Combination Of Hydroxyurea Research Articles

Phase I Study of Combination Treatment with Hydroxyurea and Magnesium Pidolate in Children with Sickle Cell Anemia.

Red blood cell (RBC) sickling is promoted by increased intracellular deoxygenated Hb S concentration and via cell dehydration. Magnesium (Mg) can reduce RBC water loss through its negative regulation of K-Cl cotransport, a pathway which mediates cell dehydration. Hydroxyurea (HU) reduces sickling in part by increasing intracellular fetal hemoglobin (Hb F). The combination of HU and Mg pidolate, two drugs with distinct mechanisms of action, could offer additive or synergistic effects. We performed a phase I study of treatment with HU and Mg pidolate in children with sickle cell anemia (SCA), to estimate the maximum tolerated dose (MTD) and toxicity of this drug combination, and obtained preliminary data regarding cellular effects of this treatment. Children with SCA who had been treated with HU on a stable dose for a minimum of 6 months, received 6 months of treatment with Mg pidolate in addition to HU. The Mg dose was 0.6 mEq/kg/day for the first cohort of patients and was escalated by 50 % in each subsequent cohort to a maximum of 1.9 mEq/kg/d. HU was continued at the patients' pre-study dose. Compliance was measured using returned bottles and pills counts for both HU and Mg pidolate. Hematologic studies were performed at baseline, 3, and 6 months, and 3 months after Mg pidolate discontinuation (9 months). In vitro RBC adhesion to immobilized thrombospondin was measured under low shear flow conditions. Sixteen patients participated in the study; 9 were boys, and the median age was 7 years (range 4 – 12 years). All were African American and had Hb SS. The median HU dose was 28.5 mg/kg/day (range 25 to 30 mg/kg/d) and the median pre-study HU treatment duration was 1.9 years (range 0.7 – 8.4 years). The MTD for Mg pidolate used in combination with HU was 0.9 mEq/kg/day. The dose limiting toxicity (DLT) of Mg pidolate was diarrhea. There were 4 cases of grade III toxicity (all in the first 4 weeks of the study), 2 cases of grade II and one case of grade I diarrhea. There also were grade III (2), and grade II (3) abdominal pain events. There were no cases of hematologic toxicity, and no patients required HU dose reduction or interruption. Compliance was above 85 % for both drugs in 95 % of the visits. At baseline, high density RBC and KCl co-transport activity were much lower, and intracellular K was much higher than in untreated Hb SS RBC; these values remained relatively stable on Mg pidolate therapy. Mean RBC adhesion to thrombospondin at baseline was low (323 ± 286 RBCs/mm2) and decreased even further to 245 ± 161 RBCs/mm2 during Mg pidolate use. No significant changes in Hb, WBC, platelets, reticulocytes, Hb F, and MCV occurred. We conclude:The MTD for Mg pidolate when used in combination with HU for children with SCA is 0.9 mEq/kg/d,The most common dose-limiting toxicities from Mg pidolate are diarrhea and abdominal pain,There is no additional hematologic toxicity from HU therapy when Mg pidolate is added,RBC adhesion to endothelium may be further decreased in SCA patients treated with HU when Mg pidolate is added,HU therapy when used at 30 mg/kg/day in fully compliant patients may promote decreased RBC adhesion, higher intracellular K, and lower KCl co-transport activity.

Hydroxyurea with Azacitidine or Decitabine in Combination Is Antagonistic on DNA Methylation Inhibition.

5-azacytidine (azacitidine, Vidaza) and 5-aza-2′deoxycytidine (decitabine, Dacogen) are cytidine analogs currently used to treat myelodysplastic syndrome and as an investigational agent to treat acute myelogenous leukemia, sickle cell disease and other cancers. Decitabine is phosphorylated to a triphosphate form and incorporated into DNA where it can covalently trap DNA methyltransferase. Azacitidine is also phosphorylated to a triphosphate form, but requires reduction from a ribonucleotide to a deoxyribonucleotide by ribonucleotide reductase (RR) before incorporation into DNA. Hydroxyurea (Hydrea) is a drug routinely used to treat patients with leukemia and sickle cell disease. Hydroxyurea inhibits cell proliferation by inhibiting RR. Inhibition of RR leads to a depletion of nucleotide pools and cell cycle arrest in S-phase. Therefore, we hypothesized that the combination of hydroxyurea with azacitidine would be antagonistic to the ability of azacitidine to inhibit DNA methylation, and synergistic with decitabine in inhibiting DNA methylation. Hydroxyurea inhibits RR, which could block the conversion of azacitidine from a ribonucleotide to a deoxyribonucleotide, and therefore prevent its incorporation into DNA. In contrast, decitabine could increase its incorporation into DNA by taking advantage of a depletion of other deoxynucleotides induced RR inhibition by hydroxyurea. In order to test this hypothesis, we treated HL-60 (leukemia) and T24 (bladder cancer) cell lines with hydroxyurea in combination with either decitabine or azacitidine. DNA methylation was quantitated using Bisulfite-PCR Pyrosequencing of LINE-1 DNA repetitive elements, the MAGE-A1 gene and the p16 gene promoter region. We clearly showed that hydroxyurea at concentrations above 0.5 mM completely blocked the ability of azacitidine to inhibit DNA methylation (IC50=0.36 ± 0.04 mM). Surprisingly, we found that hydroxyurea at concentrations above 0.5mM also completely inhibited the effect of decitabine on DNA methylation (IC50=0.24 ± 0.06 mM). Further investigation showed that inhibition of the ability to block DNA methylation correlated with inhibition of the cell cycle. Using flow cytometry we clearly show that the antagonistic effect of hydroxyurea on DNA methylation inhibitors correlates with the arresting of cell division in S-phase. Aphidicolin, which inhibits DNA polymerase, also blocked the cell cycle and the ability of azacitidine and decitabine to inhibit DNA methylation. Thus, azacitidine and decitabine are S-phase specific drugs and are antagonized when used in combination with drugs that arrest the cell cycle. However, we also show that sequential treatment of hydroxyurea followed by azacitidine or decitabine could be used to avoid this antagonism. Therefore, due to the antagonistic effect of hydroxyurea with the mechanistic inhibitors of DNA methylation, azacitidine and decitabine, we recommend sequential combination treatment strategy.

