Brief Summary: The purpose of this study is to determine whether doxycycline is effective in the treatment of relapsed Non Hodgkin Lymphomas (NHL).

Detailed Description: The long-term objective of this proposal is to develop more effective and less toxic therapeutic approaches for relapsed and refractory Non Hodgkin Lymphomas (NHL). Given the incurability of indolent lymphomas, innovative strategies for treatment are needed. For aggressive lymphomas such as Diffuse Large B Cell Lymphoma (DLBCL), novel treatments are particularly relevant since one third of patients have disease that will relapse or is refractory to standard therapy. Outcomes for this remaining group of patients are very poor. To address this unmet need, we have identified the antimicrobial agent doxycycline as a novel drug repurposed for lymphoma treatment based on results from a small molecule screen against Diffuse Large B Cell Lymphoma (DLBCL). Through preclinical work in his laboratory, my basic science collaborator Dr. Jiyong Zhao has found that doxycycline inhibits proliferation and survival in both activated B cell (ABC) type and germinal center B (GCB) type Diffuse Large B Cell Lymphoma (DLBCL) cell lines, as well as in Burkitt lymphoma (BL) and follicular lymphoma (FL) cell lines. Based on this preliminary data, we propose an open label, single center phase II study of doxycycline in patients with relapsed Non Hodgkin Lymphomas (NHL). We have selected a dose and schedule (200 mg BID by mouth daily) based on maximum antimicrobial dose use, and acceptance of tolerability in several studies. The planned correlative studies should help to identify potential biomarkers for response to doxycycline, such as plasma matrix metalloproteinase 9 (MMP9), and provide further insight into potential mechanisms of doxycyline action hypothesized from results of prior laboratory studies.