Replication-competent Adenovirus-mediated Suicide Gene Therapy Research Articles

Feasibility of Adenovirus-Mediated hNIS Gene Transfer and 131I Radioiodine Therapy as a Definitive Treatment for Localized Prostate Cancer

We have developed a replication-competent adenovirus (Ad5-yCD/mutTK(SR39)rep-hNIS) armed with two suicide genes and the human sodium iodide symporter (hNIS) gene. In this context, hNIS can be used as a reporter gene in conjunction with nuclear imaging and as a potentially therapeutic gene when combined with (131)I radioiodine therapy. Here, we quantified the volume and magnitude of hNIS gene expression in the human prostate following injection of a high Ad5-yCD/mutTK(SR39)rep-hNIS dose using a standardized injection algorithm, and estimated the radiation dose that would be delivered to the prostate had men been administered (131)I with curative intent. Six men with clinically localized prostate cancer received an intraprostatic injection of Ad5-yCD/mutTK(SR39)rep-hNIS under transrectal ultrasound guidance. All men received 2 × 0.5 ml deposits (5 × 10(11) vp/deposit) in each of the four base and midgland sextants and 2 × 0.25 ml deposits (2.5 × 10(11) vp/deposit) in each of the two apex sextants for a total of 12 deposits (5 × 10(12) vp) in 5 ml. On multiple days after the adenovirus injection, men were administered sodium pertechnetate (Na(99m)TcO(4)) and hNIS gene expression in the prostate was quantified by single photon emission computed tomography (SPECT). hNIS gene expression was detected in the prostate of six of six (100%) men. On average, 45% (range 18-83%) of the prostate volume was covered with gene expression. Had men been administered 200 mCi (131)I, we estimate that the mean absorbed dose to the prostate would be 7.2 ± 4.8 Gy (range 2.1-13.3 Gy), well below that needed to sterilize the prostate. We discuss the obstacles that must be overcome before adenovirus-mediated hNIS gene transfer and (131)I radioiodine therapy can be used as a definitive treatment for localized prostate cancer.

Adaptive seamless design for an efficacy trial of replication-competent adenovirus-mediated suicide gene therapy and radiation in newly-diagnosed prostate cancer (ReCAP Trial)

Purpose Cumulative evidence has suggested investigation of the efficacy of Replication-Competent Adenovirus-mediated Suicide Gene Therapy in newly-diagnosed Prostate Cancer (ReCAP). There is a challenge in designing an efficacy trial for newly-diagnosed prostate cancer given its long natural history. The regulatory agency recommended a Phase II trial for safety before conducting the efficacy trial. Experimental design The ReCAP trial is an adaptive seamless, multi-site open-label, randomized Phase II/III trial. Two hundred eighty men will be randomized to receive either replication-competent adenovirus-mediated suicide gene therapy followed by radiation (Arm 1) or radiation alone (Arm 2). Phase II trial component will include the first 21 patients in Arm 1 with complete toxicity through day 90 for safety evaluation. The primary efficacy endpoint is the time free from biochemical and/or clinical failure (FFF). The secondary efficacy endpoints are 2-year prostate biopsies and overall survival. Unequal spaced interim looks are proposed with the adaptive sample-size re-estimation. Results This trial has been approved by the FDA for the study therapy investigation and is currently recruiting patients. Conclusions Challenges remain in designing newly-diagnosed prostate cancer trials. Adaptive seamless design is time-saving and a cost-effective design in the development of novel medical therapies, but requires a specified statistical plan in the decision process involved.

Noninvasive Imaging and Radiovirotherapy of Prostate Cancer Using an Oncolytic Measles Virus Expressing the Sodium Iodide Symporter

