Molecular sieving of red cell membranes during gradual osmotic hemolysis

Summary Rat red blood corpuscles were held stationary with respect to a continuously flowing solution in either a specially constructed centrifuge or in glass filters. The concentration of the solution was gradually decreased to cause the swelling and subsequent gradual osmotic hemolysis of the cells. The passage of the intracellular molecules —potassium, adenylate kinase, and hemoglobin—across the cell membranes and into the flowing solution was determined as a function of time. Ions and molecules begin passage across the membranes in the order of increasing molecular size. The initial flow of potassium is followed by the initial flows of hemoglobin and adenylate kinase. The flow of hemoglobin has been interpreted as the flows of hemoglobin monomers, dimers, and tetramers such that the time sequence is: potassium; hemoglobin monomer; adenylate kinase/hemoglobin dimer; and finally, hemoglobin tetramer. It is concluded that the stressed cell membrane has molecular sieving properties and that the exclusion limit (effective hole size) increases as a function of time during the initial stages of gradual osmotic hemolysis. The process of gradual osmotic hemolysis is discussed in terms of molecular sieving through stress-induced effective membrane holes. It is suggested that a portion of the membrane protein might form an elastic network which would account for the gradual increase in size and apparent homogeneity of the effective holes.This work was prepared under the auspices of the U.S. Atomic Energy Commission.     

Discovery of 7-(3-(piperazin-1-yl)phenyl)pyrrolo[2,1-f][1,2,4]triazin-4-amine derivatives as highly potent and selective PI3Kδ inhibitors

As demonstrated in preclinical animal models, the disruption of PI3Kδ expression or its activity leads to a decrease in inflammatory and immune responses. Therefore, inhibition of PI3Kδ may provide an alternative treatment for autoimmune diseases, such as RA, SLE, and respiratory ailments. Herein, we disclose the identification of 7-(3-(piperazin-1-yl)phenyl)pyrrolo[2,1-f][1,2,4]triazin-4-amine derivatives as highly potent, selective and orally bioavailable PI3Kδ inhibitors. The lead compound demonstrated efficacy in an in vivo mouse KLH model.     

Design and characterization of MP0250, a tri-specific anti-HGF/anti-VEGF DARPin® drug candidate

MP0250 is a multi-domain drug candidate currently being tested in clinical trials for the treatment of cancer. It comprises one anti-vascular endothelial growth factor-A (VEGF-A), one anti-hepatocyte growth factor (HGF), and two anti-human serum albumin (HSA) DARPin® domains within a single polypeptide chain. While there is first clinical validation of a single-domain DARPin® drug candidate, little is known about DARPin® drug candidates comprising multiple domains. Here, we show that MP0250 can be expressed at 15 g/L in soluble form in E. coli high cell-density fermentation, it is stable in soluble/frozen formulation for 2 years as assessed by reverse phase HPLC, it has picomolar potency in inhibiting VEGF-A and HGF in ELISA and cellular assays, and its domains are simultaneously active as shown by surface plasmon resonance. The inclusion of HSA-binding DARPin® domains leads to a favorable pharmacokinetic profile in mouse and cynomolgus monkey, with terminal half-lives of ～ 30 hours in mouse and ～ 5 days in cynomolgus monkey. MP0250 is thus a highly potent drug candidate that could be particularly useful in oncology. Beyond MP0250, the properties of MP0250 indicate that multi-domain DARPin® proteins can be valuable next-generation drug candidates.