Steven Arkin

Recombinant Factor VIII for the Treatment of Previously Untreated Patients with Hemophilia A -- Safety, Efficacy, and Development of Inhibitors

BACKGROUND Although methods of viral attenuation in plasma-derived clotting-factor concentrates have improved, there is still a possibility that such concentrates may transmit certain blood-borne viruses. For this reason, the use of recombinant DNA-derived factor VIII (which is virus-free) to treat hemophilia A has generated considerable interest. METHODS We conducted a multicenter trial in previously untreated children with hemophilia A. They received recombinant factor VIII for all treatment or for prophylaxis and were evaluated at their respective clinics at intervals of no more than three months. RESULTS Between January 1, 1989, and July 1, 1992, 95 patients who could be evaluated received recombinant factor VIII. By September 1, 1992, they had received the concentrate exclusively for 2.4 months to 3.5 years (median, 1.5 years). All responded well, with no treatment failures. A total of 3315 infusions were administered; there were three reports of minor adverse reactions. Inhibitor antibodies to factor VIII developed in 16 of 81 patients tested for them, after a median of nine days of exposure to factor VIII treatment. Inhibitor titers were or became low in 9 of the 16 patients despite continued episodic treatment with the concentrate. Inhibitors disappeared completely in 4 patients and remained at a low level (< 10 Bethesda units) in 5 patients receiving episodic treatment. CONCLUSIONS Transient or low levels of inhibitor, as observed in this study, may represent part of the natural history of hemophilia in infants. In view of the transient nature and lower concentration of the inhibitors detected and the generally satisfactory response to treatment, the benefits of recombinant factor VIII for the treatment of hemophilia seem to outweigh the risks.

Human Recombinant DNA–Derived Antihemophilic Factor (Factor VIII) in the Treatment of Hemophilia A

BACKGROUND Current treatment of hemophilia A, a hereditary disorder affecting approximately 1 in 10,000 males, relies on plasma-derived factor VIII concentrates. We tested the safety and efficacy of a recombinant factor VIII preparation for the treatment of this disorder. METHODS We conducted the investigation in three stages: comparing the pharmacokinetics of plasma-derived and recombinant factor VIII, assessing the efficacy of recombinant factor VIII for home therapy, and assessing its efficacy for major surgical procedures and hemorrhage. A total of 107 subjects with hemophilia, 20 of whom had not been treated previously, enrolled in the investigation. RESULTS The in vivo recovery and elimination half-lives of recombinant factor VIII equaled or exceeded those of plasma-derived factor VIII. Seventy-six subjects participated in a home-treatment program, using recombinant factor VIII for 69 to 807 days (median, 618); home diaries of 56 subjects treated for 5 months were analyzed. Of 540 bleeding episodes, 399 (73.9 percent) required only one treatment with recombinant factor VIII. The projected annual consumption of recombinant factor VIII was similar to that of plasma-derived factor VIII concentrate. Twenty-six subjects received recombinant factor VIII for 22 surgical procedures and 10 serious hemorrhages; hemostasis was excellent in all cases. De novo formation of inhibitors occurred in only 1 of 85 previously treated subjects. Inhibitor antibodies also developed in 6 of 21 children, 20 of whom had not previously been treated; 5 had low levels (less than or equal to 7.5 Bethesda units) despite continued treatment with recombinant factor VIII. There was no evidence of new formation of antibody to foreign proteins, and recombinant factor VIII was well tolerated. CONCLUSIONS Recombinant factor VIII has biologic activity comparable to that of plasma factor VIII and is safe and efficacious for the treatment of hemophilia A.

Hepatitis C Virus Load Is Associated with Human Immunodeficiency Virus Type 1 Disease Progression in Hemophiliacs

Hepatitis C virus (HCV) and human immunodeficiency virus type 1 (HIV-1) coinfection is common in hemophiliacs and injection drug users. To assess the interaction between HCV load and HIV-1 disease progression, we examined 207 HIV-1/HCV-coinfected patients. Patients were followed prospectively for approximately 7 years, and annual measurements of CD4(+) cell counts and HCV and HIV-1 loads were obtained. Survival analysis was used to define the independent effects of HCV load on HIV-1 progression. After controlling for CD4(+) cell count and HIV-1 RNA level, every 10-fold increase in baseline HCV RNA was associated with a relative risk (RR) for clinical progression to acquired immunodeficiency syndrome (AIDS) of 1.66 (95% confidence interval [CI], 1.10-2.51; P=.016) and an RR for AIDS-related mortality of 1.54 (95% CI, 1.03-2.30; P=.036). These findings emphasize the need for further research regarding the use of HIV-1- and HCV-specific therapy in coinfected individuals.

