Biotech, Pharma, & VCs Offer Rare Disease Patient Groups Some Advice

Today’s issue examines the surge of interest in rare disease drugs, which in the past few years have attracted significant interest from biotech firms, big pharma, and venture capitalists alike. In addition to exploring the business and policy drivers behind increased investment in orphan drugs, the multi-part story looks at the critical role patient organizations play in drawing attention to rare diseases. As such, it seemed worth highlighting advice from various stakeholders on what patient groups can do to entice drug developers to work on their disease: —Organize yourselves. Find as many patients as possible, and establish a registry that will make it easy for a drug firm to begin a clinical trial. “Beginning to identify people, getting them into a registry, and collecting natural history data is one of the most valuable things a developer can have when they’re thinking about a program,” says Genzyme’s CEO David Meeker. “Among the most helful things that patient advocates can do is to help us to understand the natural history of disease,” agrees Kevin Lee, CSO of Pfizer’s rare disease unit. “Without that understanding of how the disease progresses, and what the endpoints can be, its almost impossible to do drug development.” –Find a way to collaborate with one another. In even the smallest of diseases, patient groups tend to proliferate. And while its natural and understandable for advocates to want to do all they can to help their own child or family member, it can lead to duplicative efforts. The disparate groups can also make it tougher for drug developers to access. “We all need to give everybody a lot of space here to do what they think is best, but in an optimal world, there are tremendous advantages to being coordinated,” Meeker says. —Be connectors. Patient organizations have the amazing ability to bring together academics who had previous not collaborated. “What I have found over and over again is that patient advocates know the investigators in their field far better than the investigators themselves do,” says Christopher Austin, director of NIH’s National Center for Advancing Translational Science (NCATS). “They can be instrumental there.” —Get the right researchers interested. Often only a handful of academic researchers are working on a given rare disease, and drug developers say attracting new scientists into the field, while also giving careful consideration about who to fund is key. Patient groups should look for someone who can use advocacy funds to attract larger grants. “If they can get some grant support, you’ll get more done,” says Emil Kakkis, CEO of Ultragenyx. “If they can’t get any grant support, you’ll have to wonder if it was just...

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Heptares solves first X-ray structure of Family B GPCR, but full details not yet public
Sep17

Heptares solves first X-ray structure of Family B GPCR, but full details not yet public

In what might be the year’s biggest molecular teaser, Heptares Therapeutics has announced that it has solved the first X-ray crystal structure of a G-protein coupled receptor in the Family B subclass. The work provides the first structural insights into a protein family that includes sought-after drug targets such as GLP-1 for diabetes and CGRP for migraine. Largely because of that drug discovery relevance, however, Heptares is choosing to keep its structure somewhat close to the vest. Officials presented views of the structure, of a GPCR called Corticotropin Releasing Factor (CRF-1) receptor, at conferences on Friday and Monday. But Heptares CEO Malcolm Weir says his team has no immediate plans to publish the structure or to deposit coordinates into the repository known as the Protein Data Bank. The structure, Weir says, is another success for Heptares’ GPCR stabilizing technology, StaR. The technique involves targeted mutations that help to trap a GPCR in a single biologically-relevant state. In the case of CRF-1, Weir says, the stabilized receptor is captured in the “off” state. The structure itself, which is at a resolution of 3 Ångstroms, has the 7-helix membrane-spanning structure typical of GPCRs. However, CRF-1’s architecture is rather different from receptors in Family A, the only GPCR family for which X-ray structures had been available until now, Weir says. “The overall shape of the receptor looks different, the orientation of the helices looks different, and there are detailed differences within helices that are at analogous positions in Family A receptors,” he says. He notes that there are differences in helices 6 and 7, which undergo important motions during GPCR activation. “This is an important breakthrough, although fine details of the structure and release of coordinates may still be some time away,” says Monash University’s Patrick Sexton, an expert in Family B GPCRs who was at Friday’s talk. The structure, he says, confirmed researchers’ expectations that the major differences in membrane-spanning helices between Family A and Family B receptors would occur on the extracellular side. “There was a very open and relatively deep extracellular binding pocket, with the receptor having a ‘V’ shaped appearance,” he says. This open pocket likely contributes to medicinal chemists’ difficulties obtaining high affinity small molecule ligands for Family B receptors, he suggests. That open pocket might be involved in another Family B GPCR mystery, according to Roger Sunahara, also in attendance Friday, who studies GPCRs’ molecular mechanisms at the University of Michigan, Ann Arbor. All Family B GPCRs, including CRF-1, have a large domain at their amino-terminus that contains large portions of their ligand binding sites. That domain was not included in this structure, he says, but...

