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Joint Replacement Infection Antibiotics

Joint replacement surgery is a common approach to treating severe joint pain or dysfunction that does not respond to less invasive therapy. Successful surgery offers improved quality of life with decreased pain and improved mobility. However, this treatment also comes with the risk of joint infection, and treatment of such an infection may not be straightforward.

New antibiotics and new combinations of antibiotics are necessary to deal with the antibiotic resistance that bacteria develop over time.

Lab Imitation of Joint Replacement

A study to mimic a joint replacement followed by infection has been carried out. In the animal lab, Wistar rats were implanted with a rod into the thigh bone. The rod was made of sterile steel and was infected with a bacterial suspension before being implanted. Two different kinds of bacteria suspension were tested.

Antibiotics Treatments Attempted

Treatment with antibiotics started seven days after the surgery. The antibiotics that were tested individually include linezolid, vancomycin, rifampin, and cotrimoxazole. A few antibiotic combinations were also tested: 1. rifampin + linezolid, 2. rifampin + vancomycin, and 3. rifampin + cotrimoxazole. After 23 days, the implants were removed, and the bacterial counts of the implant and surrounding tissues examined.

Joint Infection Under Control

In this study, rifampin is the only antibiotic to significantly reduce the bacterial infection on its own. However, it is already known that monotherapy using rifampin is not a good option. Previous studies found frequent development of resistance to treatment when only rifampin is used. An effective treatment needs to also prevent these resistance mechanisms from forming or evolving.

As it turns out, the combination antibiotic treatments used in this study were also found to be effective. And in addition, the combination treatment significantly reduced the development of resistance.

A Real Concern

Infection after joint replacement surgery is rare for a first-time surgery. However, if repeated surgeries are required, the risk of infection is significant. And since replaced joints typically last only 10-25 years, many people eventually require a second and third or more replacement surgeries. Therefore, it is important to determine an effective method of treatment for this type of infection.

Goetz J, Keyssner V, Hanses F, et al. Animal experimental investigation on the efficacy of antibiotic therapy with linezolid, vancomycin, cotrimoxazole, and rifampin in treatment of periprosthetic knee joint infections by MSRA. Bone Joint Res. 2022 Mar;11(3):143-151. doi:10.1302/2046-3758. PMID: 35227086

Verubecestat and Alzheimer’s Disease Prevention

Verubecestat is a BACE1 protein inhibitor that can prevent amyloid beta (Aβ) production and aggregation as found in Alzheimer’s disease. Development of treatments using BACE inhibitors have failed because of unacceptable level of side-effects. However, most of the clinical trials have focused on the late-stage disease, rather than prevention. But while inhibition of BACE prevents the formation of Aβ aggregates, it does not effectively break up already existing aggregates. Therefore, this kind of treatment may be more effective in the early stages of Alzheimer’s.

Mouse Modeling of Alzheimer’s

A recent study used a 5XFAD mouse model, a well-developed model of Alzheimer’s pathology, which develops significant Aβ plaque formation. Before the onset of symptoms, the mice were fed with a diet containing verubecestat for 3 months, while symptoms were expected to be increasing.

The results in the 5XFAD model were good. The free Aβ found in the plasma was reduced, and therefore not available to begin forming aggregates. This treatment was shown to be dose-dependent. The higher-dosed animals still experienced the negative side-effects. By carefully developing a dosing regimen, it may be possible to treat the disease while also avoiding the side-effects.

Developing a Better Mouse Model

One problem when using a mouse model to study this disease is that the physiological effects may be over-exaggerated. That makes it difficult to determine whether a treatment may or may not actually be effective against the real disease. Another recent study attempted to address this issue by developing more specific mouse models. Therefore, an App knock-in model was developed, AppG-F, which is a closer resemblance to the disease’s pathophysiology seen in humans.

Treatment of the AppG-F mice with verubecestat significantly reduced the Aβ, much more effectively than with previous mouse models. Therefore a lower dose may successfully inhibit the disease development while causing less side-effects than previously experienced with larger doses. This new model is more compatible with studies focusing on BACE inhibitors.

Change of Strategy

Alzheimer’s disease is the most common form of dementia. There are no treatments to reverse the effects yet, and developing a preventive treatment may be a more effective strategy for this particular disease. Verubecestat is just one of many BACE inhibitors that are worth investigating further.

