During this year, the name of the antiviral drug “Favipiravir” is well-known to us, same as the herbal medicine named Fah-Tha-Lay-Joan or Andrographis extracted, that both of them have been used for the purpose of Covid-19 (SAR-CoV2) treatment. Apart from them, there is also a novel drug for injection for this treatment, remdesivir which is usually the great option of hospitalized patients who have the covid-19 infection in their lungs. Thus, in this chapter, I would like to invite you to see what its action and use for covid-19 patients.
In this section, I would like to introduce you to the drug company which put a lot of effort for making novel drug “Remdesivir” and definitely own its patent, GILEAD SCIENCES.
GILEAD SCIENCES has been established since 1987 under a great vision of researching and producing novel biomedical products into the world commercial market. And now, this company is one of the drug companies that you can find its name “GILD” in the NASDAQ stock market of America.
After thirty years of working hard, GILEAD SCIENCES became famous in many antiviral drugs and cancer drugs. Last several years, the great success has belonged to the new drug “Remdesivir” for world pandemics, COVID-19.
The first thing you should know is that when the focused substances are under experiments, whatever in vitro or in vivo studies, they are called in official code such as AT99999, VZ13579 etc. Later, when they are mass produced to the drug market it will be licensed under generic names such as paracetamol, ibuprofen, propranolol, and also remdesivir. While the trade name or brand name is presented by each pharmaceutical company such as Atripla®, Tecartus™ and Veklury®.
ไวรัสตับอักเสบปัจจุบันมี 5 ชนิด คือ ชนิด A B C D และ E ซึ่งนกขอบอกว่า ตับที่อักเสบจากไวรัส BและC มีเปอร์เซ็นต์เสี่ยงเป็นมะเร็งตับตามมาได้ ฉะนั้นอย่าชะล่าใจต้องเจาะเลือดตรวจหาไวรัสตับอักเสบกันเป็นระยะด้วยนะคะ
Generally, the principle of exploring new drugs is based on chemical reaction. When chemists mix two substances under controlled conditions, some novel substances may appear. The next process is checking its capacity for capturing specific receptors. If it works, it will be produced in large quantities for further in vitro and in vivo studies. Since the enormous expense in novel drug discovery, it is not surprising that there is a legal patent for a new launched drug for 20 years.
Remdesivir (GS-5734) is an inactive form of bulky drugs which is called "monophosphoramidate prodrug". As shown in the below drawing, the bulky blue cloud 🔵 is the phosphate group which will be cut-off when remdesivir is metabolized in the body. The rest is a yellow cloud 🟡 (GS-441524) which is the active form of this drug. This active form can grab onto the RNA polymerase enzyme which plays a role in virus replication. After this enzyme is inhibited, the virus cannot continue to reproduce in the host. Moreover, the structure of remdesivir is most likely the nucleotide, it is grouped as NUCLEOTIDE ANALOG.
Actually, there are many interesting substances that have inhibitory actions against pathogens or germs in vitro studies. But when they come to further study in animals or humans (clinical studies), the results are not the same. Additionally, some novel drugs which have been proven to have the advantages of medical therapy, their serious or uncommon side effects may appear later in a large or specific population.
Remdesivir has tested the antiviral action in three types of virus in the same family, Coronaviruses - MERS-CoV, SARS-CoV and SAR-CoV2 (Covid-19). It is called Coronaviruses because its RNA is a genetic material for propagation. And the other type is EBOLA virus which is classified as a member of the family Filoviruses.
https://nokdinoschool.com/remdesivir/
🧪 เรมเดซิเวียร์กับไวรัส MERS และ SAR-CoV
How does remdesivir work on MERS-CoV and SAR-Cov?
ไวรัสโรค MERS ย่อมาจากคำว่า Middle East Respiratory Syndrome หรือ กลุ่มอาการโรคในระบบทางเดินหายใจตะวันออกกลางค่ะ ที่ได้ชื่อนี้เพราะถูกเรียกตามตำแหน่งที่พบการระบาดครั้งแรกคือ ประเทศซาอุดีอาระเบียนั่นเอง
‘Middle East Respiratory Syndrome’ or MERS is caused by MERS-COV which is related to its first pandemic of this disease in Saudi Arabia. The research is studied in cell culture. Using the human lung epithelial cell line, Calu-3 2B4 to observe what is the IC50 or inhibitory concentration at 50% against MERS-CoV. The IC50 of this drug is 0.03 uM which is interesting because it can infer that remdesivir may have a great potency against this pathogen.
