Andrew Griffin

Strategies to improve in vivo toxicology outcomes for basic candidate drug molecules

A valid PLS-DA model to predict attrition in pre-clinical toxicology for basic oral candidate drugs was built. A combination of aromatic/aliphatic balance, flatness, charge distribution and size descriptors helped predict the successful progression of compounds through a wide range of toxicity testing. Eighty percent of an independent test set of marketed post-2000 basic drugs could be successfully classified using the model, indicating useful forward predictivity. The themes within this work provide additional guidance for medicinal design chemists and complement other literature property guidelines.

Discovery of spirofused piperazine and diazepane amides as selective histamine-3 antagonists with in vivo efficacy in a mouse model of cognition.

A new series of potent and selective histamine-3 receptor (H3R) antagonists was identified on the basis of an azaspiro[2.5]octane carboxamide scaffold. Many scaffold modifications were largely tolerated, resulting in nanomolar-potent compounds in the H3R functional assay. Exemplar compound 6s demonstrated a selective profile against a panel of 144 secondary pharmacological receptors, with activity at only σ2 (62% at 10 μM). Compound 6s demonstrated free-plasma exposures above the IC50 (∼50×) with a brain-to-plasma ratio of ∼3 following intravenous dosing in mice. At three doses tested in the mouse novel object recognition model (1, 3, and 10 mg/kg s.c.), 6s demonstrated a statistically significant response compared with the control group. This series represents a new scaffold of H3 receptor antagonists that demonstrates in vivo exposure and efficacy in an animal model of cognition.

N,N-Diethyl-4-[(3-hydroxyphenyl)(piperidin-4-yl)amino] benzamide derivatives: The development of diaryl amino piperidines as potent δ opioid receptor agonists with in vivo anti-nociceptive activity in rodent models

We have investigated a series of phenolic diaryl amino piperidine delta opioid receptor agonists, establishing the importance of the phenol functional group and substitution on the piperdine nitrogen for delta agonist activity and selectivity versus the mu and kappa opioid receptors. This study uncovered compounds with improved agonist potency and selectivity compared to the standard, non-peptidic delta agonist SNC-80. In vivo anti-nociceptive activity of analog 8e in two rodent models is discussed, demonstrating the potential of delta agonists to provide a novel mechanism for pain relief.

Novel Methodology to Identify TRPV1 Antagonists Independent of Capsaicin Activation

TRPV1 was originally characterized as an integrator of various noxious stimuli such as capsaicin, heat, and protons. TRPV1-null mice exhibit a deficiency in sensing noxious heat stimuli, suggesting that TRPV1 is one of the main heat sensors on nociceptive primary afferent neurons and a candidate target for heat hypersensitivity in chronic pain. Several different potent and selective TRPV1 antagonists have been developed by more than 50 companies since the characterization of the receptor in 1997. A consequence of this competitive interest is the crowding of patentable chemical space, because very similar in vitro screening assays are used. To circumvent this issue and to expand our understanding of TRPV1 biology, we sought to take advantage of recent advancements in automated patch-clamp technology to design a novel screening cascade. This SAR-driving assay identified novel modulators that blocked the depolarization-induced activation of outwardly-rectifying TRPV1 currents independent of agonist stimulation, and we correlated the pharmacology to three other innovative assays for higher-throughput screening. Ultimately, we have identified a screening paradigm that would have good predictive value for future TRPV1 drug discovery projects and novel chemical space with a higher probability of gaining intellectual property coverage.

Potent and orally efficacious benzothiazole amides as TRPV1 antagonists.

Benzothiazole amides were identified as TRPV1 antagonists from high throughput screening using recombinant human TRPV1 receptor and structure-activity relationships were explored to pinpoint key pharmacophore interactions. By increasing aqueous solubility, through the attachment of polar groups to the benzothiazole core, and enhancing metabolic stability, by blocking metabolic sites, the drug-like properties and pharmokinetic profiles of benzothiazole compounds were sufficiently optimized such that their therapeutic potential could be verified in rat pharmacological models of pain.

Delta agonist hydroxy bioisosteres: the discovery of 3-((1-benzylpiperidin-4-yl){4-[(diethylamino)carbonyl]phenyl}amino)benzamide with improved delta agonist activity and in vitro metabolic stability.

We have investigated phenol replacements in a series of diaryl amino piperidine delta opioid agonists. From this study we have demonstrated that the hydroxy functional group can be replaced with a primary amide group, giving enhanced activity at the delta receptor, increased selectivity versus mu and kappa as well as improved in vitro metabolic stability.