Drug-induced thrombocytopenia: Focus on platelet apoptosis

Romiplostim in chemotherapy-induced thrombocytopenia: A review of the literature

Chemotherapy-induced thrombocytopenia (CIT) is a common challenge of cancer therapy and can lead to chemotherapy dose reduction, delay, and/or discontinuation, affecting relative dose intensity, and possibly adversely impacting cancer care. Besides changing anticancer regimens, standard management of CIT has been limited to platelet transfusions and supportive care. Use of the thrombopoietin receptor agonist romiplostim, already approved for use in immune thrombocytopenia, has shown promising signs of efficacy in CIT. In a phase 2 prospective randomized study of solid tumor patients with platelet counts <100 × 109/L for ≥4 weeks due to CIT, weekly romiplostim corrected the platelet count to >100 × 109/L in 93% (14/15) of patients within 3 weeks versus 12.5% (1/8) of untreated patients (p < 0.001). Including patients treated with romiplostim in an additional single-arm cohort, 85% (44/52) of all romiplostim-treated patients responded with platelet count correction within 3 weeks. Several retrospective studies of CIT have also shown responses to weekly romiplostim, with the largest study finding that poor response to romiplostim was predicted by tumor invasion of the bone marrow (odds ratio, 0.029; 95% CI: 0.0046-0.18; p < 0.001), prior pelvic irradiation (odds ratio, 0.078; 95% CI: 0.0062-0.98; p = 0.048), and prior temozolomide treatment (odds ratio 0.24; 95% CI: 0.061-0.96; p = 0.043). Elsewhere, lower baseline TPO levels were predictive of romiplostim response (p = 0.036). No new safety signals have emerged from romiplostim CIT studies. Recent treatment guidelines, including those from the National Comprehensive Cancer Network, now support consideration of romiplostim use in CIT. Data are expected from two ongoing phase 3 romiplostim CIT trials.

A case study of a patient with platelet transfusion refractoriness (PTR) combined with human leucocyte antigen (HLA) antibody positivity during hepatic arterial infusion chemotherapy in conjunction with the 'atezolizumab plus bevacizumab' regimen

Hepatic arterial infusion chemotherapy in conjunction with the combination therapy of atezolizumab (T) and bevacizumab (A) is widely used in hepatocellular carcinoma. Some adverse events such as hypertension, weakness and elevated transaminase levels occurred during treatment, while there is currently no reported case about thrombocytopenia with concomitant HLA antibody-positive PTR. We summarize the critical care nursing experience of a patient with PTR because of HLA antibody positivity during hepatic arterial infusion chemotherapy in conjunction with atezolizumab plus bevacizumab (T + A) regimen. This paper explains the nursing measures for patients with severe thrombocytopenia and proposes nursing measures for situations where conventional treatments are ineffective. Key nursing points include the administration of intravenous immunoglobulin (IVIG) and HLA-compatible platelets, prevention of complications, psychological care, oral care, and skin management. Through systematic treatment and targeted nursing care, the patient's platelet count rebounded after 9 days, leading to a successful recovery and discharge. Subsequent follow-up assessments revealed the patient's sustained well-being. Thrombocytopenia is a potential adverse reaction during the treatment of liver cancer. When platelet transfusion is ineffective, vigilance is necessary for the possibility of HLA positivity, and prompt symptomatic management is warranted.

Physiological platelet aggregation assay to mitigate drug-induced thrombocytopenia using a microphysiological system

Developing a reliable method to predict thrombocytopenia is imperative in drug discovery. Here, we establish an assay using a microphysiological system (MPS) to recapitulate the in-vivo mechanisms of platelet aggregation and adhesion. This assay highlights the role of shear stress on platelet aggregation and their interactions with vascular endothelial cells. Platelet aggregation induced by soluble collagen was detected under agitated, but not static, conditions using a plate shaker and gravity-driven flow using MPS. Notably, aggregates adhered on vascular endothelial cells under gravity-driven flow in the MPS, and this incident increased in a concentration-dependent manner. Upon comparing the soluble collagen-induced aggregation activity in platelet-rich plasma (PRP) and whole blood, remarkable platelet aggregate formation was observed at concentrations of 30 µg/mL and 3 µg/mL in PRP and whole blood, respectively. Moreover, ODN2395, an oligonucleotide, induced platelet aggregation and adhesion to vascular endothelial cells. SYK inhibition, which mediated thrombogenic activity via glycoprotein VI on platelets, ameliorated platelet aggregation in the system, demonstrating that the mechanism of platelet aggregation was induced by soluble collagen and oligonucleotide. Our evaluation system partially recapitulated the aggregation mechanisms in blood vessels and can contribute to the discovery of safe drugs to mitigate the risk of thrombocytopenia.

