Dennis X. Hu

Zuranolone (ZURZUVAE™) is an oral positive allosteric modulator of CNS GABA signaling developed by Sage Therapeutics, in collaboration with Biogen, which was approved in August 2023 by the FDA for the treatment of postpartum depression (PPD). In 2019 Sage had received approval for brexanolone (ZULRESSO™), an IV formulation of the endogenous GABA PAM neurosteroid hormone for PPD, but an oral drug is expected to greatly increase access to treatment. Zuranolone was also investigated for major depressive disorder, although the FDA declined to extend approval for this indication.

The discovery that individuals with null mutations in the NaV1.7 exhibited pain insensitivity sparked interest in targeting NaV1.7 to potentially treat pain. Despite the potential of selectively inhibiting sodium channels like NaV1.7, NaV1.8, and NaV1.9 for pain management, developing selective inhibitors suitable for clinical use has proven challenging. This article complements our coverage of VX-548, NaV1.8 as a critical target in pain management, and our NaV1.8 compound roundup and provides a reminder of noteworthy preclinical and clinical NaV1.7 small molecule inhibitors as of April 2024.

February 2024 was filled with notable scientific achievements and partnerships. Gilead and Novartis inked billion-dollar acquisitions, and Novo Nordisk and NeoMorph agreed to a $1.46B deal to discover molecular glue degraders. Additionally, Vertex introduced a promising new treatment for cystic fibrosis that is potentially superior to Trikafta. Takeda also made strides by advancing their OX2R agonist TAK-861, for treating narcolepsy type 1, into Ph. III clinical trials. Read this news roundup for more details on these and other drug discovery news stories that you may have missed from Feb 2024

Nrf2/KEAP1 modulation has been pursued since the discovery that dimethyl fumarate and its metabolite protect CNS neurons via up-regulation of Nrf2-depdendent activities. Compounds with greater selectivity have been sought for many years, culminating with the approval of the KEAP1 inhibitor, omaveloxolone. Vividion disclosed their efforts to identify the covalent KEAP1 inhibitor, VVD-702. This ACS Spring 2024 disclosure is an excellent case study for covalent hit finding using chemoproteomics, covalent compound optimization, and the use of an uncommon but surprisingly stable covalent warhead.

Inaxaplin (VX-147), developed by Vertex, is an inhibitor of APOL1 channel activity currently in a Ph. II/III pivotal study for the treatment of chronic kidney disease caused by specific variants of the APOL1 gene. It was recently granted Breakthrough Therapy designation by the FDA and PRIME designation by the EMA. The discovery story, which is an excellent case study for the use of MetID. Inaxaplin has been called “the most important genomic-driven drug discovery for chronic kidney disease this century”, acting on a target with a fascinating human genetic validation story.

NaV1.8, a member of the voltage-gated sodium channel (NaV) family, is predominantly expressed in peripheral sensory neurons. Based on rodent NaV1.8 knockout and knockdown studies and a 2012 report of gain-of-function mutations in humans, NaV1.8 has been linked to nociceptive, inflammatory, and neuropathic pain, including chronic neuropathic pain. This compound roundup provides a historical recap of both preclinical and clinical NaV1.8 inhibitors that shaped the landscape for the new era of pain management we are witnessing today.

The impact of small and mid-sized biotech companies has become increasingly important. The shift from large pharma dominance to a biotech-driven era of drug discovery presents challenges to the traditional model of education for emerging medicinal chemists. Industry leader Dean Brown recently highlighted challenges for modern medicinal chemists starting in biotech who face fewer mentoring opportunities and are often propelled into leadership positions sooner than their counterparts in big pharma. Here we share how our team of former industry scientists at Drug Hunter can help.

NaV1.8 has become an industry focal point in the pursuit of pain therapeutics thanks to the success of Vertex’s selective inhibitor, VX-548, in Ph. III clinical trials for acute pain and Ph. II results in diabetic peripheral neuropathy. Unlike opioid receptor modulation, NaV1.8 inhibition does not carry the same addiction risks in part due to its lack of expression in the brain. Following our recent review of the leading NaV1.8 inhibitor VX-548, this article provides more details on the history of target validation for NaV1.8 in pain and why this could be the new frontier for pain management.

Vertex’s VX-548 is a potential first-in-class, exquisitely selective, oral NaV1.8 inhibitor that recently captured headlines for its positive Ph. III data. With the ongoing opioid epidemic throughout the US, there is an urgent unmet medical need for non-addictive pain medications as alternatives to opioids. They plan to file an NDA by mid-2024 for the treatment of moderate-to-severe acute pain. This case study highlights what’s publicly known about Vertex’s journey in pain leading up to the Ph. III readout for VX-548, and why this is such a watershed moment for pain management.

