ATIM-26. IMMUNOLOGIC TRENDS ASSOCIATED WITH PATIENT OUTCOMES IN A PHASE 1 CLINICAL TRIAL OF TOCA 511 AND TOCA FC IN RECURRENT HIGH GRADE GLIOMA
ABSTRACT: Abstract Toca 511 (vocimagene amiretrorepvec) is a cancer selective, retroviral replicating vector encoding a codon optimized, heat stabilized cytosine deaminase that converts Toca FC (extended-release 5- fluorocytosine, 5-FC) into the anticancer agent 5-fluorouracil. Preclinical evidence demonstrates that the Toca 511 & Toca FC regimen kills cancer cells and immunosuppressive myeloid cells in the tumor microenvironment, leading to durable antitumor immune responses that can be adoptively transferred to untreated animals. In an ascending dose trial (NCT01470794) in patients with recurrent high grade glioma (rHGG), Toca 511 was injected into the resection cavity walls at the time of resection, and then multiple courses of oral Toca FC were administered. Multiyear durable and complete responses by independent radiology review have been reported. Human immune monitoring results support an immunologic mechanism of action and identify potential biomarkers related to patient outcomes. Measurements included the quantification of peripheral blood and tumor infiltrating leukocyte subsets by flow cytometry, immunohistochemistry, and deconvolution of DNA and RNA sequencing data. In addition, systemic cytokine levels were assessed in peripheral blood serum by multiplex digital ELISA. Univariate comparisons and multivariate models revealed immunologic trends associated with patient outcomes. Pre-treatment tumor infiltrating cell subsets, quantified via deconvolution of RNA sequencing data, were associated with both objective responses and survival. Subsequent exploratory models applied to selected patient data indicate that a combined biomarker using mRNA signatures from multiple leukocyte subsets may predict patient outcomes with high sensitivity and selectivity. In addition, post-treatment serum cytokine time-course results suggest that differences and temporal modulations are associated with both objective response and survival. These results support an immune-related mechanism of action for the Toca 511 & Toca FC regimen. Potentially predictive and/or prognostic biomarkers of patient outcomes will be evaluated in the ongoing randomized Phase 3 Toca 5 trial in patients with rHGG (NCT02414165).
Project description:Abstract Toca 511 (vocimagene amiretrorepvec) is an investigational retroviral replicating vector that selectively infects dividing cancer cells, integrates into the genome and replicates due to immune defects in tumors. Toca 511 spreads through tumors and stably delivers the gene encoding an optimized yeast cytosine deaminase that converts the prodrug Toca FC (an investigational, extended-release formulation of 5-fluorocytosine) into 5-fluorouracil. 5-fluorouracil kills infected cancer cells and surrounding cancer cells, myeloid derived suppressor cells and tumor associated macrophages, thus enabling immune activity against the tumor. In this phase 1 trial (NCT01470794), ascending doses of Toca 511 were injected into the resection bed of patients with rHGG, followed by multiple courses of oral Toca FC. Additional cohorts included combination of the investigational therapy with bevacizumab or lomustine. Objective responses (ORs) are observed in patients with IDH1 wildtype and mutant tumors, including 3 complete responses (CRs) and 2 partial responses with the investigational therapy, and 1 CR with the investigational therapy and bevacizumab. The IDH1-mutant patients treated at 1st recurrence all had CRs and the fact that a CR in rHGG is rare suggests that the investigational treatment may be playing a role. ORs are observed 6–19 months after Toca 511 injection, consistent with an immunologic mechanism. Median time to initial response is 9.2 months; median duration of response (mDoR) is 25.2 months. Excluding combination cohorts, mDoR is 26.7 months. All responders are alive 21.2+ to 42.6+ months, suggesting a correlation of durable responses (ORs lasting > 24 weeks) with overall survival. In a 24-patient subgroup who received the recommended Ph2 Toca 511 dose, a durable response rate of 20.8% was observed. Across the Phase 1 program, the safety profile remains favorable. Updated clinical benefit, safety, immune activity, and molecular profiles will be reported.
