Review | categories and mechanisms of action of covid-19 neutralizing antibodies and small molecule drugs

stay 2020 year SARS-Cov-2 The initial outbreak of covid COVID-19 caused by the virus , The researchers initially thought SARS-Cov-2 The evolution of viral genome diversity is slow . however , One and a half years after the COVID-19 , All over the world SARS-Cov-2 Virus mutant . These mutations are important for SARS-Cov-2 Viruses are harmless or slightly beneficial , For example, mutations lead to the enhancement of transmission and virulence, as well as immune escape ability . The first to find SARS-Cov-2 Viral genome mutations are Spike protein D614G, This mutation causes the virus to spread more efficiently , The mutant soon became the main infection strain in the world . At present, the identified mutants are 5 Kind of , Namely Alpha, Beta, Gamma, Delta , Omicron, They all have their own typical mutation sites . overall ,Spike Proteins are particularly prone to accumulate mutations , In addition, these mutants also have some mutations related to host immune escape .

Covid-19 mutant Spike Protein mutation site

At present, many vaccine research and development are based on Spike protein , The population vaccination plan of this kind of vaccine has also been promoted at full speed . However , Both real-world and serological test data show Omicron It can escape the immunity of vaccinated hosts , It can escape the immunity of the previously infected host . In the face of mutants whose transmission ability and immune escape ability have been continuously improved , The role of existing vaccines in resisting the invasion of virus variants is constantly being weakened . Virtue dwarfs vice , The road is high . Once the virus breaks through the human immune system , We must also have other killer maces to stop the reproduction of the virus in the body . Fortunately, , Researchers have developed several antiviral drugs that have been approved for marketing or are in clinical research .

Antiviral drugs can be divided into two categories ： Targeting S Neutralizing antibodies to proteins and small molecule drugs that interfere with virus replication .

Covid-19 neutralizing antibody drug

New crown neutralizing antibody （monoclonal antibodies ,mAbs） Antiviral mechanism

Due to its high specificity and reliability , Can neutralize SARS-Cov-2 Humanized monoclonal antibodies against mutant strains have become a very attractive new crown treatment , The main targets of these antibodies are SARS-Cov-2 Viruses Spike Albuminous Receptor-binding domain (RBD) perhaps N-terminal domain (NTD).Spike Protein consists of a 3 The same monomer constitutes , Its monomer consists of S1 Subunits and S2 Subunit composition , It can interact with ACE2 receptor binding , Mediate the fusion and entry of virus and host cell membrane .S1 Subunit domains include NTD and RBD,S2 Subunit domains include FP(fusion peptide),HR1( heptad repeats),HR2,TM(transmembrane domain ),CP(cytoplasmic tail ).RBD Specific monoclonal antibodies can bind Spike Protein RBD In the domain RBM Motif （receptor-binding motif）.RBM Responsible for viruses and host cells ACE2 Preliminary combination of , Initiating virus entry into cells .RBD Specific monoclonal antibodies can block RBM—ACE2 Interaction of , yes ACE2 Blocker of .

novel coronavirus Spike Protein structure

Picture citation ：Thomas Splettstoesser;www.scistyle.com

Spike Proteins have different conformations in host cells , These conformations are based on RBD The location of （ Up or down ） Named after the . According to the different conformations of McAbs RBD, It can be divided into 4 Kind of （I, II, III, and IV）.class I NAbs Only can “ Up ” Of RBD,class II NAbs perhaps class III NAbs Can identify " Up or down " Of RBDs,class IV NAbs Can combine RBD Conservative areas (core I region) perhaps “ Up ” Of RBD(core II region).Class IV core I region-dependent NAbs It has very spectral resistance SARS-Cov-2 Original plant , Mutant , And other related coronavirus activities .

Spike Protein structure , conformation , Depend on RBD Monoclonal antibody drugs

Research and development status of covid-19 neutralizing antibody

2021 year 12 month 8 Number , AstraZeneca （AstraZeneca） Announce its long-acting neutralizing antibody against novel coronavirus Evusheld（AZD7442） Get America FDA Emergency use authorization （EUA）.Evusheld It is a combination of two long-acting monoclonal antibodies , It is the only antibody therapy authorized in the United States to prevent covid-19 before exposure , It is also the only covid-19 antibody injected intramuscularly （150mg tixagevimab and 150mg cilgavimab）

On the same night , The first covid-19 neutralizing antibody combination therapy drug with independent intellectual property rights in China has obtained the emergency approval of the food and drug administration , By Tengsheng Huachuang Pharmaceutical Technology （ Beijing ） Limited company development , Ambacizumab injection （BRII-196） And romisvir mAb injection （BRII-198） form .

