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Wistar’s Medicinal Chemist Dr. Joe Salvino and the Journey to Drug Discovery

Joseph Salvino, Ph.D., medicinal chemist and professor in the Molecular & Cellular Oncogenesis Program and scientific director of the Molecular Screening & Protein Expression facility at The Wistar Institute, spent more than 20 years in the pharmaceutical industry’s drug discovery before coming to Wistar. Dr. Salvino collaborates with many Wistar scientists on programs to help identify novel small molecule lead compounds that could evolve into future drugs.

Here at the intersection of biology and chemistry is where Dr. Salvino and his team work best. Their medicinal and synthetic chemistry skills complement our investigators’ biology expertise. It’s a process wherein Dr. Salvino helps to optimize a hit compound our Wistar scientists identified or tries to identify a new lead compound for an interesting new target.

When Wistar scientists want to identify a compound that can produce a certain desired effect, Dr. Salvino works to optimize that compound’s ability to achieve its target effect. These early-stage compounds that show promise are called “hits,” and Dr. Salvino investigates these hits in a variety of biochemical settings.

Dr. Salvino’s expertise is in optimizing early-stage hits by improving target binding affinity and functional activity. His aim is to increase a compound’s biological potency and improve drug-like properties. To achieve this goal Dr. Salvino works closely with biologists to understand the molecular target. He focuses on how a small molecule will engage the target to elicit a biological response.

This crucial foundational research is the bedrock of the drug discovery process. It’s here that assays are developed with the throughput to support iterative medicinal chemistry optimization efforts that can quickly evaluate twenty or so compounds in a few days. The goal of lead optimization is to identify a suitable compound that could become a therapy to treat cancer and other disease. This is the compelling fundamental work that Wistar basic researchers accomplish before a drug discovery company considers translating what Wistar scientists have identified and potentially converts a Wistar discovery into a drug useful in health care.

As Wistar’s medicinal chemist, describe how you fit into Wistar’s scientific efforts?

I work in collaboration with Wistar scientists and scientists at neighboring universities to help identify a series of compounds suitable as a pharmacological means to modulate their target of interest. My job is to identify a suitable compound, part of a “hit-to-lead” series usually identified from a screening campaign, to test pharmacologically the effects of small molecule treatment both in vitro and in vivo.

In a lay friendly way tell us your process working with the scientists.

We work with other scientists by identifying and improving on small molecules that engage their protein target of interest. These small molecules may inhibit, stimulate, or degrade their protein and be biologically active in a cell expressing their protein, or where their protein is the cause for the disease we are trying to treat. My team needs to learn as much as we can about the molecular target from our collaborator.

We work with many Wistar investigators—typically those who are looking to identify or improve on a small molecule as a potential therapeutic agent for a disease related to their target. Often the investigator has already identified a small molecule to test their hypothesis. My team works in collaboration to improve or develop a new molecule, focusing on improving selectivity, potency, or its in vivo drug-like properties.

The Wistar Institute Molecular Screening & Protein Expression Core is under my direction. This group can develop assays that typically can be run in a plate-based format to provide a high-throughput approach to support our medicinal chemistry efforts. For example, when medicinal chemists are trying to identify an optimized compound, we need to synthesize and evaluate 10-50 different analogs that are related but have slight differences in their structure. We do this to probe for “structure activity relationships”—the changes required to improve binding affinity to a protein target or to improve its functional activity. Both binding affinity and functional efficacy are very important to optimize a molecule, even though its functional efficacy is what a biologist wants to study.

Interestingly, a typical drug discovery effort from a pharmaceutical company requires the synthesis of about 2000-3000 compounds per target to identify a development candidate.

How do you start working with scientists?

We start to work together because of a common interest in a target or a disease, such as treatment of melanoma, ovarian, or breast cancer or EBV associated cancer, or others. We normally start collaborating because of our common interests and complementary skills.

What aspects of your work do you like most?

I enjoy the interface between chemistry and biology. I love finding new compounds with interesting biological activity in collaboration with my colleagues, especially for interesting new targets. I like working with the screening core to help develop new methods to test compounds. We spend a lot of time synthesizing chemical probes, such as a binding probe, which greatly facilitate assay development. A binding probe, or also sometimes called a tracer, is used in a competitive binding assay, where an unlabeled compound will compete for binding with the tracer. For this type of study, we can determine the binding affinity of an unlabeled test compound.

Wistar does not make drugs or therapies but advances discoveries that can move into drug discovery as future therapeutics.

Spotlight on Wistar COVID-19 Researchers: Luis Montaner, D.V.M., D.Phil., & Joseph Salvino, Ph.D.