 

Oblak A, Cope Z, Quinney S, et al. Prophylactic evaluation of verubecestat on disease-and symptom-modifying effects in 5XFAD mice. Alzheimers Dement (N Y). 2022 Jul 14;8(1):e12317. doi: 10.1002/trc2.12317. PMID: 35846156

Watamura N, Sato K, Shiihashi G, et al. An isogenic panel of App knock-in mouse models: profiling β-secretase inhibition and endosomal abnormalities. Sci Adv. 2022 Jun 10;8(23):eabm6155. doi: 10.1126/sciadv.abm6155. PMID: 35675411

 

Sotorasib, Adagrasib and Genetic Mutations

Background

Sotorasib and adagrasib are two new compounds that can help us to understand the mechanisms of KRAS mutations. Mutated forms of the gene KRAS encourage cell proliferation and are involved in a large fraction of all cancers. Although this gene was discovered in the 1980s, scientists have long struggled to find chemotherapies that target it. That’s because of a lack of binding sites. The new drugs sotorasib and adagrasib can bind to and inhibit one kind of mutated KRAS. Sotorasib has been approved for the treatment of non-small-cell lung cancer and adagrasib is in clinical trials.

Non-small-cell lung cancer has a history of developing resistance to drug treatments. So, it’s likely that patients may suffer resistance when sotorasib and adagrasib enter clinical use. Recently, a team of cancer researchers sought to understand resistance to these new drugs, to improve strategies to prevent it.

Experimental

The researchers exposed a cell culture line of non-small-cell lung cancer to sotorasib or adagrasib, with added N-ethyl-N-nitrosurea to encourage mutations. Then they analyzed the KRAS mutations that resulted. Five of the mutations were resistant to one drug but not the other. Therefore, sequential treatment with these drugs might help patients with this kind of resistance. Two of the KRAS mutations that emerged were resistant to both drugs. A cocktail of BI-3406 and trametinib inhibits cells with this mutation, so this cocktail might help patients who have this kind of resistance.

The mutations found in this study are not exhaustive of all the KRAS mutations. Additional mutations may appear when patients are treated with these chemicals. However, this study made good progress toward understanding the mechanisms behind KRAS chemotherapy resistance.

Koga T, Suda K, Fujino T, et al. KRAS secondary mutations that confer acquired resistance to KRAS G12C inhibitors, sotorasib and adagrasib, and overcoming strategies: insights from in vitro experiments. Journal of Thoracic Oncology. 2021 Aug;16(8):1321-1332. PMID: 33971321. doi: 10.1016/j.jtho.2021.04.015

 

Azo Dye Pollution

Azo dyes are one group of major pollutants found worldwide. Wastewater containing these dyes from the textile industry are notoriously difficult to treat. Furthermore, azo dyes make up approximately 50% of all dyes produced worldwide and are the largest class of synthetic dyes. So far, biological treatment methods are among the most promising remediation methods. Consequently, search for new species of actinobacteria capable of either biodegrading or bioabsorping azo dyes in a marine environment has been intense.

Breaking down azo dyes

A variety of microorganisms including fungi and algae have been studied and, so far, bacteria have had the most success. Bacteria use both aerobic and anaerobic pathways in processing these materials. For example, the metabolic pathway of a thermophilic bacterial strain Anoxybacillus sp. PDR2 in degrading the dye material Direct Black G has been determined using bioinformatics analysis.

Reassessing the treated waste material

Follow-up analysis of the degraded material was done using phytotoxicity studies. Germination rates of rice and mung bean seeds, known to be sensitive to environmental hazards, were tested and it was discovered that the toxicity of the treated wastewater was greatly reduced as compared to the original azo-containing wastewater. Similarly, additional test results have been produced using other bacteria and azo-dye combinations.

Waste becomes fuel

And why stop there? Even more useful biological methods may exist that can not only break down the azo dyes to less toxic substances, but also produce oils to be used as biofuels. In this way, a waste product from one industry may be used as a feedstock for production of useful product in another industry. Recently, an oil-producing enzyme found in wood-feeding termites has been explored for the additional capability of breaking down azo dyes. Subsequently, a detailed dual-process biological pathway fulfilling both objectives has been proposed.

Further research remains to find a solution to combat all of the negative impacts on human health and the environment caused by azo dye wastewater. At any rate, coupling a waste remediation process to a production process of a useful and desired product would be an ideal goal to achieve.

Chen G, An X, Li H, et al. Detoxification of azo dye Direct Black G by thermophilic Anoxybacillus sp. PDR2 and its application potential in bioremediation. Ecotoxicol Environ Saf. 2021 May;214:112084. doi: 10.1016/j.ecoenv.2921.112084. PMID: 33640726

Chittal V, Gracias M, Anu A, et al. Biodecolorization and biodegradation of azo dye Reactive Orange-16 by marine Nocardiopsis sp. Iran J Biotechnol. 2019 Sep 1;17(3):e1551. doi: 10.29252/ijb.1551. PMID: 32195279

Ali S, Al-Tohamy R, Koutra E, et al. Coupling azo dye degradation and biodiesel production by manganese-dependent peroxidase producing oleaginous yeasts isolated from wood-feeding termite gut symbionts. Biotechnol Biofuels. 2021 Mar 8;14(1):61. doi: 10.1186/s13068-021-01906-0. PMID: 33685508

 

 

Telacebec, an Emerging Antibiotic

Telacebec is an emerging antibiotic. It’s part of a new class of antibiotics that disrupt the electron transport chain, which could be used to treat drug-resistant tuberculosis. Telacebec also has the potential to treat diseases closely related to tuberculosis, such as leprosy and Buruli ulcer. The Buruli ulcer pathogen, Mycobacterium ulcerans, is especially sensitive to telacebec.

