Reactivities of an anti-CEA peptide monoclonal antibody

Synthetic peptides representing different areas of the CEA molecule were used as immunogens for the development of anti-CEA antibodies. Both polyclonal and monoclonal antibodies were generated using peptides composed of CEA amino acid positions 99–128 and 585–613, respectively. One MAb, designated CP4, generated using the CEA peptide 99–128, was chosen for a more detailed analysis of reactivity. MAb CP4 reacts in solid phase RIAs with CEA peptide 99–128 immunogen and purified native CEA. CP4 did not react with purified non- specific cross reacting antigen (NCA), even though there were two single amino acid differences between NCA and CEA in the 29 amino acid peptide. The affinity constants of CP4 for the CEA peptide 99–128 and native CEA are 4.07 × 109M−1and 5.75 × 108M−1, respectively. When CP4 was reacted with purified CEA in Western blotting experiments, the Mr 180,000 glycoprotein characteristic of CEA was detected, but CP4 reacted to various size entities in tumor cell extracts. The results of liquid competition RIAs showed that the epitope that MAb CP4 recognized on native CEA is not available for binding when CEA is in solution. Physical (adsorption to a solid matrix) or chemical (deglycosylation or formalin-fixation) alteration of CEA is required for binding of CP4 to CEA. MAb CP4 reacted approximately 1,000-fold greater to deglycosylated CEA than native CEA. Immunohistochemical studies using formalin-fixed paraffin-embedded tissue sections demonstrated that, among carcinomas, CP4 reacts selectively with colorectal carcinomas, while normal colon is negative. Although stomach carcinoma is negative, dysplastic lesions and areas of intestinal metaplasia are reactive. Two of 7 normal stomach tissues showed focal cytoplasmic reactivity of the surface epithelium. CP4, therefore, appears to react with an epitope with highly restricted expression in colorectal carcinoma. These studies demonstrate the complexities in dealing with an anti-peptide MAb with reactivity to an epitope which is accessible only under certain conditions.

Abstract OT3-04-01: Nivolumab or capecitabine or combination therapy as adjuvant therapy for triple negative breast cancer (TNBC) with residual disease following neoadjuvant chemotherapy: The OXEL study

Background: Long-term follow-up of neoadjuvant studies demonstrates poor clinical outcomes in patients with TNBC who do not achieve pathologic complete response, with only 35% remaining free of recurrence at 10 years. The addition of adjuvant capecitabine in the CREATE-X study prolonged disease free survival and overall survival (OS) in patients with HER2 negative breast cancer with residual invasive disease, with more striking benefit in patients with TNBC. Checkpoint inhibitors have not been approved in breast cancer yet, but recent studies suggest a benefit in combination with chemotherapy and low burden of disease. In the current study, we will evaluate the role of chemoimmunotherapy in the adjuvant setting for patients with TNBC with residual disease after neoadjuvant therapy. We will also investigate the role of the peripheral immunoscore (PIS) in predicting the benefit of immune checkpoint inhibition with or without chemotherapy.

Trial design: OXEL is a pilot open-label three arm randomized study of nivolumab, capecitabine or the combination as adjuvant therapy for 45 patients with residual TNBC after adequate neoadjuvant chemotherapy. Patients enrolled will be randomly assigned to 1 of 3 treatment arms: nivolumab 360 mg iv q3weeks for x 6 cycles; capecitabine 1250mg/m2 po bid D1-D14 q3 weeks x 6 cycles; nivolumab 360mg iv q3weeks + capecitabine 1250mg/m2 po bid D1-D14 q3 weeks x 6 cycles.

Main eligibility criteria: Patients ≥18 years of age with TNBC and ≥1cm of residual disease in the breast and/or node positive disease; receipt of neoadjuvant taxane +/- anthracycline, or platinum, and having completed definitive resection of primary tumor, with no prior use of capecitabine, fluorouracil or immunotherapy, and with no active autoimmune disease or chronic use of systemic steroids.

Specific aims: The primary endpoint is assessing the immunologic effects of capecitabine, nivolumab or the combination in the adjuvant setting by PIS. Additional endpoints include toxicity assessment, distant recurrence free survival (DRFS) and OS at 3-years, association between changes in PIS and circulating tumor DNA at different timepoints with clinical outcome variables and characterization of the immune contexture in residual tumors.

Statistical methods: The study is designed to assess the change in PIS at 6 weeks from baseline in each arm. The sample size of 15 per arm (45 total for 3 arms) will provide preliminary results. A sample size of 15 per arm will have 85% power to detect an effect size of 1 (the difference of the change in PIS from baseline to week 6 between two arms divided by the standard deviation) at 5% significance level.

Present accrual and target accrual: The Institutional Review Board at Georgetown University Medical Center has approved the study. Clinicaltrials.gov NCT03487666. Enrollment of the first patient is expected in July 2018 with a total of 45 patients planned to be recruited. Recruitment sites are MedStar Georgetown University Hospital, MedStar Washington Hospital Center, Hackensack University Medical Center. This trial is supported by Bristol-Meyers Squibb, P30CA051008-25 from NCI, Inivata and the Nina Hyde Center for Breast Cancer Research.

Citation Format: Khoury K, Isaacs C, Gatti-Mays ME, Donahue RN, Schlom J, Wang H, Gallagher C, Graham D, Warren R, Dilawari A, Swain SM, Pohlmann PR, Lynce F. Nivolumab or capecitabine or combination therapy as adjuvant therapy for triple negative breast cancer (TNBC) with residual disease following neoadjuvant chemotherapy: The OXEL study [abstract]. In: Proceedings of the 2018 San Antonio Breast Cancer Symposium; 2018 Dec 4-8; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2019;79(4 Suppl):Abstract nr OT3-04-01.

