STAGE-I CLINICAL-TRIAL OF GENE-THERAPY FOR HEMOPHILIA-B

This paper describes the first human gene therapy trial for hemophilia B. Retroviruses were used to introduce human factor IX into autologou s, primary human skin fibroblasts from the patients. Recombinant retro viral vector containing human FIX cDNA driven by viral LTR promoter (X L-IX) and double-copy retroviral vector driven by human cytomegaloviru s enhancer-promoter (N2CMV-IX) were constructed. After the safety asse ssment, including soft-agar test, cell morphology observation, analysi s of endotoxin, chromosome karyotype, allergic reaction test, nude mic e test, routine pathological test, electromicroscopic analysis, and vi rus detection by PCR, etc., the engineered cells were pooled and embed ded in collagen mixture, autologously injected into the patients respe ctively. The concentration of human FIX protein of Patient 1 increased from 71 ng/ml to 220 ng/ml, with a maximum level of 245 ng/ml. The ex pression of FIX has lasted for 6 months at the time of writing. The cl otting activity also increased from 2.9% to 6.3%, his clinical symptom s have been alleviated obviously. The secretion rate of FIX for Patien t 2 increased from 130 to 250 ng/ml, maintained at the level of 220 ng /ml for 5.5 months at the time of writing, but the clotting activity h as not been increased steadily. There is no deleterious effect to be f ound in the two patients since the ex-vivo cells were implanted. The t wo patients are now under follow-up investigation. We suggested that r etrovirus-mediated transfer of genes into skin fibroblasts, to be embe dded in collagen and subcutaneously injected into patients, is a simpl e and effective approach for the gene therapy for hemophilia B.