Buruli Ulcer

Buruli ulcer is a neglected tropical disease that causes open wounds on the arms and legs. The standard of care is an eight-week-long course of antibiotics, which is difficult to give in resource-poor settings. Recently, a research team wanted to see if telacebec could be used as a shorter treatment.

Experimental Model

They infected mouse footpads with Mycobacterium ulcerans, then gave the mice a range of doses of telacebec. These treatments were more effective than standard antibiotics, and cleared infection after five days of treatment, or even in some cases after a single dose.

Mouse footpads continued to improve even after the treatment was stopped. We know that Mycobacterium ulcerans knocks down the immune system in infected limbs. Telacebec treatment might restore the immune system, which then clears the infection. To test this hypothesis, the researchers repeated their experiment in immunocompromised mice. These mice didn’t respond to treatment as well as normal mice.

A Word of Caution

Telacebec shows great promise for improving the treatment of Buruli ulcer, but short course, monotherapy treatments such as this one risk causing antibiotic resistance. Furthermore, doctors should use extra care with immunocompromised patients, such as people with HIV. For these people it might be safer to use a longer course of treatment or to use telacebec as part of an antibiotic cocktail.

Komm O, Almeida DV, Converse PJ, et al. Impact of dose, duration, and immune status on efficacy of ultrashort telacebec regimens in mouse models of Buruli ulcer. Antimicrobial Agents Chemotherapy. 2021 Oct 18,65(11):e0141821. doi: 10.1128/AAC.01418-21  PMID: 34460302

Panobinostat on Ovarian Cancer

Ovarian cancer often grows undetected into the advanced disease stages and because of this the mortality rate is relatively high. Even after using the available treatments, relapse is quite common. Recent studies of several cancers have shown positive impacts when treated with HDAC inhibitors, and even more powerful impacts when treated with an HDAC inhibitor paired with other types of inhibitors.

Cell Study

A recent study on ovarian cancer cells paired HDAC inhibitor panobinostat (LBH-589) with autophagy inhibitor chloroquine or bafilomycin A1. Together they cause DNA strand breaks and inhibit the cell’s ability to repair those breaks. The combination treatment was more powerful than the individual treatments. Discovering synergistic drug combinations such as these is the cornerstone of cancer therapy.

Animal Study

In another study, panobinostat was paired with PARP inhibitor olaparib. Mice with epithelial ovarian cancer cells were divided into 4 groups and each group subjected to one set of treatment: vehicle, panobinostat, olaparib, or panobinostat + olaparib. It was discovered that PARP inhibitors and HDAC inhibitors synergize well against HR-proficient ovarian cancer. This is exciting because HR-proficient type has proven less responsive to the developed treatments than HR-deficient type, which is more common. The overall tumor burden in the mice treated with panobinostat + olaparib was reduced. Also, there was reduced tumor proliferation and increased DNA damage observed in the harvested tumors.

Using the dual mechanisms of an HDAC inhibitor combined with another type of inhibitor is found to have a synergistic effect in many instances. The rational combination of drugs to target both cytotoxic effects and immune-modulating effects at the same time increases the potential to overcome drug resistance. This is especially important in fighting cancers such as ovarian cancer that have high mortality rates.

 

Ovejero-Sanchez M, Gonzalez-Sarmiento R, Herrero AB. Synergistic effect of chloroquine and panobinostat in ovarian cancer through induction of DNA damage and inhibition of DNA repair. Neoplasia. 2021 May;23(5):515-528. doi: 10.1016/j.neo.2021.04.003. PMID: 33930758

Wilson A, Gupta V, Liu Q, et al. Panobinostat enhances olaparib efficacy by modifying expression of homologous recombination repair and immune transcripts in ovarian cancer. Neoplasia. 2022 Feb;24(2):63-75. doi: 10.1016/j.neo.2021.12.002. PMID: 34933276

Beclomethasone Dipropionate and Asthma

Beclomethasone dipropionate is a corticosteroid. In its active form, 17-beclomethasone monopropionate, it binds to glucocorticoid receptors and reduces inflammation. Because of its anti-inflammatory properties, inhaled beclomethasone dipropionate is used to treat asthma and chronic obstructive pulmonary disorder. In Europe, it is used in a drug cocktail with formoterol fumarate, a bronchodilator, and glycopyrronium bromide, which reduces bronchial secretions.

