Expanding applications of allogeneic platelets, platelet lysates, and platelet extracellular vesicles in cell therapy, regenerative medicine, and targeted drug delivery.

Platelets are small anucleated blood cells primarily known for their vital hemostatic role. Allogeneic platelet concentrates (PCs) collected from healthy donors are an essential cellular product transfused by hospitals to control or prevent bleeding in patients affected by thrombocytopenia or platelet dysfunctions. Platelets fulfill additional essential functions in innate and adaptive immunity and inflammation, as well as in wound-healing and tissue-repair mechanisms. Platelets contain mitochondria, lysosomes, dense granules, and alpha-granules, which collectively are a remarkable reservoir of multiple trophic factors, enzymes, and signaling molecules. In addition, platelets are prone to release in the blood circulation a unique set of extracellular vesicles (p-EVs), which carry a rich biomolecular cargo influential in cell-cell communications. The exceptional functional roles played by platelets and p-EVs explain the recent interest in exploring the use of allogeneic PCs as source material to develop new biotherapies that could address needs in cell therapy, regenerative medicine, and targeted drug delivery. Pooled human platelet lysates (HPLs) can be produced from allogeneic PCs that have reached their expiration date and are no longer suitable for transfusion but remain valuable source materials for other applications. These HPLs can substitute for fetal bovine serum as a clinical grade xeno-free supplement of growth media used in the in vitro expansion of human cells for transplantation purposes. The use of expired allogeneic platelet concentrates has opened the way for small-pool or large-pool allogeneic HPLs and HPL-derived p-EVs as biotherapy for ocular surface disorders, wound care and, potentially, neurodegenerative diseases, osteoarthritis, and others. Additionally, allogeneic platelets are now seen as a readily available source of cells and EVs that can be exploited for targeted drug delivery vehicles. This article aims to offer an in-depth update on emerging translational applications of allogeneic platelet biotherapies while also highlighting their advantages and limitations as a clinical modality in regenerative medicine and cell therapies.

Platelet extracellular vesicles are efficient delivery vehicles of doxorubicin, an anti-cancer drug: preparation and in vitro characterization.

Platelet extracellular vesicles (PEVs) are an emerging delivery vehi for anticancer drugs due to their ability to target and remain in the tumor microenvironment. However, there is still a lack of understanding regarding yields, safety, drug loading efficiencies, and efficacy of PEVs. In this study, various methods were compared to generate PEVs from clinical-grade platelets, and their properties were examined as vehicles for doxorubicin (DOX). Sonication and extrusion produced the most PEVs, with means of 496 and 493 PEVs per platelet (PLT), respectively, compared to 145 and 33 by freeze/thaw and incubation, respectively. The PEVs were loaded with DOX through incubation and purified by chromatography. The size and concentration of the PEVs and PEV-DOX were analyzed using dynamic light scattering and nanoparticle tracking analysis. The results showed that the population sizes and concentrations of PEVs and PEV-DOX were in the ranges of 120-150 nm and 1.2-6.2 × 1011 particles/mL for all preparations. The loading of DOX determined using fluorospectrometry was found to be 2.1 × 106, 1.7 × 106, and 0.9 × 106 molecules/EV using freeze/thaw, extrusion, and sonication, respectively. The internalization of PEVs was determined to occur through clathrin-mediated endocytosis. PEV-DOX were more efficiently taken up by MDA-MB-231 breast cancer cells compared to MCF7/ADR breast cancer cells and NIH/3T3 cells. DOX-PEVs showed higher anticancer activity against MDA-MB-231 cells than against MCF7/ADR or NIH/3T3 cells and better than acommercial liposomal DOX formulation. In conclusion, this study demonstrates that PEVs generated by PLTs using extrusion, freeze/thaw, or sonication can efficiently load DOX and kill breast cancer cells, providing a promising strategy for further evaluation in preclinical animal models. The study findings suggest that sonication and extrusion are the most efficient methods to generate PEVs and that PEVs loaded with DOX exhibit significant anticancer activity against MDA-MB-231 breast cancer cells.

