This accomplishment, described in the December 13, 2012, issue of the journal Nature, may prove invaluable for developing drugs to treat many common diseases such as diabetes, high blood pressure, obesity, cancer, schizophrenia, and bipolar disorder. Such disorders are called complex diseases because each has a number of genetic and non-genetic influences that determine whether someone will develop the disease.

“In terms of the genetics of schizophrenia, we know there are likely hundreds of different genes that can influence the risk for disease and, because of that, there’s likely no single gene and no one drug target that will be useful for treating it, like other common complex diseases,” says study co-leader Bryan Roth, MD, PhD, the Michael J. Hooker Distinguished Professor of Pharmacology in the UNC School of Medicine, a professor in the Division of Chemical Biology and Medicinal Chemistry in the UNC Eshelman School of Pharmacy, and the director of the National Institute of Mental Health Psychoactive Drug Screening Program.

Roth says that drug design for complex neuropsychiatric conditions, infectious diseases, and cancer has been selectively aimed at a single molecular target in the past twenty years, but because these are complex diseases, the drugs are often ineffective and thus many never reach market.

Moreover, a drug that acts on a single targeted protein may interact with many other proteins, frequently causing toxicity and adverse effects.

“And so the realization has been that perhaps one way forward is to make drugs that hit collections of drug targets simultaneously. This paper provides a way to do that,” Roth says.

According to Roth, pharmaceutical company chemists had suggested that it was impossible to create a drug that hits multiple targets simultaneously, but “here we show how to efficiently and effectively make designer drugs that can do that.”

The new approach involves automated drug design by computer that takes advantage of large databases of drug-target interactions. The databases have been made public through Roth’s lab at UNC and through other resources.

Basically the researchers, also co-led by Andrew L. Hopkins, PhD, at the University of Dundee, used the power of computational chemistry to design drug compounds that were then synthesized by chemists, tested in experimental assays, and validated in mouse models of human diseases.

The team experimentally tested eight hundred drug-target predictions of the computationally designed compounds. Of those, 75 percent were confirmed in in-vitro experiments.

Drug-to-target engagement also was confirmed in animal models of human diseases. In a mouse model of attention deficit hyperactivity disorder, mice missing a particular dopamine receptor display distractibility and novelty seeking—recurrent aberrant behaviors similar to what is seen in ADHD. “We created a compound that was predicted to prevent those recurrent behaviors and it worked quite well,” Roth said.

The researchers then tested the compound in another mouse model where a particular enzyme for a brain neuropeptide is missing, also resulting in distractibility and novelty seeking. The drug had the same effect in those mice.

The new drug design process includes ensuring that compounds enter the brain by crossing the blood-brain barrier, which was also successfully tested in live animals.

Along with Roth, other UNC researchers among the study’s twenty-one co-authors include Vincent Setola, Xi-Ping Huang, and Maria F. Sassano. Other co-authors are from the University of Dundee, the Duke University Medical School, the Clinical Research Institute of Montreal, and the Swiss Federal Institute of Technology.

Part of the funding for the research comes from the National Institutes of Health grants supporting drug discovery receptor pharmacology.

Story courtesy of UNC Health Care

Bryan Roth, PhD, MD, a Michael Hooker Distinguished Professor in the UNC School of Medicine and the pharmacy school, is one of the lead investigators on the grant. Jian Jin, PhD, an associate professor and the associate director of medicinal chemistry at the pharmacy school’s Center for Integrative Chemical Biology and Drug Discovery, is the principal investigator for one of the projects supported by the grant.

Jin’s lab will receive $1.15 million in direct cost to create clinical candidates for treating schizophrenia and other mental disorders. In 2011, researchers led by Jin and Roth discovered three first-in-class chemical compounds that have an unprecedented mechanism of action. Jin will use the new grant to develop those compounds into clinical candidates, which could ultimately lead to safer, more effective medications for those conditions.

The other lead investigator on the grant is Marc Caron, PhD, the James B. Duke Professor of Cell Biology at the Duke University School of Medicine. The other investigators include William Wetsel, PhD, an associate professor of psychiatry at Duke University; and Doug Johnson, PhD, and Chris Schmidt, PhD, of Pfizer. Schmidt is senior director at Pfizer Global Research and Development, while Johnson is an associate research fellow at Pfizer Worldwide Research and Development.