Prostate cancer cells overexpress the measles virus (MV) receptor CD46. Herein, we evaluated the antitumor activity of an oncolytic derivative of the MV Edmonston (MV-Edm) vaccine strain engineered to express the human sodium iodide symporter (NIS; MV-NIS virus). MV-NIS showed significant cytopathic effect (CPE) against prostate cancer cell lines in vitro. Infected cells effectively concentrated radioiodide isotopes as measured in vitro by Iodide-125 ((125)I) uptake assays. Virus localization and spread in vivo could be effectively followed by imaging of (123)I uptake. In vivo administration of MV-NIS either locally or systemically (total dose of 9 x 10(6) TCID(50)) resulted in significant tumor regression (P < 0.05) and prolongation of survival (P < 0.01). Administration of (131)I further enhanced the antitumor effect of MV-NIS virotherapy (P < 0.05). In conclusion, MV-NIS is an oncolytic vector with significant antitumor activity against prostate cancer, which can be further enhanced by (131)I administration. The NIS transgene allows viral localization and monitoring by noninvasive imaging which can facilitate dose optimization in a clinical setting.

Phase I Study of Noninvasive Imaging of Adenovirus-mediated Gene Expression in the Human Prostate

To monitor noninvasively potentially therapeutic adenoviruses for cancer, we have developed a methodology based on the sodium iodide symporter (NIS). Men with clinically localized prostate cancer were administered an intraprostatic injection of a replication-competent adenovirus, Ad5-yCD/utTK(SR39)rep-hNIS, armed with two suicide genes and the NIS gene. NIS gene expression (GE) was imaged noninvasively by uptake of Na(99 m)TcO(4) in infected cells using single photon emission-computed tomography (SPECT). The investigational therapy was safe with 98% of the adverse events being grade 1 or 2. GE was detected in the prostate in seven of nine (78%) patients at 1 x 10(12) virus particles (vp) but not at 1 x 10(11) vp. Volume and total amount of GE was quantified by SPECT. Following injection of 1 x 10(12) vp in 1 cm(3), GE volume (GEV) increased to a mean of 6.6 cm(3), representing, on average, 18% of the total prostate volume. GEV and intensity peaked 1-2 days after the adenovirus injection and was detectable in the prostate up to 7 days. Whole-body imaging demonstrated intraprostatic gene expression, and there was no evidence of extraprostatic dissemination of the adenovirus by SPECT imaging. The results demonstrate that noninvasive imaging of adenovirus-mediated gene therapy in humans is feasible and safe.

Toxicity and Efficacy of Replication-competent Adenovirus-mediated Suicide Gene Therapy with Radiation in a Preclinical Model of Glioma

High-grade gliomas carry a dismal prognosis owing to their infiltrative nature and high rate of local recurrence. With the goal of improving the outlook for this disease, we examined the potential of combining replication-competent adenovirus-mediated suicide gene therapy (gene therapy) with radiation (XRT) in a preclinical model of human glioma. The purpose of this study was to evaluate the toxicity and efficacy of gene therapy + XRT in a preclinical model of human glioma.

41. Preliminary Long-Term Efficacy of Replication-Competent Adenovirus-Mediated Suicide Gene Therapy for the Treatment of Locally Recurrent Prostate Cancer

41. Preliminary Long-Term Efficacy of Replication-Competent Adenovirus-Mediated Suicide Gene Therapy for the Treatment of Locally Recurrent Prostate Cancer

Replication-competent Adenovirus-mediated Suicide Gene Therapy with Radiation in a Preclinical Model of Pancreatic Cancer

In preparation for a Phase I trial, we evaluated the efficacy and toxicity of replication-competent adenovirus-mediated suicide gene therapy in combination with radiation in a preclinical model of pancreatic cancer. Human MiaPaCa-2 and PANC-1 pancreatic adenocarcinoma cells were found to be sensitive to the oncolytic effects of the Ad5-yCD/mutTK(SR39)rep-ADP adenovirus and also to the cytotoxic effects of the yeast cytosine deaminase (yCD) and herpes simplex virus thymidine kinase (HSV-1 TK(SR39)) genes in vitro. Combining Ad5-yCD/mutTK(SR39)rep-ADP-mediated suicide gene therapy with radiation significantly increased tumor control beyond that of either modality alone. Injection of Ad5-yCD/mutTK(SR39)rep-ADP in the dog pancreas at doses (10(12) virus particle (vp)) to be used in humans resulted in mild pancreatitis but not peritonitis or hepatotoxicity. Following administration of 9-(4-[(18)F]-fluoro-3-hydroxymethylbutyl)guanine ([(18)F]-FHBG), a positron-emitting substrate of HSV-1 TK, Ad5-yCD/mutTK(SR39)rep-ADP activity could be monitored non-invasively by positron emission tomography (PET). [(18)F]-FHBG uptake was readily detected in the pancreas but not in other major abdominal organs, indicating that little of the injected adenovirus disseminates to collateral tissues. These results demonstrate that Ad5-yCD/mutTK(SR39)rep-ADP-mediated suicide gene therapy has the potential to augment the effectiveness of pancreatic radiotherapy without resulting in excessive toxicity. Hence they provide the scientific basis for an ongoing Phase I trial in pancreatic cancer.

