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Liveblogging First-Time Disclosures of Drug Structures from #ACSNOLA

Bookmark this page now, folks. On Wednesday, April 10, I will be here, liveblogging the public debut of five drug candidates’ structures. The “First Time Disclosures” Session at the ACS National Meeting in New Orleans runs from 2PM-4:55PM Central time. I am not able to conjure up a permalink to the session program, so here’s a screengrab instead.
NOLAblog-program
1:20PM I’m in hall R02, where the session’s set to begin in about 40 minutes. Found a seat with a power outlet nearby, so I’m good to go!
2:29PM
IMG_3813
BMS-906024
Company: Bristol-Myers Squibb
Meant to treat: cancers including breast, lung, colon, and leukemia
Mode of action: pan-Notch inhibitor
Medicinal chemistry tidbit: The BMS team used an oxidative enolate heterocoupling en route to the candidate– a procedure from Phil Baran’s lab at Scripps Research Institute. JACS 130, 11546
Status in the pipeline: Phase I
Relevant documents: WO 2012/129353
3:02PM
IMG_3810
LGX818
Company: Novartis Institutes for Biomedical Research and Genomics Institute of the Novartis Research Foundation
Meant to treat: melanoma with a specific mutation in B-RAF kinase: V600E
Mode of action: selective mutant B-RAF kinase inhibitor
Status in the pipeline: Phase Ib/II
Relevant documents: WO 2011/023773 ; WO 2011/025927
3:47PM
IMG_3812
AZD5423
Company: AstraZeneca
Meant to treat: respiratory diseases, in particular chronic obstructive pulmonary disease
Mode of action: non-steroidal glucocorticoid receptor modulators
Medicinal chemistry tidbit: This compound originated in part from a collaboration with Bayer Pharma.
Status in the pipeline: Phase II
Relevant documents: WO 2011/061527 ; WO 2010/008341 ; WO 2009/142568
4:17PM
IMG_3811
Birinapant (formerly known as TL32711)
Company: TetraLogic Pharmaceuticals
Meant to treat: cancer
Mode of action: blocks the inhibitor of apoptosis proteins to reinstate cancer cell death
Status in the pipeline: Phase II
Relevant documents: US 8,283,372
5:00PM
IMG_3814
MGL-3196 (previously VIA-3196)
Company: Madrigal Pharmaceuticals, acquired from VIA Pharmaceuticals, licensed from Roche
Meant to treat: high cholesterol/high triglycerides
Mode of action: mimics thyroid hormone, targeted to thyroid hormone receptor beta in the liver
Medicinal chemistry tidbit: this molecule was discovered at Roche’s now-shuttered Nutley site.
Status in the pipeline: completed Phase I trials
Relevant documents: WO 2007/009913 ; WO 2009/037172

And that’s it, folks! Watch the April 22nd issue of C&EN for more on this session.

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

GPCR family tree

The new structure adds a new section of GPCR space amenable to computer modeling (big blue circle), a space which includes sought-after drug targets. Previously determined GPCR structures, which are all from the same family, are highlighted in small blue and red circles. Image courtesy Heptares

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 “it would appear that deleted globular N-terminal domain would fit quite nicely into the open pocket.”

The CRF-1 receptor is a drug target for depression and anxiety, but at least one CRF antagonist failed to show benefit compared to placebo in a clinical trial. Weir says the impact of the CRF-1 structure for drug discovery will not necessarily be in CRF-1 drug discovery per se, but in the ability to develop relevant computer models of related targets.

It hasn’t been possible to make accurate models of Family B receptors with Family A information, explains Ryan G. Coleman, a postdoctoral fellow at UCSF who develops GPCR models, but who was not in attendance at the talks. Quality models could streamline small molecule drug discovery for the entire family, he explains. Most of the natural ligands for Family B receptors are long peptides, which are notoriously tough to replace with small molecule drugs.

Experts like Coleman will have to wait for some time to learn about the structure for themselves, unless they happened to have a friend in the audience at Heptares’ talks. It’s not unheard of for there to be a gap of several months to two years between a structure’s announcement and publication.

“We’re delighted to have such an informative structure,” Weir says. “It’s very exciting.” He adds says Heptares is progressing toward a structure of the biggest fish in family B, GLP-1, in the “on” state.

