Mutant p53 reactivator SLMP53-2 hinders ultraviolet B radiation-induced skin carcinogenesis.

The growing incidence of skin cancer (SC) has prompted the search for additional preventive strategies to counteract this global health concern. Mutant p53 (mutp53), particularly with ultraviolet radiation (UVR) signature, has emerged as a promising target for SC prevention based on its key role in skin carcinogenesis. Herein, the preventive activity of our previously disclosed mutp53 reactivator SLMP53-2 against UVR-induced SC was investigated. The pre-treatment of keratinocyte HaCaT cells with SLMP53-2, before UVB exposure, depleted mutp53 protein levels with restoration of wild-type-like p53 DNA-binding ability and subsequent transcriptional activity. SLMP53-2 increased cell survival by promoting G1-phase cell cycle arrest, while reducing UVB-induced apoptosis through inhibition of c-Jun N-terminal kinase (JNK) activity. SLMP53-2 also protected cells from reactive oxygen species and oxidative damage induced by UVB. Moreover, it enhanced DNA repair through upregulation of nucleotide excision repair pathway and depletion of UVB-induced DNA damage, as evidenced by a reduction of DNA in comet tails, γH2AX staining and cyclobutane pyrimidine dimers (CPD) levels. SLMP53-2 further suppressed UVB-induced inflammation by inhibiting the nuclear translocation and DNA-binding ability of NF-κB, and promoted the expression of key players involved in keratinocytes differentiation. Consistently, the topical application of SLMP53-2 in mice skin, prior to UVB irradiation, reduced cell death and DNA damage. It also decreased the expression of inflammatory-related proteins and promoted cell differentiation, in UVB-exposed mice skin. Notably, SLMP53-2 did not show signs of skin toxicity for cumulative topical use. Overall, these results support a promising protective activity of SLMP53-2 against UVB-induced SC.

Antimalarial drugs: what's new in the patents?

INTRODUCTION: The efficacy of current therapeutic warheads in preventing malaria transmission or treating the disease is often hampered by the emergence of drug-resistance. No effective vaccines are available to date, and novel drugs able to counteract drug-resistant forms of malaria and/or to target multiple stages of the parasite's lifecycle are urgently needed. AREAS COVERED: This review covers patents that protect antimalarial small molecules bearing the artemisinin or other chemical scaffolds, as well as vaccines, that have been published in the period 2015-2022. Literature was searched in public databases of articles and patents. Patents protecting small molecules that prevent malaria transmission are not discussed herein. EXPERT OPINION: Significant progress has been made in the design of antimalarial agents. Most of these candidates have been tested in standardized strains, with the use of Plasmodium clinical isolates for testing still underdeveloped. Several compounds have been profiled in in vivo mouse models of malaria, including humanized mice. Despite having different efficacy, these new molecules might further progress the field and hopefully will advance to clinical development soon.

Hybrid molecules of protoflavones and spirooxindole derivatives with selective cytotoxicity against triple-negative breast cancer cells.

The combination of compounds with complementary bioactivities into hybrid molecules is an emerging concept in drug discovery. In this study, we aimed to synthesize new hybrid compounds based on p53-MDM2/X protein-protein interaction spiropyrazoline oxindole-based inhibitors and ataxia telangiectasia and Rad3-related (ATR) protoflavone-based inhibitors through copper(i) catalysed azide-alkyne cycloaddition. Five new hybrids were prepared along with three representative reference fragments. The compounds were tested against human breast cancer cell lines MCF-7 (hormone-dependent, wild-type p53) and MDA-MB-231 (triple-negative, mutant p53). Most of the new hybrids were more cytotoxic than their reference fragments and several showed 2-4 times selective toxicity against MDA-MB-231 cells. Relevant pharmacological benefit gained from the hybrid coupling was further confirmed by virtual combination index calculations using the Chou method. Compound 13 modulated doxorubicin-induced DNA damage response through inhibiting the ATR-dependent activation of Chk-1, while increasing the activation of Chk-2. Our results suggest that the new hybrids may serve as new leads against triple negative breast cancer.

Discovery of spirooxadiazoline oxindoles with dual-stage antimalarial activity.

Malaria remains a prevalent infectious disease in developing countries. The first-line therapeutic options are based on combinations of fast-acting artemisinin derivatives and longer-acting synthetic drugs. However, the emergence of resistance to these first-line treatments represents a serious risk, and the discovery of new effective drugs is urgently required. For this reason, new antimalarial chemotypes with new mechanisms of action, and ideally with activity against multiple parasite stages, are needed. We report a new scaffold with dual-stage (blood and liver) antiplasmodial activity. Twenty-six spirooxadiazoline oxindoles were synthesized and screened against the erythrocytic stage of the human malaria parasite P. falciparum. The most active compounds were also tested against the liver-stage of the murine parasite P. berghei. Seven compounds emerged as dual-stage antimalarials, with IC50 values in the low micromolar range. Due to structural similarity with cipargamin, which is thought to inhibit blood-stage P. falciparum growth via inhibition of the Na + efflux pump PfATP4, we tested one of the most active compounds for anti-PfATP4 activity. Our results suggest that this target is not the primary target of spirooxadiazoline oxindoles and further studies are ongoing to identify the main mechanism of action of this scaffold.

