Combination regimen of nirmatrelvir/ritonavir and molnupiravir for the treatment of persistent SARS-CoV-2 infection: A case report and a scoping review of the literature

Efficacy of initial combination therapy with anti-SARS-CoV-2 antivirals targeting viral clearance in COVID-19 patients with B-cell lymphoma treated with anti-CD20 antibodies: A retrospective single-centre study in Japan

OBJECTIVES

There is no clear treatment strategy for persistent COVID-19 infection that enables clinicians to effectively achieve viral clearance, determine the optimal time to discontinue treatment, and prevent virus reactivation. This retrospective, single-centre study aimed to analyse the effectiveness of antiviral therapies in COVID-19 patients with B-cell lymphoma receiving anti-CD20 therapy.

METHODS

Conducted at Kansai Medical University Medical Center between January 2022 and October 2024, the study examined the impact of various antiviral regimens and factors on time to viral clearance, defined as SARS-CoV-2 viral load <1 copy/μL by nasopharyngeal swab.

RESULTS

Sixty-seven cases met the inclusion criteria, with 40 having a history of bendamustine use, and 33 with combination antiviral therapy as the initial treatment. A multivariable Cox proportional hazards model revealed combination antiviral therapy as the initial regimen (HR 0.36, 95 % CI 0.20-0.65, p < 0.001) significantly shortened time to viral clearance, while bendamustine use (HR 2.74, 95 % CI 1.53-4.89, p < 0.001) significantly prolonged time to viral clearance.

CONCLUSION

This study showed the potential of early combination antiviral therapy to shorten the time to viral clearance in this high-risk patient population.

Antiviral combination regimens as rescue therapy in immunocompromised hosts with persistent COVID-19

The management of severe/prolonged SARS-CoV-2 infections in immunocompromised hosts is still challenging. We describe nine patients with hematologic malignancies with a history of unsuccessful SARS-CoV-2 treatment receiving antiviral combination treatment for persistent infection at a tertiary hospital in central Italy (University Hospital of Careggi, Florence). Combination treatments consisted of nirmatrelvir/ritonavir plus molnupiravir (n = 4), nirmatrelvir/ritonavir plus remdesivir (n = 4) or remdesivir plus molnupiravir (n = 1) for 10 days, in some cases associated with sotrovimab. Combinations were generally well tolerated. One patient obtained viral clearance but died due to the underlying disease. In eight cases, clinical and virological success was confirmed by radiological follow-up. Antivirals combination is likely to become a mainstay in the future management of COVID-19 among immunocompromised patients, but knowledge in this field is still very limited and prospective studies on larger cohorts are urgently warranted.

SARS-CoV-2 drug resistance and therapeutic approaches

In light of the transition of COVID-19 from a pandemic to an endemic phase, there is still a dire need to address challenges associated with drug resistance, particularly among immunocompromised and high-risk populations. This review explores the current state of research on SARS-CoV-2 drug resistance and underscores the ongoing need for effective therapeutic strategies. It critically evaluates existing knowledge on resistance mechanisms and therapeutic options, aiming to consolidate information and highlight areas for future research. By examining the complex interactions between the virus and its host, the review advocates for a multifaceted approach, including combination therapies, targeted drug development, and continuous surveillance of viral mutations. It also emphasizes the impact of evolving viral variants on antiviral efficacy and suggests adaptive treatment protocols. This review aims to enhance our understanding of SARS-CoV-2 drug resistance and contribute to more effective management of COVID-19 through a discussion of promising strategies such as drug repurposing and combination therapies.

Amphibian-Derived Peptides as Natural Inhibitors of SARS-CoV-2 Main Protease (Mpro): A Combined In Vitro and In Silico Approach

The COVID-19 pandemic, caused by the SARS-CoV-2 virus, has highlighted the urgent need for novel therapeutic agents targeting viral enzymes such as the main protease (Mpro), which plays a crucial role in viral replication. In this study, we investigate the inhibitory potential of 23 peptides isolated from the skin of amphibians belonging to the Hylidae and Leptodactylidae families against SARS-CoV-2 Mpro. Five peptides demonstrated significant inhibition using a colorimetric Mpro inhibition assay, with IC50 values ranging from 41 to 203 µM. Among these, peptides Hp-1081 and Hp-1971, derived from Boana pulchella, exhibited the strongest activity, comparable to the natural Mpro inhibitor quercetin. The binding mechanism of the most potent peptide, Hp-1081, was further investigated through docking and molecular dynamics (MDs) simulations and energetic analysis, which revealed key Mpro residues involved in the binding process. Moreover, because SARS-CoV-2 infection can induce ROS overproduction, the antioxidant activity of Hp-1081 was assessed, reaching 48% of DPPH radical scavenging activity at 100 µM. The most potent peptides also showed no toxicity against human erythrocytes and Artemia salina. This study provides insight into the antiviral potential of amphibian-derived peptides and highlights their applicability as natural templates for drug development targeting coronaviruses.

