www.nature.com/cdd REVIEW ARTICLE OPEN Repurposing the estrogen receptor modulator raloxifene to treat SARS-CoV-2 infection ✉ Marcello Allegretti 1 , Maria Candida Cesta 1, Mara Zippoli1, Andrea Beccari1, Carmine Talarico1, Flavio Mantelli1, Enrico M. Bucci 2, Laura Scorzolini3 and Emanuele Nicastri3 © The Author(s) 2021 The ongoing coronavirus disease 2019 (COVID-19) pandemic caused by the novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) necessitates strategies to identify prophylactic and therapeutic drug candidates to enter rapid clinical development. This is particularly true, given the uncertainty about the endurance of the immune memory induced by both previous infections or vaccines, and given the fact that the eradication of SARS-CoV-2 might be challenging to reach, given the attack rate of the virus, which would require unusually high protection by a vaccine. Here, we show how raloxifene, a selective estrogen receptor modulator with anti-inflammatory and antiviral properties, emerges as an attractive candidate entering clinical trials to test its efficacy in early-stage treatment COVID-19 patients. Cell Death & Differentiation; https://doi.org/10.1038/s41418-021-00844-6 FACTS (3) If successful, the ongoing clinical study on raloxifene, a well- known SERM, in paucisymptomatic COVID-19 patients could represent a valid opportunity of treatment for controlling (1) Despite the recent advancements in vaccines development, disease progression. it is still essential not to underestimate the risk associated (4) Validation of the running hypothesis would pave the way for with COVID-19 infection, and to advance knowledge on further investigation on ER modulation as therapeutic specific SARS-CoV-2 pharmacological treatments to cure or approach to treat other infectious diseases. mitigate the impact of COVID-19 on patients. (2) Drug repurposing is an attractive approach to address unmet clinical needs in infectivology. (3) The E4C program has shown the potential of powerful INTRODUCTION supercomputing platforms in shortening the timing to the In December 2019, a new identified coronavirus, severe acute identification of potential clinical candidates targeting key viral respiratory syndrome coronavirus 2 (SARS-CoV-2), caused an proteins leading to the selection of an estrogen receptor (ER) outbreak in Wuhan with public health crisis in China and rapid modulator, raloxifene, currently under clinical investigation. spread across the world, causing general concern. On February 11, (4) Literature data suggest a protective role of estrogens in COVID- 2020, the World Health Organization officially named the disease 19 infection, by regulation of cytokines related to immunity “COVID-19”; the Chinese Government took strong and harsh and inflammation, suggesting ER modulation as a promising measures to control the outbreak progression characterized by pharmacological approach for preventing/attenuating the atypical pneumonia cases. Similar measures were also adopted in cytokine storm and inflammation associated to COVID-19. Europe and worldwide. Common symptoms of COVID-19 include fever, sore throat, fatigue, cough, shortness of breath, and dyspnea that may eventually progress toward acute respiratory distress syndrome (ARDS), to the involvement of other systems/ OPEN QUESTIONS organs are also susceptible to COVID-19 (e.g., heart, liver, and kidneys) [1, 2], up to the death in the most critical cases. About 80% of patients have mild-to-moderate disease, 14% have severe (1) Need to identify new therapies addressing noncritical COVID- disease, and 6% are critical (namely, they develop respiratory 9 patients. failure, septic shock, and/or multiple organ dysfunction/failure) [3]. (2) Selective estrogen modulators (SERMs) can modulate activity Coronaviruses are a large family of viruses belonging to the and replication of SARS-CoV-2 by interacting with estrogen Coronaviridae family. The limited number of coronaviruses known receptors (ERs). to circulate in humans widely cause mild infections, and are 1Dompé Farmaceutici S.p.A, L’Aquila, Italy. 