Antigen-Specific antitumor responses induced by OX40 agonist are enhanced by the ido inhibitor indoximod

Zuzana Berrong, Mikayel Mkrtichyan, Shamim Ahmad, Mason Webb, Eslam Mohamed, Grigori Okoev, Adelaida Matevosyan, Rajeev Kumar Shrimali, Rasha Abu Eid, Scott Hammond, John Edward Janik, Samir N. Khleif

Research output: Contribution to journalArticlepeer-review

12 Scopus citations


Although an immune response to tumors may be generated using vaccines, so far, this approach has only shown minimal clinical success. This is attributed to the tendency of cancer to escape immune surveillance via multiple immune suppressive mechanisms. Successful cancer immunotherapy requires targeting these inhibitory mechanisms along with enhancement of antigen-specific immune responses to promote sustained tumor-specific immunity. Here, we evaluated the effect of indoximod, an inhibitor of the immunosuppressive indoleamine-(2,3)-dioxygenase (IDO) pathway, on antitumor efficacy of anti-OX40 agonist in the context of vaccine in the IDO TC-1 tumor model. We demonstrate that although the addition of anti-OX40 to the vaccine moderately enhances therapeutic efficacy, incorporation of indoximod into this treatment leads to enhanced tumor regression and cure of established tumors in 60% of treated mice. We show that the mechanisms by which the IDO inhibitor leads to this therapeutic potency include (i) an increment of vaccine-induced tumor-infiltrating effector T cells that is facilitated by anti-OX40 and (ii) a decrease of IDO enzyme activity produced by nontumor cells within the tumor microenvironment that results in enhancement of the specificity and the functionality of vaccine-induced effector T cells. Our findings suggest a translatable strategy to enhance the overall efficacy of cancer immunotherapy.

Original languageEnglish (US)
Pages (from-to)201-208
Number of pages8
JournalCancer Immunology Research
Issue number2
StatePublished - Feb 2018

ASJC Scopus subject areas

  • Medicine(all)


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