Alantolactone induces platelet apoptosis by activating the Akt pathway

Alantolactone (ALT), a sesquiterpene lactone compound isolated from Inula helenium L., has recently attracted much attention for its anti-tumor properties. ALT reportedly functions by regulating the Akt pathway, which has been shown to be involved in programmed platelet death (apoptosis) and platelet activation. However, the precise effect of ALT on platelets remains unclear. In this study, washed platelets were treated with ALT in vitro, and apoptotic events and platelet activation were detected. In vivo, platelet transfusion experiments were employed to detect the effect of ALT on platelet clearance. Platelet counts were examined after intravenous injection of ALT. We found that ALT treatment induced Akt activation and Akt-mediated apoptosis in platelets. ALT-activated Akt elicited platelet apoptosis by activating phosphodiesterase (PDE3A) and PDE3A-mediated protein kinase A (PKA) inhibition. Pharmacological inhibition of the PI3K/Akt/PDE3A signaling pathway or PKA activation was found to protect platelets from apoptosis induced by ALT. Moreover, ALT-induced apoptotic platelets were removed faster in vivo, and ALT injection resulted in the platelet count decline. Either PI3K/Akt/PDE3A inhibitors or a PKA activator could protect platelets from clearance, ultimately ameliorating the ALT-induced decline in platelet count in the animal model. These results reveal the effects of ALT on platelets and their related mechanisms, suggesting potential therapeutic targets for the prevention and alleviation of possible side effects resulting from ALT treatments.

Drug-Induced Thrombocytopenia Due to Nintedanib during Treatment of Idiopathic Pulmonary Fibrosis

Nintedanib is a tyrosine kinase inhibitor that was approved for the treatment of patients with idiopathic pulmonary fibrosis in 2014. The most common side effect of Nintedanib is diarrhea, and thrombocytopenia is a rare side effect of Nintedanib. The exact mechanism is unknown, and the literature lacks case reports of this phenomenon. Here, we report the case of a patient who developed thrombocytopenia 12 weeks after starting treatment with Nintedanib. The patient underwent an extensive work up for infectious, hematological, autoimmune, and neoplastic diseases. The patient's thrombocytopenia resolved following cessation of Nintedanib. This case is significant as it reports a rare side effect that might have detrimental consequences if not recognized and treated timely. Additionally, the onset of thrombocytopenia was delayed, 3 months after the initiation of Nintedanib. We also highlight the various literature regarding drug-induced thrombocytopenia and explore the necessary work-up needed to exclude other potential diagnoses. We hope to advocate for multidisciplinary teams to be aware of patients with pulmonary fibrosis on Nintedanib so that this adverse effect can be recognized promptly.

The mechanism of thrombocytopenia caused by cholesterol-conjugated antisense oligonucleotides

In this study, we investigated thrombocytopenia caused by cholesterol-conjugated antisense oligonucleotides (Chol-ASO). First, we evaluated platelet activation induced by Chol-ASO in mice by flow cytometry after administration of platelet-rich plasma (PRP). An increase in the number of large particle-size events with platelet activation was detected in the Chol-ASO-treated group. In a smear study, numerous platelets were observed to attach to nucleic acid-containing aggregates. A competition binding assay showed that the conjugation of cholesterol to ASOs increased their affinity for glycoprotein VI. Platelet-free plasma was then mixed with Chol-ASO to form aggregates. The assembly of Chol-ASO was confirmed by dynamic light scattering measurements in the concentration range in which the formation of aggregates with plasma components was observed. In conclusion, the mechanism by which Chol-ASOs causes thrombocytopenia is proposed to be as follows: (1) Chol-ASOs form polymers, (2) the nucleic acid portion of the polymers interacts with plasma proteins and platelets, which cross-links them to form aggregates, and (3) platelets bound to aggregates become activated, resulting in platelet aggregation, leading to a decrease in platelet count in vivo. The details of the mechanism revealed in this study could contribute to creating safer oligonucleotide therapies without the risk of thrombocytopenia.

