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Background Before 2018, there was no standard of care for non-metastatic (M0) castration resistant prostate cancer nmCRPC. Androgen receptor antagonists (ARAs) were commonly used sequentially nmCRPC. Methods This was a multicenter, randomized clinical trial comparing the ARA flutamide+/−PROSTVAC, a pox viral vaccine targeting PSA that includes T-cell co-stimulatory molecules. Eligible men had negative CT and Tc99 bone scans, and rising PSA on ADT. Previous treatment with ARA was a stratification factor. Patients were also evaluated for antigen-specific immune responses using intracellular cytokine staining. Results Thirty-three patients randomized to flutamide and 31 to flutamide+vaccine. The median age was 71.8 and 69.8 years, respectively. The median time to treatment failure after a median potential follow-up of 46.7 months was, 4.5 months (range 2-70) for flutamide alone vs. 6.9 months (2.5-40; P = .38) with flutamide+vaccine. Seven patients in each arm had a >50% PSA response. Antigen-specific responses were similar in both arms (58% of patients in flutamide alone and 56% in flutamide+vaccine). The treatments were well tolerated. The most common side effect > grade 2 was injection site reaction seen in 29/31 vaccine patients which were self-limiting. Conclusion The combination of flutamide+PROSTVAC did not improve outcomes in men with nmCRPC compared with flutamide alone. (ClinicalTrials.gov Identifier: NCT00450463)

Background FOLFOX plus bevacizumab is a standard of care (SOC) for first-line treatment of microsatellite-stable metastatic colorectal cancer (MSS mCRC). This study randomized patients to SOC or SOC plus avelumab (anti-PD-L1) plus CEA-targeted vaccine. Methods Patients with untreated MSS mCRC enrolled to a lead-in arm assessing safety of SOC + immuno-oncology agents (IO). Next, patients were randomized to SOC or SOC + IO. The primary endpoint was progression-free survival (PFS). Multiple immune parameters were analyzed. Results Six patients enrolled to safety lead-in, 10 randomized to SOC, and 10 to SOC + IO. There was no difference in median PFS comparing SOC versus SOC + IO (8.8 months (95% CI: 3.3-17.0 months) versus 10.1 months (95% CI: 3.6-16.1 months), respectively; hazard ratio 1.061 [P = .91; 95% CI: 0.380-2.966]). The objective response rate was 50% in both arms. Of patients analyzed, most (8/11) who received SOC + IO developed multifunctional CD4+/CD8+ T-cell responses to cascade antigens MUC1 and/or brachyury, compared to 1/8 who received SOC alone (P = .020). We detected post-treatment changes in immune parameters that were distinct to the SOC and SOC + IO treatment arms. Accrual closed after an unplanned analysis predicted a low likelihood of meeting the primary endpoint. Conclusions SOC + IO generated multifunctional MUC1- and brachyury-specific CD4+/CD8+ T cells despite concurrent chemotherapy. Although a tumor-directed immune response is necessary for T-cell–mediated antitumor activity, it was not sufficient to improve PFS. Adding agents that increase the number and function of effector cells may be required for clinical benefit.

Characterization of rF-brachyury-TRICOM

Supplementary Figures and Tables

Purpose: The transcription factor brachyury has been shown in preclinical studies to be a driver of the epithelial-to-mesenchymal transition (EMT) and resistance to therapy of human tumor cells. This study describes the characterization of a Modified Vaccinia Ankara (MVA) vector–based vaccine expressing the transgenes for brachyury and three human costimulatory molecules (B7.1, ICAM-1, and LFA-3, designated TRICOM) and a phase I study with this vaccine.Experimental Design: Human dendritic cells (DC) were infected with MVA-brachyury-TRICOM to define their ability to activate brachyury-specific T cells. A dose-escalation phase I study (NCT02179515) was conducted in advanced cancer patients (n = 38) to define safety and to identify brachyury-specific T-cell responses.Results: MVA-brachyury-TRICOM-infected human DCs activated CD8+ and CD4+ T cells specific against the self-antigen brachyury in vitro. No dose-limiting toxicities were observed due to vaccine in cancer patients at any of the three dose levels. One transient grade 3 adverse event (AE) possibly related to vaccine (diarrhea) resolved without intervention and did not recur with subsequent vaccine. All other AEs related to vaccine were transient and ≤grade 2. Brachyury-specific T-cell responses were observed at all dose levels and in most patients.Conclusions: The MVA-brachyury-TRICOM vaccine directed against a transcription factor known to mediate EMT can be administered safely in patients with advanced cancer and can activate brachyury-specific T cells in vitro and in patients. Further studies of this vaccine in combination therapies are warranted and planned. Clin Cancer Res; 23(22); 6833–45. ©2017 AACR.

Purpose:The NHS-IL12 immunocytokine is composed of two IL12 heterodimers fused to the NHS76 antibody. Preclinical studies have shown that this antibody targets IL12 to regions of tumor necrosis by binding histones on free DNA fragments in these areas, resulting in enhanced antitumor activity. The objectives of this phase I study were to determine the maximum tolerated dose (MTD) and pharmacokinetics of NHS-IL12 in subjects with advanced solid tumors.Patients and Methods:Subjects (n = 59) were treated subcutaneously with NHS-IL12 in a single ascending-dose cohort followed by a multiple ascending-dose cohort (n = 37 with every 4-week dosing).Results:The most frequently observed treatment-related adverse events (TRAE) included decreased circulating lymphocytes, increased liver transaminases, and flu-like symptoms. Of the grade ≥3 TRAEs, all were transient and only one was symptomatic (hyperhidrosis). The MTD is 16.8 μg/kg. A time-dependent rise in IFNγ and an associated rise in IL10 were observed following NHS-IL12. Of peripheral immune cell subsets evaluated, most noticeable were increases in frequencies of activated and mature natural killer (NK) cells and NKT cells. Based on T-cell receptor sequencing analysis, increases in T-cell receptor diversity and tumor-infiltrating lymphocyte density were observed after treatment where both biopsies and peripheral blood mononuclear cells were available. Although no objective tumor responses were observed, 5 subjects had durable stable disease (range, 6–30+ months).Conclusions:NHS-IL12 was well tolerated up to a dose of 16.8 μg/kg, which is the recommended phase II dose. Early clinical immune-related activity warrants further studies, including combination with immune checkpoint inhibitors.See related commentary by Lyerly et al., p. 9