What is the context?● Current synthetic drug delivery systems can have limitations and side effects.● Platelet extracellular vesicles (PEVs) are a natural and potentially safer alternative for delivering cancer drugs to tumors.● However, there is still a lack of understanding about how to produce PEVs and how effective they are in delivering drugs.What is new?● We compared different methods for producing PEVs from clinical-grade platelets and found that sonication and extrusion were the most effective methods.● The PEVs were loaded with a cancer drug called doxorubicin (DOX) and tested their ability to kill breast cancer cells.What is the impact?● PEVs loaded with DOX were effective at killing cancer cells, especially MDA-MB-231 breast cancer cells.● This study demonstrates that PEVs are a promising strategy for delivering cancer drugs to tumors and that sonication and extrusion are the most efficient methods for producing PEVs.● The results suggest that further evaluation of PEVs in preclinical animal models is warranted to determine their potential as a cancer drug delivery system.Abbreviations: ADP: adenosine diphosphate; bFGF: basic fibroblast growth factor; BSA: bovine serum albumin; CD41: platelet glycoprotein IIb; CD62P: P-selectin; CFDASE: 5-(and-6)-carboxyfluorescein diacetate: succinimidyl ester; CPLT: cryopreserved platelet; CPZ: chlorpromazine hydrochloride; CTC: circulating tumor cell; DMSO: dimethyl sulfoxide; DDS: drug delivery system; DOX: doxorubicin; EPR: enhanced permeability and retention; EV: extracellular vesicle; FBS: fetal bovine serum; GMP: good manufacturing practice; GF: growth factor; HER2: human epidermal growth factor receptor 2; HGF: hepatocyte growth factor; Lipo-DOX: liposomal doxorubicin; MDR: multi-drug resistance; MMP-2: matrix metalloproteinase-2; MP: microparticle; MSC: mesenchymal stromal cell; NP: nanoparticle; NTA: nanoparticle tracking analysis; PAR-1: protease activated receptor-1; PAS: platelet additive solution; PBS: phosphate-buffered saline; PC: platelet concentrate; PEG: polyethylene glycol; PEV: platelet-derived extracellular vesicle; DOX-PEV: doxorubicin-loaded platelet-derived extracellular vesicle-encapsulated; PFA: paraformaldehyde; PF4: platelet factor 4; P-gp: P-glycoprotein; PLT: platelet; PS: phosphatidylserine; SDS-PAGE: sodium dodecylsulfate polyacrylamide gel electrophoresis; SEM: scanning electron microscopy; TCIPA: tumor cell-induced PLT aggregation; TDDS: targeted drug delivery system; TEG: thromboelastography; TF: tissue factor; TF-EV: extracellular vesicle expressing tissue factor; TME: tumor microenvironment; TNBC: triple-negative breast cancer; TXA2: thromboxane-A2; VEGF: vascular endothelial growth factor; WHO: World Health Organization.

Hematological toxicities of immune checkpoint inhibitors and the impact of blood transfusion and its microbiome on therapeutic efficacy and recipient's safety and survival outcome:A systematic narrative appraisal of where we are now!

Classically, patients with solid and hematologic malignancies have been treated with a combination of chemotherapy with or without a holistic targeted strategy using approved conventional therapy. While the evidence-based use of Immunomodulatory drugs and Immune checkpoint inhibitors (ICIs), including those targeting the PD-1, PD-L1 and CTLA-4, have reshaped the treatment paradigm for many malignant tumors and significantly stretched the life expectancy of patients, as for any interventional therapy, the rise in ICI applications, was associated with the observation of more immune-related hematological adverse events. Many of these patients require transfusion support during their treatment in line with precision transfusion. It has been presumed that transfusion-related immunomodulation (TRIM) and the microbiome can pose immunosuppressive effects on the recipients. Looking to the past and beyond and translating available data into practice in the evolving role of pharmaceutical therapy to ICI-receiving patients, we performed a narrative review of the literature on the immune-related hematological adverse events of ICIs, immunosuppressive mechanisms linked to blood product transfusions, as well as the detrimental impact of transfusions and its related microbiome on the sustained efficacy of ICIs and the patients' survival outcomes. Recent reports are pointing to the negative impact of transfusion on ICI response. Studies have concluded that packed RBC [PRBC] transfusions lead to an inferior progression-free and overall survival in patients with advanced cancer receiving ICIs, even after adjustments for other prognostic variables. The attenuation of the effectiveness of immunotherapy likely results from the immunosuppressive effects of PRBC transfusions. It is, therefore, wise to look retrospectively and prospectively at the impact of transfusion on ICI effects and adopt, in the interim, a restrictive transfusion strategy, if applicable, for those patients.

