In vitro activity: PRIMA-1 is converted to compounds that form adducts with thiols in mutant p53. Modification of thiol groups in mutant p53 by PRIMA-1 conversion products is sufficient to restore its tumor suppressor activity. PRIMA-1 inhibits the growth of pancreatic cancer cell lines and induces cell cycle arrest and decreases DNA synthesis. It selectively induces apoptosis and cell death in mutant p53-expressing pancreatic cancer cells and also leads to activation of p53-dependent apoptotic pathways. PRIMA-1 enhances the cytotoxicity of chemotherapeutic agents active against mutant p53 pancreatic cancer cells. PRIMA-1 has antileukemic properties in acute promyelocytic leukemia-derived NB4 cells. PRIMA-1-triggered apoptosis is in a dose-dependent and time-dependent manner as indicated by the MTT assay and annexin-V staining. Apoptosis induction by PRIMA-1 is associated with caspase-9, caspase-7 activation and PARP cleavage. PRIMA-1 does not show any significant apoptotic effect in normal human peripheral blood mononuclear cells.

Kinase Assay: PRIMA-1 is a mutant p53 reactivator, restores the sensitivity of TP53 mutant-type thyroid cancer cells to the histone methylation inhibitor 3-Deazaneplanocin A.

Cell Assay: Cells [mutant p53 expressing pancreatic cancer cell lines PANC-1 (p.R273H) and BxPC-3 (p.Y220C) and the wild type p53-expressing Capan-2 cells (wtp53)] are kept at a temperature of 37 °C, a minimum relative humidity of 95 %, and an atmosphere of 5 % CO2 in air. Cell viability is measured by MTT assay after treatment with PRIMA-1. Briefly, cells are seeded in each well of 96-well plates in 100 μl culture medium and incubated overnight at 37 °C in an atmosphere of 5 % CO2. The next day, the medium is removed and cells washed with PBS and treated with vehicle control(DMSO, dimethylsulfoxide) or different concentrations of PRIMA-1 for 12 to 48 h; the medium is replaced with MTT solution diluted in medium once the treatment is completed. The plates are further incubated at 37 °C under 5 % CO2 for 4 h and then left at room temperature until completely dry. DMSO was then added and the absorbance is read at 492 nm using a microplate enzyme-linked immunoassay reader (ELISA). The relative growth activity is determined as the percentage absorbance of treated cells compared to that of vehicle treated cells (control).

Intravenous (i.v.) injections of PRIMA-1 in mice does not cause any obvious changes in weight or behavior compared with untreated animals. PRIMA-1 has in vivo antitumor activity in this animal tumor model. It suppresses in vivo tumor growth in a mutant p53-dependent manner.