Project description:Background:Vocimagene amiretrorepvec (Toca 511) is an investigational gamma-retroviral replicating vector encoding cytosine deaminase that, when used in combination with extended-release 5-fluorocytosine (Toca FC), results preclinically in local production of 5-fluorouracil, depletion of immune-suppressive myeloid cells, and subsequent induction of antitumor immunity. Recurrent high-grade glioma (rHGG) patients have a high unmet need for effective therapies that produce durable responses lasting more than 6 months. In this setting, relapse is nearly universal and most responses are transient. Methods:In this Toca 511 ascending-dose phase I trial (NCT01470794), HGG patients who recurred after standard of care underwent surgical resection and received Toca 511 injected into the resection cavity wall, followed by orally administered cycles of Toca FC. Results:Among 56 patients, durable complete responses were observed. A subgroup was identified based on Toca 511 dose and entry requirements for the follow-up phase III study. In this subgroup, which included both isocitrate dehydrogenase 1 (IDH1) mutant and wild-type tumors, the durable response rate is 21.7%. Median duration of follow-up for responders is 35.7+ months. As of August 25, 2017, all responders remain in response and are alive 33.9+ to 52.2+ months after Toca 511 administration, suggesting a positive association of durable response with overall survival. Conclusions:Multiyear durable responses have been observed in rHGG patients treated with Toca 511 + Toca FC in a phase I trial, and the treatment will be further evaluated in a randomized phase III trial. Among IDH1 mutant patients treated at first recurrence, there may be an enrichment of complete responders.
Project description:A tumor-selective non-lytic retroviral replicating vector (RRV), Toca 511 (vocimagene amiretrorepvec), is being investigated in clinical trials in patients with recurrent high grade glioma (rHGG) (www.clinicaltrials.gov NCT01156584, NCT01470794, NCT01985256). Toca 511 encodes a modified yeast cytosine deaminase (CD), which converts oral prodrug 5-FC into the anticancer drug 5-fluorouracil (5-FU) within infected tumor cells. Since 5-FU is a radiosensitizer, we investigated in preclinical models the combination of Toca 511, 5-FC and radiation for treatment of human HGG. U87 and radioresistent U87EGFRvIII cells were infected in vitro with Toca 511 and subsequently irradiated with 0, 3, 6 or 9 Gy. In non-irradiated and irradiated cells, RRV infected >95% of cells by day 21 showing that radiation does not perturb viral spread. In vitro clonogenic survival assays showed significant radiosensitization with 5-FC in RRV-infected U87EGFRvIII cells. For in vivo survival studies, U87EGFRvIII cells (5 x 104) were stereotactically implanted into athymic mouse brain and Toca 511 (105 Transducing Units) was injected intratumorally 4 days later. Mice were treated with a single cycle of intraperitoneal PBS or 5-FC (500 mg/kg) for 5 days from day 10 to 14, with or without irradiation (2 Gy/fr/day; total 10 Gy, or 4 Gy/fr/day; total 20 Gy). Mice treated with 20 Gy and a single cycle of 5-FC showed significantly longer survival compared with the other two groups (p<0.0001) and median survival was >75 days. Next, mice were treated with multiple cycles of PBS or 5-FC (intraperitoneal, 5 days every 2 weeks, 5 cycles) with or without irradiation at the lower dose (total 10 Gy). Mice treated with 10 Gy and 5 cycles of 5-FC showed significantly longer survival (p<0.0001) and median survival was >89 days. These efficacy data support clinical investigation of Toca 511 and 5-FC in combination with radiation in the first-line setting for patients with HGG.
Project description:Background:Toca 511 (vocimagene amiretrorepvec) is a retroviral replicating vector encoding an optimized yeast cytosine deaminase (CD). Tumor-selective expression of CD converts the prodrug, 5-fluorocytosine (5-FC), into the active chemotherapeutic, 5-fluorouracil (5-FU). This therapeutic approach is being tested in a randomized phase II/III trial in recurrent glioblastoma and anaplastic astrocytoma (NCT0241416). The aim of this study was to identify the immune cell subsets contributing to antitumor immune responses following treatment with 5-FC in Toca 511-expressing gliomas in a syngeneic mouse model. Methods:Flow cytometry was utilized to monitor and characterize the immune cell infiltrate in subcutaneous Tu-2449 gliomas in B6C3F1 mice treated with Toca 511 and 5-FC. Results:Tumor-bearing animals treated with Toca 511 and 5-FC display alterations in immune cell populations within the tumor that result in antitumor immune protection. Attenuated immune subsets were exclusive to immunosuppressive cells of myeloid origin. Depletion of immunosuppressive cells temporally preceded a second event which included expansion of T cells which were polarized away from Th2 and Th17 in the CD4+ T cell compartment with concomitant expansion of interferon gamma-expressing CD8+ T cells. Immune alterations correlated with clearance of Tu-2449 subcutaneous tumors and T cell-dependent protection from future tumor challenge. Conclusions:Treatment with Toca 511 and 5-FC has a concentrated effect at the site of the tumor which causes direct tumor cell death and alterations in immune cell infiltrate, resulting in a tumor microenvironment that is more permissive to establishment of a T cell mediated antitumor immune response.
