Smart design of patient-centric long-acting products: from preclinical to marketed pipeline trends and opportunities.

INTRODUCTION: We see a development in the field of long-acting products to serve patients with chronic diseases by providing benefits in adherence, efficacy, and safety of the treatment. This review investigates features of long-acting products on the market/pipeline to understand which drug substance (DS) and drug product (DP) characteristics likely enable a successful patient-centric, low-dosing frequency product. AREAS COVERED: This review evaluates marketed/pipeline long-acting products with greater than 1 week release of small molecules and peptides by oral and injectable route of administration (RoA), with particular focus on patient centricity, adherence impact, health outcomes, market trends, and the match of DS/DP technologies which lead to market success. EXPERT OPINION: Emerging trends are expected to change the field of long-acting products in the upcoming years by increasing capability in engineered molecules (low solubility, long half-life, high potency, etc.), directly developing DP as long-acting oral/injectable, increasing the proportion of products for local drug delivery, and a direction toward more subcutaneous, self-administered products. Among long-acting injectable products, nanosuspensions show a superiority in dose per administration and dosing interval, overwhelming the field of infectious diseases with the recently marketed products.

Discovery of Umibecestat (CNP520): A Potent, Selective, and Efficacious ß-Secretase (BACE1) Inhibitor for the Prevention of Alzheimer's Disease.

After identification of lead compound 6, 5-amino-1,4-oxazine BACE1 inhibitors were optimized in order to improve potency, brain penetration, and metabolic stability. Insertion of a methyl and a trifluoromethyl group at the 6-position of the 5-amino-1,4-oxazine led to 8 (NB-360), an inhibitor with a pKa of 7.1, a very low P-glycoprotein efflux ratio, and excellent pharmacological profile, enabling high central nervous system penetration and exposure. Fur color changes observed with NB-360 in efficacy studies in preclinical animal models triggered further optimization of the series. Herein, we describe the steps leading to the discovery of 3-chloro-5-trifluoromethyl-pyridine-2-carboxylic acid [6-((3R,6R)-5-amino-3,6-dimethyl-6-trifluoromethyl-3,6-dihydro-2H-[1,4]oxazin-3-yl)-5-fluoro-pyridin-2-yl]amide 15 (CNP520, umibecestat), an inhibitor with superior BACE1/BACE2 selectivity and pharmacokinetics. CNP520 reduced significantly Aß levels in mice and rats in acute and chronic treatment regimens without any side effects and thus qualified for Alzheimer's disease prevention studies in the clinic.

Synthesis of the Potent, Selective, and Efficacious ß-Secretase (BACE1) Inhibitor NB-360.

Starting from lead compound 4, the 1,4-oxazine headgroup was optimized to improve potency and brain penetration. Focusing at the 6-position of the 5-amino-1,4-oxazine, the insertion of a Me and a CF3 group delivered an excellent pharmacological profile with a pKa of 7.1 and a very low P-gp efflux ratio enabling high central nervous system (CNS) penetration and exposure. Various synthetic routes to access BACE1 inhibitors bearing a 5-amino-6-methyl-6-(trifluoromethyl)-1,4-oxazine headgroup were investigated. Subsequent optimization of the P3 fragment provided the highly potent N-(3-((3R,6R)-5-amino-3,6-dimethyl-6-(trifluoromethyl)-3,6-dihydro-2H-1,4-oxazin-3-yl)-4-fluorophenyl)-5-cyano-3-methylpicolinamide 54 (NB-360), able to reduce significantly Aß levels in mice, rats, and dogs in acute and chronic treatment regimens.

Discovery of 1H-pyrazolo[3,4-b]pyridines as potent dual orexin receptor antagonists (DORAs).

Compound rac-1 was identified by high throughput screening. Here we report SAR studies and MedChem optimization towards the highly potent dual orexin receptor antagonists (S)-2 and (S)-3. Furthermore, strategies to overcome the suboptimal physicochemical properties are highlighted and the pharmacokinetic profiles of representative compounds is presented.

A novel BACE inhibitor NB-360 shows a superior pharmacological profile and robust reduction of amyloid-ß and neuroinflammation in APP transgenic mice.

