A prospective, randomised, phase II study of horse antithymocyte globulin vs rabbit antithymocyte globulin as immune-modulating therapy in patients with low-risk myelodysplastic syndromes.

Immunosuppression has recently been proposed for low-risk myelodysplastic syndromes (MDS) to reverse bone marrow failure by inhibiting intramedullary secretion of proapoptotic cytokines. We treated 35 MDS patients (24 refractory anaemia (RA), 10 RA with excess blasts and one chronic myelomonocytic leukaemia) with either horse antithymocyte globulin 15 mg/kg/day or rabbit antithymocyte globulin 3.75 mg/kg/day, each for 5 days. Median age was 63 years (range: 41-75). After 1 to 34+ months of follow-up (mean: 15+), four patients experienced complete haematological responses (CR), six good responses (GR) and two minor responses. All CRs and GRs occurred in patients with RA, in whom both horse and rabbit ATG yielded five responses out of 12 (42%). Time to response varied between 1 and 10 (mean: 3) months. The median duration of response was 9+ (1-17+) months; five patients are in continuing response. In all, 23 patients suffered side effects > degrees II WHO (the degree of toxicity encountered according to the internationally accepted WHO toxicity grading); one patient died 2 weeks after rabbit ATG from rhinocerebral mucormycosis. Parameters that correlated with response were duration of disease and RA subgroup. In our experience, immune-modulating therapy with either horse or rabbit ATG is feasible in patients with RA and short duration of disease.

Favourable response to antithymocyte or antilymphocyte globulin in low-risk myelodysplastic syndrome patients with a 'non-clonal' pattern of X-chromosome inactivation in bone marrow cells.

OBJECTIVE: Antithymocyte and antilymphocyte globulin (ATG/ALG) have a therapeutic effect in about 30% of patients with myelodysplastic syndromes (MDS). We were interested to know whether responding patients achieve clonal or polyclonal remissions. PATIENTS: Ten women with low-risk MDS received either ALG or ATG. Before treatment and 3, 6, and 12 months later, X-chromosome inactivation patterns of peripheral blood T lymphocytes were compared with those of peripheral blood granulocytes or bone marrow cells, using the human androgen receptor gene assay and the phosphoglycerate kinase-1 assay. RESULTS: Six women did not respond to therapy. Prior to treatment, four of them had a monoclonal, one had an oligoclonal, and one had a skewed X-chromosome inactivation pattern (XCIP). Four patients responded to ATG/ALG. Three of them were informative in our X-inactivation assays, and showed a non-clonal XCIP which did not change significantly after treatment with ATG/ALG. CONCLUSION: A non-clonal XCIP in the bone marrow was associated with a response to ATG/ALG. Non-clonal XCIPs do not necessarily imply that there is no pathological clone. By definition, they just indicate that there is no evidence of a clone contributing more than 50% of cells in a sample. Non-clonal XCIPs may therefore be attributable to incomplete clonal expansion. This, in turn, might be explained by a vigorous immune attack against the MDS clone, which simultaneously causes collateral damage in the remaining normal haemopoiesis. In such patients, ATG/ALG may improve normal haemopoiesis by relieving the immunological pressure on the innocent bystanders.

Clinical phase I dose escalation and pharmacokinetic study of high-dose chemotherapy with treosulfan and autologous peripheral blood stem cell transplantation in patients with advanced malignancies.

A Phase I dose escalation and pharmacokinetic study of the alkylating cytotoxic agent treosulfan was conducted to evaluate the maximum tolerated dose and the dose-limiting toxicities in patients with advanced malignancies rescued by autologous peripheral blood stem cell transplantation. Twenty-two patients (15 ovarian and 7 other carcinomas/lymphomas) with a median age of 48 years were treated with 28 high-dose courses. Treosulfan was infused over 2 h at escalating doses from 20 to 56 g/m2, and pharmacokinetic parameters were analyzed. At 56 g/m2, three of six patients experienced dose-limiting toxicities: diarrhea grade III/IV in three patients; mucositis/stomatitis grade III in one patient; toxic epidermal necrolysis in one patient; and grade III acidosis in one patient. Other low-grade side effects, including erythema, pain, fatigue, and nausea/vomiting, were recorded. Two patients died within 4 weeks after treatment because of rapid tumor progression and fungal infection, respectively. Plasma half-life, distribution volume, and renal elimination of treosulfan were independent of dose, whereas the increase in area under the curve was linear up to 56 g/m2 treosulfan. The maximum tolerated dose of high-dose treosulfan is 47 g/m2. A split-dose or continuous infusion regimen is recommended for future high-dose trials. In consideration of antineoplastic activity and limited organ toxicity, inclusion of high-dose treosulfan in combination protocols with autologous peripheral blood stem cell transplantation seems worthwhile.

Absence of N-RAS point mutations in peripheral blood cells of patients with aplastic anaemia and paroxysmal nocturnal haemoglobinurea.

The myelodysplastic syndromes (MDS) have a significant frequency of evolution into acute myeloid leukaemia (AML). Approximately 30% of MDS patients show activating mutations of the N-RAS proto-oncogene, and these patients are at increased risk of leukaemic evolution. Long-term survivors of aplastic anaemia (AA) and paroxysmal nocturnal haemoglobinurea (PNH) are also at significant risk of developing AML. We have screened peripheral blood DNA from 42 AA patients and 15 PNH patients for the presence of N-RAS point mutations. No mutations were detected in these samples, indicating that the mechanisms of evolution into AML may be different from those in MDS.

Childhood polyclonal T cell lymphocytosis with neutropenia: effects of antilymphocyte globulin and granulocyte colony stimulating factor in vitro and in vivo.

The pathogenesis of the neutropenia that occurs in some patients with chronic T cell lymphocytosis is not well understood. We have investigated a 15-year-old girl with this syndrome. Initial committed bone marrow progenitor numbers (CFUgm) were low but markedly increased in vitro following T cell depletion. Similarly a transient correction of neutropenia was observed following in vivo lymphocyte depletion with antilymphocyte globulin. A sustained neutrophil recovery was achieved with daily therapy using recombinant human granulocyte colony stimulating factor (rhG-CSF) despite persistence of the lymphocytosis; during successful therapy CFUgm numbers remained low, and were not increased by the in vitro addition of rhG-CSF. These observations suggest the possibility of an inhibitory regulatory mechanism specifically acting on neutrophil granulopoiesis.

Acquired aplastic anemia and paroxysmal nocturnal hemoglobinuria: studies on clonality.

We used X-chromosome methylation patterns to study clonality in aplastic anemia (AA) and paroxysmal nocturnal hemoglobinuria (PNH). AA is usually not considered to be a clonal stem cell disorder, although this has not been directly investigated. PNH is generally assumed to be a clonal disorder, although there is contradictory evidence. Methylation analysis was performed on DNA from separated granulocytes and mononuclear cells, using the M27 beta and hypoxanthine phosphoribosyl transferase (HPRT) probes. Six of seven AA patients showed a polyclonal pattern of X inactivation. In contrast, five of five PNH patients showed a monoclonal pattern. These results imply that at least 80% of the cell population derives from a single stem cell. Because this high proportion of PNH cells might be considered surprising, three patients were studied for membrane expression of decay accelerating factor (DAF). In support of the DNA data, more than 95% of the granulocytes were DAF--ve in all three cases. We conclude that AA is predominantly a polyclonal disorder, whereas PNH is a clonal stem cell disorder. Our data support a model in which a single PNH stem cell has a growth advantage over other remaining stem cells and eventually dominates hematopoiesis.