💥 ในงานชิ้นเดียวกันนี้ เขายังทดสอบเพิ่มเติมกับเซลล์เพาะเลี้ยงชนิดอื่น คือ HAE cell โดยนำไวรัสสองชนิด คือ ไวรัสโรค MERS และ ไวรัสโรคซาร์ส / SAR-CoV (ที่เป็นญาติใกล้ชิดกับเชื้อไวรัสโควิด) ไปติดสีโปรตีนที่เรืองแสงฟลูออเรสเซ้นต์สีแดง หรือ Red fluorescent protein (RFP) ไว้ แล้วดูว่า พอให้ยาเรมเดซิเวียร์ที่ความเข้มข้นต่าง ๆ แล้ว ยานี้จะยับยั้งการแบ่งตัวเติบโตของไวรัสได้มากน้อยแค่ไหน คือ จะดูจากความสามารถในการทำให้เซลล์เพาะเลี้ยงที่ติดไวรัสมีจำนวนลดลงไป หรือ หายไปมากน้อยแค่ไหน ผ่านการดูด้วยกล้องฟลูออเรสเซนต์แบบพิเศษ ที่สามารถคำนวณได้ค่ะ ว่าเหลือเซลล์ที่มีการเรืองแสงเพราะติดเชื้อไวรัสอยู่อีกแค่ไหน
Furthermore, the inhibitory action of remdesivir against two coronaviruses (MERS-CoV and SAR-CoV) is studied in another cell ine, HAE cell. By observing the absence of fluorescence of virus-infected cells, it shows the potency of drug action. At the low dose of drug, the fluorescence is much more present that at the higher dose. So, the antiviral action of this drug is dose related.
In addition, SARS-CoV and SAR-CoV2 (Covid-19) are genetically related. More than 79.6% of their nucleotides are identical. Also, lung tissue which plays a critical role in the oxygen exchange cycle is both of their target. So, we named both of them as SAR virus which stands for ‘Severe Acute Respiratory Syndrome’.
When the Ebola Hemorrhagic Fever Outbreaks, it is a huge challenge for medical science. In 2019, there is one interesting research which studied among 681 Ebola virus-infected patients. The patients were randomized into four groups for different treatment.
One of four groups received a 200 mg loading dose of remdesivir, then 100 mg once daily for 9-13 days. You will notice that the loading and maintenance dose of remdesivir in this study is the same as for covid-19 treatment presently.
The remaining three groups are given different antibodies : (1) ZMapp - triple monoclonal antibody (control group) (2) Mab114 - single human monoclonal antibody and (3) REGN-EB3 (mixed IgG1 monoclonal antibodies) to compare the antiviral potency and side-effects.
The quantity of the viral load or remaining virus in the bloodstream can be evaluated throughout this study. As well as the recording of two important enzymes, aminotransferase and serum creatinine level which imply the toxicity of these substances to liver and kidney respectively. The mortality within 28 days was also reported.
Anyways, the conclusion of this study is unsatisfactory. The clinical outcomes of remdesivir for Ebola treatment are not as good as we expected. The mortality rate of remdesivir treatment is higher than that of MAb114 and REGN-EB3. Moreover, the level of liver and kidney enzymes is elevated in remdesivir and ZMapp-treated patients than the rest.
As I said, Remdesivir itself is an inactive form or prodrug, so it has to be changed by metabolic processes in our body. Then, its active form which looks like C-adenosine nucleoside triphosphate - one of the precursors of viral propagation- will appear.
The RNA polymerase is the key enzyme for RNA synthesis that is the critical step for viral replication. One of the components it catches is C-adenosine nucleoside triphosphate. So, when the active forms of remdesivir happen. It will catch this enzyme instead of its true precursor. Finally, the virus can't reproduce in our body anymore.
Apart from that action, Remdesivir may be responsible for the generation of abnormal viruses. Moreover, it may block the entry of SAR-CoV2 into target cells.
ส่วนค่า EC90 (ความเข้มข้นของยาที่จัดการไวรัสได้ถึง 90%) ของยาเรมเดซิเวียร์ในงานวิจัยชิ้นนี้ได้ที่ 1.76 uM ในขณะที่ค่า EC90 ของยาเทียบอย่างคลอโรควินอยู่ที่ 6.90 uM ค่ะ แถมการศึกษานี้ยังทำกับเซลล์เพาะเลี้ยงจากเนื้อเยื่อตับ Huh-7 cells ก็พบว่าให้ผลตอบสนองต่อยาเรมเดซิเวียร์ที่น่าสนใจด้วยค่ะ
ดังนั้น จากงานวิจัยนี้ แสดงถึงฤทธิ์ของเรมเดซิเวียร์ต่อเชื้อโควิดในเซลล์เพาะเลี้ยง in vitro ที่ดีมากทีเดียวค่ะ (อ่านเปเปอร์)
There is a cell culture experiment with the Vero E6 cell line for finding out the Effective Concentration 50% (EC50) of remdesivir against SAR-CoV2. Chloroquine is the broad spectrum of antiviral drugs, so it is used to be the comparable standard in this experiment. The EC50 of this drug is 0.77 whereas that of Chloroquine is 1.13 uM. The lower concentration refers to the greater potency. So, it is interesting that remdesivir has effective potency to block the SAR-CoV2 propagation.
