Tag: Pharmaceuticals

  • Thalidomide Tragedy: Horror Drug or Miracle?

    Thalidomide Tragedy: Horror Drug or Miracle?

    The thalidomide tragedy was the biggest “man-made disaster apart from war”.

    This molecule’s structure looks simple and innocent, but a chiral carbon gives rise to two enantiomers with different pharmacological effects. While one isomer was a safe sedative, the other one led to limb malformations in thousands of babies. We will check out how this works exactly, but notably, the enantiomers interconvert in the body so there’s no way to control them.

    Get this: Despite increasing doubts of its safety, the US distributor of this horror drug aggressively pushed for its approval simply to maximize sales over Christmas!

    If you think the heart-breaking tragedy sealed thalidomide’s fate, you couldn’t be more wrong. Half a century after the tragedy, it generated up to $500 million sales for a pharma company! But wait, there’s more. A slightly modified, much more expensive version of thalidomide brought in eye-watering 12 billion dollars.

    How is it possible that the same drug which inflicted so much damage revived and even influenced one of the biggest acquisitions in pharma history? As we will see, the answer is glue – no joke. The story of course wouldn’t be complete without classic big pharma monopoly games and price hiking. And let’s not forget everyone’s favourites – lawsuits.

    In this post, we will go through history, biology, organic chemistry and pharmacology of thalidomide and its many cousins. You will also appreciate some paradoxical and morally questionable aspects of drug development.

    What is Thalidomide?

    Let’s get into it. Thalidomide has a very simple chemical structure. In the 1950s, the relatively small and inexperienced pharmaceutical company Chemie Grünenthal looked for new antibiotics. Instead of antibiotic activity, thalidomide seemed to be a great sedative and help with sleep or nausea. Unfortunately, it doesn’t help the story that some of Grünenthal’s leaders were ex-Nazi scientist. The research head Mückter was involved in death camp experiments and made bank during his tenure. It started all rosy. Initial safety tests in mice and rats showed good tolerability and no side effects even at remarkably high doses. Back then, you didn’t have to understand how drugs worked at all. So, thalidomide was dubbed completely safe and aggressively marketed in 1957.

    It quickly became Germany’s second best-selling pharmaceutical, just behind Bayer’s Aspirin.Ironically,safety was one of its key marketing messages. Many pregnant women used thalidomide for morning sickness. The lack of toxicity was convenient as unlike barbiturates, this agent couldn’t be misused for suicide attempts. However, over the next two years, sudden increases in cases of usually rare limb defects were detected in newborns.

    It’s less known that there were pretty early findings of teratogenicity and neurotoxicity from various researchers. Some of them, like these observations on tad poles, were shared with Grünenthal already in 1959 – with no response.

    Thalidomide Side Effects: Beginnings

    Because the incidence of deformations increased so unprecedently, German paediatricians suspected an environmental factor. In late 1961, thalidomide use by mothers during early pregnancy was the common factor. Only later did we find out that deformations were actually just the tip of the iceberg. Thalidomide induced many more miscarriages and less obvious defects like organ problems. After increasing noise on the issue, the German government pulled the drug off the market against the company’s wishes. The adverse impact of early use is so high that even a single tablet was enough to induce pregnancy loss or abnormalities – but why? To understand, we need to recap two topics.

    First, we need to know about the ubiquitin proteasome system, basically, cellular garbage management. Some of you might remember the process from your biochemistry classes.

    The process starts with very few, so-called E1 enzymes which are activated with ubiquitin, a small regulatory protein consisting of roughly 80 amino acids. This green ubiquitin tag is ultimately what directs the degradation of target proteins. As you can imagine, there are thousands of proteins that the cell might want to be able to degrade. However, it would be challenging to do this specifically if all you have are a few different E1 enzymes. This is ubiquitin groups are cascaded to a broader variety of E2 conjugation enzymes which finally put the tag on more than a thousand so called E3 ligases. These enzymes recognize specific substrates and upon addition of enough ubiquitin tags, the proteasome shreds up their targets into smaller peptides.

    Second, we need to know about molecular glues. These work exactly like you would think. The glue molecules bind between two different proteins, aggregating or gluing them together. This can lead to several effects, but targeted protein degradation is the most important one.

    How does this relate to thalidomide? Well, the molecule binds to the protein cereblon which is part of a E3 ubiquitin ligase complex. Once bound, it can act as a glue between cereblon and neo-substrates, innocent molecules. This exposes them to the E3 ligase machinery, so they are ubiquitinylated and degraded.

    Remember that the adhesion arises from nuanced interactions between functional groups of the molecular glue, cereblon in purple, and its neo-substrate in green. We don’t know the natural targets of cereblon but amongst others, it’s critical for brain development, hence its name.

    Thalidomide Side Effects: Cereblon

    By acting via cereblon, Thalidomide-initiated protein degradation influences the body’s immune system (immunomodulatory drug). The mechanism is very complex, but one of the innocent casualties is SALL4. This is an important transcription factor that governs gene expression for normal limb development. Its absence results in deformations which is why thalidomide proved so dangerous for pregnant women. Actually, genetic deletion of SALL4 replicates a similar phenotype. But why was this missed by Grünenthal? A critical piece of information that was not known in the 1950s – rodents are resistant to thalidomide’s teratogenicity. This explains the absence of safety signals, even at high doses. Only later did people figure out that rabbits or chickens are more sensitive animal models. Why?

    The susceptibility comes from a single amino acid difference in cereblon sequences. Primates and rabbits with a valine suffer thalidomide embryopathies – while rodents with an isoleucine did not show any safety signals. Interestingly, the bushbaby bears an isoleucine and is the only known resistant primate. Scientists demonstrated that mutant mice with an unnatural valine at the position become sensitive. Compared to wildtype mice, they showed statistically significant higher miscarriage rates. This is really fascinating – a slightly bulkier amino acid influences binding and degradation of substrates such as CK1 alpha but potentially also SALL4 or others.

    If you had a chemistry class or two, you would know that by having one chiral center, thalidomide has two enantiomers. Much too late, it turned out that the (S) enantiomer is ten-fold more potent protein degrader. Giving only the safe isomer as a drug is not an option. The acidic proton at the chiral center triggers partial conversion to the bad enantiomer at pH levels of over 6. If you’ve watched my deuterium video, you will know that this interconversion is slower for deuterium due to its kinetic isotope effect.

    How can the almost identical (R)-enantiomer be safe? Although it has the same molecular contacts with cereblon, its affinity is much lower due to an energetically unfavourable conformation that it needs to adopt upon binding. This twisting occurs because the glutarimide ring wants to minimize steric clashing with the binding pocket, particularly the highlighted tryptophan 383.

    Thalidomide Synthesis & AFtermath

    If we look at its synthesis, it becomes obvious why original thalidomide is a racemic mixture. The original Grünenthal synthesis starts with a condensation of L-glutamic acid and phthalic anhydride. Even though the amino acid used was chiral, the basic conditions and high temperature result in a racemic product due to the. To close the ring, the free acids linked via activation with acetic anhydride and a last treatment with urea introduced the nitrogen.

    So, the aftermath entailed a large criminal trial, examining potential negligent behaviour by leading Grünenthal employees. The process was extremely drawn out, probably the dream of every lawyer. 600 thousand pages of documents without any clear verdict. Ultimately, it was said that based on the state of science at the time, the teratogenic effects of thalidomide could not have been anticipated – so the trial was terminated and settled between Grünenthal and impacted parents. The company is still providing support to affected persons through a novel foundation, with more than $100 million Euros contributed to date.