Blood transfusion in autoimmune rheumatic diseases.

Autoimmune rheumatic disorders (ARD) represent a wide spectrum of disorders that affect in priority the joints, bones, muscles, and connective tissues. Examples of ARD include rheumatoid arthritis, systemic lupus erythematosus, Sjögren syndrome, polymyositis, systemic sclerosis, antiphospholipid syndrome and mixed connective tissue disease. Patients with ARD often require transfusion of red cell concentrates (RCC) or other blood-derived components. The presence of an autoimmune background, often complicated by the use of immunosuppressive medications, renders these patients quite vulnerable. Exposing them to RCC, when indicated, can trigger transfusion-related immunomodulation that can be aggravated by the role played by the donor microbiome, and the complement activation and the immune dysregulation induced by iron, leading to an amplification of the immune problems. Furthermore, patients are challenged by the transfused extracellular vesicles which could have a potentially negative role, particularly in patients with antiphospholipid syndrome. Despite the very vigorous screening, transfusion transmissible infections can still represent a risk to these patients, particularly in cytomegalovirus seronegative patients or when dormant pathogens are activated in the immunosuppressed transfusion recipient. The ARD population is also more at risk for transfusion-related reactions. One, therefore, has to consider a restrictive transfusion strategy if possible and, if needed, resort to the numerous blood bank procedures to reduce the immunogenicity of blood products or use safer, more targeted, industrial plasma-derived products subjected to purification and pathogen reduction technologies.

Platelet and extracellular vesicles in COVID-19 infection and its vaccines.

Platelets are at the crossroads between thrombosis and inflammation. When activated, platelets can shed bioactive extracellular vesicles [pEVs] that share the hemostatic potential of their parent cells and act as bioactive shuttles of their granular contents. In a viral infection, platelets are activated, and pEVs are generated with occasional virion integration. Both platelets and pEVs are engaged in a bidirectional interaction with neutrophils and other cells of the immune system and the hemostatic pathways. Severe COVID-19 infection is characterized by a stormy thromboinflammatory response with platelets and their EVs at the center stage of this reaction. This review sheds light on the interactions of platelets, pEVS and SARS-CoV-2 infection and prognostic and potential therapeutic role of pEVs. The review also describes the role of pEVs in the rare adenovirus-based COVID-19 vaccine-induced thrombosis thrombocytopenia.

SARS-CoV-2 and cancer: the intriguing and informative cross-talk.

The COVID-19 pandemic caused by the SARS-CoV-2 virus has significantly disrupted and burdened the diagnostic workup and delivery of care, including transfusion, to cancer patients across the globe. Furthermore, cancer patients suffering from solid tumors or hematologic malignancies were more prone to the infection and had higher morbidity and mortality than the rest of the population. Major signaling pathways have been identified at the intersection of SARS-CoV-2 and cancer cells, often leading to tumor progression or alteration of the tumor response to therapy. The reactivation of oncogenic viruses has also been alluded to in the context and following COVID-19. Paradoxically, certain tumors responded better following the profound infection-induced immune modulation. Unveiling the mechanisms of the virus-tumor cell interactions will lead to a better understanding of the pathophysiology of both cancer progression and virus propagation. It would be challenging to monitor, through the different cancer registries, retrospectively, the response of patients who have been previously exposed to the virus in contrast to those who have not contracted the infection.

No apparent association between mRNA COVID-19 vaccination and venous thromboembolism.

