatic; Cyclophosphamide; Cytomegalovirus; Cytomegalovirus Infections; Doxorubicin; Hepatitis B virus; Hepatitis B, Chronic; Humans; Hyperbilirubinemia; Immunocompromised Host; Immunosuppressive Agents; Leukemia, Lymphocytic, Chronic, B-Cell; Male; Middle Aged; Nucleosides; Prednisone; Pyrimidinones; Rituximab; Telbivudine; Thymidine; Vincristine; Viremia; Virus Activation

Chronic lymphocytic leukemia (CLL) is an incurable disease derived from the monoclonal expansion of CD5(+) B lymphocytes. High expression levels of ZAP-70 or CD38 and deletions of 17p13 (TP53) and 11q22-q23 (ATM) are associated with poorer overall survival and shorter time to disease progression. DNA damage and p53 play a pivotal role in apoptosis induction in response to conventional chemotherapy, because deletions of ATM or p53 identify CLL patients with resistance to treatment. Forodesine is a transition-state inhibitor of the purine nucleoside phosphorylase with antileukemic activity. We show that forodesine is highly cytotoxic as single agent or in combination with bendamustine and rituximab in primary leukemic cells from CLL patients regardless of CD38/ZAP-70 expression and p53 or ATM deletion. Forodesine activates the mitochondrial apoptotic pathway by decreasing the levels of antiapoptotic MCL-1 protein and induction of proapoptotic BIM protein. Forodesine induces transcriptional up-regulation of p73, a p53-related protein able to overcome the resistance to apoptosis of CLL cells lacking functional p53. Remarkably, no differences in these apoptotic markers were observed based on p53 or ATM status. In conclusion, forodesine induces apoptosis of CLL cells bypassing the DNA-damage/ATM/p53 pathway and might represent a novel chemotherapeutic approach that deserves clinical investigation.

Topics: Antibodies, Monoclonal; Antibodies, Monoclonal, Murine-Derived; Antineoplastic Agents; Antineoplastic Combined Chemotherapy Protocols; Apoptosis; Apoptosis Regulatory Proteins; Bcl-2-Like Protein 11; Bendamustine Hydrochloride; Cyclophosphamide; DNA-Binding Proteins; Dose-Response Relationship, Drug; Drug Evaluation, Preclinical; Gene Expression Regulation, Leukemic; Humans; Leukemia, Lymphocytic, Chronic, B-Cell; Membrane Proteins; Mitochondria; Nitrogen Mustard Compounds; Nuclear Proteins; Proto-Oncogene Proteins; Purine Nucleosides; Pyrimidinones; Rituximab; Tumor Cells, Cultured; Tumor Protein p73; Tumor Suppressor Protein p53; Tumor Suppressor Proteins; Vidarabine

Purine nucleoside phosphorylase (PNP) deficiency in humans results in T lymphocytopenia. Forodesine, a potent inhibitor of PNP, was designed based on the transition-state structure stabilized by the enzyme. Previous studies established that forodesine in the presence of deoxyguanosine (dGuo) inhibits the proliferation of T lymphocytes. A phase 1 clinical trial of forodesine in T-cell malignancies demonstrated significant antileukemic activity with an increase in intracellular dGuo triphosphate (dGTP). High accumulation of dGTP in T cells may be dependent on the levels of deoxynucleoside kinases. Because B-cell chronic lymphocytic leukemia (B-CLL) cells have high activity of deoxycytidine kinase (dCK), we hypothesized that these lymphocytes would respond to forodesine. This postulate was tested in primary lymphocytes during in vitro investigations. Lymphocytes from 12 patients with CLL were incubated with forodesine and dGuo. These CLL cells showed a wide variation in the accumulation of intracellular dGTP without any effect on other deoxynucleotides. This was associated with DNA damage-induced p53 stabilization, phosphorylation of p53 at Ser15, and activation of p21. The dGTP accumulation was related to induction of apoptosis measured by caspase activation, changes in mitochondrial membrane potential, and PARP cleavage. Based on these data, a phase 2 clinical trial of forodesine has been initiated for CLL patients.

Topics: Antineoplastic Agents; Apoptosis; B-Lymphocytes; Caspases; DNA Damage; Enzyme Inhibitors; Humans; Leukemia, Lymphocytic, Chronic, B-Cell; Lymphocytes; Mitochondria; Phosphorylation; Purine Nucleosides; Purine-Nucleoside Phosphorylase; Pyrimidinones; Pyrroles; T-Lymphocytes; Tumor Suppressor Protein p53