Project description:Abstract BACKGROUND Toca 511 (vocimagene amiretrorepvec) is a cancer-selective, retroviral replicating vector encoding a codon optimized, heat stabilized cytosine deaminase that converts Toca FC (extended-release 5-fluorocytosine, 5-FC) into the anticancer agent 5-fluorouracil. Three Ph1 studies in patients with recurrent high grade glioma have demonstrated a tolerable safety profile and encouraging efficacy. METHODS Toca 5 is a multi-national, randomized, open-label Ph3 trial (NCT02414165) of Toca 511 & Toca FC versus standard of care (SOC) options that comprises Investigator’s choice of single agent chemotherapy (lomustine, temozolomide) or bevacizumab in patients who have undergone resection for first or second recurrence of glioblastoma or anaplastic astrocytoma. 403 patients were randomized 1:1 to the Toca arm or the SOC arm and stratified by IDH1 status, KPS, and geographic region. Primary endpoint was overall survival (OS), and secondary endpoints were durable response rate, durable clinical benefit rate, duration of durable response, and 12-month survival rate. The study used group sequential design including 2 interim analyses and 1 final analysis, and the stratified log-rank test are used for the analysis. RESULTS 271 events were observed for this analysis. Median follow-up was 22.8 months, and the Toca arm missed the primary endpoint (OS) compared to the SOC arm (11.1 months median compared to 12.2 months, HR=1.06, p=0.6154). All secondary endpoints showed no meaningful difference between the arms of the trial. The safety, tolerability and adverse event profile of Toca 511 and Toca FC was as expected for this patient population, with low incidences of Grade 3–4 adverse events. Pre-planned subgroup analyses showed compelling OS improvement in patients with secondary recurrence, and favorable trends in IDH1 mutant and AA population. Detailed data will be presented at the time of the conference.
Project description:Abstract Toca 511, a clinical-stage retroviral replicating vector (RRV) encoding an optimized yeast cytosine deaminase (CD) prodrug activator gene, in combination with Toca FC (extended-release 5-fluorocytosine (5-FC)), is designed to produce 5-FU which kills cancer cells and immune-suppressive myeloid cells in the tumor microenvironment, leading to anti-cancer immune activation and long term survival. The combination treatment is currently under evaluation in an international Phase 2/3 trial in patients with recurrent high-grade glioma. In the present study, we investigated the feasibility of further applying Toca 511 to brain-metastatic breast cancer, which frequently arises from highly aggressive, treatment-refractory, “triple-negative” (ER(-) PR(-) HER2(-)) disease, and is associated with a dismal prognosis of 4-6 months survival. We first evaluated in vitro replication kinetics of RRV encoding the GFP reporter gene in MDA-MB-231-BR (human) and JC (murine) breast cancer cells. After virus inoculation at either M.O.I. of 0.01 or 0.1, high levels of transduction were achieved within 1-2 weeks as measured by flow cytometric quantitation of GFP fluorescence. Next, we tested in vitro cytotoxicity by MTS assay after 5-FC treatment of MDA-MB-231BR and JC cells transduced with Toca 511. In both Toca 511-transduced breast cancer lines, cell viability was reduced by approximately 70-85% after exposure to 0.1 mM 5-FC and complete cell killing was observed with 1 mM 5-FC within 4-6 days. In survival studies, animals treated with Toca 511 followed by 5-FC prodrug showed statistically significant (231-BR: p<0.0001, JC: p=0.0003) survival benefit compared to the control group. These data provide preclinical validation for a new Phase Ib trial evaluating RRV-mediated immunotherapy in various types of metastatic malignancies, including CNS-metastatic breast cancer (TOCA 6 trial: clinicaltrials.gov NCT02576665), currently recruiting at the University of Miami.
Project description:<h4>Background</h4>Toca 511, a gamma retroviral replicating vector encoding cytosine deaminase, used in combination with 5-fluorocytosine (5-FC) kills tumor by local production of 5-fluorouracil (5-FU), inducing local and systemic immunotherapeutic response resulting in long-term survival after cessation of 5-FC. Toca 511 and Toca FC (oral extended-release 5-FC) are under investigation in patients with recurrent high-grade glioma. Lomustine is a treatment option for patients with high-grade glioma.<h4>Methods</h4>We investigated the effects of lomustine combined with Toca 511 + 5-FC in syngeneic orthotopic glioma models. Safety and survival were evaluated in immune-competent rat F98 and mouse Tu-2449 models comparing Toca 511 + 5-FC to lomustine + 5-FC or the combination of Toca 511 + 5-FC + lomustine. After intracranial implantation of tumor, Toca 511 was delivered transcranially followed by cycles of intraperitoneal 5-FC with or without lomustine at the first or fourth cycle.<h4>Results</h4>Coadministration of 5-FC with lomustine was well tolerated. In F98, combination Toca 511 + 5-FC and lomustine increased median survival, but "cures" were not achieved. In Tu-2449, combination Toca 511 + 5-FC and lomustine increased median survival and resulted in high numbers of cure. Rejection of tumor rechallenge occurred after treatment with Toca 511 + 5-FC or combined with lomustine, but not with lomustine + 5-FC. Mixed lymphocyte-tumor cell reactions using splenocytes from cured animals showed robust killing of target cells in an effector:target ratio-dependent manner with Toca 511 + 5-FC and Toca 511 + 5-FC + lomustine day 10.<h4>Conclusion</h4>The combination of Toca 511 + 5-FC and lomustine shows promising efficacy with no additive toxicity in murine glioma models. Immunotherapeutic responses resulting in long-term survival were preserved despite lomustine-related myelosuppression.
