Protein-protein interactions (PPI), which are the ultimate determinants of the function of all proteins, can rarely be modulated by small molecules because the corresponding protein interfaces do not have adequate binding pockets. Recently, an intriguing alternative has been recognized for constitutively multimeric proteins such as those in the important TNF superfamily (TNFSF) via an allosteric mechanism that distorts one of the binding partners. Since we have recently identified the first small-molecule inhibitors of the CD40?CD154 costimulatory interaction, which is a member of this family, we propose to exploit the possible advantages that can be derived from such a mechanism and (1) confirm the feasibility of an allosteric, trimer-distorting mechanism in interfering with the CD40?CD154 costimulatory proteinprotein interaction, a member of the TNFSF that plays an important role in the activation of immune responses, (2) use this information and design improved small-molecule inhibitors suitable for therapeutic applications and to confirm the immunosuppressive activity of the most promising inhibitors, and (3) investigate whether similar mechanism can be found for other members of the TNF superfamily (in particular, OX40?OX40L, BAFF-R?BAFF, RANK?RANKL, 4-1BB?4- 1BBL) and whether it can be used to identify specific inhibitors. TNFSF costimulatory interactions play key roles in the development of effective immune responses, but until relatively recently, they, just as most other PPIs, were considered ?undruggable?. It has now been suggested that such inhibitions for CD40?CD154 and other members of the TNFSF family might occur via a unique allosteric mechanism whereby the disruptor molecule intercalates not between the receptorligand interface, but between monomeric units of the trimeric ligand (or receptor). This can allow more efficient binding making these interactions particularly targetable by small molecule. Whereas ?drug-like? chemical libraries commonly used for high-throughput screening are now recognized to not be well-suited for PPI inhibition, the chemical space of our inhibitors can allow quick exploration of this novel mechanism for constitutively homotrimeric cytokines, and can lead to novel pharmacological tools and new innovative drugs for the many disease areas where TNF superfamily interactions are involved. Development of a detailed mechanistic understanding of the small-molecule inhibition of CD40?CD154 and possibly other receptor-ligand pairs of the TNF superfamily can lead to the development of novel, clinically feasible approaches addressing therapeutic needs arising from dysregulated functions of costimulatory molecules in T-, B-, and APC cells such as autoimmune diseases and transplant rejection. Accordingly, the proposed work should lead to the elucidation of an intriguing new mechanism that can make possible small-molecule costimulatory blockade as well as to novel pharmacological tools and new innovative drugs for a number of disease areas where TNF superfamily interactions are involved. Because of its unique combination of expertise in small molecule pharmacology, medicinal chemistry, molecular biology, cell transplant, and immunobiology, we believe that our team is very well positioned to achieve considerable progress along these lines.

Public Health Relevance

Activation of effective immune responses requires so-called costimulatory interactions between the corresponding cells. Here, we propose to elucidate and exploit a recently identified new mechanism that, contrary to previous expectations, might allow blockade of these interactions with traditional small-molecule drugs. This can lead to have clear therapeutic applications for transplant rejection as well as for autoimmune diseases such as type 1 diabetes, systemic lupus erythematous (SLE), or multiple sclerosis (MS).

National Institute of Health (NIH)
National Institute of Allergy and Infectious Diseases (NIAID)
Research Project (R01)
Project #
Application #
Study Section
Special Emphasis Panel (ZRG1-IMM-M (08))
Program Officer
Lapham, Cheryl K
Project Start
Project End
Budget Start
Budget End
Support Year
Fiscal Year
Total Cost
Indirect Cost
University of Miami School of Medicine
Schools of Medicine
Coral Gables
United States
Zip Code
Bojadzic, Damir; Buchwald, Peter (2018) Toward Small-Molecule Inhibition of Protein-Protein Interactions: General Aspects and Recent Progress in Targeting Costimulatory and Coinhibitory (Immune Checkpoint) Interactions. Curr Top Med Chem 18:674-699
Bojadzic, Damir; Chen, Jinshui; Alcazar, Oscar et al. (2018) Design, Synthesis, and Evaluation of Novel Immunomodulatory Small Molecules Targeting the CD40?CD154 Costimulatory Protein-Protein Interaction. Molecules 23:
Bahnan, Wael; Boucher, Justin C; Gayle, Petoria et al. (2018) The eIF2? Kinase Heme-Regulated Inhibitor Protects the Host from Infection by Regulating Intracellular Pathogen Trafficking. Infect Immun 86:
Mohan, Teena; Berman, Zachary; Luo, Yuan et al. (2017) Chimeric virus-like particles containing influenza HA antigen and GPI-CCL28 induce long-lasting mucosal immunity against H3N2 viruses. Sci Rep 7:40226
Chen, Jinshui; Song, Yun; Bojadzic, Damir et al. (2017) Small-Molecule Inhibitors of the CD40-CD40L Costimulatory Protein-Protein Interaction. J Med Chem 60:8906-8922
Buchwald, Peter (2017) A three-parameter two-state model of receptor function that incorporates affinity, efficacy, and signal amplification. Pharmacol Res Perspect 5:e00311
Cechin, Sirlene R; Lopez-Ocejo, Omar; Karpinsky-Semper, Darla et al. (2015) Biphasic decline of ?-cell function with age in euglycemic nonobese diabetic mice parallels diabetes onset. IUBMB Life 67:634-44
Song, Yun; Buchwald, Peter (2015) TNF superfamily protein-protein interactions: feasibility of small- molecule modulation. Curr Drug Targets 16:393-408
Cechin, Sirlene R; Buchwald, Peter (2014) Effects of representative glucocorticoids on TNF?- and CD40L-induced NF-?B activation in sensor cells. Steroids 85:36-43
Song, Yun; Margolles-Clark, Emilio; Bayer, Allison et al. (2014) Small-molecule modulators of the OX40-OX40 ligand co-stimulatory protein-protein interaction. Br J Pharmacol 171:4955-69

Showing the most recent 10 out of 11 publications