STING enhances cell death through regulation of reactive oxygen species and DNA damage.

Resistance to DNA-damaging agents is a significant cause of treatment failure and poor outcomes in oncology. To identify unrecognized regulators of cell survival we performed a whole-genome CRISPR-Cas9 screen using treatment with ionizing radiation as a selective pressure, and identified STING (stimulator of interferon genes) as an intrinsic regulator of tumor cell survival. We show that STING regulates a transcriptional program that controls the generation of reactive oxygen species (ROS), and that STING loss alters ROS homeostasis to reduce DNA damage and to cause therapeutic resistance. In agreement with these data, analysis of tumors from head and neck squamous cell carcinoma patient specimens show that low STING expression is associated with worse outcomes. We also demonstrate that pharmacologic activation of STING enhances the effects of ionizing radiation in vivo, providing a rationale for therapeutic combinations of STING agonists and DNA-damaging agents. These results highlight a role for STING that is beyond its canonical function in cyclic dinucleotide and DNA damage sensing, and identify STING as a regulator of cellular ROS homeostasis and tumor cell susceptibility to reactive oxygen dependent, DNA damaging agents.

The Degradation Chemistry of GSK2879552: Salt Selection and Microenvironmental pH Modulation to Stabilize a Cyclopropyl Amine.

The cyclopropyl amine moiety in GSK2879552 (1) degrades hydrolytically in high pH conditions. This degradation pathway was observed during long-term stability studies and impacted the shelf life of the drug product. This article describes the work to identify the degradation impurities, elucidate the degradation mechanism, and design a stable drug product. It was found that salt selection and control of the microenvironmental pH of the drug product formulation blend significantly improved the chemical stability of the molecule in the solid state.

Analysis of unstable degradation impurities of a benzodiazepine and their quantification without isolation using multiple linear regression.

This manuscript presents a novel methodology for calculating the relative response factors (RRFs) of unstable degradation impurities of molibresib (1). The degradation impurities were observed by HPLC during stress testing and were accompanied by large mass balance deficits. However, the impurities could not be isolated for traditional RRF determination due to their instability. The RRFs of two degradation impurities were determined without isolation by multiple linear regression analysis of HPLC-UV data. The results permitted accurate quantification of the degradants. The benefits and drawbacks of the approach are discussed, including suggested validation acceptance criteria.

Effect of water vapor sorption on local structure of poly(vinylpyrrolidone).

The effect of water vapor sorption on the local structure of poly(vinylpyrrolidone) (PVP), was investigated using high-quality X-ray powder diffraction (XRPD). To examine the effects on molecular scale structure due to polymer chain length and water sorption, different molecular weights of PVP were studied at ambient temperature and different controlled relative humidities. Sorption of water determined gravimetrically on drying and changes to the glass-transition temperature (T(g)) measured by modulated differential scanning calorimetry (mDSC) were found to be consistent with previous reports. The XRPD results show that the position of the high- and low-angle halos for PVP change with the sorption of water. The corresponding characteristic scattering distances display a strong correlation with the measured water content and to T(g). Chemometric analysis was also performed to extract water content information from XRPD data and obtained results are correlated with the values measured gravimetrically, which lends support for the apparent clustering of water in PVP drawn by other techniques.