Project description:Toca 511 (vocimagene amiretrorepvec), a nonlytic, amphotropic retroviral replicating vector (RRV), encodes and delivers a functionally optimized yeast cytosine deaminase (CD) gene to tumors. In orthotopic glioma models treated with Toca 511 and 5-fluorocytosine (5-FC) the CD enzyme within infected cells converts 5-FC to 5-fluorouracil (5-FU), resulting in tumor killing. Toca 511, delivered locally either by intratumoral injection or by injection into the resection bed, in combination with subsequent oral extended-release 5-FC (Toca FC), is under clinical investigation in patients with recurrent high-grade glioma (HGG). If feasible, intravenous administration of vectors is less invasive, can easily be repeated if desired, and may be applicable to other tumor types. Here, we present preclinical data that support the development of an intravenous administration protocol. First we show that intravenous administration of Toca 511 in a preclinical model did not lead to widespread or uncontrolled replication of the RVV. No, or low, viral DNA was found in the blood and most of the tissues examined 180 days after Toca 511 administration. We also show that RRV administered intravenously leads to efficient infection and spread of the vector carrying the green fluorescent protein (GFP)-encoding gene (Toca GFP) through tumors in both immune-competent and immune-compromised animal models. However, initial vector localization within the tumor appeared to depend on the mode of administration. Long-term survival was observed in immune-competent mice when Toca 511 was administered intravenously or intracranially in combination with 5-FC treatment, and this combination was well tolerated in the preclinical models. Enhanced survival could also be achieved in animals with preexisting immune response to vector, supporting the potential for repeated administration. On the basis of these and other supporting data, a clinical trial investigating intravenous administration of Toca 511 in patients with recurrent HGG is currently open and enrolling.
Project description:Retroviral replicating vectors (RRVs) are a nonlytic alternative to oncolytic replicating viruses as anticancer agents, being selective both for dividing cells and for cells that have defects in innate immunity and interferon responsiveness. Tumor cells fit both these descriptions. Previous publications have described a prototype based on an amphotropic murine leukemia virus (MLV), encoding yeast cytosine deaminase (CD) that converts the prodrug 5-fluorocytosine (5-FC) to the potent anticancer drug, 5-fluorouracil (5-FU) in an infected tumor. We report here the selection of one lead clinical candidate based on a general design goal to optimize the genetic stability of the virus and the CD activity produced by the delivered transgene. Vectors were tested for titer, genetic stability, CD protein and enzyme activity, ability to confer susceptibility to 5-FC, and preliminary in vivo antitumor activity and stability. One vector, Toca 511, (aka T5.0002) encoding an optimized CD, shows a threefold increased specific activity in infected cells over infection with the prototype RRV and shows markedly higher genetic stability. Animal testing demonstrated that Toca 511 replicates stably in human tumor xenografts and, after 5-FC administration, causes complete regression of such xenografts. Toca 511 (vocimagene amiretrorepvec) has been taken forward to preclinical and clinical trials.
Project description:Treatment of tumors with Toca 511, a gamma retroviral replicating vector encoding cytosine deaminase, followed by 5-fluorocytosine (5-FC) kills tumors by local production of 5-fluorouracil (5-FU). In brain tumor models, this treatment induces systemic anti-tumor immune responses and long-term immune-mediated survival. Phase 1 Toca 511 and Toca FC (extended-release 5-FC) clinical trials in patients with recurrent high-grade glioma show durable complete responses and promising survival data compared to historic controls. The work described herein served to expand on our earlier findings in two models of metastatic colorectal carcinoma (mCRC). Intravenous (i.v.) delivery of Toca 511 resulted in substantial tumor-selective uptake of vector into metastatic lesions. Subsequent treatment with 5-FC resulted in tumor shrinkage, improved survival, and immune memory against future rechallenge with the same CT26 CRC cell line. Similar results were seen in a brain metastasis model of mCRC. Of note, 5-FC treatment resulted in a significant decrease in myeloid-derived suppressor cells (MDSCs) in mCRC tumors in both the liver and brain. These results support the development of Toca 511 and Toca FC as a novel immunotherapeutic approach for patients with mCRC. A phase 1 study of i.v. Toca 511 and Toca FC in solid tumors, including mCRC, is currently underway (NCT02576665).