IDO/TDO Screening Services

BPS offers biochemical and cell-based IDO/TDO screening services which can effectively accelerate your research and drug discovery programs. With all screening and profiling services, we provide a comprehensive (>10 page) report with both raw and analyzed data, graphs, detailed protocols, etc. Trust us to provide you with high quality data with fast turnaround time. Our team of experts along with our broad services portfolio makes it easy to:

  • Screen for inhibitors/targets using our IDO1 assay
  • Select from IC50 determination and single point concentrations
  • Receive data within days of compound submission
  • Perform follow-up studies using the same soluble receptors manufactured in-house
  • Get questions answered or project guidance in a time-efficient manner

Contact BPS today to find out more about how we can assist you in your IDO1 related research.

Biochemical Assay Format: 

IDO Cell-Based Assay Format: The IDO1 Cell-Based Screening service is designed to measure IDO1 enzyme inhibition. Stable, recombinant HEK293 cells expressing tetracycline-inducible human IDO1 are treated with test inhibitors and IDO1 activity is detected by measuring Kyn levels in the cell culture medium. Alternatively, HeLa cells treated with IFN-γ to induce IDO1 expression or the ovarian cancer cell line, SK-OV-3, which overexpresses IDO1, can be used. 

TDO Cell-Based Assay Format: The TDO Cell-Based Screening service is designed to measure TDO enzyme inhibition. Stable, recombinant HEK293 cells overexpressing TDO are treated with test compound and TDO activity is detected by measuring Kyn levels in the cell culture medium. 


Tryptophan (Trp or L-Trp) is an important and essential amino acid that has a variety of functions within the cell. In addition to being incorporated into the polypeptide chain of proteins, various catabolic pathways can produce a number of functional Trp derivatives. In the context of a tumor, Trp catabolizing enzymes have been shown to assist cancer cells in immune evasion.  Cancer cells use indoleamine 2,3-dioxygenases (IDO1 and IDO2) and tryptophan 2,3-dioxygenase (TDO), enzymes that catalyze the first and rate limiting step of the kynurenine (Kyn) Trp degradation pathway to suppress the host’s immune response in a number of different ways.

First, there is less tryptophan available for immune cells to utilize. As a result, immune cells are starved of an essential amino acid that is necessary for protein synthesis. Additionally, when tryptophan is converted into kyn, it can be transported into immune cells and have immunosuppressive functions. When kyn is transported into immune cells, the immune system is weakened and cancer cells have the ability to spread and proliferate. Many types of cancers such as pancreatic, ovarian, lung, brain and cervical, are thought to utilize IDO or TDO upregulation as a means of immune evasion. Due to its widespread clinical relevance, these enzymes are important immunotherapy targets and provide researchers a new means of regulating cancer cell death. 

When IDO1 is upregulated in cancer cells, Trp is converted into Kyn and this effects a plethora of immune cell types, ultimately dampening the inflammatory immune response through various mechanisms.

To help you advance your immunotherapy related research, BPS offers a variety of Tryptophan-related Assay Kits including

Not quite what you're looking for? We also offer custom assays for several other immunotherapy targets. Our Custom Assay Development Services allow for flexibility to meet your specific research needs