Regadenoson for the treatment of COVID-19: A five case clinical series and mouse studies

Abstract

Background Adenosine inhibits the activation of most immune cells and platelets. Selective adenosine A2A receptor (A2AR) agonists such as regadenoson (RA) reduce inflammation in most tissues, including lungs injured by hypoxia, ischemia, transplantation, or sickle cell anemia, principally by suppressing the activation of invariant natural killer T (iNKT) cells. The anti-inflammatory effects of RA are magnified in injured tissues due to induction in immune cells of A2ARs and ecto-enzymes CD39 and CD73 that convert ATP to adenosine in the extracellular space. Here we describe the results of a five patient study designed to evaluate RA safety and to seek evidence of reduced cytokine storm in hospitalized COVID-19 patients. Methods and findings Five COVID-19 patients requiring supplemental oxygen but not intubation (WHO stages 4–5) were infused IV with a loading RA dose of 5 μg/kg/h for 0.5 h followed by a maintenance dose of 1.44 μg/kg/h for 6 hours, Vital signs and arterial oxygen saturation were recorded, and blood samples were collected before, during and after RA infusion for analysis of CRP, D-dimer, circulating iNKT cell activation state and plasma levels of 13 proinflammatory cytokines. RA was devoid of serious side effects, and within 24 hours from the start of infusion was associated with increased oxygen saturation (93.8 ± 0.58 vs 96.6 ± 1.08%, P<0.05), decreased D-dimer (754 ± 17 vs 518 ± 98 ng/ml, P<0.05), and a trend toward decreased CRP (3.80 ± 1.40 vs 1.98 ± 0.74 mg/dL, P = 0.075). Circulating iNKT cells, but not conventional T cells, were highly activated in COVID-19 patients (65% vs 5% CD69+). RA infusion for 30 minutes reduced iNKT cell activation by 50% (P<0.01). RA infusion for 30 minutes did not influence plasma cytokines, but infusion for 4.5 or 24 hours reduced levels of 11 of 13 proinflammatory cytokines. In separate mouse studies, subcutaneous RA infusion from Alzet minipumps at 1.44 μg/kg/h increased 10-day survival of SARS-CoV-2-infected K18-hACE2 mice from 10 to 40% (P<0.001). Conclusions Infused RA is safe and produces rapid anti-inflammatory effects mediated by A2A adenosine receptors on iNKT cells and possibly in part by A2ARs on other immune cells and platelets. We speculate that iNKT cells are activated by release of injury-induced glycolipid antigens and/or alarmins such as IL-33 derived from virally infected type II epithelial cells which in turn activate iNKT cells and secondarily other immune cells. Adenosine released from hypoxic tissues, or RA infused as an anti-inflammatory agent decrease proinflammatory cytokines and may be useful for treating cytokine storm in patients with Covid-19 or other inflammatory lung diseases or trauma.

Genetic Polymorphisms of P2RX7 but Not of ADORA2A Are Associated with the Severity of SARS-CoV-2 Infection

“…Although the role of A2AR in the severity of SARS-CoV-2 infection has been hypothesized [ 32 , 33 , 34 ] and preliminary clinical data indicate that the infusion of either adenosine or of a selective A2AR agonist may dampen inflammation in COVID-19 patients [ 35 , 36 ], our study did not reveal any association between SARS-CoV-2 infection and the rs2298383 SNP of A2AR, a loss-of-function polymorphism associated with bolstered immune response [ 28 ]. We have previously shown in the context of brain diseases that the altered role of A2AR depends both on the up-regulation of A2AR as well as an increased formation of extracellular adenosine [ 40 , 41 , 42 , 43 ].…”

“…We have previously shown in the context of brain diseases that the altered role of A2AR depends both on the up-regulation of A2AR as well as an increased formation of extracellular adenosine [ 40 , 41 , 42 , 43 ]. Thus, the contrasting evidence that A2AR properties seems unrelated to the severity of COVID-19 whereas exogenously added agonists provide a clinical benefit [ 35 , 36 ] is suggestive that the major modification in the adenosine system associated with COVID-19 might be the availability of extracellular adenosine. Future studies assessing the levels of extracellular adenosine as well as the function of A2AR during infection, or of other SNPs of A2AR [ 27 ], are needed to better understand a possible role of the adenosine A2AR modulation system in SARS-CoV-2 pathophysiology.…”

“…This association of P2X7R and of A2AR with inflammation and infection has prompted multiple opinion papers hypothesizing that the antagonism of P2X7R [ 29 , 30 , 31 , 32 ] or activation of A2AR [ 32 , 33 , 34 ] may afford a benefit to manage COVID-19. However, apart from three reports describing that inhaled adenosine seems beneficial in patients with COVID-19-pneumonia [ 35 ], that an A2AR agonist regadenoson reduces inflammatory burden in 5 COVID-19 patients [ 36 ], that P2X7R controls the replication of the alpha SARS-CoV-2 variants [ 37 ] and that soluble P2X7R is increased in the plasma of COVID-19 patients [ 38 ], there is scarce experimental evidence linking P2X7R or A2AR to the severity of COVID-19.…”

The Purinergic Nature of Pseudoxanthoma Elasticum

“…Moreover, positron emission tomography combined with computed tomographic imaging has shown a positive correlation between calcification and inflammation in the skin and arteries of a 42-year-old PXE patient [159]. At this point in time, the connection between ABCC6 function and IL-6 is not clear, however a recent study could provide some clues [200]. A very recent publication by Casemayo et al showed that Abcc6 deficiency produced an immune modulation with positive effects on the renal manifestations of rhabdomyolysis [158].…”