PD-1 (programmed cell death-1) is a receptor expressed on activated T cells and - when bound to ligands PD-L1 or PD-L2 has been shown to down-regulate immune responses. It is known that many cancer cells expressed PD-L1 and PD-L2 and this helps them evade destruction by the immune system.
There are already three 'checkpoint inhibitor' drugs on the market which target the pathway - Merck & Co's Keytruda (pembrolizumab), Bristol-Myers Squibb's Opdivo (nivolumab) and Roche's Tecentriq (atezolizumab) - and there are several other candidates in trials including AstraZeneca's durvalumab and Pfizer/Merck KGaA avelumab.
AMSBIO says the two new cell lines will help companies discover and develop new compounds that target the PD-1/PD-L1 pathway. The first is a PD-1/NFAT Reporter - Jurkat cell line that can be used to screen for activators or inhibitors of PD-1 signalling as well as for studying the biological activity of PD-1 and its interactions with ligands.
An accompanying TCR activator/PD-L1 - Chinese hamster ovary (CHO) cell line can also be used for screening for activators or inhibitors of PD-1 signalling, as well as screening PD-L1 antibodies for their binding affinity to the receptor.
"Activation of the immune system involves a number of checkpoints in order to ensure proper activation," said ASMBIO.
"Given its diverse function and the fact that the immune system plays a role in virtually all human diseases, immunotherapy has become an important approach for the treatment of numerous diseases," it added, noting that PD-1 and PD-L1 may also be potential targets in multiple sclerosis, arthritis, lupus, and type I diabetes.
Collectively, the PD-1/PD-L1 inhibitors and drugs targeting other immune checkpoints such as CTLA-4 have been tipped by market research firm Visiongain to grow into a therapeutic category worth $16.5bn or more by 2020 in cancer alone, thanks to exceptional, durable efficacy across a number of tumour types.
The PD-1/PD-L1 inhibitors are predicted to account for the bulk of that market, it said.