Novel Tissue Factor Inhibition for Thromboprophylaxis in COVID-19: Primary Results of the ASPEN-COVID-19 Trial

Review of COVID-19 Therapeutics by Mechanism: From Discovery to Approval

The global research and pharmaceutical community rapidly mobilized to develop treatments for coronavirus disease 2019 (COVID-19). Existing treatments have been repurposed and new drugs have emerged. Here we summarize mechanisms and clinical trials of COVID-19 therapeutics approved or in development. Two reviewers, working independently, reviewed published data for approved COVID-19 vaccines and drugs, as well as developmental pipelines, using databases from the following organizations: United States Food and Drug Administration (US-FDA), European Medicines Agency (EMA), Japanese Pharmaceutical and Medical Devices Agency (PMDA), and ClinicalTrials.gov. In all, 387 drugs were found for initial review. After removing unrelated trials and drugs, 66 drugs were selected, including 17 approved drugs and 49 drugs under development. These drugs were classified into six categories: 1) drugs targeting the viral life cycle 2) Anti-severe acute respiratory syndrome coronavirus 2 Monoclonal Antibodies, 3) immunomodulators, 4) anti-coagulants, 5) COVID-19-induced neuropathy drugs, and 6) other therapeutics. Among the 49 drugs under development are the following: 6 drugs targeting the viral life cycle, 12 immunosuppression drugs, 2 immunostimulants, 2 HIF-PHD targeting drugs, 3 GM-CSF targeting drugs, 5 anti-coagulants, 2 COVID-19-induced neuropathy drugs, and 17 others. This review provides insight into mechanisms of action, properties, and indications for COVID-19 medications.

Targeting the tissue factor coagulation initiation complex prevents antiphospholipid antibody development

ABSTRACT

Antiphospholipid antibodies (aPL) in primary or secondary antiphospholipid syndrome (APS) are a major cause for acquired thrombophilia, but specific interventions preventing autoimmune aPL development are an unmet clinical need. Although autoimmune aPL cross react with various coagulation regulatory proteins, lipid-reactive aPL, including those derived from patients with COVID-19, recognize the endolysosomal phospholipid lysobisphosphatidic acid presented by the cell surface-expressed endothelial protein C receptor. This specific recognition leads to complement-mediated activation of tissue factor (TF)-dependent proinflammatory signaling and thrombosis. Here, we show that specific inhibition of the TF coagulation initiation complex with nematode anticoagulant protein c2 (NAPc2) prevents the prothrombotic effects of aPL derived from patients with COVID-19 in mice and the aPL-induced proinflammatory and prothrombotic activation of monocytes. The induction of experimental APS is dependent on the nicotinamide adenine dinucleotide phosphate (NADPH) oxidase complex, and NAPc2 suppresses monocyte endosomal reactive oxygen species production requiring the TF cytoplasmic domain and interferon-α secretion from dendritic cells. Latent infection with murine cytomegalovirus causes TF cytoplasmic domain-dependent development of persistent aPL and circulating phospholipid-reactive B1 cells, which is prevented by short-term intervention with NAPc2 during acute viral infection. In addition, treatment of lupus prone MRL-lpr mice with NAPc2, but not with heparin, suppresses dendritic-cell activation in the spleen, aPL production and circulating phospholipid-reactive B1 cells, and attenuates lupus pathology. These data demonstrate a convergent TF-dependent mechanism of aPL development in latent viral infection and autoimmune disease and provide initial evidence that specific targeting of the TF initiation complex has therapeutic benefits beyond currently used clinical anticoagulant strategies.

Tissue Factor and COVID-19 Associated Thrombosis

Microbial infections activate the innate and adaptive immune systems.1 Pathogen-associated molecular patterns produced by microbes, such as double-stranded RNA, are detected by PRRs (pattern-recognition receptors), such as toll-like receptor 3, and this leads to the expression of interferons and cytokines.1,2.

Multisite spontaneous hematomas and bleeding in critically ill Chinese patients with COVID-19: two case reports and a literature review

BACKGROUND

Anticoagulation is recommended as a standardized therapy for COVID-19 patients according to the WHO guidelines. However, bleeding events have also been reported. Hemorrhage or hematoma was observed in sites including the retroperitoneum, brain, alimentary tract, muscles, and soft tissues. Reduction or suspension of anticoagulants is a common intervention. Transfusion, endoscopic hemostasis, and vascular interventional therapy have been used to improve the condition.

CASE PRESENTATION

In this article, we present two cases of concurrent multisite hematomas and bleeding at other sites in patients with SARS-CoV-2 infection. Both patients were treated with heparins and experienced bleeding after the anticoagulation therapy. Both patients were older with more than two comorbidities, and critical COVID-19. Laboratory tests revealed a considerable decrease in hemoglobin levels and alterations in the coagulation system. In the first patient, the main intervention was embolization using angiography. However, we only adjusted the anticoagulation strategy in the second case. The first patient recovered and was discharged; however, the second died of other causes. This study provides a retrospective review of typical hemorrhagic cases during anticoagulation in COVID-19 patients over the course of four years. A relatively comprehensive search was performed in Pubmed by constructing MeSH subject terms on limiting the search period and specific contents. It summarizes and synthesizes the research related to heparins and other novel anticoagulants in the context of COVID-19 from the onset of the pandemic to the present disseminated phase. This study aimed to offer valuable insights and reference points for developing anticoagulation treatment strategies for patients with COVID-19.

CONCLUSIONS

Anticoagulation is a crucial treatment option for patients with COVID-19. The difference in anticoagulant effects is related to the severity of COVID-19. Nafamostat can reduce thrombosis in the extracorporeal circuits in critically ill patients with COVID-19. The efficacy and safety of novel anticoagulants require further clinical data. Routine bedside assessments and real-time laboratory monitoring are essential for early identification of bleeding events during anticoagulant therapy and administering intervention.

Challenges to Laboratory Monitoring of Direct Oral Anticoagulants

Direct oral anticoagulants (DOACs) exert anticoagulation effect by directly inhibiting Factor Xa (rivaroxaban, apixaban, and edoxaban) or thrombin (dabigatran). Though DOACs are characterized by fixed-dose prescribing and generally do not require routine laboratory drug-level monitoring (DLM), circumstances may arise where the DLM may aid in clinical decision-making, including DOAC dose adjustment, anticoagulant class change, or decisions to withhold or administer reversal agents. We review the current literature that describes high-risk patient groups in which DLM may be beneficial for improved patient anticoagulation management and stewardship. The review also summarizes the limitations of conventional coagulation testing and discuss the emerging utility of quantitative methods for routine and rapid emergent evaluation of DOAC drug levels-in particular, the Anti-Xa activity to detect Factor Xa Inhibitors (rivaroxaban, apixaban, and edoxaban). Both technical and regulatory barriers to widespread DLM implementation are limiting factors to further clinical research that must be overcome, in order to propose universal DOAC DLM strategies and provide clinical-laboratory correlation to formally classify high-risk patient groups.