Dr. Luis Montaner is an HIV expert focused on finding new ways to boost the natural function of the immune system to combat infection or viral-associated disease. Dr. Joseph Salvino is a medicinal chemist and an expert in drug discovery and identification of novel small molecule lead compounds. The two have combined their expertise to design a strategy to modulate the immune response to viral infections using novel small molecules. They discuss the basis of this approach and how they are advancing it.

Montaner: We are born programmed to resist viral infections. One of the key weapons our immune system uses to respond to viruses is interferon, which “interferes” with the viral replication. However, sometimes our system is not effective. Our goal is to amp up the natural immune response to COVID-19 in a targeted way without inducing greater inflammatory damage in the lung.

Salvino: Interferons activate the immune response by engaging a specific receptor present on the cell surface. We are developing compounds that stimulate binding of interferons to their receptor and activate signaling to the cell to initiate an antiviral response. We have some interesting lead compounds that we are testing to confirm they have the intended biological effect without toxicity.

Montaner: Joe and I have been collaborating for the past three years to find small molecules that can modulate immunity in HIV by acting on the interferon response, as one of my lab’s interests is what happens when this response becomes chronic and poses problems.

Salvino: For this project, we have now tested about 20-30 thousand compounds based on computer models and predictions. We were looking for inhibitory compounds that block the interaction of interferons with their receptor, but we have also come across stimulatory compounds that have the opposite effect and can actually serve as a glue between ligand and receptor.

Montaner: When the COVID-19 outbreak started, we realized we had those molecules in our hands that could potentially be helpful and limit the disease by amplifying the interferon antiviral response. These small molecules act as cement between interferon and receptor, making the interaction more stable and, as a consequence, strengthening the stimulation provided on the immune cell. We don’t want to make it irreversible, though. We want to maintain an off switch because the immune cells are not programmed to be on a constant inflammatory state and that could lead to tissue damage, for example to the lungs in the case of COVID-19.

So, we looked back at several molecules that in our studies made the interferon response better. The platform we developed to test our inhibitory compounds in vitro and in vivo gives us the advantage of time because we don’t need to set up new systems and assays; we already have them in place. Basically, we are steps ahead in the process because we already have candidate molecules and the appropriate tools to test them. We are evaluating these compounds to track their effect on the immune response in vivo.

Salvino: There are limited small molecule drugs available to fight viral infections and, in general, they work by directly interacting with the virus. For example, a compound could bind to the “Spike” of COVID-19 to block the virus from entering the host cells; or it could directly bind to an essential component in the virus to reduce its ability to function. However, viruses have the ability to mutate and become resistant to drugs, and that small molecule could lose effectiveness. Our approach is different because it targets the host and has a reduced likelihood of causing resistance compared to virus-directed approaches.

Montaner: These small molecule drugs can potentially amplify the natural antiviral response and prevent the COVID-19 virus from establishing an infection, or rapidly fight it off. In theory, such therapeutic booster could be used alone at onset of symptoms or later on in combination with other antiviral drugs.

Salvino: This work is very collaborative. Our labs complement each other, since my expertise in organic and synthetic chemistry is combined with Luis’s immunology and biology expertise.

Montaner: As a basic biomedical research institute, Wistar makes fundamental discoveries and generates proofs of concepts for potential new therapies. For example, after identifying new compounds, we study their activity and test them in preclinical models. Once these steps are complete, partnerships with industry become critical in order to translate our discoveries into new medicines.

We believe our work to identify small molecules to boost the immune response against viral infection could potentially be important in the COVID-19 crisis, and for other diseases, but even getting to the point at which a new candidate drug is attractive to industry partners requires extensive work and robust financial support.

Using Spider Venom to Make New Therapeutics for Central Nervous  System Disorders

Wistar’s Joseph Salvino, Ph.D., medicinal chemist and professor in the Molecular & Cellular Oncogenesis Program, and scientific director of the Molecular Screening & Protein Expression facility at Wistar, is currently developing a new potential therapy based on the venom of the Parawixia striata spider. This colony spider lives socially in a cluster of hundreds of spiders high up in tree canopies throughout South America, including Brazil. It uses its venom to paralyze insect prey.

“This project is different from the bulk of my work, because spider venom is a natural product made from a very complex cocktail of proteins, peptides, salts, and other molecules,” said Salvino. “Synthesizing natural products is extremely complex.”

The unique opportunity for Salvino to work with spider venom originated through a collaboration with colleague Andréia Mortensen, Ph.D., assistant research professor in the Pharmacology & Physiology Department at Drexel University College of Medicine, whose Ph.D. thesis centered on animal venoms and how they modulate the central nervous system.