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Antibacterial Resistance – Learning Bacterial Tricks
Mar23

Antibacterial Resistance – Learning Bacterial Tricks

Virulent bacteria are growing increasingly resilient against our best antibiotics. Each day seems to bring a new story: MRSA outbreaks, resistant salmonella, or tough-to-treat tuberculosis. Just last week, World Health Organization director-general Dr. Margaret Chan delivered an address in Copenhagen, where she cautioned: “We are losing our first-line antimicrobials . . . in terms of replacement antibiotics, the pipeline is virtually dry. The cupboard is nearly bare.” (Click here for The Haystack’s past coverage of the development of new antibacterials). Why have our drugs stopped working? Recent research from St. Jude’s (Science, 2012, 1110) attempted to answer that question. Using X-ray crystallography, a technique used to see structures at the atomic level, the researchers were able to capture a critical moment when a drug binds to DHPS, its bacterial enzyme target. The scientists could then predict how bacteria evolve to dodge further biocidal bullets. The antibacterial medicines caught in the act by the St. Jude’s researchers are the sulfa drugs (see right), former front-line treatments many doctors push to the bottom of treatment regimens, due to increasingly resistant bacterial strains. Researchers knew resistance had something to do with the drugs’ mechanism of action; sulfa drugs mimic the binding of PABA – para-aminobenzoic acid, a compound found in many sunscreens (Chemical Note: PABA occurs naturally as bacterial vitamin H1, and can also be found in yeast and plants. Chemists often borrow naturally-occurring compounds for industrial uses; two prominent examples are vanillin and Vitamin C). Disruption of this PABA binding shuts down bacterial DNA replication, stopping reproduction. Before now, however, no one had succeeded in growing crystals of the active site that actually showed the drugs interacting with the enzymatic intermediate. Let’s take one more step back: how does PABA attach itself? The enzyme we’re discussing, DHPS, catalyzes bond formation between PABA and intermediates known as pterins (see picture, left). Earlier researchers believed that this molecular hook-up operated by an SN2 mechanism, a reaction where the PABA kicks out a small piece of the pterin to form a new C-N bond. We chemists would say that SN2 means concerted bond formation, meaning that PABA would bind at the same time as the leaving group (OPPi), well, leaves. Turns out that picture’s not quite right: it’s more SN1-like, which means that the pterin first forms a positively-charged, enzyme-stabilized species! As you can imagine, this is no small feat, since the reaction works at physiological pH, in water, which could hydrate the intermediate (but doesn’t). Nope – instead, this charged molecule sits around waiting for a PABA – or a sulfa drug – to bind to it. When PABA binds, the complex exits...

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Neuroscience Outtakes Part 2: Vanderbilt’s Jeff Conn on the Role of Academic Labs

On Monday, we highlighted outtakes from our interview with Michael Ehlers, Pfizer’s CSO for neuroscience research, for our story on the state of neuroscience R&D. Today, we wanted to offer a view from academia: Jeff Conn is head of the Vanderbilt Center for Neuroscience Drug Discovery, which in the past several years has generated a number of CNS drug candidates. While Ehler is focused on the growing body of genetic information that could pave the way for new neuroscience targets, Conn’s lab is taking a somewhat different approach. By scouring the literature for evidence–in humans–of a molecule or target’s activity, the lab then sinks substantial resources into understanding the basic biology driving that activity and designing molecules to exploit it. In depression, for example, R&D has been stalled by a lack of new targets. But Conn’s lab is intrigued by studies showing that ketamine, an animal tranquilizer (and club drug), swiftly and effectively reduces the symptoms of major depressive disorder. “When I talk to scientists at Vanderbilt, its an approach they’re using for their most refractory patients,” Conn says. A laundry list of side effects makes wider use of ketamine improbable. As such, Conn’s lab is looking at ways to design molecules that produce the same kind of results on depression without the adverse effects. Conn, a former Merck researcher, also discussed ways that discovery efforts inside academia can build a scientific case for CNS programs that pharma might otherwise overlook. Vanderbilt scientists spend “twice as much effort in basic science than for the drug discovery itself, and to me, that’s absolutely critical,” Conn says. When the team finds that molecules have different profiles in vitro, they spend a lot of time trying to understand how that will translate into adverse effects in vivo. “In pharma, you have to stay on such a narrow, direct path, that you have to ignore all that,” Conn says. In the academic lab, researchers take a longer, more methodical approach that entails optimizing many different molecules, then putting those in animals to understand what properties a final drug candidate needs to have. That approach has enabled Vanderbilt scientists to tackle drug targets that have tripped up industry. “mGluR5 is a good example where, early on, we started seeing different properties of molecules in vitro,” he says. “Instead of putting blinders on and moving forward or ignoring it,” an avenue industry scientists are often forced to take, “we deliberately put a lot of effort into optimizing those properties.” As a result, the Vanderbilt group and its collaborator, J&J, recently moved forward what Conn calls “very safe” schizophrenia drug candidates targeting mGlur5. “I don’t think...