Neutralizing antibody production costs are too high , It doesn't have the conditions for popularization , It can only be applied to some specific scenes and special groups , For example, a group of people with low immunity , Elderly people with underlying diseases , Or breakthrough infection , Or preventive treatment before exposure . More importantly , At present, most neutralizing antibody drugs are right Omicron The mutant is insensitive , It is difficult to show good clinical effect .

Research and development status of covid-19 neutralizing antibody

Covid-19 small molecule drug

1.RNA polymerase inhibitors

In all kinds of RNA Virus genes , The only common genetic product is RNA-dependent-polymerase（RdRp）. Besides , Of the human body RNA Polymerase is not dependent RNA Template RNA Polymerase activity , This avoids targeting viruses RdRp Small molecule drugs interfere with the normal physiological response of host cells . therefore RdRp Become an ideal target of antiviral drugs .

SARS-Cov-2 RdRp Inhibitors act as NTP Competitive substrate , In the virus RNA Under the action of polymerase , Insert into the virus RNA In sequence . Generally speaking , By testing nucleotide analogue inhibitors , You can find RdRp Inhibitors . however , Because of the difference RNA Viral RdRp The structure is significantly different , So many studies have shown that , Existing antiviral drugs that can inhibit other viruses are right SARS-Cov-2 There is no inhibitory effect .

From another point of view , Compared with DNA Viruses ,RNA Viral polymerase has a relatively high polymerization error rate , And lack of proofreading function （proofreading capability）. The high-frequency error rate will bring many mutations to each round of replication of the virus genome , The variability of these viral genomes , In turn, it improves the adaptability of the virus . however , There are also special circumstances , Coronavirus has a correction function 3'-5' Exonuclease （NSP14 ）, It is used to ensure low error rate and high replication fidelity of virus genome .NSP14 Especially important , Because nucleoside analogues should be effectively combined with the viral genome , You need to avoid NSP14 Correction mechanism . The unique exonuclease activity of coronavirus also brings challenges to the research and development of antiviral drugs .

Target selection of small molecule drugs in the life cycle of covid-19

Molnupiravir- Induce high-frequency mutations

2021 year 9 month ,Kabinger Et al. Nat Struct Mol Biol publish an article ：Mechanism of molnupiravir-induced SARS-CoV-2 mutagenesis, Find out Molnupiravir Lead to SARS-Cov-2 RNA The mechanism of high-frequency mutation of products .Molnupiravir The active form of is NHC triphosphate (‘MTP’).SARS-Cov-2 Viruses RdRp You can put NHC As a substrate , Replace cytosine triphosphate nucleotide or uracil triphosphate nucleotide . next , When SARS-Cov-2 Viruses RdRp To blend in MTP Of RNA As a template ,RNA In the template sequence NHC Will mediate G perhaps A Insert a template and pair it , Thus producing highly mutated RNA product , Unable to form functional virus particles . Very lucky ,NHC Be able to escape SARS-Cov-2 The correction effect of exonuclease without being removed .

Molnupiravir Mechanism of action

Molnupiravir By the United States Merck The company cooperates with other companies to develop , Early clinical data show ,Molnupiravir It can reduce the number of hospitalizations and deaths of covid-19 50%, And there was no death in the administration group .2021 year 11 month 4 Number , The British food and Drug Administration approved the world's first covid-19 oral drug Molnupiravir Apply to specific groups .

Molnupiravir clinical data

AT-527- Chain termination

AT-527 It's the United States Atea The company uses its unique purine nucleotide precursor drug platform to develop , stay 2021 year 10 month 9 Number , The company released clinical 2 Period data , Failed to achieve the expected results .

2022 year 2 month ,Ashleigh Shannon Et al. Natrue Communications publish an article ：A dual mechanism of action of AT-527 against SARS-CoV-2 polymerase, The article found AT527 With two targets , stay RdRp and NiRAN The active site has double inhibition , It shows that it is a very potential anti SARS-CoV-2 Small molecule drugs , It can greatly avoid drug resistance .AT527 The active form entering cells is AT-9010, Be able to suppress SARS-CoV-2 replicase/transcriptase Two independent activities of the complex . The first one is , stay RdRp Active site ,AT-9010 Insert into RNA Product chain 3' end , Its chemically modified ribose will prevent NTP To enter , the second AT-9010 Can cause RNA Rapid termination of synthesis . The second kind , And nature NTP Form a competition ,AT-9010 Combine with N-terminal domain of nsp12 （NiRAN） In the active site , act as nsp8 and nsp9 NMPylation Inhibitors , Inhibition NiRAN Nucleotide transferase activity .nsp12 It is a highly conserved gene , It will not change with the emergence of mutations and mutant strains .