CALCIUM CHANNEL ANTAGONISTS AUGMENT HYDROXYUREA- AND RU486-INDUCED INHIBITION OF MENINGIOMA GROWTH IN VIVO AND IN VITRO

Although the chemotherapy drug hydroxyurea (HU) and the antiprogesterone mifepristone (RU486) have been used to treat meningiomas for which surgical and radiation therapies have failed, results have been disappointing. The addition of calcium channel antagonists (CCAs) to chemotherapeutic drugs enhances tumor growth inhibition in other tumor types, and the authors demonstrated that CCAs can block meningioma growth in vitro and in vivo. The purpose of this study was to test the effects of the addition of a CCA to HU or RU486 on meningioma growth. Primary and malignant (IOMM-Lee) meningioma cell lines were treated with HU, RU486, or either of these plus diltiazem or verapamil. Assays for cell growth, apoptosis, and fluorescent-activated cell sorting were performed on in vitro cultures. Similar cell lines were implanted into nude mice and were treated with HU or RU486, in combination with a CCA. Tumors were analyzed by light microscopy, MIB-1, and factor VIII immunohistochemical staining studies. The addition of diltiazem or verapamil to HU or RU486 augmented meningioma growth inhibition by 20 to 60% in vitro. In vivo, tumors treated with combination drugs were smaller; and immunohistochemical analysis of the IOMM-Lee tumors showed a 10% decrease in the MIB-1 ratio (from 0.41 to 0.30) and an approximate 75% decrease in microvascular density. The addition of diltiazem or verapamil to HU or RU486 augments meningioma growth inhibition in vitro by inducing apoptosis and G1 cell-cycle arrest. The combination of HU and diltiazem inhibited the growth of meningiomas in vivo by decreasing proliferation and microvascular density. These results suggest a possible role for these drugs as an additional adjuvant therapy for recurrent or unresectable meningiomas.

Treatment with hydroxyurea and tyrphostin-1 significantly improves the transduction efficiency of recombinant adeno-associated viruses in human cancer cells

To enhance the transduction efficiency (TE) of a recombinant adeno-associated virus 2 (rAAV2) in human cancer cells, we examined the combined effects of various chemicals known to influence the rAAV2 transduction process at distinct steps. Among the agents tested were trichostatin A, a histone deacetylase inhibitor, MG-132, a proteosome inhibitor, the genotoxic agents hydroxyurea, aphidicolin, etoposide and camptothecin, and tyrphostin-1, an epidermal growth factor receptor inhibitor. During or after chemical treatment, various human cancer cells were infected with rAAV2 expressing beta-galactosidase. Treatment with hydroxy-urea or etoposide plus tyrphostin-1 dramatically increased the TE in most cell lines. The combination of hydroxyurea plus tyrphostin-1 increased TE to 37.7+/-7.9%, 32.8+/-2.0% and 31.8+/-2.1% in SK-Hep1, HeLa, and HCT116 cells, respectively. In addition, following rAAV2 infection and treatment with hydroxyurea plus tyrphostin-1, long-term transgene expression was observed for up to 6 months, with no damage to the transduced cells. These results indicate that rAAV2 transgene expression can be significantly enhanced by a combination of chemical agents with distinct activity and prolonged gene expression can occur following rAAV2 gene transfer into human cancer cells.

