In vivo genotoxicity assessment of N-(-9 acridinyl)-b-alanine hydrochloride (S-300) using a validated Pig-a mutagenesis assay.

BACKGROUND: N-(-9 acridinyl)-b-alanine hydrochloride (S-300) is the main byproduct of red blood cell (RBC) amustaline/glutathione(GSH) pathogen reduction, currently undergoing phase III US clinical trials following successful European studies(1-3). Phosphatidylinositol glycan, class A (Pig-a) X-linked gene mutagenesis is a validated mammalian in vivo mutation assay for genotoxicity, assessed as clonal loss of glycosylphosphatidylinositol-linked CD59 cell-surface molecules on reticulocytes (RETs) and RBCs. METHODS: Male Sprague-Dawley rats received continuous infusion of S-300 up to the maximum feasible dose (240 mg/kg/day-limited by solubility and volume) for 28 days. Positive controls received a known mutagen by oral gavage on Days 1-3. Plasma levels of S-300 were assessed by HPLC before, during and after infusion. CD59-negative RBCs and RETs were enumerated in pre-dose and Day 28 samples, using a flow cytometric method. Outcome was evaluated by predetermined criteria using concurrent and historical controls. Toxicity was assessed by laboratory measures and necropsy. RESULTS: S-300 reached maximum, dose-dependent levels (3-15 µmol/L) within 2-8 h that were sustained for 672 h and undetectable 2 h after infusion. Circulating RET levels indicated a lack of hematopoietic toxicity. Necropsy revealed minimal-mild observations related to poor S-300 solubility at high concentrations. Pig-a assessment met the preset acceptability criteria and revealed no increase in mutant RBCs or RETs. CONCLUSIONS: Maximum feasible S-300 exposure of rats by continuous infusion for 28 days was not genotoxic as assessed by an Organization for Economic Cooperation and Development-compliant, mammalian, in vivo Pig-a gene mutation assay that meets the requirements of International Conference on Harmonization (ICH) S2(R1) and FDA guidances on genotoxicity testing.

Evaluation of amotosalen and UVA pathogen-reduced apheresis platelets after 7-day storage.

BACKGROUND: Amotosalen/UVA pathogen-reduced platelet components (PRPCs) with storage up to 7 days are standard of care in France, Switzerland, and Austria. PRPCs provide effective hemostasis with reduced risk of transfusion-transmitted infections and transfusion-associated graft versus host disease, reduced wastage and improved availability compared with 5-day-stored PCs. This study evaluated the potency of 7-day PRPCs by in vitro characterization and in vivo pharmacokinetic analysis of autologous PCs. STUDY DESIGN AND METHODS: The in vitro characteristics of 7-day-stored apheresis PRPCs suspended in 100% plasma or 65% platelet additive solution (PAS-3)/35% plasma, thrombin generation, and in vivo radiolabeled post-transfusion recovery and survival of 7-day-stored PRPCs suspended in 100% plasma were compared with either 7-day-stored or fresh autologous conventional platelets. RESULTS: PRPCs after 7 days of storage maintained pH, platelet dose, in vitro physiologic characteristics, and thrombin generation when compared to conventional 7-day PCs. In vivo, the mean post-transfusion survival was 151.4 ± 20.1 h for 7-day PRPCs in 100% plasma (Test) versus 209.6 ± 13.9 h for the fresh autologous platelets (Control), (T-ΔC: 72.3 ± 8.8%: 95% confidence interval [CI]: 68.5, 76.1) and mean 24-h post-transfusion recovery 37.6 ± 8.4% for Test versus 56.8 ± 9.2% for Control (T-ΔC: 66.2 ± 11.2%; 95% CI: 61.3, 71.1). DISCUSSION: PRPCs collected in both 100% plasma as well as 65% PAS-3/35% plasma and stored for 7 days retained in vitro physiologic characteristics. PRPCs stored in 100% plasma for 7 days retained in vivo survival. Lower in vivo post-radiolabeled autologous platelet recovery is consistent with reported reduced count increments for allogenic transfusion.

Preclinical safety assessment of pathogen reduced red blood cells treated with amustaline and glutathione.

