Amine promiscuity and toxicology analysis

Peptide delivery of a multivalent mRNA SARS-CoV-2 vaccine

Lipid nanoparticles (LNP) have been instrumental in the success of mRNA vaccines and have opened up the field to a new wave of therapeutics. However, what is ahead beyond the LNP? The approach herein used a nanoparticle containing a blend of Spike, Membrane and Envelope antigens complexed for the first time with the RALA peptide (RALA-SME). The physicochemical characteristics and functionality of RALA-SME were assessed. With >99% encapsulation, RALA-SME was administered via intradermal injection in vivo, and all three antigen-specific IgG antibodies were highly significant. The IgG2a:IgG1 ratio were all >1.2, indicating a robust TH1 response, and this was further confirmed with the T-Cell response in mice. A complete safety panel of markers from mice were all within normal range, supported by safety data in hamsters. Vaccination of Syrian Golden hamsters with RALA-SME derivatives produced functional antibodies capable of neutralising SARS-CoV-2 from both Wuhan-Hu-1 and Omicron BA.1 lineages after two doses. Antibody levels increased over the study period and provided protection from disease-specific weight loss, with inhibition of viral migration down the respiratory tract. This peptide technology enables the flexibility to interchange and add antigens as required, which is essential for the next generation of adaptable mRNA vaccines.

Off target toxicities and links with physicochemical properties of medicinal products, including antibiotics, oligonucleotides, lipid nanoparticles (with cationic and/or anionic charges). Data review suggests an emerging pattern

Toxicology is an essential part of any drug development plan. Circumnavigating the risk of failure because of a toxicity issue can be a challenge, and failure in late development is extremely costly. To identify potential risks, it requires more than just understanding the biological target. The toxicologist needs to consider a compound's structure, it's physicochemical properties (including the impact of the overall formulation), as well as the biological target (e.g., receptor interactions). Understanding the impact of the physicochemical properties can be used to predict potential toxicities in advance by incorporating key endpoints in early screening strategies and/or used to compare toxicity profiles across lead candidates. This review discussed the risks of off-target and/or non-specific toxicities that may be associated with the physicochemical properties of compounds, especially those carrying dominant positive or negative charges, including amphiphilic small molecules, peptides, oligonucleotides and lipids/liposomes/lipid nanoparticles. The latter of which are being seen more and more in drug development, including the recent Covid pandemic, where mRNA and lipid nanoparticle technology is playing more of a role in vaccine development. The translation between non-clinical and clinical data is also considered, questioning how a physicochemical driven toxicity may be more universal across species, which means that such toxicity may be reassuringly translatable between species and as such, this information may also be considered as a support to the 3 R's, particularly in the early screening stages of a drug development plan.

Discovery of 4-(3-aminopyrrolidinyl)-3-aryl-5-(benzimidazol-2-yl)-pyridines as potent and selective SST5 agonists for the treatment of congenital hyperinsulinism

SST5 receptor activation potently inhibits insulin secretion from pancreatic β-cells, and an orally available nonpeptide selective SST5 agonist may be used to effectively manage the blood glucose levels of congenital HI patients to avoid severe hypoglycemia. Our medicinal chemistry efforts have led to the discovery of 4-(3-aminopyrrolidinyl)-3-aryl-5-(benzimidazol-2-yl)-pyridine analogs as potent SST5 agonists. This class of molecules exhibits excellent human SST5 potency and selectivity against SST1, SST2, SST3 and SST4 receptors. Leading compound 3-{4-[(3S)-3-aminopyrrolidin-1-yl]-5-(4-methyl-1H-1,3-benzodiazol-2-yl)pyridin-3-yl-5-fluorobenzonitrile (28, CRN02481) showed limited off-target activity and good pharmacokinetic profiles in both male Sprague Dawley rats and Beagle dogs to advance into further preclinical evaluations.

