Discovery of 4-aminopyrimidine analogs as highly potent dual P70S6K/Akt inhibitors.

Activation of the PI3K/Akt/mTOR kinase pathway is associated with human cancers. A dual p70S6K/Akt inhibitor is sufficient to inhibit strong tumor growth and to block negative impact of the compensatory Akt feedback loop activation. A scaffold docking strategy based on an existing quinazoline carboxamide series identified 4-aminopyrimidine analog 6, which showed a single-digit nanomolar and a micromolar potencies in p70S6K and Akt enzymatic assays. SAR optimization improved Akt enzymatic and p70S6K cellular potencies, reduced hERG liability, and ultimately discovered the promising candidate 37, which exhibited with a single digit nanomolar value in both p70S6K and Akt biochemical assays, and hERG activities (IC50 = 17.4 µM). This agent demonstrated dose-dependent efficacy in inhibiting mice breast cancer tumor growth and covered more than 90% pS6 inhibition up to 24 h at a dose of 200 mg/kg po.

Discovery of Evobrutinib: An Oral, Potent, and Highly Selective, Covalent Bruton's Tyrosine Kinase (BTK) Inhibitor for the Treatment of Immunological Diseases.

Bruton's tyrosine kinase (BTK) inhibitors such as ibrutinib hold a prominent role in the treatment of B cell malignancies. However, further refinement is needed to this class of agents, particularly in terms of adverse events (potentially driven by kinase promiscuity), which preclude their evaluation in nononcology indications. Here, we report the discovery and preclinical characterization of evobrutinib, a potent, obligate covalent inhibitor with high kinase selectivity. Evobrutinib displayed sufficient preclinical pharmacokinetic and pharmacodynamic characteristics which allowed for in vivo evaluation in efficacy models. Moreover, the high selectivity of evobrutinib for BTK over epidermal growth factor receptor and other Tec family kinases suggested a low potential for off-target related adverse effects. Clinical investigation of evobrutinib is ongoing in several autoimmune diseases, including multiple sclerosis, rheumatoid arthritis, and systemic lupus erythematosus.

Small Molecules Drive Big Improvements in Immuno-Oncology Therapies.

Immuno-oncology therapies have the potential to revolutionize the armamentarium of available cancer treatments. To further improve clinical response rates, researchers are looking for novel combination regimens, with checkpoint blockade being used as a backbone of the treatment. This Review highlights the significance of small molecules in this approach, which holds promise to provide increased benefit to cancer patients.

Recent progress towards clinically relevant ATP-competitive Akt inhibitors.

The frequency of PI3K/Akt/mTOR (PAM) Pathway mutations in human cancers sparked interest to determine if the pathway is druggable. The modest clinical benefit observed with mTOR rapalogs (temsirolimus and everolimus) provided further motivation to identify additional nodes of pathway inhibition that lead to improved clinical benefit. Akt is a central signaling node of the PAM pathway and could be an ideal target for improved pathway inhibition. Furthermore, inhibitors of Akt may be especially beneficial in tumors with Akt1 mutations. Recently, multiple ATP-competitive Akt inhibitors have been identified and are currently in clinical development. This review details the medicinal chemistry efforts towards identification of these molecules, highlights relevant preclinical data supporting clinical evaluation, and summarizes current clinical development plans.

M2698 is a potent dual-inhibitor of p70S6K and Akt that affects tumor growth in mouse models of cancer and crosses the blood-brain barrier.

Dysregulated PI3K/Akt/mTOR (PAM) pathway signaling occurs in ~30% of human cancers, making it a rational target for new therapies; however, the effectiveness of some PAM pathway inhibitors, such as mTORC rapalogs, may be compromised by a compensatory feedback loop leading to Akt activation. In this study, the p70S6K/Akt dual inhibitor, M2698 (previously MSC2363318A), was characterized as a potential anti-cancer agent through examination of its pharmacokinetic, pharmacodynamic and metabolic properties, and anti-tumor activity. M2698 was highly potent in vitro (IC50 1 nM for p70S6K, Akt1 and Akt3 inhibition; IC50 17 nM for pGSK3ß indirect inhibition) and in vivo (IC50 15 nM for pS6 indirect inhibition), and relatively selective (only 6/264 kinases had an IC50 within 10-fold of p70S6K). Orally administered M2698 crossed the blood-brain barrier in rats and mice, with brain tumor exposure 4-fold higher than non-disease brain. Dose-dependent inhibition of target substrate phosphorylation was observed in vitro and in vivo, indicating that M2698 blocked p70S6K to provide potent PAM pathway inhibition while simultaneously targeting Akt to overcome the compensatory feedback loop. M2698 demonstrated dose-dependent tumor growth inhibition in mouse xenograft models derived from PAM pathway-dysregulated human triple-negative (MDA-MB-468) and Her2-expressing breast cancer cell lines (MDA-MB-453 and JIMT-1), and reduced brain tumor burden and prolonged survival in mice with orthotopically implanted U251 glioblastoma. These findings highlight M2698 as a promising PAM pathway inhibitor whose unique mechanism of action and capacity to pass the blood-brain barrier warrant clinical investigation in cancers with PAM pathway dysregulation, and those with central nervous system involvement.

Design of non-cysteine-containing antimicrobial beta-hairpins: structure-activity relationship studies with linear protegrin-1 analogues.

Protegrins are short, cationic peptides that display potent, broad-spectrum antimicrobial activity. PG-1, the first of the five natural analogues discovered, forms a rigid antiparallel two-stranded beta-sheet that is stabilized by two disulfide bonds. The two strands of the sheet are linked by a short two-residue loop segment. Removal of the disulfide bridges (e.g., in Cys --> Ala analogues) is known to cause marked loss of antimicrobial activity. We have used basic principles of beta-hairpin design to develop linear analogues of PG-1 that lack cysteine but nevertheless display PG-1-like activity. Our most potent reengineered molecules contain three essential design features: (i) the four cysteine residues of PG-1 are replaced by residues that have high propensity for beta-strand conformation, (ii) D-proline is placed at the i + 1 position of the reverse turn to promote a type II' beta-turn, and (iii) amino functionality is incorporated at the gamma-carbon of the D-proline residue to mimic the charge distribution of the natural beta-hairpin. Structural studies revealed that the antimicrobial potency of the non-disulfide-bonded peptides can be correlated to the stability of the beta-hairpin conformations they adopt in aqueous solution. The presence of 150 mM NaCl was found to have little effect on the antimicrobial activity of PG-1, but one of our linear analogues loses some potency under these high salt conditions. Despite this discrepancy in salt sensitivity, NMR and CD data indicate that neither PG-1 nor our linear analogue experiences a significant decrease in beta-hairpin conformational stability in the presence of 150 mM NaCl. Thus, salt inactivation is not due to destabilization of the beta-hairpin conformation. Furthermore, our results show that beta-sheet design principles can be used to replace conformation-stabilizing disulfide bridges with noncovalent conformation-stabilizing features.