Background: COVID-19 represents a threat for frailty patients. Objective: Investigate efficacy, safety and economic value of treatment with Molnupiravir in a cohort of fragile patients affected by COVID-19. Methods: Observational, prospective study. The data collected allowed to assess efficacy and safety of Molnupiravir in real life, compare the results with a subgroup of patients treated with Nirmatrelvir-Ritonavir and to effect a cost-effectiveness analysis. Results: In January-December 2022, 435 patients (225 males, 220 females; median age 72 years), were enrolled; 24 patients were unvaccinated, 280 patients had ≥2 risk factors. Molnupiravir appeared to give better results than the SOC both clinically and economically. In these patients in comparison with literature data or SOC, hospitalization was 2.5% vs 6.8% (p<0.005), overall adverse effects 14,3% vs 30.4% (p<0.0001), severe adverse effects 2.6 vs 6.9% (p<0.001), thus involving a potential total savings of about € 92.954 per patient (8% of standard of care cost). Conclusions: early Molnupiravir treatment helped fragile patients who partially responded to vaccine, or with absolute contraindications to vaccination, to overcome COVID-19 without the need of hospitalization. Molnupiravir represents a clinical and economic effective treatment, avoiding disease progression in old patients suffering from multiple pathologies and taking several drugs.

Introduction: 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). This data has been confirmed 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 up to the negativization. Conclusion: 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.

The Main Protease (Mpro) plays a pivotal role in the replication of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and is considered a highly conserved viral target. Disruption of the catalytic activity of Mpro produces a detrimental effect on the course of the infection, making this target one of the most attractive for the treatment of COVID-19. The current success of the SARS-CoV-2 Mpro inhibitor Nirmatrelvir, the first oral drug for the treatment of severe forms of COVID-19, has further focused the attention of researchers on this important viral target, making the search for new Mpro inhibitors a thriving and exciting field for the development of antiviral drugs active against SARS-CoV-2 and related coronaviruses.

Introduction: The development of effective vaccines has partially mitigated the trend of the SARS-CoV-2 pandemic, however, the need for orally available antiviral drugs persists. This study aims to investigate the activity of molnupiravir in combination with nirmatrelvir or GC376 on SARS-CoV-2 to verify the synergistic effect. Methods: The SARS-CoV-2 strains 20A.EU, BA.1 and BA.2 were used to infect Vero E6 in presence of antiviral compounds alone or in combinations using 5 two-fold serial dilution of compound concentrations ≤EC90. After 48 and 72 h post-infection, viability was performed using MTT reduction assay. Supernatants were collected for plaque-assay titration. All experiments were conducted three times and in triplicate. The synergistic score was calculated using Synergy Finder version 2. Results: All compounds reached micromolar EC90. Molnupiravir and GC376 showed a synergistic activity at 48 h with an HSA score of 19.33 (p<0.0001) and an additive activity at 72 h with an HSA score of 8.61 (p<0.0001). Molnupiravir and nirmatrelvir showed a synergistic activity both at 48 h and 72 h with an HSA score of 14.2 (p=0.01) and 13.08 (p<0.0001), respectively. Conclusion: Molnupiravir associated with one of the two protease-inhibitors nirmatrelvir and GC376 showed good additive-synergic activity in vitro.