By January 2022 over ten billion doses of COVID-19 vaccines had been administered worldwide. Concerns about COVID-19 vaccine-associated thrombosis arose after the characterization of a rare prothrombotic condition associated with adenoviral vector-based COVID-19 vaccines known as vaccine-induced immune thrombotic thrombocytopenia (VITT). Although mRNA COVID-19 vaccines have not been linked to VITT, concerns about thrombosis after vaccination persist despite safety data from hundreds of millions of recipients of mRNA COVID-19 vaccines. With widespread vaccination some VTE will occur shortly after vaccination by chance alone because VTE is a common condition that affects 1 to 2 in 1000 persons each year. Detailed analysis is required to determine whether these VTE events are coincidental or associated when they occur in close proximity to mRNA vaccine administration. This paper will review what is currently known about rates of VTE after mRNA vaccination in adults, discuss the reasons why uncertainty on this topic persists, and briefly review the implications of these findings for clinical practice and health policy.

Metabolism-mediated thrombotic microangiopathy and B12.

Thrombotic microangiopathies (TMAs) are a group of life-threatening conditions requiring urgent management and characterized by a clinical triad of microangiopathic hemolytic anemia, thrombocytopenia, and ischemic tissue injury. Severe vitamin B12 (Cobalamin-Cbl) deficiency or defective cobalamin metabolism, particularly defects in intracellular B12 metabolism, may lead to a TMA-like picture. The latter has been termed metabolism-mediated TMA (MM-TMA). This confusing picture is mediated partly by ineffective erythropoiesis with significant red cell fragmentation resulting in a hemolytic pattern, coupled with reduced platelet production and endothelial injury with organ damage resulting from accumulated toxic byproducts of B12 dysmetabolism. However, unlike in classic thrombotic thrombocytopenic purpura, where therapeutic plasma exchange has to be initiated promptly, cases of MM-TMA can be treated, if diagnosed properly, with adequate B12 replacement.

Regenerative effect of expired platelet concentrates in human therapy: An update.

There is concrete evidence that outdated allogeneic platelet concentrates not used for transfusion are valuable sources of functional trophic factors, including growth factors, cytokines, chemokines, anti-inflammatory and antioxidant molecules. Such outdated platelet concentrates can be used to produce human platelet lysates (HPL), a proven potent growth supplement for the propagation of therapeutic human cells, including mesenchymal stromal cells. On-going preclinical studies demonstrate the interest in such "outdated" allogeneic platelet lysates for treating corneal diseases and neurological disorders of the central nervous system, potentially opening vital therapeutic perspectives.

Prospective Therapeutic Applications of Platelet Extracellular Vesicles.

There is much interest in the use of extracellular vesicles (EVs) as a subcellular therapy for regenerative medicine and drug delivery. Blood-borne platelets represent a source of therapeutic EVs that is so far largely unexplored. Advantages of platelets as a cellular source of EVs include their established clinical value, regulated collection procedures, availability in a concentrated form, propensity to generate EVs, and unique composition and tissue-targeting capacity. This review analyzes the unique potential of platelet-derived (p-) EVs as therapeutic modalities and presents their inherent translational advantages for hemostasis, for regenerative medicine, and as drug-delivery vehicles.

Clinical-grade cryopreserved doxorubicin-loaded platelets: role of cancer cells and platelet extracellular vesicles activation loop.