Potential for Artifacts in Monitoring for the Detection of Tumor Associated Antigens (TAG-72 and CEA) in Serum from Patients Undergoing MAb-based Diagnostic and Therapeutic Protocols

The administration of murine monoclonal antibodies (MAbs) induces, in many patients, an immunological response represented by the development of human anti-mouse antibodies (HAMA). HAMA have been previously shown to interfere in some assays for the detection of CEA, as well as other non tumor related analytes. The present study was performed to determine whether the CA 72-4 assay is affected by the presence of HAMA, and to establish conditions capable of overcoming this artifact. Serum samples obtained from 8/9 patients entered into a therapeutic protocol using 131I-labeled MAb B72.3 showed the development of apparently high levels of TAG-72 during the clinical follow-up concurrent with the appearance of elevated titers of HAMA. Heat treatment at 90°C at pH 5.0 sodium acetate, previously reported as a method of abolishing HAMA interference without affecting CEA levels, resulted in a considerable loss of detectable TAG-72. However, treatment of these samples at 90°C in pH 6.5 Bis Tris abolished the artifact due to HAMA and resulted in the reversion of reported TAG-72 levels to those observed prior to any MAb administration.

As the use of murine M Abs, for both diagnostic and therapeutic applications continues to expand, the identification of this artifactual increase in reported antigen levels due to the development of HAMA has become an important factor in the use of tumor markers, e.g. TAG-72 and CEA, in the follow-up of carcinoma patients.

In Vitro and in Vivo Regulation of Human Tumor Antigen Expression by Human Recombinant Interferons: A Review

The ongoing development of monoclonal antibody technology may eventually lead to the selective targeting of human carcinoma lesions by MAbs conjugated with a variety of cytotoxic agents (i.e., radionuclides, drugs, etc.). The antigen phenotype of the carcinoma cell will play an important role in the efficacy of the MAbs. Clearly, the human tumor antigens that are expressed on all carcinoma cells, and with a high antigen density, should provide the optimal target for the MAbs. More often than not, however, the human tumor antigens whose expression is highly selective for human tumor cells will also exhibit a certain degree of heterogeneity. Therefore, the ability of interferon to augment the level of expression of human tumor antigens such as TAG-72 and CEA, may play an important role in an adjuvant setting for immunoscintigraphy and/or immunotherapy. More recent observations have demonstrated that interferon treatment can also enhance the amount of TAG-72 and CEA secreted by the tumor cell. The ability of interferon to enhance the shedding of both TAG-72 and CEA could be of particular importance since recent reports suggest that their presence in the sera of patients diagnosed with gastrointestinal adenocarcinoma may be complementary and that the ability to increase either marker may facilitate earlier diagnosis of recurrent disease. It is conceivable that in subsequent years effective approaches to monitoring and/or treating malignacies may include a new combination of biological/immunological therapy.

Molecular Profile, Tissue Distribution and Prognostic Evaluation of a Human Melanoma-Carcinoma Antigen Recognized by the Murine Monoclonal Antibody B1.1

Using the murine monoclonal antibody (MoAb) B1.1 we have analyzed the immunochemical profile and the tissue distribution of a human melanoma associated antigen (MAA) carrying an epitope shared by the 180 kd CEA. Results of this study have demonstrated that the epitope expressed by the MAA is carried by a distinct set of molecules of 110-140 kd. Similarly to the 180 kd CEA molecules synthesized by carcinomas, the expression of the melanoma associated CEA like components (MA-CEA) is upregulated by IFN-α. The tissue distribution of MA-CEA is not restricted to malignant primary and metastatic melanocytic lesions but is found also at low levels in 64% of benign nevi. No circulating CEA was found in patients bearing widespread metastatic disease of MA-CEA positive lesions.

Preliminary clinical evaluation of stage I melanoma patients bearing MoAb Bl. l positive lesions has not shown a significative prognostic association of this phenotypic marker with clinical course of the disease.

Complementation of Expression of Carcinoembryonic Antigen and Tumor Associated Glycoprotein-72 (TAG-72) in Human Colon Adenocarcinomas

Enzyme-labeled monoclonal antibodies (MAbs) were used in an immunohistochemical, dual-staining study of 10 colon adenocarcinomas. MAbs B72.3 and COL-4, reactive with the high molecular weight tumor-associated glycoprotein-72 (TAG-72) antigen and carcinoembryonic antigen (CEA), respectively, were labeled with horseradish peroxidase or alkaline phosphatase. Dual staining using the two MAbs on a single tissue section (formalin-fixed, paraffin-embedded) showed that greater numbers of carcinoma cells could be detected by using the combination of the two MAbs than could be detected by use of either MAb alone. In many tumors, some carcinoma cells reacted with MAb B72.3, some reacted with MAb COL-4, and some cells reacted with both MAbs. Only 1 of 10 carcinomas showed > 75% reactive cells when stained with each MAb individually. In 9 of 10 cases, however, > 75% of cells reacted when the combination of MAbs was used. Cell surface and cytoplasmic patterns of reactivity were observed with both MAbs while some pools of extracellular mucin were composed of both TAG- 72 and CEA. This study supports the rationalefor the use of a combination of anti-TAG-72 and anti-CEA MAbs for in vitro immunologic detection and potential in vivo immunodiagnostic and immunotherapeutic applications for these MAbs in colon adenocarcinoma patients.

Abstract P3-05-04: An IL-15 superagonist enhances antibody-dependent cell-mediated cytotoxicity against breast cancer cells regardless of FCGR3A (CD16) genotype and rescues NK cell from TGF-β1-induced immunosuppression

It has been reported that the Natural killer (NK) cell with FCGR3A (CD16a) V genotype is associated with enhanced clinical response to IgG1 monoclonal Ab (mAb) therapy such as trastuzumab, rituximab and cetuximab (1,2), suggesting a role of antibody-dependent cell-mediated cytotoxicity (ADCC) induced by NK cells. NK cells express three types of polymorphism of CD16; FcγRIIIa-158 VV, VF, FF, which are derived from the genotype of FCGR3A. It is a clinical challenge to improve the outcome in patients with FCGR3A 158FF genotype whose NK cells have lower affinity to mAb and mediate poor ADCC activity. The IL-15 superagonist/IL-15Rα-Fc fusion complex (ALT-803) activates the IL-15 receptor on CD8 T cells and NK cells, inducing their expansion, cytotoxity, and ADCC against B cell lymphoma (3, 4, 5).

