Gianfranco Battistuzzi

Non-natural macrocyclic inhibitors of histone deacetylases: design, synthesis, and activity.

Nonpeptidic chiral macrocycles were designed on the basis of an analogue of suberoylanilide hydroxamic acid (2) (SAHA, vorinostat) and evaluated against 11 histone deacetylase (HDAC) isoforms. The identification of critical amino acid residues highly conserved in the cap region of HDACs guided the design of the suberoyl-based macrocycles, which were expected to bear a maximum common substructure required to target the whole HDAC panel. A nanomolar HDAC inhibitory profile was observed for several compounds, which was comparable, if not superior, to that of 2. A promising cytotoxic activity was found for selected macrocycles against lung and colon cancer cell lines. Further elaboration of selected candidates led to compounds with an improved selectivity against HDAC6 over the other isozymes. Pair-fitting analysis was used to compare one of the best candidates with the natural tetrapeptide apicidin, in an effort to define a general pharmacophore that might be useful in the design of surrogates of peptidic macrocycles as potent and isoform-selective inhibitors.

Exploring bis-(indolyl)methane moiety as an alternative and innovative CAP group in the design of histone deacetylase (HDAC) inhibitors

In order to gather further knowledge about the structural requirements on histone deacetylase inhibitors (HDACi), starting from the schematic model of the common pharmacophore that characterizes this class of molecules (surface recognition CAP group-connection unit-linker region-Zinc Binding Group), we designed and synthesized a series of hydroxamic acids containing a bis-(indolyl)methane moiety. HDAC inhibition profile and antiproliferative activity were evaluated.

N-Hydroxy-(4-oxime)-cinnamide: A versatile scaffold for the synthesis of novel histone deacetilase (HDAC) inhibitors

With the aim to discover novel HDAC inhibitors with high potency and good safety profiles, we have designed a small library based on a N-hydroxy-(4-oxime)-cinnamide scaffold. We describe the synthesis of these novel compounds and some preliminary in vitro cytotoxic activity on three tumor cell lines, NB4, H460 and HCT116, as well as their inhibitory activity against class I, II and IV HDAC. Several 4-oxime derivatives demonstrated a promising inhibitory activity on HDAC6 and HDAC8 coupled to a good selectivity profile.

ST7612AA1, a thioacetate-ω(γ-lactam carboxamide) derivative selected from a novel generation of oral HDAC inhibitors.

A systematic study of medicinal chemistry aimed at identifying a new generation of HDAC inhibitors, through the introduction of a thiol zinc-binding group (ZBG) and of an amide-lactam in the ω-position of the polyethylene chain of the vorinostat scaffold, allowed the selection of a new class of potent pan-HDAC inhibitors (pan-HDACis). Simple, highly versatile, and efficient synthetic approaches were used to synthesize a library of these new derivatives, which were then submitted to a screening for HDAC inhibition as well as to a preliminary in vitro assessment of their antiproliferative activity. Molecular docking into HDAC crystal structures suggested a binding mode for these thiol derivatives consistent with the stereoselectivity observed upon insertion of amide-lactam substituents in the ω-position. ST7612AA1 (117), selected as a drug candidate for further development, showed an in vitro activity in the nanomolar range associated with a remarkable in vivo antitumor activity, highly competitive with the most potent HDAC inhibitors, currently under clinical trials. A preliminary study of PK and metabolism is also illustrated.

Hydroxamic acid based histone deacetylase inhibitors with confirmed activity against the malaria parasite

Recent studies have highlighted a key role in regulating gene transcription, in both eukaryotes and prokaryotes, by enzymes that control the acetylation and deacetylation of histones. In particular, inhibitors of histone deacetylases (HDAC-Is) have been shown effective in controlling the development of many parasites, such as the plasmodium of malaria. Here we report the results of a study aimed at evaluating antiparasitic effect of two classes of HDAC-Is bearing different zinc binding group (hydroxamic acid vs thiol). The study showed that only the hydroxamic acid based HDAC inhibitors were active, with Plasmodium falciparum being the most sensitive parasite, having from low double-digit to single-digit nanomolar range in vitro activities. Among three derivatives evaluated also in vivo, ST8086AA1 (8) effectively inhibited 88% of the development of Plasmodium falciparum.