    Thalidomide in the United States

    The impact in the US is another ridiculous story. Grünenthal had offered the company Smith, Kline & French – today’s GSK – to market the drug in North America. SKF ran a large clinical trial which likely also resulted in several phocomelia cases, and they declined Grünenthal’s partnership offer.

    However, another company Richardson-Merrell was eager to introduce it. These guys were calling up the FDA to submit a marketing authorization application in the fall of 1960. I invite you to read this nice article which contains comments of Frances Kelsey who reviewed the application at the FDA. And yes, that’s her with President John F. Kennedy, getting a medal for Distinguished Federal Civilian Service. You see, as if this story couldn’t get worse and more capitalistic, Richardson-Merrell was pushing for an early approval prior to Christmas to maximize their sales.

    In a – now recognized as heroic – move Kelsey challenged the drug’s data. Something felt off about giving enormous amounts without any toxicity – so suspicions rose that other conditions could change the drug’s absorption and unveil toxic effects. Her suspicions proved to be right – but that didn’t prevent Richardson-Merrell from giving away literally millions of thalidomide tablets for “investigational use”, at the time permissible under existing regulations. The FDA cited 17 children born in America with thalidomide-associated deformities, but the true number is surely higher.

    What has science learned from this tragedy? On one hand, drug controls got stricter. Prior to 1962, drug developers only had to show that new drugs were safe – and as we just saw, even that was not a given. A new pivotal amendment required strict “proof of efficacy” from well-controlled studies, and not the bro-science which Richardson-Merrell tried to pass. Drug advertising now required accurate information about side effects, and clinical trials had to include informed consent of participants prior to the study. For us in the 21st century, this seems obvious. The FDA also launched a comprehensive assessment of drugs that were already on the market. Finally, drug testing got more robust with a requirement to use rabbits and other thalidomide-sensitive species for teratogenicity testing.

    Is Thalidomide Still Used Today?

    Thalidomide’s risks but also benefits continue to linger. Just shortly after its initial withdrawal, it proved efficacious in ENL, a leprosy complication. To avoid teratogenicity, access to the drug depends on so-called Risk Evaluation and Mitigation Strategies, short REMS. For instance, female patients must avoid pregnancy though regular testing and use of two or more forms of reliable contraception. In the US, thalidomide was approved for leprosy in 1998 and REMS were well regulated. However, use over decades in countries like Brazil with subpar REMS has still led to some cases of embryopathy.

    Although there was research on thalidomide in cancer already in the 60s, the molecule was finally proven to have anti-cancer activity in the 90s. This time around, the company Celgene got IP rights to the drug and thoroughly interrogated its potential. A landmark trial showcased its value in multiple myeloma, a type of blood cancer. Given its unique mechanism and profile, combination with other agents was powerful. This resurrected thalidomide, turning a monster drug into a precious option for patients who relapsed or did not respond to other treatment.

    Mechanistically, the anti-oncology effect arises from degradation of Ikaros and Aiolos. Unlike SALL4, these transcription factors regulate the development of B and T cells of the immune system. Ultimately, thalidomide inhibits the process of angiogenesis. As a very smart person, you will realize that lower growth of new blood vessels in turn suppresses tumor growth.

    The “new early” days of thalidomide remained controversial, with a whistleblower lawsuit accusing Celgene of off-label marketing. Allegedly, they actively pushed thalidomide, which as we saw was approved for leprosy, to be off label prescribed to cancer patients prior to its approval. While these off-label prescriptions extended thousands of lives, intentional off-label marketing by companies is not compliant. The company ultimately had to settle the lawsuit for 280 million dollars.

    Lenalidomide: multiple myelomA Blockbuster

    Thalidomide’s legacy is even more shocking. We already know that small changes have big impacts so you shouldn’t be shocked. You see, two simple functional group modifications created lenalidomide. This is the big boy. By the way, there’s even another hybrid between the two – a bit less imaginative. Due to the new structures, these analogues enjoyed new marketing exclusivity, with great commercial success.

    Lenalidomide received an orphan drug designation – a FDA incentive that gives drug developers special tax incentives and market exclusivity. With a hefty original 6-figure price tag, the drug earned Celgene double digit billions in yearly sales.

    Lenalidomide didn’t sell for no reason. Molecularly, it is much more potent than thalidomide across various metrics. For instance, its IC50 inhibitory value against resistant multiple myeloma cells is orders of magnitude lower.

    These molecular changes also translate into better survival outcomes for patients than thalidomide. In addition, risks of neuropathies and other adverse events were lower. This is a follow-on strategy gone well: new molecule, better efficacy and financial success.

    Legal Considerations

    You could also argue that given Celgene’s research is not associated with Grünenthal’s initial wrongdoings, they actually changed the world for the better. You could also call it a perverse twist – a horror drug ended up as the basis for massive profit. Some have accused Celgene of using particularly fierce ways of preventing entry of generics. Doing so, it managed to command soaring prices for the drugs, and even increase them. This includes more than a dozen of patents on their REMS system which further blocked generic competition. Remember, REMS are special activities that patients, providers and distributors need to take to prevent harm from teratogenicity.

    In this case, it means that access to the drug is dependent on several criteria, such as regular pregnancy tests and surveys. This is great because it encourages safe use of the medicine, but as always, we have more potential illegal activities looming.

    For many years, Celgene fought it out with the generics manufacturer Mylan. You see, to call approve a generic medicine, the FDA needs to see bioequivalence data. Essentially, we need to undoubtedly prove that the copy has the same effects. So, generic manufacturers need to buy the branded drug. Allegedly, Celgene not only refused to sell the drugs directly, but they also implemented distribution restrictions that prevented Mylan from buying thalidomide and lenalidomide. This was resolved after five years in classic fashion by paying 100 million dollars and some change to settle the claims.

    As alluded to, subsequently BMS acquired Celgene and with it, the knowledge on thalidomide and friends. If you thought this was the end of the saga, think again.

    Outlook: More Cereblon Modulators

    The development of next-generation cereblon modulators such as iberdomide is still ongoing. At a first glance, this one might look like a simple copycat molecule.

    As you can see from the crystal structure, the morpholino side chain extends into a pocket on cereblon, increasing surface interactions and binding of the molecular glue.

    This enhanced affinity results in a faster protein degradation of neo-substrates, and anti-proliferative activity against multiple myeloma cell lines. In normal cells, iberdomide is much more potent – compare the red and green curves. More importantly, this analog retains activity in cells resistant to lenalidomide. Due to this higher penetration, the hope is that the drug will prove more efficacious in resistant cases. It’s currently in phase 3 trials and again, the idea is combining it with other medications to stack up the effects.

    We will close with a final next-generation idea: covalent modification of cereblon. Scientists have noted that there’s a histidine residue close to the molecular glue binding site. Do you already know where this is heading? By creating analogs with electrophilic groups such as this highly reactive fluorosulfate, we can trigger a covalent bond formation with the proximal histidine.

    Why is this even interesting? Well, this covalent modification triggers broader conformational changes which change cereblon’s activity. The scientists found that this covalent modulator led to the degradation of the so far elusive protein NTAQ1. Thus, such experiments might unlock even more avenues for drug discovery in different tumor types.