Successful Sequential Treatment From Remdesivir to Molnupiravir for Prolonged COVID-19 in a Patient With Follicular Lymphoma and Renal Pelvic Carcinoma: A Case Report

A 69-year-old Japanese male with follicular lymphoma and renal pelvic carcinoma presented with fever and cough, testing positive for SARS-CoV-2 via PCR. Chest CT revealed ground-glass opacities. Initially, his symptoms improved with a 10-day course of remdesivir (RDV), but they recurred. On day 42, a second 10-day course of RDV combined with dexamethasone was initiated; however, symptoms persisted, and his SARS-CoV-2 PCR test remained positive on day 72. Subsequently, a successful treatment regimen of 10 days of RDV followed by five days of molnupiravir (MOL) was administered. This study represents the first reported case of persistent SARS-CoV-2 infection successfully treated with sequential therapy transitioning from RDV to MOL, without extending the treatment duration.

Antiviral combination treatment of SARS-CoV-2 after repeated treatment failures of remdesivir monotherapy: A case report

Immunocompromised patients infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) can have a longer duration of viral shedding and persistence of symptoms. The optimal treatment strategy for these patients remains to be established. This case describes a male in his late sixties with follicular lymphoma and persistent symptoms of infection with SARS-CoV-2 variant BA.2 who was treated with remdesivir five times over a period of six months. The clinical effect of remdesivir treatment decreased over time, and further viral sequencing revealed the emergence of mutations across the SARS-CoV-2 genome. Due to the lack of other treatment options, the patient was treated with a combination of remdesivir and molnupiravir for 10 days, and epcoritamab was discontinued, which led to the cessation of symptoms. This case illustrates the risk of a diminished effect of remdesivir with prolonged use and the need for treatment guidelines for immunocompromised patients with persistent COVID-19.

COVID-19-related Pneumonitis in Immunocompromised Patients: Reviewing Clinical Features and Management Approaches

In this case series, we explore persistent SARS-CoV-2 infection and its resultant pneumonitis within a cohort of immunocompromised patients. We elucidate the complex interplay between immunosuppression and COVID-19 by examining four patients who experienced prolonged viral shedding and recurrent respiratory failure due to their compromised immune systems. This series elucidates the clinical presentation, diagnostic challenges, and therapeutic strategies. We also summarize existing literature regarding persistent SARS-CoV-2 infection in immunocompromised individuals. Our findings support the use of a tailored treatment approach using a proposed diagnostic and management algorithm to standardize care and optimize outcomes.

Prospects of Innovative Therapeutics in Combating the COVID-19 Pandemic

The sudden global crisis of COVID-19, driven by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), demands swift containment measures due to its rapid spread and numerous problematic mutations, which complicate the establishment of herd immunity. With escalating fatalities across various nations no foreseeable end in sight, there is a pressing need to create swiftly deployable, rapid, cost-effective detection, and treatment methods. While various steps are taken to mitigate the transmission and severity of the disease, vaccination is proven throughout mankind history as the best method to acquire immunity and circumvent the spread of infectious diseases. Nonetheless, relying solely on vaccination might not be adequate to match the relentless viral mutations observed in emerging variants of SARS-CoV-2, including alterations to their RBD domain, acquisition of escape mutations, and potential resistance to antibody binding. Beyond the immune system activation achieved through vaccination, it is crucial to develop new medications or treatment methods to either impede the infection or enhance existing treatment modalities. This review emphasizes innovative treatment strategies that aim to directly disrupt the virus's ability to replicate and spread, which could play a role in ending the SARS-CoV-2 pandemic.

