Coronavirus-Drug Discovery and Therapeutic Options

COVID-19 is basically a medium size RNA virus and the nucleic acid is about 30 kb long, positive in sense, single stranded and polyadenylated. The RNA which is found in this virus is the largest known RNA and codes for a large polyprotein. In addition, coronaviruses are capable of genetic recombination if 2 viruses infect the same cell at the same time. SARS-CoV emerged first in southern China and rapidly spread around the globe in 2002–2003. In November 2002, an unusual epidemic of atypical pneumonia with a high rate of nosocomial transmission to health-care workers occurred in Foshan, Guangdong, China. In March 2003, a novel CoV was confirmed to be the causative agent for SARS, and was thus named SARS-CoV. Despite the report of a large number of virus-based and host-based treatment options with potent in vitro activities for SARS and MERS, Short Communication Tayyab et al.; JPRI, 33(50A): 154-158, 2021; Article no. JPRI.73208 155 only a few are likely to fulfil their potential in the clinical setting in the foreseeable future. Most drugs have one or more major limitations that prevent them from proceeding beyond the in vitro stage. First, many drugs have high EC50/Cmax ratios at clinically relevant dosages.


INTRODUCTION
The history of corona virus family is very old, it bagan in 1965 when Tyrrell and Bynoe found that there was a virus family who damage the respiratory pathway. This virus was named as B814 at that time. It was transmitted from animals to humans. Now, in 2020 there is a virus COVID-19 which is also belongs to the family of corona virus and infected the whole world. People all around the world facing the situation of the pandemic [1][2][3][4][5][6]. This virus affects the whole world and do not believe in racism.
COVID-19 is basically a medium size RNA virus and the nucleic acid is about 30 kb long, positive in sense, single stranded and polyadenylated. The RNA which is found in this virus is the largest known RNA and codes for a large polyprotein. In addition, coronaviruses are capable of genetic recombination if 2 viruses infect the same cell at the same time.
The most common symptoms of COVID-19 is cold, flu, fever and infection in lungs [7][8][9][10][11][12]. There are different stages in the attacking of this virus [9-15]. At stage one and at the start patient just feel flu and temperature just like common cold and flu. But after seven days it becomes worse and patient feels shortness of breath and dry cough. At advanced stage the patients become also suffered from pneumonia. There is no vaccine and antiviral therapy until now.
In this short communication we will talk about current situation of COVID-19 in Pakistan. It was basically started in China from December 2019, when there was a person who died in Wuhan (a city of China) due to an unknown virus. What started as an epidemic mainly limited to China has now become a truly global pandemic. There have now been over 392,331 confirmed cases and 17,156 deaths, according the John Hopkins University Covid-19 dashboard, which collates information from national and international health authorities. The disease has been detected in more 196 countries and territories, with Italy, the US and Spain experiencing the most widespread outbreaks outside of China. There were 438,441 cases from which 19,650 died and 111,877 were recovered all around the world. The typical coronavirus (CoV) genome is a single-stranded, non-segmented RNA genome, which is approximately 26-32kb. It contains 5ʹ-methylated caps and 3ʹ-polyadenylated tails and is arranged in the order of 5ʹ, replicase genes, genes encoding structural proteins (spike glycoprotein (S), envelope protein (E), membrane protein (M) and nucleocapsid protein (N)), poly adenylated tail and then the 3ʹ end. The partially overlapping 5ʹ-terminal open reading frame 1a/b (ORF1a/b) is within the 5ʹ two-thirds of the CoV genome and encodes the large replicase poly protein 1a (pp1a) and pp1ab.

