The US Food and Drug Administration (FDA) has cleared Immune-Onc Therapeutics to start a Phase I clinical trial of its myeloid checkpoint inhibitor in solid tumor patients.
Immune-Onc’s candidate, IO-202, is an antibody that targets leukocyte immunoglobulin-like receptor B4 (LILRB4), a receptor expressed on dendritic cells and other monocytic myeloid cells. Researchers have linked upregulation of LILRB4 by dendritic cells, as is seen in many solid tumor types, to the generation of antigen-specific T regulatory cells and induction of immunosuppression in cancer.
A Phase I clinical trial of IO-202 in patients with relapsed/refractory acute myeloid leukemia and chronic myelomonocytic leukemia got underway in 2020. With the FDA clearing Immune-Onc to start a second study in solid tumor patients, the biotech plans to build on the earlier trial to accelerate its progress.
“Since we have an ongoing Phase I of IO-202 in blood cancer, we are able to leverage the safe doses tested in blood cancers to start with a higher initial dose in solid tumors,” said Charlene Liao, CEO of Immune-Onc. “We have limited steps in dose escalation for monotherapy and combination with pembrolizumab, an anti-PD-1 antibody. Our protocol also includes expansion cohorts in specific tumor types. We expect to initiate the phase 1b trial in 1H2022, and complete dose escalation in 2022.”
The combination with pembrolizumab, sold by Merck as Keytruda, is part of a push to establish IO-202 as a drug capable of enhancing the effects of the blockbuster PD-1/L1 checkpoint inhibitors that dominate the immuno-oncology landscape today.
Merck’s in-house researchers have looked at the concept of targeting LILRB4, publishing a paper in 2020 that concluded the mechanism “may be useful to reverse the immunosuppressive function of [monocytic myeloid-derived suppressor cells] and enhance the efficacy of immune checkpoint inhibitors.” Liao set out the rationale for the combination.
“We see myeloid checkpoints as significant contributors to primary and second immune resistance to T-cell checkpoint inhibitors such as anti-PD-1 or anti-PD-L1 for cancer treatment,” Liao said. “Since myeloid cells play crucial roles in regulating T cells, there is strong synergy in targeting myeloid checkpoint and T-cell checkpoints simultaneously. That's why we want to combine our first-in-class myeloid checkpoint inhibitor IO-202 with an anti-PD-1.”
NGM Biopharmaceuticals also is working on an antibody against LILRB4, also known as ILT3, that has just entered clinical trials. With a Phase I/I trial of NGM’s NGM831, as a monotherapy and in combination with Keytruda, in solid tumor patients expected to start this month, Immune-Onc has a close rival for the LILRB4 opportunity.