Optimal suppression of HIV replication by low-dose hydroxyurea through the combination of antiviral and cytostatic (‘virostatic’) mechanisms

The hydroxyurea-didanosine combination has been shown to limit immune activation (a major pathogenic component of HIV/AIDS) and suppress viral load by both antiviral and cytostatic ('virostatic') activities. Virostatics action represent a novel approach to attack HIV/AIDS from multiple directions; however, the use of these drugs is limited by the lack of understanding of their dose-dependent mechanism of action and by fear of pancreatic toxicity, even though a large review of ACTG studies has shown that hydroxyurea does not increase the incidence of pancreatitis. In vitro cytostatic and cytotoxic activity, inhibition of viral replication and immune activation by pharmacologically attainable plasma concentrations of hydroxyurea (10-100 micromol/l) and didanosine (1-5 micromol/l) were analyzed by cell proliferation, viability, apoptosis and infection assays using peripheral blood mononuclear cells. In vivo, 600, 900 and 1200 mg daily doses of hydroxyurea in combination with standard doses of didanosine and stavudine were studied in 115 randomized chronically infected patients. A cytostatic low (10 micromol/l) concentration of hydroxyurea inhibited cell proliferation and HIV replication in vitro. A gradual switch from cytostatic to cytotoxic effects was observed by increasing hydroxyurea concentration to 50-100 micromol/l, predicting that lower doses of hydroxyurea would be less toxic and more potent in vivo. The clinical results confirmed that 600 mg hydroxyurea was better tolerated, had fewer side effects and was more potent in suppressing HIV replication than the higher doses. A bimodal, dose-dependent, cytostatic-cytotoxic switch is an immune-based mechanism explaining the apparent paradox that lowering the dose of hydroxyurea to 600 mg daily induces maximal antiviral suppression in HIV-infected patients.

Imatinib and hydroxyurea in pretreated progressive glioblastoma multiforme: a patient series

Grade IV malignancies of the brain, such as glioblastoma multiforme (GBM), are associated with a dismal prognosis. Autocrine and paracrine loops of platelet-derived growth factor (PDGF) signaling, as well as other signal transduction pathways, have been postulated to play a role in glioblastoma transformation, and molecules involved in these pathways can potentially serve as targets for therapeutic inhibitory agents. Imatinib, an inhibitor of PDGF receptors alpha and beta, as well as other selected tyrosine kinases, is indicated for treatment of chronic myelogenous leukemia (CML) and gastrointestinal stromal tumor (GIST). Unfortunately, imatinib, as with many conventional chemotherapeutic agents, has limited efficacy as monotherapy in GBM. In preclinical studies, the chemotherapeutic agent hydroxyurea is demonstrated to have cytotoxic effects additive with imatinib. We tested the combination of hydroxyurea and imatinib in 30 grade IV progressive GBM patients refractory to chemo- and radiotherapy. All 30 patients were evaluable after a median 19 weeks observation time. Combination therapy with imatinib and hydroxyurea resulted in a 20% response rate, including complete and partial responses. Patients experiencing response or stable disease yielded a combined clinical benefit rate of 57%. Median time to progression was 10 weeks and median overall survival was 19 weeks. Three patients continue to survive on combination therapy, with the shortest duration being 106 weeks. Six-month and 2-year progression-free survival rates were 32% and 16%, respectively. The efficacy results, combined with findings that imatinib and hydroxyurea were well tolerated, suggest that this combination shows promise as therapy for GBM.

Hydroxyurea plus Didanosine as Maintenance Therapy for HIV-Infected Patients on Long-Term Successful Highly Active Antiretroviral Therapy

Background: Toxicity and quality of life issues have moved to delay the initiation of highly active antiretroviral therapy (HAART) and to explore novel treatment strategies for HIV infection. The switch to simpler regimens or treatment discontinuation has been attempted with limited success. The combination of hydroxyurea (HU) plus didanosine (ddI) is a simple regimen that might be able to restrain virus replication for long periods of time and could be an acceptable option as maintenance therapy in patients on prolonged successful HAART. Method: The combination of HU (500 mg bid) plus ddI (400 mg qd) was offered to participants with viral load (VL) <50 HIV RNA copies/mL and CD4 counts >350 cells/μL for more than 6 months under HAART. The prior HAART regimen was resumed if VL rose to >5,000 copies/mL and/or the CD4 count fell to <200 cells/μL after being on HU + ddI maintenance therapy. Results: A total of 187 participants replaced HAART with HU + ddI. In an intent-to-treat analysis at 48 weeks, 109 (58%) and 77 (41%) patients had VL below 5,000 and 500 HIV RNA copies/mL, respectively. The mean CD4 count dropped from 809 ± 283 to 573 ± 270 cells/μL, while 77% of patients remained above 350 cells/μL. The proportion of participants with hypercholesterolemia declined from 70% to 46% (p < .001), while those with hypertriglyceridemia fell from 36% to 21% (p < .05). Significant improvements in lipohypertrophy and lipoatrophy were observed in 52% and 64% of participants, respectively. Grade 3-4 toxicities appeared in 20 patients (11%), including 3 cases of pancreatitis and 1 of peripheral neuropathy. Prior history of VL >5 log, CD4 counts <200 cells/μL, and ddI experience were independently associated with lower response to HU + ddI maintenance therapy. Conclusion: The combination of HU + ddI may be a satisfactory maintenance therapy for more than half of patients on successful HAART who want to alleviate drug-related toxicities and/or pill burden. Patients with metabolic and/or body-shape abnormalities might particularly benefit from switching to this simple regimen.

