Development of a multigram synthesis of the bradykinin receptor 2 agonist FR-190997 and analogs thereof.

Using Fujisawa's B2R agonist FR-190997, we recently demonstrated for the first time that agonism at the bradykinin receptor type 2 (B2R) produces substantial antiproliferative effects. FR-190997 elicited an EC50 of 80 nM in the triple-negative breast cancer cell line MDA-MB-231, a much superior performance to that exhibited by most approved breast cancer drugs. Consequently, we initiated a program aiming primarily at synthesizing adequate quantities of FR-190997 to support further in vitro and in vivo studies toward its repurposing for various cancers and, in parallel, enable the generation of novel FR-190997 analogs for an SAR study. Prerequisite for this endeavor was to address the synthetic challenges associated with the FR-190997 scaffold, which the Fujisawa chemists had constructed in 20 steps, 13 of which required chromatographic purification. We succeeded in developing a 17-step synthesis amenable to late-stage diversification that eliminated all chromatography and enabled access to multigram quantities of FR-190997 and novel derivatives thereof, supporting further anticancer research based on B2R agonists.

New Analogs of Polyamine Toxins from Spiders and Wasps: Liquid Phase Fragment Synthesis and Evaluation of Antiproliferative Activity.

Polyamine toxins (PATs) are conjugates of polyamines (PAs) with lipophilic carboxylic acids, which have been recently shown to present antiproliferative activity. Ten analogs of the spider PATs Agel 416, HO-416b, and JSTX-3 and the wasp PAT PhTX-433 were synthesized with changes in the lipophilic head group and/or the PA chain, and their antiproliferative activity was evaluated on MCF-7 and MDA-MB-231 breast cancer cells, using Agel 416 and HO-416b as reference compounds. All five analogs of PhTX-433 were of very low activity on both cell lines, whereas the two analogs of JSTX-3 were highly active only on the MCF-7 cell line with IC50 values of 2.63-2.81 µΜ. Of the remaining three Agel 416 or HO-416b analogs, only the one with the spermidine chain was highly active on both cells with IC50 values of 3.15-12.6 µM. The two most potent compounds in this series, Agel 416 and HO-416b, with IC50 values of 0.09-3.98 µΜ for both cell lines, were found to have a very weak cytotoxic effect on the MCF-12A normal breast cells. The present study points out that the structure of both the head group and the PA chain determine the strength of the antiproliferative activity of PATs and their selectivity towards different cells.

Studies towards the Synthesis of Novel 3-Aminopropoxy-Substituted Dioxins Suitable for the Development of Aptamers for Photonic Biosensor Applications.

Hydroxy-substituted tetrachlorodibenzo[b,e][1,4]dioxin and tetrachlorodibenzo[b,d]furans have been synthesized using 3,4-dichloroanisole, 2,3,6-trichlorophenol and 4,5-dichlorocatechol as starting materials and electrophilic and/or nucleophilic aromatic substitution reactions for the assembly of the dibenzo[b,e][1,4]dioxin and dibenzo[b,d]furan systems. The thus-obtained phenolic compounds were then alkylated with N-1-(4,4-dimethyl-2,6-dioxocyclohexylidene)ethyl (Dde)-protected 3-bromopropan-1-amine to give the corresponding N-Dde protected 3-aminopropoxy-substituted tetrachlorodibenzo[b,e][1,4]dioxin and tetrachlorodibenzo[b,d]furans, respectively. Hydrazinolysis-mediated Dde removal from the former compound provided the corresponding amino-substituted dioxin, which was coupled to carboxy-substituted magnetic beads affording magnetic beads coated by the amino-substituted dioxin. The latter is an attractive intermediate for the development of selective single-standard DNA (ssDNA) aptamers, which constitute molecular recognition elements in photonic biosensors with potential application to the monitoring of the dangerous environmental pollutants, dioxins having serious implications in human health.

Potent antiproliferative activity of bradykinin B2 receptor selective agonist FR-190997 and analogue structures thereof: A paradox resolved?

Βradykinin stimulation of B2 receptor is known to activate the oncogenic ERK pathway and overexpression of bradykinin receptors B1 and B2 has been reported to occur in glioma, colorectal and cervical cancers. B1R and B2R antagonists have been shown to reverse tumor proliferation and invasion. Paradoxically, B1R and B2R agonism has also been reported to elicit antiproliferative benefits. In order to complement the data accumulated to date with the natural substrate bradykinin and peptidic B2R antagonists, we decided to examine for the first time the response elicited by B2R stimulation in breast cancer lines with a non-peptidic small molecule B2R agonist. We synthesized and assessed the highly selective and potent B2R partial agonist FR-190997 in MCF-7 and MDA-MBA-231 breast cancer lines and found it possessed significant antiproliferative activity (IC50 2.14 and 0.08 µΜ, respectively). The modular nature of FR-190997 allowed us to conduct a focused SAR study and discover compound 10 which exhibits subnanomolar antiproliferative activity (IC 50 0.06 nΜ) in the TNBC MDA-MBA-231 cell line. This performance surpasses, in most cases by several orders of magnitude, those of established anticancer agents and FDA-approved breast cancer drugs. In line with the established literature we suggest that this remarkable activity precipitates from a dual mode of action involving agonist-induced receptor internalization/degradation combined with sequestration of functional intracellular B2 receptors and inhibition of the associated endosomal signaling. The latter mode may be realized by appropriate ligands regardless of B2R agonist/antagonist designation which only relates to membrane residing GCPRs. Under this prism the controversy over the antiproliferative effects of B2 agonists and antagonists is potentially neutralized.