Tetrodotoxin: Why Toxic Is Complicated

(This post was written for the “Our Favorite Toxic Chemicals” blog carnival hosted by Sciencegeist.)

It was a meal Captain James Cook would just as soon have forgotten. The fish, an unfamiliar species, seemed harmless enough. But after just a small taste of its liver, he and two shipmates regretted it.

“We were seized with an extraordinary weakness in all our limbs attended with a numness [sic]…We each of us took a Vomet and after that a Sweat which gave great relief. One of the pigs which had eat the entrails was found dead… When the Natives came on board and saw the fish hanging up, they immidiately [sic] gave us to understand it was by no means to be eat.”

Cook had a rather more dramatic introduction to the lethal chemical tetrodotoxin than I did. I learned about it from a lecture in a windowless room. (Yes, I’ve linked to the original slides, still online after eight years.) That presentation had plenty to make my ears perk up. Highly poisonous. No antidote. Still kills today, because pufferfish, one of the web of creatures that makes tetrodotoxin, gets carved into a delicacy called fugu, and sometimes those knives miss a little bit of the animal’s toxic innards.

We weren’t learning about tetrodotoxin because of its deadliness. Tetrodotoxin, to the organic chemist, is a case study. The lab where I earned my Ph.D. is in the business of making the toughest molecules it can. The lessons teams learned by forging tetrodotoxin from scratch, the idea goes, will be useful in other endeavors. Chemists for decades have argued about whether this is an appropriate way to train students, but suffice to say it’s still the way that most medicinal chemists in pharma get their start.

Tetrodotoxin is different things to different people. To biochemists and neurobiologists, tetrodotoxin, or TTX for short, is a tool for unraveling how pain works. Researchers today know that TTX binds to sodium channel proteins involved with pain pathways in the nervous system.

To those who study the cultures of Haiti, tetrodotoxin evokes something else entirely– the zombie of Haitian tradition.

In the 1980s, ethnobotanist Wade Davis fingered tetrodotoxin as a key ingredient in a powder witch doctors use in voodoo zombie-making rituals. His doctoral thesis, as well as his bestselling book the “The Serpent and the Rainbow”, about the topic eventually became the basis for a movie of the same name.

Davis’s results came under fire from the medical and scientific community. Another team’s measurements of tetrodotoxin levels in the powder detected amounts too low to have any relevant effects, though Davis and another set of researchers have countered that fluctuations in pH dramatically affect those levels.

Tetrodotoxin levels aside, “the main criticism of Wade’s hypothesis is that tetrodotoxin does not confer the long term fugue that would be necessary to keep someone in a wakeful but zombified state,” says Frank Swain, a science writer currently working on a book about zombies. Swain also points to clinical examinations of three purported zombies, where each was diagnosed with a mental illness. “It seems zombies are just normal people with learning difficulties, who become pawns in various feuds as one family accuses another zombifying their children,” Swain says.

Davis, today an explorer-in-residence at the National Geographic Society, defends his work, saying that examining zombies with a purely chemical lens ignores their cultural context. “The zombie definition in Haiti has nothing to do with the poison,” he says. “Of course tetrodotoxin cannot make a zombie, but it can make someone appear to be dead.” From there, the belief system takes over and makes tetrodotoxin “the obvious culprit,” he adds.

Whether or not you adhere to the Haitian belief system, tetrodotoxin is a chemical that’s not to be messed with. Yet somehow fugu emerged as a delicacy. Customers line up, as the BBC puts it, to “play Russian roulette at the dinner table”. Consuming fugu is a much bigger gamble than consuming a burger made with the infamous meat product “pink slime”. But it was the slime that got the outrage.

It all comes down to information and choice. According to economist Robin Hanson, America is much more paternalistic when it comes to regulating foods consumed by the poor and by children, presumably because people feel those groups are unable to obtain or act on the information they’d need to make informed food choices.

Preserved pufferfish at the Heard Natural Science Center, Fairview, Texas (Flickr/gurdonark)

With fugu, folks know what they’re in for. They’re aware of the risk, though they may be less aware of the black-market trade in pufferfish, or of Tokyo’s recent move to ease strict regulations about who can serve it. And it doesn’t end with food. Hairstylists and consumers didn’t know that the cancer-causing chemical formaldehyde was in the hair-straightener Brazilian Blowout, because of the company’s deceptive marketing. Now that they do, some people beg for it anyway, and drop hundreds of dollars a pop to do it.