Phase I Trial of Replication-competent Adenovirus-mediated Suicide Gene Therapy Combined with IMRT for Prostate Cancer

Replication-competent adenovirus-mediated suicide gene therapy is an investigational cancer treatment in which an oncolytic adenovirus armed with chemo-radiosensitizing genes is used to destroy tumor cells. Previously, we evaluated the toxicity and efficacy of this approach in two clinical trials of prostate cancer using a first-generation adenovirus. Here, we report the toxicity and preliminary efficacy of this approach in combination with intensity-modulated radiotherapy (IMRT) in patients with newly diagnosed prostate cancer using an improved, second-generation adenovirus. The investigational therapy was associated with low toxicity, and there were no dose-limiting toxicities or treatment-related serious adverse events. Relative to a previous trial using a first-generation adenovirus, there was no increase in hematologic, hepatic, gastrointestinal (GI), or genitourinary (GU) toxicities. Post-treatment prostate biopsies yielded provocative preliminary results. When the results of two similar trials were combined, 22% of evaluable patients were positive for adenocarcinoma at their last biopsy, which is better than expected (>or=40%) for this cohort of patients (P=0.038). When the results were categorized by prognostic risk, most of the treatment effect was observed in the intermediate-risk group, with 0 of 12 patients (0%) being positive for cancer at their last biopsy (P<0.01). These results further demonstrate the safety of this investigational approach and raise the possibility that it may have the potential to improve the outcome of conformal radiotherapy in select patient groups.

Five-year Follow-up of Trial of Replication-competent Adenovirus-mediated Suicide Gene Therapy for Treatment of Prostate Cancer

Replication-competent adenovirus-mediated suicide gene therapy is an investigational cancer treatment that combines the oncolytic actions of human adenoviruses with the cytotoxic effects of chemo-radiosensitizing genes. Previously, we reported the short-term effects of this therapy in men with local recurrence of prostate cancer after definitive radiotherapy. With a median prostate-specific antigen (PSA) follow-up of 5 years, we report here the effect of the gene therapy on prostate-specific antigen doubling time (PSADT), a surrogate end point with significant prognostic power. When considering all evaluable subjects, the PSADT increased following the gene therapy from a mean of 17 to 31 months (median 16 to 22 months) (P=0.014). Assuming that salvage androgen suppression therapy androgen suppression therapy (AST) was uniformly initiated at a PSA of 15 ng/mL, the gene therapy would have delayed the projected onset of salvage therapy by an average of 2 years. The results indicate that replication-competent adenovirus-mediated suicide gene therapy may provide a potential long-term benefit to patients, as shown by a lengthening of the PSADT, and delay in when salvage therapy is indicated. Given the high morbidity associated with AST, we believe this approach could provide an attractive treatment option for selection of patients experiencing PSA relapse following definitive therapy.

Second-Generation Replication-Competent Oncolytic Adenovirus Armed with Improved Suicide Genes and ADP Gene Demonstrates Greater Efficacy without Increased Toxicity