“I was working towards a Ph.D. in biochemistry at Ribeirão Preto School of Medicine at the University of São Paulo, Brazil,” said Mortensen. “My advisor was interested in animal venoms of all kinds and we found interesting components of these venoms that would regulate the central nervous system of mammals. One of these is glutamate, which is also the main excitatory neurotransmitter in our brain.”

Mortensen studied the effects of venom in animal studies and found one component increased the activity of glutamate transporters. 

“This venom component helps transporters remove excess glutamate and therefore is neuroprotective in conditions like traumatic brain injury, where excess glutamate causes too much excitation and kills brain cells,” she said.

Mortensen, Salvino and colleagues are interested in treating other disorders and diseases of the central nervous system such as Alzheimer’s disease, Parkinson’s disease, Huntington’s disease, ALS (Amyotrophic Lateral Sclerosis), epilepsy, stroke, and neuropathic pain, where there is a disfunction in glutamate concentrations or an over-release of glutamate that results in toxicity. 
Previous work had shown that there were structures in venom that would target glutamatergic channels and receptors in our brain. “But there could be much more—transporters are other structures in our brain that we thought venom could modulate, but we didn’t know exactly how,” said Mortensen. 

It was the 90s in Brazil with a rich source of spiders in the vicinity of the university. What started as an exploration became a major find in the components of venom in these spiders. Spider venom became Mortensen’s life’s work. She continued collecting spiders, extracting venom and characterizing it with high profile liquid chromatographs that break down venom into several components. Then she came to the United States to access technology specialized in glutamate transporters and carried out selectivity studies and finally found the one active component of the venom she was targeting.

“I was at Oregon Health Science University (OHSU) for six months in the middle of my Ph.D. on an internship as an exchange student,” said Mortensen. “But I came back to do my postdoctoral fellowship at OHSU. At that point, I changed my interest to understanding glutamate transporters: Nowadays my lab at Drexel is a ‘glutamate transporter’ lab and we use the venom to develop synthetic components, which has become a collaboration of more than six years with Dr. Salvino, who can take my work further. Our collaboration came at the right time because working with natural products is very tricky.”

Salvino spent more than 20 years in drug discovery at biotechnology and pharmaceutical industries before he became a professor in the Department of Pharmacology and Physiology at Drexel and then came to Wistar. He works closely with many scientists to help identify novel small molecule lead compounds that could become future drugs. Exploring spider venom for possible drug targets was a welcome challenge. 

“Glutamate is an important neurotransmitter,” said Salvino. “You need it, but at high concentrations it causes glutamate excitotoxicity. In diseases where you have this excess glutamate effect, it causes neurodegeneration or pain.”

Devi Ashok, Ph.D., another key player in this project, was a graduate student in chemistry and worked as a postdoctoral fellow at the University of Guelph, in Canada. She then enrolled in the Master’s program in Drug Discovery & Development at Drexel in 2015 with the hope of working in the pharmaceutical industry. “I worked with Dr. Salvino for two summers and came up with the first lead compound derived from spider venom,” said Ashok. “The project was very interesting and rewarding. I always wanted to work in pharma and this turned into a good platform to launch my career ambition.” Ashok was involved in the synthesis of analogues which had the potential to boost activity of glutamate transporters in the brain.

“It was so exciting to be in the lab making a compound that would be tested in real time by a fellow student just across the corridor,” said Ashok. “Getting that immediate feedback was fantastic and led me to think about what experiments I should do next, what changes I should make to get a more positive result and what direction I should try.”

Ashok’s compound was definitely neuroprotective. “It protects against neurodegeneration induced in a traumatic brain injury,” said Salvino. “It stimulates the transporters to remove excess glutamate, is protective and shields against neurodegeneration.”

Nick Anastasi, a University of Pittsburgh student, interned in Wistar’s Salvino Lab in the summer of 2017. 

“My primary job was synthesizing new chemical compounds of Ashok’s advanced lead,” said Anastasi. “We had molecules we knew were active and performed in a certain way, and I was making modifications to them to improve activity, which it ultimately ended up doing.” 
Because of his experience in the Salvino Lab, Anastasi was inspired to change direction in his education and focus on bioengineering.

“I’m interested in going into the biotech industry after having worked at Wistar and seeing how Dr. Salvino forged his path,” said Anastasi. “The industry is very interesting and rewarding. It’s an upfront satisfaction where, once you complete your work and you have your lead, you can transfer it to partners that will develop and commercialize a product that helps people. Hopefully the scientific advancement I helped make at Wistar will be able to cure people and have multiple applications.” The satisfaction of running reactions, making chemicals and creating molecules is payoff in itself. 