Our relationship with toxic chemicals is complicated. It isn’t always Nick Kristof’s “Big Chem” that’s out to obscure dangers or cloud our judgement. Sometimes, it’s human nature. We know smoking’s bad for us, and we do it anyway. But we don’t always know what lurks in, for example, a trailer provided by FEMA. Painting chemicals as “evil” or “good” is too simplistic- it’s all about their doses and their context. Instead of op-eds “teaching nothing more than a generalized chemical anxiety”, as Deborah Blum eloquently wrote, the world would be better served by op-eds that call for better information on what chemicals’ danger thresholds are. It’s a nuanced mission, but I’d venture a paper of the New York Times’ caliber is up to it.

TEDMED: Andrew Read’s Five Tips For Keeping Superbugs At Bay

Read (TEDMED)

Researchers may like to think they’re pretty smart, but you could argue that bacteria have also got some bragging rights. Every day, microbes develop resistance to even the most powerful antibiotics scientists have developed.

Andrew Read thinks evolution is the best lens for staring down the superbugs. He took the stage Thursday at TEDMED, where he warned, “we’re picking a fight with natural selection.”

“Picking a fight without Darwin is like going to the moon without Newton,” Read added. “We are in the dark ages when it comes to evolutionary management.”

Read, director of Penn State University’s Center for Infectious Disease Dynamics, sat down with me on Thursday and shared a few principles he thinks the scientific community should keep in mind in order to keep antibiotic resistance in check. Here are his five tips for would-be superbug slayers. Continue reading →

TEDMED and Alzheimer’s: Gregory Petsko, Reisa Sperling, and the next Al Gore

Petsko (TEDMED)

Gregory Petsko knows why he came to TEDMED. “I’m looking for Al Gore,” he told me flat-out over lunch. Folks who know Petskoknow the former Brandeis University biochemistry department chair isn’t one to mince words. And he’s nailed the reason why an academic might want to look outside traditional conferences and soak up some of the TEDMED aura. He’s looking for a charismatic champion to take up a biomedical cause: in Petsko’s case, it’s support for research in Alzheimer’s disease.

Petsko and Reisa Sperling, director of the Center for Alzheimer’s Research and Treatment at Brigham and Women’s Hospital, talked about Alzheimer’s at TEDMED on Wednesday. Both talks were cast as calls to action. Just consider the introduction Petsko got from TEDMED chair and Priceline.com founder Jay S. Walker: “This is a man who hears a bomb ticking.”

Alzheimer’s statistics are sobering and Petsko used them to dramatic effect. People who will reach 80 by the year 2050 have a 1 in 3 chance of developing the disease if nothing is done, he told the audience. “And yet I hear no clamor,” he said. “I hear no sense of urgency.”

Petsko shared some not-yet-published work with TEDMED’s audience. Continue reading →

Francis Collins At TEDMED – Repurposing Drugs, Replacing Animal Models, Rocking Out


You know you’re at an interesting conference when the director of the NIH starts off his presentation with a guitar duet, and shares a session with Cookie Monster.

But the organizers of TEDMED made a very deliberate decision in opening this year’s conference with Francis Collins. This is the first year that the gathering of medical luminaries, artists, and design gurus (TED stands for Technology, Entertainment, Design) is taking place in Washington, DC, after moving from San Diego. It marks a philosophical shift for the organization, from TEDMED as idea incubator to TEDMED as inserting itself into the national conversation on health and medicine. What better way to do that then bringing in the head of the biggest biomedical funding agency?

Collins wants to compress the time it takes to get a drug development pipeline, and make the pipeline less leaky. This isn’t news to folks around the pharma blogosphere, including here at the Haystack, Ash at Curious Wavefunction and Derek Lowe, who’ve followed last year’s announcement of NIH’s venture for drug discovery, the National Center for Advancing Translational Sciences.

Folks have expressed some concerns about the concept, and its emphasis on the promise of gene-based drug discovery. But, as Derek noted, the fact of the matter is that everyone in drug discovery wants the things Collins wants, so there’s a measure of goodwill for the venture too.