The most characteristic feature of AS is the absence or near absence of speech throughout the person’s life. The disease, often misdiagnosed as cerebral palsy or autism, is caused by mutations or deletions in the Ube3a gene inherited from the mother, or the maternal allele. The Ube3a protein produced by that gene is a key component of an important molecular pathway that helps brain neurons pass electrical or chemical signals to other neurons via the synapse.

There is a paternal Ube3a allele, but whereas both the maternal and paternal alleles are expressed in most body tissues, this gene is dormant in human and rodent neurons.

“We wanted to determine if there could be a way to awaken the dormant allele and restore Ube3a expression in neurons,” says neuroscientist Benjamin D. Philpot, PhD, one of three senior investigators in the study and an associate professor of cell and molecular physiology at the UNC School of Medicine.

In a paper published online December 21 in the journal Nature, the team of UNC scientists, which included researchers from the UNC Eshelman School of Pharmacy, says it has found a way to awaken the paternal Ube3a allele, opening the door to a potential treatment strategy for AS.

Using a library of FDA-approved drugs, the UNC team discovered that irinotecan, a topoisomerase inhibitor known to be active in the central nervous system, robustly awakened Ube3a in genetically engineered mice. Subsequently, the team found that the medication topotecan and several other topoisomerase inhibitors can also awaken Ube3a.

Importantly, the protein from the awakened paternal Ube3a was functional and was expressed by the gene in amounts comparable to that of normal maternal Ube3a in control animals.

The researchers determined that topotecan awakened the dormant paternal Ube3a allele by reducing antisense RNA, a strand of ribonucleic acid that silences the allele.

The study is “the first example of a drug that regulates antisense RNA and, as a result, regulates protein levels of a coding gene,” says neuroscientist Mark J. Zylka, PhD, one of the study’s senior coauthors and an assistant professor of cell and molecular physiology.

Zylka and Philpot caution against using topoisomerase inhibitors right now to treat AS, given the limits of current knowledge.

“We’d like to stress that these compounds are not ready to be used clinically for Angelman syndrome,” Zylka says. “We don’t know what the off-target effects might be on a gene or genes with similar DNA sequences. We need to figure out optimal concentrations and dosing before we move to clinical trials. And we need to determine which drug is best.”

The other senior coauthor on the study is Bryan Roth, MD, PhD, the Michael Hooker Distinguished Professor of Pharmacology and Translational Proteomics, director of the National Institute of Mental Health Psychoactive Drug Screening Program, and a professor in the UNC Eshelman School of Pharmacy. Jian Jin, PhD, the associate director of medicinal chemistry at the Center for Integrative Chemical Biology and Drug Discovery, was also on the team of researchers.

Other UNC coauthors are: Hsien-Sung Huang, John A. Allen, Angela M. Mabb, Ian F. King, Jayalakshmi Miriyala, Bonnie Taylor-Blake, Noah Sciaky, J. Walter Dutton Jr., Hyeong-Min Lee, Xin Chen, and Arlene S. Bridges.

The research was supported in part by funds from the Angelman Syndrome Foundation, the Simons Foundation, the National Institute of Mental Health, the National Eye Institute, the National Institute of Neurological Disorders and Stroke, the NIMH Psychoactive Drug Screening Program, and the NC TraCS Institute funded by the NIH Clinical and Translational Science Awards (CTSA).

Story and photo courtesy of UNC Healthcare

Schizophrenia is typically treated with antipsychotic medications, but the medications do not adequately treat a high percentage of patients. The drugs don’t address the negative and cognitive symptoms of schizophrenia, and all current antipsychotics can lead to serious side effects such as cardiovascular conditions and weight gain with chronic use.

The new compounds, which UNC has patented, will help address these problems by enabling researchers to better study which key signaling pathways in the body are essential to the effectiveness and side effects of antipsychotics, says Jian Jin, PhD, one of the study’s corresponding authors and the associate director of medicinal chemistry at the pharmacy school’s Center of Integrative Chemical Biology and Drug Discovery.

“These compounds are unprecedented,” says Jin, who spearheaded the medicinal chemistry portion of the research. “They give biomedical researchers a powerful tool for studying the relationship between signaling pathways and the efficacy and side effects of antipsychotic medications. That understanding will help us design better treatments.

“At the same time, these novel compounds themselves could be developed into clinical candidates for treating schizophrenia and related disorders, with improved efficacy and fewer side effects. So this discovery is highly significant.”

The study’s findings are described in a paper to be published during the week of October 24 in the online Early Edition for the journal Proceedings of the National Academy of Sciences, USA. Jin and Bryan Roth, PhD, MD, led a team that included researchers from Duke University and Columbia University. Roth, who directed the pharmacological component of the study, is a Michael Hooker Distinguished Professor in the UNC School of Medicine and the pharmacy school.

