Cytochrome P450 Inhibition: Old Drug, New Tricks

multiwell screening plate and various pills on a table

Cytochrome P450 (CYP) inhibitors are often used as boosting agents in combination with other drugs. This drug development strategy is front and center for Paxlovid, the new anti-SARS-CoV-2 treatment from Pfizer. Paxlovid is a combination therapy, comprised of two protease inhibitors, nirmatrelvir and ritonavir. It significantly reduces the risk of COVID-19 hospitalization in high-risk adults and is ingested orally rather than injected, which is an advantage over other SARS-CoV-2 treatments, such as Remdesivir.

Nirmatrelvir was originally developed by Pfizer almost 20 years ago to treat HIV and works by blocking enzymes that help viruses replicate. Pfizer created another version of this drug to combat SARS in 2003, but, once that outbreak ended, further development was put on pause until the advent of the COVID-19 pandemic. After developing an intravenous form of nirmatrelvir early in the pandemic, Pfizer created another version that can be taken orally and combined it with ritonavir.

When ritonavir was originally developed, it wasn’t considered particularly useful because it metabolized so quickly in the body. Now it is recognized as a pharmacokinetic enhancer in combination with other drugs. Ritonivir inhibits CYP3A4, an enzyme which plays a key role in the metabolism of drugs and xenobiotics. By inhibiting CYP3A4, ritonivir slows the metabolism of other drugs. In the case of Paxlovid, this allows nirmatrelvir to stay in the body longer at a high enough concentration to be effective against the virus. This ultimately means that patients can be given lower doses of the drug with reducing efficacy.

Diagram of Nirmaltrelvir mechanism of action.
Nirmatrelvir inhibits the viral 3CL protease, so that functional, smaller viral proteins cannot be produced.
Continue reading “Cytochrome P450 Inhibition: Old Drug, New Tricks”

Rice-Based Cholera Vaccine

Oral vaccines are a great strategy and are especially beneficial in areas with poor sanitation. This form of vaccine distribution could help control the acute diarrheal disease caused by Vibrio cholera. There are an estimated 1.3 to 4 million cases and 21,000 to 143,000 deaths from cholera each year. A recent study from The Lancet Microbe finds new hope in a rice-based cholera vaccine that will fight against the diarrheal toxin without severe adverse events.

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RAS-Targeted Drug Discovery: From Challenge to Opportunity

cancer cell, ras-targeted drug discovery

In 1963, Jennifer Harvey was studying Moloney murine leukemia virus (MMLV) at the cancer research department of the London Hospital Research Laboratories. After routine transfers of plasma from MMLV-infected rats to mice, she made an unusual discovery. In addition to the expected leukemia, the mice that received the plasma developed solid tumors (soft-tissue sarcomas), primarily in the spleen (1). A few years later, Werner Kirsten at the University of Chicago observed similar results working with mouse erythroblastosis virus (MEV) (2).

Subsequent research, with the advent of genome sequencing, showed that a cellular rat gene had been incorporated into the viral genome in both cases (3). These genomic sequences contained a mutation later shown to be responsible for the development of sarcomas, and the word “oncogene” became a common part of the vocabulary in cancer publications during the early 1980s (4). Harvey’s discovery led to the naming of the corresponding rat sarcoma oncogene as HRAS, while Kirsten’s related oncogene was named KRAS. Several laboratories, working independently, cloned the human homolog of the viral HRAS gene in 1982 (3). The human KRAS gene was cloned shortly thereafter, as well as a third RAS gene, named NRAS (3). Additional studies showed that a single point mutation in each of these genes led to oncogenic activation, and they have been popular targets for anticancer drug discovery efforts ever since.

Continue reading “RAS-Targeted Drug Discovery: From Challenge to Opportunity”

RNA-Protein Interactions: A New Frontier for Drug Discovery

Almost 90% of the human genome is transcribed into RNA, but only 3% is ultimately translated into a protein. Some non-translated RNA is thought to be useless, while some play a significant yet often mysterious role in cancer and other diseases. Despite its abundance and biological significance, RNA is rarely the target of therapeutics.

