Florian Kabinger

Bio: Florian Kabinger is an academic researcher from Max Planck Society. The author has contributed to research in topics: Base pair & RNA polymerase. The author has an hindex of 2, co-authored 2 publications receiving 20 citations.

Mechanism of molnupiravir-induced SARS-CoV-2 mutagenesis.

Abstract: Molnupiravir is an orally available antiviral drug candidate currently in phase III trials for the treatment of patients with COVID-19. Molnupiravir increases the frequency of viral RNA mutations and impairs SARS-CoV-2 replication in animal models and in humans. Here, we establish the molecular mechanisms underlying molnupiravir-induced RNA mutagenesis by the viral RNA-dependent RNA polymerase (RdRp). Biochemical assays show that the RdRp uses the active form of molnupiravir, β-D-N4-hydroxycytidine (NHC) triphosphate, as a substrate instead of cytidine triphosphate or uridine triphosphate. When the RdRp uses the resulting RNA as a template, NHC directs incorporation of either G or A, leading to mutated RNA products. Structural analysis of RdRp-RNA complexes that contain mutagenesis products shows that NHC can form stable base pairs with either G or A in the RdRp active center, explaining how the polymerase escapes proofreading and synthesizes mutated RNA. This two-step mutagenesis mechanism probably applies to various viral polymerases and can explain the broad-spectrum antiviral activity of molnupiravir.

Mechanism of molnupiravir-induced SARS-CoV-2 mutagenesis

Abstract: Molnupiravir is an orally available antiviral drug candidate that is in phase III trials for the treatment of COVID-19 patients1,2. Molnupiravir increases the frequency of viral RNA mutations3,4 and impairs SARS-CoV-2 replication in animal models4-6 and in patients2. Here we establish the molecular mechanisms that underlie molnupiravir-induced RNA mutagenesis by the RNA-dependent RNA polymerase (RdRp) of the coronavirus SARS-CoV-2. Biochemical assays show that the RdRp readily uses the active form of molnupiravir, {beta}-D-N4-hydroxycytidine (NHC) triphosphate, as a substrate instead of CTP or UTP. Incorporation of NHC monophosphate into nascent RNA does not impair further RdRp progression. When the RdRp uses the resulting RNA as a template, NHC directs incorporation of either G or A, leading to mutated RNA products. Structural analysis of RdRp-RNA complexes containing mutagenesis products shows that NHC can form stable base pairs with either G or A in the RdRp active center, explaining how the polymerase escapes proofreading and synthesizes mutated RNA. This two-step mutagenesis mechanism likely applies to various viral polymerases and can explain the broad-spectrum antiviral activity of molnupiravir.

Molnupiravir for Oral Treatment of Covid-19 in Nonhospitalized Patients

Abstract: New treatments are needed to reduce the risk of progression of coronavirus disease 2019 (Covid-19). Molnupiravir is an oral, small-molecule antiviral prodrug that is active against severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2).We conducted a phase 3, double-blind, randomized, placebo-controlled trial to evaluate the efficacy and safety of treatment with molnupiravir started within 5 days after the onset of signs or symptoms in nonhospitalized, unvaccinated adults with mild-to-moderate, laboratory-confirmed Covid-19 and at least one risk factor for severe Covid-19 illness. Participants in the trial were randomly assigned to receive 800 mg of molnupiravir or placebo twice daily for 5 days. The primary efficacy end point was the incidence hospitalization or death at day 29; the incidence of adverse events was the primary safety end point. A planned interim analysis was performed when 50% of 1550 participants (target enrollment) had been followed through day 29.A total of 1433 participants underwent randomization; 716 were assigned to receive molnupiravir and 717 to receive placebo. With the exception of an imbalance in sex, baseline characteristics were similar in the two groups. The superiority of molnupiravir was demonstrated at the interim analysis; the risk of hospitalization for any cause or death through day 29 was lower with molnupiravir (28 of 385 participants [7.3%]) than with placebo (53 of 377 [14.1%]) (difference, -6.8 percentage points; 95% confidence interval [CI], -11.3 to -2.4; P = 0.001). In the analysis of all participants who had undergone randomization, the percentage of participants who were hospitalized or died through day 29 was lower in the molnupiravir group than in the placebo group (6.8% [48 of 709] vs. 9.7% [68 of 699]; difference, -3.0 percentage points; 95% CI, -5.9 to -0.1). Results of subgroup analyses were largely consistent with these overall results; in some subgroups, such as patients with evidence of previous SARS-CoV-2 infection, those with low baseline viral load, and those with diabetes, the point estimate for the difference favored placebo. One death was reported in the molnupiravir group and 9 were reported in the placebo group through day 29. Adverse events were reported in 216 of 710 participants (30.4%) in the molnupiravir group and 231 of 701 (33.0%) in the placebo group.Early treatment with molnupiravir reduced the risk of hospitalization or death in at-risk, unvaccinated adults with Covid-19. (Funded by Merck Sharp and Dohme; MOVe-OUT ClinicalTrials.gov number, NCT04575597.).