A team of European researchers wanted to confirm whether this drug cocktail reaches the peripheral lungs. If so, there is a much higher chance that it can effectively treat asthma. The researchers recruited ten healthy people and nine people with asthma for a clinical trial. The trial participants first inhaled a drug cocktail that was labelled with technetium-99 (tek-nē-shē-əm).  Then their lungs were imaged using gamma scintigraphy. The study found that about 25% of the inhaled drug was deposited in the lungs, and half of that made it into the peripheral lungs.

There was no significant difference in drug deposition between healthy people and people with asthma. As such, these results are encouraging. It suggests that the beclomethasone dipropionate/formoterol fumarate/glycopyrronium bromide cocktail gets delivered correctly for people with asthma.

 

Usmani S, Baldi S, Warren S, et al. Lung deposition of inhaled extrafine beclomethasone dipropionate/formoterol fumarate/glycopyrronium bromide in healthy volunteers and asthma: the STORM study. J Aerosol Med Pulm Drug Deliv. 2022 Aug;35(4):179-185. doi: 10.1089/jamp.2021.0046. PMID: 35128939

 

Nirmatrelvir Against SARS-CoV-2 Mutants

SARS-CoV-2 continues to cause death and illness across the world. We need both vaccines and an arsenal of antiviral drugs to combat this virus.

One drug that was recently developed to treat SARS-CoV-2 is nirmatrelvir. Nirmatrelvir targets the main protease (Mpro) of SARS-CoV-2, which it needs to replicate. This molecule binds to the active site of Mpro and permanently alters it.

A recent study by Ullrich et al. sought to test whether nirmatrelvir still works when SARS-CoV-2 accumulates mutations in its Mpro. Epidemiologists have identified many mutations in this protease, so Ullrich et al. chose a selection of the most common mutations to study. They expressed mutant copies of Mpro and measured their proteolytic activity. The mutant Mpro has similar activity to wild-type.

Next, the researchers added nirmatrelvir to the mutant Mpro and calculated its inhibitory concentration. Nirmatrelvir inhibitory concentration against the mutant Mpro was similar to the wild-type.

This encouraging result suggests that nirmatrelvir will continue to work against SARS-CoV-2 in the near future, even if the virus mutates. However, in the long term we should consider developing drug cocktails to prevent resistance from evolving.

 

Ullrich S, Ekanayake KB, Otting G, Nitsche C. Main protease mutants of SARS-CoV-2 variants remain susceptible to nirmatrelvir. Bioorg Med Chem Lett. 2022 Apr 15;62:128629. doi.org/10.1016/j.bmcl.2022.128629. PMID: 35182772

Vitamin K Metabolic Engineering

Vitamin K is a class of fat-soluble molecules that are required for blood clotting and calcium binding in the human body. Although acute vitamin K deficiency is rare, there is evidence that subclinical deficiency raises the risk of heart disease and osteoporosis. The menaquinones (vitamin K2) are an especially good dietary source of vitamin K because of their bioavailability and stability. Menaquinones can be found in fermented foods such as natto and dairy.

A team of researchers at the Norwegian University of Life Sciences wanted to enhance the menaquinone content of dairy to increase its functional value. To achieve this goal, they planned to genetically engineer a lactobacterium, Lactococcus lactis, that is involved in making yogurt. L. lactis contains a biosynthetic pathway to produce several menaquinones, especially menaquinone-9. The researchers tried overexpressing the genes in that pathway. Overexpression of some genes (menF, menA) caused L. lactis to produce extra menaquinone-3, instead of the more desirable menaquinone-9. The overexpression of other genes (mvk, llmg_0196) led to increased production of menaquinone-9.

When the engineered L. lactis was used to culture milk, the yogurt had enhanced levels of menaquinone-9. The researchers calculate that moderate intake of such yogurt would help many people get optimal vitamin K in their diet. This encouraging result suggests that engineered bacteria can be used more broadly to enhance nutrition.

Boe C, Holo H. Engineering Lactococcus lactis for increased vitamin K2 production. Front Bioeng Biotechnol. 2020 Mar 18;8:191. PMID: 32258010. doi: 10.3389/fbioe.2020.00191

 

Mayaro Virus Antiviral EIDD-1931

Mayaro virus is a mosquito-borne virus endemic to forests in South America. It causes acute illness with fever, headache, rash, and long-lasting joint pain. Mayaro’s range could spread in the future because of climate change. No vaccines or antiviral drugs are currently available although there are some candidates under development.

Therefore, a concerned team of scientists from the Rega Institute for Medical Researchin Belgium wanted to do exploratory research on antivirals that might treat this disease. They chose a panel of molecules that are known to treat other mosquito-borne viruses, some of which block early stages of the virus life cycle (arbidol, chloroquine, suramin, and ribavirin), and some that inhibit virus genome replication (favipiravir, 7DMA, 2’CMC, EIDD-1931, galidesivir and remdesivir).

They then applied these selected molecules to a model of cell culture that was infected with Mayaro virus. The researchers measured the 50% effective concentration, or the amount of molecule that inhibits 50% of the virus infectivity. They optimized the antiviral screening assay to be reproducible and reliable.