Novel PARP-1 inhibitors based on a 2-propanoyl-3H-quinazolin-4-one scaffold.

Poly(ADP-ribose)polymerase-I (PARP-1) enzyme is involved in maintaining DNA integrity and programmed cell death. A virtual screening of commercial libraries led to the identification of five novel scaffolds with inhibitory profile in the low nanomolar range. A hit-to-lead optimization led to the identification of a group of new potent PARP-1 inhibitors, acyl-piperazinylamides of 3-(4-oxo-3,4-dihydro-quinazolin-2-yl)-propionic acid. Molecular modeling studies highlighted the preponderant role of the propanoyl side chain.

Lactam based 7-amino suberoylamide hydroxamic acids as potent HDAC inhibitors

A series of SAHA-like molecules were prepared introducing different lactam-carboxyamides in position 7 of the suberoylanilide skeleton. The activity against different HDAC isoforms was tested and the data compared with the corresponding linear products, without substituent in position 7. In general, this modification provided an effective reinforcement of in vitro activity. While the lactam size or the CO/NH group orientation did not strongly influence the inhibition, the contemporary modification of the suberoylamide fragment gave vary active variants in the lactam series, with compound 28 (ST8078AA1) that showed IC50 values between 2 and 10nM against all Class I HDAC isoforms, demonstrating it to be a large spectrum pan-inhibitor. This strong affinity with HDAC was also confirmed by the value of IC50=0.5μM against H460 cells, ranking 28 as one of the most potent HDAC inhibitors described so far.

E-ring-modified 7-oxyiminomethyl camptothecins: Synthesis and preliminary in vitro and in vivo biological evaluation

In contrast to five-membered E-ring analogues, 7-oxyiminomethyl derivatives of homocamptothecins showed ability to form stable ternary complexes with DNA and topoisomerase I. The 7-oxyiminomethyl derivatives of homocamptothecins were evaluated as a racemic mixture. Following the isolation of the two enantiomers, the 20 (R)-hydroxy isomer confirms the best activity. By using a panel of human tumor cells, all tested homocamptothecins showed a potent antiproliferative activity, correlating to the persistence of the cleavable complex. No significant difference was observed between the natural scaffold and the corresponding homocamptothecin homologue. A selected compound of this series exhibited an excellent antitumor activity against human gastrointestinal tumor xenografts.

4,5,6,7-Tetrahydro-isoxazolo-(4,5-c)-pyridines as a new class of cytotoxic Hsp90 inhibitors

Hsp90 is considered an interesting therapeutic target for anticancer drug development. Here we describe a new class of 4,5,6,7-tetrahydro-isoxazolo-[4,5-c]-pyridine compounds. A small library of derivatives has been synthesized and investigated. Some reported compounds show interesting properties combining both notable binding to Hsp90 and potent cell growth inhibitory activity. N-5 substitution with a 2,4 resorcinol carboxamide appears crucial for activity. Moreover, a derivative bearing a hydroxamic acid residue bound to C-3 amide portion was found to inhibit both Hsp90 and HDAC6.

New retinoid derivatives as back-ups of Adarotene

Adarotene belongs to the so-called class of atypical retinoids. The presence of the phenolic hydroxyl group on Adarotene structure allows a rapid O-glucuronidation as a major mechanism of elimination of the drug, favoring a fast excretion of its glucuronide metabolite in the urines. A series of ether, carbamate and ester derivatives was synthesized. All of them were studied and evaluated for their stability at different pH. The cytotoxic activity in vitro on NCI-H460 non-small cell lung carcinoma and A2780 ovarian tumor cell lines was also tested. A potential back-up of Adarotene has been selected to be evaluated in tumor models.