Temporal changes in the systemic concentrations of retinoids in pregnant and postpartum women.

Retinoids and vitamin A are essential for multiple biological functions, including vision and immune responses, as well as the development of an embryo during pregnancy. Despite its importance, alterations in retinoid homeostasis during normal human pregnancy are incompletely understood. We aimed to characterize the temporal changes in the systemic retinoid concentrations across pregnancy and postpartum period. Monthly blood samples were collected from twenty healthy pregnant women, and plasma concentrations of retinol, all-trans-retinoic acid (atRA), 13-cis-retinoic acid (13cisRA), and 4-oxo-retinoic acids were measured using liquid chromatography-tandem mass spectrometry. Significant decreases in 13cisRA concentrations over the pregnancy were observed, with rebound increases in retinol and 13cisRA levels after delivery. Of note, atRA concentrations exhibited a unique temporal pattern with levels peaking at mid-pregnancy. While the 4-oxo-atRA concentration was below the limit of quantification, 4-oxo-13cisRA was readily detectable, and its temporal change mimicked that of 13cisRA. The time profiles of atRA and 13cisRA remained similar after correction by albumin levels for plasma volume expansion adjustment. Together, the comprehensive profiling of systemic retinoid concentrations over the course of pregnancy provides insights into pregnancy-mediated changes in retinoid disposition to maintain its homeostasis.

Size optimization of carfilzomib nanocrystals for systemic delivery to solid tumors.

Carfilzomib (CFZ) is a second-generation proteasome inhibitor effective in blood cancer therapy. However, CFZ has shown limited efficacy in solid tumor therapy due to the short half-life and poor tumor distribution. Albumin-coated nanocrystal (NC) formulation was shown to improve the circulation stability of CFZ, but its antitumor efficacy remained suboptimal. We hypothesize that NC size reduction is critical to the formulation safety and efficacy as the small size would decrease the distribution in the reticuloendothelial system (RES) and selectively increase the uptake by tumor cells. We controlled the size of CFZ-NCs by varying the production parameters in the crystallization-in-medium method and compared the size-reduced CFZ-NCs (z-average of 168 nm, NC168) with a larger counterpart (z-average of 325 nm, NC325) as well as the commercial CFZ formulation (CFZ-CD). Both CFZ-NCs showed similar or higher cytotoxicity than CFZ-CD against breast cancer cells. NC168 showed greater uptake by cancer cells, less uptake by macrophages and lower immune cell toxicity than NC325 or CFZ-CD. NC168, but not NC325, showed a similar safety profile to CFZ-CD in vivo. The biodistribution and antitumor efficacy of CFZ-NCs in mice were also size-dependent. NC168 showed greater antitumor efficacy and tumor accumulation but lower RES accumulation than NC325 in 4T1 breast cancer model. These results support that NC formulation with an optimal particle size can improve the therapeutic efficacy of CFZ in solid tumors.