The assay described in this paper can be useful to test future antiviral drugs against this virus. Furthermore, the three molecules that performed well in cell culture are worth further study with in vivo models. Although the range of Mayaro virus is limited for now, we should study it and other neglected diseases to proactively prevent suffering in the future.

 

Langendries L, Abdelnabi R, Neyts J, Delang L. Repurposing drugs for Mayaro virus: identification of EIDD-1931, Favipiravir, and Suramin as Mayaro virus inhibitors. Microorganisms. 2021 Mar 31;9(4):734. PMID: 33807492

Artificial Sweetener Mogroside V

Artificial sweetener Mogroside V is a major component of S. grosvenorri, or monkfruit. Extracts from this fruit enjoy increasing popularity as artificial sweeteners. What effect does mogroside V have on the gut microbiome? Some preliminary evidence suggests that it is a prebiotic, or food for gut bacteria, so a team of researchers from South China University of Technology sought to clarify its effects.

The team incubated gut bacteria in a nutrient broth containing mogroside V for twenty-four hours. Then, they analyzed both the broth and the sediment using UPLC. The amount of mogroside V decreased and the amount of secondary metabolites increased, including mogroside I, mogroside II, mogroside III, and mogrol, suggesting that the gut bacteria had been metabolizing the mogroside V.

They then incubated gut bacterial cultures with and without added mogroside V and measured the microbial species composition. In the cultures with added mogroside V, the prevalance of actinomycetes and bacteriodetes increased, and the prevalence of proteobacteria and firmicutes decreased. These changes in gut bacterial composition might be beneficial to human health.

The artificial sweetener Mogroside V has potential as a prebiotic to improve gut health.

 

Xiao R, Liao W, Luo G. et al. Modulation of gut microbiota composition and short-chain fatty acid synthesis by mogroside V in an in vitro incubation system. ACS Omega. 2021 Sep 21;6(39):25486-25496. PMID: 34632206

HT-2 Toxin Disruption of Cartilage Development

Kashin-Beck disease is a bone and cartilage disease found in Siberia, North Korea, and northeast China. Patients suffer from short stature, malformed joints, and pain. The cause of the disease is unclear, but it is thought to be an interaction between genes and environmental factors such as selenium deficiency and mycotoxins from grains grown in the region.

T2 toxin, a mycotoxin, has already been identified as a risk factor for Kashin-Beck disease. What of Ht-2 toxin, one of its metabolites? A team of researchers from the Xi’an School of Public Health, China, wanted to know if HT-2 toxin disrupts the development of cartilage.

They used HiPSCs (human induced pluripotent stem cells) to build a model of Kashin-Beck disease. HiPSC cells with a Kashin-Beck genetic background were differentiated into chondrocytes. HT-2 toxin was toxic to these cells: microscopy found that treatment caused microtubules, mitochondria, and endoplasmic reticulum to be disordered. The cell cycle regulation, including p53, p21, and CDK6, had disrupted expression.

This study confirms that HT-2 toxin is a direct risk factor for Kashin-Beck disease. The results also suggest a mechanism for how HT-2 toxin and T-2 toxin contribute to this disease. HT-2 toxin disrupted the cell cycle, which inhibited chondrocytes from differentiating into mature cartilage. This disruption in growth could cause cartilage malformation in people.

 

Zhang Y, Liu H, Lin X, et al. Dysregulation of cells cycle and apoptosis in human induced pluripotent stem cells chondrocytes through p53 pathway by HT-2 toxin: an in vitro study. Frontiers in Genetics. 2021 Aug 4;12:677723. PMID: 34421989. doi: 10.3389/fgene.2021.677723.

Gut Peptides

Gut peptides are hormones secreted by the gut that act on the brain to regulate digestion and appetite. The function of gut peptides is a promising area of research for the treatment of type-2 diabetes and obesity.

Background

In the last ten years, glucagon-like peptide (GLP-1) agonists have reached clinical use to treat type-2 diabetes. This class of drugs can cause side effects such as nausea and vomiting, so the maximum tolerable dose is limited. A combination of gut peptide agonists might allow better patient outcomes at lower doses of each drug.

New Studies Using Combination

Recently, a team of researchers sought to understand the effects of combining a GLP-1 agonist with a cholecystokinin (CCK) agonist. They gave mice a GLP-1 agonist and a CCK agonist by injection and measured the mice’s food intake in the short and the long term. Mice on the GLP-1/CCK1 agonist combination ate less and lost more body weight than mice on either agonist alone. The researchers also tested the effect of the GLP-1/CCK1 agonist combination on mice that had become obese by eating a high-fat diet. The obese mice had a similar but smaller response.

Impact on Brain

The researchers wanted to know what effect the agonist combination had on the mouse brain. They immunostained mouse brains for a marker of brain metabolic activity and found that activity was stimulated the most in the nucleus solitary tract, a part of the brain stem.