    To not overdo it, we’ll wrap up here. As always, until next time!

    Key references on thalidomide science and other information:

    • Frances Oldham Kelsey. FDA medical reviewer leaves her mark on history | FDA Consum 2001, 35, 24
    • The Thalidomide Syndrome | Scientific American 1962, 207, 29
    • THALIDOMIDE AND CONGENITAL ABNORMALITIES | Lancet 1962, 279, 45
    • The Ubiquitin Proteasome System in Neuromuscular Disorders: Moving Beyond Movement | Int J Mol Sci 2020, 21, 6429
    • Molecular glues modulate protein functions by inducing protein aggregation: A promising therapeutic strategy of small molecules for disease treatment| Acta Pharmaceutica Sinica B 2022, 12, 3548
    • Exploiting ubiquitin ligase cereblon as a target for small-molecule compounds in medicine and chemical biology | Cell Chem Biol 2021, 28, 987
    • Crbn I391V is sufficient to confer in vivo sensitivity to thalidomide and its derivatives in mice | Blood 2018, 132, 1535
    • Differentiation of antiinflammatory and antitumorigenic properties of stabilized enantiomers of thalidomide analogs | PNAS 2015, E1471
    • Lawsuit Blames Thalidomide for More Birth Defects | Scientific American 2011
    • Antitumor Activity of Thalidomide in Refractory Multiple Myeloma | NEJM 1999, 341, 1565
    • Immunomodulatory Drugs for the Treatment of B Cell Malignancies | Int. J. Mol. Sci. 2021, 22(16), 8572
    • A Cereblon Modulator (CC-220) with Improved Degradation of Ikaros and Aiolos | J Med Chem 2018, 61, 535
  • This Obesity Drug Tricks Your Body Into Burning Fat (Exercise Mimetics)

    This Obesity Drug Tricks Your Body Into Burning Fat (Exercise Mimetics)

    Exercise mimetics: Watch this video or read the written blog below!

    Are you tired of dieting or pounding the pavement like David Goggins just to shed a few pounds? Imagine a future medicine that could mimic the benefits of literally running for days.

    Weight loss meds like Ozempic have been sending shockwaves through Hollywood and Wall Street. Advocacy by famous figures went viral on social media, causing supply shortages and more recently, questions on their safety emerged. The stonks of select pharma companies exploded, with Danish Novo Nordisk’s market capitalization surpassing the country’s GDP.

    Is this first wave of drugs already the be-all, end-all? Side effects like loss of hard-earned gains and pooping pants lead to many users stopping treatment.

    Meet SLU-PP-332, a simple small molecule melting fat and effectively mimicking marathon training in mice – all without setting a tiny paw on a treadmill, and without eating less. We will cover this molecule’s discovery, chemical synthesis, and pre-clinical efficacy. This will enrich your interdisciplinary knowledge and give you some practise for data interpretation. We will also explain how other exercise mimetics work and cover random facts, such as taking a closer look at alleged health benefits of red wine.

    How obesity Drugs Work

    So regardless how we feel about it, obesity is the problem for healthcare systems, and source of many problems. By 2030, nearly half of Americans will be obese – not to mention overweight.

    Why even consider drugs for weight loss? We all know that exercise and diet regimens have very low compliance in reality. People just don’t stick to them even if they know they should. Also, some patients have co-morbidities that make them exercise-intolerant. It doesn’t matter how much you want to be David Goggins – if you have chronic heart failure, you can’t run for days.

    Another issue: the emerging obesity drugs melt away body mass, but much of it is also muscle tissue. Drugs which can trigger fat loss, retain muscle and simulate exercise would be helpful for many people.

    Obviously, with hundreds of millions of obese people, this is a massive long-term opportunity for pharmaceutical companies. This bullish outlook has resulted in strong investor interest in obesity drug developers, adding billions of dollars to their valuations.

    The drugs behind this gold rush are GLP1 agonists. As mimetics of the incretin hormone GLP1, they stimulate insulin production and help manage blood sugar – this is especially key for diabetics. They also slow down movement of food in your stomach which can help patients feel fuller faster and curb hunger. Leave a comment if you want to learn more about these hyped obesity drugs in a future video – they have a massive history of research behind them. Today, we will instead check out the so-called exercise mimetics.

    Science Behind Exercise Mimetics

    PGC-1a is a key link between endurance exercise and physiological adaptation. Expressed in various tissues, this is the master regulator of creation of mitochondria – also known as the powerhouse of the cell – as well as other processes like glucose and lipid metabolism. Because it’s a coactivator, it interacts with other transcription factors to modulate the expression of certain genes. Looking at the example of detoxification of reactive oxygen species, we realize this gets into complex cellular biology territory. Due to this complexity, dysregulation of PGC-1 alpha disrupts physiological processes and contributes to many diseases.

    Why is this relevant for exercise mimetics? Well, while various mimetics have different primary targets, most ultimately all trace back to PGC-1 alpha.

    One rather famous molecule in this class is resveratrol. This polyphenol is present in many foods and wines, and it can trigger just about every effect under the sun. It likely indirectly activates the so-called SIRT1 protein, which in turn deacetylates PGC-1 alpha and ramps up beneficial activities. There’s a lot of literature on this if you want to check out the cellular biology.

    Some of the first insights came from a 2006 study looking at daily intake of resveratrol in mice being fed a high-fat diet. If you are good at playing ‘spot the difference’, you will notice that fat and muscle tissues feature much denser mitochondria. It looks like these mice adapted to exercise they didn’t perform – thus, we’re calling such effects mimicry.

    Shockingly, some human studies showed resveratrol actually blunted some aspects of training adaptation. Ironically, removal of reactive oxygen species by resveratrol might limit training-induced adaptations. This once more highlights that in biology, nothing is simple or black-or-white.

    Based on the immature human data, the verdict on resveratrol is still open. If you check Wikipedia, you can see that no health benefits have clear evidence. Such lacking clinical data is a common theme for exercise mimetics in general, as they represent a new class of compounds.

    Even big pharma companies dabbled in this space, with GSK paying 700 million dollars for a biotech working on a resveratrol formulation 15 years ago. They did not test it in obesity but rather haematological cancers. This proved to be bad luck as they killed the program after seeing increased risks of kidney failure. You can see that even introducing seemingly healthy substances like resveratrol into medical practice can be challenging.

    Estrogen-related REceptors

    So let’s get into exercise mimetics more deeply. To understand SLU-PP-332, we need to take a look at another investigational compound. Unlike resveratrol which targeted SIRT1, this one activates the estrogen-related receptor gamma.

    This is one of three siblings of the ERR family, expressed in tissues with high energy demands. These nuclear receptors have received considerable attention for their potential value in treating metabolic diseases. As a side note, nuclear receptors are proteins chilling in the cytosol or nucleus. They can sense specific ligand molecules and in turn, regulate expression of specific genes.

    As their name suggests, ERRs are structurally related to estrogen receptors (ERs). These nuclear receptors utilize estrogens as ligands and contribute to breast and other cancer types. A key ER-drug is Nolvadex – more famously used by bodybuilders to manage their gynecomastia. Back to ERRs, which despite their resemblance work via different mechanisms than ERs.

