Natural IFN-alpha therapy in hairy-cell leukaemia (namalva-type IFN--Wellferon).

More than 50 patients with hairy-cell leukaemia have now been entered into the British Wellferon (IFN) study, at different centres under the coordination of the Wellcome Research Laboratories. While the treatment duration and dosage varied between patients, the initial dose was usually 3 megaunits daily by intramuscular or subcutaneous injection. Although flu-like symptoms and mild somnolence were commonly experienced side-effects; cessation of IFN treatment as a result of such effects was necessary in only three patients. All patients irrespective of previous treatment showed some response and a complete (less than 5% hairy cells, HCs) bone marrow response was observed in 17. The degree of response was related to the duration of therapy. Immunological markers showed that there was no apparent increase in natural killer (NK) cells and no return of normal B lymphocytes. Light-chain-restricted B cells became reduced in parallel with the disappearance of morphological HCs. Absolute numbers of T cells were reduced, Leu2a+ preferentially, resulting in an increase in helper/suppressor ratios. The ratios (saturation index, SI) of saturated to unsaturated 18 carbon fatty acids (C18FA) of erythrocyte or leukocyte membranes, while abnormal in untreated patients, approached normal levels during IFN therapy. It is concluded that prolonged alpha IFN therapy is highly effective in HCL. The mechanism of action of IFN remains unknown, but indirect surface-marker data favours a direct effect on HCs.