Preclinical disposition of MGS0274 besylate, a prodrug of a potent group II metabotropic glutamate receptor agonist MGS0008 for the treatment of schizophrenia

Discovery of TP0628103: A Highly Potent and Selective MMP-7 Inhibitor with Reduced OATP-Mediated Clearance Designed by Shifting Isoelectric Points

Matrix metalloproteinase-7 (MMP-7) has been shown to play an important role in pathophysiological processes such as cancer and fibrosis. We previously discovered selective MMP-7 inhibitors by molecular hybridization and structure-based drug design. However, the systemic clearance (CLtot) of the biologically active lead compound was very high. Because our studies revealed that hepatic uptake by organic anion transporting polypeptide (OATP) was responsible for the high CLtot, we found a novel approach to reducing their uptake based on isoelectric point (IP) values as an indicator for substrate recognition by OATP1B1/1B3. Our "IP shift strategy" to adjust the IP values culminated in the discovery of TP0628103 (18), which is characterized by reduced in vitro OATP-mediated hepatic uptake and in vivo CLtot. Our in vitro-in vivo extrapolation of OATP-mediated clearance and the "IP shift strategy" provide crucial insights for a new medicinal chemistry approach to reducing the systemic clearance of OATP1B1/1B3 substrates.

Bottom-up physiologically based pharmacokinetic modeling for predicting the human pharmacokinetic profiles of the ester prodrug MGS0274 and its active metabolite MGS0008, a metabotropic glutamate 2/3 receptor agonist

1. For ester prodrugs that are used to improve the gastrointestinal absorption of highly hydrophilic, pharmacologically active substances, it is challenging to predict the human pharmacokinetics (PK) of the prodrugs and their parent compounds using only preclinical data.2. This research was aimed at constructing a PBPK model for predicting the human PK of the ester prodrug MGS0274 and its parent compound MGS0008 after a single oral administration of MGS0274 besylate.3. First, we identified carboxylesterase 1 (CES1) as the major enzyme involved in the hydrolysis of MGS0274. Second, we constructed a new compartment model to estimate the passive diffusion clearance (CL_pd) of MGS0008, a critical parameter for predicting the PK of highly hydrophilic compounds, based on in vivo monkey PK data. Finally, we constructed a permeability-limited liver PBPK model incorporating the CL_pd assumed to be the same in humans.4. We confirmed that our method reliably predicted the human PK and that the estimated CL_pd was comparable to that calculated retrospectively using the PBPK model, suggesting that the methodology for estimating the CL_pd was valid.5. Our proposed methodology is expected to be helpful for human PK prediction of ester prodrugs hydrolyzed by CES1 and their hydrophilic parent compounds even during the preclinical phase.

Nanotechnology Approaches for Enhanced CNS Drug Delivery in the Management of Schizophrenia

Schizophrenia is a neuropsychiatric disorder mainly affecting the central nervous system, presented with auditory and visual hallucinations, delusion and withdrawal from society. Abnormal dopamine levels mainly characterise the disease; various theories of neurotransmitters explain the pathophysiology of the disease. The current therapeutic approach deals with the systemic administration of drugs other than the enteral route, altering the neurotransmitter levels within the brain and providing symptomatic relief. Fluid biomarkers help in the early detection of the disease, which would improve the therapeutic efficacy. However, the major challenge faced in CNS drug delivery is the blood-brain barrier. Nanotherapeutic approaches may overcome these limitations, which will improve safety, efficacy, and targeted drug delivery. This review article addresses the main challenges faced in CNS drug delivery and the significance of current therapeutic strategies and nanotherapeutic approaches for a better understanding and enhanced drug delivery to the brain, which improve the quality of life of schizophrenia patients.