Utility of Physicochemical Properties for the Prediction of Toxicological Outcomes: Takeda Perspective

The role that physicochemical properties play toward increasing the likelihood of toxicity findings in in vivo studies has been well reported, albeit sometimes with different conclusions. We decided to understand the role that physicochemical properties play toward the prediction of in vivo toxicological outcomes for Takeda chemistry using 284 internal compounds. In support of the previously reported "3/75 rule", reducing lipophilicity of molecules decreases toxicity odds noticeably; however, we also found that the trend of toxicity odds is different between compounds classified by their ionization state. For basic molecules, the odds of in vivo toxicity outcomes were significantly impacted by both lipophilicity and polar surface area, whereas neutral molecules were impacted less so. Through an analysis of several project-related compounds, we herein demonstrate that the utilization of the 3/75 rule coupled with consideration of ionization state is a rational strategy for medicinal chemistry design of safer drugs.

Promiscuity of in Vitro Secondary Pharmacology Assays and Implications for Lead Optimization Strategies

We conducted an analysis on screening data generated from 1445 compounds against a panel of 130 enzymes, ion channels, and receptors to assess secondary pharmacological risks. Hit rates of these targets as well as physicochemical properties for those hits were evaluated. A majority of targets yielded hits with higher clogP, molecular weight, and more basic character than inactive compounds. Although most targets favored lipophilic hits, the average clogP of hits at a given target did not correlate with its hit rate. Furthermore, a matched pair analysis was completed to determine structural changes that impacted off-target activities. A correlation of binding assays used in this analysis illustrated that some pharmacologically related binding assays are highly correlative and may be substituted for a smaller set of surrogate assays.

Small-Scale Panel Comprising Diverse Gene Family Targets To Evaluate Compound Promiscuity

Despite the recent advances in the life sciences and the remarkable investment in drug discovery research, the success rate of small-molecule drug development remains low. Safety is the second most influential factor of drug attrition in clinical studies; thus, the selection of compounds with fewer toxicity concerns is crucial to increase the success rate of drug discovery. Compounds that promiscuously bind to multiple targets are likely to cause unexpected pharmacological activity that may lead to adverse effects. Therefore, avoiding such compounds during early research stages would contribute to identifying compounds with a higher chance of success in the clinic. To evaluate the interaction profile against a wide variety of targets, we constructed a small-scale promiscuity panel (PP) consisting of eight targets (ROCK1, PDE4D2, GR, PPARγ, 5-HT_2B, adenosine A₃, M1, and GABA_A) that were selected from diverse gene families. The validity of this panel was confirmed by comparison with the promiscuity index evaluated from larger-scale panels. Analysis of data from the PP revealed that both lipophilicity and basicity are likely to increase promiscuity, while the molecular weight does not significantly contribute. Additionally, the promiscuity assessed using our PP correlated with the occurrence of both in vitro cytotoxicity and in vivo toxicity, suggesting that the PP is useful to identify compounds with fewer toxicity concerns. In summary, this small-scale and cost-effective PP can contribute to the identification of safer compounds that would lead to a reduction in drug attrition due to safety issues.

Pharmacological property optimization for allosteric ligands: A medicinal chemistry perspective

New strategies to potentially improve drug safety and efficacy emerge with allosteric programs. Biased allosteric modulators can be designed with high subtype selectivity and defined receptor signaling endpoints, however, selecting the most meaningful parameters for optimization can be perplexing. Historically, "potency hunting" at the expense of physicochemical and pharmacokinetic optimization has led to numerous tool compounds with excellent pharmacological properties but no path to drug development. Conversely, extensive physicochemical and pharmacokinetic screening with only post hoc bias and allosteric characterization has led to inefficacious compounds or compounds with on-target toxicities. This field is rapidly evolving with new mechanistic understanding, changes in terminology, and novel opportunities. The intent of this digest is to summarize current understanding and debates within the field. We aim to discuss, from a medicinal chemistry perspective, the parameter choices available to drive SAR.