I enjoy applying chemistry to solve problems in biology, especially those related to drug design and discovery. Being a chemist by training, my research is necessarily collaborative, involving labs from biology, pharmacology, and the clinical sciences. Although our projects may focus on different biological targets, our role is consistent. We study relationships between molecular structure and biological function (typically small molecule – large molecular interactions) to rationalize the design of improved therapeutics using SAR studies, biochemical assays, and structural analyses (including X-ray crystallography, molecular modeling, and spectroscopy).
When I arrived at Minnesota in the early 90’s, the initial focus of my lab was on opioids and G protein-coupled receptor function. Over the years, we made substantial contributions to this field and were one of the first groups to apply structure-based models to the design of selective opioid agonists and antagonists.
We also performed seminal work on salvinorin, a potent kappa opioid agonist that gained popularity in the street drug culture for its hallucinogenic properties. Using a combination of site directed mutagenesis studies and computer modeling, we described a unique binding site model that placed salvinorin A in a pocket that shares limited overlap with traditional kappa selective opiates. This orientation is shown in Figure 1 and was published in the Journal of Medicinal Chemistry.
Although I continue to work on projects involving opioids and other
drugs of abuse, my lab has become more involved in cancer research. Our
transition into the design of anticancer agents happened somewhat by
chance. We had synthesized a series of constrained analogs of a highly
potent delta opioid antagonist with a diaryl amino core structure.
Interestingly, the heterocycles we developed never showed the desired
potency as analgesics, but did show good activity when cross screened
for antiviral and anticancer activity.
While it took several years to
complete, we have successfully described a small, diverse chemical
library with promising activity against a variety of targets. The
screening of this library led to the discovery of the first small
molecule lead compounds with promising activity against the West Nile
Virus as well as a new set of topoisomerase inhibitors with a
NMR derived structucture of aminoacridines bound to quadraplex DNA. From: Ferreira, R.; Artali, R.; Benoit, A.; Gargallo, R.; Eritja, R.; Ferguson, D. M.: Sham, Y.; Mazzini, S. Structure and Stability of Human Telomeric G-Quadruplex with Preclinical 9-Amino Acridines. PLoS ONE 8 (3): e57701, 2013
My lab has further shown the latter function as catalytic inhibitors of topo activity (not poisons) and block topo association with DNA by intercalation. The compounds have been found to be active in both in vitro and in vivo anticancer assays and showed excellent efficacy in an mouse glioblastoma model following oral administration. This project is particularly interesting to us since we have a long standing history in the simulation and analyses of the structural properties of DNA complexes. In fact, we applied this expertise in concert with DNA binding studies and high field NMR work to build a structural model that explains the molecular basis to catalytic inhibition of topo II.
Our most recent work is perhaps the most exciting. As part of our
pre-clinical work on treating gliobastoma with topoisomerase inhibitors,
we were asked if it would be possible to synthesize a number of
Toll-like receptor (TLR) agonists for the development of a cancer
vaccine. Clinical trials have shown that patients receiving combination
therapies including vaccines based on tumor cells or lysates showed
better outcomes than those receiving chemotherapy alone.
of Minnesota is a leader in the field of autologous cancer cell-based
immunotherapy and has completed clinical trials for treating
glioblastoma in humans and several canine meningioma trials. Autologous
cancer cell vaccines use the patient’s own tumor cells as the antigen
which is formulated as a cell lysate or apoptotic bodies as an
One of the primary challenges to cancer vaccination is the
rapid development of tolerance and suppression of tumor specific
cytotoxic T cell function. The key to defeating tolerance are the
Toll-like receptors. TLR ligands, such as the TLR-7 agonist imiquimod,
stimulate the immune response and are capable of increasing the
immunogenicity of antigen presenting cells (APCs) by several orders of
magnitude. TLR activation triggers the NF-kappaB mediated transcription
of cytokines and chemokines, leading to a robust response in the
generation of antigen specific T cells (both CD8+ and CD4+ cells).
lab has shown that more potent TLR adjuvants can be created by
co-stimulation of TLR-7 and -8. This is not surprising since the
“natural” ligand for both these subtypes is RNA (derived from viral
pathogens). Based on the imidazoquinoline scaffold of imiquimod, our lab
developed a series of highly substituted analogs that show a clear SAR
in producing cytokines and triggering TLR-7 and -8. We have also begun
to establish rules for selectivity of these ligands for TLR-7 and -8 and
published seminal work relating structure to function in generating
cytokines that are critical to an antigen specific immune response.
Our lead compound 528 has entered into canine clinical trials for
treating meningioma. This project is a partnership between my lab, Liz
Pluhar’s group in the veterinary school, and Mike Olin’s lab in
The first dog treated was batman and he remained tumor free
until he died of natural causes. See a video of Batman.
We now have treated over 100 dogs with autologous tumor cell vaccines
and offer the technology to clinics across the country through a program
at the University of Minnesota.
As part of the partnership, my lab
takes part in monthly brain tumor meetings to review current cases and
discuss changes in protocols or formulations as dictated by the
outcomes. My group is responsible for the synthesis and formulation of
the adjuvant and work closely with the clinical team to improve the
efficacy and safety of the vaccine.
Our adjuvants are also part of a nanoparticle study initiated in
collaboration with Jayanth Panyam in Pharamceutics for treating
melanoma. We are pre-loading nanoparticles with drug to create a time
release formulation for use in vaccination. Nanoparticles can be used
to target the adjuvant to specific cell types and organs adding a new
dimension to the vaccination protocol. The system can also be used to
co-deliver drugs or specific peptide antigens.
Our lab focuses on optimization of the loading process through chemical modification of the adjuvant. We balance the lipophilicity of the compound with the potency in triggerring TLR-7/8 and cytokine induction. This approach applies SAR, synthesis, and logP measurements to identify optimal candidates to evaluate for loading efficiency.