Hydroxyurea in the treatment of HIV infection: clinical efficacy and safety concerns.

Data from basic science and clinical studies suggest that hydroxyurea (hydroxycarbamide)-based regimens are effective treatment options for patients with HIV at various stages of disease. In vitro studies of HIV-infected lymphocytes have shown that hydroxyurea: (i) inhibits viral DNA synthesis; (ii) synergistically interacts with nucleoside reverse transcriptase inhibitors (NRTI); and (iii) increases the antiviral activity of didanosine. Clinical studies have confirmed that hydroxyurea in combination with didanosine produces potent and sustained viral suppression in patients with HIV infection. However, some concerns have been recently raised on the use of hydroxyurea in association with NRTI. Hydroxyurea can cause myelosuppression, skin toxicities, mild gastrointestinal toxicity, and abnormalities of renal and liver functions. In addition, hydroxyurea may accentuate the toxic effects of nucleoside analogues. In fact, some clinical data seem to indicate an increased risk of pancreatitis and neuropathy when hydroxyurea is combined with didanosine and stavudine. Since hydroxyurea-related toxicity is dose dependent, a systematic study of hydroxyurea optimal dosage and schedule was initiated to monitor patients for possible nucleoside toxicity. In the Research Institute for Genetic and Human Therapy (RIGHT) 702 study it was shown that a low, well-tolerated hydroxyurea dose (600 mg daily) achieved better antiretroviral activity than higher doses, together with better CD4+ cell count increase and fewer adverse effects. In this paper the effects of hydroxyurea as salvage therapy for heavily pretreated patients with advanced HIV disease are presented. These studies have shown that some patients with extensive pretreatment experience and advanced disease can respond substantially to the addition of hydroxyurea. The addition of hydroxyurea to didanosine does not prevent the emergence of resistance to didanosine; nonetheless, the efficacy of this therapeutic regimen may not be attenuated by the presence of didanosine-resistant HIV mutants. Since CD4 T lymphocyte activation is essential for virus replication and CD8 T lymphocyte activation may contribute to pathogenesis, the combination of hydroxyurea with other drugs may lead to the inhibition of HIV, by blocking the 'cell activation-virus production-pathogenesis' cycle. Clinical data indicate that hydroxyurea may play a role in attenuation of viral rebound and immune reconstitution by decreasing CD4 T cell proliferation, as well as preventing the exhaustion of CD8 T cell populations that may result from excessive activation during HIV infection. While the combination of hydroxyurea with didanosine has provided hope, future studies including those that evaluate optimal dosing and long-term toxicity are needed to define the role for this agent in the treatment of HIV infection.

The HYDILE Trial: Efficacy and Tolerance of a Quadruple Combination of Reverse Transcriptase Inhibitors Versus the Same Regimen Plus Hydroxyurea or Hydroxyurea and Interleukin-2 in HIV-Infected Patients Failing Protease Inhibitor-Based Combinations

Purpose: To compare the efficacy and tolerance of a stavudine (d4T), didanosine (ddI), efavirenz (EFV), and abacavir (ABC) combination regimen with an identical regimen plus hydroxyurea (HU), or plus HU and interleukin-2 (IL-2), in patients failing protease inhibitor-based combinations and naive of EFV and ABC. Method: This was a randomized prospective trial in 69 HIV-infected patients recruited in one clinical center. Antiretroviral drugs were administered at standard doses according to weight. HU was added at week 6 at 500 mg twice daily. Three courses of IL-2 were given subcutaneously at 4.5 MU twice daily for 5 consecutive days, between weeks 24 and 40. The proportion of patients reaching plasma HIV-1 RNA <200 and <50 copies/mL was compared in the three trial groups at weeks 6, 24, and 48 using intent-to-treat and as-treated analyses. CD4+ T-cell count changes from baseline were also assessed at the same time points, along with anthropometric and metabolic measurements. Results: After 48 weeks, only 25% of patients receiving antiretrovirals had plasma HIV-1 RNA <200 copies/mL versus 59.1% in the group receiving HU and 56.5% in the group receiving HU and IL-2 (intent-to-treat; p < .01). At the 50 copies/mL cutoff, the results were 20.8%, 54.5%, and 47.8%, respectively. Most treatment discontinuations were due to failure in the first group and adverse events in the two others. A median decline of 27 CD4+ cells was observed in patients receiving antiretrovirals plus HU, against a gain of 78-118 cells at week 48 in patients receiving antiretrovirals alone or in combination with HU and IL-2. More patients were affected by clinical fat atrophy symptoms at week 48 than at baseline. Additionally, a trend toward increased cholesterol levels was observed throughout the study. Conclusion: During this trial, virologic response in patients failing previous regimens was clearly enhanced by the addition of HU, despite d4T and ddI recycling. Although adverse events were more frequent in the HU-containing arms, no unexpected toxicity was observed and the blunted CD4 response prompted by HU was corrected by the addition of IL-2. The combination of HU with reverse transcriptase inhibitors can therefore be regarded as a valuable alternative for patients with few remaining therapeutic options.