Apoptosis in platelets is independent of the actin cytoskeleton

Homeostasis between platelet production and clearance is essential for human health. A critical facet of the balance that facilitates platelet clearance from the circulation is apoptosis (programmed cell death). The precise cellular mechanisms that underpin platelet apoptosis are not defined. In nucleated cells, reorganization of the actin cytoskeleton is known to regulate platelet apoptosis. However, the role of the actin cytoskeleton in regulating apoptosis in platelets has not been extensively studied as they are anucleate and exhibit a distinctive physiology. Here, apoptosis was induced in washed human platelets using ABT-737, a BH3-mimetic drug. Mitochondrial depolarization was measured using the ratiometric dye JC-1; surface phosphatidylserine (PS) exposure was measured by annexin V binding; caspase-3 activation was measured by Western blotting. All three apoptotic markers were unaffected by the presence of either the actin depolymerizing drug cytochalasin D or the actin polymerizing drug jasplakinolide. Moreover, platelets were isolated from wild-type (WT) mice and mice deficient in gelsolin (Gsn), an actin-binding protein that is essential for normal cytoskeletal remodeling. In response to ABT-737, gelsolin-null (Gsn^-/-) platelets initially showed accelerated PS exposure relative to WT platelets, however, both WT and Gsn^-/- platelets exhibited similar levels of mitochondrial depolarization and caspase-3 activation in response to ABT-737. We conclude that ABT-737 induces established markers of platelet apoptosis in an actin-independent manner.

Association of Platelet Desialylation and Circulating Follicular Helper T Cells in Patients With Thrombocytopenia

Thrombocytopenia is a multifactorial condition that frequently involves concomitant defects in platelet production and clearance. The physiopathology of low platelet count in thrombocytopenia remains unclear. Sialylation on platelet membrane glycoprotein and follicular helper T cells (TFHs) are thought to be the novel platelet clearance pathways. The aim of this study was to clarify the roles of platelet desialylation and circulating TFHs in patients with immune thrombocytopenia (ITP) and non-ITP thrombocytopenia. We enrolled 190 patients with ITP and 94 patients with non-ITP related thrombocytopenia including case of aplastic anemia (AA) and myelodysplastic syndromes (MDS). One hundred and ten healthy volunteers were included as controls. We found significantly increased desialylated platelets in patients with ITP or thrombocytopenia in the context of AA and MDS. Platelet desialylation was negatively correlated with platelet count. Meanwhile, the circulating TFH levels in patients with thrombocytopenia were significantly higher than those of normal controls, and were positively correlated with desialylated platelet levels. Moreover, TFHs-related chemokine CXCL13 and apoptotic platelet levels were abnormally high in ITP patients. The upregulation of pro-apoptotic proteins and the activation of the MAPK/mTOR pathway were observed in the same cohort. These findings suggested that platelet desialylation and circulating TFHs may become the potential biomarkers for evaluating the disease process associated with thrombocytopenia in patients with ITP and non-ITP.

Effect of avatrombopag in the management of severe and refractory chemotherapy-induced thrombocytopenia (CIT) in patients with solid tumors

Chemotherapy-induced thrombocytopenia (CIT) is a common complication in cancer patients, especially after multiple cycles of chemotherapy, which leads to the delayed treatment or reduced dosage. The treatment of CIT is limited for refractory and severe cases. Herein we reported a single-center study of avatrombopag, a type of thrombopoietin receptor agonist (TPO-RA), for the treatment of severe and refractory (S/R) CIT who failed from multi-line treatments. A total of 13 cancer patients with S/R CIT were enrolled at the First Affiliated Hospital of Zhejiang Chinese Medical University from September 2020 to February 2021. All the patients were administered oral avatrombopag at an initial dose of 60 mg/day, which could be decreased as needed, over a period of 8 weeks. Eight (8/13, 61.5%) patients responded to avatrombopag (with a platelet count ≥50 × 10⁹/L and transfusion independent), with a median response time of 27.5 (11-50) days, and the median cumulative day of platelet response was 79 (20-167). Ten of 13 patients (76.9%) no longer required platelet transfusion at the study endpoint. The predictor of response was the level of hemoglobin (HB) at study entry, patients with an HB over 90 g/L achieved a response rate of 88.9%. In addition, platelet count showed 87.5% sensitivity and 100% specificity to predict the treatment response at a cutoff value of 25.5× 10⁹/L at the end of the third week management. No drug-related side effects were noticed during administration. Our study showed that avatrombopag could be a novel and effective drug for the treatment of severe and refractory CIT, especially for those with hemoglobin above 90 g/L. This study was registered at chictr.org.cn as # ChiCTR2100050646.