Here, we examined the effect of ALT803 on NK cell-mediated ADCC activity by the the anti-HER2 IgG1 mAb trastuzumab in HER2+ cell lines (SKBR3, BT474, MDA-MB-453). In addition, we used the anti-epidermal growth factor receptor(EGFR) IgG1 mAb cetuximab in EGFR positive TNBC cell lines (MDA-MB-231, SUM149, BT549). Finally, we examined the anti-PD-L1 IgG1 mAb avelumab was used for PD-L1 positive breast cancer cell lines (MDA-MB-231, BT549). Trastuzumab, cetuximab, and avelumab all significantly increased NK cell-induced lysis via ADCC. ALT803 significantly further increased both NK induced lysis and ADCC activity in all the cell lines. There was a significant positive correlation for the mean of ADCC lysis induced by NK cells from three FF (21%), three VF (33%), three VV (45%) donors. ALT803 significantly increased the mean of ADCC lysis by NK cells from all donors of each genotype to the same extent. ALT803 increased the expression of NK cell-activating receptors and cytotoxic granules regardless of the genotype of NK cell FCGR3A in terms VV, VF, or FF.

We further examined the potential of ALT803 for NK cell-cytotoxicity suppressed by TGF-β1 which is one of the main barriers to immunity in the tumor microenvionment (TME). NK cells treated with TGF-β1 showed lower expression of activating receptors and cytotoxic granules, culminating in decreased lysis of MDA-MB231. ALT803 inhibited TGF-β1 from down-regulating the expression of NK cell-activating receptors and cytotoxic granules, and from suppressing the cytotoxicity of NK cells to MDA-MB231.

In conclusion, the IL-15 superagonist ALT803 can potentially increase the clinical benefit of ADCC-based mAb therapy for breast cancer patients, regardless of the genotype of FCGR3A. Moreover, ALT803 prevented NK cell-cytotoxity from TGF-β1-induced suppression, providing a rationale for ALT803 therapy to overcome TME-mediated immunosuppression.

References

(1) Gavin et. al. JAMA Oncol.2017;3(3)

(2) Musolino et. al. J Clin Oncol.2008;26(33)

(3) Xu et. al. Cancer Res.2013;73(10)

(4) Kim et. al. Oncotarget.2016;7(13)

(5) Rosario et. al. Clin. Cancer Res. 2016; 22(3)

Citation Format: Fujii R, Wong HC, Schlom J, Hodge JW. An IL-15 superagonist enhances antibody-dependent cell-mediated cytotoxicity against breast cancer cells regardless of FCGR3A (CD16) genotype and rescues NK cell from TGF-β1-induced immunosuppression [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P3-05-04.

Sequences related to the RNA tumor viruses in the RNA and DNA of human leukemias and lymphomas

DNA-RNA hybridization was used to explore whether human neoplasias contain RNA molecules having sequence homologies to those of the RNA tumor viruses known to cause similar diseases in animals. The pattern of specific RNAs found in the human tumors showed a remarkable concordance with the predictions deducible from the animal systems. Thus human breast cancer contains RNA homologous only to that of the murine mammary tumor virus (MMTV). Human leukemias, sarcomas, and lymphomas (including Hodgkin's and Burkitt's) all contain RNA with sequence homology to the murine leukemia virus (RLV) and not to MMTV RNA. Finally, as in the case of the mouse, none of the human tumors examined contain RNA related in sequence to that of the avian myeloblastosis virus (AMV). The RNA detected in all of the human neoplasias was demonstrated to be of high molecular weight (1 times 10(7) daltons) and encapsulated with a reverse transcriptase in particles having densities between 1.16-1.19 g/ml. Further, the RNA of these human tumor particles was related in sequence to the murine viruses that cause the corresponding neoplasias in mice. Thus, 4 features diagnostic for the murine oncogenic viruses are satisfied by the particles found in the human cancers. Finally, it was shown by "recycling" experiments that the DNA from human leukemic cells and from lymphomatous tissue contained particle-related sequences that could not be detected in normal DNA. This finding was further substantiated by studies with identical twins in which it was shown that the leukemic twin contained particle-related sequences that could not be detected in the leukocytes of his identical healthy sibling. These findings are inconsistent with hypotheses that require chromosomal transmission in the germ line of complete copies of the information required to produce malignancy and the associated virus particles.

Evidence for an RNA tumor viruses in human milk

Certain human milks have been shown to contain particles that have the biochemical and biophysical properties that are diagnostic of the known RNA tumor viruses of animals. These properties include 1) a particle density of 1.16-1.19 g/ml 2) a viral reverse transcriptase (RNA-directed DNA polymerase), and 3) a high molecular weight (HMW) 60-70S RNA that contains polyadenylic regions of 200 nucleotides in length. Inner cores, or nucleoids, of these particles have been isolated. They have a density of 1.26-1.27 g/ml and contain the viral reverse transcriptase and 60-70S RNA. Using molecular hybridization, a specific homology was demonstrated between radioactive DNA synthesized from the RNA of the human milk particle and the RNA from human malignant breast tumors. RNA from benign breast tumors and other human tissues were negative in these tests.

Abstract P5-16-06: A phase 2 randomized trial of docetaxel (DOC) alone or in combination with therapeutic cancer vaccine, CEA-, MUC-1-TRICOM (PANVAC)

Background: A previous phase 1/2 trial of PANVAC, a poxviral based cancer vaccine, suggested clinical efficacy in some patients (pts) with breast and ovarian cancer and evidence of immunologic activity. Preclinical data showed DOC can modify tumor phenotype, making tumor cells more amenable to T-cell mediated killing. The goal was to determine if DOC and PANVAC could synergize and improve clinical outcomes compared with DOC alone.