Antiviral therapies for the management of persistent coronavirus disease 2019 in immunocompromised hosts: A narrative review

Antiviral agents with activity against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) have played a critical role in disease management; however, little is known regarding the efficacy of these medications in the treatment of SARS-CoV-2 infection in immunocompromised patients, particularly in the management of persistent SARS-CoV-2 positivity. This narrative review discusses the management of persistent coronavirus disease 2019 in immunocompromised hosts, with a focus on antiviral therapies. We identified 84 cases from the literature describing a variety of approaches, including prolonged antiviral therapy (n = 11), combination antivirals (n = 13), and mixed therapy with antiviral and antibody treatments (n = 60). A high proportion had an underlying haematologic malignancy (n = 67, 80%), and were in receipt of anti-CD20 agents (n = 51, 60%). Success was reported in 70 cases (83%) which varied according to the therapy type. Combination therapies with antivirals may be an effective approach for individuals with persistent SARS-CoV-2 positivity, particularly those that incorporate treatments aimed at increasing neutralizing antibody levels. Any novel approaches taken to this difficult management dilemma should be mindful of the emergence of antiviral resistance.

Joint analysis of vaccination effectiveness and antiviral drug effectiveness for COVID-19: a causal inference approach

OBJECTIVES

This study aims to estimate the causal effects of oral antivirals and vaccinations in the prevention of all-cause mortality and progression to severe COVID-19 in an integrative setting with both antivirals and vaccinations considered as interventions.

METHODS

We identified hospitalized adult patients (i.e. aged 18 or above) in Hong Kong with confirmed SARS-CoV-2 infection between March 16, 2022, and December 31, 2022. An inverse probability-weighted (IPW) Andersen-Gill model with time-dependent predictors was used to address immortal time bias and produce causal estimates for the protection effects of oral antivirals and vaccinations against severe COVID-19.

RESULTS

Given prescription is made within 5 days of confirmed infection, nirmatrelvir-ritonavir is more effective in providing protection against all-cause mortality and development into severe COVID-19 than molnupiravir. There was no significant difference between CoronaVac and Comirnaty in the effectiveness of reducing all-cause mortality and progression to severe COVID-19.

CONCLUSIONS

The use of oral antivirals and vaccinations causes lower risks of all-cause mortality and progression to severe COVID-19 for hospitalized SARS-CoV-2 patients.

Chimeric antigen receptor T-cell therapy after COVID-19 in refractory high-grade B-cell lymphoma

Although chimeric antigen receptor T-cell (CAR-T) therapies have dramatically improved the outcomes of relapsed/refractory B-cell malignancies, recipients suffer from severe humoral immunodeficiencies. Furthermore, patients with coronavirus disease 2019 (COVID-19) have a poor prognosis, as noted in several case reports of recipients who had COVID-19 before the infusion. We report the case of a 70-year-old woman who developed COVID-19 immediately before CAR-T therapy for high-grade B-cell lymphoma. She received Tixagevimab-Cilgavimab chemotherapy and radiation therapy but never achieved remission. She was transferred to our hospital for CAR-T therapy, but developed COVID-19. Her symptoms were mild and she was treated with long-term molnupiravir. On day 28 post-infection, lymphodepleting chemotherapy was restarted after a negative polymerase chain reaction (PCR) test was confirmed. The patient did not experience recurrence of COVID-19 symptoms or severe cytokine release syndrome. Based on the analysis and comparison of the previous reports with this case, we believe that CAR-T therapy should be postponed until a negative PCR test is confirmed. In addition, Tixagevimab-Cilgavimab and long term direct-acting antiviral agent treatment can be effective prophylaxis for severe COVID-19 and shortening the duration of infection.

In Vitro Combinatorial Activity of Direct Acting Antivirals and Monoclonal Antibodies against the Ancestral B.1 and BQ.1.1 SARS-CoV-2 Viral Variants

Combination antiviral therapy may be helpful in the treatment of SARS-CoV-2 infection; however, no clinical trial data are available, and combined use of direct-acting antivirals (DAA) and monoclonal antibodies (mAb) has been reported only anecdotally. To assess the cooperative effects of dual drug combinations in vitro, we used a VERO E6 cell-based in vitro system with the ancestral B.1 or the highly divergent BQ.1.1 virus to test pairwise combinations of the licensed DAA, including nirmatrelvir (NRM), remdesivir (RDV) and the active metabolite of molnupiravir (EIDD-1931) as well the combination of RDV with four licensed mAbs (sotrovimab, bebtelovimab, cilgavimab, tixagevimab; tested only with the susceptible B.1 virus). According to SynergyFinder 3.0 summary and weighted scores, all the combinations had an additive effect. Within DAA/DAA combinations, paired scores with the B.1 and BQ.1.1 variants were comparable. In the post hoc analysis weighting synergy by concentrations, several cases of highly synergistic scores were detected at specific drug concentrations, both for DAA/DAA and for RDV/mAb combinations. This was supported by in vitro confirmation experiments showing a more than a linear shift of a drug-effective concentration (IC50) at increasing concentrations of the companion drug, although the effect was prominent with DAA/DAA combinations and minimal or null with RDV/mAb combinations. These results support the cooperative effects of dual drug combinations in vitro, which should be further investigated in animal models before introduction into the clinic.

