A novel approach to identifying potential anticancer drug combinations revealed that pairing cholesterol-reducing drugs called statins with cyclin-dependent kinase inhibitors might provide an effective approach to treating intractable melanomas driven by mutations in the NRAS and KRAS gene.
David F. Stern, Ph.D., professor of pathology at Yale University School of Medicine in New Haven, Conn., and colleagues reported these data in Cancer Discovery, a journal of the American Association for Cancer Research.
"The identification of gene mutations that drive specific subsets of cancers has had a major beneficial impact on treatments for these patients. But, such mutations can only be identified for some cancers. Some patients who have a specific cancer-driving genetic mutation never respond to the matching drug, while nearly all those who initially respond eventually become resistant to the effects of the drug and their cancers relapse," said Stern.
For this reason, Stern and colleagues reasoned that using drug combinations may be necessary to address the problem of drug resistance and enable effective treatment of cancers driven by signaling molecules that currently cannot be targeted, such as RAS.
They developed an in vitro, high-throughput screen to test the effectiveness of anticancer drugs, alone and in pairs, against three types of melanoma cell lines: those driven by mutations in the RAS gene (representing approximately 20 percent of human melanomas), those driven by mutations in the BRAF gene (40 to 50 percent of melanomas) and those without mutations in either the RAS or BRAF genes.
Through analysis of 150 drugs as single agents, Stern and colleagues narrowed their pool to 40 drugs for combination testing. Melanoma cell lines driven by BRAF and RAS were sensitive to different combinations of drugs. Some combinations that killed BRAF-driven melanoma cell lines were also effective against BRAF-driven melanoma cell lines resistant to a single agent used to treat patients with melanoma tumors characterized by BRAF gene mutations, and these combinations may prove to be helpful in preventing or managing resistance to these agents.
"Perhaps the most interesting observation was that several drug combinations that included a statin, a drug class used clinically to lower cholesterol, killed RAS-driven melanoma cell lines, given the lack of success in treating such cancers," said Stern.
One statin combination that showed efficacy in vitro, simvastatin plus flavopiridol, an inhibitor of proteins called cyclin-dependent kinases that activate cell division, also worked in vivo substantially reducing the growth of a RAS-driven human melanoma cell line transplanted into mice.
"These agents may be extremely useful as partner agents in combination therapy. Since multiple cyclin-dependent kinase inhibitors are already in human clinical trials, there may be a short path to testing the combination of a statin plus a cyclin-dependent kinase inhibitor in patients with RAS-driven melanoma," said Stern. "There is a great need for drugs to treat cancers driven by RAS. RAS proteins are inappropriately active in up to a third of all human cancers, including melanoma and lung and pancreatic cancers."
"This brings up the important point that our high-throughput screening approach is applicable to other types of cancer, including lung and pancreatic cancer," he added. "A major challenge is in picking the appropriate agents for combination screening, since with multiple doses per agent, the scale of a screen needed for all combinations grows rapidly. This requires careful evaluation of single agents, and analytical methods for choosing the best candidates for follow-up in combinations. For our work, the relatively small number of genetic subtypes was very important, so this system provides a great starting point for investigation of carcinomas (lung, pancreatic cancer, breast cancer), which are genetically more complex."
An international research collaboration led by scientists at the University of North Carolina School of Medicine and the University of Dundee, in the U.K., have developed a way to efficiently and effectively make designer drugs that hit multiple protein targets at once. This accomplishment, described in the Dec. 13, 2012 issue of the journal Nature, may prove invaluable for developing drugs to treat many common human diseases such as diabetes, high blood pressure, obesity, cancer, schizophrenia, and bi-polar disorder.
These disorders are called complex diseases because each have a number of genetic and non-genetic influences that determine susceptibility, i.e., whether someone will get the disease or not.
"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," said study co-leader, Brian L. Roth, MD, PhD, Michael J. Hooker Distinguished Professor of Pharmacology in the UNC School of Medicine, professor in the Division of Chemical Biology and Medicinal Chemistry in the UNC Eshelman School of Pharmacy, and director of the National Institute of Mental Health Psychoactive Drug Screening Program.
In complex neuropsychiatric conditions, infectious diseases and cancer, Roth points out that for the past 20 years drug design has been selectively aimed at a single molecular target, but because these are complex diseases, the drugs are often ineffective and thus many never reach the market.
Moreover, a drug that acts on a single targeted protein may interact with many other proteins. These undesired interactions frequently cause 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 said.
