The addition of NewLink Genetics Corp.'s investigational therapy indoximod to therapy with Merck & Co. Inc.'s Keytruda improved the response rate of advanced melanoma patients, according to phase 2 clinical trial results presented April 4 at the American Association of Cancer Research conference in Washington, D.C.
Despite the improvement, investors were not impressed by the data. NewLink Genetics' shares opened the April 4 session down 25%, but have since recovered somewhat and are down 11% as of midday.
The overall response rate, including partial and complete reductions in tumor size, was 52%, compared to 33% among advanced melanoma patients in the clinical trial that resulted in approval of Keytruda. The company presented new data at the conference on the outcomes for trial patients from as recently as January 2017. After a median follow-up of 10.5 months, six of 60 patients saw all signs of cancer disappear, while 25% had a partial response, according to an April 4 release.
Investigator Yousef Zakharia of the University of Iowa said in a release that the rate is 59% when ocular melanoma patients are excluded. Ocular melanoma is less responsive than other types of melanomas; patients with that type of disease have been excluded from similar trials, he said.
Indoximod belongs to class of immunotherapies called IDO inhibitors, which block a pathway that slows down the body's natural immune response to cancer. The activity at the cancer conference makes clear that the field is an active one within the oncology arena due to the advent of combination therapies.
Rival Incyte Corp. revealed April 2 that it is making progress on its partnership with Bristol-Myers Squibb Co. to develop its IDO inhibitor for use in combination with the immunotherapy drug Opdivo. The news comes on the heels of Incyte's March 31 announcement that its collaboration with Merck has been expanded to include seven phase 3 trials of combination therapy with the immunotherapy drug Keytruda.
In addition, Bristol-Myers presented early stage trials results of its internal IDO inhibitor candidate at the conference and said in its abstract that the data support further evaluation of the compound in combination with Opdivo.
The IDO inhibition programs of Bristol-Myers and Merck are furthest along, Morgan Stanley equity analyst David Risinger wrote in a March 17 research note. AstraZeneca PLC is testing Incyte's candidate in early stage combination therapy trials, while Roche Holding Ltd. is working with NewLink. Pfizer Inc. plans to begin IDO inhibition combination therapy trials in the second half of this year.