A recent preliminary study published on medRxiv identified ibrutinib, a drug commonly used to treat cancer, as a potential candidate for treating cocaine toxicity (1). The researchers used publicly available genome wide expression data and an unlikely model for cocaine addiction — fruit flies — to establish a new method for screening and validating generic drugs for a variety of drug use disorders.
“We have medications for opioid use disorder and alcohol use disorder, but we are lacking effective medications for stimulant use disorders, including cocaine use disorder,” said Lorenzo Leggio, deputy scientific director of the National Institute of Drug Abuse Intramural Research Program, who was not involved in this study. “It’s definitely intriguing and welcome that there are scientists who are thinking out of the box.”
For the new study, Spencer Huggert, a behavioral geneticist at Emory University and first author of the preprint paper, analyzed gene expression data from post-mortem human brain tissues from 71 individuals, 36 of whom died from cocaine overdose. He then used the NIH Library of Integrated Network-Based Cellular Signatures (LINCS) L1000 database to identify potential drug candidates.
The LINCS L1000 database contains gene expression data collected from cells treated with a variety of drugs. He analyzed the transcriptional response profiles of 825 FDA approved drugs in neuronal cells available in the L1000 database and identified 16 with transcriptional profiles opposite of those from the brains of individuals with cocaine use disorder. Essentially, genes that were highly expressed in the brains of cocaine users were expressed at low levels in neuronal cells treated with one of the drugs and vice versa.
The negative correlation was stronger than any of the 20 drugs currently in clinical trials for cocaine use disorder, suggesting that the drug may combat aberrant gene expression and therefore symptoms of cocaine toxicity more effectively than drugs currently in trial.
“The secret sauce is in the method that we use. It's just a really interpretable, robust approach to figure out which disease and compound are matched and, in this case, negatively associated,” said Huggert.
Huggert used computational analysis to trim his list. He compared the transcriptional profile of responses to each of the drugs with transcriptomics data available from published in vitro and in vivo experiments. Neuronal cells treated with ibrutinib, which is commonly used to treat leukemia, showed inverse expression profiles compared to cells and mice exposed to cocaine.
Huggert’s analysis indicated that ibruitinib may reverse the expression of key neurological signaling genes highly expressed in mice addicted to cocaine, making it a candidate for potentially treating cocaine toxicity.
He turned to geneticist Robert Anholt from Clemson University to test if ibrutinib could reverse the effects of cocaine toxicity as predicted using an established fruit fly model (2).
Anholt and Mackay fed fruit flies food spiked with cocaine, which caused frequent seizures that reduced the flies’ movement. Male fruit flies treated with ibrutinib after cocaine exposure moved more frequently and had significantly fewer seizures than untreated flies. Although female fruit flies given cocaine and ibrutinib also moved more frequently and had fewer seizures, the results were not significant.
This did not surprise Anholt, who also observed differences in cocaine responses between male and female flies when he used single cell RNA sequencing to map the transcript level changes of each cell in the brain of flies treated with cocaine (2).
“We actually looked at changes in gene expression across the entire brain, and we were able to identify a whole network of genes that are very different between males and females that show changes in gene expression when flies are exposed to a fixed amount of cocaine,” said Anholt.
Leggio suggested that adding data from a rodent model would strengthen the findings and give a stronger sense as to whether or not ibrutinib can treat cocaine use disorder and cocaine toxicity.
Huggert is already ramping up to validate these results in mice and testing the effectiveness of other drugs identified in his analysis in fruit flies to strengthen the preprint before publication in a peer-reviewed journal.
Huggert and Leggio are both excited about the potential of this method to speed the discovery of generic drug candidates for other neurological disorders.
“We can apply this wealth of data that's at our fingertips to use this kind of signature matching algorithm to find potential off label utility for other human diseases,” said Huggert. “We can apply this framework to mitigate human suffering broadly across neurological diseases.”
- Huggert, S.B. et al. Ibrutinib as a Potential Therapeutic for Cocaine Use Disorder. medRxiv (2021).
- Baker et al. The Drosophila brain on cocaine at single-cell resolution. Genome Res. doi: 10.1101/gr.268037.120 (2021).