STC15 is Storm Therapeutics' first-in-class and first-to-clinic inhibitor of the post-transcriptional RNA modifier, METTL3, which progressed from HTS hit to clinical development in less than three years. METTL3 inhibitors have been previously identified, but no METTL3 inhibitors have entered clinical development until now. In this article, we explore METL3 as a therapeutic target, highlight the discovery story of STC15, its fascinating mechanism of action, provide the latest clinical development update, and much more.

There were several key clinical readouts in Dec. 2023 for small molecules in areas ranging from non-opioid pain management to sickle cell disease. While most results were positive, one pivotal trial led to a program discontinuation. This roundup highlights key data recently reported for selected molecules targeting NaV1.8, BTK, and more.

Last December, the pharmaceutical industry witnessed many important updates for clinical molecules, ranging from neurology-based therapies to anti-tumors and radiopharmaceuticals, in addition to the unfortunate discontinuations. In case you missed it, here is a recap of the most notable news updates in the pharma world for December 2023

An aldosterone synthase inhibitor, a pFOX inhibitor, a brain-penetrant MEK1/2 inhibitor, and several other modulators had major trial results disclosed recently. In case you missed them, this article rounds up key results of general industry interest, with representative patent structures for undisclosed molecules. Read this review to get a sneak peek at potential future approvals, as well as some informative disappointments.

Last November saw several notable updates for molecules we previously covered on Drug Hunter. These updates ranged from positive Ph. III results and NDA submission to failed clinical trials and discontinuation, for TTR, FXIa, GLP-1R modulators, and more. In case you missed it, this article is a round-up of these clinical updates from Nov. ’23.

Several multi-million dollar acquisitions or license agreements took place in November 2023 for hot drug targets, with assets from selective PARP1 inhibitors to GLP1R agonists, and others. This recent news roundup highlights the notable acquisitions by pharma companies for rights to molecules in a range of different indications, with illustrative patent examples for undisclosed structures.

Kymera's KT-474 is the first oral degrader to demonstrate activity in clinical trials outside cancer and Sanofi recently started a Ph. II trial with the molecule in AD, restoring life to IRAK4 as an immunology target. This article highlights why Kymera’s KT-474 program is scientifically notable, including how it differentiates from small molecule inhibitors, potential competitiveness with biologics, the first reported cryo-EM ternary complex of a heterobifunctional degrader, and why this 2023 Molecule of the Year Nominee will likely be considered a “landmark in drug discovery” for some time.

KIN-3248 (Kinnate Biopharma) is a next-generation, irreversible, pan-fibroblast growth factor receptor inhibitor (FGFRi) in a first-in-human (FIH) dose-escalation study (NCT05242822) in adults with advanced tumors harboring FGFR2 and FGFR3 gene alterations. The program is an excellent case study for rational covalent drug design to address kinase mutations while maintaining sufficient PK properties for oral daily dosing in humans.

Peptidic GLP-1R agonists have received significant media coverage over the past year for their astounding efficacy in several indications. GLP-1R agonists now appear to be efficacious in reducing heart disease risk and in treating certain chronic kidney diseases, expanding their likely future use. This review by Oliver Philps provides an overview of GLP-1 agonists and where they fit in the treatment of diabetes, how the peptide drugs evolved over time to today’s weight loss medications, and what to expect next...

Nuvalent’s lead compound, NVL-520, is an oral, brain-penetrant, TRK-sparing, and potential best-in-class ROS1 kinase inhibitor that recently entered Ph. II of the ARROS-1 trial (NCT05118789) in patients with advanced ROS1-positive NSCLC. This article highlights what makes the Nuvalent’s NVL-520 program scientifically notable, including what gives it a potential best-in-class profile as a ROS1 inhibitor, the emerging toxicology of hard-to-avoid off-targets, an interesting synthetic route to the small macrocycle, and more.

STX-478 is a wild-type-sparing, oral, CNS-penetrant, novel allosteric inhibitor of mutant phosphatidylinositol-3 kinase α (PI3Kα), targeting a cryptic pocket near the ATP-binding site. PI3Kα plays a central role in many cancers, and has been recently highlighted in coverage of 2021 Molecule of the Year nominee and PI3Kα degrader inavolisib. Currently approved PI3Kα modulators are limited by their off-target activities on WT PI3Kα and other kinases, leading to significant side effects including hyperglycemia and rash.

Genentech’s GDC-6599 is the first oral TRP Ankyrin 1 (TRPA1) antagonist to reach Ph. IIa (NCT05660850) for chronic cough after preclinical studies and a Ph. I trial showed it was well-tolerated, in contrast to prior molecules. The transient receptor potential (TRP) family of ion channels has been the subject of intensive drug discovery efforts due to their critical role in the development and progression of pain, itch, and respiratory conditions.