AT-527 Have dual targets , Inhibit virus replication

2. Protease inhibitor

SARS-CoV-2 The viral genome contains many structural proteins （ for example Spike protein ）、 Nonstructural proteins （ for example 3- Chymotrypsin like protease （3CL Or major protease Mpro）、 Papain like protease (PLpro)、 Helicase and RNA Dependence RNA Polymerase ） And helper proteins .SARS-Cov-2 Viruses can encode two polypeptides , Then two viral proteases ,PLpro and Mpro, These two polypeptides can be processed , Catalyze the release of themselves and other non structural proteins , Construct viral replication transcription complex . This makes Mpro Become a very attractive drug target . Besides , In different coronaviruses ,Mpro It is highly conservative in structure , There is no homolog in human body , This is designed to target Mpro The new coronase inhibitor provides very favorable conditions .

PF-07321332/PAXLOVID

PF-07321332, It is a covalent inhibitor , Cysteine catalytic residues that can interact directly with protease （Cys145） combination , The success of this drug research and development is still due to Pfizer's precipitation and accumulation in the field of drug research and development for many years . stay 2003 year SARS When it erupts , Pfizer developed for SARS Drugs for viral protease PF-00835231, But because of SARS The rapid disappearance of the epidemic , There is no follow-up clinical study of the drug , Once shelved . After the outbreak of the new crown , Pfizer decided to develop targeted SARS-Cov-2 Protease inhibitors of viruses , So I picked it up again PF-00835231. however , because PF-00835231 It is a small molecule drug of polypeptide , Indicates that it is rich in hydrogen bonds , It has polarity , It cannot be absorbed by the intestines by oral administration . Therefore, Pfizer R & D team has undergone a series of complex chemical modifications , A series of derived compounds were synthesized , Finally selected PF-07321332, And with HIV The antiviral drug ritonavir is used in combination , The combination of the two is called PAXLOVID. Although ritonavir has no anti covid-19 activity , But it can be combined with liver drug enzymes , prevent PF-07321332 It is metabolized by the liver and loses its activity .

2021 year 11 month , Pfizer announced 2/3 The results of phase I test are in line with expectations . Results show , Treat within three days after the symptom occurs ,PAXLOVID It can reduce the hospitalization rate 89%. The drug is effective in 2021 year 12 month 22 It was approved by the US Food and Drug Administration for emergency use . Just a few days ago ,2022 year 2 month 11 It was approved by the China National Drug Administration for import and use of emergency accessories .

Research and development status of new crown small molecule drugs

summary

We will finally defeat the New Champions League , It is necessary to establish a strong immune barrier in the population , It should also have the ability to inhibit the replication of the virus in the body . because mRNA The emergence of Technology , Make a major breakthrough in the speed of vaccine research and development and capacity expansion , In a short time , Rapid development of mRNA The vaccine .mRNA Technology provides an easy opportunity to get on the bus , Capital poured into the track , Spawn many domestic mRNA Startups , What everyone sees is the opportunity to overtake on the curve . It can be seen from the research and development of covid-19 antiviral drugs summarized above , Neutralizing antibodies , In particular, the research and development of small molecule drugs can not be done overnight , It takes a long time to accumulate technology and research and development , Only established pharmaceutical companies in the pharmaceutical research and development industry have the opportunity to compete and overcome . To really solve the threat brought by novel coronavirus , We must develop broad-spectrum and efficient antiviral drugs , It's not easy to go this way , The difficulties , Need to really stand loneliness , People who are willing to spend time studying .

reference ：

1.Monoclonal antibodies for COVID-19 therapy and SARS-CoV-2 detection

2.Current status of therapeutic monoclonal antibodies against SARS-CoV-2

3. New crown vaccine , Neutralizing antibodies , Small molecule oral medicine is an effective combination of anti epidemic , Southwest Securities Research Center

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

5.A dual mechanism of action of AT-527 against SARS-CoV-2 polymerase

6.https://zh.wikipedia.org/wiki/PF-07321332

7.Remdesivir, Molnupiravir and Nirmatrelvir remain active against SARS-CoV-2 Omicron and other variants of concern