Methods: This is an open-label randomized phase 2 multi-center trial designed to enroll 48 pts with metastatic breast cancer to receive DOC in combination with PANVAC (A) or alone (B). Cross-over was allowed so that pts randomized to B could receive the vaccine upon progression. Eligibility included ECOG performance status <1 and normal organ and immune function with no limits on previous lines of therapy, but pts may not have received DOC for metastatic disease. Her2+ pts on trastuzumab were allowed to continue trastuzumab on trial. All pts received DOC 35mg/m2 weekly × 3 doses during 28-day cycles. Pts on A were “primed” with recombinant vaccinia-PANVAC study day 1. Three weeks later, they began 28-day cycles of DOC with “boost” recombinant fowlpox-PANVAC given on day 1, given until progression. CT and bone scans were performed after 3 cycles and then every 2 cycles. 1° endpoint was PFS., with a phase 2.5 statistical design, with the intent of identifying a trend toward benefit to guide a larger trial design. A p value of 0.10 is considered a strong trend. 2° endpoints included overall survival and immunologic correlative studies. Immunologic assays included analysis of T cell and NK cell activation, presence and activity of regulatory T cells, and ELISPOT assays. Immune correlative analysis was done using multiparametric flow cytometry analysis of immune cell subpopulations from peripheral blood mononuclear cells (PBMCs) of pts and comparing those findings using Boolean logic with the immune assays and clinical outcomes.

Results: Enrollment of 48 pts completed in February 2012 (A, n=25; B, n=23). Five pts remain on treatment (2 on A, 3 on B). Pt and tumor characteristics were well matched. Analysis through August 2, 2012 (median follow-up of 5.1 months for pts on study), indicates PFS is 6.6 vs. 3.8 months in A vs. B (p = 0.12, HR=0.67, 95% CI: 0.34 to 1.31). Analysis of the adverse events on both arms demonstrated very little difference between the two groups. The only statistically significant differences were increases in the frequency of grade 1 and 2 edema (p = 0.018) and injection site reactions (p <0.0001) in the combination arm. Immune analysis and correlation to pt clinical outcomes are ongoing and will be available for presentation at the time of the meeting. There are not yet enough events to perform a comparison of overall survival in the two groups.

Conclusion: This randomized study suggests the combination of PANVAC with DOC in metastatic breast cancer may provide a clinical benefit compared to DOC alone. The clear separation of the curves indicates potential benefit, which is not statistically significant, likely due to the small number of pts enrolled. This study was hypothesis generating and may provide both rationale and statistical assumptions for a larger definitive randomized study.

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P5-16-06.

Impact of tumour volume on the potential efficacy of therapeutic vaccines

With the recent approval by the U.S. Food and Drug Administration of the first therapeutic vaccine for cancer, the long-awaited goal of harnessing a patient's immune system to attack cancer through this modality is finally realized. However, as researchers in the field of cancer immunotherapy continue to perform randomized definitive studies, much remains to be learned about potential surrogate endpoints and appropriate patient populations for therapeutic vaccines. The present review addresses available data from clinical trials of immunotherapeutic agents relevant to the selection of appropriate patient populations. We believe that the weight of evidence supports the use of immunotherapy earlier in the disease course and in patients with less aggressive disease, and that the relevant findings have important implications for the design of clinical trials with therapeutic vaccines.

Long-term follow-up of prostate cancer patients treated with vaccine and definitive radiation therapy

BACKGROUND

Vaccine therapy in combination with radiation therapy may improve distant and/or local control in prostate cancer. We present long-term follow-up data on the secondary and exploratory endpoints of safety and biochemical failure, respectively, from patients with clinically localized prostate cancer treated definitively with a poxviral vector-based therapeutic vaccine combined with external beam radiation therapy (EBRT).

METHODS

Thirty-six prostate cancer patients received definitive EBRT plus vaccine. A total of 18 patients were treated with adjuvant standard-dose interleukin-2 (S-IL-2) (4 MIU m(-2)) and 18 were treated with very low-dose IL-2 (M-IL-2) (0.6 MIU m(-2)). Seven patients were treated with EBRT alone. Twenty-six patients treated with EBRT plus vaccine returned for follow-up, and we reviewed the most recent labs and clinical notes of the remaining patients.

RESULTS

Median follow-up for the S-IL-2, M-IL-2 and EBRT-alone groups was 98, 76 and 79 months, respectively. Actuarial 5-year PSA failure-free probability was 78%, 82% and 86% (P=0.58 overall), respectively. There were no significant differences between the actuarial overall survival and the prostate cancer-specific survival between the two vaccine arms. Of the 26 patients who returned for follow-up, Radiation Therapy Oncology Group grade ≥2 genitourinary (GU) and gastrointestinal (GI) toxicity was seen in 19% and 8%, respectively, with no difference between the arms (P=1.00 and P=0.48 for grade ≥2 GU and GI toxicity, respectively). In all, 12 patients were evaluated for PSA-specific immune responses, and 1 demonstrated a response 66 months post-enrollment.

CONCLUSIONS

We demonstrate that vaccine combined with EBRT does not appear to have significant differences with regard to PSA control or late-term toxicity compared with standard treatment. We also found limited evidence of long-term immune response following vaccine therapy.

A randomized phase II study of flutamide with or without PSA-TRICOM in nonmetastatic castration-resistant prostate cancer (CRPC)

163

Background: PSA-TRICOM is a vector-based, therapeutic cancer vaccine regimen consisting of recombinant poxviruses containing the transgenes for prostate-specific antigen (PSA) and 3 T-cell co-stimulatory molecules (TRICOM). A previous randomized, placebo-controlled phase II study demonstrated an 8.5-month improvement in median survival (25.1 months for PSA-TRICOM group vs. 16.6 months for control group) in men with metastatic CRPC.

Methods: This study is currently enrolling patients with non-metastatic CRPC on testosterone suppression therapy who have a rising PSA. Patients are stratified by PSA doubling time and randomized to androgen receptor antagonist alone (flutamide) or flutamide plus PSA-TRICOM. Flutamide is given at the standard dose of 400 mg TID while PSA-TRICOM is given by monthly subcutaneous injections. The primary endpoint of the study is time to treatment failure (TTF) which is defined as biochemical recurrence (PSA rise) or development of metastatic lesions on scans.