Optimizing COVID-19 treatment in immunocompromised patients: early combination therapy with remdesivir, nirmatrelvir/ritonavir and sotrovimab

BACKGROUND

Morbidity and mortality are higher in immunocompromised patients affected by COVID-19 than in the general population. Some authors have successfully used antiviral combination, but never in the early phase of the infection.

METHODS

We conducted a retrospective cohort study to determine the efficacy and safety of the combination of two antivirals, with and without a monoclonal antibody (mAb), in both the early (within 10 days of symptoms) and in a later phase (after 10 days) of SARS-CoV-2 infection in immunocompromised patients admitted to our Facility.

RESULTS

We treated 11 patients (seven in an early phase and four in a late phase of COVID-19) with 10 days of intravenous remdesivir plus five days of oral nirmatelvir/ritonavir, also combined with sotrovimab in 10/11 cases. Notably, all the "early" patients reached virological clearance at day 30 from the end of the therapy and were alive and well at follow-up, whereas the corresponding numbers in the "late" patients were 50% and 75%. Patients in the "late" group more frequently needed oxygen supplementation (p = 0.015) and steroid therapy (p = 0.045) during admission and reached higher COVID-19 severity (p = 0.017).

DISCUSSION

The combination of antiviral and sotrovimab in the early phase of COVID-19 is well tolerated by immunocompromised patients and is associated with 100% of virological clearance. Patients treated later have lower response rates and higher disease severity, but whether therapy plays a causative role in such findings has yet to be determined.

Antiviral combination therapies for persistent COVID-19 in immunocompromised patients

OBJECTIVES

After the third year of the COVID-19 pandemic, most of the severe COVID-19 burden falls upon immunocompromised patients who cannot mount an endogenous immune response after both vaccination and/or natural infection. They also experience persistent SARS-CoV-2 infection with high viral loads often unsuccessfully managed by the standard antiviral monotherapy regimen initially validated for treatment of COVID-19 immunocompetent patients, only. The off-label prescription of such monotherapy regimens in immunocompromised patients is likely to drive the emergence of treatment-related immune escape, relapses, excess morbidity, and mortality from both COVID-19 and delayed treatment of the underlying disorders. A possible treatment approach to mitigate such consequence is based on combined antiviral therapies.

METHODS

We searched PubMed for case reports, case series and clinical trials reporting the usage of combined antiviral therapies for COVID-19.

RESULTS

In this narrative review, we show that combinations of either small molecule antivirals or small molecule antiviral plus passive immunotherapies are safe and effective in small cohorts reported so far.

CONCLUSION

Considering the progressive loss of efficacy of all authorized anti-spike monoclonal antibodies, promising regimen options are reserved to combinations of small molecule antivirals and COVID-19 convalescent plasma from vaccinated donors.

Molnupiravir Revisited-Critical Assessment of Studies in Animal Models of COVID-19

Molnupiravir, a prodrug known for its broad antiviral activity, has demonstrated efficacy in animal models of COVID-19, prompting clinical trials, in which initial results indicated a significant effect against the disease. However, subsequent clinical studies did not confirm these findings, leading to the refusal of molnupiravir for permanent market authorization in many countries. This report critically assessed 22 studies published in 18 reports that investigated the efficacy of molnupiravir in animal models of COVID-19, with the purpose of determining how well the design of these models informed human studies. We found that the administered doses of molnupiravir in most studies involving animal COVID-19 models were disproportionately higher than the dose recommended for human use. Specifically, when adjusted for body surface area, over half of the doses of molnupiravir used in the animal studies exceeded twice the human dose. Direct comparison of reported drug exposure across species after oral administration of molnupiravir indicated that the antiviral efficacy of the dose recommended for human use was underestimated in some animal models and overestimated in others. Frequently, molnupiravir was given prophylactically or shortly after SARS-CoV-2 inoculation in these models, in contrast to clinical trials where such timing is not consistently achieved. Furthermore, the recommended five-day treatment duration for humans was exceeded in several animal studies. Collectively, we suggest that design elements in the animal studies under examination contributed to a preference favoring molnupiravir, and thus inflated expectations for its efficacy against COVID-19. Addressing these elements may offer strategies to enhance the clinical efficacy of molnupiravir for the treatment of COVID-19. Such strategies include dose increment, early treatment initiation, administration by inhalation, and use of the drug in antiviral combination therapy.