BACKGROUND: The nucleic acid targeted pathogen reduction (PR) system utilizing amustaline (S-303) and glutathione (GSH) is designed to inactivate blood-borne pathogens and leukocytes in red blood cell concentrates (PR-RBCC). Inactivation is attained after amustaline intercalates and forms covalent nucleic acid adducts preventing replication, transcription, and translation. After pathogen inactivation, amustaline spontaneously hydrolyzes to S-300, the primary negatively charged reaction product; amustaline is below quantifiable levels in PR-RBCC. GSH quenches free unreacted amustaline. STUDY DESIGN AND METHODS: The genotoxic and carcinogenic potential of PR-RBCC, the reaction by-products, and S-300 were assessed in accordance with the International Conference on Harmonization (ICH) guidelines and performed in compliance with the Food and Drug Administration (FDA) good laboratory practice standards, 21 CFR Part 58. in vitro bacterial reverse mutagenicity and chromosomal aberration assays were performed with and without exogenous S9 metabolic activation, and in in vivo clastogenicity and carcinogenic assays using validated murine models. RESULTS: PR-RBCCs were not genotoxic in vitro and in vivo and were non-carcinogenic in p53+/- transgenic mice transfused over 26 weeks. Estimated safety margins for human exposure ranged from >90 to >36 fold for 2 to 5 PR-RBCCs per day, respectively. PR-RBCCs and S-300 did not induce chromosome aberration in the in vivo murine bone marrow micronucleus assay at systemically toxic doses. CONCLUSIONS: PR-RBCCs did not demonstrate genotoxicity in vitro or in vivo and were not carcinogenic in vivo. These studies support the safety of PR-RBCCs and suggest that there is no measurable genotoxic hazard associated with transfusion of PR-RBCCs.

Prevalence of natural and acquired antibodies to amustaline/glutathione pathogen reduced red blood cells.

BACKGROUND: The INTERCEPT™ Blood System for Red Blood Cells (RBCs) utilizes amustaline (S-303) and glutathione (GSH) to inactivate pathogens and leukocytes in transfused RBCs. Treatment-emergent low titer non-hemolytic antibodies to amustaline/GSH RBC were detected in clinical trials using a prior version of the process. The amustaline/GSH process was re-formulated to decrease S-303 RBC adduct formation. STUDY DESIGN AND METHODS: A standard three-cell antibody screening panel was modified to include reagent red cells (RRC) with high (S-303H) or low (S-303L) S-303 adduct density as assessed by flow cytometry, representative of the original and current amustaline/GSH treatment processes, respectively. General hospital and RBC transfusion-dependent patients never exposed, and clinical trial subjects exposed to amustaline/GSH RBC were screened for antibodies to amustaline/GSH RBC using a standardized agglutination assay. RESULTS: Twelve (0.1%) of 10,721 general hospital and 5 (0.5%) of 998 repeatedly-transfused patients not previously exposed to amustaline/GSH RBCs expressed natural, low titer (2-32) IgM and/or IgG (non-IgG1 or IgG3 isotype) antibodies with acridine (a structural element of amustaline) (n = 14) or non-acridine (n = 3) specificity. 11 of 17 sera reacted with S-303L panel RRCs. In clinical studies 81 thalassemia and 25 cardiac surgery patients were transfused with a total of 1085 amustaline/GSH RBCs and no natural or treatment-emergent S-303 antibodies were detected. CONCLUSION: Standardized RRC screening panels are sensitive for the detection of natural and acquired S-303-specific antibodies. Natural low titer antibodies to amustaline/GSH RBC are present in 0.15% of naïve patients. The clinical relevance of these antibodies appears minimal but is under further investigation.

Amustaline-glutathione pathogen-reduced red blood cell concentrates for transfusion-dependent thalassaemia.

Transfusion-dependent thalassaemia (TDT) requires red blood cell concentrates (RBCC) to prevent complications of anaemia, but carries risk of infection. Pathogen reduction of RBCC offers potential to reduce infectious risk. We evaluated the efficacy and safety of pathogen-reduced (PR) Amustaline-Glutathione (A-GSH) RBCC for TDT. Patients were randomized to a blinded 2-period crossover treatment sequence for six transfusions over 8-10 months with Control and A-GSH-RBCC. The efficacy outcome utilized non-inferiority analysis with 90% power to detect a 15% difference in transfused haemoglobin (Hb), and the safety outcome was the incidence of antibodies to A-GSH-PR-RBCC. By intent to treat (80 patients), 12·5 ± 1·9 RBCC were transfused in each period. Storage durations of A-GSH and C-RBCC were similar (8·9 days). Mean A-GSH-RBCC transfused Hb (g/kg/day) was not inferior to Control (0·113 ± 0·04 vs. 0·111 ± 0·04, P = 0·373, paired t-test). The upper bound of the one-sided 95% confidence interval for the treatment difference from the mixed effects model was 0·005 g/kg/day, within a non-inferiority margin of 0·017 g/kg/day. A-GSH-RBCC mean pre-transfusion Hb levels declined by 6·0 g/l. No antibodies to A-GSH-RBCC were detected, and there were no differences in adverse events. A-GSH-RBCCs offer potential to reduce infectious risk in TDT with a tolerable safety profile.