Background NHS-IL12 is a first-in-class, recombinant fusion protein composed of the human monoclonal antibody NHS76 (binds exposed DNA/histones at sites of intratumoral necrosis) fused to 2 IL-12 heterodimers. The maximum tolerated dose (MTD) and recommended phase II dose (RP2D) of NHS-IL12 monotherapy given subcutaneously (SC) every 4 weeks was previously reported. The study was expanded to include a high-exposure cohort with NHS-IL12 SC every 2 weeks (q2w). Methods This single-arm, phase I trial evaluated NHS-IL12 12 µg/kg SC q2w or 16.8µg/kg SC q2w in patients with metastatic solid tumors. The primary endpoint was safety. Results Using a 3+3 design, 13 patients with advanced cancer were enrolled and 12 were dose-limiting toxicity (DLT) evaluable. There was 1 DLT (Grade 3 aspartate transaminase/alanine transaminase [AST/ALT] elevation). Other grade 3 toxicities included: flu-like symptoms 1/13 (8%), decreased absolute lymphocyte count (ALC) 1/13 (8%), decreased white blood cell count (WBC) 1/13 (8%), but most adverse events reported were low grade and self-limiting grade. Fifty percent of evaluable patients (6/12) experienced stable disease (SD) with 42% (5/12) developing progressive disease (PD) at the first restaging. Conclusion Biweekly NHS-IL12 was well tolerated in this small phase I study. Additional studies incorporating NHS-IL12 with other immunomodulating agents are underway. (ClinicalTrials.gov Identifier: NCT01417546).

5-fluorouracil (5-FU) is an important component of chemotherapy for metastatic colon cancer and can be administered as an intravenous infusion or bolus. Coronary vasospasm is a known complication of infusional and bolus 5-FU administration. In patients who experience coronary vasospasm, 5-FU is often discontinued. Several cases of successful re-challenge with bolus 5-FU, utilizing calcium channel blockers (CCBs) and nitrates to prophylaxis against coronary vasospasm recurrence, have been reported in the literature. However, since there is increased variability of time to symptom onset with infusional 5-FU, re-challenge with infusional 5-FU has not been widely studied. Given potential differences in the toxicity profile and exposure time, infusional may be more appropriate than bolus for some patients. Here we report successful re-challenge with infusional 5-FU, following coronary vasospasm during the first cycle of 5-FU plus leucovorin plus oxaliplatin chemotherapy, in a patient with metastatic colon cancer and coronary artery disease (CAD). The 5-FU re-challenge plan included dose reduction, CCB and nitrate prophylaxis, and telemetry monitoring.

Purpose: The NHS-IL12 immunocytokine is composed of two IL12 heterodimers fused to the NHS76 antibody. Preclinical studies have shown that this antibody targets IL12 to regions of tumor necrosis by binding histones on free DNA fragments in these areas, resulting in enhanced antitumor activity. The objectives of this phase I study were to determine the maximum tolerated dose (MTD) and pharmacokinetics of NHS-IL12 in subjects with advanced solid tumors. Patients and Methods: Subjects (n = 59) were treated subcutaneously with NHS-IL12 in a single ascending-dose cohort followed by a multiple ascending-dose cohort (n = 37 with every 4-week dosing). Results: The most frequently observed treatment-related adverse events (TRAE) included decreased circulating lymphocytes, increased liver transaminases, and flu-like symptoms. Of the grade ≥3 TRAEs, all were transient and only one was symptomatic (hyperhidrosis). The MTD is 16.8 μg/kg. A time-dependent rise in IFNγ and an associated rise in IL10 were observed following NHS-IL12. Of peripheral immune cell subsets evaluated, most noticeable were increases in frequencies of activated and mature natural killer (NK) cells and NKT cells. Based on T-cell receptor sequencing analysis, increases in T-cell receptor diversity and tumor-infiltrating lymphocyte density were observed after treatment where both biopsies and peripheral blood mononuclear cells were available. Although no objective tumor responses were observed, 5 subjects had durable stable disease (range, 6–30+ months). Conclusions: NHS-IL12 was well tolerated up to a dose of 16.8 μg/kg, which is the recommended phase II dose. Early clinical immune-related activity warrants further studies, including combination with immune checkpoint inhibitors. See related commentary by Lyerly et al., p. 9