Clinical evaluation of moroctocog alfa (AF-CC), a new generation of B-domain deleted recombinant factor VIII (BDDrFVIII) for treatment of haemophilia A: demonstration of safety, efficacy, and pharmacokinetic equivalence to full-length recombinant factor VIII

Summary.  BDDrFVIII is a B‐domain deleted recombinant factor VIII (rFVIII) product for haemophilia A. Manufacture uniquely includes purification chromatography by synthetic‐affinity ligand rather than murine‐based monoclonal antibody, as well as an albumin‐free cell culture process. BDDrFVIII was studied in 204 patients, including 62 subjects <16 years old, in two studies. A double‐blind, randomized, pharmacokinetic (PK) crossover study, utilizing a central laboratory assay (one‐stage (OS)) for both drug potency assignment and plasma FVIII‐activity measurements, demonstrated that BDDrFVIII was PK‐equivalent to a full‐length rFVIII. Favourable efficacy and safety were observed: during defined routine prophylaxis in a patient population significant for preexisting target joints, nearly half (45.7%) of patients had no bleeding, and a low‐annualized bleed rate (ABR) was achieved (median 1.9); 92.5% of haemorrhages (n = 187) required ≤2 infusions. Three subjects (1.5%, across both studies) developed de novo inhibitors (low‐titre, transient), and the primary safety endpoint, based on a prospective Bayesian analysis, demonstrated the absence of neoantigenicity for BDDrFVIII. The PK‐equivalence, based on central testing to align test and reference articles, and the novel Bayesian analysis of inhibitor safety in these investigations reflect robust experimental designs with relevance to future studies. This extensive dataset demonstrates the safety and efficacy of BDDrFVIII for haemophilia A.

An intrinsic progenitor defect in Diamond‐Blackfan anaemia

Summary. To determine whether the erythropoietin (epo) insensitivity of erythroid progenitor differentiation in congenital pure red cell aplasia or Diamond‐Blackfan anaemia is intrinsic to the progenitor itself or is due to defective accessory cell function or active suppression, progenitors from normals and two patients (one steroid resistant and one spontaneously remitting), separated from all known accessory cells using sequential negative selection techniques (adherence, E‐rosetting, and direct and indirect immune‐panning), were studied. Initially, we evaluated three patients with DBA using unfractionated bone marrow mononuclear cells. Progenitors from two steroid non‐responsive patients showed insensitivity to crude epo (c‐epo) while one steroid responsive patient demonstrated normal in vitro sensitivity to c‐epo. When recombinant epo (r‐epo) was used in place of c‐epo, the two steroid non‐responders continued to demonstrate in vitro progenitor epo insensitivity. However, sensitivity of progenitors from the steroid responder, which was normal in the presence of c‐epo, became abnormal when recombinant epo (r‐epo) was substituted. Thus, using unfractionated bone marrow, the abnormal response to epo of progenitors from some patients with DBA appears to be obscured by stimulating factors termed erythroid burst‐promoting activity (BPA) which are present in c‐epo. Using fractionated highly enriched progenitors, from normals and a steroid responsive patient a final 3–10‐fold enrichment of progenitors was achieved, but no such enrichment was seen when marrow from a steroid resistant patient was cultured. The epo sensitivities of normal and of patient erythroid progenitors were similar. However, at sub‐optimal epo concentrations in both patients CFU‐E responsiveness to crude BPA was abnormal compared to the three controls. We conclude from these studies that in DBA: (a) the failure of erythropoiesis is due to an intrinsic progenitor defect; (b) this defect involves progenitor insensitivity to factors in addition to erythropoietin; and (c) there exists a spectrum of disease reflected in the degree of the in vitro abnormality observed.

DNA Damage is the Triggering Event for Apoptosis in Fanconi Anemia (FA) ♦ 748

FA is an autosomal recessive disorder associated with chromosomal instability, pancytopenia and risk of neoplasia. De novo and in the presence of DNA alkylating agents, FA cells have increased chromosome breaks, prolonged G2/M phase of the cell cycle and increased apoptosis relative to normal. Studies were performed to determine if FA cells have an intrinsically increased rate of apoptosis or whether the observed apoptosis is an appropriate cellular response following unrepaired DNA damage. FA and non-FA fibroblast cell lines exposed to varying concentrations of nitrogen mustard[NM] were studied using flow cytometry. At each [NM] the percent of cells in G2/M arrest and the percent of apoptotic cells was quantitated and threshold[NM] for increased cell cycle arrest and apoptosis were correlated. For Lesch-Nyhan and normal cells the threshold [NM] triggering increased G2/M arrest were 0.125 or 0.25 μg/ml respectively. Accumulation of apoptotic cells did not occur until these thresholds were met or exceeded. In FA cell lines the threshold [NM] triggering increased G2/M arrest and apoptosis was reduced (0.005-0.0125 μg/ml). As with non-FA cells, accumulation of apoptotic FA cells did not occur until the threshold [NM] for increased G2/M arrest was met or exceeded. These data (table) indicate that, in all cell lines tested, DNA damage, as detected using G2/M arrest as a surrogate marker, is the primary insult and that apoptosis is a cellular response to DNA damage. We conclude that the increased apoptosis detected in FA cells is an appropriate cellular response to unrepaired DNA damage rather than a primary pathophysiologic process.