Red blood cells treated with the amustaline (S-303) pathogen reduction system: a transfusion study in cardiac surgery.

BACKGROUND: Nucleic acid-targeted pathogen inactivation technology using amustaline (S-303) and glutathione (GSH) was developed to reduce the risk of transfusion-transmitted infectious disease and transfusion-associated graft-versus-host disease with red blood cell (RBC) transfusion. STUDY DESIGN AND METHODS: A randomized, double-blind, controlled study was performed to assess the in vitro characteristics of amustaline-treated RBCs (test) compared with conventional (control) RBCs and to evaluate safety and efficacy of transfusion during and after cardiac surgery. The primary device efficacy endpoint was the postproduction hemoglobin (Hb) content of RBCs. Exploratory clinical outcomes included renal and hepatic failure, the 6-minute walk test (a surrogate for cardiopulmonary function), adverse events (AEs), and the immune response to amustaline-treated RBCs. RESULTS: A total of 774 RBC unis were produced. Mean treatment difference in Hb content was -2.27 g/unit (95% confidence interval, -2.61 to -1.92 g/unit), within the prespecified equivalence margins (±5 g/unit) to declare noninferiority. Amustaline-treated RBCs met European guidelines for Hb content, hematocrit, and hemolysis. Fifty-one (25 test and 26 control) patients received study RBCs. There were no significant differences in RBC usage or other clinical outcomes. Observed AEs were within the spectrum expected for patients of similar age undergoing cardiovascular surgery requiring RBCs transfusion. No patients exhibited an immune response specific to amustaline-treated RBCs. CONCLUSION: Amustaline-treated RBCs demonstrated equivalence to control RBCs for Hb content, have appropriate characteristics for transfusion, and were well tolerated when transfused in support of acute anemia. Renal impairment was characterized as a potential efficacy endpoint for pivotal studies of RBC transfusion in cardiac surgery.

Plasma treated with amotosalen and ultraviolet A light retains activity for hemostasis after 5 days post-thaw storage at 1 to 6o C.

BACKGROUND: Plasma thawed and stored at 1 to 6° C for up to 5 days (thawed plasma [TP]) provides rapid availability in emergencies and reduces plasma waste, but it carries risks of coagulation factor loss or activation, bacterial outgrowth, and viral contamination. We characterized changes in amotosalen/ultraviolet A (UVA) light pathogen-reduced, fresh-frozen plasma (FFP) and plasma frozen within 24 hours (PF24) with post-thaw storage. STUDY DESIGN AND METHODS: Amotosalen/UVA light-treated FFP and PF24 were thawed after approximately 3 to more than 12 months of frozen storage and held at 1 to 6° C for 5 days. Global assessments of coagulation and hemostatic, antithrombotic, and activation markers indicative of function were assessed. RESULTS: Day 5, thawed amotosalen/UVA light-treated FFP and PF24 contained levels of Factors II, V, VIII, IX, X, von Willebrand factor ristocetin cofactor (vWF:RCo), fibrinogen, antithrombin III (ATIII), protein C, and protein S similar to the levels measured in Day 5 TP, as described in the Circular of Information. Thrombin generation was robust on Day 5 (amotosalen/UVA: FFP = 1866 ± 402 nM/minute; PF24 = 1800 ± 277 nM/minute). Most factor activities on Day 5, including von Willebrand factor-cleaving protease (ADAMTS-13), were more than 90% of Day 0 values, except for known labile Factors V and VIII and protein S. All units contained greater than 0.4 IU/mL protein S and α2 plasmin inhibitor on Day 5. Global functional indices, including thrombin-antithrombin complexes, nonactivated thromboplastin time, and thrombin-generation peak height, did not indicate activation of the coagulation cascade, although isolated units showed raised levels of Factor VIIa and Complement 3a. CONCLUSION: Amotosalen/UVA light-treated FFP and PF24 demonstrated retention of procoagulant and antithrombotic activity after 5 days post-thaw storage at 1 to 6° C.

