Hit evaluation of an α-helical peptide: Ala-scan, truncation and sidechain-to-sidechain macrocyclization of an RNA polymerase Inhibitor.

RNA polymerase (RNAP) remains a relatively underexplored target with only rifampicin and fidaxomicin in clinical use. Hence, the concurrent rise in bacterial resistance rate urges the search for novel RNAP inhibitors with a novel mode of action. In this work, we investigated the impact of several systematic modifications including sidechain-to-sidechain macrocylization in the α-helical content and biological activity of a previously identified inhibitory sigma factor fragment. Ala-scan results, peptide truncation from both the N- and C-terminus and modifications inspired by other RNAP inhibitors revealed novel structure activity relationships but did not yield a superior sequence. Additionally, four insertion points for non-natural amino acids bearing side chains required for macrocylization were explored. Linear precursors showed improved stabilization of the α-helical content compared to the original sequence as demonstrated by circular dichroism (CD) spectroscopy. However, this increase in α-helicity did not translate into improved biological activity. Instead, complete abolishment of RNAP inhibitory activity occurred. We hypothesize three possible reasons for such a discrepancy and offer the basis for further optimization efforts for this peptidic RNAP inhibitor.

Synthesis and Optimization of New 3,6-Disubstitutedindole Derivatives and Their Evaluation as Anticancer Agents Targeting the MDM2/MDMx Complex.

Twelve derivatives of the general formula 3-substituted-6-chloroindoles were synthesized and tested for their growth inhibitory effects versus p53(+/+) colorectal cancer HCT116 and its p53 knockout isogenic cells; colorectal cancer cell p53(-/-) SW480; the lung cancer cell line p53(-/-) H1299; mouse embryonic fibroblasts (MEF) p53(+/+) and its p53 knockout isogenic cells. The compounds were also evaluated for their ability to induce p53 nuclear translocation and binding to murine double minute 2 (MDM2) and murine double minute 4 (MDM4). Of these, compound 5a was the most active in inhibiting the growth of cells, with selectivity towards the p53(+/+) cell lines, and it showed stronger binding to MDM4 rather than MDM2. The activity profile of compound 5a is strongly similar to that of Nutlin-3.

Synthesis and biological evaluation of 16E-arylidenosteroids as cytotoxic and anti-aromatase agents.

Taking into consideration the structural requirements for cytotoxicity and aromatase inhibition, several new 16E-arylidenosteroidal derivatives have been prepared and evaluated for their cytotoxic and aromatase inhibitory activity. The new steroidal analogues 3, 5-8 and 11 exhibited significant cytotoxic effects when screened against three cancer cell lines, MCF-7 (breast), NCl-H460 (lung) and SF-268 central nervous system (CNS) at 100 µM and sensible cytotoxic effects subsequently in sixty cancer cell lines derived from nine cancers types (leukemia, lung, colon, CNS, melanoma, ovarian, renal, prostate and breast cancers). The imidazolyl substituted steroidal derivatives 5 and 7 exhibited strong inhibition of the aromatase enzyme with 16-[4-{3-(imidazol-1-yl)propoxy}-3-methoxybenzylidene]-5-androstene-3ß,17ß-diol (7) displaying 13 times more potency in comparison to aminoglutethimide.

A New PqsR Inverse Agonist Potentiates Tobramycin Efficacy to Eradicate Pseudomonas aeruginosa Biofilms.

Pseudomonas aeruginosa (PA) infections can be notoriously difficult to treat and are often accompanied by the development of antimicrobial resistance (AMR). Quorum sensing inhibitors (QSI) acting on PqsR (MvfR) - a crucial transcriptional regulator serving major functions in PA virulence - can enhance antibiotic efficacy and eventually prevent the AMR. An integrated drug discovery campaign including design, medicinal chemistry-driven hit-to-lead optimization and in-depth biological profiling of a new QSI generation is reported. The QSI possess excellent activity in inhibiting pyocyanin production and PqsR reporter-gene with IC50 values as low as 200 and 11 × 10-9 m, respectively. Drug metabolism and pharmacokinetics (DMPK) as well as safety pharmacology studies especially highlight the promising translational properties of the lead QSI for pulmonary applications. Moreover, target engagement of the lead QSI is shown in a PA mucoid lung infection mouse model. Beyond that, a significant synergistic effect of a QSI-tobramycin (Tob) combination against PA biofilms using a tailor-made squalene-derived nanoparticle (NP) formulation, which enhance the minimum biofilm eradicating concentration (MBEC) of Tob more than 32-fold is demonstrated. The novel lead QSI and the accompanying NP formulation highlight the potential of adjunctive pathoblocker-mediated therapy against PA infections opening up avenues for preclinical development.