BACKGROUND: Human platelets (PLT) and PLT-extracellular vesicles (PEV) released upon thrombin activation express receptors that interact with tumour cells and, thus, can serve as a delivery platform of anti-cancer agents. Drug-loaded nanoparticles coated with PLT membranes were demonstrated to have improved targeting efficiency to tumours, but remain impractical for clinical translation. PLT and PEV targeted drug delivery vehicles should facilitate clinical developments if clinical-grade procedures can be developed. METHODS: PLT from therapeutic-grade PLT concentrate (PC; N > 50) were loaded with doxorubicin (DOX) and stored at - 80 °C (DOX-loaded PLT) with 6% dimethyl sulfoxide (cryopreserved DOX-loaded PLT). Surface markers and function of cryopreserved DOX-loaded PLT was confirmed by Western blot and thromboelastography, respectively. The morphology of fresh and cryopreserved naïve and DOX-loaded PLT was observed by scanning electron microscopy. The content of tissue factor-expressing cancer-derived extracellular vesicles (TF-EV) present in conditioned medium (CM) of breast cancer cells cultures was measured. The drug release by fresh and cryopreserved DOX-loaded PLT triggered by various pH and CM was determined by high performance liquid chromatography. The thrombin activated PEV was analyzed by nanoparticle tracking analysis. The cellular uptake of DOX from PLT was observed by deconvolution microscopy. The cytotoxicities of DOX-loaded PLT, cryopreserved DOX-loaded PLT, DOX and liposomal DOX on breast, lung and colon cancer cells were analyzed by CCK-8 assay. RESULTS: 15~36 × 106 molecules of DOX could be loaded in each PLT within 3 to 9 days after collection. The characterization and bioreactivity of cryopreserved DOX-loaded PLT were preserved, as evidenced by (a) microscopic observations, (b) preservation of important PLT membrane markers CD41, CD61, protease activated receptor-1, (c) functional activity, (d) reactivity to TF-EV, and (e) efficient generation of PEV upon thrombin activation. The transfer of DOX from cryopreserved PLT to cancer cells was achieved within 90 min, and stimulated by TF-EV and low pH. The cryopreserved DOX-loaded PLT formulation was 7~23-times more toxic to three cancer cells than liposomal DOX. CONCLUSIONS: Cryopreserved DOX-loaded PLT can be prepared under clinically compliant conditions preserving the membrane functionality for anti-cancer therapy. These findings open perspectives for translational applications of PLT-based drug delivery systems.

Vitamin B12 deficiency and metabolism-mediated thrombotic microangiopathy (MM-TMA).

Thrombotic microangiopathies (TMA) are characterized by microangiopathic hemolytic anemia, thrombocytopenia and organ damage resulting from mechanical factors, accumulation of the ultra-large von Willebrand factor multimers or complement-mediated abnormalities. Severe acquired vitamin B12 (Cobalamin - Cbl) deficiency or congenital defective Cbl metabolism could lead to a picture that mimics TMA. The later has been termed metabolism-mediated TMA (MM- TMA). This confusing picture is mediated partly by the large red cell fragmentation coupled with reduced platelet production in the absence of vitamin B12 and partly by the accumulated byproducts and metabolites that induce endothelial injury and hence organ damage. Expensive and complicated treatment for TMA is often initiated on an empiric basis, pending the results of confirmatory tests. In contrast, vitamin B12 Pseudo-TMA and MM-TMA could be treated with proper vitamin B12 supplementation. It is therefore important to identify these disorders promptly. The recent availability of a validated scoring system such as the PLASMIC score uses simple clinical and laboratory parameters. As it incorporates the mean corpuscular volume in its laboratory parameters, this helps in the identification of pseudo and MM-TMA. Perhaps some minor modification of this scoring system by changing the parameters of hemolysis to include reticulocytosis and rather than and/or other hemolytic parameters could even help refine this identification.

Plasma fractionation in countries with limited infrastructure and low-/medium income: How to move forward?