They did a further test for neuron RNA expression. Neurons that were activated by the GLP-1/CCK1 agonist combination had increased expression of a receptor for calcitonin gene-related peptide (CGRP). Neurons that were inhibited by the GLP-1/CCK1 agonist combination had increased expression of a receptor for pituitary adenylate cyclase-activating peptide (PACAP). The results of these studies suggest that CGRP and PACAP are themselves worth studying for their effects on type-2 diabetes and obesity.

 

Glucagon, Exendin, PACAP and Related Peptides

Calcitonin and Related Peptides

Cholecystokinin (CCK)   S3351

 

Roth E, Benoit S, Quentin B, et al. Behavioral and neurochemical mechanisms underpinning the feeding-suppressive effect of GLP-1/CCK combinatorial therapy. Molecular Metabolism. 2021 Jan;43:101118. PMID: 33221554 doi.org/10.1016/j.molmet.2020.101118

 

Molnupiravir Against COVID-19

Molnupiravir is an antiviral drug that has recently been approved by the FDA for the treatment of COVID-19. This drug is especially exciting because it is the first approved COVID-19 drug that can be taken as a pill, and also because it reduces the risk of hospitalization and death by 30%. Two recent research papers give us insight into the molecular biology of how molnupiravir works.

In order to reproduce, the virus SARS-CoV-2 needs to synthesize RNA. Usually, the enzyme it uses to do this, RNA-dependent RNA polymerase (RdRp), is an attractive target for makers of antiviral drugs. At present, many antiviral drugs block RdRp by mimicking RNA nucleotides. When such a drug gets incorporated into a new RNA strand, synthesis stops. Unfortunately, this drug strategy is not effective against SARS-CoV-2 because it has proofreading enzymes that allow synthesis to continue.

Two research teams in Germany and Canada recently showed that molnupiravir mimics cytidine and uridine, two RNA nucleotides. Molnupiravir incorporates into new RNA strands, like other antiviral drugs. But interestingly, RdRp continues to synthesize RNA. How, then, does molnupiravir prevent severe COVID-19?

Both teams addressed this question by combining RNA that contained molnupiravir with RdRp in vitro. They found that when RdRp uses this RNA to synthesize new RNA, molnupiravir causes mutations. After several generations, mutations build up to a lethal level and the virus can no longer reproduce.

Molnupiravir’s mechanism of action evades viral proofreading enzymes. Because of this, it may also find use in treating a broad variety of other viruses that also have these enzymes.

 

Kabinger F, Stiller C, Schmitzova J, et al. Mechanism of molnupiravir-induced SARS-CoV-2 mutagenesis. Nature Structural & Molecular Biology. 2021 Sep;28(9):740-746. PMID: 34381216

Gordon CJ, Tchesnokov EP, Schinazi RF, et al. Molnupiravir promotes SARS-CoV-2 mutagenesis via the RNA template. Journal of Biological Chemistry. 2021 Jul;297(1):100770. PMID: 33989635

FDA News Release: FDA authorizes additional oral antiviral for treatment of COVID-19 in certain adults

Fidaxomicin as a New Antibiotic Template

Fidaxomicin is a narrow-spectrum antibiotic that is specific against gram-positive bacteria. Furthermore, it is not well absorbed into the bloodstream, so it remains in the gut. Both these characteristics make it a useful drug to treat Clostridioides difficile infections. It has been in clinical use since 2011.

Fidaxomicin-resistant C. difficile is currently rare, but antibiotic resistance is always a concern. A team of scientists at the University of Zurich, Switzerland wanted to use fidaxomicin as a template to develop new antibiotics before more resistant strains evolve.

They used a rational design approach, starting with the cryo-EM structure of fidaxomicin bound to bacterial RNA polymerase. Fidaxomicin has two carbohydrates attached to it, a noviose and a rhamnose. Based on the cryo-EM structure, the C3″ on the noviose looked like a promising place to add new functional groups. The team made thirty derivatives of fidaxomicin by changing the functional groups on that carbon.

They tested the antibiotic activity of these derivatives by measuring their minimal inhibitory concentration against C. difficile. Many of the derivatives still showed antibiotic activity. Although the derivatives were not any more effective against C. difficile than fidaxomicin, this experiment is an encouraging proof of concept for the rational design of new antibiotics.

 

Dailler D, Dorst A, Schafle D, et al. Novel fidaxomicin antibiotics through site-selective catalysis. Communications Chemistry. 2021. 4:59.  doi.org/10.1038/s42004-021-00501-6.

Astaxanthin Antitumor Effect

Astaxanthin is a natural pigment that makes many sea creatures red, such as shrimp and crabs. It has many commercial uses such as a food coloring and an animal feed supplement, and it is an antioxidant. Previous research has found that astaxanthin has an antitumor effect.