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Wither Neuroscience R&D? Pfizer’s Ehlers Doesn’t Think So

In this week’s issue, I look at the perceived exodus by pharma companies from neuroscience R&D. Between AstraZeneca’s recent cutbacks, the closure of Novartis’ neuroscience research facility in Basel, and earlier moves by GSK and Merck, industry watchers are understandably worried that the neuroscience pipeline will dry up. One person who isn’t worried is Michael Ehlers, Pfizer’s chief scientific officer for neuroscience research. Ehlers came to Pfizer a year and a half ago from Duke, with the explicit mission to revamp how the company finds and develops drugs for brain diseases. The scientist is convinced that the field is ripe for new and better drugs, and that by staying in the game, Pfizer will be in a good position to capitalize on what he believes will be a healthy flow of new discoveries. Many drug companies argue that the risk in neuroscience simply doesn’t justify the investment. The overarching sentiment is that the brain is still a black box: good targets are few and far between; clinical trials are long and unpredictable; regulatory approval is tough; and generic competition is plentiful. For many big pharma firms, the math just doesn’t add up. “I personally don’t find that calculus to give you the total picture,” Ehlers says. Shifting resources away from neuroscience to focus on areas like oncology, where the environment looks favorable—clear clinical trial endpoints, the opportunity for fast-track approval, an easier chance for reimbursement from payors—only makes sense in the short term, Ehlers says. But that thinking “is short sighted as to where the fundamental state of biology is in neuroscience,” he says. Why is Ehlers so encouraged about a field that so many are walking away from? He believes that neuroscience is poised to benefit from the kind of genetic links that generated so many targets—and eventually so many targeted-drugs—in oncology. “There is going to be kind of a revolution in the next five years—it’s not going to be tomorrow…but you have to think about that inflection of opportunity over the five-to-ten year time horizon.” To take advantage of each new genetic clue, Ehlers has revamped Pfizer’s approach to neuroscience R&D. As this week’s story explains: In the past, big pharma often gave its scientists a mandate to work in areas such as Alzheimer’s or schizophrenia, regardless of tractable drug targets. Now at Pfizer, Ehlers says, his team is “indication agnostic.” Any program that Pfizer undertakes must have a critical mass of biological knowledge—for example, human genetics, human phenotyping, and evidence of dysfunctional neurocircuits—to convince Ehlers it’s worth pursuing. “We start there,” he says. “That hasn’t always been the case.” Moreover, Pfizer no longer relies on mouse...

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Exploring Rational Drug Design
Feb17

Exploring Rational Drug Design

Medicinal chemists strive to optimize molecules that fit snugly into their proposed targets. But in the quest for potency, we often overlook the local physics that govern drugs’ binding to these receptors. What if we could rationally predict which drugs bind well to their targets? A new review, currently out on J. Med. Chem. ASAP, lays out all the computational backing behind this venture. Three computational chemists (David Huggins, Woody Sherman, and Bruce Tidor) break down five binding events from the point-of-view of the drug target: Shape Complementarity, Electrostatics, Protein Flexibility, Explicit Water Displacement, and Allosteric Modulation….whew! Note: Before we dive into this article, let’s clarify a few terms computational drug-hunters use that bench chemists think of differently: ‘decoy’ – a test receptor used to perform virtual screens; ‘ligand’ – the drug docking into the protein; ‘affinity / selectivity’ – a balance of characteristics, or how tightly something binds vs. which proteins it binds to; ‘allosteric’ – binding of a drug molecule to a different site on an enzyme than the normal active site. Regular readers and fans of compu-centric chem blogs such as The Curious Wavefunction and Practical Fragments will feel right at home! We’ll start at the top. Shape complementarity modeling uses small differences in a binding pocket, such as a methylene spacer in a residue (say, from a Val to Ile swap) to dial-in tighter binding between a target and its decoy. The authors point out that selectivity can often be enhanced by considering a drug that’s literally too big to fit into a related enzymatic cavity. They provide several other examples with a ROCK-1 or MAP kinase flavor, and consider software packages designed to dock drugs into the “biologically active” conformation of the protein. Electrostatic considerations use polar surface maps, the “reds” and “blues” of a receptor’s electronic distribution, to show how molecular contacts can help binding to overcome the desolvation penalty (the energy cost involved in moving water out and the drug molecule in). An extension of this basic tactic, charge optimization screening, can be used to test whole panels of drugs against dummy receptors to determine how mutations might influence drug binding. Because target proteins move and shift constantly, protein flexibility, the ability of the protein to adapt to a binding event, is another factor worth considering. The authors point out that many kinases possess a “DFG loop” region that can shift and move to reveal a deeper binding cavity in the kinase, which can help when designing binders (for a collection of several receptors with notoriously shifty binding pockets – sialidase, MMPs, cholinesterase – see p. 534 of Teague’s NRDD review). But these...

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