Red blood cell in vitro quality and function is maintained after S-303 pathogen inactivation treatment.

BACKGROUND: Over the past decade there has been a growth in the development of pathogen reduction technologies to protect the blood supply from emerging pathogens. This development has proven to be difficult for red blood cells (RBCs). However the S-303 system has been shown to effectively inactivate a broad spectrum of pathogens, while maintaining RBC quality. STUDY DESIGN AND METHODS: A paired three-arm study was performed to compare the in vitro quality of S-303-treated RBCs with RBCs stored at room temperature (RT) for the duration of the treatment (18-20 hr) and control RBCs stored at 2 to 6°C. Products were sampled weekly over 42 days of storage (n = 10) and tested using an array of in vitro assays to measure quality, metabolism, and functional variables. RESULTS: During S-303 treatment there was a slight loss of RBCs and hemoglobin (Hb < 5 g). Hemolysis, glucose consumption, and potassium release were similar in all groups during the 42 days of storage. S-303-treated RBCs had a significantly lower lactate concentration and pH compared to the paired controls. The S-303-treated RBCs had significantly higher adenosine triphosphate than the RT and control RBCs. There was a significant loss of 2,3-diphosphoglycerate in the S-303-treated products, which was also observed in the RT RBCs. Flow cytometry analysis demonstrated similar RBC size, morphology, expression of CD47, and glycophorin A in all groups. CONCLUSION: RBCs treated with S-303 for pathogen reduction had similar in vitro properties to the paired controls and were within transfusion guidelines.

Evaluation of the efficacy and safety of amustaline/glutathione pathogen-reduced RBCs in complex cardiac surgery: the Red Cell Pathogen Inactivation (ReCePI) study-protocol for a phase 3, randomized, controlled trial.

BACKGROUND: Red blood cell (RBC) transfusion is a critical supportive therapy in cardiovascular surgery (CVS). Donor selection and testing have reduced the risk of transfusion-transmitted infections; however, risks remain from bacteria, emerging viruses, pathogens for which testing is not performed and from residual donor leukocytes. Amustaline (S-303)/glutathione (GSH) treatment pathogen reduction technology is designed to inactivate a broad spectrum of infectious agents and leukocytes in RBC concentrates. The ReCePI study is a Phase 3 clinical trial designed to evaluate the efficacy and safety of pathogen-reduced RBCs transfused for acute anemia in CVS compared to conventional RBCs, and to assess the clinical significance of treatment-emergent RBC antibodies. METHODS: ReCePI is a prospective, multicenter, randomized, double-blinded, active-controlled, parallel-design, non-inferiority study. Eligible subjects will be randomized up to 7 days before surgery to receive either leukoreduced Test (pathogen reduced) or Control (conventional) RBCs from surgery up to day 7 post-surgery. The primary efficacy endpoint is the proportion of patients transfused with at least one study transfusion with an acute kidney injury (AKI) diagnosis defined as any increased serum creatinine (sCr) level ≥ 0.3 mg/dL (or 26.5 µmol/L) from pre-surgery baseline within 48 ± 4 h of the end of surgery. The primary safety endpoints are the proportion of patients with any treatment-emergent adverse events (TEAEs) related to study RBC transfusion through 28 days, and the proportion of patients with treatment-emergent antibodies with confirmed specificity to pathogen-reduced RBCs through 75 days after the last study transfusion. With ≥ 292 evaluable, transfused patients (> 146 per arm), the study has 80% power to demonstrate non-inferiority, defined as a Test group AKI incidence increase of no more than 50% of the Control group rate, assuming a Control incidence of 30%. DISCUSSION: RBCs are transfused to prevent tissue hypoxia caused by surgery-induced bleeding and anemia. AKI is a sensitive indicator of renal hypoxia and a novel endpoint for assessing RBC efficacy. The ReCePI study is intended to demonstrate the non-inferiority of pathogen-reduced RBCs to conventional RBCs in the support of renal tissue oxygenation due to acute anemia and to characterize the incidence of treatment-related antibodies to RBCs.

Preclinical pharmacokinetic and toxicology assessment of red blood cells prepared with S-303 pathogen inactivation treatment.