Glioblastoma is a type of brain cancer with an especially poor prognosis. It is difficult to treat because most cancer drugs can’t cross the blood-brain barrier to reach the brain tumor. Some natural products such as curcumin can cross the blood-brain barrier. Recently, a team of scientists in Japan set out to test whether astaxanthin can cross the blood-brain barrier and whether it can act against glioblastoma tumors.

First, the researchers added astaxanthin to a cell culture line of mouse glioblastoma cells. They found that the cells had reduced proliferation and migration, both of which are needed for tumors to spread.

Then they fed astaxanthin to mice and were able to detect it in mouse brains, suggesting that astaxnthin can cross the blood-brain barrier. The researchers fed astaxanthin to mice with a model of glioblastoma and the tumor growth was notably inhibited.

Astaxanthin may inhibit glioblastoma growth because it is an antioxidant. Antioxidants can affect the cell signals that control growth and division. The antitumor effect of astaxanthin in this experiment was modest, but astaxanthin is worth researching in combination with other promising glioblastoma drugs.

 

Tsuji S, Nakamura S, Maoka T, et al. Antitumor effects of astaxanthin and adonixanthin on glioblastoma. Marine Drugs. 2020 Sep 18;18(9):474. doi:10.3390/md18090474. PMID: 32962073.

Protease Inhibitors: Saquinavir and Boceprevir

The COVID-19 pandemic continues to cause death and severe illness around the world. As many countries still experience vaccine shortages and the virus evolves to be more contagious, we need to develop better treatments for this disease.

A Possible Target:

The SARS-CoV2 main protease (Mpro) is an attractive target for drug treatment. The coronavirus needs this protease to process its proteins, an important step in its life cycle. Protease inhibitors are already in clinical use to treat other viral infections, such as HIV and hepatitis C. Repurposed existing drugs can get approval to treat disease faster than new drugs because their safety and pharmacokinetics are already known. Can we repurpose known protease inhibitors to treat SARS-CoV2 infection?

Two recent scientific studies address this question.

Docking and Molecular Dynamics Simulations:

Bello et al. built a computer model of Mpro and twelve promising protease inhibitors: darunavir, indinavir, saquinavir, tipranavir, diosmin, hesperidin, rutin, raltegravir, velpatasvir, ledipasvir, rosuvastatin, and bortezomib. The model predicts that of the twelve, saquinavir should bind to Mpro the best. Interestingly, saquinavir has long been used as part of drug cocktails to treat HIV. Although a computer study is limited, saquinavir is worth following up in vitro.

Enzyme Assays:

Another team of researchers, Ma et al., used an enzyme assay to screen for drugs that might inhibit the activity of Mpro. Out of a library of known inhibitors, they found that boceprevir inhibited Mpro the most. Formerly, boceprevir was used to treat hepatitis C before more effective protease inhibitors were developed. Boceprevir might find new life now as a treatment for COVID-19, and is worth further study.

 

Bello M, Martinez-Muñoz A, Balbuena-Rebolledo I. Identification of saquinavir as a potent inhibitor of dimeric SARS-CoV2 main protease through MM/GBSA. Journal of Molecular Modeling. 2020 Nov 12; 26(12):340. PMID: 33184722

Ma C, Sacco MC, Hurst B, et al. Boceprevir, GC-376, and calpain inhibitors II, XII inhibit SARS-CoV2 viral replication by targeting the viral main protease. Cell Research. 2020 Aug; 30(8):678-692. PMID: 32541865

Remdesivir Synergy Against COVID-19

Currently, remdesivir is the only antiviral drug approved to treat COVID-19. Its effects on the course of disease are moderate. Many viral diseases, such as HIV and hepatitis C, are treated with drug cocktails. Existing antiviral drugs might make remdesivir more effective in combination.

Two research teams recently screened for antiviral drugs that might increase the effectiveness of remdesivir.

Lo et al. screened a library of drugs for its ability to reduce SARS-CoV-2 viral load in kidney epithelial cells. They found that simeprevir reduces viral load in vitro. Simeprevir is a protease inhibitor that is often combined with sofosbuvir to treat hepatitis C. Simeprevir was even more effective in the in vitro experiment when combined with remdesivir.

Nguyenla et al. added remdesivir to cell cultures of kidney epithelial cells and human lung cells and infected these cells with SARS-CoV-2. They used this remdesivir-treated culture to screen a large library of FDA-approved drugs for compounds that reduce a proxy measure of viral load. The team chose the twenty most promising drugs to validate in human lung cell culture, which they tested for viral load.

The drugs velpatasvir and elbasvir reduced viral load. Both velpatasvir and elbasvir are used as parts of drug cocktails to treat hepatitis C. Velpatasvir is used with sofosbuvir and elbasvir is used with grazoprevir. The research team then tested the velpatasvir/sofosbuvir and elbasvir/grazoprevir cocktails with remdesivir in lung cell culture; the three-drug cocktails were even more effective that the pairs.