BACKGROUND: Alzheimer's disease (AD) is the most common form of dementia, the number of affected individuals is rising, with significant impacts for healthcare systems. Current symptomatic treatments delay, but do not halt, disease progression. Genetic evidence points to aggregation and deposition of amyloid-ß (Aß) in the brain being causal for the neurodegeneration and dementia typical of AD. Approaches to target Aß via inhibition of γ-secretase or passive antibody therapy have not yet resulted in substantial clinical benefits. Inhibition of BACE1 (ß-secretase) has proven a challenging concept, but recent BACE1inhibitors can enter the brain sufficiently well to lower Aß. However, failures with the first clinical BACE1 inhibitors have highlighted the need to generate compounds with appropriate efficacy and safety profiles, since long treatment periods are expected to be necessary in humans. RESULTS: Treatment with NB-360, a potent and brain penetrable BACE-1 inhibitor can completely block the progression of Aß deposition in the brains of APP transgenic mice, a model for amyloid pathology. We furthermore show that almost complete reduction of Aß was achieved also in rats and in dogs, suggesting that these findings are translational across species and can be extrapolated to humans. Amyloid pathology may be an initial step in a complex pathological cascade; therefore we investigated the effect of BACE-1 inhibition on neuroinflammation, a prominent downstream feature of the disease. NB-360 stopped accumulation of activated inflammatory cells in the brains of APP transgenic mice. Upon chronic treatment of APP transgenic mice, patches of grey hairs appeared. CONCLUSIONS: In a rapidly developing field, the data on NB-360 broaden the chemical space and expand knowledge on the properties that are needed to make a BACE-1 inhibitor potent and safe enough for long-term use in patients. Due to its excellent brain penetration, reasonable oral doses of NB-360 were sufficient to completely block amyloid-ß deposition in an APP transgenic mouse model. Data across species suggest similar treatment effects can possibly be achieved in humans. The reduced neuroinflammation upon amyloid reduction by NB-360 treatment supports the notion that targeting amyloid-ß pathology can have beneficial downstream effects on the progression of Alzheimer's disease.

Blocking metabotropic glutamate receptor subtype 7 (mGlu7) via the Venus flytrap domain (VFTD) inhibits amygdala plasticity, stress, and anxiety-related behavior.

The metabotropic glutamate receptor subtype 7 (mGlu7) is an important presynaptic regulator of neurotransmission in the mammalian CNS. mGlu7 function has been linked to autism, drug abuse, anxiety, and depression. Despite this, it has been difficult to develop specific blockers of native mGlu7 signaling in relevant brain areas such as amygdala and limbic cortex. Here, we present the mGlu7-selective antagonist 7-hydroxy-3-(4-iodophenoxy)-4H-chromen-4-one (XAP044), which inhibits lateral amygdala long term potentiation (LTP) in brain slices from wild type mice with a half-maximal blockade at 88 nm. There was no effect of XAP044 on LTP of mGlu7-deficient mice, indicating that this pharmacological effect is mGlu7-dependent. Unexpectedly and in contrast to all previous mGlu7-selective drugs, XAP044 does not act via the seven-transmembrane region but rather via a binding pocket localized in mGlu7's extracellular Venus flytrap domain, a region generally known for orthosteric agonist binding. This was shown by chimeric receptor studies in recombinant cell line assays. XAP044 demonstrates good brain exposure and wide spectrum anti-stress and antidepressant- and anxiolytic-like efficacy in rodent behavioral paradigms. XAP044 reduces freezing during acquisition of Pavlovian fear and reduces innate anxiety, which is consistent with the phenotypes of mGlu7-deficient mice, the results of mGlu7 siRNA knockdown studies, and the inhibition of amygdala LTP by XAP044. Thus, we present an mGlu7 antagonist with a novel molecular mode of pharmacological action, providing significant application potential in psychiatry. Modeling the selective interaction between XAP044 and mGlu7's Venus flytrap domain, whose three-dimensional structure is already known, will facilitate future drug development supported by computer-assisted drug design.

Distinct effects of IPSU and suvorexant on mouse sleep architecture.