“It’s not uncommon to find researchers in the lab throughout the day because they’re running reactions and very into what they’re doing,” said Salvino. “What’s cool with Devi and Nick is they were able to make compounds that had great activity. They could see it, and I could see that spark.”

Next steps are to realize the compound’s potential by securing funding and garnering interest from industry. But the crux of their success lies in exploration, determination and collaboration.
“We’d love to see this eventually evaluated in clinical trials to confirm this approach is useful,” said Salvino. “We’re the only ones with a molecule like this and it’s eluded the industry for years. We would love to get this into clinic.” 


The main excitatory neurotransmitter in the central nervous system, also involved in memory and learning. In the synapses, it’s released by nerve cells and binds with specific receptors that send a signal down to the muscles or brain, but too much of it causes overstimulation.

Salvino says: “It’s like an electrical cable—you put too much voltage to it and it burns up and then neuronal death happens.”

Glutamate Transporters 
Proteins that play an important role regulating the amount of glutamate in the extracellular space in the brain, preventing excessive stimulation of glutamate receptors.

Salvino says: “Transporters sit like a vacuum cleaner and suck out glutamate from the synaptic space. As soon as it’s sucked out, it’s converted to glutamine and becomes inactive. Transporters are key to keeping the balance. Think of any electrical circuit or battery—too much electricity going across will short-circuit.”

Meet Wistar’s First Medicinal Chemist

In February, Joseph Salvino, Ph.D., joined The Wistar Institute as professor in the Molecular and Cellular Oncogenesis Program and Scientific Director of the Institute’s Molecular Screening Facility. Salvino focuses on drug discovery and development and using small molecules as tools to confirm whether a newly discovered therapeutic target is “druggable.” Salvino recently answered some questions about his background in medicinal chemistry and what projects he’ll be working on at Wistar.

Q: How did you get interested in medicinal chemistry?

A: Initially, I thought I was going to pursue a career in biology, but that all changed once I took organic chemistry in college. From that moment on, I knew I wanted to design molecules that are biologically active, meaning they have beneficial effects on cells. Having a better understanding of chemistry allows me to find the proper molecules that will act on therapeutic targets. After I received my Ph.D. from Brown University in organic chemistry, I completed postdoctoral training in synthetic and medicinal chemistry at the University of Pennsylvania. The field offers tremendous flexibility as well. In my career, I’ve worked on drug design projects in a variety of disease types. I may not have a deep understanding of disease quite like biologists do, but what I’ve been able to do is take their findings and determine how to design a drug that can be tested clinically.

Q: Why do you feel Wistar is a good fit for your skills?

A: I came to Wistar from Drexel, so I’m already pretty familiar with the Philadelphia life sciences community. I’ve also had the pleasure of working with a few of Wistar’s scientists prior to coming here. For example, I’ve collaborated with Drs. Paul Lieberman and Troy Messick of Wistar’s Gene Expression and Regulation Program on their Epstein-Barr virus drug development project since 2012. At Wistar, you have so many really talented cancer biologists that have discovered several targets for a variety of diseases. From my end, I need to take those targets and make them druggable. In some cases, these scientists have the therapeutic target they want to study but are overwhelmed by the process of determining which drugs could act on that target. In other instances, the target is already druggable, but the design needs to be improved in order to reduce toxicity of the drug, which can cause adverse affects in patients. The goal is to demonstrate the effectiveness of these targets and drugs here so that we can more quickly move them into clinical trials.

Q: What are some of the projects you’ll be working on at Wistar?

A: There are several ongoing projects that I’m excited to work on. Dr. Qihong Huang is working on an exciting target called GABRA3, which is expressed in metastatic breast cancer tissue. Dr. Maureen Murphy has a great target called HSP70, a stress-survival protein found in many different types of tumors. Dr. Meenhard Herlyn’s lab is also working on a drug development project for melanoma. These are just a few examples of the types of projects I’ll be focusing on as I take these targets off the hands of the biologists and help them reach their full potential.

Q: One of your other roles here is as scientific director of Wistar’s Molecular Screening Facility. What are your plans for this facility?

A: One of the things I’m hoping to work on with our scientists is to move their discoveries into what’s known as the hit-to-lead stage. The idea is to take a target and to use something called high throughput screening to find promising lead compounds that could be studied as potential drugs. High throughput screening allows scientists to test hundreds, thousands, or many, many more compounds for biochemical activity, saving considerable time in taking these promising targets and finding the drugs that act upon them. I have enough experience to look at the structure of a molecule and, in many cases, I’ll know whether there are drugs available that may act on it. In any event, the screening helps get these discoveries to that crucial hit-to-lead stage, which ultimately results in new drugs being developed more quickly and more effectively.