“We say it’s undruggable, but I would say that ‘not-yet-drugged’ is a better way to put it,” says Amanda Garner, Associate Professor of Medicinal Chemistry at the University of Michigan. “We know that RNA biology is important, but we don’t yet know how to target it.”

Amanda’s lab develops systems to study RNA biology. She employs a variety of approaches to analyze the functions of different RNAs and study their interactions with proteins. Her lab recently published a paper describing a novel method for studying RNA-protein interactions (RPI) in live cells. Amanda says that with the right tools, RPI could become a critical target for drug discovery.

“It’s amazing that current drugs ever work, because they’re all based on really old approaches,” Amanda says. “This isn’t going to be like developing a small molecule kinase inhibitor. It’s a whole new world.”

Continue reading “RNA-Protein Interactions: A New Frontier for Drug Discovery”

Paving New Ways for Drug Discovery & Development: Targeted Protein Degradation

The Dana-Farber Targeted Protein Degradation Webinar Series discusses new discoveries and modalities in protein degradation.

In this webinar, Senior Research Scientist, Dr. Danette Daniels, focuses primarily on proteolysis-targeting chimeras, or PROTACs. A variety of topics are covered including the design, potency, and efficacy of PROTACs in targeted protein degradation. Watch the video below to learn more about how PROTACs are shifting perspectives through fascinating research and discoveries in targeted protein degradation.

Learn more about targeted protein degradation and PROTACS here.

Young Scientist Discovers Potential Anti-SARS-CoV-2 Drug Molecule

14-year-old Anika Chebrolu spent the early months of the COVID-19 pandemic identifying a potential anti-SARS-CoV-2 drug candidate. Originally, she was screening potential anti-influenza treatments, but as she watched COVID-19 case numbers rising around the world, she pivoted to focus instead on the SARS-CoV-2 virus. Several months later, Anika not only discovered a strong candidate for further testing, but she earned the title of 2020 Top Young Scientist in a competition sponsored by 3M.

3d model of coronavirus SARS-CoV-2
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RiboMAX and the Effort to Find Antiviral Drugs to Fight Coronaviruses and Enteroviruses

Prior to 2020, there were two major outbreaks of coronaviruses. In 2003, an outbreak of SARS-CoV sickened 8098 people and killed 774. In 2012, an outbreak of MERS-CoV began which so far has sickened 2553 and killed 876. Although the overall number of MERS cases is low, the disease has a high fatality rate, and new cases are still being reported. Even though fatality rates are high for these two outbreaks, containment was quickly achieved. This makes development of a treatment not commercially viable so no one had undertaken a large effort to develop an approved treatment for either coronavirus infection.

Fast forward to late 2019/2020… well, you know what has happened. There is currently no reliable antiviral treatment for SARS-CoV-2, the coronavirus that causes COVID-19 infections.

Zhang, et al. thought of a way to make an antiviral treatment commercially viable. If the treatment is actually a broad-spectrum antiviral, it could be used to treat more than one infection, meaning, it can be used to treat more people and thus be seen as more valuable and worth the financial risk to pharmaceutical companies. So, they decided to look at the similarities between coronaviruses and enteroviruses.

Continue reading “RiboMAX and the Effort to Find Antiviral Drugs to Fight Coronaviruses and Enteroviruses”

Catalyzing Solutions with Synthetic Biology

Computer-generated model of a virus.

The keynote speaker for this year’s International Symposium on Human Identification (ISHI), Andrew Hessle, describes himself as a catalyst for big projects and ideas (1). In biology, catalysts are enzymes that alter the microenvironment and lower the energy of activation so that a chemical reaction that would proceed anyway happens at a much faster rate—making a reaction actually useful to the biological system in which it occurs.

In practical terms, Andrew Hessel is the person who helps us over our inertia. Instead of waiting for someone else, he sees a problem, gathers an interested group of people with diverse skills and perspectives, creates a microenvironment for these people to interact, and runs with them straight toward the problem. Boom. Reaction started.