Although therapeutic drivers are changing over the years, and innovative biotech products are continuously modifying the clinical landscape, there is an increasing need for plasma protein therapies obtained by the fractionation of human plasma. Plasma-derived protein products therefore continue to play vital roles in the therapeutic management of various immunological disorders, deficiencies in coagulation factors or protease inhibitors, viral or bacterial infections, and trauma. Plasma fractionation is a biotechnology industry that has increased in complexity over the last 30 years to ensure that plasma-derived protein therapies exhibit optimal quality and pathogen safety profiles. Plasma-derived products are among the safest biological therapies available; in industrialized countries they are strictly and efficiently regulated in all aspects of their production chain and clinical use. Conversely, due to some technological complexities and strict adherence to regulatory requirements, a substantial barrier to entry into the field of plasma fractionation exists. Although various plasma-derived protein products are on the WHO model list of essential medicines, dramatic shortages of these products exist, especially in low-/medium income countries, while at the same time more than 9 million liters of recovered plasma in these countries are wasted annually. Lack of plasma protein products results mainly from three factors: (a) cost of imported products, (b) insufficient local supply of quality plasma for fractionation, or (c) lack of domestic industrial fractionation capacity. As the understanding of critical quality and safety factors has dramatically improved over the years, there is a need to rethink how affordable, scalable, and reliable purification and virus inactivation technologies could be introduced in countries with poor relevant infrastructures and low-/medium income. Such technologies, when properly validated and implemented, could help ensure local availability of essential plasma protein therapies and gradually fill the gap in product supply, safety and affordability that exists relative to advanced economies.

Viral safety of human platelet lysate for cell therapy and regenerative medicine: Moving forward, yes, but without forgetting the past.

Growth factor-rich pooled human platelet lysate (HPL), made from human platelet concentrates, is one new blood-derived bioproduct that is attracting justified interest as a xeno-free supplement of growth media for human cell propagation for cell therapy. HPL can also find potentially relevant applications in the field of regenerative medicine. Therefore, the therapeutic applications of HPL go far beyond the standard clinical applications of the traditional blood products typically used in patients suffering from life-threatening congenital or acquired deficiencies in cellular components or proteins due to severe genetic diseases or trauma. A wider population of patients, suffering from various pathologies than has traditionally been the case, is thus, now susceptible to receiving a human blood-derived product. These patients would, therefore, be exposed to the possible, but avoidable, side effects of blood products, including transfusion-transmitted infections, most specifically virus transmissions. Unfortunately, not all manufacturers, suppliers, and users of HPL may have a strong background in the blood product industry. As such, they may not be fully aware of the various building blocks that should contribute to the viral safety of HPL as is already the case for any licensed blood products. The purpose of this manuscript is to reemphasize all the measures, including in regulatory aspects, capable of assuring that HPL exhibits a sufficient pathogen safety margin, especially when made from large pools of human platelet concentrates. It is vital to remember the past to avoid that the mistakes, which happened 30 to 40 years ago and led to the contamination of many blood recipients, be repeated due to negligence or ignorance of the facts.

Transplant-associated thrombotic microangiopathy: Diagnostic challenges and management strategies.

Transplant-associated thrombotic microangiopathy (TA-TMA) is one of the early endothelial complications post Hematopoietic Stem Cell Transplant (HSCT). Several mechanisms during HSCT can contribute to systemic capillary endothelial damage which can lead to TA-TMA among other complications as capillary leak syndrome or engraftment syndrome. Early diagnosis of TA-TMA contributes a challenge due to overlapping clinical manifestations and the absence of specific diagnostic criteria. Incidence is greatly variable between 1-76% according to risk factors of patients and the definition used to confirm the diagnosis. The mortality rates in patients who develop severe TA-TMA are in excess of 80%. Early treatment improves the outcome. This review outlines the diagnostic challenges and therapeutic options for TA-TMA.

New monoclonal/bi-specific antibodies: Reshaping transfusion medicine beyond replacement.

Since the first successful transfusion in 1818, Transfusion Medicine has evolved significantly. The advent of plasma fractionation and availability of recombinant products allowed for precision replacement therapy to treat many hematological conditions, such as hemophilia, thrombotic thrombocytopenic purpura, and hereditary angioedema. A deeper understanding of the pathophysiology underlying those conditions along with the development of safer monoclonal and bispecific antibodies is now offering safe and effective alternatives to the simple conventional approach of replacing a missing plasma protein. Many biologicals are already in wide clinical use in areas such as rheumatology, gastroenterology, and medical oncology. The introduction of novel therapeutic antibodies within the realm of Transfusion Medicine will likely reshape the field and challenge the role of local blood establishments as the gate-keepers of such therapies.

Flow cytometry and immune thrombocytopenic purpura.

