FLX Bio has boosted its cash supplies with a new $60 million series C round as it starts dosing for its new cancer test.
South San Francisco, California-based FLX emerged from Bristol-Myers Squibb’s $800 million takeover of Flexus Biosciences, with a pipeline of prospects the Big Pharma decided it could live without.
It now has the cash and the early data to push on with phase 1 tests, just started, for its oral CCR4 inhibitor FLX475. This drug focuses on a key pathway by which tumors recruit regulatory T cells to suppress tumor immunity. By blocking this pathway with a CCR4 antagonist, the biotech is betting that it can prevent regulatory T cell recruitment to the tumor site, reduce the number of regulatory T cells in the tumor and importantly, enable immune activation and tumor killing. The biotech also sees FLX475 as having the potential to boost cell-based immunotherapies, such as CAR-T and cancer vaccines, which could lead to combos in the future.
The company adds that it’s also now looking to pick out another clinical candidate next year, this time targeting ubiquitin specific protease 7 (USP7), as well as working on its GCN2 program. USP7 plays a key role in two cancer pathways: it promotes the formation and function of regulatory T cells by deubiquitinating and stabilizing FOXP3; and it maintains low levels of p53, a prevalent tumor suppressor protein (and the focus of several other early-stage biotechs), thereby allowing the tumor to grow unchecked.
GCN2, meanwhile, is a myeloid-derived suppressor cell target that works downstream of IDO and arginase. GCN2 inhibition has the potential for superior efficacy, as it can reverse immune suppression caused by depletion of both tryptophan and arginine.
All three programs represent “differentiated and important mechanisms to stimulate an immune response within the tumor microenvironment,” the company said in a statement.
The $60 million swag comes from new investments out of Google’s venture arm GV and other “undisclosed investors,” as well as existing investors including The Column Group, Kleiner Perkins, Topspin Partners and Celgene. It got a $50 million series B back in April last year.
“With a discerning syndicate of investors committed to our science, our strategy and our team, we look forward to using the proceeds of this series C financing to advance our robust pipeline of small molecule immuno-oncology compounds focused on regulatory T cell and tumor myeloid cell modulation,” said Brian Wong, M.D., Ph.D., president and CEO.
FLX475 hits the clinic on the strength of preclinical data presented by FLX earlier this year. Those results showed that FLX’s CCR4 antagonists block the migration of regulatory T cells—in the tumor but not in peripheral tissues—and aid the expansion of activated effector T cells. Adding the CCR4 antagonist to anti-PD-L1 and anti-CD137 antibodies dialed up the tumor-killing effects of these drugs.
FLX lists the CCR4 antagonist program as the most advanced in its pipeline, despite having started life with a FLT3 and CDK4/6 inhibitor that was already in phase 1. Flexus moved that drug, FLX925, into the clinic just before being bought by Bristol-Myers. FLX925 has since disappeared from FLX’s pipeline, although a phase 1/1b dose-escalation trial is listed as ongoing on ClinicalTrials.gov.