We studied the effects of recombinant interferon alpha-2a (IFN-alpha) in 36 patients with polycythemia vera (PV) previously treated with phlebotomy and/or conventional cytostatic agents. In each patient, after at least 2 months of discontinuation of any cytotoxic therapy, the hematocrit (Hmt) was first brought to normal value by phlebotomy; IFN-alpha treatment was then begun at a starting dose of 3,000,000 IU s.c. three times a week. Response to treatment, which was assessed monthly, was defined as persistent normalization of Hmt without concomitant phlebotomy; in non-responsive patients the initial IFN-alpha weekly dosage was progressively increased. Twenty patients were responsive with a median duration of response of 7 months (range 2-25+ months); out of these, 7 patients are still under treatment and responsive at 13+, 17+, 20+, 22+, 23+, 25+, 25+ months. These findings indicate that a cohort, although small, of patients with PV (19.4%) are persistently sensitive to IFN-alpha; in this subset of patients, this cytokine can therefore provide a useful treatment option, since, contrary to conventional therapeutic approaches such as radioactive phosphorus, cytostatic agents, or phlebotomy, IFN-alpha is devoid of harmful side effects.

No abstract

No abstract

We report on long‐term therapeutic efficacy and toxicity of recombinant interferon‐alpha 2a (rIFN‐alpha) in a series of 38 patients with polycythaemia vera (PV). In all patients haematocrit was first brought into the normal range by venesection; rIFN‐alpha was then begun at a starting weekly dose of 9,000,000 IU. Complete response (CR) was defined as persistence of normal haematocrit without venesection and partial response (PR) as >50% reduction of phlebotomy requirement. Eleven patients (28.9%) achieved CR and 8 (21.0%) PR. Median duration of treatment for all responsive patients was 40 months; 12 patients are still responsive and under treatment after 13, 15, 25, 35, 40, 41, 43, 49, 50, 51, 52 and 52 months of therapy with rIFN‐alpha. In responsive patients, rIFN‐alpha also normalized leucocyte counts, platelet counts and spleen enlargement; rIFN‐alpha also relieved generalized pruritus in all 10 patients displaying this symptom. Early toxicity (flu‐like syndrome) was observed in 23.6% and late toxicity (severe weakness) in 13.1% of patients, requiring rIFN‐alpha treatment suspension in all cases. Progression to leukaemia was observed in none of the 10 patients treated only with rIFN‐alpha and in one of the 12 who received alkylating agents before enrolment in this study. According to these data, rIFN‐alpha seems to be an effective and safe treatment option for PV.

The last few years have seen an enormous increase in our knowledge on the haematopoietic growth factor erythropoietin (Epo), firstly with its purification and determination of its primary amino acid sequence, and more recently with the isolation of the Epo gene and its expression in mammalian cell lines. This review article summarizes the crucial biological features of Epo and critically examines the main results obtained in clinical trials on humans.