These results support the idea that COVID-19 could be better treated with cocktails of antiviral drugs.

 

Lo HS, Hui KPY, Lai HM, et al. Simeprevir potently suppresses SARS-CoV-2 replication and synergizes with remdesivir. ACS Central Science. 2021 May 26;7(5): 792-802. doi: 10.1021/acscentsci.0c01186. PMID: 34075346

Nguyenla X, Wehri E, Dis EV, et al. Discovery of SARS-CoV-2 antiviral synergy between remdesivir and approved drugs in human lung cells. BiorXiv. Preprint. 2020 Sept. http://doi.org/10.1101/2020.09.18.302398

Baloxavir Antiviral to Shorten and Prevent Influenza

Baloxavir is an antiviral drug that was FDA approved in 2018 for the treatment of influenza. It works by inhibiting an enzyme that influenza needs to replicate its DNA. When taken early, it can shorten the course of influenza by a day.

But can it also prevent influenza?

Researchers working for Shionogi, the manufacturer of baloxavir, set up a clinical trial in Japan to test this question. During the 2018-2019 flu season, they identified patients with influenza when they went to see their primary care doctor.

The researchers offered the household contacts of these patients either baloxavir or a placebo. Ten days later, the researchers tested the household contacts for influenza RNA (clinical influenza) using RT-PCR.

1.9% of household contacts who took the active treatment had clinical influenza whereas 13.6% of household contacts who took the placebo had clinical influenza. This is a successful demonstration that Baloxavir is effective at preventing influenza and as such was recently FDA approved for this use.

The authors of this study were not able to rule out whether this chemical can contribute to the rise of drug-resistant influenza. Further research is needed on this topic.

 

Baloxavir

Baloxavir Marboxil

 

Ikematsu H, Hayden FG, Kawaguchi K, et al. Baloxavir marboxil for prophylaxis against influenza in household contacts. N Engl J Med. 2020 Jul 23; 383(4):309-320. doi 10.1056/NEJMoa1915341. PMID: 32640124.

 

Rosiglitazone for Neuroinflammatory Abnormalities

Gulf War Illness is a chronic disorder brought on by exposure to sand storms, prophylaxis against chemical warfare, and chronic unpredictable stress. This illness is characterized by neuropsychological and cognitive problems affecting the central nervous system as well as specific organs.

Animal studies of this illness have shown neuroinflammation in several regions of the brain. Treatments used to reduce the neuroinflammation have led to improvements of the neurofunctional abnormalities.

Rosiglitazone and pioglitazone are compounds from the thiazolidinedione family that both have demonstrated neuroprotection in animal models. A new study recently completed at the University of Maryland looked at Gulf War Illness in a rat model and the impact of treatment with rosiglitazone.

Simulation

In order to simulate a Gulf War type of exposure, the rats were subjected to a variety of intense daily stressors for 33 days. Stressors included subjection to restraint, cold, wet, hunger, thirst, and various other types of unpredictably timed environmental stresses. During the 33 days the experimental treatment groups were also administered an oral solution of rosiglitazone each day.

Live Testing

Beginning on day 35, a battery of neurofunctional evaluations was begun. Evaluations included open-field exploration, maze exploration, new object recognition, sucrose preferences, tail suspension response, coat hygiene, splash testing, and forced swimming. These test methods were used as a gauge for cognition, anxiety-like behavior, and depression-like behavior.

Neurofunctional evaluation of the groups showed the development of significant abnormalities in rats exposed to the stressors compared to rats not subjected to such stress. The results of rats exposed to daily stressors and treatment with rosiglitazone were less conclusive. Rosiglitazone treatment seemed to improve measures related to cognition and anxiety, while not having much impact on weight gain or depression.

Tissue Testing

Following the neurofunctional evaluations, the rats were sacrificed so that the brain tissues could be analyzed. Examination of astrocytes, translocator protein, and microglia showed results consistent with a reduced inflammatory response in the samples from the rosiglitazone-treated group.

This modelling of Gulf War Illness successfully induced critical neurofunctional abnormalities, while the concurrent treatment with rosiglitazone reduced the development or abnormalities and neuroinflammation. The model will be useful for further study of the impact and potential treatments for Gulf War Illness.

 

Learn more about Gulf War Illness on Wikipedia

 

Thiazolidinediones Available:

Ciglitazone

Pioglitazone

Rosiglitazone

Rosiglitazone Maleate

Troglitazone

 

Keledjian K, Tsymbalyuk O, Semick S, et al. The peroxisome proliferator-activated receptor gamma (PPARγ) agonist, rosiglitazone, ameliorates neurofunctional and neuroinflammatory abnormalities in a rat model of Gulf War Illness. PLoS One. 2020 Nov 13;15(11):e0242427. PMID: 33186383