APPROACHES TO ANTI-CoV DRUG SCREENING
The main two human-pathogenic CoVs known before the SARS pestilence were HCoV-229E and HCoV-OC43, which as a rule because selfconstraining upper respiratory tract contaminations. Along these lines, analysts and examination offices, particularly those associated with antiviral turn of events, were underprepared when SARS-CoV out of nowhere emerged in 2003.
In this manner, three general methodologies were utilized to find potential enemy of CoV treatment alternatives for humanpathogenic CoVs particularly SARS-CoV and the rising MERS-CoV.
The main way to deal with sedate revelation is to test existing wide range antiviral medications that have been utilized to treat other viral diseases by utilizing standard examines that measure the impacts of these medications on the cytopathicity, infection yield and plaque development of live and additionally pseudo composed CoVs. Instances of medications distinguished utilizing this methodology incorporate interferon alfa, interferon beta, interferon gamma, ribavirin and inhibitors of cyclophilin. These medications have the undeniable preferred position of being promptly accessible with known pharmacokinetic and pharmacodynamic properties, symptoms and dosing regimens. Nonetheless, they don't have explicit enemy of CoV impacts and might be related with serious antagonistic impacts. The second enemy of CoV medicate revelation approach includes the screening of substance libraries involving huge quantities of existing mixes or databases that contain data on transcriptional marks in various cell lines. This methodology gives quick, high-throughput screening of numerous promptly accessible aggravates that would then be able to be additionally assessed by hostile to viral tests. Different classes of medications have been distinguished in these medication repurposing programs, including numerous that have significant physiological as well as immunological impacts, for example, those that influence synapse guideline, the estrogen receptor, kinase flagging, lipid or sterol digestion, protein handling and DNA amalgamation or fix.

ADVANCEMENT OF MERS-CoV IMMUNIZATIONS
Quick diagnostics and compelling immunizations are regularly correlative to antiviral treatment in the control of pandemics brought about by developing viruses. In spite of the fact that there has not been any new human SARS case for more than 10 years, inconsistent cases and groups of MERS keep on happening in the Middle East inferable from the diligence of zoonotic sources in endemic territories, and these cases spread to different areas. Powerful MERS-CoV antibodies are basic for intruding on the chain of transmission from creature stores and contaminated people to helpless hosts. Liveconstricted antibodies, which have been recently assessed in creature models for SARS, may be related with dispersed disease in resistant traded off patients. Inactivated antibodies may be related with immunopathology during creature challenge. These are un great methodologies for MERS antibody advancement on the grounds that a considerable extent of patients with serious MERS have comorbidities or fundamental resistant bargaining conditions. Other immunization systems for MERS that utilization DNA plasmids, viral vectors, nanoparticles, infection like particles and recombinant protein subunits are being developed and some have been assessed in creature models. The accessibility of a sheltered and powerful MERS-CoV antibody for dromedary camels and non-invulnerable people at high danger of camel contact in endemic locales, for example, the Middle East and the more prominent Horn of Africa would be a significant measure for controlling the progressing pandemic.
Reasonable creature models are particularly significant for testing hostile to CoV drugs in light of the fact that the vast majority of these medications have not been utilized in people. As opposed to the set number of creature models set up for the mellow diseases brought about by HCoV-229E, HCoV-OC43, HCoV-NL63 and HCoV-HKU1, different little creature and nonhuman primate models have been assessed for investigations of the pathogenesis and treatment of SARS and MERS.

CONCLUSION
Despite the report of a large number of virusbased and host-based treatment options with potent in vitro activities for SARS and MERS, only a few are likely to fulfil their potential in the clinical setting in the foreseeable future. Most medications have at least one significant impediments that keep them from continuing past the in vitro stage. In the first place, numerous medications have high EC50/Cmax proportions at clinically significant measurements. Instances of such medications incorporate cyclosporine, chlorpromazine and interferon alfa. Second, some have extreme symptoms or cause immunosuppression. For instance, the utilization of high-portion ribavirin might be related with haemolytic iron deficiency, neutropenia, teratogenicity and cardiorespiratory trouble. MERSCoV-contaminated basic marmosets rewarded with mycophenolate mofetil built up a deadly disease with significantly higher viral burdens in their lungs and extra aspiratory tissues than untreated controls did128. Operators focusing on have flagging pathways or receptors may instigate immunopathology. Moreover, the absence of a solid medication conveyance strategy in vivo is especially tricky for siRNAs and different operators that have not been recently utilized in people.