Cancer Therapy Clinical Trials Using Novel Recombinant Vaccines

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Therapeutic PSA-targeted poxviral vaccines for prostate cancer have been well tolerated. PROSTVAC-VF treatment was evaluated for safety, prolongation of progression free of survival (PFS), and overall survival, in a randomized, controlled, and blinded phase II study. 125 patients were randomized in a multi-center trial of vaccination series. Eligible patients had minimally symptomatic castration resistant metastatic prostate cancer (mCRPC). PROSTVAC-VF comprises 2 recombinant viral vectors, each encoding transgenes for prostate specific antigen (PSA) and 3 immune costimulatory molecules (B7.1, ICAM-1, and LFA3: TRICOM). Vaccinia-based vector was used for priming followed by 6 planned Fowlpox-based vector boosts. Patients were allocated (2:1) to PROSTVAC-VF + GM-CSF, versus Control empty vectors + saline injections. 2 patients received PROSTVAC-VF and 40 received Control vectors. Patient characteristics were similar. The primary endpoint was PFS, which was similar in the two groups (P=0.6). However, at 3 years post study, PROSTVAC-VF patients had a better overall survival with 25/82 (30%) alive, versus 7/40 (17%) Controls. There was a longer median survival by 8.5 months (24.5 months for vaccine versus 16 months Controls);and estimated hazard ratio 0.56 (95% CI 0.37-0.85); stratified log rank P=0.0061. PROSTVAC-VF immunotherapy was well tolerated and associated with a 44% reduction in the death rate and an 8.5 month improvement in median OS in men with mCRPC. These provocative data provide preliminary evidence of clinically meaningful benefit, but need to be confirmed in a larger Phase III study. A concurrent multicenter, randomized Phase II trial employing a recombinant poxviral vaccine provided evidence of enhanced median overall survival (OS) (p=0.0061) in patients with metastatic castrate-resistant prostate cancer (mCRPC). This study employed the identical vaccine in mCRPC to investigate the influence of GM-CSF with vaccine, and the influence of immunologic and prognostic factors on median OS. 32 patients were vaccinated once with recombinant vaccinia containing the transgenes for prostate-specific antigen (PSA) and three human costimulatory molecules (B7.1, ICAM-1 and LFA-3, designated as TRICOM). Patients received booster vaccines with recombinant fowlpox containing the same four transgenes. 12/32 patients showed declines in serum PSA and 2/12 showed evaluable decrease in index lesions. Median OS was 26.6 months. Patients with greater PSA-specific T-cell responses showed a trend (p=0.055) toward enhanced survival. There was no difference in T-cell responses or survival in cohorts of patients receiving GM-CSF vs no GM-CSF. Patients with a Halabi predicted survival of < 18 months (predicted 12.3 months) had an actual median OS of 14.6 months, while those with a Halabi predicted survival of ≥ 18 months (predicted survival 20.9 months) will meet or exceed 37.3 months, with 12/15 patients living longer than predicted (p=0.035). Treg suppressive function was shown to decrease in patients surviving longer than predicted and increase in patients surviving less than predicted. These studies provide evidence that patients with more indolent mCRPC (Halabi predicted survival ≥ 18 months) may best benefit from vaccine therapy. Pilot study of vaccination with recombinant CEA-MUC-1-TRICOM poxviral-based vaccines in patients with metastatic carcinoma. Poxviral vectors have a proven safety record and can be used to incorporate multiple transgenes. Prior clinical trials with poxviral vaccines have shown that immunologic tolerance to self-antigens can be broken. Carcinoembryonic antigen (CEA) and MUC-1 (breast cancer associated epithelial mucin) are overexpressed in a substantial proportion of common solid carcinomas. The primary end point of this study was vaccine safety, with immunologic and clinical responses as secondary end points. We report here a pilot study of 25 patients treated with a poxviral vaccine regimen consisting of the genes for CEA and MUC-1, along with a triad of costimulatory molecules (TRICOM; composed of B7.1, ICAM-1, and LFA-3) engineered into vaccinia (PANVAC-V) as a prime vaccination and into fowlpox (PANVAC-F) as a booster vaccination. The vaccine was well tolerated. Apart from injection-site reaction, no grade ≥2 toxicity was seen in more than 2% of the cycles. Immune responses to MUC-1and/or CEA were seen following vaccination in 9 of 16 patients tested. A patient with clear cell ovarian cancer and symptomatic ascites had a durable (18-month) clinical response radiographically and biochemically, and one breast cancer patient had a confirmed decrease of >20% in the size of large liver metastasis. This vaccine strategy seems to be safe, is associated with both CD8 and CD4 immune responses, and has shown evidence of clinical activity. Further trials with this agent, either alone or in combination with immunopotentiating and other therapeutic agents, are warranted. Dr. Gulley and his colleagues in the Laboratory of Tumor Immunology and Biology (LTIB) and the Medical Oncology Branch (MOB), Center for Cancer Research (CCR), NCI, have ongoing or recently completed in FY08-09 the following collaborative vaccine clinical trials at the NCI Clinical Center. A Phase I-II study of tumor vaccine following chemotherapy in patients with previously untreated metastatic breast cancer: Vaccine-induced bias of T-cell repertoire reconstitution after T-cell Reinfusion. (Collaboration with Dr. Sportes) MOB, CCR, NCI. This trial combines the concepts of T-cell repertoire reconstitution with vaccine therapy. An open label pilot study to evaluate the safety and tolerability of PANVAC-V (Vaccinia) and PANVAC-F (Fowlpox) in combination with Sargramostim (GM-CSF) in patients with metastatic adenocarcinoma, MOB, CCR, NCI. This trial employed vectors with transgenes of both multiple tumor antigens and multiple costimulatory molecules. A recent amendment allowed additional patients to further analyze the efficacy of the vaccine. An open label phase I study to evaluate the safety and tolerability of a vaccine (GI-6207) consisting of whole, heat-killed recombinant Saccharomyces cerevisiae (yeast) genetically modified to express CEA protein in adults with metastatic CEA-expressing carcinoma. This is a first in humans trial for this vaccine. An open label pilot study to evaluate the effect on the immune system of talactoferrin in adults with non-small cell lung cancer (NSCLC). Immunologic response to this agent is the primary endpoint. Collaborative Trials with Extramural Cancer Centers A phase II study of PROSTVAC-V(Vaccinia)/TRICOM and PROSTVAC-F(fowlpox)/TRICOM with GM-CSF in patients with PSA progression after local therapy for prostate cancer. (Eastern Cooperative Oncology Group) A Phase I study of sequential vaccinations with fowlpox-CEA(6D)-TRICOM and vaccinia-CEA(6D)-TRICOM, in combination with GM-CSF and Interferon-Alfa-2B in patients with CEA expressing carcinomas. (Ohio State Comprehensive Cancer Center) A Phase I study of regulatory T cell depletion with Denileukin Diftitox followed by active immunotherapy with autologous dendritic cells infected with CEA-6D expressing fowlpox-TRICOM in patients with advanced or metastatic malignancies expressing CEA (Duke Comprehensive Cancer Center) Phase I study of intravessical recombinant fowlpox-GM-CSF and or recombinant fowlpox-TRICOM in patients with bladder carcinoma scheduled for cystectomy (Cancer Institute of New Jersey, CINJ)