There are two major types of signaling pathways for this drug target. One type is mediated by a class of proteins called G proteins, while the other is controlled by a different group of proteins, including a prominent one called beta-arrestin. The new compounds activate the beta-arrestin pathways but not the G protein-mediated pathways, allowing researchers to study them separately.

“This discovery provides a completely new approach for treating schizophrenia and related disorders with greater efficacy and fewer side effects,” says Roth, who directs the National Institute of Mental Health Psychoactive Drug Screening Program at UNC-Chapel Hill.

Jin and Roth are also working to identify compounds that would activate only the G protein-mediated pathways. Jin said that only a very limited number of functionally selective compounds — compounds that selectively activate one signaling pathway over the other — have been reported to date.

“Prior to our study, there had been very little purposeful attention devoted to creating and annotating novel compounds that show functional selectivity,” Jin says. “Our approach, which combines comprehensive medicinal chemistry and pharmacological profiling, provides a successful proof-of-concept for how such compounds can be discovered and validated.”

The study was supported by funding from the National Institutes of Health and the NIMH. The co-first authors are John A. Allen, PhD, and Vincent Setola, PhD, from Roth’s lab and Julianne M. Yost, PhD, from Jin’s lab. Other researchers who worked on the project include

• From Roth’s lab: Maria F. Sassano, PhD; Prem N. Yadav, PhD; Xi-ping Huang, PhD; and Niels H. Jensen, PhD
• From Jin’s lab: Xin Chen, PhD
• From the CICBDD: center director Stephen V. Frye, PhD
• From the Duke University Medical Center: James B. Duke Professor Marc G. Caron, PhD; associate professor William C. Wetsel, PhD; Meng Chen, PhD; and Sean Peterson
• From the College of Physicians and Surgeons at Columbia University: professor Jonathan A. Javitch, MD, PhD; and Bo Feng, PhD
• From the Center for Combinatorial Chemistry and Drug Discovery at Jilin University in China: professor Xu Bai, PhD, and Xin Che, PhD

The annual award honors researchers who received PhRMA Foundation grants early in their careers and then distinguished themselves through outstanding scientific and/or academic achievements. Roth will be presented with the award April 9 at a meeting of the American Society for Pharmacology and Experimental Therapeutics.

“This award is wonderful for me and for my lab,” says Roth, who is the Michael J. Hooker Distinguished Professor of Pharmacology at the UNC School of Medicine and holds a joint appointment in the UNC Eshelman School of Pharmacy. “Essentially, the PhRMA Foundation makes a bet on young investigators, and no one knows for years whether it was a good bet or not. I am happy I was able to find success and, hopefully, will continue to find it for many years.”

Roth’s work in pharmacology and drug discovery has earned him numerous patents and he has published nearly 300 articles in, among many other publications, Science, Nature, Cell and the New England Journal of Medicine. He has also trained dozens of doctoral and post-doctoral students who have also become leaders in their field.

Much of his research focuses on trying to understand how central nervous system drugs affect the brain’s neurons. The goal is to investigate existing treatments in order to find new treatments and mitigate side effects, particularly for such problems as schizophrenia, depression, bipolar disorder and eating disorders.

“We really don’t understand how most drugs currently used in brain disorders work,” Roth says. “If we can uncover how they exert their therapeutic actions, we hope to find drugs that are more effective. Additionally, if we can understand the side effects of current drugs, we’ll know what molecular targets we have to avoid in making new drugs so they don’t have the side effects.”

Essentially, Roth’s work identifies both good targets for drug development and bad targets to be avoided. In one application of the technique, Roth’s lab identified potentially safe and effective compounds for treating obesity. Those compounds have been out-licensed to biotech companies for commercial development.

In one of his most important research projects, Roth and his team at UNC, along with scientists at the University of California, San Francisco, developed and validated a computer model that can allow researchers to predict likely side effects before a drug is even put into clinical testing.  The method compares the structures of all known drugs for various disease targets to their naturally-occurring binding partners. That comparison has revealed interactions between drugs and their targets that could not be predicted simply by studying their chemical structures.

The researchers developed a computational method that compares how similar the structures of all known drugs are to the naturally occurring binding partners -- known as ligands -- of disease targets within the cell. In a study published this week in Nature, the scientists showed that the method predicts potential new uses as well as unexpected side effects of approved drugs.