Collins spent his time on the TEDMED stage emphasizing two things: drug repurposing and developing high-tech cellular solutions to supplement and replace often-imperfect animal models.

On the tech side, Collins showcased the Harvard-based Wyss Institute’s lung-on-a-chip, which combines tissue engineering and electronics to mimic the interface between the lung’s air sacs and capillaries (Science, DOI: 10.1126/science.1188302). He said that technologies like this suggest viable alternatives to animal testing are possible.

When New Scientist reported on the lung-on-a-chip in 2010, researchers praised it as a step in the right direction, but cautioned that immortalized cell lines, such as those on the chip, don’t neccesarily behave like primary cells from patients. Collins also noted that it might be possible to use such devices with patients’ own cells someday.

On the repurposing side, Collins cited an article on the topic in Nature Reviews Drug Discovery (DOI: 10.1038/nrd3473), and alluded to lonafarnib (SCH 66336), a farnesyltransferase inhibitor that was originally designed to be part of cancer-treatment cocktails. It didn’t pan out as a cancer drug, Collins said, but now clinical trials are underway to test whether the drug is effective at countering a rare mutation that causes Hutchinson-Guilford progeria, an ailment that leads to rapid aging in children. Collins shared the stage with 15-year-old Sam, a progeria patient.

Francis Collins (right) and Sam. (TEDMED)

To bridge the massive gap between ideas and applications in medicine “we need resources, we need new kinds of partnerships, and we need talent,” he told the audience.

In a conversation with reporters after his talk, Collins provided another repurposing story published last month– bexarotene, a retinoid X receptor agonist intended for lymphoma that was just shown to clear amyloid-beta and reverse cognitive deficits in a mouse model of Alzheimer’s (Science, DOI: 10.1126/science.1217697)

At that chat, I asked Collins how the repurposing effort and his call for talent squares with massive layoffs in industry and flat or declining funding.
“It would help if we had a strong foundation of support,” Collins said. He said his agency’s purchasing power has decreased 20% over the last 8 years.

Another reporter asked what was the main obstacle to getting repurposing become habit. “IP,” Collins said. He told reporters that a model intellectual property sharing agreement with pharmaceutical companies has been drafted. Asked if companies had signed on to it, Collins said “we’re working on it.”

UPDATED 3:30PM 4/12: Here’s the scoop on Cookie Monster, for Muppet devotee Robin:
he spoke later in the session with ultramarathoner Scott Jurek about nutrition.

How Jagabandhu Das made dasatinib possible

In my story on how drugs get their generic names for this week’s issue of C&EN, I briefly discussed how the chronic myelogenous leukemia medication Sprycel (dasatinib), mentioned in this Haystack post by SeeArrOh, ended up being named after Bristol-Myers Squibb research fellow Jagabandhu Das. Even though Das, or Jag, as his coworkers call him, didn’t discover the molecule that bears his name, the program leader for Das’s team, Joel Barrish, says dasatinib wouldn’t have existed without him.

So how’d Das make a difference? About one and a half years into the search for a kinase inhibitor that might be able to treat chronic myelogenous leukemia, “we were hitting a wall,” Barrish, today vice-president of medicinal chemistry at BMS, recalls. “We couldn’t get past a certain level of potency.”

Early on, the team’s work suggested that a 4′-methyl thiazole was critical for potency. Replace the methyl with a hydrogen, and potency went out the window. But Das challenged that dogma, Barrish says. He thought the compound series had evolved to the point where it would be a good idea to go back and test those early assumptions. His hunch paid off– in the new, later kinase inhibitor series, it turned out that removing the methyl group from the thiazole actually boosted potency. Thanks in large part to that discovery, the team eventually was able to make kinase inhibitors with ten thousand fold higher activity.

Dasatinib (J. Med.Chem.)

“Jag didn’t stop there,” Barrish says. After debunking the methyl dogma, Das found a way to replace an undesirable urea moiety in the team’s inhibitors with a pyrimidine group, which improved the inhibitors’ physical properties. With help from Das’s two insights combined, eventually BMS’s team came up with the molecule that became dasatinib (J. Med. Chem., DOI: 10.1021/jm060727j).