    The company GSK developed the first small molecule ERR agonists already in the early 2000s. Remember for later that this hydrazone-based agent strongly activates beta and gamma, but not the alpha ERR isoform. ERR beta is a negligible player given it’s not present in skeletal muscle .

    ERR gamma highly expressed in oxidative slow-twitch muscle tissues in the calves, with minimal expression in quadriceps which appear more white. Its powerful effects can be clearly seen if a spooky experiment is performed, creating transgenic mice that express ERR gamma more broadly. These super mice have deep red muscle bellies due to improved oxidative capacity, increased vascularization and bigger mitochondria. In an endurance exhaustion test, transgenic mice ran roughly 1500 meters instead of measly 600m by wildtype mice. This means without any specific training, ERR overexpression creates endurance monsters that can run more than twice as far.

    We also need to look at ERR alpha, the receptor which was not significantly activated by the GSK compound. Like the related gamma isoform, it’s expressed in skeletal muscle and has similar functions.

    We’ve just seen how transgenic mice expressing ERR gamma are endurance monsters. For ERR alpha, scientists also looked at the opposite model – so called knockout mice lacking this important nuclear receptor. These mice are able to live somewhat normally which means that this receptor type is not vital for life. However, if you look at the relative size of the heart and muscles compared to body weight, the knockout mice in blue have significantly lower muscle mass.

    As you might expect, this means the mice have lower endurance capacity and reach exhaustion much faster. The realization here is that if lacking ERR alpha results in endurance weakness, we could be able to mimic endurance exercise by activating it with a drug.

    SLU-PP-332

    The first question is, how do we find an ERR alpha drug? One way is to start with the GSK compound – but wait, didn’t we say this one only activated the beta and gamma ERRs? I’ll explain. First, you have to know that the only available X-ray structure for this molecules is with ERR gamma. This tells us with high certainty what the binding mode looks like – for example, in red we can see that the phenolic hydrogen is involved in a hydrogen bond with an aspartate residue of ERR gamma. This structure can guide the simulation of how the slightly different binding pocket of ERR alpha would bind to ‘4716. As we’ve said the binding is not that strong, but we can use it as a starting point for the design of more potent drugs.

    The scientists behind this research identified a crucial phenylalanine at position 328, here in pink, which is present in ERR alpha but not gamma. By engineering interactions with this unique group, we could design a drug that selectively targets alpha over gamma.

    This was achieved very easily by converting the iso-propyl benzene of ‘4716 into a naphthalene ring. As you can see from the new simulation, this extended aromatic system can undergo pi-pi stacking with then phenylalanine. This simple change increases affinity for ERR alpha by more than 50-fold. Let’s compare it again to ERR gamma. As the phenylalanine is not present, the interactions are weaker here and the agent is around 4-to-1 selective for the alpha receptor.

    The chemistry behind this is so easy that it can be managed by even the clumsiest undergrad . The starting materials are simple and cheap – the only thing needed is cooking them up in toluene overnight. The highly nucleophilic hydrazide adds to the electrophilic aldehyde, creating an adduct. After a proton shift, the intermediate can eliminate water, forming the hydrazone linkage of the product. As it precipitates from the solution, it can be easily separated and subsequently recrystallized to give pure SLU-PP-332.

    Exercise mimetic effects

    By now you are eager to hear about its effects – is it really as impressive as the clickbaity title? Let’s start from micro and go to macro. For some of these, feel free to pause and take more time to digest the info.

    Upon treatment of isolated myocytes or muscle cells, the researchers observed a doubling of the maximal mitochondrial respiration rate. Obviously, more oxygen means a higher energy production. Not only are the mitochondria more productive, but there are more of them!

    There were also structural differences. Here you can see stained sections from quadriceps muscle. Notice the difference? There’s significantly more green color which corresponds to myosin protein in type IIa fibers which are fast, aerobic muscles. On the other hand, there are less red, type IIb fibers. These are muscles which act fast but use anaerobic metabolism, meaning they fatigue quickly. Interestingly, no difference was observed for slow aerobic type I muscle.

    Knowing this, what do you expect regarding exercise performance? Well, mice treated for a few days with this compound showed superior endurance without any training, being able to run roughly 70% further than normal mice. Unfortunately, the experimental procedure for this assessment is less fun. You can tell because the wording says “mice were run”. If they subsequently didn’t react to electrical shocks, you know that they were legitimately exhausted.

    There are additional investigations into the “why” behind this such as specific gene expression targets. I leave this topic for interested nerds to check out on their own.

    One interesting finding was that extended dosing for 2 weeks led to difference in grip strength as well. Unfortunately, the authors don’t describe this in more detail. It looks like grip strength decreased over time for both the active and the control group. This might be because of accumulating fatigue or other things. It would be cool if the authors are correct – meaning if SLU-PP-332 could enhance some strength endurance, and not just pure aerobic performance.

    We haven’t covered one major, obvious question yet. The molecule’s exercise mimetic effects are very intriguing, but does it have any impact on weight?

    Well, in another recent study the team documented that mice treated with the drug used more energy while consuming the same amount of food! Numerically it looks like they even had less food.

    Metabolically, ‘332 triggered a shift towards fat burning. Fatty acid oxidation increased by roughly 25%, while the use of carbs decreased reciprocally. Again, more details can be found in the paper.

    The magnitude of weight loss depends on the starting point. Normal mice with healthy diet and weight did not lose weight. On the other hand, obese mice eating an unhealthy high-fat diet saw 12% weight loss after one month. The researchers also looked at a genetic model. These mice don’t produce the key metabolic hormone leptin, leading to excessive hunger and food intake. Similar to the  diet-induced obese mice, these chunky fellas also dropped significant weight.

    We’ve noted that providing more than just weight loss is the next frontier. SLU-PP-332 might be one step in that direction. More pre-clinical work is required to understand its long-term effects. Maybe, related, optimized molecules could be even more potent. Researchers have not seen any safety signals but tolerability, administration and translation will be key to elucidate prior to first-in-human trials. These drugs will (likely) not be launched earlier than the end of the 2030s but with the excitement around obesity, it’s definitely going to remain an interesting space.

    References on exercise mimetics

    • PGC-1α, Inflammation, and Oxidative Stress: An Integrative View in Metabolism | Oxidative Medicine and Cellular Longevity, 2020, 1452696
    • Caloric restriction and exercise “mimetics’’: Ready for prime time? | Pharmacological Research 2016, 103, 158
    • Resveratrol improves mitochondrial function and protects against metabolic disease by activating SIRT1 and PGC-1alpha | Cell 2006, 127, 1109
    • Distribution and Effects of Estrogen Receptors in Prostate Cancer: Associated Molecular Mechanisms | Frontiers in Endocrinology 2022, 12, 811578
    • Identification and structure-activity relationship of phenolic acyl hydrazones as selective agonists for the estrogen-related orphan nuclear receptors ERRbeta and ERRgamma | J Med Chem 2005, 48, 3107
    • Exercise and PGC-1 alpha-Independent Synchronization of Type I Muscle Metabolism and Vasculature by ERR gamma | Cell Metabolism 2011, 13, 283
    • Estrogen-related receptor-α coordinates transcriptional programs essential for exercise tolerance and muscle fitness | Mol Endocrinol 2014, 28, 2060
    • Synthetic ERRα/β/γ Agonist Induces an ERRα-Dependent Acute Aerobic Exercise Response and Enhances Exercise Capacity | ACS Chem. Biol. 2023, 18, 756
    • A Synthetic ERR Agonist Alleviates Metabolic Syndrome | J. Pharmacol. Exp. Ther. 2023, 001733
  • Are New Drugs Really Better Than Existing Ones?