The HYDILE Trial: Efficacy and Tolerance of a Quadruple Combination of Reverse Transcriptase Inhibitors Versus the Same Regimen Plus Hydroxyurea or Hydroxyurea and Interleukin-2 in HIV-Infected Patients Failing Protease Inhibitor-Based Combinations

Purpose: To compare the efficacy and tolerance of a stavudine (d4T), didanosine (ddI), efavirenz (EFV), and abacavir (ABC) combination regimen with an identical regimen plus hydroxyurea (HU), or plus HU and interleukin-2 (IL-2), in patients failing protease inhibitor-based combinations and naive of EFV and ABC. Method: This was a randomized prospective trial in 69 HIV-infected patients recruited in one clinical center. Antiretroviral drugs were administered at standard doses according to weight. HU was added at week 6 at 500 mg twice daily. Three courses of IL-2 were given subcutaneously at 4.5 MU twice daily for 5 consecutive days, between weeks 24 and 40. The proportion of patients reaching plasma HIV-1 RNA <200 and <50 copies/mL was compared in the three trial groups at weeks 6, 24, and 48 using intent-to-treat and as-treated analyses. CD4+ T-cell count changes from baseline were also assessed at the same time points, along with anthropometric and metabolic measurements. Results: After 48 weeks, only 25% of patients receiving antiretrovirals had plasma HIV-1 RNA <200 copies/mL versus 59.1% in the group receiving HU and 56.5% in the group receiving HU and IL-2 (intent-to-treat; p < .01). At the 50 copies/mL cutoff, the results were 20.8%, 54.5%, and 47.8%, respectively. Most treatment discontinuations were due to failure in the first group and adverse events in the two others. A median decline of 27 CD4+ cells was observed in patients receiving antiretrovirals plus HU, against a gain of 78-118 cells at week 48 in patients receiving antiretrovirals alone or in combination with HU and IL-2. More patients were affected by clinical fat atrophy symptoms at week 48 than at baseline. Additionally, a trend toward increased cholesterol levels was observed throughout the study. Conclusion: During this trial, virologic response in patients failing previous regimens was clearly enhanced by the addition of HU, despite d4T and ddI recycling. Although adverse events were more frequent in the HU-containing arms, no unexpected toxicity was observed and the blunted CD4 response prompted by HU was corrected by the addition of IL-2. The combination of HU with reverse transcriptase inhibitors can therefore be regarded as a valuable alternative for patients with few remaining therapeutic options.

Complementary Antiviral Efficacy of Hydroxyurea and Protease Inhibitors in Human Immunodeficiency Virus-Infected Dendritic Cells and Lymphocytes

Dendritic cells are susceptible to human immunodeficiency virus (HIV) infection and may transmit the virus to T cells in vivo. Scarce information is available about drug efficacy in dendritic cells because preclinical testing of antiretroviral drugs has been limited predominantly to T cells and macrophages. We compared the antiviral activities of hydroxyurea and two protease inhibitors (indinavir and ritonavir) in monocyte-derived dendritic cells and in lymphocytes. At therapeutic concentrations (50 to 100 microM), hydroxyurea inhibited supernatant virus production from monocyte-derived dendritic cells in vitro but the drug was ineffective in activated lymphocytes. Concentrations of hydroxyurea insufficient to be effective in activated lymphocytes cultured alone strongly inhibited supernatant virus production from cocultures of uninfected, activated lymphocytes with previously infected monocyte-derived dendritic cells in vitro. In contrast, protease inhibitors were up to 30-fold less efficient in dendritic cells than in activated lymphocytes. Our data support the rationale for testing of the combination of hydroxyurea and protease inhibitors, since these drugs may have complementary antiviral efficacies in different cell compartments. A new criterion for combining drugs for the treatment of HIV infection could be to include at least one drug that selectively targets HIV in viral reservoirs.

Phase I clinical trial of parenteral hydroxyurea in combination with pelvic and para-aortic external radiation and brachytherapy for patients with advanced squamous cell cancer of the uterine cervix