Persistent SARS-CoV-2 infection in patients with B-cell deficiency: a case series of successful antiviral treatment of four patients

Persistent severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection in immunocompromised patients remains a major medical challenge. Diagnosing the syndrome is difficult as symptoms may mimic other diseases and treatment guidelines are lacking. We describe a case series of four patients with persistent SARS-CoV-2 infection that all had an underlying B-cell deficiency due to rituximab treatment (in one case in combination with epcoritamab). In all four patients, it was initially difficult to recognize the persistent disease, leading to a duration of illness between 45 and 242 days. Two patients were only positive for SARS-CoV-2 by polymerase chain reaction (PCR) in the nasopharynx at the beginning of the disease but were later repeatedly negative. However, when bronchoalveolar lavage was performed, a positive SARS-CoV-2 PCR was revealed from the lower airways in both patients. The difficulties establishing diagnosis contributed to these two patients' long disease course. The longest disease duration was in the patient treated with rituximab and epcoritamab, who also responded poorly to single standard antiviral treatment. This patient ultimately cleared the infection after administering a combination treatment with remdesivir and nirmatrelvir/ritonavir. After a confirmed diagnosis, the other three patients cleared the infection when they were finally treated with antivirals. Increasing clinicians' awareness of this condition is important as it might be treatable once diagnosed. Further studies are warranted to define the condition and treatment strategy with greater precision.

Key Considerations during the Transition from the Acute Phase of the COVID-19 Pandemic: A Narrative Review

The COVID-19 pandemic has been met with an unprecedented response from the scientific community, leading to the development, investigation, and authorization of vaccines and antivirals, ultimately reducing the impact of SARS-CoV-2 on global public health. However, SARS-CoV-2 is far from being eradicated, continues to evolve, and causes substantial health and economic burdens. In this narrative review, we posit essential points on SARS-CoV-2 and its responsible management during the transition from the acute phase of the COVID-19 pandemic. As discussed, despite Omicron (sub)variant(s) causing clinically milder infections, SARS-CoV-2 is far from being a negligible pathogen. It requires continued genomic surveillance, particularly if one considers that its future (sub)lineages do not necessarily have to be milder. Antivirals and vaccines remain the essential elements in COVID-19 management. However, the former could benefit from further development and improvements in dosing, while the seasonal administration of the latter requires simplification to increase interest and tackle vaccine hesitancy. It is also essential to ensure the accessibility of COVID-19 pharmaceuticals and vaccines in low-income countries and improve the understanding of their use in the context of the long-term goals of SARS-CoV-2 management. Regardless of location, the primary role of COVID-19 awareness and education must be played by healthcare workers, who directly communicate with patients and serve as role models for healthy behaviors.

Sequential or Combination Treatments as Rescue Therapies in Immunocompromised Patients with Persistent SARS-CoV-2 Infection in the Omicron Era: A Case Series

Prolonged SARS-CoV-2 infections are widely described in immunosuppressed patients, but safe and effective treatment strategies are lacking. We aimed to outline our approach to treating persistent COVID-19 in patients with immunosuppression from different causes. In this case series, we retrospectively enrolled all immunosuppressed patients with persistent SARS-CoV-2 infections treated at our centers between March 2022 and February 2023. Patients received different sequential or combination regimens, including antivirals (remdesivir, nirmatrelvir/ritonavir, or molnupiravir) and/or monoclonal antibodies (mAbs) (tixagevimab/cilgavimab or sotrovimab). The main outcome was a complete virological response (negative SARS-CoV-2 RT-PCR on nasopharyngeal swabs) at the end of treatment. Fifteen patients were included as follows: eleven (11/15; 73%) with hematological disease and four (4/15; 27%) with recently diagnosed HIV/AIDS infection. Six patients (6/15; 40%) received a single antiviral course, four patients (4/15; 27%) received an antiviral and mAbs sequentially, and two patients (13%) received three lines of treatment (a sequence of three antivirals or two antivirals and mAbs). A combination of two antivirals or one antiviral plus mAbs was administered in three cases (3/15, 20%). One patient died while still positive for SARS-CoV-2, while fourteen (14/15; 93%) tested negative within 16 days after the end of treatment. The median time to negativization since the last treatment was 2.5 days. Both sequential and combination regimens used in this study demonstrated high efficacy and safety in the high-risk group of immunosuppressed patients.