    Are New Drugs Really Better Than Existing Ones?

    Watch the video on YouTube or read the blog below!

    You probably know that drugs can get very expensive. What do you think – what percentage of new drugs actually provide significant therapeutic benefit compared to existing treatments? And do you think that drugs with a low clinical benefit are indeed priced any cheaper than highly beneficial ones?

    Beyond drug prices, we will also talk about cancer “approvals gone wrong”. These were shown only after their regulatory approval to lead to equal or even worse outcomes for patients. One of these debated drugs ultimately led to bankruptcy of the company who developed it. However, the molecule has some nice chemistry behind it. You know the channel – we will take any opportunity to study organic synthesis that we get.

    Healthcare Spending and Drug Prices

    Let’s face the facts – healthcare spending has grown much faster than gross domestic product – in the US and everywhere else. Drug costs are one driver behind this. The most extreme example is perhaps cancer, where we can observe almost exponential growth of drug costs over the last 50 years.

    The US spent $4.2 trillion on healthcare in 2021. Who paid the bill, and on what? As you can see, government spending on Medicare and Medicaid is about 40%, whereas patients paid out-of-pocket for 10% of costs. On the other hand, hospital care received the bulk of spend with 31%, with prescription drugs coming in at 9%. Increasing drug costs are problematic, but as we see, they are not the only reason behind high healthcare spend.

    Initially expensive branded drugs are becoming much cheaper after entry of generic drugs. Fortunately, this leads to more accessible, vital treatment options for patients. This is where we have the crux: While standards of care improved across all diseases, new medicines need to continuously drive improvement in therapeutic benefit.

    Let’s imagine we have a new drug in a disease that affects the liver, demonstrating it slows loss of liver function by 25%. Sounds good in theory, but let’s assume this was only tested against placebo and already approved treatments have shown similar results in their trials. If we ignore any benefits on things like safety or durability of response, this means the relative therapeutic benefit of this therapy would be rather low. On the other hand, a new drug showing superior efficacy to other already approved treatments would be much better. Instead of “me-too” drugs, we would want any new drugs to significantly improve on existing drugs. The problem is that this has not been the case in past years.

    The Therapeutic value of new drugs

    The authors of the first piece of research looked at the last decade’s new drug approvals and their ratings of therapeutic value from health technology assessment bodies in France and Germany. These agencies assess the added benefits of a drug’s approved indication compared with existing therapies. This tells us whether there is major, considerable, minor, or no benefit of a new drug. The underlying criteria are slightly different across countries but capture the drug’s effect on reduction of disease duration or side effects, for example. If any of the two agencies rated a drug as providing considerable or major benefit, the authors consider it a high value drug in their analysis.

    The sad result is that only 40 to 50% of drugs approved by the US FDA or European EMA regulator are high value drugs. But check out the second set of bars. These refer to approved uses in additional diseases or indications after a drug’s first approval. In these settings, are even less likely to be quote-unquote better drugs.

    Drugs with multiple indications

    But why can drugs have more than one indication? As most of you know, a single mechanism of action can apply to different diseases. For instance, immuno-oncology drugs like PD1 inhibitors can be applied across solid tumors. Keytruda, the soon-to-be world’s best-selling medicine, is approved in more than a dozen different tumor types. Beyond oncology, we have complement inhibitors like Soliris which you might remember if you watched the previous video on the world’s most expensive drugs. Because the complement immune pathway is involved in many diseases, it is possible that the same drug which saves kidneys might save eyes as well.

    On one hand, patients benefit because they get one more option which might help them go into disease remission (not always). It also makes sense for pharmaceutical companies to get rewarded by bringing innovation to more patients. Because clinical development costs billions, they maximize product revenues during their limited window of exclusivity.

    But the reality shatters this pleasant theory: Only 40% of drugs in supplementary indications bring significant new benefit. If we look at the relative rate, drugs are less and less likely to bring new therapeutic benefit in every follow-on indication.

    Some caveats remain, like questions behind the precise logic of defining something as high therapeutic benefit. There are specific local factors, like France using their own therapeutic strategy as a criterion. But more important is that while a drug might not be high value on average, sub-segments of patients with specific mutations or other characteristics might respond very well. We know who might respond best for some drugs but for most, this is less clear.

    Value of Accelerated approvals & Friends

    This research confirms what others have found before. An interesting second analysis differentiated the therapeutic value of normal drugs and those with expedited approval. The exception is awarded for drugs which major promise in diseases with high unmet (e.g., certain cancers, rare diseases). The logic is obvious: imagine there is a drug which shows drastic tumor shrinkage in an early phase 2 clinical trial. Instead of waiting 3-4 years for larger and longer-term data, an accelerated approval might be lifesaving for many patients. Accelerated approvals require drug developers to run confirmatory trials in parallel. The hope is that the drug will show full efficacy and safety retrospectively. In a minute, we will talk about two cases where this unfortunately was not the case.

    The publication at hand also included other expedited regulatory mechanisms in their analysis such as fast track and priority review, as well as breakthrough therapy designations.

    So, what do you think is value-add of these expedited programs? As you might expect and can see in the much higher purple band, drugs under expedited mechanisms are more likely to have high therapeutic value.

    Most program types are in a similar range, with breakthrough designations coming in highest – 60% are indeed high value. While normal approvals are at a crappy 13%, drugs with 3 or more designations are at 65%. These designations are awarded during development, so before the clinical product profile become clear. Thus, it’s obvious that we will never get to let’s say 90% for breakthroughs, simply because drugs which appear very promising in phases 1 or 2 might prove out to be only mediocre after a larger scale phase 3 trial. Still, regulatory agencies should give additional explanations or disclaimers to set more realistic expectations for patients and doctors.

    Are Drugs getting More expensive?

    Finally, let’s see what a 2020 study has to say, covering 65 cancer drugs across countries. The sad insight: low-benefit drugs are just as expensive as high-benefit medicines. You can see that the blue and red distributions are awfully close to each other, with no statistically significant differences between them. From this chart, you can also immediately see why the US is the major pharmaceutical market globally, with drug costs roughly 1.3-times higher than in the European countries.

    In summary, new drugs do not always mean innovation, breakthroughs are not always proven to be true breakthroughs, and a high price does not mean high value. Did any of these statistics surprise you? On an optimistic side, we should remember that this is just theory and does not reflect the real-world use of these drugs. Patients will not switch to a new drug which works just as well as what they are already on, and payers would restrict coverage for high-price drugs with dubious efficacy.

    Approvals gone wrong – Avastin in metastatic Breast Cancer

    However, as we alluded to at the start, there are unfortunately cases where drugsare proven to be quote unquote useless. Let’s check out two examples, and then dive into some chemistry.

    The first one is Avastin, which is a VEGF-targeting antibody which suppresses the growth of new blood vessels. This hinders supply nutrients to the cancer, slows its growth, and therefore slows cancer progression.

