Freeze-dried platelets are a promising alternative in bleeding thrombocytopenic patients with hematological malignancies

Thrombosomes are trehalose-stabilized, freeze-dried group O platelets with a 3-year shelf life. They can be stockpiled, rapidly reconstituted, and infused regardless of the recipient's blood type. Thrombosomes thus represent a potential alternative platelet transfusion strategy. The present study assessed the safety and potential early signals of efficacy of Thrombosomes in bleeding thrombocytopenic patients. We performed an open-label, phase 1 study of single doses of allogeneic Thrombosomes at three dose levels in three cohorts, each consisting of eight patients who had hematologic malignancies, thrombocytopenia, and bleeding. Adverse events, dose-limiting toxicities (DLTs), World Health Organization (WHO) bleeding scores, and hematology values were assessed. No DLTs were reported. The median age was 59 years (24-71). Most patients had AML (58%) or ALL (29%), followed by MDS (8%) and myeloproliferative neoplasm (4%). The WHO scores of 22 patients who were actively bleeding at a total of 27 sites at baseline either improved (n = 17 [63%]) or stabilized (n = 10 [37%]) through day 6. Twenty-four hours after infusion, 12 patients (50%) had a clinically significant platelet count increase. Of eight patients who received no platelet transfusions for 6 days after Thrombosomes infusion, 5 had a clinically significant increase in platelet count of ≥5000 platelets/μL and 2 had platelet count normalization. Thrombosomes doses up to 3.78 × 10⁸ particles/kg demonstrated safety in 24 bleeding, thrombocytopenic patients with hematological malignancies. Thrombosomes may represent an alternative to conventional platelets to treat bleeding. A phase 2 clinical trial in a similar patient population is underway.

Safety evaluation of a lyophilized platelet-derived hemostatic product

BACKGROUND

Hemorrhage causes significant morbidity and mortality in people aged <65 years. A lyophilized platelet-derived hemostatic agent (Thrombosomes) demonstrated hemostatic efficacy in animal models. We report the results of the first safety trial of autologous Thrombosomes given to normal subjects.

STUDY DESIGN AND METHODS

Ten subjects received autologous Thrombosomes prepared from their apheresis platelets, and five control subjects received a buffer solution. There were five cohorts, with three subjects per cohort (two in the Thrombosomes group and one in the control group). Doses escalated from 1/1,000 to 1/10 of a proposed efficacious dose. Cohorts 4 and 5 received the highest dose, but in Cohort 5, one-half the dose was infused 2 hours apart. Cohorts 1 through 3 were monitored for 42 days, Cohorts 4 and 5 were monitored for 60 days using hematology, coagulation, and chemistry assays and antibody testing.

RESULTS

There were no serious adverse events (AEs) and no subject withdrawals. There were eight treatment-related AEs (TRAEs) in 5 of 15 subjects (33%) (four in the Thrombosomes group and one in the control group). Of four subjects receiving the highest doses, three had TRAEs. One had elevated D-dimer, prothrombin fragment 1 + 2, and white blood cell count (subject had concurrent upper respiratory tract infection); one had T-wave inversions in precordial leads V2 and V3 without elevated troponin or symptoms; and one had a platelet autoantibody without change in platelet count. All subjects' TRAEs resolved by Day 21.

CONCLUSION

There were no serious AEs in this small study. Thrombosomes were considered safe at the doses assessed. Future, larger trials will be needed to further assess safety and efficacy.

Slow internal protein dynamics in solution

Large-scale domain dynamics in proteins are found when flexible linkers or hinges connect domains. The related conformational changes are often related to the function of the protein,for example by arranging the active center after substrate binding or allowing transport and release of products. The adaptation of a specific active structure is referred to as ‘induced fit’ and is challenged by models such as ‘conformational sampling’. Newer models about protein unction include some flexibility within the protein structure or even internal dynamics of the protein. As larger domains contribute to the configurational changes, the timescale of the involved motions is slowed down. The role of slow domain dynamics is being increasingly recognized as essential to understanding the function of proteins. Neutron spin echospectroscopy (NSE) is a technique that is able to access the related timescales from 0.1 up to several hundred nanoseconds and simultaneously covers the length scale relevant for protein domain movements of several nanometers distance between domains. Here we focus on these large-scale domain fluctuations and show how the structure and dynamics of proteins can be assessed by small-angle neutron scattering and NSE.

Bending elastic properties of a block copolymer-rich lamellar phase doped by a surfactant: a neutron spin-echo study

The influence of the short alkyl-chain ionic surfactant OTAB on the dynamic behavior of an inverse block copolymer-rich lamellar phase was investigated by neutron spin-echo spectroscopy (NSE). The observed intermediate scattering function can be described by a sum of two contributions. For high scattering vectors the model of Zilman-Granek plus a slow diffusional mode can be used to describe the experimental data and the bending elastic modulus κ for a polymer-rich membrane is calculated. At low scattering vectors the relaxation curves are strongly influenced by de Gennes narrowing arising from the structure factor of the Lα phase. Hence, the computed relaxation rates in this q-range are inversely proportional to the static structure factor. The present study demonstrates the necessity to directly investigate the dynamic behavior of lamellar phases and that an analysis of the width of the Bragg peaks can be insufficient to derive information about the single membrane elasticity, especially when both κ and B[combining macron] depend on the composition of the membrane.

Fast microscopic method for large scale determination of structure, morphology, and quality of thin colloidal crystals

We present a novel fast microscopic method to analyze the crystal structures of air-dried or suspended colloidal multilayer systems. Once typical lattice spacings of such films are in the range of visible light, characteristic Bragg scattering patterns are observed. If in microscopic observations these are excluded from image construction, a unique color coding for regions of different structures, morphologies, and layer numbers results. Incoherently scattering defect structures, however, may not be excluded from image construction and thus remain visible with high resolution.

Transfusion to blood group A and O patients of group B RBCs that have been enzymatically converted to group O

BACKGROUND

The transfusion of ABO-incompatible RBCs is the leading cause of fatal transfusion reactions. Group O RBCs, lacking terminal immunodominant A and B sugars to which humans are immunized, are safe for transfusion to persons of any ABO blood group. With the use of a recombinant alpha-galactosidase to remove terminal galactose from group B RBCs, the safety and efficacy of enzyme-converted group-B-to-group-O (ECO) RBC components were studied in transfusion-dependent patients.

STUDY DESIGN AND METHODS

Twenty-four patients (blood groups A and O) were randomly assigned to receive transfusion(s) of either ECO or control group O RBCs. If a second transfusion was given, the other blood component was administered.

RESULTS

Twenty-one patients were given ECO RBCs; 18 also underwent control transfusions. One patient received only a small aliquot for RBC survival studies, instead of a full-unit transfusion, because his serum was incompatible with ECO RBCs. No adverse events occurred. Both ECO and control transfusions resulted in appropriate Hb increments and comparable (51)Cr-labeled RBC survival studies. One patient developed a transient, weak-positive DAT, without hemolysis. Two weeks after transfusion, 5 of 19 evaluable ECO RBC recipients had increases in anti-B titers.

CONCLUSION

ECO RBCs were comparable to group O cells for safety and efficacy in this study. The clinical significance of the increase in anti-B and of occasional serologic incompatibilities with ECO RBCs is unclear. If strategies can be developed to remove A epitopes, enzymatic conversion could be used to create a universal (group O) donor blood supply.