Purpose : Oral hydroxyurea (HU) is a potent radiation sensitizer, but in vitro studies have suggested that prolonged exposure to HU by way of continuous parenteral infusion would enhance clinical efficacy. The objective of this study was to determine the maximal tolerated dose and identify the toxicities of continuous infusion HU in combination with pelvic and para-aortic external beam radiotherapy (RT) and intrauterine brachytherapy in patients with locally advanced carcinoma of the uterine cervix. Methods : This Phase I study of concomitant RT was designed with an escalating dose schedule of HU administered by continuous infusion. HU was administered parenterally as a continuous infusion, 5 d/wk, during the first 21 days of external radiation, during the final 5 days of external beam RT, followed by another 5-day infusion schedule bracketing the single fraction of brachytherapy. The maximal tolerated dose was defined as the highest dose level at which 3 of 3 or 5 of 6 patients could be treated without dose-limiting toxicity. Results : At dose level 1 (0.25 mg/m 2/min), 0 of 4 patients experienced Grade 4 toxicities and 2 patients experienced Grade 3 hematologic toxicities that were not considered dose-limiting. One of the first 4 patients at level 2 (0.375 mg/m 2/min) had Grade 3 diarrhea, but the 3 subsequent patients tolerated the dose. At level 3 (0.5 mg/m 2/min), 4 of 5 patients failed to complete therapy without a >7-day interruption in HU. Conclusions : The maximal tolerated dose of parenteral HU was 0.375 mg/m 2/min when administered with concomitant RT. The most common toxicities were hematologic. A new trial, incorporating concurrent cisplatin, HU, and RT is planned.

Chronic myeloid leukaemia with marked thrombocytosis in a patient with thalassaemia major: complete haematological remission under the combination of hydroxyurea and anagrelide

The co-existence of thalassaemia major and chronic myeloid leukaemia (CML) is a very rare event. We report a 32-year-old man with thalassaemia major whose progressively increasing leukocytosis and thrombocytosis led to the diagnosis of CML confirmed by the characteristic t(9;22)(q34;q11) chromosomal translocation and the bcr-abl (b3a2) DNA fusion. The patient was treated with hydroxyurea and anagrelide. This combination resulted in the satisfactory control of both the white blood cell and platelet counts, which has continued over the past 14 months with no major side-effects, albeit with no molecular response. The administration of hydroxyurea was also associated with a significant HbF increase.

Overexpression of cyclin A in human HeLa cells induces detachment of kinetochores and spindle pole/centrosome overproduction.

The combination of hydroxyurea (HU) and caffeine has been used for inducing kinetochore dissociation from mitotic chromosomes and for causing centrosome/spindle pole amplification. However, these effects on microtubule organizing centers (MTOCs) are limited to certain cell types. It was reasoned that if the biochemical differences in MTOC behavior between cells following HU treatment could be identified, then critical information concerning the regulation of these organelles would be obtained. During these studies, it was determined that cells from hamster, rat, and deer could be induced to enter mitosis with dissociated kinetochores and to synthesize centrosomes during arrest with HU, while cells from human and mouse could not. Comparisons between human HeLa cells and CHO cells determined that cyclin A levels were depressed in HeLa cells relative to CHO cells following HU addition. Overexpression of cyclin A in HeLa cells converted them to a cell type capable of detaching kinetochores from mitotic chromosomes. Ultrastructural analyses determined that the detached human kinetochores exhibited a normal plate-like morphology and appeared capable of associating with microtubules. In addition, HeLa cells overexpressing cyclin A also overproduced spindle poles during HU arrest, demonstrating that cyclin A activity also is important for centrosome replication during interphase. In summary, elevated cyclin A levels are important for the capacity of cells to be driven into mitosis by caffeine addition, for the ability of cells to progress to mitosis with detached kinetochores, and for centrosome/spindle pole replication.

Direct analysis of mitochondrial toxicity of antiretroviral drugs.

Mitochondrial toxicity is a serious side-effect of antiretroviral drugs, especially nucleoside reverse transcriptase inhibitors (NRTI). An in vitro assay to predict mitochondrial toxicity of in-use and developmental NRTI would be invaluable. To test the ability of a cytofluorimetric technique to predict the mitochondrial-dependent pancreatic and hepatic toxicity we used didanosine (ddI) alone or in combination with hydroxyurea (HU). The technique is based on the ability of the lipophilic cation JC-1 to enter selectively into mitochondria and change its colour as the membrane potential changes due to toxicity. Mitochondrial toxicity by HU and ddI was evaluated in pancreatic and hepatic human cell lines. The results were expressed as mitochondrial toxicity index (MTI), ranging from 0 to 100: the negative control was 0, and 100 indicating maximal toxicity. Dose-dependent pancreatic toxicity of ddI was evident after 14 days of culture (MTI 34 +/- 4 at 100 microM, 10 +/- 4 at 10 microM, 2 +/- 3 at 1 microM ddI). HU alone was not toxic (MTI 7 +/- 10 at 100 microM, 2 +/- 2 at 50 microM and 2 +/- 4 at 10 microM HU); however, HU increased the toxicity of high, but not low, concentrations of ddI. For example, the MTI of 10 microM ddI plus 50 microM HU was 54 +/- 9. Negligible mitochondrial toxicity was observed in the hepatic cell line exposed to ddI alone or in combination with HU. This in vitro assay might have in vivo relevance. First, ddI-related pancreatitis is dose dependent, and is reported more frequently than hepatic failure, consistent with our in vitro results. Second, patients who developed pancreatitis during randomized, controlled trials were treated with HU in combination with 400 mg ddI once daily (high peak concentration of ddI in the blood). In contrast, no pancreatitis was observed when HU was combined with 200 mg ddI twice daily (low peak concentration of ddI). These in vivo results are consistent with our in vitro observation that HU increases pancreatic cell toxicity in the presence of high concentrations of ddI. The in vitro assay described here might be used to predict the mitochondrial toxicity of other NRTI, alone or in combination.

