ONC201 and imipridones: Anti-cancer compounds with clinical efficacy

ONC201 was originally discovered as TNF-Related Apoptosis Inducing Ligand (TRAIL)-inducing compound TIC10. ONC201 appears to act as a selective antagonist of the G protein coupled receptor (GPCR) dopamine receptor D2 (DRD2), and as an allosteric agonist of mitochondrial protease caseinolytic protease P (ClpP). Downstream of target engagement, ONC201 activates the ATF4/CHOP-mediated integrated stress response leading to TRAIL/Death Receptor 5 (DR5) activation, inhibits oxidative phosphorylation via c-myc, and inactivates Akt/ERK signaling in tumor cells. This typically results in DR5/TRAIL-mediated apoptosis of tumor cells; however, DR5/TRAIL-independent apoptosis, cell cycle arrest, or antiproliferative effects also occur. The effects of ONC201 extend beyond bulk tumor cells to include cancer stem cells, cancer associated fibroblasts and immune cells within the tumor microenvironment that can contribute to its efficacy. ONC201 is orally administered, crosses the intact blood brain barrier, and is under evaluation in clinical trials in patients with advanced solid tumors and hematological malignancies. ONC201 has single agent clinical activity in tumor types that are enriched for DRD2 and/or ClpP expression including specific subtypes of high-grade glioma, endometrial cancer, prostate cancer, mantle cell lymphoma, and adrenal tumors. Synergy with radiation, chemotherapy, targeted therapy and immune-checkpoint agents has been identified in preclinical models and is being evaluated in clinical trials. Structure-activity relationships based on the core pharmacophore of ONC201, termed the imipridone scaffold, revealed novel potent compounds that are being developed. Imipridones represent a novel approach to therapeutically target previously undruggable GPCRs, ClpP, and innate immune pathways in oncology.

Inhibitors of human histone deacetylase with potent activity against the African trypanosome Trypanosoma brucei

A number of hydroxamic acid derivatives which inhibit human histone deacetylases were investigated for efficacy against cultured bloodstream form Trypanosoma brucei. Three out of the four classes tested displayed significant activity. The majority of compounds blocked parasite growth in the submicromolar range. The most potent was a member of the sulphonepiperazine series with an IC(50) of 34nM. These results identify lead compounds with potential for the development of a novel class of trypanocidal agent.

Novel tricyclic pyrazole BRAF inhibitors with imidazole or furan central scaffolds

V-RAF murine sarcoma viral oncogene homolog B1 (BRAF) is a serine/threonine-specific protein kinase that is mutated with high frequency in cutaneous melanoma, and many other cancers. Inhibition of mutant BRAF is an attractive therapeutic approach for the treatment of melanoma. A triarylimidazole BRAF inhibitor bearing a phenylpyrazole group (dimethyl-[2-(4-{5-[4-(1H-pyrazol-3-yl)-phenyl]-4-pyridin-4-yl-1H-imidazol-2-yl}-phenoxy)-ethyl]-amine, 1a) was identified as an active BRAF inhibitor. Based on this starting point, we synthesized a series of analogues leading to the discovery of 6-{2-[4-(4-methyl-piperazin-1-yl)-phenyl]-5-pyridin-4-yl-3H-imidazol-4-yl}-2,4-dihydro-indeno[1,2-c]pyrazole (1j), with nanomolar activity in three assays: inhibition of purified mutant BRAF activity in vitro; inhibition of oncogenic BRAF-driven extracellular regulated kinase (ERK) activation in BRAF mutant melanoma cell lines; and inhibition of proliferation in these cells.

Crystal structures and inhibitor identification for PTPN5, PTPRR and PTPN7: a family of human MAPK-specific protein tyrosine phosphatases

Protein tyrosine phosphatases PTPN5, PTPRR and PTPN7 comprise a family of phosphatases that specifically inactivate MAPKs (mitogen-activated protein kinases). We have determined high-resolution structures of all of the human family members, screened them against a library of 24000 compounds and identified two classes of inhibitors, cyclopenta[c]quinolinecarboxylic acids and 2,5-dimethylpyrrolyl benzoic acids. Comparative structural analysis revealed significant differences within this conserved family that could be explored for the design of selective inhibitors. PTPN5 crystallized, in two distinct crystal forms, with a sulphate ion in close proximity to the active site and the WPD (Trp-Pro-Asp) loop in a unique conformation, not seen in other PTPs, ending in a 3(10)-helix. In the PTPN7 structure, the WPD loop was in the closed conformation and part of the KIM (kinase-interaction motif) was visible, which forms an N-terminal aliphatic helix with the phosphorylation site Thr66 in an accessible position. The WPD loop of PTPRR was open; however, in contrast with the structure of its mouse homologue, PTPSL, a salt bridge between the conserved lysine and aspartate residues, which has been postulated to confer a more rigid loop structure, thereby modulating activity in PTPSL, does not form in PTPRR. One of the identified inhibitor scaffolds, cyclopenta[c]quinoline, was docked successfully into PTPRR, suggesting several possibilities for hit expansion. The determined structures together with the established SAR (structure-activity relationship) propose new avenues for the development of selective inhibitors that may have therapeutic potential for treating neurodegenerative diseases in the case of PTPRR or acute myeloblastic leukaemia targeting PTPN7.

Chondroitin sulphate structure affects its immunological activities on murine splenocytes sensitized with ovalbumin

Chondroitin sulphate (CS) is a glycosaminoglycan widely distributed in animal tissues, which has anti-inflammatory and chondroprotective properties. We reported previously that chondroitin 4-sulphate (CS-A) up-regulates the antigen-specific Th1 immune response of murine splenocytes sensitized with ovalbumin in vitro, and that CS suppresses the antigen-specific IgE responses. We now demonstrate that a specific sulphation pattern of the CS polysaccharide is required for the Th1-promoted activity, as other polysaccharides such as dextran and dextran sulphate do not significantly induce this activity. While the presence of some O-sulpho groups appear to be essential for activity, CS-A, and synthetically prepared, partially O-sulphonated CS, induce higher Th1-promoted activity than synthetically prepared, fully O-sulphonated CS. CS-A induces an activity greater than chondroitin sulphate B (CS-B) or chondroitin 6-sulphate (CS-C). In addition, chondroitin sulphate E (CS-E) induces greater activity than CS-A or CS-D. These results suggest that the GlcA(beta1-3)GalNAc(4,6-O-disulpho) sequence in CS-E is important for Th1-promoted activity. Furthermore, rat anti-mouse CD62L antibody, an antibody to L-selectin, inhibits the Th1-promoting activity of CS. These results suggest that the Th1-promoted activity could be associated with L-selectin on lymphocytes. These findings describe a new mechanism for the anti-inflammatory and chondroprotective properties of CS that may be useful in designing new therapeutic applications for CS used in the treatment of immediate-type hypersensitivity.