Regulation of Glutamatergic Activity via Bidirectional Activation of Two Select Receptors as a Novel Approach in Antipsychotic Drug Discovery

Schizophrenia is a mental disorder that affects approximately 1-2% of the population and develops in early adulthood. The disease is characterized by positive, negative, and cognitive symptoms. A large percentage of patients with schizophrenia have a treatment-resistant disease, and the risk of developing adverse effects is high. Many researchers have attempted to introduce new antipsychotic drugs to the clinic, but most of these treatments failed, and the diversity of schizophrenic symptoms is one of the causes of disappointing results. The present review summarizes the results of our latest papers, showing that the simultaneous activation of two receptors with sub-effective doses of their ligands induces similar effects as the highest dose of each compound alone. The treatments were focused on inhibiting the increased glutamate release responsible for schizophrenia arousal, without interacting with dopamine (D₂) receptors. Ligands activating metabotropic receptors for glutamate, GABA_B or muscarinic receptors were used, and the compounds were administered in several different combinations. Some combinations reversed all schizophrenia-related deficits in animal models, but others were active only in select models of schizophrenia symptoms (i.e., cognitive or negative symptoms).

Discovery of MGS0274, an ester prodrug of a metabotropic glutamate receptor 2/3 agonist with improved oral bioavailability

We previously reported that MGS0008 is a selective group II metabotropic glutamate receptor (mGlu2/3 receptor) agonist that is effective in animal models of schizophrenia. MGS0008 is a highly hydrophilic glutamate analog and is therefore expected to show low oral bioavailability in humans. To improve the oral bioavailability of MGS0008, ester prodrugs of MGS0008 were synthesized and their usefulness was evaluated. Among the prodrugs, the l-menthol-ester prodrug 4h demonstrated preferable lipophilicity, good chemical stability, and a high conversion rate to MGS0008 in human and monkey liver microsomes. A pharmacokinetic study in monkeys revealed that the oral bioavailability of MGS0008 after oral dosing of compound 4h was approximately 15-fold higher than that after oral dosing of MGS0008. Based on these findings, a diastereomer of compound 4h (compound 4j, or MGS0274), was selected as a candidate for clinical drug development, and its besylate is currently under development for the treatment of schizophrenia (Development code: TS-134).

Safety and pharmacokinetic profiles of MGS0274 besylate (TS-134), a novel metabotropic glutamate 2/3 receptor agonist prodrug, in healthy subjects

Aims

The safety and pharmacokinetics of single and multiple doses of a novel mGlu_2/3 receptor agonist prodrug, MGS0274 besylate (TS‐134), were investigated in healthy subjects.

Methods

Phase 1 single‐ascending dose (5–20 mg) and multiple‐ascending dose titration (5–80 mg) studies were conducted in healthy male and female subjects. Both studies were randomized, double‐blinded and placebo‐controlled. In one cohort of single‐ascending dose study (10 mg), concentrations of MGS0008, the active compound, in the cerebrospinal fluid (CSF) were measured for up to 24 hours postdose.

Results

Following single and multiple oral administrations, MGS0274 was rapidly absorbed and extensively converted into MGS0008, which reached a maximum concentration (C_max) in plasma within 4 hours postdose and declined with a terminal half‐life (t_1/2) of around 10 hours. Plasma exposure to MGS0274 was minimal, accounting for approximately 3% of the area under the concentration–time curve (AUC) of MGS0008. Plasma C_max and AUC of MGS0008 at steady state increased dose proportionally (5–80 mg). MGS0008 penetrated into CSF, with a CSF‐to‐plasma C_max ratio of 3.66%, and was eliminated with a t_1/2 of approximately 16 hours. The most frequent treatment‐emergent adverse events observed following single and multiple oral administration included headache, nausea, somnolence, dizziness and vomiting.

Conclusion

TS‐134 is orally bioavailable in humans and converts rapidly and extensively to MGS0008, which exhibits good CSF penetration. Orally administered TS‐134 was safe and generally well‐tolerated; hence, TS‐134 is a promising candidate for further clinical development for the treatment of disorders in which glutamatergic abnormalities are involved, such as schizophrenia.