    The FDA approved Avastin in a broad set of tumors. So, we can see the theme of supplemental indications mentioned in the first part. The problem really was around its accelerated approval in metastatic breast cancer (2008). At the time, the FDA’s Oncology Advisory committee, so an outside advisory panel, had actually recommended 5 to 4 against the approving Avastin in metastatic breast cancer. This mixed opinion was because Avastin at the time did not extend life.

    We look at the details of the clinical study comparing Avastin as an add-on to chemotherapy. Overall survival – the time from trial entry to patient death – is the gold standard primary endpoint in cancer trials but takes more time and patients to collect. Avastin missed the mark on this important metric. Avastin’s OS is numerically higher, 26.7 months vs. 25.2 months, but this is not statistically significant as indicated by a p value of higher than 0.05.

    However, progression free survival improved significantly. PFS is the time between treatment start and first evidence of disease progression, or also death. PFS data is available earlier than OS, so it serves as a surrogate endpoint. So essentially, Avastin reduced the speed of progression by more than 5 months, but patients were ultimately not living longer. Also, their subjective quality of life did not increase either. You might think: If the drug slows down progression, should we approve it nevertheless?

    What was The Problem?

    An additional problem was the overall 20% increase in adverse events with Avastin. Toxic effects like hypertension or infections increased significantly. This resulted in 6 deaths due to Avastin. So, considering all this evidence, the accelerated approval was quite optimistic but understandable given the lack of other treatments that showed similar PFS benefit.

    As we learned, accelerated approvals require parallel studies which intend to confirm the drug’s benefit. However, the opposite happened.

    Looking at the AVADO trial comparing two doses of Avastin, the extended PFS was still there. However, with just under 1 month difference between trial arms, this was significantly lower than expected. More importantly, patients on Avastin had numerically shorter OS. Because of the high p value, we can’t really say if this means Avastin is indeed worse or just equal to chemo. This led the FDA to withdraw the metastatic breast cancer indication for Avastin.

    Interestingly, the European regulator EMA did not follow suit. In their view, benefits outweigh risks given positive albeit small PFS benefit and lack of statistically significant detrimental effect on OS.

    Approvals gone wrong – rucaparib in 3rd line ovarian cancer

    The second case study is Rucaparib, which was indicated, among other uses, for third-line treatment in ovarian cancer. It belongs to the class of PARP inhibitors which interfere with DNA repair mechanisms.

    Like the results for avastin, rucaparib extended the median progression-free survival by 5 months. Patients with DNA repair deficient tumors responded even better as they are more prone to PARP inhibition. This seemed like a solid benefit at the time – but can you guess the problem?

    Four years after its approval, now in 2022, more mature data on overall survival came in. The harsh reality – across different data cuts, patients on treatment again did not live longer. Again, we need to check the p value to see that even in the BRCA mutated sub-group, the potential strong responders, the seemingly beneficial effect is not statistically significant. This led to a voluntary withdrawal in the third-line indication by the company. Unfortunately, a somewhat desperate filing of rucaparib as a first-line therapy by the company did not work out either.

    If you watched my previous video, you would remember that pharmaceutical companies burn a lot of money on development and operations. Clovis tried to cut costs through lay-offs and raise additional money, but ultimately had to throw in the towel and file for bankruptcy.

    In summary, PFS benefit does not necessarily translate into true survival benefit – which is ultimately most important. Also, we saw that the FDA and EMA can reach different scientific conclusions looking at the same data.

    organic synthesis of rucaparib

    Finally, it’s chemistry time. Here we have two things to check out. First, we will look at just one part of Rucaparib’s original large scale process route, and second, go through a more efficient synthesis in full.

    The process route, albeit long, has an interesting reaction early on. It starts with a nitration of this benzoic acid – which selectively nitrates meta to the acid. So far, nothing special – most of you should know the selectivity. Doing a nitration with 23L concentrated nitric acid is nothing so sneeze at, but we are more eager to see what happens after this step, and a simple esterification. It’s a Leimgruber-Batcho indole synthesis which leverages the moderate acidity at the benzylic position of these nitroarenes. In the first step, the benzyl anion is formed and attacks the reagent, dimethylformamide dimethylacetal. This adds one carbon to the system and after spontaneous elimination of methanol, a conjugated link is formed.

    The second step of the indole synthesis is the reduction of the nitro-group. The liberated nucleophilic aniline can intramolecularly cyclize with the iminium, and again eliminate dimethylamine to create the aromatic indole. Although you might expect that immediate intramolecular attack in a 5-endo-trig fashion would give an anion that is very much stabilized through the ester group, I think that’s kinetically disfavoured work due to Baldwin’s rules.

    Second synthesis of rucaparib

    The remaining steps are not revolutionary so we will instead look at the very direct synthesis published in 2022. The starting material is already highly functionalized, but you can buy this commercially so it’s fair game. The first step is a Heck-reaction with the highly reactive aryl iodide. Next, the aryl amine was condensed with an aldehyde bearing the other half of rucaparib. At this point, we essentially already have all atoms that we need already, it’s just about linking them and getting to the right oxidation states.

    To create the indole, the chemists used a cyanide-catalyzed imino-Strecker reaction – you might remember this one as a prime example of Umpolung chemistry. The mechanism starts with nucleophilic addition of cyanide to the aldimine. The negative charge first sits on nitrogen, but rapidly tautomerizes alpha to the nitrile. Now, we have the typical Stetter 1,4-conjugate addition onto the vinyl nitrile. Finally, just like we’ve seen in the previous Leimgruber-Batcho synthesis, elimination delivers the indole. This regenerates the catalytic cyanide which is why the reaction works with just 20 mol% of sodium cyanide.

    Well, what do we do next with the nitrile? You’ve guessed it – we need to reduce it to the amine, and link it to the ester. Because typical hydrogenation did not result in any reaction, the authors looked for other reducing agents. Interestingly, the generation of nickel boride from nickel chloride and sodium borohydride worked smoothly and chemoselectively, leaving the ester group in peace. The lactamization occurred spontaneously in situ, so that was quite convenient as well. The ultimate step was a simple deprotection of the amine sitting at the other side of the molecule, completing the total 5-step synthesis.

    That’s it for this time. As always, I will catch you in the next one.

    Key References:

    • Therapeutic value of first versus supplemental indications of drugs in US and Europe (2011-20): retrospective cohort study: BMJ 2023, 382, e074166
    • Association between FDA and EMA expedited approval programs and therapeutic value of new medicines: retrospective cohort study: BMJ 2020, 371, m3434$
    • rices and clinical benefit of cancer drugs in the USA and Europe: a cost-benefit analysis: Lancet Oncology 2020, 21, 664
    • The US FDAs withdrawal of the breast cancer indication for Avastin (bevacizumab): Saudi Pharm J 2012, 20, 381
    • Efficacy and safety of bevacizumab in combination with docetaxel for the first-line treatment of elderly patients with locally recurrent or metastatic breast cancer: Results from AVADO: Eur J Cancer 2011, 47, 2387
    • Paclitaxel plus Bevacizumab versus Paclitaxel Alone for Metastatic Breast Cancer: N Engl J Med 2007, 357, 2666
    • Multikilogram Scale-Up of a Reductive Alkylation Route to a Novel PARP Inhibitor: OPRD 2012, 16, 1897
    • Total Synthesis of Rucaparib: JOC 2022, 87, 4813
  • World’s Most Expensive Drug: Greedy or Fair?

    World’s Most Expensive Drug: Greedy or Fair?