BackgroundPRGN-2009 is a novel gorilla adenovirus vaccine containing 35 non-HLA-restricted epitopes of HPV 16 and 18 which is being tested in an open-label, NCI-sponsored, single-center Phase I/II study alone and combined with the bifunctional TGF-β ”trap”/anti-PD-L1 fusion protein bintrafusp alfa (BA) (NCT04432597).MethodsFor the Phase I of the trial, eligible patients are adults with previously treated (checkpoint blockade allowed) recurrent/metastatic HPV-associated cancers. Objectives are to assess the safety and determine the recommended phase 2 dose (RP2D) of PRGN-2009 alone and combined with BA. Treatment followed a single-agent 3+3 dose escalation at two dose levels of PRGN-2009 (dose level 1: 1x1011 viral particle units (VPU), dose level 2: 5x1011 VPU) subcutaneously Q2W for 3 times, then Q4W for up to one year in total. After determination of RP2D, a combination cohort of 10 patients treated with PRGN-2009 at the RP2D combined with BA (1200 mg IV Q2W for 52 weeks) opened. Peripheral blood mononuclear cells collected from patients before and after vaccination with PRGN-2009 were stimulated with overlapping peptide pools and assessed by intracellular cytokine staining to identify HPV-16 and HPV-18 specific T-cells, as well as T-cells targeting cascade antigens not encoded by the vaccine.ResultsSix patients were enrolled in the single-agent PRGN-2009 dose-escalation phase (3 with cervical cancer, 2 with anal cancer, 1 with vaginal cancer). Observed adverse events were Grade 1-2 flu-like syndrome (headache, body aches), injection site reactions (erythema, pruritus, soreness, localized edema), fatigue, and rash. There were no dose limiting toxicities, and 5x1011 VPU was selected as RP2D. Four patients had stable disease as best response, (one ongoing, 10 months on treatment).T-cells targeting HPV-16 and/or HPV-18 were increased after vaccination in 100% of patients, with 3/6 (50%) developing HPV-16 T cells and 5/6 (83%) developing HPV-18 T cells. In some patients, the magnitude and breadth of HPV-16 and HPV-18 specific T cells were notably increased after repeated vaccination. T cells that target the cascade antigens brachyury and MUC1 were also increased in all patients evaluated. Multifunctional T-cell responses against all these antigens were also developed after vaccination in the majority of patients. No differences in immunogenicity were noted between the two dose levels. Enrollment is underway in combination with BA. Updated data will be presented.ConclusionsThe Phase 1 results demonstrate the safety of single-agent PRGN-2009 and induction of anti-HPV T-cell immune responses, supporting the hypothesis that PRGN-2009 could potentially induce anti-tumor effects in HPV-associated cancers.AcknowledgementsThis research was supported in part by the Intramural Research Program of the NIH, NCI.Trial RegistrationNCT04432597Ethics ApprovalApproved by the NIH IRB (Ref No 543876). All participants have given informed consent before taking part in the study.

TPS6092 Background: R/M HPVC (cervical, anal, oropharyngeal, etc.) are incurable by current therapies. For newly diagnosed LA HPV-OPSCC standard-of-care (SOC) is radiotherapy ± chemotherapy (C/RT) or surgery ± adjuvant C/RT, with considerable risk of relapse. Newly diagnosed LA SNSCC treatment follows the OPSCC paradigm, and detection of HPV appears to confer improved prognosis. Neoadjuvant PD-1 immune checkpoint blockade (ICB) before surgery may improve RFS and is being evaluated in a multicenter phase III clinical trial (Keynote-689). PRGN-2009 (P) is a novel gorilla adenovirus vaccine containing 35 non-HLA-restricted epitopes of HPV 16 and 18 shown to induce HPV specific responses (preclinical models). Bintrafusp alfa (BA) is a bifunctional fusion protein targeting TGF-β and PD-L1 with promising activity in HPVC. This trial will evaluate the safety and activity of P/ P + BA in patients with previously treated R/M HPVC and as neoadjuvant/induction therapy before SOC surgery or C/RT in newly diagnosed LA HPV-OPSCC and HPV-SNSCC. Methods: This is a first-in-human, investigator-initiated, single-center phase I/II trial. Pts with previously treated (incl. ICB) R/M HPVC are eligible for Phase I: P dose escalation arm (3+3 design, 6-12 patients) testing 2 dose levels (1x1011, 5x1011 viral particle units, SC Q2W three times, then Q4W), and combination arm (10 patients) testing P (recommended phase 2 dose (RP2D), same schedule) + BA (1200 mg IV Q2W). Treatment (both arms) will continue until disease progression, unacceptable toxicity, decision to withdraw. Primary endpoint is safety. Secondary endpoints include ORR (RECIST 1.1), PFS, and OS. For Phase II, patients with newly diagnosed stage II/III (AJCC Cancer Staging Manual, 8th ed.) HPV-OPSCC and stage II/III/IVA/IVB HPV-SNSCC planned for SOC C/RT or surgery will be eligible for two treatment arms of 20+2 patients each (sequential): P arm and P + BA, to evaluate the treatment activity. All patients will have pre-treatment biopsy, receive two cycles of the study treatment at the NCI Clinical Center two weeks apart, followed by post-treatment biopsy and SOC treatment (at the referring institution) 4 weeks after the first study treatment. Primary endpoint is post-treatment ≥2-fold increase in tumor-infiltrating CD3+ cells. Secondary endpoints include RFS, OS. Exploratory endpoints for both arms include analyses of immune subsets, soluble factors, and HPV-specific immune responses in peripheral blood and tissue where available, and in Phase II sequencing (exome, scRNA), immune spatial profiling with multiplex immunofluorescence, and salivary HPV DNA. Clinical trial registry: NCT04432597. Clinical trial information: NCT04432597.