Dual orexin receptor (OXR) antagonists (DORAs) such as almorexant, SB-649868, suvorexant (MK-4305), and filorexant (MK-6096), have shown promise for the treatment of insomnias and sleep disorders. Whether antagonism of both OX1R and OX2R is necessary for sleep induction has been a matter of some debate. Experiments using knockout mice suggest that it may be sufficient to antagonize only OX2R. The recent identification of an orally bioavailable, brain penetrant OX2R preferring antagonist 2-((1H-Indol-3-yl)methyl)-9-(4-methoxypyrimidin-2-yl)-2,9-diazaspiro[5.5]undecan-1-one (IPSU) has allowed us to test whether selective antagonism of OX2R may also be a viable strategy for induction of sleep. We previously demonstrated that IPSU and suvorexant increase sleep when dosed during the mouse active phase (lights off); IPSU inducing sleep primarily by increasing NREM sleep, suvorexant primarily by increasing REM sleep. Here, our goal was to determine whether suvorexant and IPSU affect sleep architecture independently of overall sleep induction. We therefore tested suvorexant (25 mg/kg) and IPSU (50 mg/kg) in mice during the inactive phase (lights on) when sleep is naturally more prevalent and when orexin levels are normally low. Whereas IPSU was devoid of effects on the time spent in NREM or REM, suvorexant substantially disturbed the sleep architecture by selectively increasing REM during the first 4 h after dosing. At the doses tested, suvorexant significantly decreased wake only during the first hour and IPSU did not affect wake time. These data suggest that OX2R preferring antagonists may have a reduced tendency for perturbing NREM/REM architecture in comparison with DORAs. Whether this effect will prove to be a general feature of OX2R antagonists vs. DORAs remains to be seen.

Kinetic properties of "dual" orexin receptor antagonists at OX1R and OX2R orexin receptors.

Orexin receptor antagonists represent attractive targets for the development of drugs for the treatment of insomnia. Both efficacy and safety are crucial in clinical settings and thorough investigations of pharmacokinetics and pharmacodynamics can predict contributing factors such as duration of action and undesirable effects. To this end, we studied the interactions between various "dual" orexin receptor antagonists and the orexin receptors, OX1R and OX2R, over time using saturation and competition radioligand binding with [(3)H]-BBAC ((S)-N-([1,1'-biphenyl]-2-yl)-1-(2-((1-methyl-1H-benzo[d]imidazol-2-yl)thio)acetyl)pyrrolidine-2-carboxamide). In addition, the kinetics of these compounds were investigated in cells expressing human, mouse and rat OX1R and OX2R using FLIPR® assays for calcium accumulation. We demonstrate that almorexant reaches equilibrium very slowly at OX2R, whereas SB-649868, suvorexant, and filorexant may take hours to reach steady state at both orexin receptors. By contrast, compounds such as BBAC or the selective OX2R antagonist IPSU ((2-((1H-Indol-3-yl)methyl)-9-(4-methoxypyrimidin-2-yl)-2,9-diazaspiro[5.5]undecan-1-one) bind rapidly and reach equilibrium very quickly in binding and/or functional assays. Overall, the "dual" antagonists tested here tend to be rather unselective under non-equilibrium conditions and reach equilibrium very slowly. Once equilibrium is reached, each ligand demonstrates a selectivity profile that is however, distinct from the non-equilibrium condition. The slow kinetics of the "dual" antagonists tested suggest that in vitro receptor occupancy may be longer lasting than would be predicted. This raises questions as to whether pharmacokinetic studies measuring plasma or brain levels of these antagonists are accurate reflections of receptor occupancy in vivo.

Identification of a novel series of orexin receptor antagonists with a distinct effect on sleep architecture for the treatment of insomnia.

Dual orexin receptor (OXR) antagonists (DORAs) such as almorexant, 1 (SB-649868), or suvorexant have shown promise for the treatment of insomnias and sleep disorders in several recent clinical trials in volunteers and primary insomnia patients. The relative contribution of antagonism of OX1R and OX2R for sleep induction is still a matter of debate. We therefore initiated a drug discovery project with the aim of creating both OX2R selective antagonists and DORAs. Here we report that the OX2R selective antagonist 26 induced sleep in mice primarily by increasing NREM sleep, whereas the DORA suvorexant induced sleep largely by increasing REM sleep. Thus, OX2R selective antagonists may also be beneficial for the treatment of insomnia.