Although Immune thrombocytopenic purpura is a common disorder that family physicians, internists and hematologists face in their everyday practice, its diagnosis rests only on "exclusion" and its therapy is based on algorithms where "trial and error" is the rule. Flow cytometry, if simplified and standardized, could provide a quicker and better diagnostic accuracy. Studies of the lymphocyte subset using flow cytometry and more elaborate immune studies are paving the way for a better understanding of the disease and in identification of prognostic markers. Such studies may even help stratify the first-line therapy responder and assist in the use of the arsenal of immune suppressive therapy with better precision.

Circulatory-cell-mediated nanotherapeutic approaches in disease targeting.

Circulating blood cells, and cell-derived microvesicles, are emerging as pragmatic delivery systems that can smartly complement the already existing nanotherapeutic platforms evaluated to treat or diagnose diseases. The valuable distinctive features of circulatory cells over synthetic nanocarriers encompass their biological origin which confers immune transparence, known biodegradability, high drug loading, relatively long half-life and a targeting capacity associated with their physiological surface functionality. Absence of nuclei in red blood cells and platelets provides further rationale for their use as cargo vehicles for nucleotoxic agents. Ongoing developments in cell-based and cell-inspired nanotherapies can move drug delivery into reachable frontiers and exhibit high potentiality for translatability into clinical use.

A randomized multicenter study: safety and efficacy of mini-pool intravenous immunoglobulin versus standard immunoglobulin in children aged 1-18 years with immune thrombocytopenia.

BACKGROUND: Because there is a global shortage of intravenous immunoglobulin, there is a need for new products to fill the gap. STUDY DESIGN AND METHODS: This was a multicenter, open-label study investigating the safety and efficacy of a newly developed mini-pool intravenous immunoglobulin G for children with immune thrombocytopenia. Seventy-two patients ages 1 to 18 years with newly diagnosed (<1 month) immune thrombocytopenia who had platelet counts from 5 to 20 × 109 /L with no serious bleeding were recruited from four centers in Egypt. Eligible patients were randomized into three groups 1:1:1. Group A (n = 24) received blood group-specific mini-pool intravenous immunoglobulin in a dose equivalent to immunoglobulin 1 g/kg over 6 to 8 hours, Group B (n = 24) received standard intravenous immunoglobulin (approximately 1g/kg) as a single dose, and Group C (n = 24) did not receive any platelet-enhancing therapy. Parents signed informed consent. RESULTS: Of the patients who received mini-pool intravenous immunoglobulin, 14 achieved a complete response (CR) (58.8%), and four had a response (16.6%). Of the patients who received intravenous immunoglobulin G, 16 achieved a complete response (66.6%), and four had a response (16.6%). In Group C, eight patients achieved a complete response (33.3%), and four had a response (16.6%). The median time to response was 8, 9, and 21 days in Group A, B, and C, respectively, which was significantly higher in Group C than Groups A and B (p < 0.001). Patients in Groups A and B reported 16 adverse drug reactions. CONCLUSION: Mini-pool intravenous immunoglobulin G was well tolerated, presented no safety issues, and was effective in the treatment of immune thrombocytopenia, with efficacy comparable to that of the standard intravenous immunoglobulin G group, and it was significantly more effective than no treatment.

Platelet transfusion in thrombocytopenic cancer patients: Sometimes justified but likely insidious.

The transfusion of platelet concentrates prepared from allogeneic single or pooled donations is a standard procedure in transfusion medicine to stop or prevent bleeding in cancer patients with thrombocytopenia undergoing surgery, chemotherapy and/or radiotherapy. While platelet transfusion may appear reasonable in many instances, greater scientific and medical attention should however be given to the possibly insidious impact of transfused platelets on the outcome of cancers. Indeed platelets and the microvesicles they release possess all the biological ingredients capable of supporting tumor growth, protecting circulating tumor cells, and to contributing to metastatic invasion. Until any randomized controlled trials can objectively document their effects on survival or cancer recurrence, minimizing the use of platelet transfusion in cancer patients appears to represent a reasonable precautionary measure.