BackgroundAntitumor vaccines targeting tumor-associated antigens (TAAs) can generate antitumor immune response. A novel vaccine platform using adenovirus 5 (Ad5) vectors [E1–, E2b–] targeting three TAAs—prostate-specific antigen (PSA), brachyury, and MUC-1—has been developed. Both brachyury and the C-terminus of MUC-1 are overexpressed in metastatic castration-resistant prostate cancer (mCRPC) and have been shown to play an important role in resistance to chemotherapy, epithelial–mesenchymal transition, and metastasis. The transgenes for PSA, brachyury, and MUC-1 all contain epitope modifications for the expression of CD8+ T-cell enhancer agonist epitopes. We report here the first-in-human trial of this vaccine platform.MethodsPatients with mCRPC were given concurrently three vaccines targeting PSA, brachyury, and MUC-1 at 5×1011 viral particles (VP) each, subcutaneously every 3 weeks for a maximum of three doses (dose de-escalation cohort), followed by a booster vaccine every 8 weeks for 1 year (dose-expansion cohort only). The primary objective was to determine the safety and the recommended phase II dose. Immune assays and clinical responses were evaluated.ResultsEighteen patients with mCRPC were enrolled between July 2018 and September 2019 and received at least one vaccination. Median PSA was 25.58 ng/mL (range, 0.65–1006 ng/mL). The vaccine was tolerable and safe, and no grade >3 treatment-related adverse events or dose-limiting toxicities (DLTs) were observed. One patient had a partial response, while five patients had confirmed PSA decline and five had stable disease for >6 months. Median progression-free survival was 22 weeks (95% CI: 19.1 to 34). Seventeen (100%) of 17 patients mounted T-cell responses to at least one TAA, whereras 8 (47%) of 17 patients mounted immune responses to all three TAAs. Multifunctional T-cell responses to PSA, MUC-1, and brachyury were also detected after vaccination in the majority of the patients.ConclusionsAd5 PSA/MUC-1/brachyury vaccine is well tolerated. The primary end points were met and there were no DLTs. The recommended phase II dose is 5×1011 VP. The vaccine demonstrated clinical activity, including one partial response and confirmed PSA responses in five patients. Three patients with prolonged PSA responses received palliative radiation therapy. Further research is needed to evaluate the clinical benefit and immunogenicity of this vaccine in combination with other immuno-oncology agents and/or palliative radiation therapy.Trial registration numberNCT03481816.

e17569 Background: Enzalutamideis ahighly effective treatment in metastatic castration resistant prostate cancer (mCRPC). Although Prostate Cancer Working Group (PCWG) guidelines recommend continuing treatment until radiographic/clinical progression (rPD/cPD), many patients discontinue therapy for rising PSA alone. Methods: We conducted an open label, randomized phase 2 trial in mCRPC patients untreated with docetaxel, abiraterone, or enzalutamide, comparing enzalutamide alone or in combination with PROSTVAC, a therapeutic cancer vaccine designed to induce an anti-tumor immune response. The study discontinued accrual after planned interim analysis indicated no difference in progression between the two arms. Patients were followed beyond 1st of 3 confirmed PSA rises until rPD. 49 patients were analyzed for Circulating Tumor Cell (CTC) count and AR-V7 status at 1st PSA rise and at rPD/cPD or last follow up. Results: 57 patients were enrolled with median follow up time of 55.4 mo. 49/57 (86%) patients had rising PSA; median time to 1st PSA rise for all patients was 6.4 mo (95% CI: 3.7-11.0 mo) after starting enzalutamide. 38/57 (67%) patients had progressive disease (majority with rPD; 1/38 (3%) with cPD); median time to progression for all patients was 23.3 mo (95% CI: 16.1-27.8 mo). 5 patients tested positive for AR-V7 within 30 days of rPD. In patients who experienced rPD/cPD, CTCs were detected in 11/24 (46%) samples taken at rPD vs. in only 3/24 (13%) samples taken at rising PSA. CTC counts were higher at rPD compared to samples taken at rising PSA (P = 0.004, Wilcoxon unpaired test). Of the 7 patients still being treated (median time on drug = 4.2 yrs), 2 experienced rising PSA; however none of the patients had detectable CTCs at a median of 30 days from last follow up. Conclusions: These data suggest that a rising PSA may not be a warning of near-term clinically significant disease progression in mCRPC patients treated with enzalutamide, given the 17-month difference between the first rise in PSA and ultimate rPD/cPD seen in this analysis. Further, CTCs and AR-V7 status associate strongly with rPD but not with rising PSA, adding biological rationale to the hypothesis that CTC counts and AR-V7 status are associated with disease progression. Collectively, these data highlight the need to continue to educate patients and providers on PCWG criteria for progression and appropriately-timed utilization of both therapies and diagnostic tests to maximize drug efficacy in mCRPC. Clinical trial information: NCT01867333 .

105 Background: Enzalutamideis ahighly effective treatment in patients with metastatic castration resistant prostate cancer (mCRPC). Although Prostate Cancer Working Group Guidelines (PCWG) recommend continuing treatment until radiographic progression of disease (rPD) or clinical progression (cPD), many patients discontinue therapy for rising PSA alone. Methods: We conducted an open label, randomized phase 2 clinical trial in mCRPC patients (on testosterone suppression therapy) previously untreated with docetaxel, abiraterone, or enzalutamide, comparing enzalutamide alone or in combination with PROSTVAC, a therapeutic cancer vaccine designed to induce an anti-tumor immune response. The study discontinued accrual after a planned interim analysis indicated no difference in progression between the two arms. Patients were followed beyond PSA progression (first of three confirmed PSA rises, evaluated monthly) until rPD per PCWG (scans done every 3 months per protocol). Results: A total of 57 patients were enrolled with a median follow up time of 55.4 months. Of those, 47 (82%) patients were Caucasian and seven (12%) patients were African American. The median age of patients on enrollment was 67.2 years. 49/57 (86%) patients had PSA progression and the median time to first PSA rise for all 57 patients combined was 6.4 months (95% CI: 3.7-11.0 months) after starting enzalutamide. 38/57 (67%) patients experienced progressive disease (majority with rPD and 1/38 (3%) with cPD), with the median time to progression for all 57 patients of 23.3 months (95% CI: 16.1-27.8 months). Conclusions: Consistent with PCWG recommendations, these data suggest that a rising PSA may not be a warning of near-term clinically significant disease progression in mCRPC patients given the nearly 17-month difference between the first rise in PSA and ultimate rPD or cPD seen in this analysis. These data highlight the need to continue to educate patients and providers on PCWG criteria for progression, which were also used in original trials that led to the FDA approval of enzalutamide, so as not to substantially limit the potential efficacy of mCRPC therapies such as enzalutamide. Clinical trial information: NCT01867333.