Bryan Roth, MD, PhD

“This approach uncovered interactions between drugs and targets that we never could have predicted simply by looking at the chemical structures,” said senior study author Bryan Roth, MD, PhD, a professor in the Division of Medicinal Chemistry and Natural Products and director of the National Institute of Mental Health Psychoactive Drug Screening Program at UNC. “We may now have a way to predict what side effects are likely to occur from treatment before we even put a drug into clinical testing.” 

Roth is also a professor of pharmacology in the UNC School of Medicine and a member of the UNC Lineberger Comprehensive Cancer Center.

Many of the most successful drugs on the market today are being prescribed for ailments that are quite different from the ones they were originally designed to treat. Viagra, for instance, was once intended for coronary heart disease but now is used to combat erectile dysfunction. The discovery of surprising uses of developed drugs can sometimes be the result of serendipity, as unforeseen side effects emerge from clinical trials. In the past, researchers have tried to predict drug interactions by looking for chemical similarities among the possible targets of pharmaceutical compounds.

However, some drug targets which look very similar to one another bind very different ligands, and some targets that don't have any obvious similarity bind similar ligands, says Brian Shoichet, PhD., co-senior study author and professor of pharmaceutical chemistry at UCSF. “So if instead we were to organize targets by the ligands they recognize, it could reveal different patterns than traditional approaches, and illuminate new opportunities for drugs to bind to unexpected targets.”

A team of researchers led by Roth and Shoichet did just that, comparing the structures of 3,365 FDA-approved and investigational drugs against the structures of hundreds of targets, defining each target by its ligands. They then honed in on thirty of the strongest predictions, validating the actual physical interactions between the drugs and targets in wet laboratory experiments.

In one of their follow-up experiments, the scientists investigated the molecular targets of the hallucinogenic substance dimethyltrytamine (DMT), which had previously been postulated to act through a site known as the sigma-1 receptor. Using the computational approach, Roth and colleagues found that DMT had a high affinity for serotonin receptors, including the binding site for LSD, another hallucinogen.

They also showed that the substance is hallucinogenic in normal mouse models but not in ones lacking the serotonin receptor. Roth says the power of their approach is it can be used to uncover the real targets of pharmaceutical compounds quickly and efficiently, and will probably lead to a greater understanding of the many molecular targets of each drug.

“Drugs are not as selective as we once thought,” said Roth, who is also a professor in the School of Pharmacy’s medicinal chemistry and natural products division. “It turns out that the most non-selective drugs are frequently the most effective for complex diseases. Rather than ‘magic bullets,’ we need to come up with ‘magic shotguns’ that hit more than one molecular target at a time. We could use this computational approach to identify the drugs that hit the right targets and miss the wrong ones.”

Study co-authors from UNC include Vincent Setola, research associate professor; Atheir Abbas, former graduate student; Sandra J. Hufeisen, senior research assistant; Niels H. Jensen, research associate; Michael B. Kuijer, research technician; Roberto C. Matos, research technician; Thuy B. Tran, research technician; Ryan Whaley, research technician; and Richard A. Glennon.  The paper’s first author is Dr. Michael Keiser, from the UCSF side of the collaboration.  Also from UCSF were Drs. John Irwin, Christian Laggner and Jerome Hert, and PharmDs Kelan Thomas and Douglas Edwards.

Funding for the studies at UNC and at UCSF came from the National Institutes of Health.

Bryan Roth, MD, PhD

• Research

Bryan Roth, MD, PhD, a professor at the UNC School of Pharmacy, has received a Distinguished Investigators Award from the National Alliance for Research on Schizophrenia and Depression, the largest donor-supported organization in the world that supports research on brain and behavior disorders.

NARSAD awarded eleven Distinguished Investigators grants this year from a pool of 160 applicants. The one-year, $100,000 grants will support research with the greatest potential to lead the field forward in its understanding and treatment of serious mental illness.

Roth is using new methodology recently invented in his lab to create mice with specially engineered characteristics, with which he hopes to shed new light on the neuronal pathways of schizophrenia. His work will help provide information for developing screening campaigns to identify new drugs for schizophrenia and related disorders.

Roth is in the School’s Division of Medicinal Chemistry and Natural Products and holds a joint appointment in the Department of Pharmacology at the School of Medicine. He is also the director of the National Institutes of Mental Health Psychoactive Drug Screening Program, which provides screening of novel psychoactive compounds for pharmacological and functional activity at cloned human or rodent CNS receptors, channels, and transporters.

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