The new way involves automated drug design by computer that takes advantage of large databases of drug-target interactions. The latter 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 in the Division of Biological Chemistry and Drug Discovery, College of Life Sciences, at the University of Dundee, in Scotland, 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 disease.
The study team experimentally tested 800 drug-target predictions of the computationally designed compounds; of these, 75 percent were confirmed in test-tube (in vitro) experiments.
Drug to target engagement also was confirmed in animal models of human disease. In a mouse model of attention deficit hyperactivity disorder (ADHD), mice missing a particular dopamine receptor engage in recurrent aberrant behaviors similar to what is seen in ADHD: distractibility and novelty seeking. "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. Distractibility and novelty seeking also are behavioral features in these animals. And 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. These, too, were tested successfully in live animals.
According to Roth, pharmaceutical company chemists had suggested that the objective of a drug hitting multiple targets simultaneously is impossible and unlikely to succeed. "Here we show how to efficiently and effectively make designer drugs that can do that."
Along with Roth, the study's 21 co-authors include the following from UNC: Vincent Setola, Xi-Ping Huang and Maria F. Sassano. Other co-authors are from University of Dundee, Dundee, U.K.; Duke University Medical School, Durham, N.C.; Clinical Research Institute of Montreal, Montreal, Quebec, Canada; and the Swiss Federal Institute of Technology in Lausanne, Switzerland.
Part of the funding for the research comes from the National Institute of Health grants supporting drug discovery receptor pharmacology.
A newly found understanding of receptor signaling may have revealed a better way to design drugs. A study from Nationwide Children's Hospital suggests that a newly identified group of proteins, alpha arrestins, may play a role in cell signaling that is crucial to new drug development. The study appears in PLOS ONE.
More than one-third of drugs on the market work by targeting G protein-coupled receptors that control how cells communicate and function. With many hundreds of members, G protein-coupled receptors are the largest family of signaling receptors throughout the body.
Once a cell's G protein-coupled receptor binds with a natural ligand or a drug, intracellular G proteins and beta arrestins independently mediate various signals. Immediately following, beta arrestins block further signaling of G proteins and recruit proteins to remove the receptor to halt cell signaling. Those receptors can subsequently recycle to the cell surface or be destroyed.
"Receptor down regulation caused by beta arrestins can interfere with drug efficacy because the G protein-coupled receptor that the drug has been targeting is absent from the cell surface," said Carlos E. Alvarez, PhD, principal investigator in the Center for Molecular and Human Genetics at The Research Institute at Nationwide Children's Hospital and lead study author. "This is why patients who are prescribed long-term medication can become drug-tolerant and require higher and higher doses."
In some cases, a drug's ability to trigger beta arrestin effects and block G protein signaling is preferential. Take beta blockers, for example. As the name suggests, beta blockers interfere with the binding to the receptor for epinephrine and other stress hormones, weakening the hormones' effects and therefore being useful in treating irregular heartbeats, prevention of second heart attacks, hypertension and other conditions. Screening has revealed that the beta blocker Carvedilol may be the most ideal for treatment of heart conditions as it reduces the cardiotoxic effects of G protein signaling, while increasing the cardioprotective effects of beta arrestin signaling.
Yet, it seems that beta arrestins may only be part of the cell signaling story. In 2008, Dr. Alvarez discovered a subfamily of arrestins that his team named alpha arrestins. In the current study, Fortune Shea in Dr. Alvarez's lab used biochemical and imaging approaches to further identify the role alpha arrestins play in cell signaling.
He found that alpha arrestins respond to receptor binding and recruit enzymes that chemically modify the receptor to initiate aspects of down regulation. These effects occur in the first five minutes after the receptor is bound, the same time frame that beta arrestins are known to have roles in triggering down regulation. The team is also the first to find that alpha arrestins function coordinately with beta arrestins.
"Our findings suggest that alpha arrestins, like beta arrestins, are ubiquitous regulators of G-protein coupled receptor signaling," says Dr. Alvarez. "It seems that like beta arrestins, alpha arrestins could have great pharmacological relevance."
A major effort in pharmacology is to develop drugs with functional selectivity that either target G protein or beta arrestin signaling effects. Dr. Alvarez foresees alpha arrestins becoming a big player in the refining of such efforts.
"Just as has been discovered with beta blockers and beta arrestin, I expect we'll find drugs that also have significant alpha arrestin effects," he says. "I believe that targeting alpha arrestins will allow us to develop compounds that are more effective and have reduced side effects," says Dr. Alvarez.