Discovery of MDM2-p53 and MDM4-p53 protein-protein interactions small molecule dual inhibitors.

MDM2 and MDM4 are key negative regulators of p53, an important protein involved in several cell processes (e.g. cell cycle and apoptosis). Not surprisingly, the p53 tumor suppressor function is inactivated in tumors overexpressing these two proteins. Therefore, both MDM2 and MDM4 are considered important therapeutic targets for an effective reactivation of the p53 function. Herein, we present our studies on the development of spiropyrazoline oxindole small molecules able to inhibit MDM2/4-p53 protein-protein interactions (PPIs). Twenty-seven potential spiropyrazoline oxindole dual inhibitors were prepared based on in silico structural optimization studies of a hit compound with MDM2 and MDM4 proteins. The antiproliferative activity of the target compounds was evaluated in cancer cell lines harboring wild-type p53 and overexpressing MDM2 and/or MDM4. The most active compounds in SJSA-1 cells, 2q and 3b, induce cell death via apoptosis and control cell growth by targeting the G0/G1 cell cycle checkpoint in a concentration-dependent manner. The ability of the five most active spiropyrazoline oxindoles in dissociating p53 from MDM2 and MDM4 was analyzed by an immunoenzymatic assay. Three compounds inhibited MDM2/4-p53 PPIs with IC50 values in the nM range, while one compound inhibited more selectively the MDM2-p53 PPI over the MDM4-p53 PPI. Collectively, these results show: i) 3b may serve as a valuable lead for obtaining selective MDM2-p53 PPI inhibitors and more efficient anti-osteosarcoma agents; ii) 2a, 2q and 3f may serve as valuable leads for obtaining dual MDM2/4 inhibitors and more effective p53 activators.

Potency and Selectivity Optimization of Tryptophanol-Derived Oxazoloisoindolinones: Novel p53 Activators in Human Colorectal Cancer.

To search for novel p53 activators, four series of novel (S)- and (R)-tryptophanol-derived oxazoloisoindolinones were synthesized in a straightforward manner and their antiproliferative activity was evaluated in the human colorectal cancer HCT116 cell line. Structural optimization of the hit compound SLMP53-1 led to the identification of a (R)-tryptophanol-derived isoindolinone that was found to be six-fold more active, with increased selectivity for HCT116 cells with p53 and with low toxicity in normal cells. Binding studies with MDM2 showed that the antiproliferative activity of tryptophanol-derived isoindolinones does not involve inhibition of the main negative regulator of the p53 protein. Molecular docking simulations showed that although these molecules establish hydrophobic interactions with MDM2, they do not possess the required features to bind MDM2.

Small Molecules Targeting Mutant P53: A Promising Approach for Cancer Treatment.

More than half of all human tumors express mutant forms of p53, with the ovary, lung, pancreas, and colorectal cancers among the tumor types that display the highest prevalence of p53 mutations. In addition, the expression of mutant forms of p53 in tumors is associated with poor prognosis due to increased chemoresistance and invasiveness. Therefore, the pharmacological restoration of wild-type-like activity to mutant p53 arises as a promising therapeutic strategy against cancer. This review is focused on the most relevant mutant p53 small molecule reactivators described to date. Despite some of them have entered into clinical trials, none has reached the clinic, which emphasizes that new pharmacological alternatives, particularly with higher selectivity and lower adverse toxic side effects, are still required.

An Update on MDMX and Dual MDM2/X Inhibitors.

The tumor suppressor protein p53 is inactivated in all types of human cancers, either by negative regulation, by mutation or deletion of its gene. Specifically, in tumors that retain wild-type (wt) p53 status, p53 is inactivated by interaction with negative regulators, such as MDM2 and MDMX. These two proteins are found to be overexpressed in several different types of cancers, and the restoration of p53 activity by inhibition of these proteins is now considered an important approach for cancer treatment. The first studies using this strategy to reactivate wt p53 were focused on the development of small molecules that could inhibit MDM2. In this way, p53 could be liberated and act again as a tumor suppressor. From these studies, nine small molecules have reached clinical trials. More recently, MDMX was also identified as an important therapeutic target to efficiently reactivate wt p53, and it is now considered that, for full p53 reactivation, dual inhibition of MDM2 and MDMX is required. In this review we will focus on the most recent advances in the discovery of novel small molecules and stapled peptides that act as selective MDMX inhibitors or as dual MDM2/X inhibitors.