Efficacy and safety of three new oral antiviral treatment (molnupiravir, fluvoxamine and Paxlovid) for COVID-19：a meta-analysis

Abstract: Abstract Background The coronavirus disease (COVID-19) epidemic has not been completely controlled. Although great achievements have been made in COVID-19 research and many antiviral drugs have shown good therapeutic effects against COVID-19, a simple oral antiviral drug for COVID-19 has not yet been developed. We conducted a meta-analysis to investigate the improvement in mortality or hospitalization rates and adverse events among COVID-19 patients with three new oral antivirals (including molnupiravir, fluvoxamine and Paxlovid). Methods We searched scientific and medical databases, such as PubMed, Web of Science, Embase and Cochrane Library for relevant articles and screened the references of retrieved studies on COVID-19. Results A total of eight studies were included in this study. The drug group included 2440 COVID-19 patients, including 54 patients who died or were hospitalized. The control group included a total of 2348 COVID-19 patients, including 118 patients who died or were hospitalized. The overall odds ratio (OR) of mortality or hospitalization was 0.33 (95% confidence interval [CI], 0.22–0.49) for COVID-19 patients in the drug group and placebo group, indicating that oral antiviral drugs were effective for COVID-19 patients and reduced the mortality or hospitalization by approximately 67%. Conclusions This study showed that three novel oral antivirals (molnupiravir, fluvoxamine and Paxlovid) are effective in reducing the mortality and hospitalization rates in patients with COVID-19. In addition, the three oral drugs did not increase the occurrence of adverse events, thus exhibiting good overall safety. These three oral antiviral drugs are still being studied, and the available data suggest that they will bring new hope for COVID-19 recovery and have the potential to be a breakthrough and very promising treatment for COVID-19. KEY MESSAGES Many antiviral drugs have shown good therapeutic effects, and there is no simple oral antiviral drug for COVID-19 patients. Meta-analysis was conducted for three new oral antivirals to evaluate the improvement in mortality or hospitalization rates and adverse events among COVID-19 patients. We focussed on three new oral Coronavirus agents (molnupiravir, fluvoxamine and Paxlovid) and hope to provide guidance for the roll-out of oral antivirals.

A phase 2a clinical trial of molnupiravir in patients with COVID-19 shows accelerated SARS-CoV-2 RNA clearance and elimination of infectious virus