Jecure’s JT001 is a selective inhibitor of NLRP3 inflammasome and among the earlier compounds in this now highly competitive space. In 2018, Genentech bought Jecure Therapeutics for an undisclosed amount, gaining access to Jecure’s NLRP3 inhibitor JT001. While there are many other NLRP3 inhibitors now in the space, JT001 is an interesting example of an initial attempt to overcome liver toxicity with well-known NLRP3 inhibitor MCC950. However, the molecule ran into its own kidney toxicity issues, making this an intriguing toxicology case study.

Acoramidis (AG10), an oral, second-generation stabilizer of the tetrameric transthyretin (TTR) protein, was submitted for FDA approval on Dec. 5, 2023 by BridgeBio for the treatment of transthyretin amyloid cardiomyopathy (ATTR-CM). The rare but potentially fatal disease is characterized by amyloid deposits in heart muscle. The molecule has the potential to be best-in-class relative to Pfizer’s $2.4B+/yr blockbuster tafamidis. This story highlights early experiments validating TTR stabilization, why enthalpy of binding was key, how it binds TTR, its 30-mo clinical data, and more.

RAPT Therapeutics, formerly known as FLX Bio, was spun out of Flexus Biosciences after its billion-dollar acquisition by BMS for Flexus’s immuno-oncology IDO1 program. While the IDO1 molecule unfortunately did not show efficacy in Ph. III trials in combination with BMS’s PD-1 inhibitor nivolumab, RAPT Therapeutics appears to be having better luck with its potentially first-in-class CCR4 inhibitors FLX475 (for immune-oncology) and RPT193 (for atopic dermatitis). Oral FLX475 (100 mg QD, human T1/2 = 72 h) appears to shrink EBV+ tumors both as a monotherapy and in combination

Atrasentan (ABT-627/A-127722) is an ETA receptor antagonist that was originally discovered by Abbott (AbbVie) in the 1990s to treat prostate cancer. Unfortunately, clinical data with the compound in prostate cancer was insufficient for approval, and AbbVie pivoted the compound to chronic kidney diseases instead, ultimately conducting a large, 5,000+ patient trial (SONAR) that was published in 2019.

Vorasidenib (AG-881) is a brain-penetrant allosteric inhibitor of mutant isocitrate dehydrogenases 1 and 2 (mIDH1/2) from Agios and Celgene that made headlines summer 2023 due to its stunning efficacy for treatment of glioma in patients with mIDH1/2.

This Featured Case Study reviews how it was discovered, how it works, and why it matters.

AZD4747 is a CNS-penetrant, oral KRAS G12C covalent inhibitor for the treatment of CNS-metastatic KRAS-mutant cancers. KRAS inhibitors have tended to be quite large and fall outside the range of physicochemical properties generally required for CNS permeability. (MW < 360 Da, cLogD < 2, TPSA < 90 Å2. AZD4747 is much smaller than marketed KRAS G12C inhibitors but maintains exceptional cellular potency. The team also encountered an unexpected toxicity that scientists working on covalents should pay attention to.

Obtaining adequate drug exposure in the brain is key to treating CNS diseases effectively. Recently, Dennis Koester gave us a crash course in CNS drug discovery in a Drug Hunter Flash Talk. Here, he sums up some key points on how to find compounds that cross the blood-brain barrier.

LRRK2 has been a hotly pursued drug target for Parkinson’s Disease based on human genetics. Clinical advancement of LRRK2 inhibitors was initially stalled by concerns about on-target lung findings in primates, but these were ameliorated by a Merck/Genentech/Pfizer/MJFF study showing that these lung changes were reversible, and Biogen/Denali has currently a small molecule (BIIB122/DNL151) in Ph. II (NCT05348785) after demonstrating safety and CNS exposure in 145 healthy patients in Ph. I (NCT04557800)

The arachidonic acid (AA) metabolite, 20-hydroxy-5,8,11,14-eicosatetranoic acid (20-HETE), has been extensively studied as a modulator of kidney function and a mediator of kidney diseases over decades. The receptor for 20-HETE, the G-coupled protein receptor GPR75, was only recently identified (2017), and GPR75/20-HETE pathway modulators are of industry interest in many disease areas including obesity (e.g. 2020 Regeneron patent filing) and kidney diseases (e.g. 2018 Taisho patent filing).