Discovery of 1H-pyrrolo[2,3-c]pyridine-7-carboxamides as novel, allosteric mGluR5 antagonists.

1H-pyrrolo[2,3-c]pyridine-7-carboxamides constitute a new series of allosteric mGluR5 antagonists. Variation of the substituents attached to the heterocyclic scaffold allowed to improve the physico-chemical parameters for optimization of the aqueous solubility while retaining high in vitro potency.

Kynurenine 3-monooxygenase inhibition in blood ameliorates neurodegeneration.

Metabolites in the kynurenine pathway, generated by tryptophan degradation, are thought to play an important role in neurodegenerative disorders, including Alzheimer's and Huntington's diseases. In these disorders, glutamate receptor-mediated excitotoxicity and free radical formation have been correlated with decreased levels of the neuroprotective metabolite kynurenic acid. Here, we describe the synthesis and characterization of JM6, a small-molecule prodrug inhibitor of kynurenine 3-monooxygenase (KMO). Chronic oral administration of JM6 inhibits KMO in the blood, increasing kynurenic acid levels and reducing extracellular glutamate in the brain. In a transgenic mouse model of Alzheimer's disease, JM6 prevents spatial memory deficits, anxiety-related behavior, and synaptic loss. JM6 also extends life span, prevents synaptic loss, and decreases microglial activation in a mouse model of Huntington's disease. These findings support a critical link between tryptophan metabolism in the blood and neurodegeneration, and they provide a foundation for treatment of neurodegenerative diseases.

Structure determination of neoefrapeptins A to N: peptides with insecticidal activity produced by the fungus Geotrichum candidum.

The structures of neoefrapeptins A to N, peptides with insecticidal activity, were elucidated. They showed a close similarity to efrapeptin. However, all neoefrapeptins contained the very rare amino acid 1-amino-cyclopropane-carboxylic acid and some of them also contained (2S,3S)-3-methylproline. The neoefrapeptins are the first case, in which these amino acids are found as building blocks for linear peptides. They were identified by comparison of the silylated hydrolyzate to reference material by GC/MS (EI-mode). The sequence was elucidated using mass spectrometry (ESI+ mode). Full scan spectra showed two fragments in high yield, even under mild ionization conditions. MS/MS spectra of these two fragments yielded fragment rich spectra from which the sequence of the compounds was determined almost completely. The proteolytic cleavage with the proteinase papain yielded products that allowed to prove the rest of the sequence and the identity of the C-terminus to efrapeptin. The proteolytic cleavage products allowed furthermore to determine the position of the isobaric amino acids, pipecolic acid and 3-methylproline in neoefrapeptin F, as well as the location of R-isovaline and S-isovaline. Papain digestion was such established as a tool for structure elucidation of peptides rich in alpha,alpha-dialkylated amino acids. CD spectra suggested a 3(10) helical structure for neoefrapeptins A and F.

Plant-plant signaling: application of trans- or cis-methyl jasmonate equivalent to sagebrush releases does not elicit direct defenses in native tobacco.

Nicotiana attenuata plants growing in close proximity to damaged sagebrush (Artemisia tridentata ssp. tridentata) suffer less herbivory than plants near undamaged sagebrush. Sagebrush constitutively releases methyl jasmonate (MeJA), a compound that when applied directly to N. attenuata, elicits herbivore resistance and the direct defense traits [protease inhibitors (PIs), nicotine]. Damage increases the release of volatile MeJA, primarily in the cis epimer, suggesting that cis-MeJA may mediate this apparent interplant signaling. We characterized sagebrush's MeJA plume before and after damage in nature and in the laboratory, and compared the activity of trans- and cis-MeJA in inducing PIs, nicotine, and Manduca sexta resistance in N. attenuata. We used both lanolin applications and aqueous sprays that mimic natural exposures, and we determined the amount of volatilized MeJA required to elicit a nicotine response in open-grown plants. Wounding rapidly and transiently increased cis-MeJA emissions from damaged parts (but not systemically), and the released plume did not rapidly dissipate in nature. cis-MeJA was not consistently more active than trans-MeJA, and the order of exposure (trans- then cis-) did not influence activity. We conclude that volatile MeJA, either trans- or cis-, when applied at levels consistent with those released by sagebrush does not elicit direct defenses in N. attenuata.