Shares in Incyte have leaped after the company reported positive results for its epacadostat—vying to be the first-in-class IDO1 inhibitor—alongside Merck's PD-1 blocker Keytruda.
The first look at data from the mid-stage study, which will be presented in full next month at the annual ASCO meeting in Chicago, makes for encouraging reading and bodes well for the prospects of inhibitors of IDO, which like PD-1 is a pathway used by tumors to escape detection by T cells.
The top-line message from the ASCO abstracts is that adding epacadostat to Keytruda in the ECHO-202 trial boosted the overall response rate (ORR) in a range of solid tumor types, compared to historical data for Keytruda used on its own.
For non-small cell lung cancer and bladder cancer, the combo achieved an ORR of 35%, all of which were partial responses. In head and neck cancer and renal cancer patients, the combo managed a 31% and 30% response rate, respectively, with three patients showing complete clearance of their tumors. Prior studies have suggested with Keytruda as a monotherapy ORR rates were 20% or less in these cancers.
The results "demonstrate encouraging clinical activity, both within and across tumor types, which compares favorably to contemporary data in the second-line setting," commented Steven Stein, M.D., Incyte's chief medical officer.
Incyte has already pushed epacadostat into phase 3 testing alongside Keytruda for all four tumor types, and reckons the combination of IDO1 and PD-1 blockade could be a cornerstone in immuno-oncology therapy, especially as the two drugs seemed to be well tolerated.
The biotech has not stayed faithful to Merck in that regard, however, signing a deal earlier this year with its archrival in the PD-1 inhibitor space, Bristol-Myers Squibb, to test epacadostat alongside its Opdivo product.
The potential to overcome the obstacle that PD-1/PD-L1 inhibitors only work in about a third of patients as a monotherapy—which remains a big unanswered question in cancer immunotherapy—is making IDO inhibition a particularly hot prospect in the field. Incyte is capitalizing on its lead in the space, although BMS, Roche and Pfizer all have IDO candidates in early-stage testing.
The ASCO data are a welcome boost for Incyte after the FDA decided not to approve its Eli Lilly-partnered rheumatoid arthritis drug baricitinib last month. That setback wiped out 10% of the company's share price and also followed a series of clinical trial failures in 2015 and 2016 for its JAK inhibitor Jakafi (ruxolitinib)—sold for myelofibrosis and polycythemia vera—as well as INCB39110, another drug in the JAK class.