Research

Projects currently being pursued

Novel Technologies Based on Luciferase

This project focuses on using bioluminescence to efficiently generate triplet excited states, a process usually achieved for biological chromophores by photoexcitation. Triplet excited states play key roles in natural processes like photosynthesis and in technological advances like photodynamic therapy. This research fills a need for the controlled biological creation of singlet oxygen, a reactive oxygen species (ROS) involved in oxidative stress and the immune response. We will achieve this goal by development of pairs of luciferase mutants and luciferin analogs that can generate triplet states and, via sensitization, singlet oxygen. This species is otherwise very difficult to induce with biological, that is genetic, control. These unnatural luciferin-luciferase pairs will be useful as agents to modify biology by ablation of specific cells in vitro or in vivo based on gene expression and folding of luciferase mutants. These goals intrinsically involve generation of non-native luciferase substrates, whose acceptance by wt firefly luciferase is typically much lower than luciferin. To maximize utility of these analogs, modification of the enzyme using protein engineering techniques will be important.

Immuno-oncology Synergism with Enzyme Inhibitors

The objective of this project is to validate a novel protein target for immuno-oncology and to supply one strategy to inactivate it. It focuses on tumor evasion of the native immune response, which involves signaling to immune cells through multiple pathways other than the checkpoint, one being the tryptophan kynurenine-AHR axis. Aryl hydrocarbon receptor (AHR) activation also promotes tumor cell survival and proliferation. Inhibitors of the first step in the KYN pathway, indoleamine-2,3-dioxygenase (IDO), have been studied clinically (KEYNOTE trial) in combination with checkpoint inhibitors, without much success. However, it was recently shown that another enzyme in the KYN pathway, IL4I1, correlates better than IDO with AHR activation, making it a more attractive drug target. Tryptophan metabolites like indole-3-pyruvate (I3P) that play a key role in activating the AHR are produced only by IL4I1, not IDO. This work will validate the KYN pathway as a target for cancer drugs and provide an inhibitor of the most relevant enzyme in the pathway. It exploits known enzymology of the target flavoenzyme family and compounds that are known to inactivate related enzymes in the family.

Serine Peptide Assembly

The objectives of this project are the development, using novel peptide coupling/ligation chemistries, of new syntheses of two native peptide drugs and one peptide-based natural product. These syntheses will be far more sustainable than extant syntheses (by minimizing chemical steps, reagent use, and waste production). They exploit a new methodology we are developing, serine peptide assembly (SPA), that has parallels in well-known native chemical ligation chemistry, but is performed at high reagent concentration in organic media. They also will use another methodology we are developing, aminoacylation with N-carboxyanhydride (NCA) amino acid derivatives, which can halve the number of steps in peptide synthesis.