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Abstract 2816 Background: Vorinostat is a histone deacetylase inhibitor with activity in lymphoma and leukemia. Vorinostat has been reported to act synergistically with topoisomeraseII inhibitors such as anthracyclines (Ac) by facilitating an open chromatin configuration thus enhancing double-strand DNA breaks and apoptosis. We conducted a phase 1 study of escalating doses of vorinostat with pegylated liposomal doxorubicin (V+PLD) in patients with relapsed or refractory lymphoma. The primary objective was to determine the maximum tolerated dose (MTD). Other endpoints included safety, tolerability, and activity of V+PLD. Methods: Patients age ≥18 years with relapsed or refractory lymphoma were enrolled sequentially into 1 of 3 dosing levels using a standard 3+3 design for up to 8 cycles. The study was conducted in accordance with the Declaration of Helsinki, good clinical practice and regulatory guidelines. Vorinostat 200 (dose level 1), 300 (dose level 2), or 400mg (dose level 3) twice daily on days 1–7 and PLD 30mg/m2 on day 3 of a 21-day cycle were administered to eligible and consenting patients. CTCAE v.3.0 was used to determine toxicities, and the revised criteria for malignant lymphoma were used to determine response. Results: 14 patients have been enrolled; 2 men and 12 women; median age 69 years [range 27–88]; median prior therapies (4) [1-11]; prior Ac (13); median prior Ac dose (300mg/m2) [108-440mg/m2]; prior HDACi (1); Dose level 1 (7); Dose level 2 (4); Dose level 3 (3). Lymphoma subtypes included: Hodgkin's lymphoma (HL)(4), peripheral T-cell lymphoma (3), diffuse large B-cell lymphoma (DLBCL)(5), grey zone lymphoma (1), lymphoplasmacytic lymphoma (1). Median number of study cycles was two [1-8](2). Grade 3–4 hematologic toxicities included: neutropenia (3) and thrombocytopenia (1). Grade 3–4 non-hematologic toxicities included: fatigue (2), nausea (1), anorexia (1), dehydration (1), AST/ALT elevation (1), amylase/lipase elevation (1). No cardiac toxicities were observed. There was one death attributed to disease progression. Partial responses (PR) were documented in two HL patients, stable disease (SD) in one HL and one DLBCL patient. Three patients continued therapy beyond 2 cycles. One HL patient with a PR tolerated 8 cycles despite a prior anthracycline dose of 350mg/m2 and 9 prior systemic treatments including ABVD, ICE, GND, DICEP, BEAM and autologous stem cell transplant, Gem and C-MOPP. Another HL patient with a PR after 2 cycles is currently on cycle 3 at dose level 3 and had 5 prior treatments including autologous transplant. One other HL patient with SD discontinued therapy after 2 cycles to proceed with alternative chemotherapy including allogeneic stem cell transplant. One patient with cutaneous DLBCL obtained a skin response but had overall stable disease and completed 6 cycles before disease progression; prior treatment included R-CHOP, R-ICE, CEPP, and GemOx. In addition, one patient with lymphoplasmacytic lymphoma had a clinical response after 1 cycle but therapy was discontinued because of neutropenia and her disease progressed. Conclusions: The combination of V+PLD is well tolerated even among older and heavily pretreated patients. There were no cardiac toxicities even in patients heavily pretreated with anthracyclines. The MTD has not been reached and enrollment to dose level 3 is ongoing. Disease control was achieved in 4 of 14 patients (2 PR and 2 SD). Of interest, 3 of 4 patients with HL achieved disease control (2 PR and one SD), and treatment with vorinostat in combination with anthracycline-based therapy warrants further investigation in HL. Disclosures: Lansigan: Merck: Speakers Bureau. Off Label Use: Vorinostat in combination with pegylated doxorubicin is considered experimental in lymphoma. Foss:Merck: Speakers Bureau.