Transfer of the Multidrug Resistance Gene, MDR-1, to Hematopoietic Progenitors from a Patient with Transformed Large Cell Lymphoma, and Demonstration of In Vivo Chemotherapy Protection with Dose Escalating Chemotherapy.

We report results for the first patient enrolled in a gene therapy clinical trial (RAC and FDA approved) for poor risk non-Hodgkin’s lymphoma. The retroviral vector, SF1m (Hildinger et al ’98,’99), consists of the LTRs of SFFV, the leader sequence of MESV, and the full length MDR-1 cDNA. The first subject enrolled on this trial had follicular transformed large cell lymphoma that relapsed with a large mediastinal mass and superior vena cava syndrome two and a half years after initial therapy. After 3 cycles of salvage chemotherapy with RICE, a residual 4 cm mediastinal mass persisted that was gallium avid, and B symptoms recurred by 3 weeks. With informed consent, the patient underwent mobilization with rituximab, cyclophosphamide, and G-CSF. A total of 3 X 10⁶ CD34+ cells/kg were cryopreserved without further manipulation. An additional apheresis product was subjected to CD34 selection on the Isolex 300i. The purified product was 96% CD34+, represented 3.17 X 10⁶ CD34+ cells/kg, 98% yield with 99% viability. These cells were pre-incubated for 17h with 20 ng/ml IL-3, and 100 ng/ml each of IL-6, SCF and TPO, and then transduced with three changes of retrovirus SF1m in fibronectin CH-296 peptide (Retronectin)-coated gas permeable bags (X-fold), alternately 7–9 hours with virus, followed by 6–11 hours in media with cytokines, and a final centrifugation. The final product was 95% CD34+, with 96% viability, and represented 5.5 X 10⁶ CD34+ cells/kg, because of a 2.4-fold expansion. Post transduction, 10% of the cells effluxed rhodamine (a function of the MDR-1 encoded p-glycoprotein), as compared to 1% of the non-transduced cells. The patient received low dose (100 cGy) total body irradiation (TBI), followed by infusion of the transduced cells. The patient then received 4 cycles of vincristine, dose-escalating etoposide, and prednisone, and the platelet count nadir improved with each cycle (18, 65, 98, and 131K after cycles 1, 2, 3, and 4), as did the ANC nadir by the final cycle (100 cycle 1 v. 640 cycle 4). The patient had no evidence of disease prior to a second, myeloablative transplant using the original unmanipulated cells infused after high dose cyclophosphamide and TBI (1200 cGy). The grade 4 adverse events included febrile neutropenia and thrombocytopenia after the first cycle of dose escalating chemotherapy, and after the myeloablative transplant. At one year after infusion of transduced cells, the patient remains well and free of disease. Thus, a patient who was poor risk for autologous transplant initially, due to rapid re-growth of disease, was brought to a myeloablative transplant without residual disease by this treatment with gene modified cells. The striking improvement in nadir platelet count was presumably due to expansion of MDR-1 expressing cells. Lastly, the final, fully myeloablative transplant should represent a safety feature, protecting against the development of a malignancy due to insertional mutagenesis, as the gene modified cells would not be expected to survive.