Results: The first 26 patients enrolled are evaluated in this analysis. For flutamide alone (n = 13), the median age at enrollment was 64.7 years and median Gleason Score was 8. For flutamide + PSA-TRICOM (n = 13), the median age at enrollment was 67.1 years and median Gleason score was 8. Median time to progression is 223 days for Fluatmide + PSA- TRICOM (range 70-638) vs. 85 days for Flutamide alone (56-372). Progression for 11/12 flutamide alone patients and 9/10 fluatmide + PSA-TRICOM patients has been by PSA rise only.

Conclusions: Preliminary evidence suggests improvement in time to treatment failure using combination of hormonal therapy with flutamide + PSA-TRICOM vaccine compared to fluatmide alone in patients with non-metastatic CRPC. This trial will continue to accrue a total of 62 patients and also will evaluate immunological responses.

No significant financial relationships to disclose.

Intraprostatic vaccine administration in patients with locally recurrent prostate cancer

141

Background: PSA-TRICOM is a cancer vaccine consisting of recombinant poxviruses with transgenes for PSA and 3 T cell costimulatory molecules (TRICOM). A multicenter randomized vector controlled phase II study showed an 8.5 month improvement in median survival in men with metastatic CRPC. Preclinical studies showed intratumoral administration of TRICOM vaccines may improve anti-tumor outcomes. This study was intended to show safety of intraprostatic (i.p.) vaccine administration. 2° goals included immunologic and tumor response.

Methods: 21 pts were enrolled with locally recurrent prostate cancer after radiation into 5 cohorts and received initial vaccination with s.c. recombinant vaccinia (rV)-PSA-TRICOM and booster i.p. recombinant fowlpox (rF)-PSA-TRICOM. Cohorts 3-5 also received i.p. rF-GM-CSF. Cohort 5 received concurrent s.c. and i.p. boosters. Priming was given on day 1, and boosters were given on days 29, 57, and 85. Pts had pre- and post-treatment prostate biopsies. Tumor infiltrate was evaluated when adequate tissue was available. PBMCs were analyzed by ELISPOT for response to PSA and 3-color flow cytometry to characterize regulatory T cells (Treg) or effector T cells. Treg suppression function was assayed by suppression of the CD4+ effector T cell proliferation.

Results: Only 1 grade 3 toxicity occurred, a transient fever. Most common grade 2 adverse events for all doses were fever (14.5%) and injection-site reactions (21%). 15 of 21 pts had stable or improved PSA on study, and 16 of 21 pts had stable or improved PSA doubling time. Post-vaccination, 4 of 8 evaluable pts had immunological response by ELISPOT assay and 11 of 15 pts had decreased (n=8) or stable (n=3) Treg function. A paired t-test of 13 biopsies pre- and post- vaccination showed significant increases in immune infiltrates within tumors after vaccination. CD4+ cells increased from 1.3 → 13.1/high power field (hpf). CD8+ cells rose from 6.4 → 14/hpf.

Conclusions: I.p. administration of PSA-TRICOM is safe, feasible and can generate a substantial immunologic response. Improved PSA kinetics and intense post-vaccination immune infiltrates were seen in the majority of pts. Trials of i.p. PSA-TRICOM examining clinical endpoints are warranted.

No significant financial relationships to disclose.

Role of vaccine therapy in cancer: biology and practice

Vaccines constitute a potential new therapeutic approach for a range of human cancers. Unlike other therapeutics, vaccines initiate a dynamic process in the host immune system that can be exploited with subsequent therapies. Indeed, recent preclinical and clinical studies with cancer vaccines have provided evidence that this unique therapeutic modality should lead to consideration of new paradigms in both clinical trial design and endpoints and in combination therapies. The present article reviews and sets out a rationale for these new paradigms, with a focus on prostate cancer.

Overall survival (OS) analysis of a phase II randomized controlled trial (RCT) of a poxviral-based PSA targeted immunotherapy in metastatic castration-resistant prostate cancer (mCRPC)

5013

Background: Therapeutic poxviral vaccines for prostate cancer are safe with preliminary evidence of clinical benefit in phase I/II studies. PROSTVAC-VF (PV) comprises 2 recombinant viral vectors (Vaccinia and Fowlpox), each encoding transgenes for prostate specific antigen (PSA) and 3 immune costimulatory molecules (B7.1, ICAM-1, and LFA3: TRICOM). PV is administered subcutaneously in a heterologous prime-boost regimen with concurrent low-dose GM-CSF. Methods: 122 patients (pts) were treated in a multi-center, double-blind, RCT of a vaccination series. Pts were randomized 2:1 to PV + GM-CSF vs. placebo empty vector + control saline injections (C). Vaccinia-based vector was used for priming followed by 6 planned Fowlpox-based vector boosts. The trial completed enrollment in July 2005. Eligible pts had metastatic disease, a rising PSA despite castrate testosterone levels, and a Gleason score of ≤7. Pts with a history of prior chemotherapy use, visceral metastasis, or narcotic use were excluded. The 1º endpoint was progression free survival (PFS), with progression defined as 2 new lesions on bone scan or RECIST-defined progression. Vaccination was discontinued after progression. Results: 82 pts received PV and 40 received C. Pt characteristics were similar (means): age (72PV/76C), PSA (134PV/188C), Alk-Phos (142PV/159C), LDH (207PV/218C), Hgb (13PV/13C), and number bone metastatic sites (5.3PV/6.5C). Mean number of vaccinations was 5.4 PV and 5.3 C. PFS was similar in the 2 groups (p = 0.56). However, at 3 years post study, PV patients had a better overall survival than C patients (25 alive, 30%, PV, versus 7 alive, 17%, C) and a longer median survival (24.5 months PV, versus 16 months C); estimated hazard ratio 0.6 (95% CI 0.4–0.9); stratified log rank p = 0.016. Conclusions: In a RCT, PV immunotherapy was associated with an 8.5 month improvement in median OS in men with mCRPC. These data provide evidence of prolonged anti-tumor activity, but need to be confirmed in a larger phase III study.