An Overview on Anti-COVID-19 Drug Achievements and Challenges Ahead

The appearance of several coronavirus pandemics/epidemics during the last two decades (SARS-CoV-1 in 2002, MERS-CoV in 2012, and SARS-CoV-2 in 2019) indicates that humanity will face increasing challenges from coronaviruses in the future. The emergence of new strains with similar transmission characteristics as SARS-CoV-2 and mortality rates similar to SARS-CoV-1 (∼10% mortality) or MERS-CoV (∼35% mortality) in the future is a terrifying possibility. Therefore, getting enough preparations to face such risks is an inevitable necessity. The present study aims to review the drug achievements and challenges in the fight against SARS-CoV-2 with a combined perspective derived from pharmacology, pharmacotherapy, and medicinal chemistry insights. Appreciating all the efforts made during the past few years, there is strong evidence that the desired results have not yet been achieved and research in this area should still be pursued seriously. By expressing some pessimistic possibilities and concluding that the drug discovery and pharmacotherapy of COVID-19 have not been successful so far, this short essay tries to draw the attention of responsible authorities to be more prepared against future coronavirus epidemics/pandemics.

Successful treatment of persisting SARS-CoV-2 infection in an immunocompromised patient with repeated nirmatrelvir/ritonavir courses: a case report

BACKGROUND

In immunocompromised patients, persistent SARS-CoV-2 viral shedding and relapsing COVID-19 pneumonia have been described. Currently, little is known about the management of persisting COVID-19, and immunocompromised patients are recommended to be treated using antivirals and immunomodulatory therapies at similar doses and durations as the general population. Previous case reports have described treatment with repeated and prolonged courses of remdesivir and some evidence is emerging in the use of nirmatrelvir/ritonavir combination (NMV/r).

METHODS

We describe a patient with recent chemotherapy including rituximab for follicular lymphoma with persisting SARS-CoV-2 infection. Polymerase chain reaction tests (PCR), cycle threshold values and blood SARS-CoV-2 antigen levels were evaluated.

RESULTS

The patient presented with persisting SARS-CoV-2 with relapsing COVID-19 pneumonia. The patient was treated successfully with repeated courses of NMV/r without any observed adverse effects. After the third, prolonged course, the patient remained afebrile and PCR negative, and no relapses have been observed four months after the third NMV/r course.

CONCLUSIONS

Nirmatrelvir-ritonavir could offer a more accessible alternative to remdesivir. Further research and guidelines for persisting SARS-CoV-2 infection in immunocompromised patients are urgently needed.

Synergistic Activity of Remdesivir-Nirmatrelvir Combination on a SARS-CoV-2 In Vitro Model and a Case Report

BACKGROUND

This study aims to investigate the activity of the remdesivir-nirmatrelvir combination against Severe Acute Respiratory Syndrome Coronavirus-2 (SARS-CoV-2) and to report a case of Coronavirus Disease 2019 (COVID-19) cured with this combination.

METHODS

A Vero E6 cell-based infection assay was used to investigate the in vitro activity of the remdesivir-nirmatrelvir combination. The SARS-CoV-2 strains tested were 20A.EU1, BA.1 and BA.5. After incubation, a viability assay was performed. The supernatants were collected and used for viral titration. The Highest Single Agent (HSA) reference model was calculated. An HSA score >10 is considered synergic.

RESULTS

Remdesivir and nirmatrelvir showed synergistic activity at 48 and 72 h, with an HSA score of 52.8 and 28.6, respectively (p < 0.0001). These data were confirmed by performing supernatant titration and against the omicron variants: the combination reduced the viral titer better than the more active compound alone. An immunocompromised patient with prolonged and critical COVID-19 was successfully treated with remdesivir, nirmatrelvir/ritonavir, tixagevimab/cilgavimab and dexamethasone, with an excellent clinical-radiological response. However, she required further off-label prolonged therapy with nirmatrelvir/ritonavir until she tested negative.

CONCLUSIONS

Remdesivir-nirmatrelvir combination has synergic activity in vitro. This combination may have a role in immunosuppressed patients with severe COVID-19 and prolonged viral shedding.