One of the problems he has set his mind toward is that of cancer drug development. Continue reading “Catalyzing Solutions with Synthetic Biology”

Increasing Drug Research and Development Efficiency Using a 4-point Screening Method to Determine Molecular Mechanism of Action

Fig 4. Four point MMOA screen for tideglusib and GW8510. Time dependent inhibition was evaluated by preincubation of TbGSK3β with 60 nM tideglusib and 6 nM GW-8510 with 10μM and 100μM ATP. (A). Tideglusib [60 nM] in 10μM ATP. (B). GW8510 [60 nM] in 10μM ATP. (C.) Tideglusib [60 nM] at 100μM ATP. (D.) GW8510 [60 nM] at 100μM ATP. All reactions preincubated or not preincubated with TbGSK3β for 30 min at room temperature. Experiments run with 10μM GSM peptide, 10μM ATP, and buffer. Minute preincubation (30 min) was preincubated with inhibitor, TbGSK3β, GSM peptide, and buffer. ATP was mixed to initiate reaction. No preincubation contained inhibitor, GSM peptide, ATP, and buffer. The reaction was initiated with TbGSK3β. Reactions were run at room temperature for 5 min and stopped at 80°C. ADP formed was measured by ADP-Glo kit. Values are mean +/- standard error. N = 3 for each experiment and experiments were run in duplicates. Control reactions contained DMSO and background was determined using a zero time incubation and subtracted from all reactions. Black = 30 min preincubation Grey = No preincubation.
Four point MMOA screen for tideglusib and GW8510.
Time dependent inhibition was evaluated by preincubation of TbGSK3β with 60 nM tideglusib and 6 nM GW-8510 with 10μM and 100μM ATP. (A). Tideglusib [60 nM] in 10μM ATP. (B). GW8510 [60 nM] in 10μM ATP. (C.) Tideglusib [60 nM] at 100μM ATP. (D.) GW8510 [60 nM] at 100μM ATP. All reactions preincubated or not preincubated with TbGSK3β for 30 min at room temperature.  Black = 30 min preincubation Grey = No preincubation.
The first small-molecule kinase inhibitor approved as a cancer therapeutic, imatinib mesylate (Gleevec® treatment), has been amazingly successful. However, a thorough understanding of its molecular mechanism of action (MMOA) was not truly obtained until more than ten years after the molecule had been identified.

Understanding the MMOA for a small-molecule inhibitor can play a major role in optimizing a drug’s development. The way a drug actually works–the kinetics of binding to the target molecule and how it competes with endogenous substrates of that target–ultimately determines whether or not a a candidate therapeutic can be useful in the clinic. Drugs that fail late in development are extremely costly.

Drug research and discovery for neglected tropical diseases suffer from a lack of a large commercial market to absorb the costs of late-stage drug development failures. It becomes very important to know as much as possible, simply and quickly, about MMOA for candidate molecules for these diseases that are devastating to large populations.

One such neglected topical disease is Human African trypanosomiasis (HAT, also known as sleeping sickness). Continue reading “Increasing Drug Research and Development Efficiency Using a 4-point Screening Method to Determine Molecular Mechanism of Action”

Customized Kinase Selectivity Profiling Just Got Easier

11296971-DC-CR-KinaseOff-target activities of target compounds can become costly if they aren’t discovered until late in the drug research and discovery process. Therefore, knowing the inhibitory profile of your test compounds across a broad collection of kinases as quickly as possible is highly desirable.

However, screening against many kinases at once requires a universal platform that is still sensitive enough to detect inhibitor activity and assess selectivity and potency on kinases of different classes. The luminescent ADP-Glo™ Kinase Assay is a universal platform that measures kinase activity by quantifying the amount of ADP produced during a kinase reaction.

We have used the ADP-Glo™ Chemistry to develop highly sensitive assays for more than 170 kinases across the human kinome and further enhanced the assays for ease-of-use by developing the Kinase Selectivity Profiling Systems. These systems provide an easy-to-use, reliable platform for kinase inhibitor profiling in house.

And even better, we now provide an online Kinase Profiling System Designer so that you can design a custom Kinase Selectivity Profiling System to fit your exact experimental needs. Simply drag and drop the combination of kinases you need to create an 8-kinase strip and submit your order. Continue reading “Customized Kinase Selectivity Profiling Just Got Easier”