Small Molecule Therapeutics Vorinostat Downregulates CD30 and Decreases Brentuximab Vedotin Efficacy in Human Lymphocytes

With an increasing number of clinical trials looking at combination therapies in cancer, potential drug–drug interactions require particular attention. One such instance is the treatment of CD30þ tumors after previous vorinostat (SAHA; suberoylanilide hydroxyamic acid) failure with the anti-CD30 antibody–drug conjugate brentuximab vedotin. Using B-, T-, and natural killer (NK)–cell lines in vitro, we demonstrate that SAHA downregulates the expression of CD30 and lowers the efficacy of subsequent brentuximab vedotin treatment if baseline CD30 levels are reduced by 50% or more. Interestingly, low-dose SAHA treatment that maintained 50% or more of basal CD30 expression followed by subsequent treatment with brentuximab vedotin led to enhanced antitumor activity. The downregulation of CD30 was short lived upon SAHA removal, suggesting that allowing SAHAwashout may circumvent any interactions with subsequent drug therapies. Our findings confirm the requirement of CD30 for brentuximab vedotin efficacy and suggest that combination treatment with SAHA in CD30 tumors may decrease efficacy. Combination treatment in highly CD30þ tumors, however, increases efficacy andwarrants further consideration as a new treatment paradigm.Mol Cancer Ther; 13(12); 2784–92. 2014 AACR.