BACKGROUND: A system has been developed to inactivate a wide spectrum of blood-borne pathogens in red blood cells (RBCs) before transfusion. The system utilizes S-303 to target nucleic acids of pathogens and white blood cells. The safety of pathogen inactivated RBC was assessed using S-303-treated RBCs (S-303 RBCs) and S-300, the primary degradation product of S-303. STUDY DESIGN AND METHODS: As part of a preclinical safety evaluation program, intravenous toxicity, safety pharmacology, toxicokinetic, and pharmacokinetic studies were conducted in rats and dogs with S-303 RBCs and S-300. RESULTS: Single and repeated transfusions of S-303 RBCs were well tolerated in rats and dogs at S-303 concentrations up to five times higher than that used to prepare RBCs for clinical use. For S-300, the doses ranged from the lowest level representative of a clinical exposure from transfusion of 1 unit (0.052 mg/kg/day) to up to the amount of S-300 that would result from exposure to more than 1900 units of RBCs (100 mg/kg/day). There were no related effects of S-303 RBCs or S-300 on mortality, clinical status, body weight, or clinical laboratory assessments and no evidence of organ toxicity. S-300 did not accumulate in the plasma of rats and dogs after repeated transfusions. For all the studies, plasma S-303 was consistently below the limit of quantitation. CONCLUSION: The level of residual S-303 and S-300 in the treated blood component is well below that at which no adverse effects were observed. These results support further clinical development of S-303 RBCs for prevention of transfusion-transmitted infections.

Stored red blood cell viability is maintained after treatment with a second-generation S-303 pathogen inactivation process.

BACKGROUND: Transfusion-transmitted infections and immunologic effects of viable residual lymphocytes remain a concern in red blood cell (RBC) transfusion. Pathogen reduction technologies for RBC components are under development to further improve transfusion safety. S-303 is a frangible anchor-linker-effector with labile alkylating activity and a robust pathogen reduction profile. This study characterized the viability of RBCs prepared with a second-generation S-303 process and stored for 35 days. STUDY DESIGN AND METHODS: This was a two-center, single-blind randomized, controlled, crossover study in 27 healthy subjects. S-303 (test) or control RBCs were prepared in random sequence and stored for 35 days, at which time an aliquot of radiolabeled RBCs was transfused. The 24-hour recovery, RBC life span, and in vitro metabolic and viability variables were analyzed. RESULTS: The mean 24-hour RBC recovery and hemolysis of test RBCs were similar to control RBCs and were consistent with the Food and Drug Administration (FDA) guidance for RBC viability. The mean differences in life span and median life span (T(50) ) of circulating test RBCs were 13.7 and 6.8 days, while the mean difference in the area under the curve of surviving RBCs was 1.38%, in favor of control RBCs. There were no clinically relevant abnormal laboratory values after the infusion of test RBCs. All crossmatch assays of autologous S-303 RBCs were nonreactive. CONCLUSIONS: RBCs prepared using the S-303 pathogen inactivation process were physiologically and metabolically suitable for transfusion after 35 days of storage, met the FDA guidance criteria for 24-hour recovery, and did not induce antibody formation.

Development of the S-303 Pathogen Inactivation Technology for Red Blood Cell Concentrates.

Pathogen inactivation systems are in use in many European countries as routine procedures. However, a pathogen inactivation system for erythrocytes is currently not available. Although significant improvements have been made to decrease the incidence of transfusion-transmitted infections, risks remain for infectious disease agents specific to red blood cell concentrates, such as parasitic infections resulting in babesiosis and malaria. The pathogen inactivation system for erythrocytes utilizes S-303 and glutathione for the treatment of red blood cell concentrates. Preclinical studies to assess the pathogen inactivation efficacy and toxicology as well as preliminary clinical studies have been completed. Preclinical studies have shown log reduction for leukocytes, several viruses and bacteria in excess of 4 to 6 logs. Preclinical toxicology studies were conducted to enable the initiation of two phase III clinical studies in the USA for support of acute and chronic anemia. A second-generation system was developed after observation of an unexpected immune response in two chronic anemia patients. Preclinical pathogen inactivation studies, serological evaluations and a clinical study to evaluate survival of S-303-treated erythrocytes have been completed to support advanced development of the S-303 pathogen inactivation system. A functional system for the inactivation of red blood cell concentrates has been completed and is reaching clinical application.