    Watch the video on YouTube or read the blog below!

    What is the most expensive drug in the world? Imagine a single dose of medicine priced at $3.5 MILLION. Since the approval of the gene therapy Hemgenix in late 2022, this is a reality. This eye-popping price is easy to scrutinize, especially if you know the truth behind most newly approved drugs. Drug manufacturers think these prices are still fair, with some even winding down operations due to pricing disagreements. Also, it couldn’t be more fitting that one of the companies we will talk about, who is selling a very simple drug for one million a year, very recently saw itself forced to lay off 25% of its staff, maintain loans and preserve cash burn to simply keep up its operations for another year.

    After reading this post, you will know:

    • Why soaring prices do not always equal large profits. You will not understand why some therapies, as crazy as it sounds, cannot be sold for prices under hundreds of thousands of dollars
    • The answer to the question “what is the most expensive drug”?, as well as top contenders
    • The chemical synthesis of the most expensive small molecule drug, used for an ultra-rare disease occurring in 1 out of 40 million people
    • How to estimate drug sales for gene therapies

    most expensive drug in the world – what is the bar?

    Hemgenix approval dethroned the gene therapies Skysona and Zynteglo, both developed as rare disease therapies by the company BlueBird Bio. With costs per dose of 3 and 2.8 million respectively, they currently land on number 2 and 3. The Institute for Clinical and Economic Review, a non-profit organization publishing clinical and cost-effectiveness analyses of treatments, deemed the true value of Skysona to not be too far off. The company itself postulated normal standard of care consisting of regular transfusion treatments cumulate to total healthcare costs of $6million over a patients life time. Comparing this with Soliris, which had been the world’s most expensive drug for some years in the past decade, we can see that in certain diseases such as myasthenia gravis, a cost-effective price would require a more than 95% discount on the annual price.

    So, million-dollar gene therapies are actually not bad in terms of value provided. We have also seen some companies offer outcome-based deals, where for example 80% of the price is refunded if the patient does not respond to therapy.

    Gene therapies are also less-overpriced if we look at the cost that it takes to produce them. Producing the annual supply of the antibody Soliris, costs less than 1% of its price. In contrast, gene therapies require bespoke manufacturing and supply chains, with fully loaded manufacturing costs reaching over 200 thousand dollars. But maybe you’re wondering why companies wouldn’t sell them at a lower price let’s say, half a million, and still make a decent profit? First of all, these variable costs do not include the large capital investments required for manufacturing facilities.

    Drug R&D Costs

    But as anyone who had more than 30min of business school will tell you, there are many more direct and indirect costs behind drugs.

    Currently, it costs roughly 2.3 billion dollars to research, develop and launch a new drug. As you can see, R&D costs have been trending up, roughly doubling during the last decade. Some drugs are even higher than 3-5 billion. These large upfront investments are why a company will typically command as high of a price as it can reasonably get, to try to maximize internal return on the dollars.

    But if we look at the peak sales potential of drugs, we can see that this decreased instead of increased in recent years. Basically, development is getting more expensive while returns are getting smaller.

    Don’t forget that there are other costs beyond the manufacturing cost we highlighted. Companies deploy various functional teams to drive uptake of drugs – the easiest to think about are sales and marketing. On a company level, selling, general and administrative cost are usually around 15-30% of net revenues. On a product level, this obviously depends on the lifecycle stage, with new drugs having much more investments behind them than established products which are more like cash cows.

    Additional Factors: Discounts and risk

    Another important thing to note are gross-to-net price discounts. You see, the list price you read in the news refers to a theoretical price which is actually never paid. In the extremely convoluted US healthcare system, manufacturers give discounts to various stakeholders involved in access, distribution, or other things. These typically untransparent gross-to-net discounts translate into actual net sales for companies which can be less than 50% of the original list price.

    One of the underlying problems behind high development costs is the low probability of clinical success. Science and drug development is inherently high risk, high-reward. While big companies with more than a hundred projects will always get something out of their R&D funnel, smaller companies can get wiped out if several drugs turn out to simply not work as hoped. This is why no company will ever price drugs at minimal margins, because prices need to be high to compensate for large R&D costs AND offer protection against critical pipeline setbacks.

    Lonafarnib: another expensive drug

    This molecule was originally discovered by Schering-Plough more than 2 decades ago as an investigational cancer drug. After development for oncology was discontinued due to lack of efficacy, and Schering-Plough was acquired by Merck, a deal was struck with the small biotech Eiger Pharmaceuticals. Eiger originally wanted to develop the molecule for hepatitis D, but was also introduced to the Progeria Research Foundation by Merck. This non-profit research organization found that the mechanism underlying lonafarnib’s activity was also involved in progeria.

    This heart-breaking disorder causes rapid-aging in children. With a prevalence rate of 1 case in 20 million individuals, this is an ultra-rare disease. Patients die at an average age of 13 years, perversely from heart attack or stroke – so the unmet need is massive.

    This always fatal disease is caused by mutation in the gene coding for a protein called lamin A. A single cytosine-to-thymine mis-spelling is the most common mutation, and has critical effects.

    Normal lamin A is modified with a farnesyl group which helps direct it to the nuclear lamina (a shipping tag). The tag is subsequently cut-off from normal lamin A. However, the progerin cannot be defarnesylated – meaning the un-natural shipping tag stays on the protein – and this interferes with a myriad of different cellular mechanisms. Because lonafarnib is a farnesyl transferase inhibitor, it prevents the addition of farnesyl groups to progerin to start with. Due to the missing shipping tag, the proteins do not reach their destination as easily but also do not accumulate and mess up the nuclear lamina either.

    Although far from a cure, the simple farnesylation-block has significant clinical effects. Treated patients have significantly lower mortality risk and over the course of 11 years, live roughly 2.5 years longer. It also had a good safety profile with small number of discontinuations.

    How Expensive is it?

    As this is a significant improvement in ridiculously small patient population, we can start to understand why this medicine costs around one million a year, despite being a simple small molecule. This makes it the most expensive small molecule drug. There are not that many sales to be made – as many of the 400 children living with progeria worldwide were already dosed in your clinical trials. Of course, Eiger could theoretically sell it for cheaper, but you also must consider cost of the several clinical trials which lonafarnib was tested in, including its oncology history. So even though the price looks Machiavellian, the company actually lost 200 million dollars in the last three years.

    The current R&D spend is focused on the development of lonafarnib in hepatitis D, which is a much bigger commercial opportunity but will also come with lower pricing. They also have additional pipeline projects, so all this cash drain resulted in them recently communicating a 25% workforce reduction. In summary, we see that having the most expensive small molecule drug doesn’t necessarily make life easy.

    Chemical Synthesis

    Lonafarnib was synthesized on a up to mind-blowing 100kg scale when it was planned as an oncology drug. If you compare the key intermediate to the target, you will notice that we need to introduce an aryl bromide group. How is this done selectively? If you ever had some electrophilic aromatic substitution theory, you would know that other positions are more electronically activated due to the present chloride substituent.

    The team approached this starting with a single nitration, giving rise to two nitro regioisomers. Regardless of their position, the effect is the same. A novel reduction system with catalytic iodide proved to reduce the nitro group as well as ketone, saving a step. A mix of hypo-phosphorous and phosphorous acid avoided halogen side reactions while reducing both groups. However, they also observed severe foaming at the beginning of the reaction. For more control, they first added H3PO3 to reduce the nitro group, and then H3PO2 to reduce the ketone. This system proved better than hydrogenation or metal catalysis which would have decomposed the aryl halide groups and introduced potential contaminants.