Generic naming requirements are extensive, but the committees involved in the naming process are willing to use inventors’ names as long as they fit the criteria.
But sometimes, Barrish says, “there’s luck involved in who makes the final compound.” In the dasatinib story, though, it was clear that Das’s discoveries were the keys to success.

When dasatinib was in clinical trials and it came time to put forward a set of possible generic names for consideration, Barrish didn’t have to think too hard about who was most responsible for his team’s success. “It was very clear in my mind that it was Jag,” he says. So he added dasatinib to the list.

“I admit, it was one of those things you do and you kind of forget about it, thinking, ‘oh, they’ll pick something else’,” Barrish says. When dasatinib ended up being the name of choice, he says, it made the entire team feel good. “And obviously, Jag was quite pleased with it.”

Takeda’s Diabetes Drug Candidate TAK-875 In Phase III Trials

Takeda Pharmaceutical today announced it has begun Phase III clinical trials of TAK-875, a first-in-class drug candidate for treating type 2 diabetes. The experimental therapy activates GPR40, a G-protein-coupled receptor that resides in pacreatic islet cells.

The TAK-875 story is as much about the biology of the target as it is about the molecule itself. And it’s a story that owes much to the company’s willingness to delve into uncharted territory.

In the early 2000s, scientists knew GPR40 existed, but didn’t know what GPR40′s purpose was in the body. Plenty of proteins fit this description– they’re called “orphan receptors” in the industry parlance. Much of Takeda’s drug discovery strategy is based on figuring out what orphan receptors do.

In a 2003 paper in Nature (DOI: 10.1038/nature01478), Takeda laid out what it learned about GPR40. The receptor responds to a variety of long-chain fatty acids. In response to fatty acid binding, GPR40 activates and boosts insulin secretion from pancreatic beta cells.

GPR40 became a viable drug target for Takeda for several reasons. First, one of the hallmarks of type 2 diabetes is a reduction in insulin secretion from pancreatic beta cells, something GPR40 activation could help counter. Second, G-protein-coupled receptors are established drug targets– and GPR40 happens to be in the class of GPCRs for which researchers know the most about structure– the Class A, or rhodopsin-like, GPCRs. (Note: other GPR-type receptors are diabetes targets as well– C&EN contributing editor Aaron Rowe has written about Arena Pharmaceuticals’ activators of GPR119 as diabetes drug candidates.)

TAK-875 docked to a model of GPR40 (ACS Med. Chem. Lett.)

Takeda used structural knowledge to its advantage in the discovery of TAK-875 (ACS Med. Chem. Lett., DOI: 10.1021/ml1000855). Researchers were able to build a model of GPR40 based on its similarity to GPCRs of known structure, and dock potential drug candidates inside to see how well they could bind.

This is far from the only drug discovery story that has to do with “de-orphanizing” orphan receptors. In fact, as far back as 1997, pharmaceutical company researchers were writing about orphan receptors as a neglected drug discovery opportunity (Trends Pharmacol. Sci., DOI: 10.1016/S0165-6147(97)90676-3). And of course, just because researchers have “de-orphanized” a receptor doesn’t mean all of the complex biology is pinned down. Case in point: the PPAR receptors (J. Med. Chem., DOI: 10.1021/jm990554g). Despite these receptors’ promise as targets for obesity and diabetes, drugs designed to target them have tanked in development or had unexpected problems after arrival on the market (read: Avandia).

So as TAK-875 enters Phase III trials, the news might be about the drug candidate’s clinical performance, but you can be sure that Takeda’s researchers are still working hard to unravel as much of GPR40′s basic biology as they can behind the scenes.

More Medicinal Chemistry At The #Chemcarnival

Last month, I wrote a post on amide formation, that humble but useful tool in the medicinal chemistry arsenal, for CENtral Science’s “Your Favorite Reaction” blog carnival. Today, CENtral Science’s own pharmacologist-in-residence David Kroll has compiled a must-read guide to all the entries in the carnival, and I was pleased to see a few more entries that might pique medicinal chemists’ interest. I was especially psyched to see entries from bloggers with whose writing I wasn’t familiar.

Make sure to read David’s fantastic overview to learn about each post in the carnival. But I’ve made note of a few favorites here at The Haystack: Continue reading →