Series of Novel and Highly Potent Cyclic Peptide PCSK9 Inhibitors Derived from an mRNA Display Screen and Optimized via Structure-Based Design.

Proprotein convertase subtilisin-like/kexin type 9 (PCSK9) is a key regulator of plasma LDL-cholesterol (LDL-C) and a clinically validated target for the treatment of hypercholesterolemia and coronary artery disease. In this paper, we describe a series of novel cyclic peptides derived from an mRNA display screen which inhibit the protein-protein interaction between PCSK9 and LDLR. Using a structure-based drug design approach, we were able to modify our original screening lead 2 to optimize the potency and metabolic stability and minimize the molecular weight to provide novel bicyclic next-generation PCSK9 inhibitor peptides such as 78. These next-generation peptides serve as a critical foundation for continued exploration of potential oral, once-a-day PCSK9 therapeutics for the treatment of cardiovascular disease.

From Screening to Targeted Degradation: Strategies for the Discovery and Optimization of Small Molecule Ligands for PCSK9.

Proprotein convertase substilisin-like/kexin type 9 (PCSK9) is a serine protease involved in a protein-protein interaction with the low-density lipoprotein (LDL) receptor that has both human genetic and clinical validation. Blocking this protein-protein interaction prevents LDL receptor degradation and thereby decreases LDL cholesterol levels. Our pursuit of small-molecule direct binders for this difficult to drug PPI target utilized affinity selection/mass spectrometry, which identified one confirmed hit compound. An X-ray crystal structure revealed that this compound was binding in an unprecedented allosteric pocket located between the catalytic and C-terminal domain. Optimization of this initial hit, using two distinct strategies, led to compounds with high binding affinity to PCSK9. Direct target engagement was demonstrated in the cell lysate with a cellular thermal shift assay. Finally, ligand-induced protein degradation was shown with a proteasome recruiting tag attached to the high-affinity allosteric ligand for PCSK9.

In vitro growth of mouse preantral follicles: effect of animal age and stem cell factor/insulin-like growth factor supplementation.

OBJECTIVE: To determine whether animal age impacts in vitro preantral follicle growth. Effects of hCG, stem cell factor (SCF), and/or insulin-like growth factor (IGF) supplementation in growth medium were also investigated. METHODS: Intact preantral follicles were mechanically isolated from fresh ovaries of BDF1 mice and cultured in growth medium for 9 to 11 days. Surviving follicles with antrum formation were transferred to maturation medium for 14 to 18 hours. Follicle survival, antrum formation, and retrieval of metaphase II (MII) oocytes were compared among three age categories (4-5, 7-8, and 10-11 week-old). By using 7- to 8-week-old mice, preantral follicles were cultured in growth medium supplemented with hCG (0, 5, or 10 mIU/mL), SCF (50 ng/mL), IGF-1 (50 ng/mL), and SCF+IGF-1. RESULTS: Seven- to eight-week-old mice showed a higher follicle survival and antrum formation and produced more MII oocytes compared to other groups. In the 7- to 8-week-old mice, supplementation of 5 mIU/mL hCG significantly enhanced the antrum formation but the percentage of MII oocytes was similar to that of the control. Supplementation of SCF+IGF-1 did not enhance follicle survival or antrum formation but the percentage of MII oocytes increased modestly (39.1%) than in the control (28.6%, statistically not significant). CONCLUSION: Seven- to eight-week-old mice showed better outcomes in growth of preantral follicles in vitro than 4- to 5- or 10- to 11-week-old mice. Supplementation of hCG enhanced antrum formation and supplementation of SCF+IGF-1 yielded more mature oocytes; hence, these should be considered in the growth of preantral follicles in vitro.

Effect of sphingosine-1-phosphate supplementation on follicular integrity of vitrified-warmed mouse ovarian grafts.

OBJECTIVE: To investigates the effect of sphingosine-1-phosphate (S1P) supplementation on follicular integrity and apoptosis in vitrified-warmed mouse ovarian grafts. STUDY DESIGN: Ovaries from 4-week-aged ICR mice were vitrified using a vitrification solution with or without 2 µM S1P. After warming, follicular normality was assessed by histological analysis and TUNEL assay. A part of ovaries vitrified with or without 2 µM S1P was transplanted, and 2 weeks later, gross and microscopic follicular morphology was assessed. RESULTS: During vitrification and warming, inclusion of 2 µM S1P into the vitrification solution significantly raised the rate of morphologically intact follicles compared to controls (36.6% vs. 30.8%, p=0.047). This protective effect was profound especially in primordial follicles (45.5% vs. 34.6%, p=0.034). After transplantation of vitrified-warmed ovaries, the morphological integrity of primordial follicles was superior in the S1P-treated group (55.0% vs. 39.4%, p=0.035). The rates of non-apoptotic follicles (TUNEL-negative) were similar in the two groups in either non-transplanted or transplanted ovaries. CONCLUSION: Inclusion of S1P in the vitrification solution during transplantation of vitrified-warmed ovary had a beneficial effect on preservation of the primordial follicular pool.