CXCR4 and COVID-19: As targeting CXCR4 has been subject to intensive studies due to involvement of the chemokine axis in tumor progression (52, 53), suitable radiopharmaceutical conjugates of CXCR4 as well as potent CXCR4 antagonists have been developed and thoroughly described (54, 55) and thus could be easily repurposed to investigate the cytokine signaling pathway in COVID-19 and monitor possible effects of targeted therapy with CXCR4 antagonists by quantifying the regional level of CXCR4 activity over time.