Shea F, Rowell J, Li Y, Chang TH, Alvarez C. Mammalian alpha arrestins link activated seven transmembrane receptors to Nedd4 family E3 ubiquitin ligases and interact with beta arrestins. PLOS ONE.
People who use aspirin regularly for at least 10 years run a small risk of developing a potentially blinding condition known as age-related macular degeneration, researchers report.
In the United States, an estimated 19 percent of adults report using aspirin regularly and aspirin use increases with age, the University of Wisconsin researchers noted. Meanwhile, the incidence of age-related macular degeneration is increasing as the population ages, making this association important to examine, they added.
"There are a lot of people taking aspirin for cardioprotection," said lead researcher Dr. Barbara Klein, from the university's School of Medicine and Public Health.
"Heart attacks have a high risk of death, so the question is: is it worth the possible increase in [risk for] age-related macular degeneration, compared to the risk of getting a heart attack?" she said.
"These data do not suggest that people should stop taking aspirin for cardioprophylaxis," Klein said. "One should not alter aspirin use based on these findings."
The report was published in the Dec. 19 edition of the Journal of the American Medical Association.
For the study, Klein's team collected data on almost 5,000 men and women who took part in the Beaver Dam Eye Study. Participants had their eyes checked every five years over a 20-year period. In addition, they were asked about their use of aspirin.
Over almost 15 years of follow-up, 512 people developed early macular degeneration and 117 people developed late macular degeneration.
The investigators found that people who took aspirin for 10 years almost doubled their risk for developing macular degeneration, compared with a less than 1 percent risk among people who did not take aspirin.
When the researchers looked specifically at late age-related macular degeneration, they found aspirin users had a 1.4 percent increased risk of developing the condition, compared with a 0.6 percent risk among those who did not take aspirin.
These findings show an association between age-related macular degeneration and aspirin use, and not a cause-and-effect relationship.
Klein noted that the biological mechanism for this association isn't known. If it turns out that there is one, then it might lead to new ways to protect people from heart attacks and strokes, she said.
One expert cautioned that it is too soon to change clinical practice.
"While this observational study suggests there may be an association of long-term aspirin use with age-related macular degeneration, the potential risk was small in absolute terms, [and] the association may not be causal," said Dr. Gregg Fonarow, a professor of cardiology at the University of California, Los Angeles.
Moreover, randomized controlled trials of aspirin use with follow-up as long as 10 years have not shown any increase in the risk of age-related macular degeneration, he said. A randomized, controlled study is one in which people are randomly assigned to different groups: one group receives the treatment and the other does not receive the treatment (the "control" group).
"For most patients, the benefits of regular low-dose aspirin use outweigh the potential risks," Fonarow said. "Individuals prescribed aspirin for primary or secondary cardiovascular prevention should not be concerned or discontinue this beneficial therapy."
For more on aspirin and heart disease, visit the American Heart Association.
The U.S. Food and Drug Administration today approved Iclusig (ponatinib) to treat adults with chronic myeloid leukemia (CML) and Philadelphia chromosome positive acute lymphoblastic leukemia (Ph+ ALL), two rare blood and bone marrow diseases.
Iclusig is being approved more than three months ahead of the product’s prescription user fee goal date of March 27, 2013, the date the agency was scheduled to complete review of the drug application. The FDA reviewed the Iclusig drug application under the agency’s priority review program, which provides for an expedited six-month review for drugs that may provide safe and effective therapy when no satisfactory alternative therapy exists, or offer significant improvement compared to marketed products.
Iclusig blocks certain proteins that promote the development of cancerous cells. The drug is taken once a day to treat patients with chronic, accelerated, and blast phases of CML and Ph+ ALL whose leukemia is resistant or intolerant to a class of drugs called tyrosine kinase inhibitors (TKIs). Iclusig targets CML cells that have a particular mutation, known as T315I, which makes these cells resistant to currently approved TKIs.
“The approval of Iclusig is important because it provides a treatment option to patients with CML who are not responding to other drugs, particularly those with the T315I mutation who have had few therapeutic options,” said Richard Pazdur, M.D., director of the Office of Hematology and Oncology Products in FDA’s Center for Drug Evaluation and Research. “Iclusig is the third drug approved to treat CML and the second drug approved to treat ALL this year, demonstrating FDA’s commitment to approving safe and effective drugs for patients with rare diseases.”
The FDA approved Bosulif (bosutinib) in September 2012 and Synribo (omacetaxine mepesuccinate) in October 2012 to treat various phases of CML. Marqibo (vincristine sulfate liposome injection) was approved in August 2012 to treat Philadelphia chromosome negative ALL.
