Lactoferrin is another macromolecule that is being considered in the context of COVID-19. It is an iron-binding, multifunctional globular glycoprotein that is widely present in secretory biological fluids, particularly milk [294]. Lactoferrin exhibits a broad-spectrum antimicrobial activity against bacterial, viral, and fungal infections. It also appears to exhibit a clinically relevant activity against some forms of cancer [295], cystic fibrosis [296], and necrotizing enterocolitis [297]. Literature indicates that lactoferrin exhibits activity against a wide range of RNA and DNA viruses, including cytomegalovirus, herpes simplex viruses, HIV, HCV, poliovirus, hantaviruses, rotaviruses, human respiratory syncytial virus, and others [298,299]. Importantly, lactoferrin also appears to exhibit activity against SARS-CoV. It was shown that lactoferrin prevented SARS-CoV from entering human cultured cells. Lactoferrin appeared to block the interaction between the viral spike S protein and heparan sulfate proteoglycans, which serve as an anchoring site on the host cell surface during the early phase of virus infections [300]. Lactoferrin was also found to support the growth of the gut flora as well as the enterocytes proliferation with direct anti-inflammatory/immunomodulatory effects [301]. Currently, lactoferrin is being tested in few clinical trials for COVID-19, including liposomal lactoferrin in COVID-19 patients with mild-to-moderate disease as well as in asymptomatic COVID-19 patients (NCT04475120; n = 60).