[Table: see text]

Phase I trial of targeted therapy with PSA-TRICOM vaccine (V) and ipilimumab (ipi) in patients (pts) with metastatic castration-resistant prostate cancer (mCRPC)

5144

Background: There are few treatment options for mCRPC pts. Immunotherapy + adjuvant immunomodulators is a promising modality. PSA-TRICOM V is composed of poxviral vectors encoding PSA and 3 costimulatory molecules (ICAM-I, LFA-3, and B7.1) and has clinical activity in mCRPC. Ipi blocks CTLA-4, a T-cell downregulatory receptor, has clinical activity in mCRPC as monotherapy and has also been shown to enhance anti-tumor responses in combination with V in preclinical studies. Methods: Pts received V and GM-CSF q 4 weeks in 4 sequential cohorts of escalating doses of ipi at 1, 3, 5, and 10 mg/kg (DL1–4 respectively). After 6 courses of ipi, pts could receive a maintenance dose q 3 months (mo) until progression. Results: Study accrual is complete with 30 pts. There was no DLT and no > G2 adverse event (AE) attributed to V. There were 20 ≥ G2 immune-related AE (irAE): 0/3, 2/6, 5/6 and 13/15 pts on DL1–4, respectively. There was no evidence of clinical benefit in the 6 pts who had prior chemo on DL1 and 2, so subsequently we excluded pts with prior chemo. Median TTP for 9 chemo-naïve pts treated on DL2 and 3 was 6.1 mo (2.9–11.6 mo). Median PSA doubling time (DT) ↑ from 2.2 mo at baseline to 3.7 on study (p = 0.17). 5 of 9 had ≥ 50% ↓ in PSA from peak during study and 1 had a sustained ↓ PSA > 95% from baseline. 4 of these pts had stable disease (SD) for ≥ 6 mo and 2 had unconfirmed partial responses by RECIST. Of the 15 pts on DL4, to date 9 have had SD for ≥ 6 mo (2 ≥ 12 mo); 4 remain on trial. 1 had a sustained ↓ in PSA > 99% from baseline and is still on study after 12 mo. Median PSA DT ↑ > 3-fold from 2.6 mo at baseline to 8.2 on study (p = 0.01) in DL4. The 24 chemo-naïve pts had PSA DT ↑ from 2.5 to 6 mo (p = 0.003). 14 of 30 pts had a PSA ↓ from baseline or peak PSA on study. 2 of 14 had no irAE, 12 showed ≥ G2 irAE temporally associated with PSA ↓. 5 of 9 pts had > 2–5 fold ↑ in T-cell responses by ELISPOT assay and 4 of 13 had significant ↓ in their IL-6 levels. Immune responses appeared to correlate with clinical activity. Conclusions: This combination has clinical activity in pts with chemo-naïve mCRPC and seems to correlate with immune responses. It is associated with manageable side effects; however, further studies are required to see if the combination is more effective than either agent alone.

No significant financial relationships to disclose.

Five-year overall survival (OS) in non-metastatic androgen-independent prostate cancer (AIPC) patients (pts) treated with nilutamide (N), vaccine (V), and combination therapy

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Introduction: There is no standard treatment for pts with non-metastatic AIPC (D0.5).We previously performed the first randomized study in this pt population involving N,V, and combination therapy. To our knowledge this report is the first prospective analysis of OS data in pts with stage D0.5 AIPC. Methods: The initial study randomized 21 pts to treatment with N and 21 pts to treatment with V. The V was an admixture containing a vaccinia vector with the gene for PSA combined with vaccinia containing the costimulatory molecule B7.1. As part of this V strategy, pts also received monthly boosts of fowlpox-PSA with GM-CSF and IL-2 with all vaccinations. Pts who developed rising serum PSA levels on either arm could cross-over to receive both V and N. Initial data demonstrated a clinical benefit in pts treated with combination V and N. Pts characteristics were reviewed and OS was determined using the social security death index. Actuarial analyses of the data using the Kaplan-Meier method were performed. Results: The OS from on-study date in all randomized pts was 4.6 years (yrs) with 3yr OS=71% and 5yr OS=48%. There was no difference in OS in all pts based on Gleason Score (GS) or PSA at diagnosis (dx), orchiectomy, radical prostatectomy, or radiation therapy. However, a subgroup analysis showed a trend to improved OS for pts treated with V alone or V+N (compared to N alone or N+V), who had GS <7 (p=0.18), PSA<20 (p=0.077), and PSA doubling time<3 months (p=0.14). Comparing OS in the study arms: Conclusion: Although these results were not statistically significant due to small cohort sizes, there was a clear trend in both 3yr and 5yr OS in the pts who received V first and crossed-over to V+N, as compared with the reciprocal scheduling of N followed by N+V. A randomized trial at the NCI will compare androgen deprivation therapy (ADT) alone vs ADT plus vaccine to further study the benefits of combination therapy in this population.

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No significant financial relationships to disclose.

A randomized pilot study of concurrent docetaxel plus vaccine versus vaccine alone in metastatic androgen independent prostate cancer

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Background: Docetaxel has activity against androgen insensitive prostate cancer (AIPC) and preclinical studies have demonstrated that taxane-based chemotherapy can enhance antitumor response of vaccines. The primary objective of this study was to determine: if concurrent docetaxel (with dexamethasone) had any effect on generating an immune response to a prostate cancer vaccine in patients with metastatic AIPC; secondary endpoints werewhether vaccine could be given safely with docetaxel, and the clinical outcome of the treatment regimen. Methods: The vaccination regimen was composed of (1) recombinant vaccinia virus (rV) that expresses the prostate-specific antigen gene (rV-PSA) admixed with (2) rV that expresses the B7.1 costimulatory gene (rV-B7.1), and (3) sequential booster vaccinations with recombinant fowlpox virus containing the PSA gene (rF-PSA). Patients received GM-CSF with each vaccination. Twenty-eight patients with metastatic AIPC were randomized to receive either vaccine and weekly docetaxel or vaccine alone. Patients on the vaccine alone arm were allowed to cross over to receive docetaxel alone at time of disease progression. An ELISPOT assay for IFN-gamma production was used to monitor immune responses for PSA-specific T cells. Results: The median increase in these T-cell precursors to PSA was 3.33-fold in both arms following 3 months of therapy. In addition, immune responses to other prostate cancer associated tumor antigens were also detected post-vaccination. Eleven patients who progressed on vaccine alone crossed over to receive docetaxel at time of progression. Median PFS on docetaxel was 6.1 months after receiving vaccine compared to 3.7 months with the same regimen in a historical control. Conclusions: This is the first clinical trial to demonstrate that docetaxel can be administered safely with immunotherapy, and without inhibiting vaccine specific T-cell responses. Furthermore, patients previously vaccinated with an anticancer vaccine may respond longer to docetaxel compared with a historical control of patients receiving docetaxel alone. Larger prospective clinical studies will be required to validate these findings.