Background Therapeutic cancer vaccines targeting tumour associated antigens (TAAs) offer a potential method to activate cytotoxic T-cells. A vaccine using a novel Ad5 vector (E1-, E2b-) targeting 3 TAAs, PSA, MUC-1 and Brachyury, has been constructed. Both the C-terminus of MUC-1 and Brachyury have been shown to play an integral role in epithelial-to-mesenchymal transition, metastasis, and chemotherapy resistance. Both antigens are overexpressed in mCRPC. The transgenes for PSA, MUC-1 and Brachyury contain modifications for the expression of CD8+ T-cell enhancer agonist epitopes. This vaccine has not been previously tested in humans. Methods Pts with mCRPC were treated with the combination of 3 vaccines targeting PSA, MUC-1 and Brachyury at 5 x 1011 viral particles (VP) each, SQ every 3 weeks for maximum of 3 doses (dose de-escalation cohort) and followed by boost every 8 weeks for 1 year (dose expansion cohort only). The primary objective was to determine the safety and tolerability and to establish the recommended phase 2 dose. Immune assays were conducted in the first 5 enrolled patients. Results 12 pts were enrolled (6 in each cohort) between 07/2018 and 04/2019 and received at least 1 dose. Median PSA was 37.8 (range, 5.81 – 1006 ng/mL). Vaccine was safe and tolerable, no DLTs or grade 3 or higher treatment-related adverse events (TRAEs) were observed. All other TRAEs were Grade 1 or 2; the most common was injection-site reaction in all pts. Two chemotherapy naive pts had confirmed PSA declines (89% and 50%, respectively) observed after only 1 dose. Third had unconfirmed 12% PSA decline at week 3. 5/5 patients mounted responses to at least 1 TAA while 3/5 mounted immune responses to all 3 TAAs. Multifunctional T-cell responses to PSA, MUC-1 and Brachyury were also detected post-vaccination. Conclusions Ad5 PSA/MUC-1/Brachyury vaccine is safe and well tolerated. The recommended Phase 2 dose is 5 x 1011 VP. Confirmed PSA decline was observed in 2 pts. Multifunctional TAA specific T-cell responses to all 3 antigens were seen in a patient with 89% PSA decline. Further research is warranted to evaluate immunogenicity and eventual clinical benefit. Future trials will involve the use of this vaccine in combination with other immuno-oncology agents. Clinical trial identification NCT03481816. Editorial acknowledgement Debra Weingarten. Legal entity responsible for the study Center for Cancer Research, National Cancer Institute, National Institutes of Health. Funding Intramural Research Program of the Center for Cancer Research, National Cancer Institute (NCI), National Institutes of Health (NIH), and by Cooperative Research and Development Agreements (CRADAs) between the NCI and NantCell/Etubics, and the NCI and NantBioscience. Disclosure E.S. Gabitzsch: Full / Part-time employment: Etubics Corporation. F.R. Jones: Full / Part-time employment: Etubics Corporation. J.P. Balint: Full / Part-time employment: Etubics Corporation. P. Soon-Shiong: Full / Part-time employment, Founder and an executive: NantCell; Full / Part-time employment, Founder and an executive: NantBioscience. S. Rabizadeh: Full / Part-time employment: NantCell. All other authors have declared no conflicts of interest.

Purpose: The transcription factor brachyury has been shown in preclinical studies to be a driver of the epithelial-to-mesenchymal transition (EMT) and resistance to therapy of human tumor cells. This study describes the characterization of a Modified Vaccinia Ankara (MVA) vector–based vaccine expressing the transgenes for brachyury and three human costimulatory molecules (B7.1, ICAM-1, and LFA-3, designated TRICOM) and a phase I study with this vaccine. Experimental Design: Human dendritic cells (DC) were infected with MVA-brachyury-TRICOM to define their ability to activate brachyury-specific T cells. A dose-escalation phase I study (NCT02179515) was conducted in advanced cancer patients (n = 38) to define safety and to identify brachyury-specific T-cell responses. Results: MVA-brachyury-TRICOM-infected human DCs activated CD8+ and CD4+ T cells specific against the self-antigen brachyury in vitro. No dose-limiting toxicities were observed due to vaccine in cancer patients at any of the three dose levels. One transient grade 3 adverse event (AE) possibly related to vaccine (diarrhea) resolved without intervention and did not recur with subsequent vaccine. All other AEs related to vaccine were transient and ≤grade 2. Brachyury-specific T-cell responses were observed at all dose levels and in most patients. Conclusions: The MVA-brachyury-TRICOM vaccine directed against a transcription factor known to mediate EMT can be administered safely in patients with advanced cancer and can activate brachyury-specific T cells in vitro and in patients. Further studies of this vaccine in combination therapies are warranted and planned. Clin Cancer Res; 23(22); 6833–45. ©2017 AACR.

