Treatment of Ph'-positive chronic myelogenous leukemia (CML) with recombinant interferon alfa-2b (Intron A)

Clinical use of biologic response modifiers in cancer treatment: an overview. Part I. The interferons

Interferons are proteins with antiviral, antiproliferative, and immune-regulating activity. They are classified as alfa, beta, or gamma on the basis of antigenicity and biologic properties. Alfa interferons as single-agent therapy produce clinical improvement in approximately 90 percent of patients with hairy-cell leukemia, and up to 70 percent of patients with chronic myelogenous leukemia (CML) in early-stage disease. Prolonged suppression or elimination of the leukemic cell clone by interferon may ultimately increase survival of patients with CML. Interferon is not effective single-agent therapy for multiple myeloma, but improves response rate when combined with conventional agents. AIDS-associated Kaposi's sarcoma demonstrates a 40 percent objective response rate to interferon, with less risk of immune system suppression than conventional cytotoxics. Other applications of alfa interferon include malignant melanoma and renal cell carcinoma. Beta interferon is similar to the alfa subtype and may have utility in treatment of brain tumors. Gamma interferon is an important immune regulator with qualitative and quantitative differences in its efficacy and toxicity when compared with alfa interferon.

Recombinant interferon-alpha-2C in chronic myelogenous leukaemia: relationship of sensitivity of committed haematopoietic precursor cells in vitro (BFU-E, CFU-GM, CFU-Meg) and clinical response

In an ongoing phase-II trial we aimed to predict clinical responsiveness of Philadelphia chromosome positive (Ph1+) chronic myelogenous leukaemia (CML) to recombinant IFN-alpha-2C (rIFN-alpha-2C) by pretesting in vitro. From five normal controls and 14 CML patients in chronic phase, bone marrow samples were taken before treatment and tested for antiproliferative activity by rIFN-alpha-2C, using a microagar culture system for BFU-E, CFU-GM, and CFU-Meg. Light-density nucleated bone marrow cells were stimulated for BFU-E and CFU-Meg colony formation with Alpha medium containing 20% serum obtained from a patient with severe aplastic anaemia. CFU-GM growth was induced with conditioned medium from the cell line GCT. In normal controls BFU-E, CFU-GM and CFU-Meg colony formation was inhibited by rIFN-alpha-2C in a dose-dependent manner. BFU-E proved to be the most sensitive cell lineage (IC50: 65; range: 53-116 U/ml) whereas CFU-GM was about 20 times less sensitive (IC50: 643; range: 480-897 U/ml). The sensitivity of CFU-Meg ranged between these two colony types with 50% growth inhibition at an IFN concentration of 160 (range: 68-246 U/ml). A heterogeneous response to rIFN-alpha-2C in vitro was seen in CML patients. Three of the 14 patients were 'resistant' to rIFN-alpha-2C in vitro with IC50 values for BFU-E, CFU-GM and/or CFU-Meg colony formation greater than 10(4) U/ml. Patients were subsequently treated with a daily dose of rIFN-alpha-2C of 5 x 10(6) U. Four patients achieved a complete and six achieved a partial haematological response. Of the four non-responders three rapidly progressed into blastic crisis. Thus it was seen that treatment failure to interferon was accompanied by IFN-resistance in vitro of BFU-E, CFU-GM and/or CFU-Meg colony formation by bone marrow precursors (p less than 0.01). These results suggest a predictive value of IFN-sensitivity testing in vitro in Ph1 + CML.

Sequential therapy with recombinant interferons gamma and alpha in patients with unfavorable prognosis of chronic myelocytic leukemia: clinical responsiveness to recombinant IFN-alpha correlates with the degree of receptor down-regulation

Natural and recombinant interferons (IFNs) have already demonstrated therapeutic efficacy, including cytogenetic remissions, in patients with chronic myelocytic leukemia (CML). We investigated at the level of ligand-receptor interaction the question whether heterogeneity of receptor number or affinity might contribute to primary or secondary treatment failures in CML. We therefore analyzed IFN-gamma and IFN-alpha receptor expression and regulation during treatment with recombinant IFN-gamma and IFN-alpha in 15 patients with advanced CML. We found no difference in number or affinity of constitutively expressed IFN-gamma receptors (mean 1,100) and, on average, a 30% reduction of IFN-alpha receptors (mean 750) on peripheral blood mononuclear cells (PBMNC) of patients with chronic or accelerated CML as compared to mature granulocytes and/or bone marrow cells of healthy controls, which express on average 1,050 and 1,100 IFN-gamma and IFN-alpha receptors, respectively. While IFN-gamma receptor expression on PBMNC is not influenced upon treatment with rIFN-gamma, there is a substantial downregulation of IFN-alpha receptors in the course of rIFN-alpha therapy. Our data also show a differential pattern of receptor downregulation between patients achieving complete hematologic remission (CHR) (4 out of 12) compared with patients with partial hematologic remission (PHR) and non-responders. We conclude that differences in IFN receptor number cannot explain primary or secondary treatment failures. However, the differential ligand induced downregulation of IFN-alpha receptors in patients achieving CHR compared to those with PHR or non-responders suggest a prospective value of IFN-alpha receptor determination.