No significant financial relationships to disclose.

Randomized single institute pilot study of vaccinia-CEA(6D)-tricom and fowlpox-CEA (6D)-tricom with GM-CSF (V) in combination with docetaxel (D) in patients with colorectal cancer (CC)

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Background: Our previous study demonstrated 40% patients with CC achieved stable disease at 4 months with V (JCO, 23(4):720–31, 2005.). Preclinical studies showed taxene enhanced tumor vaccine in delaying tumor growth and increasing the antigen-specific T cells. We report the results of a Randomized phase II pilot study of V in combination with docetaxel (D) in CC patients. Methods: 27 patients with metastatic CC were randomly assigned to 3 arms, stratified for HLA-A2. All patients received a ‘prime’ dose of vaccinia-Tricom on Day 0, followed by ‘boost’ doses of fowlpox-Tricom on Days 21 and q 21 days for 4 months; all vaccinations were followed by local GM-CSF (100 μg) for 4 days. Arm 1 received V; Arm II and III received V and D on D1, D8 during each fowlpox vaccination at 10mg/m2 and 30mg/m2, respectively. Patients with stable disease continued vaccinations monthly after study completed. Safety data was evaluated. Primary endpoints included the impact of varying doses of D on CEA-specific T cell immune responses (CTL) using the ELISPOT assay, the recommended dose for further study as defined by the best immune response with acceptable toxicity, and objective clinical response. Results: The most common AE related to the vaccines was grade (g) 1 injection site reactions. Other common AEs were g1 fatigue, nausea, vomiting, fever, headache, and myalgia. There were 1 g3 fever and 1 g3 abdominal pain. The AE from the combination arm were contributed by D as expected, included g3: hyperglycemia (1), fatigue (1), elevation of liver function tests (2), pulmonary infection (1), abdominal pain (1), vomiting (1) or diarrhea (1). 6/ 27 patients have died 17 months after starting V. Patients received 2 to 12 cycles of therapy before disease progression. Observed clinical benefit was significantly lower than the 40% previously documented with V alone. The immune data is to be presented. Conclusions: Inferior clinical benefit as compared to our previous experiment could be explained by more heavily pretreated patients in this trial or negative impact of D on V. CTL data should explain this observation.

No significant financial relationships to disclose.

A pilot study of a PANVAC-V and PANVAC-F in patients (pts) with metastatic carcinoma

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Background: The vast majority of carcinomas express either MUC-1 or CEA. Preclinical and clinical studies have demonstrated that induction of T-cell responses directed against CEA and MUC-1 can lead to anti-tumor activity without toxicity. Two novel vaccines have been developed: (a) PANVAC-V (V) a recombinant vaccinia virus containing CEA and MUC-1 with modified agonist epitopes and 3 costimulatory molecule transgenes, and (b) PANVAC-F (F) a similar recombinant fowlpox virus. Methods: This pilot study enrolled 25 pts with metastatic carcinoma who had progressive disease after chemotherapy. Pts received V priming followed by F boosts every 2 weeks × 3 then monthly with restaging scans every 2 months while on study. All vaccines were given with sargramostim at the vaccine site. The primary endpoint was safety. Class I and class II immune responses to CEA were analyzed. Class I responses were assayed by ELISPOT, intracellular cytokine, and tetramer binding; and class II responses were assayed by ELISA using CEA protein and class II peptides. Results: Treatment was well tolerated with 135 cycles given. Only one grade 3 toxicity (syncope during a flu-like illness) was possibly related to vaccine. Apart from injection site reactions, only 9 cycles (7%) were associated with transient grade 2 toxicity (generally flu-like syndromes). Class I and class II immunologic responses were demonstrated. A pt with metastatic breast cancer and 5 large liver metastasis had a 24% decrease in unidimensional measurement of disease for 6 months. A pt with metastatic gastric cancer had stable disease for 5 months. Furthermore, a pt with metastatic clear cell ovarian cancer s/p chemotherapy had complete disappearance of large volume, symptomatic ascites accompanied by marked improvement in the appearance of mesenteric stranding and a CA-125 reduction from 281 U/mL to continued sustained normal values (< 20 U/mL). Conclusions: This vaccine can be given safely and can generate therapy specific immunologic responses. In addition 1 pt with metastatic ovarian cancer had a dramatic clinical response. Based on this, we have initiated a pilot study specifically for ovarian cancer pts to gain more information on which to base a large clinical endpoint trial.

No significant financial relationships to disclose.

Cancer vaccine development

A new era involving the evaluation of recombinant cancer vaccines has begun with the concurrent emergence of insights and technologies in the fields of molecular biology and immunology. These advances include: The identification and cloning of an array of genes associated with the neoplastic process, such as oncogenes, suppressor genes, genes encoding oncofoetal antigens and tissue-lineage determinants. The development of a variety of viral and bacterial vectors to deliver and present gene products. The identification of numerous T-cell costimulatory molecules and an understanding of their mode of action. The cloning and analysis of the modes of action of an array of cytokines and other immunomodulatory molecules. More sophisticated knowledge of the mode(s) of antigen presentation and T-cell activation. One current challenge in cancer therapy is the delineation of strategies toward the rational design and implementation of recombinant vaccines that will be of therapeutic benefit to cancer patients and/or members of groups at high risk for specific neoplasias. Numerous concepts are emerging in this regard. The study of immunologic intervention using laboratory animal models demonstrates that no one approach will prevail for all cancer types or, perhaps, for the various stages of the neoplastic process of a given tumour type. The immunological role(s) of CD8+, CD4+, natural killer and other cell types, as well as the roles of antibodies, must all be taken into consideration. This article reviews some of the strategies currently undergoing evaluation toward the development of recombinant vaccines for several carcinoma types.

