e14547 Background: Thromboembolic events (TEEs) occur in approximately 10–15% of advanced cancer patients. Risk factors include cancer therapy and extent and type of malignancy. Vorinostat, a histone deacetylase inhibitor, has been licensed in the USA for the treatment of cutaneous manifestations in patients with cutaneous T-cell lymphoma (CTCL) who have progressive, persistent, or recurrent disease on or following two systemic therapies. TEEs were observed in 6/86 patients (7.0%) enrolled in vorinostat CTCL clinical trials at licensure. To gain further insight into the association between TEEs and vorinostat treatment, we analyzed data from vorinostat clinical trials and post-marketing surveillance (PMS) reports. Methods: Serious adverse events (SAEs) reported through November 3, 2008, among patients receiving vorinostat in completed and ongoing clinical trials, PMS reports, and published literature were reviewed for terms consistent with TEEs. A committee of independent (non-Merck employees) academic experts evaluated these reports. Although no safety signals were observed, the committee recommended that d-dimer and/or plasmin-antiplasmin assays should be conducted. This recommendation has been implemented in three ongoing studies ( NCT00486720 , NCT00632931 , NCT006429542) and will provide further information on clotting parameters among patients being treated with vorinostat. Results: During the reporting period, data from >1,845 cancer patients who received vorinostat were reviewed. Irrespective of causality, 107 patients (<5.8%) reported TEE SAEs (Table). Of these, 47 (<2.6%) had TEE SAEs that were rated as related to vorinostat, four of which were fatal. As of the data cut off, review of the special assays in the three studies did not result in any conclusive correlation. Conclusions: The incidence rate of TEEs observed in vorinostat studies is similar to reported rates of TEEs for advanced cancer patients. [Table: see text] [Table: see text]