As well as the concentration of EC90, remdesivir is 1.76 uM which is much lower than 6.90 uM in Chloroquine-testing. The results of an in vitro experiment handled in the liver cell line, Huh-7 cells are shown the same way.(Read more)
Here is an interesting study observed in hospitalized patients who had been diagnosed with covid-19 infected lung. They were treated with the first 200 mg-loading dose of remdesivir, then followed by a 100 mg-maintenance dose until 10 days. The percentage of saturated oxygen and patients symptoms were all recorded. The data were collected until 36 completed days after the starting date. Then, they were evaluated at the end of this cohort study.
Sixty-eight percent of 53 patients showed great improvement during their treatment whether they were invasive or non-invasive. Remdesivir was entirely effective among all three age divided groups of <50 years’ group, 50-7- years’ group and >70 years' group. Anyways, seven patients (13%), six of them were invasive cases, died. (Read more)
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🧑 ใครควรใช้ Remdesivir ?
Who should be treated with remdesivir for the treatment of Covid-19?
*ใช้ตามแนวทางของ IDSA - Infectious Diseases Society of America) และ US-NIH - สถาบันสุขภาพแห่งชาติสหรัฐ / The National Institutes of Health
It is recommended to use remdesivir in people aged more than 12 years old. The weight of patients should be more than 40 kilograms. And it should be the second option for patients who can’t be treated with favipiravir. Remdesivir is also suggested to use for severe cases of covid-19 patients who have to be hospitalized with ECMO equipment.
The remdesivir dose should be adjusted according to the weight of children under 12 years old. The initial loading dose is 5 mg/kg once daily followed by 2.5 mg/kg once a day thereafter.
The route of administration for Remdesivir is intravenous injection (i.v.). Each vial contains 100 mg Remdesivir as the active ingredient. A captisol is added to the formulation in order to increase the solubility also.
Hospitalized Covid-19 patients should receive remdesivir 100 mg once daily for at least 5 days, after a loading dose of double the maintenance dose on day 1. For the patients using the ECMO machine, they should be treated with remdesivir for 10 days continuously.
Actually, this point is the highlight of using remdesivir. Because the use of favipiravir is not much evidence that it is safe for pregnant women and unborn children when compared to that of remdesivir. So, it is suggested to treat pregnant mothers infected with SAR-CoV2 in her lungs with remdesivir. No matter how many months pregnant.
But at an early stage of pregnancy (1-3 months) with mild symptoms of Covid-19 pathology, remdesivir is not necessary. In the second trimester of pregnancy with moderate infection of SAR-CoV2, physicians should weigh the risk and benefit for each patient cautiously.
From many studies, Remdesivir itself is not harmful to the liver and kidney. It differs from favipiravir,the first line drug for Covid-19 treatment. The dose of favipiravir should be adjusted in patients with liver problems. Remdesivir should be avoided in patients with glomerular filtration rate (GFR) less than 30 ml/minute. (The normal rate of GFR should be 95-125 ml/min)
Remdesivir is metabolized by hydrolases, then broken down and eliminated from the body in hours. It doesn’t take long to get rid of this drug. So, it is safer to use in patients who have liver disease when compared to favipiravir. Anyways, it should be avoided in patients with alanine transaminase (liver enzyme which indicates the level of liver damage) much more than 5 times of normal level. (The normal range of ALT is 0 - 48 U/L.) (Read more)
Some side effects of remdesivir are reported such as nausea, vomiting, constipation and hypotension. However, there are more potential advantages when compared to these side effects. (Read more)
Even though the efficacy of remdesivir is very interesting, it is not the first choice in all cases of SAR-CoV2 infection. Nowaday we have favipiravir which is cheaper and easier to use. The cost of each favipiravir tablet is 120-150 Thai baht, whereas that of remdesivir is more than 3000 Thai baht per single-dose vial.
Actually,we have to take more than 50 tablets of favipiravir in one course of treatment. So the overall payment must be at least 6,000-7,500 Thai baht. Whereas the 5-10 day-course of remdesivir is more expensive, we have to pay about 20,000 Thai baht or more. Besides that, many people have limited reimbursements for their medical expenses. So, remdesivir will be used in a specific case that matches the certain criteria.