Jeff Krise Research
Intracellular drug delivery and disposition
The Krise laboratory seeks to understand how drugs distribute and localize within human cells and how this influences their therapeutic activity and pharmacokinetic distribution properties. Much of our recent studies have focused on the intracellular distribution of amine-containing drugs and their propensity to become highly concentrated in acidic intracellular compartments such as lysosomes according to an ion trapping-type mechanism. We employ a variety of techniques to study drug accumulation in lysosomes including florescence microscopy, phase contrast microscopy and electron microscopy. The laboratory has also developed and refined methods for fractionating cells, which allow us to directly measure the concentration of drugs within organelles using LC/MS/MS analysis. Employing a combination of these approaches the laboratory has pioneered research that has established how physicochemical properties of drugs, including pKa and permeability properties, correlate with intracellular distribution. Using this information, we routinely collaborate with scientists within the pharmaceutical industry to assist them in the design of drugs with optimized intracellular distribution behavior in an effort to augment activity and pharmacokinetic distribution properties.
We are also fundamentally interested in understanding the biology of drug transport within cells. We specifically study the lysosomal accumulation and trafficking of membrane-impermeable solutes and drugs and examine how drugs and lysosomal storage diseases influence these events. Towards this end, we currently study the Niemann Pick Type C class of proteins (i.e., NPC1 and NPC2), which we have shown to function in this regard. Ultimately, it is our hope that research in this area leads to the development of novel therapies that may benefit patients afflicted with lysosomal diseases of varying etiology.
The laboratory also examines the distribution of anticancer drugs inside cancer cells in an effort to improve their activity and selectivity. We have shown that many cancer cells are unusual in that they have defective acidification of lysosomes, which causes significant alterations in their intracellular distribution of weakly basic anticancer agents. This observation inspired the creation of an entirely new drug targeting strategy that was designed to increase the selectivity of cancer drugs to cancer cells. Traditional drug-delivery based targeting approaches rely on the premise that in order to improve selectivity one must promote preferential distribution of the drug in cancer cells, a feat that is theoretically flawed for most membrane-permeable drugs. Our strategy is fundamentally different in that it allows for equal distribution of drugs in normal and cancer cells. Instead, we focus on the design of drugs so that they have relatively unfavorable intracellular distribution in normal cells (i.e., away from targets) and more favorable intracellular distribution in cancer cells. We refer to this as intracellular distribution-based drug targeting and we believe that the basic premise for this drug targeting platform has applications well beyond cancer chemotherapy.
Finally, we are interested in how drug localization and kinetic accumulation behavior observed in single cells grown in culture correlates with global in vivo pharmacokinetic distribution properties. We propose that such a relationships exists considering that the human body is comprised of some 10 trillion single cells. We have recently shown that exposure of cells to one drug can dramatically alter the intracellular distribution and accumulation of a secondarily administered drug. This, we propose, provides important insight into a previously unexplored pathway for drug-drug interactions that may help account for the wide intra- and inter-patient variability in drug elimination half-life that has been observed with many drugs.