2Sbarro Health Research Organization, Biology Department CFT, Temple University, Philadelphia, PA, USA. 3Lazzaro Spallanzani ✉ National Institute for Infectious Diseases, IRCCS, Rome, Italy. email: [email protected] Edited by G. Melino. Received: 25 January 2021 Revised: 9 July 2021 Accepted: 25 July 2021 Official journal of CDDpress M. Allegretti et al. 2 relatively harmless respiratory human pathogens. The culprit virus DRUG REPURPOSING APPROACH belongs to the family of coronaviruses that caused two other The identification and development of effective drugs in new outbreaks, namely SARS in 2002 [4], and Middle East respiratory indications are lengthy processes that are not adequate to face syndrome (MERS) in 2012 [5]. The first known SARS-CoV case the emergency of the immediate global challenge generated by occurred in Foshan, China, in November 2002, and new cases the COVID-19 outbreak. Hence, in the present unprecedented emerged in mainland China in February 2003. The first emergence situation of deaths daily due to the epidemic, repurposing existing of MERS-CoV occurred in June 2012 in Saudi Arabia. drugs with proven safety and toxicology profiles leverage huge These events demonstrate that the threats of CoVs must not be advantage in terms of sparing time in identifying new potential underestimated and that it is essential to advance the knowledge treatments [16, 17]. Drug repurposing provides a particularly on these viruses, their replication, and interactions with the hosts attractive approach to address unmet clinical needs in the area of with the main goal to develop new pharmacological treatments infectious diseases. This “recycling” strategy based on the reuse of and vaccines. approved drugs is mostly successful, as demonstrated by Investigations on epidemiological and clinical characteristics as examples of repurposing treatments in cancer and other human well as outcomes of patients infected by SARS-CoV-2 demon- diseases [18]. Drug repurposing is a particularly attractive strated that the infection causes clusters of severe respiratory approach that substantially reduces time and costs of drug illness similar to the known SARS-CoV. The symptoms of human development, as safety, tolerability, and pharmacokinetic data infection with SARS-CoV-2 are generally fever, fatigue, dry cough, already exist [19]. For this reason, the pandemic emergency and dyspnea. Noteworthy, a considerable percentage of COVID-19 immediately triggered large efforts to identify potential effective cases rapidly progress to a severe and critical clinical condition, treatments within the pharmaceutical armamentarium for the where acute lung injury (ALI), ARDS, and pulmonary edema are management of severe/critical patients and to contain the spread the most common complications in a large number of hospitaliza- of COVID-19 infection. Several clinical trials and drug repositioning tions with the need of supplemental oxygen, invasive and studies have been conducted and many studies are currently noninvasive mechanical ventilation, or even, in very few cases of ongoing to select new agents to control this pandemic better. extra corporeal membrane oxygenation. Drugs with broad and different mechanisms of action have been In this situation, new strategies to treat and stop the spread of selected as potential candidates for the treatment of COVID-19 the disease or mitigate the impact of COVID-19 both on patients patients, such as antiviral, immune enhancing, anti-inflammatory, and the national health system are urgently needed. Specifically, or immunomodulatory agents [20]. Among the drugs previously 1234567890();,: they should aim at: (1) preventing patients with mild COVID-19 to approved for different indications and currently tested in ongoing progress toward severe/critical disease, (2) relieving hospitals from or completed clinical trials against COVID-19, several very different the burden of highly complicated patients, and (3) shortening the compounds and biologicals exist. Worth mentioning are chlor- time of viral shedding in order to curb individual infectiousness oquine and hydroxychloroquine to interfere with the viral entry and reduce the average number of secondary cases. Although and replication, anti-interleukin-6 receptor monoclonal antibodies knowledge and understanding of COVID-19 are rapidly evolving, (anti-IL-6R) for reducing the inflammatory response upon cytokine as are supportive medical cares, there is still much uncertainty on storm [21], and corticosteroids, previously used to treat SARS and the proposed treatments’ real efficacy. This fact is mainly MERS infections, and frequently administered to COVID-19 imputable to the accumulation of data from small and uncon- patients to reduce lung inflammation and prevent ARDS devel- trolled trials, observational studies, and case studies, most of them opment [22]. Table 1 reports a comprehensive, but not exhaustive, from the initial Chinese epidemic, that are affected by several list of the most popular repurposed drugs approved or under biases, intense background noise, and a long list confounding development for COVID-19 treatment. factors [6]. In any case, due to the urgent need of effective treatments, several drugs with variable targets have been and continue to be proposed for the treatment of severe or mild-to- GENDER SENSITIVITY IN COVID-19 AND SARS-COV-2 moderate COVID-19 patients worldwide, even if systemic corticoster- A gender disparity