Lessons Learned Concurrent ETBX-011, ETBX-051, and ETBX-061 can be safely administered to patients with advanced cancer. All patients developed CD4+ and/or CD8+ T-cell responses after vaccination to at least one tumor-associated antigen (TAA) encoded by the vaccine; 5/6 patients (83%) developed MUC1-specific T cells, 4/6 (67%) developed CEA-specific T cells, and 3/6 (50%) developed brachyury-specific T cells. The presence of adenovirus 5-neutralizing antibodies did not prevent the generation of TAA-specific T cells. Background A novel adenovirus-based vaccine targeting three human tumor-associated antigens—CEA, MUC1, and brachyury—has demonstrated antitumor cytolytic T-cell responses in preclinical animal models of cancer. Methods This open-label, phase I trial evaluated concurrent administration of three therapeutic vaccines (ETBX-011 = CEA, ETBX-061 = MUC1 and ETBX-051 = brachyury). All three vaccines used the same modified adenovirus 5 (Ad5) vector backbone and were administered at a single dose level (DL) of 5 × 1011 viral particles (VP) per vector. The vaccine regimen consisting of all three vaccines was given every 3 weeks for three doses then every 8 weeks for up to 1 year. Clinical and immune responses were evaluated. Results Ten patients enrolled on trial (DL1 = 6 with 4 in the DL1 expansion cohort). All treatment-related adverse events were temporary, self-limiting, grade 1/2 and included injection site reactions and flu-like symptoms. Antigen-specific T cells to MUC1, CEA, and/or brachyury were generated in all patients. There was no evidence of antigenic competition. The administration of the vaccine regimen produced stable disease as the best clinical response. Conclusion Concurrent ETBX-011, ETBX-051, and ETBX-061 can be safely administered to patients with advanced cancer. Further studies of the vaccine regimen in combination with other agents, including immune checkpoint blockade, are planned.

Therapeutic cancer vaccines that use attenuated vaccinia viruses as delivery vectors are undergoing clinical trials at dozens of sites internationally. Even in an attenuated form, these live viruses can cause severe illness if they are accidentally transmitted to immunocompromised people, pregnant women, or people with certain skin conditions. Oncology nurses should become familiar with how to manage patients' vaccine injection sites to minimize these risks to patients' close contacts and the community at large. .

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 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 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.

Importance Previous phase 1 and 2 trials of PANVAC, a poxviral-based cancer vaccine, have suggested clinical efficacy in some patients with breast, ovarian, and colorectal cancer and have shown evidence of immunologic activity. Preclinical data have shown that docetaxel can modify tumor phenotype, making tumor cells more amenable to T cell–mediated killing. Objective The goal of this study was to determine if the treatment combination of docetaxel and PANVAC improves clinical outcomes in patients with metastatic breast cancer compared with docetaxel treatment alone. Design, Setting, and Participants Between May 2006 and February 2012, this open-label, phase 2 randomized clinical trial enrolled 48 patients with metastatic breast cancer of all subtypes, without limitation on other lines of previous therapy, to receive treatment with either docetaxel with PANVAC (arm A) or docetaxel alone (arm B). Final clinical data were collected on September 16, 2013. All patients were treated at either the National Cancer Institute or the Department of Breast Medical Oncology, MD Anderson Cancer Center. Main Outcomes and Measures The primary end point was progression-free survival (PFS), using a phase 2.5 statistical design, with the intent of identifying a trend toward benefit (defined as 1-sided P ≤ .10) to guide a larger trial design. Secondary end points included safety and immunologic correlative studies. Results Forty-eight participants were enrolled: 25 were randomized to the combination treatment arm A, and 23 to arm B. No patient remained in the study at the time of the final analysis. Patient and tumor characteristics were well matched. Analysis of adverse events in both treatment arms demonstrated very little difference between the 2 groups. In the combination treatment arm (arm A), statistically significant increases were noted in the frequency of grades 1 and 2 edema ( P = .02, likely related to greater median number of docetaxel cycles) and injection-site reactions ( P P = .09). Conclusions and Relevance The results suggest that the combination of PANVAC with docetaxel in metastatic breast cancer may provide a clinical benefit. This study was hypothesis generating and provides both rationale and statistical assumptions for a larger definitive randomized study. Trial Registration clinicaltrials.gov Identifier:NCT00179309