Orforglipron is an oral non-peptide glucagon-like peptide-1 (GLP-1) receptor partial agonist that entered Ph. III for obesity and type-2-diabetes mellitus (T2DM). This 2020 and 2023 Molecule of the Year nominee (nominated initially back when it was still in Ph. I) was first discovered by Chugai Pharmaceuticals under the name OWL833, then licensed by Eli Lilly for worldwide development under the name LY3502970. The article discusses where it sits in the GLP-1R agonist landscape, why it’s scientifically notable, how it works with illustrations from cryo-EM structures, its synthesis, and more.

Ziretaxestat, an oral autotaxin (ATX) inhibitor originated by Galapagos, once garnered excitement as the first molecule to complete a Ph. III clinical program in idiopathic pulmonary fibrosis since the approvals of nintedanib and pirfenidone. Following the disappointing clinical data and discontinuation of the molecule, this annotation revisits ziritaxestat in the context of other inhibitors, recaps the therapeutic hypothesis and how it was discovered, summarizes notable molecular properties for drug discovery scientists, and discusses what happened and what’s next.

Targeted Protein Degradation (TPD) allows for elimination, rather than inhibition, of proteins by exploiting cells’ own protein clearance mechanisms. While traditional inhibitors can be very effective at preventing a protein from undertaking a particular function, blocking protein activity...

A diaziridine-based tumor-activated prodrug for AKR1C3-expressing cancers from a defunct Bay Area biotech. OBI-3424 (formerly TH-3424) is a tumor-activated prodrug in Ph. II that releases DNA-crosslinking diaziridine phosphamide (remniscent of thioTEPA) upon activation by the NAD(P)H-dependent aldoketoreductase, AKR1C3, which is differentially expressed in many cancers. The molecule was originated at...

Genentech announced that fenebrutinib (GDC-0853), a non-covalent BTK inhibitor entering Ph. III, showed significant human CNS exposure and reduced new brain lesions in Ph. II for relapsing multiple sclerosis. Fenebrutinib is the only reversible BTK inhibitor in Ph. III for MS, and has the opportunity to differentiate on safety relative to covalent inhibitors. This case study highlights notable challenges overcome in the discovery of fenebrutinib including surprising metabolism, animal-specific on-target toxicity, and more.

The accelerated approvals of Ras(OFF)-targeting KRAS G12C inhibitors sotorasib and adagrasib, decades in the making, marked the beginning of a new phase of KRAS drug discovery. While an increasing number of follow-on KRAS inhibitors are emerging with similar mechanisms of action, Revolution Medicines’ 2023 Molecule of the Year Nominee, RMC-6291, is representative of a completely novel approach that could become a strong addition to the clinical toolbox for KRAS, but also serves as proof-of-concept for a new class of small molecule therapeutics entirely.

Macrocyclic molecules, containing 12 or more atoms in a ring system, are increasingly prevalent in drug discovery, with over 67 macrocyclic drugs approved so far and several notable examples of clinical success highlighted on Drug Hunter recently, including MK-0616 , repotrectinib , and pacritinib . By imparting conformational restraint and [...]

Vadadustat (Vafseo) from Akebia Therapeutics is an oral hypoxia-inducible factor prolyl-4-hydroxylase domain (HIF-PHD) inhibitor developed for anemia in patients with chronic kidney disease (CKD). It received FDA approval on March 27th, 2024 for patients on dialysis for at least three months, after regulatory challenges including an earlier complete response letter due to safety concerns. This makes vadadustat the second FDA-approved HIF-PHD inhibitor for the treatment of anemia in CKD for dialysis-dependent patients after GSK’s daprodustat’s approval in Feb. 2023.

It's hard not to think about infectious diseases at the moment, but it's a great time to review the drug discovery literature. One area of drug discovery that has deep roots in infectious disease research is targeted covalent inhibition. Targeted covalent inhibitors form covalent bonds with discrete targets (as opposed to [...]

At the time of this writing Kim Huard was one of Genentech’s Senior Scientists, and has spent a decade looking for new medicines.  She spent eight years at Pfizer at the Groton and Cambridge sites before joining us in California. She's currently a Director in the Discovery Chemistry department leading teams of scientists in pursuit of new [...]

or, How I Learned to Stop Worrying and Love My Own Definition. Recently I posted on “biologic drugs” which were approved in 2019 . All was well in my little scientific universe, until I received this in an email: “You recently reported "14 novel biologic drugs," referring to 'novel' biopharmaceuticals approved CDER. But, … You also include [...]

This article explains what LogD is, why LogD (or LogP) is important in drug discovery, rookie mistakes in drug discovery that come from overlooking LogD or LogP, and contains a LogD reference poster that shows the estimated amount of potency attributable to lipophilicity considerations alone. By Dennis Hu Jump to Cheat Sheet Lipophilicity is [...]