Pancreatitis associated with hydroxyurea in combination with didanosine

Hydroxurea is a popular, but unlicensed, means of intensifying treatment in patients receiving didanosine, an inhibitor of nucleoside reverse transcriptase (a “nucleoside analogue”) used in combination with other retroviral drugs...

Cid1, a fission yeast protein required for S-M checkpoint control when DNA polymerase delta or epsilon is inactivated.

The S-M checkpoint is an intracellular signaling pathway that ensures that mitosis is not initiated in cells undergoing DNA replication. We identified cid1, a novel fission yeast gene, through its ability when overexpressed to confer specific resistance to a combination of hydroxyurea, which inhibits DNA replication, and caffeine, which overrides the S-M checkpoint. Cid1 overexpression also partially suppressed the hydroxyurea sensitivity characteristic of DNA polymerase delta mutants and mutants defective in the "checkpoint Rad" pathway. Cid1 is a member of a family of putative nucleotidyltransferases including budding yeast Trf4 and Trf5, and mutation of amino acid residues predicted to be essential for this activity resulted in loss of Cid1 function in vivo. Two additional Cid1-like proteins play similar but nonredundant checkpoint-signaling roles in fission yeast. Cells lacking Cid1 were found to be viable but specifically sensitive to the combination of hydroxyurea and caffeine and to be S-M checkpoint defective in the absence of Cds1. Genetic data suggest that Cid1 acts in association with Crb2/Rhp9 and through the checkpoint-signaling kinase Chk1 to inhibit unscheduled mitosis specifically when DNA polymerase delta or epsilon is inhibited.

Excess peripheral neuropathy in patients treated with hydroxyurea plus didanosine and stavudine for HIV infection

Hydroxyurea potentiates the action of some nucleoside reverse transcriptase inhibitors, and although its role in combination therapy has yet to be fully defined, it is commonly used in combination with didanosine (ddI) and stavudine (d4T). The use of hydroxyurea in HIV infection has recently been reviewed in detail [1] Although there have been no published reports of peripheral neuropathy in patients receiving hydroxyurea as part of anti-cancer chemotherapy, we have heard anecdotal reports that peripheral neuropathy is commoner in patients taking hydroxyurea as part of antiviral therapy. Neurotoxicity caused by hydroxyurea, presenting with confusion and encephalopathy (but not peripheral neuropathy), has recently been reported in a patient with HIV [2] We were prompted to examine this issue after observing peripheral neuropathy in five patients receiving ddI, d4T and hydroxyurea in combination with a range of other antiviral agents. In particular, we sought to test the hypothesis that hydroxyurea increases the frequency of peripheral neuropathy in patients receiving ddI and d4T. Computerized details of antiviral therapy prescribed at the Regional Infectious Diseases Unit are kept within the department. From the records of 938 patients who have been treated in the Unit, 88 treatment episodes were identified in which patients had received ddI and d4T simultaneously. These case notes were examined to determine whether patients had received hydroxyurea and whether they had developed treatment-limiting peripheral neuropathy. Neuropathy was considered to have been caused by antiviral therapy if it had not been present before the start of therapy, if the treating physician considered it to be caused by therapy, if therapy had been stopped or changed, and if neuropathy improved after this change or discontinuation. Hydroxyurea was given in 26 episodes, and seven (27%) of these episodes were complicated by peripheral neuropathy. Didanosine and d4T were given without hydroxyurea in 61 treatment episodes of which six (10%) were complicated by peripheral neuropathy. This difference did not quite achieve statistical significance (Fisher's two-tailed P = 0.053). No significant difference was found between the duration of therapy before the diagnosis of neuropathy in either group (Table 1).Table 1: The incidence of peripheral neuropathy in patients receiving didanosine and stavudine with or without hydroxyurea. Although the increased risk of neuropathy in the patients treated with hydroxyurea did not quite reach a statistically significant level, this is believed to be an important trend that requires further study. Rutschmann et al. [3] reported a similar trend towards more frequent and more severe neuropathy in patients receiving hydroxyurea as opposed to placebo with ddI and d4T in a controlled trial of 144 patients (25 and 14%, respectively). Combining these two sets of figures gives an incidence of peripheral neuropathy of all severities of 25.5% for patients on hydroxyurea versus 11.9% for patients not on hydroxyurea (Yates' χ2 = 6.39, P = 0.012). Thompson et al. [4] described a retrospective case–control study in which 23 patients who had received hydroxyurea in association with ddI, d4T, or both, were compared with 798 patients on similar regimens without hydroxyurea. Five (22%) of the patients exposed to hydroxyurea developed peripheral neuropathy compared with 40 (5%) of patients not exposed to hydroxyurea. In the past 4 years the number of anti-HIV drugs licensed in Europe has increased rapidly. It is now possible to choose in excess of 100 clinically reasonable three-drug regimens. In a recent survey of 54 patients attending our clinic it was found that 95 different drug combinations had been used (unpublished data). It is clearly no longer possible to assess the efficacy and toxicity of every possible antiviral combination by clinical trial, and it is likely that additive toxicities similar to the one suggested by the data reported in this study will only become apparent with widespread clinical use. In the United Kingdom the Committee on Safety of Medicines, in association with the MRC Clinical Trials Unit and the Medicines Control Agency, have set up an HIV adverse drug reactions reporting scheme, but as of September 1999, no association between neuropathy and hydroxyurea had been reported by that scheme, even though it is believed that this adverse effect is widely recognized by clinicians. There is clearly a need for clinicians to report adverse effects related to particular antiviral combinations. Jorge A Cepeda David Wilks