Replication-competent adenovirus-mediated suicide gene therapy has proven to be safe in humans when delivered intraprostatically. Although signs of efficacy are emerging, it is likely that further improvements will be needed before this technology will have widespread applicability in the clinic. Toward this end, we have developed a second-generation, replication-competent adenovirus (Ad5-yCD/mutTKSR39rep-ADP) containing an improved yeast cytosine deaminase (yCD)/mutantSR39 herpes simplex virus thymidine kinase fusion (yCD/mutTKSR39) gene and the adenovirus death protein (ADP) gene. Relative to the first-generation Ad5-CD/TKrep adenovirus, Ad5-yCD/mutTKSR39rep-ADP demonstrated greater tumor cell kill in vitro and significantly greater tumor control in preclinical models of human cancer. Quantification of transgene volume following direct injection of fadenovirus into human tumor xenografts and the naïve canine prostate demonstrated that ADP enhanced adenoviral spread in vivo. Toxicology studies were performed to determine whether the improved yCD/mutTKSR39 fusion and ADP genes increased toxicity. Intraprostatic injection of Ad5-yCD/mutTKSR39rep-ADP did not result in significantly increased toxicity relative to the parental Ad5-CD/TKrep adenovirus, the latter of which has proven to be safe in two Phase I prostate cancer clinical trials. Together, these results provide the scientific basis for evaluating the safety and efficacy of the second-generation Ad5-yCD/mutTKSR39rep-ADP adenovirus in humans.

724. Phase I Study of Replication-Competent Adenovirus-Mediated Suicide Gene Therapy in Combination with Conformal Radiotherapy for the Treatment of Intermediate- to High-Risk Prostate Cancer: Two Year Efficacy Results

Adenovirus-mediated suicide gene therapy may hold much promise in the treatment of human cancer. We have developed a novel approach that utilizes an oncolytic, replication-competent adenovirus to deliver a therapeutic CD/HSV-1 TK fusion gene to tumors. The efficacy of oncolytic adenoviral therapy can be enhanced significantly by invoking two suicide gene systems (CD/5-FC and HSV-1 TK/GCV), which render malignant cells sensitive to specific pharmacological agents, and sensitizes them to radiation. Our preclinical work has provided the scientific basis for three Phase I prostate cancer clinical trials that were recently completed with excellent results. In our second trial, we evaluated the safety and efficacy of our oncolytic adenoviral/suicide gene therapy approach in combination with conformal radiotherapy in patients with newly diagnosed, intermediate- to high-risk prostate cancer. Fifteen patients in five cohorts received a single intraprostatic injection (1012 vp) of a first-generation, replication-competent adenovirus (Ad5-CD/ TKrep) on Day 1. Two days later, subjects were administered 5-FC and vGCV prodrug therapy along with 70 Gy conformal radiotherapy. The median follow-up is 40 months and all subjects have passed the two-year primary efficacy endpoint. Fifteen of 15 (100%) subjects have achieved a serum PSA |[le]| 1 ng/mL and 8 of 10 (80%) subjects not treated with hormone therapy have achieved a serum PSA |[le]| 0.5 ng/mL. Only one subject (high-risk) has failed biochemically. One- and two-year prostate biopsies have generated provocative results. Whereas 30% of intermediate-risk patients treated with 70 Gy radiotherapy alone are expected to be positive for adenocarcinoma at two years, 0 of 5 (0%) subjects treated with the gene therapy and radiotherapy combination had cancer at the two-year time point. None of these subjects received hormone therapy. Two (of 7) intermediate-risk subjects were not biopsied at two years because of concomitant medical issues. Both subjects were negative for adenocarcinoma at one-year. Thus, 7 of 7 (100%) of intermediate-risk subjects were negative for cancer at their last biopsy and none have any evidence of disease. By contrast, 4 of 8 (50%) high-risk subjects were negative for cancer at their last biopsy, which is comparable to that expected (44%) for 70 Gy radiotherapy alone. It has been demonstrated previously that CAR is down- regulated in high-grade prostate cancer, which may explain why this adenovirus-based approach failed to show a benefit in the high-risk patient group. The results indicate that oncolytic adenoviral and suicide gene therapies may improve the effectiveness of conformal radiotherapy in intermediate-risk prostate cancer. Based on these encouraging results, a randomized, prospective, two-arm Phase II trial will soon be initiated that will compare the efficacy of replication- competent adenovirus-mediated suicide gene therapy in combination with 76 Gy IMRT vs. 76 Gy IMRT alone using an improved, second-generation adenovirus (Ad5-yCD/mutTKSR39rep-ADP) that has already demonstrated to be safe in a Phase I trial.