ALBERT

Description: Chronic lymphocytic leukemia (CLL) cells can be made to express recombinant CD40-ligand (CD154) by transduction with a replication-defective adenovirus vector (Ad-CD154). Ad-CD154–transduced and bystander leukemia cells become highly effective antigen-presenting cells that can induce CLL-specific autologous cytotoxic T lymphocytes in vitro. This study investigated the immunologic and clinical responses to infusion of autologous Ad-CD154-CLL cells in patients with CLL. After a one-time bolus infusion of autologous Ad-CD154–transduced leukemia cells, there was increased or de novo expression of immune accessory molecules on bystander, noninfected CLL cells in vivo. Treated patients also developed high plasma levels of interleukin-12 and interferon-γ, the magnitudes of which corresponded to absolute blood CD4+T-cell counts before therapy. On average, patients experienced a greater than 240% increase in absolute blood T-cell counts within 1 to 4 weeks of treatment. Moreover, treatment increased the numbers of leukemia-specific T cells, demonstrated by autologous ELISPOT assay and mixed lymphocyte reactions. These biologic effects were associated with reductions in leukemia cell counts and lymph node size. Treatment did not induce autoimmune thrombocytopenia or hemolytic anemia and no dose-limiting toxicity was observed. This approach may provide a novel and effective form of gene therapy for patients with this disease.

Description: Abstract 1472 Background: Chronic lymphocytic leukemia (CLL) cells with del(17p) typically have loss of functional P53, rendering them refractory to chemotherapeutic agents. However, del(17p) CLL cells activated by CD40L (CD154) are induced to express pro-apoptotic factors that re-sensitize cells to the cytotoxic activity of P53-dependent drugs, such as fludarabine (F-ara-A). Chemotherapy re-sensitization is mediated in part by induction of p73, a p53-related transcription factor. To examine whether a CD154-based therapeutic strategy can be developed in vivo for del(17p) and/or fludarabine refractory CLL, a phase 1b clinical study evaluating an autologous cellular gene immunotherapy is being conducted. Autologous CLL cells transduced ex vivo with a replication defective adenovirus vector encoding a membrane-stable, re-engineered form of CD154 (Ad-ISF35) are administered, followed by standard courses of FCR in subjects with high-risk fludarabine refractory and/or del(17p) CLL. Methods: Subjects with fludarabine refractory and/or del(17p) receive three IV doses (one dose every two weeks) of 3×108 autologous CLL cells that have been transduced ex vivo with Ad-ISF35. Two weeks following the third dose of Ad-ISF35-transduced cells, subjects receive standard monthly cycles of fludarabine, cyclophosphamide and rituximab (FCR). Study endpoints include analysis of safety and efficacy. Correlative analyses are conducted for evidence of drug re-sensitization, regulation of apoptotic pathways, cytokine analysis, and humoral immune responses to the adenovirus vector and ISF35 transgene. Results: To date, four patients have completed treatment. Two patients have achieved a compete response, one of them without detectable minimal residual disease (MRD) by sensitive multiparameter flow cytometry of marrow mononuclear cells after completion of treatment. These responses have been durable after a median follow up of 18 months. One patient achieved a partial response with complete resolution of lymphocytosis, lymphadenopathy and splenomegaly, but residual CLL in the bone marrow. The remaining patient had progressive disease despite an initial response to both infusion of Ad-ISF35-transduced cells and FCR chemoimmunotherapy. Infusion of Ad-ISF35 transduced cells has been well tolerated. Overall, the most common adverse events have been transient fever, malaise and fatigue associated with infusion of Ad-ISF35-transduced cells and cytopenias after treatment with FCR. Prior to ISF35 treatment, CLL cells from patients were resistant to F-ara-A induced apoptosis (IC50 〉 10μM). However, one day following the first infusion of Ad-ISF35-transduced CLL cells, patient cells became sensitive to F-ara-A (IC50 0.3–1 μM). In addition, pro-apoptotic factors, including Bid, DR5, CD95, and P73 were induced in the non-transduced “bystander” CLL population following ISF35 infusion. These pro-apoptotic effects persisted ≥ 2 weeks following IV infusion. The sera from treated patients showed increase in IL-6 and IFN-γ after infusion of Ad-ISF35 transduced CLL cells. Despite evidence of anti-adenovirus antibody responses in the treated patients, there was no detectable anti-human CD154 production before or after ISF35 treatment. Conclusions: The results indicate that Ad-ISF35-cell-gene therapy can sensitize P53-deficient CLL to “P53-dependent” cytotoxic agents in vivo, allowing for effective and durable clinical responses. These data are very encouraging and suggest that this unique chemoimmunotherapy re-sensitization strategy could offer a valuable treatment option for patients who otherwise would be resistant to standard forms of therapy. Disclosures: Cantwell: Memgen: Employment. Kipps:Memgen, LLC: Membership on an entity's Board of Directors or advisory committees.