Iclusig is being approved under the agency’s accelerated approval program, which provides patients earlier access to promising new drugs while the company conducts additional studies to confirm the drug’s clinical benefit and safe use. The therapy is being granted an orphan product designation because it is intended to treat a rare disease or condition.
Iclusig’s safety and effectiveness were evaluated in a single clinical trial of 449 patients with various phases of CML and Ph+ ALL. All participants were treated with Iclusig.
The drug’s effectiveness was demonstrated by a reduction in the percentage of cells expressing the Philadelphia chromosome genetic mutation found in most CML patients, major cytogenetic response (MCyR). Fifty-four percent of all patients and 70 percent of patients with the T315I mutation achieved MCyR. The median duration of MCyR had not yet been reached at the time of analysis.
In accelerated and blast phase CML and Ph+ ALL, Iclusig’s effectiveness was determined by the number of patients who experienced a normalization of white blood cell counts or had no evidence of leukemia (major hematologic response or MaHR). Results showed:
- 52 percent of patients with accelerated phase CML experienced MaHR for a median duration of 9.5 months;
- 31 percent of patients with blast phase CML achieved MaHR for a median duration of 4.7 months; and
- 41 percent of patients with Ph+ ALL achieved MaHR for a median duration of 3.2 months.
Iclusig is being approved with a Boxed Warning alerting patients and health care professionals that the drug can cause blood clots and liver toxicity. The most common side effects reported during clinical trials include high blood pressure, rash, abdominal pain, fatigue, headache, dry skin, constipation, fever, joint pain, and nausea.
Iclusig is marketed by ARIAD Pharmaceuticals, based in Cambridge, Mass. Bosulif is marketed by New York City-based Pfizer, and Synribo is marketed by Frazer, Pa.-based Teva Pharmaceuticals. Marqibo is marketed by Talon Therapeutics Inc. based in South San Francisco, Calif.
A study published today online in The Journal of Experimental Medicine has identified the population of CD4 T cells serving as the major reservoir for HIV infected cells and as the primary cell site for HIV replication and production in infected patients. The study was led by Prof. Giuseppe Pantaleo and Dr. Matthieu Perreau at the Division of Immunology and Allergy and at the Swiss Vaccine Research Institute, Lausanne University Hospital, Lausanne, Switzerland.
CD4 T cells are known to be the primary target of HIV. The CD4 T cells serving as reservoir for HIV infection and as primary site for HIV replication and production are not present in the blood and are exclusively found in the lymphoid tissues in a region called germinal centers. These CD4 T cells are called ˜T follicular helper' (Tfh) cells: they represent about 2% of the total CD4 T cells residing in the lymphoid tissues and are in close contact with B cells and help B cells to mature and produce antibodies.
“This is a major discovery for the HIV field; we have finally identified the cell population predominantly responsible for supporting active HIV replication and production,” says Prof. Pantaleo. “We have also provided evidence that the Tfh cells are likely to be responsible for residual virus replication in patients effectively treated with antiretroviral therapy.”
“HIV-infected Tfh cells hide themselves within the germinal centers where they are difficult to be reached by HIV-specific cytotoxic CD8 T cells, which generally are poorly present in germinal centers,” says Dr. Perreau.“Therefore, germinal centers represent a sanctuary for HIV replication in Tfh cells.”
“The identification of the major HIV CD4 T cell reservoir will be instrumental in developing therapeutic strategies to selectively target HIV infected Tfh cells,” says Prof. Pantaleo. “The elimination of HIV infected Tfh cells will represent a critical therapeutic strategy to achieve HIV functional cure, i.e. control of HIV replication in the absence of antiretroviral therapy, and potentially HIV eradication.”
T cells: Small lymphocytes that play a major role in cellular immunity. T cells mature in the thymus and have the ability to recognize specific antigens through the receptors expressed at their cell surface. They identify and eliminate incoming microbes such as bacteria and viruses.
CD4 T cells: are a sub-group of small lymphocytes. CD4 T cells in the blood represent 50-60% of human T cells. The CD4 molecule serves as the primary receptor for HIV. HIV causes depletion of CD4 T cells. The depletion of CD4 T cells is associated with increased susceptibility to infection with other infectious agents in the advanced stages of HIV disease.
CD8 T cells: CD8 T cells recognize viral antigens on the surface of HIV-infected cells and are capable of killing virus infected cells.
Reservoir: cell type or anatomical site, where a replication-competent form of HIV can accumulate and persist stably.