Comparative studies of Avipox-GM-CSF versus recombinant GM-CSF protein as immune adjuvants with different vaccine platforms

Granulocyte-macrophage colony-stimulating factor (GM-CSF) is a potent immune stimulant when administered with different vaccines. Optimal use of GM-CSF resides in its ability to act locally to stimulate the proliferation and maturation of professional antigen-presenting cells (APCs) (i.e., Langerhans' cells) at the injection site. GM-CSF was engineered into a replication-incompetent recombinant avian (fowlpox) virus (rF-GM-CSF) and a single subcutaneous injection resulted in a sustained enrichment of activated dendritic cells within the regional draining lymph nodes. Those changes were attributed to local GM-CSF production at the injection site by rF-GM-CSF-infected cells. Studies were carried out in which mice were administered different types of beta-galactosidase (beta-gal)-based vaccines--whole protein, peptide, recombinant poxviruses--and GM-CSF was administered either as a single injection of rF-GM-CSF or four daily bolus injections of the recombinant protein. The use of rF-GM-CSF either improved the immune adjuvant effect, as observed for poxvirus-based vaccines, or was equivalent to rGM-CSF, as observed with the beta-gal protein vaccine. It is important to note that with either the replication-competent (vaccinia) or replication-incompetent (fowlpox) vaccines expressing LacZ, strong CTL responses directed against beta-gal were induced only when rF-GM-CSF was used as the immune adjuvant. Engineering GM-CSF into a recombinant fowlpox virus offers an excellent vehicle for the delivery of this cytokine as an immune adjuvant with specific vaccine platforms. In particular, delivery of GM-CSF via the rF-GM-CSF construct would be preferred over bolus injections of rGM-CSF when used as an immune adjuvant with whole protein or recombinant poxvirus-based vaccines. The study underscores the importance of defining the appropriate delivery form of an immune adjuvant, such as GM-CSF, relative to the immunization strategy to maximize the host immune responses against a specific antigen.

A triad of costimulatory molecules synergize to amplify T-cell activation in both vector-based and vector-infected dendritic cell vaccines

The activation of a T cell has been shown to require two signals via molecules present on professional antigen presenting cells: signal 1, via a peptide/MHC complex, and signal 2, via a costimulatory molecule. Here, the role of three costimulatory molecules in the activation of T cells was examined. Poxvirus (vaccinia and avipox) vectors were employed because of their ability to efficiently express multiple genes. Murine cells provided with signal 1 and infected with either recombinant vaccinia or avipox vectors containing a TRIad of COstimulatory Molecules (B7-1/ICAM-1/LFA-3, designated TRICOM) induced the activation of T cells to a far greater extent than cells infected with vectors expressing any one or two costimulatory molecules. Despite this T-cell "hyperstimulation" using TRICOM vectors, no evidence of apoptosis above that seen using the B7-1 vector was observed. Results employing the TRICOM vectors were most dramatic under conditions of either low levels of first signal or low stimulator cell to T-cell ratios. Experiments employing a four-gene construct also showed that TRICOM recombinants could enhance antigen-specific T-cell responses in vivo. These studies thus demonstrate the ability of vectors to introduce three costimulatory molecules into cells, thereby activating both CD4+ and CD8+ T-cell populations to levels greater than those achieved with the use of only one or two costimulatory molecules. This new threshold of T-cell activation has broad implications in vaccine design and development. Dendritic cells infected with TRICOM vectors were found to greatly enhance naïve T-cell activation, and peptide-specific T-cell stimulation. In vivo, peptide-pulsed DCs infected with TRICOM vectors induced cytotoxic T lymphocyte activity markedly and significantly greater than peptide-pulsed DCs.

Enhanced activation of rhesus T cells by vectors encoding a triad of costimulatory molecules (B7-1, ICAM-1, LFA-3)

Since the rhesus is often used as a "gatekeeper" model for the evaluation of malaria and simian immunodeficiency virus (SIV)/HIV vaccines, the identification of strategies to enhance the activation of rhesus T cells would potentially aid in the generation of more potent vaccines directed against these infectious agents. Several molecules normally found on the surface of professional human APCs are capable of providing the second signals critical for T cell activation: B7-1 (CD80), ICAM-1 (CD54), and LFA-3 (CD58). With the exception of B7, T cell costimulatory molecules in the rhesus have not been identified. We have recently designed and characterized both recombinant vaccinia and recombinant avipox vectors containing the transgenes for a triad of human T cell costimulatory molecules (B7-1, ICAM-1, LFA-3; designated TRICOM). Here, we demonstrate the enhanced activation of rhesus T cells stimulated with rhesus APCs infected with TRICOM vectors in the presence of signal 1. Infection with TRICOM vectors led to significant improvement of APC capabilities in terms of reduction of the amount of signal 1 needed to activate naive T cells, and reduction in the amount of APCs required to activate T cells using a constant amount of signal 1. Antibody blocking studies demonstrated that each of the three costimulatory molecule transgenes contributed to the enhanced proliferation of T cells. TRICOM-enhanced T cell activation was shown to correspond to increases in type 1 cytokines and a reduced level of apoptosis. TRICOM-infected autologous B cells from rhesus immunized with either an SIV vaccine or a malaria vaccine stimulated significantly greater levels of IFN-gamma in response to specific peptide than stimulation with uninfected autologous B cells or B cells infected with wild-type vector. The ability to augment immune responses using poxvirus-based vaccines containing multiple costimulatory molecule transgenes can now be addressed in the rhesus macaque model.