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.”
GLOSSARY
Glutamate
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.”