Background: There is increasing interest in using combination immunotherapy in the neoadjuvant setting in prostate cancer, however, endpoints for such studies remain elusive. We have conducted a clinical trial evaluating immunotherapy with ADT in patients with high risk prostate cancer. Patients were assessed for immune responses and changes in endorectal (er) MRI which can be used to assess intraprostatic tumors. Methods: Treatment-naïve high-risk (Gleason 8-10, PSA>20, or stage T3) prostate cancer patients (pts) were randomized to standard ADT+Radiation + an immunotherapy targeting MUC1 (tecemotide, aka L-BLP25) in this trial (NCT01496131). ADT consisted of gonadotropin-releasing hormone therapy. Immunotherapy included low dose (300 mg/m2, maximum 600 mg) pre-treatment cyclophosphamide for regulatory T-cell depletion. erMRI was done at baseline and after 2 months of immunotherapy including multiparametric MRI evaluation of apparent diffusion coefficient (ADC) maps from diffusion-weighted MRI. Monthly peripheral blood assessments analyzed immune cell subsets using flow cytometry and intracellular cytokine (ICC) staining for MUC-1 specific responses. Results: 28 pts with high risk prostate cancer were enrolled (n=14/arm). As expected, PSA declined in all pts 2 months after ADT. erMRI after 2 months of treatment suggested greater improvements in ADC values in pts receiving immunotherapy+ADT vs. ADT alone. Improved ADC on MRI indicates increased intratumoral diffusion and has been associated with decreased tumor density. The improvements in ADC were seen when one dominant tumor per patient was evaluated (p=0.17) but were more pronounced when up to 3 lesions were evaluated per pt (n=44 lesions; p=0.031). Compared to baseline, there were trends to increases in CTLA4+ CD8+ T-cells consistent with immune activation and decreases in myeloid derived suppressor cells (MDSCs) in pts receiving immunotherapy+ADT coinciding with the erMRI changes. These immune findings were not seen in the ADT alone group. 3 of 14 pts had MUC1 specific immune response by ICC. 2 of these patients had the greatest changes in ADC noted on erMRI over a 2-year period. Conclusions: Based on assessments by erMRI, pts who received ADT+immunotherapy had greater improvements in ADC than pts receiving ADT alone. Given that ADC improvements are associated with decreased tumor density, this suggests a possible greater anti-tumor effect of the ADT-immunotherapy combination vs. ADT alone. These findings were associated with trends to increased activated CD8+ T-cells and decreased MDSCs in pts receiving immunotherapy+ADT, with 3/14 pts having MUC1 specific immune responses. Further studies are required to confirm the potential to use ADC on erMRI as a potential (bio)marker of anti-tumor effect of immune combinations including ADT. Citation Format: Ravi A. Madan, Baris Turkbey, Lauren M. Lepone, Renee N. Donahue, Italia Grenga, Samuel Samuel Borofsky, Peter A. Pinto, Deborah Citrin, Aradhana Kaushal, Andra Krauze, Sheri McMahon, Myrna Rauchhorst, Anna Couvillon, Martin H. Falk, S Peter Eggleton, Stephen C. Greco, Peter L. Choyke, William L. Dahut, Jeffrey Schlom, James L. Gulley. Neoadjuvant immunotherapy with androgen deprivation therapy (ADT) prior to radiation in prostate cancer: Impact on multiparametric prostate MRI and immune responses [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr LB-059. doi:10.1158/1538-7445.AM2017-LB-059

30 Background: Endorectal(er) MRI is an emerging tool in assessing intraprostatic tumors. Immunotherapy development in prostate cancer has been limited due to the lack of intermediate (bio)markers of response. Methods: Untreatedpts with high-risk prostate cancer were randomized in a trial (NCT01496131) of standard ADT+Radiation + an immunotherapy targeting MUC1 (tecemotide, aka L-BLP25). Pts had erMRI at baseline and after 2 months of ADT+/- biweekly immunotherapy. Low dose (300 mg/m2, maximum 600 mg) cyclophosphamide for regulatory T-cell depletion preceded first immunotherapy. Multiparametric MRI included evaluation of apparent diffusion coefficient (ADC) maps from diffusion-weighted MRI. Monthly peripheral blood assessments utilized flow cytometry to evaluate immune cell subsets. This analysis focuses on the 2 month neoadjuvant period of ADT+/-immunotherapy before radiation. Results: 28 pts (n = 14/arm) with high risk prostate cancer (Gleason 8-10, PSA > 20, or stage T3) were enrolled. PSA declined in all pts 2 months after ADT. erMRI findings at 2 months indicated greater improvements in ADC values in pts receiving immunotherapy+ADT vs. ADT alone. Improved ADC on MRI suggests improvements in intratumoral diffusion and has been associated with decreased tumor density. This relative improvement between the groups occurred both per patient (p = 0.16) and per lesion (p = 0.031). Relative to baseline, pts receiving immunotherapy+ADT had increases in CTLA4+ CD8+ T-cells consistent with immune activation (p = 0.0134) and decreases in myeloid derived suppressor cells (MDSCs; p = 0.0353) during the neoadjuvant period corresponding to the erMRI changes. These immune findings were not seen in the ADT alone group. Conclusions: Pts who received immunotherapy+ADT for 2 months had greater improvements in ADC values on erMRI, consistent with decreased tumor density, relative to pts receiving ADT alone. Corresponding increases in activated CD8+ T-cells and decreases in MDSCs were seen in pts receiving vaccine+ADT. These preliminary findings suggest that ADC on MRI may be useful in assessing immunologic impact. Further study is warranted. Clinical trial information: NCT01496131.

203 Background: Recently there has been growing evidence that 18F-Fluoride PET/CT has increased sensitivity relative to technetium-99m diphosphonate (Tc-99m MDP) bone scan for evaluating metastatic bone disease. This analysis studied changes in 18F-Fluoride PET/CT and evaluated associations with PSA changes for mCRPC patients (pts) on enzalutamide (enz). Methods: As part of a randomized phase II study evaluating enz with or without vaccine therapy, men with mCRPC electively underwent 18F-Fluoride PET/CT at 3 month (mos) intervals [NCT01867333]. At these points serum PSA was collected. Data was taken on max SUV and volume of presumed cancerous lesions and a variable, ΣSUV*Volume, was calculated which was defined as the sum of the products of SUV max and volume of cancerous lesions. Results: At the time of our analysis, 19 pts had PSA and PET/CT data for at least 2 time points within 1 year of initiating therapy. The median baseline PSA was 19.6 ng/ml (0.76-587). All pts had predominantly bone disease with 10 having small volume lymphadenopathy. Only 1/19 pts progressed by PSA Working Group criteria. An analysis found that 18/19 pts (95%) had an association between changes in PSA and ΣSUV*Volume. Of these 18 pts, 13 had a major ( > 50%) and 1 had a minor ( > 30%) PSA response and all 14 had an accompanying decrease in ΣSUV*Volume. For 11/14 pts with PSA responses, the change in ΣSUV*Volume paralleled the change in PSA at all time points, while for 3 pts an associated change between ΣSUV*Volume and PSA was delayed by 3 mos. 4/14 pts had short term responses lasting only 3 mos followed by PSA increases. For these 4 pts the changes in ΣSUV*Volume paralleled PSA changes, decreasing at 3 mos and increasing thereafter. Finally 4/18 patients had no PSA response to therapy. All 4 pts had increases in ΣSUV*Volume which paralleled rising PSA values. Conclusions: Preliminary data from a small cohort suggests that findings on 18F-Fluoride PET/CT are associated with PSA changes. This represents a substantial difference from standard Tc-99m MDP and further suggests that 18F-Fluoride PET/CT may provide a more sensitive analysis of bone disease. Additional data from this and other studies are required.

