Significant Activity Of The mTOR Inhibitor Sirolimus and HDAC Inhibitor Vorinostat In Heavily Pretreated Refractory Hodgkin Lymphoma Patients

Background Preclinical models have suggested that HDAC and mTOR inhibitors have synergistic antineoplastic activity in Hodgkin lymphoma and other cancers by reducing the activity of AKT, mTOR and HDAC. Methods We designed a phase I study to determine the safety of the mTOR inhibitor sirolimus (1mg-5mg PO daily q 28 days) and HDAC inhibitor vorinostat (100mg-400mg PO daily q 28 days) in advanced cancers with an expansion cohort at the recommended phase 2 dose (RP2D) of sirolimus 4mg and vorinostat 300mg for patients with refractory classical Hodgkin lymphoma. The expansion cohort included optional pre- and post-treatment tumor biopsies, peripheral blood mononuclear cells (PBMCs), plasma/serum collections for pharmacodynamic (PD) and pharmacokinetic (PK) endpoints. Results A total of 16 patients (men, n=8; women, n=8), median age 33 years, median of 6.5 prior therapies (including autologous SCT [n=15], autologous and allogeneic SCT [n=4]) were enrolled in dose escalation (n=1) or RP2D (n=15) cohorts. At the median follow-up of 3.2 months, 15 (94%) patients demonstrated decreased FDG uptake including 2 CRs (13%) and 5 PRs (31%) using CHESON criteria, with a total CR+PR rate of 44%. The median reduction of tumor was -27% (-100% to +20%, [Figure][1]). The estimated median time-to-treatment failure has not been reached and 63% of the patients continued on therapy with further improvement in their level of disease response. Major grade 3-4 treatment-related toxicities included grade 3 thrombocytopenia (4 patients, 25%), grade 4 thrombocytopenia (6, 38%), grade 3 anemia (1, 6%), febrile neutropenia (1, 6%) and led to treatment interruptions and/or dose modifications in 10 (63%) patients. Five (31%) patients had archival tissue available for targeted next-generation sequencing and one patient had a loss of TSC2 , an abnormality that putatively activates mTOR. This patient has had a continuing response to therapy (-56%) for 8.4+ months. PD studies in pre- and post-treatment tumor biopsies, PBMCs and plasma as well as PK analysis continue. Conclusion The combination of sirolimus and vorinostat is well tolerated with encouraging activity in very heavily pretreated patients with Hodgkin lymphoma refractory to standard therapies. Enrollment continues. ![Figure][2] Disclosures: Off Label Use: sirolimus - mTOR inhibitor vorinostat - HDAC inhibitor. [1]: #F1 [2]: pending:yes