Description: Chronic lymphocytic leukemia (CLL) cells can be made to express recombinant CD40-ligand (CD154) by transduction with a replication-defective adenovirus vector (Ad-CD154). Ad-CD154–transduced and bystander leukemia cells become highly effective antigen-presenting cells that can induce CLL-specific autologous cytotoxic T lymphocytes in vitro. This study investigated the immunologic and clinical responses to infusion of autologous Ad-CD154-CLL cells in patients with CLL. After a one-time bolus infusion of autologous Ad-CD154–transduced leukemia cells, there was increased or de novo expression of immune accessory molecules on bystander, noninfected CLL cells in vivo. Treated patients also developed high plasma levels of interleukin-12 and interferon-γ, the magnitudes of which corresponded to absolute blood CD4+T-cell counts before therapy. On average, patients experienced a greater than 240% increase in absolute blood T-cell counts within 1 to 4 weeks of treatment. Moreover, treatment increased the numbers of leukemia-specific T cells, demonstrated by autologous ELISPOT assay and mixed lymphocyte reactions. These biologic effects were associated with reductions in leukemia cell counts and lymph node size. Treatment did not induce autoimmune thrombocytopenia or hemolytic anemia and no dose-limiting toxicity was observed. This approach may provide a novel and effective form of gene therapy for patients with this disease.

Description: Abstract 168FN2 CLL cells with del(17p) typically have loss of functional p53, rendering them refractory to chemotherapeutic agents. However, del(17p) CLL cells activated by CD40 ligand (CD154) are induced to express pro-apoptotic factors to overcome resistance to the cytotoxic activity of p53-dependent drugs, such as fludarabine. To examine whether a CD154-based therapeutic strategy can be developed in vivo for del(17p) and/or fludarabine-refractory CLL, a phase 1b clinical study evaluating an autologous cellular gene immunotherapy is being conducted. Autologous CLL cells transduced ex vivo with a replication-defective adenovirus vector encoding a membrane-stable, re-engineered form of CD154 (Ad-ISF35) are administered, followed by standard courses of FCR. Subjects with fludarabine-refractory and/or del(17p) CLL received three IV doses (one dose every two weeks) of 3×108autologous Ad-ISF35-transduced CLL cells. Two weeks following the third dose of Ad-ISF35-transduced cells, subjects receive up to six monthly cycles of FCR. Study endpoints include analysis of safety and efficacy. Nine (9) subjects have been enrolled and treated on study. Median age was 63 (range 48–70). All subjects were del(17p) (range 14–96%), and included treatment naïve (n=4) and previously treated (n=5) subjects. The number of prior treatments range from 0–5, including three subjects that previously received fludarabine-containing regimens. The overall response rate was 67% with 56% of subjects achieving a complete response (CR), including 3 CRu pending bone marrow assessment. Two subjects with a marked percentage del(17p) (range 63–66%) continue to have an ongoing complete response (CR) after a median follow up of 〉2 years, and no detectable minimal residual disease (MRD) in one subject. Three subjects that showed disease progression were treated with either alemtuzumab (1 subject) or ofatumumab plus high dose methylprednisolone therapy followed by allogeneic stem cell transplant (2 subjects). We observed clinical responses not only after FCR but also after infusion of Ad-ISF35-transduced cell. These ISF35-specific responses included reductions in absolute lymphocyte counts in all subjects (decrease from baseline 4–89%), and decreased lymphadenopathy (〉50% reduction) in 78% of the subjects (decrease from baseline 19–100%). Infusion of Ad-ISF35-transduced cells plus FCR has been well-tolerated. The primary non-hematologic adverse events have been flu-like symptoms following infusion of Ad-ISF35 transduced cells. This includes transient grade I/II fever (89%), fatigue (56%) and chills (56%). The primary hematologic adverse events have been cytopenias following FCR treatment, including grade III/IV neutropenia (33%) and anemia (22%). Grade I/II hypophosphatemia (56%) following ISF35 has been observed and this might be related to increased serum cytokine levels following Ad-ISF35-transduced cell administration. Correlative studies on CLL cells obtained before and after infusions of Ad-ISF35-transduced CLL cells demonstrated that CLL cells prior to treatment were refractory to the cytoxic effects of P53-dependent drugs (e.g. F-ara-A). However, the CLL cells obtained after treatment with Ad-ISF35-transduced CLL had increases of p73, p21 and Bid and became sensitive in vitro to the cytotoxic activity of F-ara-A. We also observed up-regulation of costimulatory molecules (CD80, CD86, CD54) and death receptors (CD95). The majority of subjects developed antibodies against adenovirus with neutralizing activity. However, they did not developed antibodies against human CD154. Subjects also showed increases in TNFα, IL-6 and IL12 after infusion of Ad-ISF35 transduced cells. In conclusion, the combination of Ad-ISF35 transduced CLL cells plus FCR appears to be well-tolerated and highly effective in CLL patients with fludarabine-refractory disease and/or del(17p). The CR rate that we have observed in this high-risk CLL population is higher than those reported in the literature and makes our results very encouraging. Correlative data suggest that Ad-ISF35 promotes upregulation of costimulatory and death receptor molecules as well as pro-apoptotic proteins that may overcome resistance to FCR in vivo. These encouraging data suggest the combination of Ad-ISF35 plus chemoimmunotherapy could offer an effective treatment option for patients who otherwise would be resistant to standard forms of therapy. Disclosures: Cantwell: Memgen, LLC: Employment, Patents & Royalties.