Metabolism-Guided Optimization of Tryptophanol-Derived Isoindolinone p53 Activators

For the first time, the pharmacokinetic (PK) profile of tryptophanol-derived isoindolinones, previously reported as p53 activators, was investigated. From the metabolites' identification, performed by liquid chromatography coupled to high resolution tandem mass spectrometry (LC-HRMS/MS), followed by their preparation and structural elucidation, it was possible to identify that the indole C2 and C3 are the main target of the cytochrome P450 (CYP)-promoted oxidative metabolism in the tryptophanol-derived isoindolinone scaffold. Based on these findings, to search for novel p53 activators a series of 16 enantiopure tryptophanol-derived isoindolinones substituted with a bromine in indole C2 was prepared, in yields of 62-89%, and their antiproliferative activity evaluated in human colon adenocarcinoma HCT116 cell lines with and without p53. Structural optimization led to the identification of two (S)-tryptophanol-derived isoindolinones 3.9-fold and 1.9-fold more active than hit SLMP53-1, respectively. Compounds' metabolic stability evaluation revealed that this substitution led to a metabolic switch, with the impact of Phase I oxidative metabolism being minimized. Through differential scanning fluorimetry (DSF) experiments, the most active compound of the series in cell assays led to an increase in the protein melting temperature (Tm) of 10.39 °C, suggesting an effective binding to wild-type p53 core domain.

Abstract P030: Chemoprevention by the mutant p53 reactivator SLMP53-2 on ultraviolet radiation-induced skin cancer

The growing incidence of skin cancer (SC) is a global public health concern. Preventive approaches mostly embrace the sunscreen use against ultraviolet radiation (UVR), the main SC etiologic factor. Yet, the increasing SC incident have suggested that additional preventive agents could complement the sunscreen, helping to reverse this trend. Mutant p53 (mutp53) represents a promising target in SC prevention, since its occurrence is a key early event in UVR-induced SC. Thus, the inhibition of mutp53 formation by mutp53 reactivators, which are able to restore the wild-type-like function to p53, would be a valuable strategy for SC prevention. Recently, our group identified the tryptophanol-derived oxazoloisoindolinone SLMP53-2 as a new mutp53 reactivator. Herein, we aimed to study the potential of SLMP53-2 as a chemopreventive drug against UVR-induced SC. For that, assays with normal human keratinocyte HaCaT cells were performed. Cells were pre-treated with SLMP53-2 for 24h, followed by exposure to distinct UVB doses and further analysis. For in vivo studies, FVB/N mice were topically pre-treated for 1h prior to UVB radiation (180 mJ/cm2) and the skin was collected 24h after for immunohistochemistry/immunofluorescence analysis. Pre-treatment of HaCaT cells with SLMP53-2 enhanced cell survival in response to UVB with promotion of cell cycle arrest in G0/G1 phase, upregulation of p21 protein levels, reduction of UVB-induced apoptosis, and inhibition of JNK activity. SLMP53-2 also protected cells from UVB-induced ROS generation and from its consequent lipid peroxidation and protein carbonylation. It enhanced DNA repair through upregulation of the protein and mRNA levels of XPC (xeroderma pigmentosum complementation group C) and DDB-2 (DNA damaged binding protein 2) from the NER (nucleotide excision repair) pathway. In fact, SLMP53-2 depleted UVB-induced DNA damage, as evidenced by a reduction of DNA in comet tails, γH2AX staining and cyclobutane pyrimidine dimers (CPDs) levels. SLMP53-2 also showed promising activity in suppressing UVB-induced inflammation, decreasing COX-2, IL-6 and TNF-α protein levels and reducing NF-kB nuclear translocation and DNA binding ability. Moreover, SLMP53-2 enhanced the expression of key players in keratinocytes differentiation, namely NOTCH1 and keratin 1. Consistently, pre-treatment with SLMP53-2 reduced mutp53 protein levels by potentially restoring its wild-type p53 form, which may underlie the increased resistance of HaCaT cells to UVB harmful effects. Importantly, in vivo studies supported that SLMP53-2 pre-treatment of UVB-irradiated mice promoted the survival of epidermal cells, reducing the DNA damage by enhancement of DNA repair and downregulating mutp53 expression levels. Further, it reduced the expression of inflammatory-related proteins and promoted cell differentiation. Collectively, these results support a promising chemopreventive activity for SLMP53-2 against UVB-induced skin damage. We thank FCT/MCTES for the projects UIDB/50006/2020, UIDP/04423/2020 and fellowship SFRH/BD/128673/2017 (J.B. Loureiro).

Citation Format: Joana B. Loureiro, Rita Ribeiro, Nair Nazareth, Tiago Ferreira, Adelina Quaresma, Valentina Barcherini, Laura Marabini, Paula A. Oliveira, Maria M. M. Santos, Lucília Saraiva. Chemoprevention by the mutant p53 reactivator SLMP53-2 on ultraviolet radiation-induced skin cancer [abstract]. In: Proceedings of the AACR-NCI-EORTC Virtual International Conference on Molecular Targets and Cancer Therapeutics; 2021 Oct 7-10. Philadelphia (PA): AACR; Mol Cancer Ther 2021;20(12 Suppl):Abstract nr P030.

Tryptophanol-Derived Oxazolopyrrolidone Lactams as Potential Anticancer Agents against Gastric Adenocarcinoma

Gastric cancer is one of the deadliest cancers in modern societies, so there is a high level of interest in discovering new drugs for this malignancy. Previously, we demonstrated the ability of tryptophanol-derived polycyclic compounds to activate the tumor suppressor protein p53, a relevant therapeutic target in cancer. In this work, we developed a novel series of enantiomerically pure tryptophanol-derived small molecules to target human gastric adenocarcinoma (AGS) cells. From an initial screening of fourteen compounds in AGS cell line, a hit compound was selected for optimization, leading to two derivatives selective for AGS gastric cells over other types of cancer cells (MDA-MB-231, A-549, DU-145, and MG-63). More importantly, the compounds were non-toxic in normal cells (HEK 293T). Additionally, we show that the growth inhibition of AGS cells induced by these compounds is mediated by apoptosis. Stability studies in human plasma and human liver microsomes indicate that the compounds are stable, and that the major metabolic transformations of these molecules are mono- and di-hydroxylation of the indole ring.

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.