Concomitant radiochemotherapy for cancer of the cervix: critical analysis based on the Standards, Options and Recommendations methodology

The "Standards, Options and Recommendations" (SOR) project, started in 1993, is a collaboration between the National Federation of the French Cancer Centres (FNCLCC), the 20 French Cancer Centres (CRLCC) and specialists from French public universities, general hospitals and private clinics. The main objective is the development of clinical practice guidelines to improve the quality of health care and outcome for cancer patients. The methodology is based on literature review and critical appraisal by a multidisciplinary group of experts, with feedback from specialists in cancer care delivery. To update, according to the methodology of SOR, the Standards, Options and Recommendations for the management of patients with cancer of the cervix, and in particular, the place of concomitant radiochemotherapy. Data have been identified by a literature search using Medline (to April 1999) and the personal reference lists of experts. Once the guidelines were defined, the document was submitted for review to independent national and international reviewers and to the medical committees of the CRCC. The principle recommendations concerning the place of radiochemotherapy in the treatment of cancer of the cervix are 1/ the available data shows a significant increase in local control (level of evidence A) and of overall survival (level of evidence B1) following concomitant radiochemotherapy as compared to radiotherapy alone or the combination of radiotherapy-hydroxyurea. For stages IB, IIA, proximal IIB with bad prognostic factors (tumour size greater than 4 cm and/or invasion of pelvic nodes and/or microscopic invasion of the parametrium) and without lumbo-aortic nodal invasion, concomitant radiochemotherapy can be considered as standard treatment. This benefit is less clear for stages distal IIB, III and IVA without para-aortic nodal invasion (level of evidence C) and must be confirmed (expert agreement). 2/ the toxicity of radiochemotherapy is essentially haematologic and gastrointestinal (level of evidence B1) and is greater than that of radiotherapy alone (level of evidence B1). 3/ these results have been obtained by the combination of chemotherapy based oncisplatin alone, or in combination with 5-FU. Although of equal benefit, the toxicity of the cisplatin/5-FU/ hydroxyurea combination was greater than that of cisplatin alone in a trial comparing the two protocols. A significantly longer survival have also been obtained by the combination of chemoradiation and adjuvant chemotherapy with epirubicin (level of evidence C). These results must be confirmed. 4/ the exact means of delivering the chemotherapy has not been clearly established. In fact, in these trials, some protocols use cisplatin weekly at a dose of 40 mg/m2 and others every three or four weeks at doses ranging from 50 to 75 mg/m2. Subsequent randomised studies are likely to establish optimal schema for the delivery of chemotherapy when combined with external radiotherapy and brachytherapy.

Chloroquine exerts an additive in vitro anti-HIV type 1 effect when associated with didanosine and hydroxyurea.

Several groups, including ours, have reported that chloroquine (CQ) or its analog hydroxychloroquine has anti-HIV-1 activity both in vitro and in vivo. We studied in vitro whether the addition of CQ to the combination of hydroxyurea (HU) plus didanosine (ddI) had an additive effect in inhibiting the replication of HIV-1. Therefore both the H-9 T lymphocytic cell line and the U-937 promonocytic cell line as well as primary T cells and monocytes were infected with HIV-1 and then treated with HU at 0.2 mM and ddI at 1 microM and varying concentrations of CQ. Addition of CQ resulted in an additional inhibition of HIV-1 replication, as assessed by reverse transcriptase (RT) activity, with a CQ EC50 of 0.4-0.9 microM for the cell lines and of 0.2-0.9 microM for the primary cells. Similarly, addition of CQ further inhibited HIV-1 replication in U-1 cells stimulated either with LPS or H2O2 and in ACH-2 cells stimulated either with PMA or H2O2, with CQ EC50 values of 0.1 and 1 microM, respectively. Under the experimental conditions used, CQ induced neither toxicity nor apoptosis in the H-9 and U-937 cells. This in vitro additive anti-HIV-1 activity of CQ, in combination with HU + ddI, supports the idea that this triple regimen should be studied in clinical trials. It may become of particular interest to HIV-1-infected individuals from the developing world, in view of the low cost of both CQ and HU.