A Comparison of Coagulation Function in Patients Receiving Aspirin and Cefoperazone-Sulbactam With and Without Vitamin K1: A Retrospective, Observational Study

PURPOSE

The study objective was to explore whether prophylaxis with vitamin K₁ improves abnormal coagulation function-associated cefoperazone-sulbactam in patients treated in the long term with low-dose aspirin.

METHODS

This retrospective, observational study assessed patients treated with long-term low-dose aspirin in a naval military hospital in China from 2004 to 2018, including all patients treated concurrently with cefoperazone-sulbactam with or without vitamin K₁. Differences in the coagulation index were analyzed statistically before and after receipt of cefoperazone-sulbactam.

FINDINGS

The cohort included 227 patients. After cefoperazone-sulbactam treatment, the mean (SD) prothrombin time (PT) was 14.07 (3.07) seconds, activated partial thromboplastin time (aPTT) was 35.15 (4.78) seconds, and international normalized ratio (INR) was 1.49 (0.49) in the cefoperazone-sulbactam group, which was significantly higher than the PT of 11.55 (1.29), aPTT of 31.37 (2.20), and INR of 1.12 (0.35) before cefoperazone-sulbactam treatment. No significant difference was in the cefoperazone-sulbactam plus vitamin K₁ group. In addition, no significant difference was found in the thrombin time or fibrinogen level between before and after cefoperazone-sulbactam treatment in both groups. The mean (SD) platelet counts of the 2 groups were 197.34 (71.82) × 10⁹/L and 187.75 (72.66) × 1 0⁹/L after cefoperazone-sulbactam treatment, respectively, which was significantly lower than 231.77 (77.05) × 10⁹/L and 232.08 (84.48) × 10⁹/L before cefoperazone-sulbactam treatment. There were greater proportions of coagulation disorders (prolongation of PT, aPTT, INR, and bleeding) after cefoperazone-sulbactam treatment in the cefoperazone-sulbactam group compared with that in the cefoperazone-sulbactam plus vitamin K₁ group.

IMPLICATIONS

Results indicate that, after adding cefoperazone-sulbactam to the regimens of patients receiving long-term low-dose aspirin, therapy contributed to remarkable increase in abnormal coagulation function and coagulation disorders. Prophylaxis with vitamin K₁ decreased the risk of these abnormalities in blood coagulation parameters associated with cefoperazone-sulbactam in patients taking long-term aspirin.

Mechanisms involved in the development of thrombocytopenia in patients with COVID-19

Corona Virus Disease 2019 (COVID-19) is caused by the novel coronavirus SARS-CoV-2. Emerging genetic and clinical evidence suggests similarities between COVID-19 patients and those with severe acute respiratory syndrome and Middle East respiratory syndrome. Hematological changes such as lymphopenia and thrombocytopenia are not rare in COVID-19 patients, and a smaller population of these patients had leukopenia. Thrombocytopenia was detected in 5–41.7% of the patients with COVID-19. Analyzing the dynamic decrease in platelet counts may be useful in the prognosis of patients with COVID-19. However, the mechanisms underlying the development of thrombocytopenia remain to be elucidated. This review summarizes the hematological changes in patients infected with SARS-CoV-2 and possible underlying mechanisms of thrombocytopenia development.

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Early diagnosis and treatment of COVID-19 patients can reduce mortality.

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There is no laboratory test index to predict disease progression and prognosis.

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Progressive decline in platelets may be a prognostic factor for COVID-19 patients.

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Monitoring platelet count may be an effective index for COVID-19 progression.

Acquired Glanzmann thrombasthenia: From antibodies to anti-platelet drugs

In contrast to the inherited platelet disorder given by mutations in the ITGA2B and ITGB3 genes, mucocutaneous bleeding from a spontaneous inhibition of normally expressed αIIbβ3 characterizes acquired Glanzmann thrombasthenia (GT). Classically, it is associated with autoantibodies or paraproteins that block platelet aggregation without causing a fall in platelet count. However, inhibitory antibodies to αIIbβ3 are widely associated with primary immune thrombocytopenia (ITP), occur in secondary ITP associated with leukemia and related disorders, solid cancers and myeloma, other autoimmune diseases, following organ transplantation while cytoplasmic dysregulation of αIIbβ3 function features in myeloproliferative and myelodysplastic syndromes. Antibodies to αIIbβ3 occur during viral and bacterial infections, while drug-dependent antibodies reacting with αIIbβ3 are a special case. Direct induction of acquired GT is a feature of therapies that block platelets in coronary artery disease. This review looks at these conditions, emphasizing molecular mechanisms, therapy, patient management and future directions for research.