About Lausanne University Hospital
The Centre hospitalier universitaire vaudois (CHUV) is one of the five Swiss University Hospitals. Through its collaboration with the Faculty of Biology and Medicine of the University of Lausanne, the CHUV plays a leading role in Europe in medical care, research and education.
About the Swiss Vaccine Research Institute (SVRI)
The SVRI is a partnership of five research institutes in Switzerland. The SVRI was created in 2007 in Lausanne and is supported by the Swiss Secretariat of Education and Research. Its primary objective is to develop effective preventive vaccine strategies and therapeutic vaccine interventions for infectious diseases and for cancer. SVRI plays an instrumental role in linking basic research to translational research. SVRI's research program targets primarily HIV/AIDS, malaria, tuberculosis, as well as the emerging influenza pandemic threat. SVRI benefits also from ongoing efforts in the area of cancer vaccine research. The SVRI hosting house is the Lausanne University Hospital (Lausanne, Switzerland).
Allakos Inc. announced today that it has completed a $32 million Series A preferred stock financing led by Novo Ventures with participation from Alta Partners, RiverVest Venture Partners and the Roche Venture Fund. Peter Moldt , PhD., Partner at Novo Ventures, Robert Alexander , PhD., Director at Alta Partners and John McKearn PhD., Managing Director at RiverVest Venture Partners, will join the Board of Directors.
Commented Dr. Moldt: "We believe that Allakos' innovative approach to developing antibody-based therapeutics represents a large and important therapeutic and commercial opportunity, founded upon a strong scientific rationale and supported by a respected management team with deep experience in therapeutic antibody development. We are pleased to join with these other distinguished investors in supporting their progress."
"We very much appreciate the confidence placed in our company by our Series A investors," said Christopher Bebbington , DPhil, Founder and Chief Executive Officer of Allakos. "Our therapeutic antibodies are designed to work through novel mechanisms of action, to have significant safety and efficacy advantages and to have potential in multiple, high-value markets, including large therapeutic areas as well as orphan indications. With these proceeds, we are now well positioned to advance our lead program towards meaningful near-term milestones."
SOURCE Allakos Inc.
Drugs that are used in the clinic to treat some forms of breast and kidney cancer and that work by inhibiting the signaling molecule mTORC1 might have utility in treating some of the more than 15 percent of human cancers driven by alterations in the Myc gene, according to data from a preclinical study published in Cancer Discovery, a journal of the American Association for Cancer Research.
"More than 1 million people diagnosed with cancer each year have a tumor driven by alterations in the Myc gene," said Grant A. McArthur, M.D., Ph.D., professor of translational research at the Peter MacCallum Cancer Centre in Melbourne, Australia. "However, it has proven impossible to develop drugs that effectively target Myc.
"One of Myc's functions is to regulate cell growth. Because mTORC1 is also a regulator of cell growth, we hypothesized that inhibiting mTORC1 with the drug everolimus might suppress Myc-driven tumor initiation and growth."
McArthur and his colleagues tested their hypothesis in a mouse model of Myc-driven lymphoma and found that treatment with everolimus provided strong protection against disease: only four of 33 mice treated with everolimus developed lymphoma, while 22 of 34 mice treated with placebo developed the disease.
In addition, treatment with everolimus led to tumor regression and significantly improved survival compared with placebo in mice with established lymphomas. However, all of these mice eventually relapsed as a result of the growth of lymphoma cells resistant to the effects of everolimus.
"These data confirmed our hypothesis that mTORC1 inhibition could suppress Myc-driven tumor initiation and growth," said McArthur. "The surprise was found in how mTORC1 inhibition led to tumor regression. We had expected that it would trigger cancer cells to die by a cellular process known as apoptosis, but we found that this was not the case."
Detailed analysis of the tumors indicated that everolimus caused tumor regression by inducing cellular senescence.
According to McArthur, normal cells protect themselves when cancer-driving genes are switched on is by entering a state called senescence. When cancers develop, they have found ways to overcome this safeguard. "Our data indicate that one way in which cancers bypass senescence, in particular senescence induced by Myc, is through a signaling pathway involving mTORC1," he said.
Resistance to everolimus treatment in mice with established lymphomas was associated with loss of the function of p53, a protein known to help suppress tumor formation and growth.
"The loss of effectiveness of everolimus therapy against lymphoma cells deficient in p53 function has important clinical implications," said McArthur. "Everolimus could be a useful new string to the bow for clinicians treating patients with Myc-driven cancers, in particular B cell lymphomas, but that it would be helpful only to those patients with functional p53."
Source: American Association for Cancer Research