Abstract: There is an urgent need for an effective, oral, direct-acting therapeutic to block transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and prevent progression to severe coronavirus disease 2019 (COVID-19). In a phase 2a double-blind, placebo-controlled, randomized, multicenter clinical trial, we evaluated the safety, tolerability, and antiviral efficacy of the nucleoside analog molnupiravir in 202 unvaccinated participants with confirmed SARS-CoV-2 infection and symptom duration <7 days. Participants were randomized 1:1 to receive molnupiravir (200 mg) or placebo and then 3:1 to receive molnupiravir (400 or 800 mg) or placebo, orally twice daily for 5 days. Antiviral activity was assessed by reverse transcriptase polymerase chain reaction (RT-PCR) for SARS-CoV-2 RNA in nasopharyngeal swabs. Infectious virus was assessed by inoculation of cultured Vero cells with samples from nasopharyngeal swabs and was detected by RT-PCR. Time to viral RNA clearance (primary endpoint) was decreased in the 800-mg molnupiravir group (median 14 days) compared to the placebo group (median 15 days) (log rank P value = 0.013). Of participants receiving 800 mg of molnupiravir, 92.5% achieved viral RNA clearance compared with 80.3% of placebo recipients by study end (4 weeks). Infectious virus (secondary endpoint) was detected in swabs from 1.9% of the 800-mg molnupiravir group compared with 16.7% of the placebo group at day 3 of treatment (P = 0.016). At day 5 of treatment, infectious virus was not isolated from any participants receiving 400 or 800 mg of molnupiravir compared with 11.1% of placebo recipients (P = 0.034 and 0.027, respectively). Molnupiravir was well tolerated across all doses.

Structures and functions of coronavirus replication-transcription complexes and their relevance for SARS-CoV-2 drug design.

Abstract: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has killed millions of people and continues to cause massive global upheaval. Coronaviruses are positive-strand RNA viruses with an unusually large genome of ~30 kb. They express an RNA-dependent RNA polymerase and a cohort of other replication enzymes and supporting factors to transcribe and replicate their genomes. The proteins performing these essential processes are prime antiviral drug targets, but drug discovery is hindered by our incomplete understanding of coronavirus RNA synthesis and processing. In infected cells, the RNA-dependent RNA polymerase must coordinate with other viral and host factors to produce both viral mRNAs and new genomes. Recent research aiming to decipher and contextualize the structures, functions and interplay of the subunits of the SARS-CoV-2 replication and transcription complex proteins has burgeoned. In this Review, we discuss recent advancements in our understanding of the molecular basis and complexity of the coronavirus RNA-synthesizing machinery. Specifically, we outline the mechanisms and regulation of RNA translation, replication and transcription. We also discuss the composition of the replication and transcription complexes and their suitability as targets for antiviral therapy. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and other coronaviruses rely on a cohort of specialized viral proteins to transcribe and replicate their RNA genomes. Recent studies have improved our understanding of coronavirus RNA translation, replication and transcription, and offer new therapeutic targets.

Emerging COVID-19 variants and their impact on SARS-CoV-2 diagnosis, therapeutics and vaccines

Abstract: Abstract The emergence of novel and evolving variants of SARS-CoV-2 has fostered the need for change in the form of newer and more adaptive diagnostic methods for the detection of SARS-CoV-2 infections. On the other hand, developing rapid and sensitive diagnostic technologies is now more challenging due to emerging variants and varying symptoms exhibited among the infected individuals. In addition to this, vaccines remain the major mainstay of prevention and protection against infection. Novel vaccines and drugs are constantly being developed to unleash an immune response for the robust targeting of SARS-CoV-2 and its associated variants. In this review, we provide an updated perspective on the current challenges posed by the emergence of novel SARS-CoV-2 mutants/variants and the evolution of diagnostic techniques to enable their detection. In addition, we also discuss the development, formulation, working mechanisms, advantages, and drawbacks of some of the most used vaccines/therapeutic drugs and their subsequent immunological impact. Key message The emergence of novel variants of the SARS-CoV-2 in the past couple of months, highlights one of the primary challenges in the diagnostics, treatment, as well as vaccine development against the virus. Advancements in SARS-CoV-2 detection include nucleic acid based, antigen and immuno- assay-based and antibody-based detection methodologies for efficient, robust, and quick testing; while advancements in COVID-19 preventive and therapeutic strategies include novel antiviral and immunomodulatory drugs and SARS-CoV-2 targeted vaccines. The varied COVID-19 vaccine platforms and the immune responses induced by each one of them as well as their ability to battle post-vaccination infections have all been discussed in this review.