    With the amine in place, the desired bromination product is favored through either ortho-direction in one of the isomers, or para-direction in the other. After removal of the amino groups, the most acidic site is between the aryl rings. The addition of LDA, quinine and this electrophile led to a chiral alkylation, proceeding with impressive 95% ee. Gratifyingly, they were able to recycle the quinine – quite important if you run things on a double-digit kilo scale. Next, a diastereomer salt formation enriched ee to 99%. Last, a final amide formation introduced the missing part – and a one-pot Boc deprotection and urea formation gave the product.

    Hemgenix in hemophilia B: The world’s most expensive drug

    Now that the chemists are happy, we can pivot to the most expensive drug. For this, we need to understand a disease called hemophilia B, an inherited bleeding disorder caused by a deficiency of the coagulation factor IX. This disorder is characterized by frequent and recurrent bleeding into joints or soft tissue, leading to chronic pain, disability, and impaired quality of life.

    The current standard-of-care for haemophilia B includes life-long on-demand and prophylactic replacement therapy with FIX concentrates. This replacement therapy is effective at reducing bleeding episodes and is well tolerated – although some patients develop antibodies, making them resistant to replacement therapy. These repeated injections become extremely expensive over a patients lifetime, with most estimates well beyond $10 million. ICER says 3 million dollars would be a very reasonable price – so Hemgenix is not too far off. So clearly this one-time treatment has a lot of impact, but how does this work biochemically?

    How do Gene therapies work?

    Gene therapies use engineered viruses as carriers or so-called vectors of genetic information to correct a patient’s genetic code, ultimately restoring the proper functions of vital proteins. For Hemgenix, this vector is adeno-associated virus or AAV-based. It’s like a train or truck delivering cargo. As viruses are doing virus things, they can enter cells and integrate or transduct the missing gene into the cell.

    Compared to normal viruses, these AAV are modified to lose their replicative abilities, rendering them safe as therapies for humans. In addition, a DNA regulatory element called promoter limits the transgene expression in only the desired tissue. In this case, it’s the liver, as factor 9 is produced in hepatocytes and released into circulation from there. The actual factor 9 gene being incorporated is basically a factor 9 protein on steroids, which is 7-times more activity than wildtype due to a single mutation. This allows for a lower AAV vector dose which in turn decreased averse immune reactions by patients.

    As you might expect, Hemgenix was superior to replacement therapy in a mid-sized trial with 54 patients. This led to a significantly lower rate of bleeding events as the primary endpoint. 96% of patients were able to stop replacement therapy. This transformational benefit shows in the increased factor IX activity of patients. Severe hemophilia is characterized with untreated factor IX activity below 5%. This also approved, with immediate and sustained increase post-treatment. Given the adult population, the approval is only in patients over 18 years. In summary, instead of continuously replacing factor 9 exogenously multiple times a week, incorporation of the missing gene solves the problem for good – or at least for more than 20 years.

    How can we estimate drug sales?

    Hemgenix is the world’s most expensive drug – so will it lead to the highest profits?

    You might know that total yearly sales equal sales per year multiplied with the cost per patient. We already know the latter – but what is the true number of patients that will get treatment?

    Well, there’s only approximately 6000 people with hemophilia B in the US. Let’s assume this population grows by 1% each year. Do you remember if we can treat all of them? Nope! The approval is only for adult patients, which might be around 80% of patients, and only in cases with severe hemophilia B, maybe around 60% of the patients. So 6K times 80% times 60% – some of you might do it in their head –is 2’880. But why is the number I have here different? Well, I mentioned some patients develop antibodies or inhibitors to factor IX replacement therapy. Because Hemgenix does not have data in these patients, we will exclude them too. This reduces the eligible pool by 2%.

    Gene THerapies Are Unique

    Now just multiply this number with price? Think again! Will all patients use Hemgenix, immediately? Clearly not – most of them will never receive it due to limited coverage due to the high cost, and the uptake will only gradually increase with time.

    It’s probably fair to say that not much more than 10% of patients will ever get Hemgenix, and we also need to assume a build over time – let’s say a one or two percentage points every year. Hemgenix is a one-time treatment. It practically cures patients or it “does not work”. Therefore, more patients being treated reduces the addressable pool.

    But hey, this therapy will also not be the only one. There is another hemophilia B gene therapy (Pfizer/Spark). Even if we assume that the first-to-market therapy will dominate, the second product will also have some penetration. Obviously, this all depends on its relative efficacy, safety and importantly price. Here, I simply assumed that the new product would have 50% of Hemgenix’ uptake, delayed by one year.

    This means the blue line gives us the actual pool we can treat with each product in every year, factoring in the total number of patients previously treated with Hemgenix and the Pfizer/Spark product. I hope you could follow.

    Now we can take the number of new patients treated with Hemgenix, calculated by multiplying the phased penetration with the untreated addressable pool, and multiply it with the price per patient. There are also some less important pricing assumptions.

    How Profitable is The World’s most expensive drug?

    Do you notice anything about the result? The number of Hemgenix-treated patients actually peaks after just a few years, maybe even staying below 200 patients per year. This translates into peak sales of $630M.

    Definitely nothing to sneeze at, but we also have to be real here – many mega-blockbusters with lower pricing are much more lucrative for companies due to steady revenues and higher number of patients. Throw the quarter million-per unit production cost on top, program development cost, and all your other functional and SG&A cost … Just because something is the world’s most expensive drug, doesn’t mean it’s highly profitable or overly “capitalistic”.

    And let’s once again re-iterate the topic of low probability of success. With bad luck, developers can easily risk all profits of one drug while financing others. Even the simplest medicines can simply fail to demonstrate efficacy – but the development of innovative therapies like gene or cell therapies is another beast. Very recently, the FDA put a clinical hold on Arcellx’s Phase 2 investigating a CAR-T cell therapy following the death of a patient. Just half a year prior, Gilead invested over $300M to secure development and commercialization rights. This shows how fast the profits gained on some products can disappear.

    Thank you for sticking through to the end! As always, I hope you’ve learned something!

    Key references

    • Lonafarnib: First Approval | Drugs. 2021; 81(2): 283
    • A Novel Iodide-Catalyzed Reduction of Nitroarenes and Aryl Ketones with H3PO2 or H3PO3: Its Application to the Synthesis of a Potential Anticancer Agent | Org. Lett. 2011; 13 (19): 5220
    • Impact of farnesylation inhibitors on survival in Hutchinson-Gilford progeria syndrome | Circulation 2014;130(1): 27
    • Gene Therapy with Etranacogene Dezaparvovec for Hemophilia B | N Engl J Med 2023; 388(8): 706
    • Etranacogene dezaparvovec for hemophilia B gene therapy | Therapeutic Advances in Rare Disease. 2021;2. doi: 10.1177/26330040211058896
    • Structure-activity relationship study to improve cytotoxicity and selectivity of lonafarnib against breast cancer cells | Arch Pharm (Weinheim) 2023; 356(4): e2200263
    • Deloitte | Measuring return from pharmaceutical innovation 2022 – IQVIA | Global Trends in R&D 2021