Anchor extension: a structure-guided approach to design cyclic peptides targeting enzyme active sites.

Despite recent success in computational design of structured cyclic peptides, de novo design of cyclic peptides that bind to any protein functional site remains difficult. To address this challenge, we develop a computational "anchor extension" methodology for targeting protein interfaces by extending a peptide chain around a non-canonical amino acid residue anchor. To test our approach using a well characterized model system, we design cyclic peptides that inhibit histone deacetylases 2 and 6 (HDAC2 and HDAC6) with enhanced potency compared to the original anchor (IC50 values of 9.1 and 4.4 nM for the best binders compared to 5.4 and 0.6 µM for the anchor, respectively). The HDAC6 inhibitor is among the most potent reported so far. These results highlight the potential for de novo design of high-affinity protein-peptide interfaces, as well as the challenges that remain.

Anticancer Ruthenium Complexes with HDAC Isoform Selectivity.

The histone deacetylase (HDAC) enzymes have emerged as an important class of molecular targets in cancer therapy, with five inhibitors in clinical use. Recently, it has been shown that a lack of selectivity between the 11 Zn-dependent HDAC isoforms may lead to unwanted side-effects. In this paper, we show that piano stool Ru complexes can act as HDAC inhibitors, and variation in the capping arene leads to differences in HDAC isoform selectivity.

Pharmacological inhibition of HDAC6 reverses cognitive impairment and tau pathology as a result of cisplatin treatment.

Chemotherapy-induced cognitive impairment (CICI) is a commonly reported neurotoxic side effect of chemotherapy, occurring in up to 75% cancer patients. CICI manifests as decrements in working memory, executive functioning, attention, and processing speed, and greatly interferes with patients' daily performance and quality of life. Currently no treatment for CICI has been approved by the US Food and Drug Administration. We show here that treatment with a brain-penetrating histone deacetylase 6 (HDAC6) inhibitor for two weeks was sufficient to fully reverse cisplatin-induced cognitive impairments in male mice, as demonstrated in the Y-maze test of spontaneous alternation, the novel object/place recognition test, and the puzzle box test. Normalization of cognitive impairment was associated with reversal of cisplatin-induced synaptosomal mitochondrial deficits and restoration of synaptic integrity. Mechanistically, cisplatin induced deacetylation of the microtubule protein α-tubulin and hyperphosphorylation of the microtubule-associated protein tau. These cisplatin-induced changes were reversed by HDAC6 inhibition. Our data suggest that inhibition of HDAC6 restores microtubule stability and reverses tau phosphorylation, leading to normalization of synaptosomal mitochondrial function and synaptic integrity and thereby to reversal of CICI. Remarkably, our results indicate that short-term daily treatment with the HDAC6 inhibitor was sufficient to achieve prolonged reversal of established behavioral, structural and functional deficits induced by cisplatin. Because the beneficial effects of HDAC6 inhibitors as add-ons to cancer treatment have been demonstrated in clinical trials, selective targeting of HDAC6 with brain-penetrating inhibitors appears a promising therapeutic approach for reversing chemotherapy-induced neurotoxicity while enhancing tumor control.