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Cilastatin: a potential treatment strategy against COVID-19 that may decrease viral replication and protect from the cytokine storm

Acute kidney injury (AKI) is a frequent secondary feature in coronavirus disease 2019 (COVID-19) patients [1]. AKI may re-quire renal replacement therapy, complicates management and is associated with impaired outcomes. The absence of current drug treatments for COVID-19 and associated AKI renders patients dependent on supportive intensive care, and therefore new therapeutic approaches are urgently needed [1]. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) entry into human host cells requires endocytosis mecha-nisms activated by binding of SARS-CoV-2 spike protein (S) to angiotensin-converting enzyme 2 (ACE2) on the cell surface Thus, blockade of this binding step is a potential therapeutic approach. in (DHP-I) which to of

Acute kidney injury (AKI) is a frequent secondary feature in coronavirus disease 2019 (COVID-19) patients [1]. AKI may require renal replacement therapy, complicates management and is associated with impaired outcomes. The absence of current drug treatments for COVID-19 and associated AKI renders patients dependent on supportive intensive care, and therefore new therapeutic approaches are urgently needed [1].
Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) entry into human host cells requires endocytosis mechanisms activated by binding of SARS-CoV-2 spike protein (S) to angiotensin-converting enzyme 2 (ACE2) on the cell surface [2]. Thus, blockade of this binding step is a potential therapeutic approach.
ACE2 is located in cholesterol rafts. Cilastatin is a specific competitive blocker of renal dehydropeptidase I (DHP-I) enzyme, which is anchored to cholesterol rafts of renal tubular cells. Cilastatin protects both in vitro and in vivo against tubular cell injury and AKI induced by nephrotoxic drugs such as cyclosporine, vancomycin or cisplatin [3]. The mechanism of this wideranging protection entails blockade of cholesterol raft internalization by the cilastatin/DHP-I complex and decreased membrane turnover. As a result, nephrotoxic compound uptake is decreased. Furthermore, cilastatin blocks signalling by death receptors present in cholesterol rafts, such Fas, whose expression is increased during kidney injury, including bacterial lipopolysaccharide (LPS)-induced AKI and lung injury [4]. The cilastatin/DHP-I complex prevents internalization, trimerization and signalling through the Fas/Fas ligand complex [3]. Consequently, programmed cell death is prevented, and thus the amplifying inflammatory and oxidative wave of cell damage [3,5]. Kidney protection by cilastatin is also observed in rodent models of septic shock [6]. DHP-I is also expressed in lung alveolar epithelial cells. We have now observed for the first time that cilastatin blocks efficiently the development of histological lung injury associated with LPS-induced respiratory distress, decreasing inflammatory cell infiltration ( Figure 1). Both severe sepsis and COVID-19 may be complicated by respiratory distress and AKI, which are associated with higher mortality [7]. In this regard, the cytokine storm elicited by LPS may mimic the cytokine storm of severe COVID-19.
Cilastatin is a fully developed parenteral drug that is clinically safe and currently approved for human use as a fixed combination with imipenem. Generic imipenem/cilastatin is already available. A dose-escalating Phase I clinical trial to evaluate the safety of higher doses of cilastatin than those authorized in the data sheet was completed in 2018 (NCT03595189). During the study, there were no clinically relevant alterations in the physical examination, vital signs and electrocardiogram recordings; minimal changes observed in haematological and biochemistry parameters had neither clinical relevance nor relationship with the study drug; there were no abnormalities detected in the Holter records performed during the study and there were no local tolerance warnings during the continuous administration of the drug.  Based on the preclinical evidence of kidney and lung protection in the context of endotoxemia as presented in this letter, we propose that cilastatin should be studied in clinical trials as a potential therapy for COVID-19. The current understanding of the drug mechanism of action suggests that it may both decrease viral entry and consequently viral replication, and additionally may protect from the deleterious consequences of the cytokine storm observed in severe COVID-19 ( Figure 2). Indeed, a clinical trial of the Fas ligand trap asunercept is planned (https://www.pharmiweb.com/ press-release/2020-07-28/apogenix-to-start-european-clinicalphase-ii-trial-with-asunercept-in-covid-19-patients).

FUNDING
The results of the cilastatin basic research were supported by Spanish grants from the Ministry of Economy and Competitiveness ISCIII-FIS (PI11/01132, PI14/01195 and PI17/00276 cofinanced by FEDER Funds from the European Commission, 'A way of making Europe'), ISCIII-RETIC REDinREN/RD16/0009/0026, Comunidad de Madrid S2017-BMD-3686 (CIFRA2-CM) and Fundació n Senefro (nephrology research grant SENEFRO 18/01). The data that support the findings presented in this letter are available from the corresponding author upon reasonable request. The Renal Physiopathology Laboratory dedicates this work to the memory of its founder, Dr Alberto Tejedor, inventor of cilastatin as a kidney protector, who died as a result of the dramatic effects of COVID-19.