172 Background: Results of recent clinical trials have intensified interest in immunotherapy in oncology. A number of cancer immunotherapies have been approved recently, while others are in late stage clinical development. The poxvirus-based active immunotherapy, PROSTVAC is generally well tolerated and is currently being evaluated in a global Phase 3 randomized, placebo-controlled trial. Ipilimumab, an approved immune checkpoint inhibitor in melanoma, is also being evaluated in a Phase 3 trial in chemo-naïve mCRPC. Methods: Results of two Phase 2 trials in men with mCRPC who were treated with PROSTVAC alone were compared with results from a Phase 1 combination study in mCRPC patients treated with PROSTVAC plus escalating doses of ipilimumab. Patients were enrolled in the Phase 1 combination study when docetaxel was the only FDA-approved mCRPC treatment that improved overall survival (OS). Results: In a multicenter Phase 2 trial, 125 men were randomized 2:1 to receive PROSTVAC or placebo. Patients treated with PROSTVAC had improved OS compared to placebo (25.1 vs 16.6 months; HR 0.56; 95% CI 0.37-0.85).Similar data was seen in a second phase 2 trial of PROSTVAC, where 32 patients with mCRPC had a median OS of 26.6 months (predicted median OS by the Halabi nomogram was 17.4 months). In a Phase 1 combination study of 30 mCRPC patients with similar baseline characteristics (predicted median OS of 18.5 months), patients were treated with PROSTVAC plus escalating doses of ipilimumab. The observed median OS was 31.3 months for all dose cohorts and 37.2 months for patients treated at 10 mg/kg based on updated overall survival data. Furthermore, there appears to be a tail on the curve with approximately 20% of patients at 10 mg/kg alive at 80 months. Conclusions: The comparison of data from three independent trials of PROSTVAC active immunotherapy in three similar patient populations provides hypothesis-generating data that the addition of an immune checkpoint inhibitor may have a positive effect on overall survival through a potential synergy in mechanism of action. The updated long term survival data is further evidence of improved OS with PROSTVAC. Future randomized trials are being planned to prospectively evaluate this hypothesis. Clinical trial information: NCT00113984.

TPS5104 Background: There is a strong rationale to combine therapeutic cancer vaccines with hormonal abrogation in prostate cancer. Androgen abrogation augments T-cell trafficking to prostate, decreases immune tolerance, increases production of naïve thymic T-cells, enhances cytotoxic T-cell repertoire. PSA TRICOM (PROSTVAC) is a therapeutic, viral-vector based, off-the-shelf, cancer vaccine of PSA & 3 co-stimulatory molecules in phase III testing. This was developed at the NCI in collaboration with Bavarian Nordic Immunotherapeutics. It has demonstrated safety and survival benefit in a randomized phase 2 trial of metastatic castrate resistant prostate cancer (mCRPC). Enzalutamide is a modern androgen receptor inhibitor (ARI) approved for the treatment of mCRPC. Data from the clinical trials with these therapies suggest good individual tolerability without any overlapping toxicities. Analysis of previous trials suggests that vaccines may enhance clinical outcomes with ARI. These data form the scientific basis for a combination approach of a cancer vaccine with ARI to control tumor progression in mCRPC. Methods: A randomized, phase 2, open-label clinical trial at the NCI will enroll 72 chemo-naïve, minimally symptomatic patients with mCRPC. They will be randomized (1:1) to enzalutamide (160 mg daily) alone, or enzalutamide with PSA TRICOM for treatment until radiographic progression. PSA-TRICOM will be administered in a core phase (with day 1, 15 and 29 then 4 additional monthly boosts) followed by continued boosts every 3 months. The primary end point will evaluate time to progression in each arm with secondary endpoints including overall survival and systemic immune responses (lymphocyte subsets, regulatory T-cells, regulatory T-cell function, cytokines, naïve thymic emigrants). If a therapeutic cancer vaccine can enhance the clinical efficacy of a hormonal agent such as enzalutamide, it may help define a new role for vaccines as an adjuvant to standard therapies. We will also evaluate this combination in a second trial in non-metastatic, castration-sensitive patients where this combination may yield its greatest clinical impact.

TPS3127 Background: Saccharomyces cerevisiae has been genetically modified to express CEA protein and developed under a CRADA with GlobeImmune/NCI as a heat-killed immune-stimulating, therapeutic cancer vaccine (GI-6207). A phase I study with GI-6207 demonstrated safety, biomarker stabilization and enhanced immune response in some patients. CEA is over-expressed in multiple malignancies, including medullary thyroid cancer (MTC). Two therapies recently approved by the FDA for metastatic MTC (vandetanib, cabozantinib) come with toxicity and should be reserved for symptomatic/progressive disease. However, a large population of asymptomatic MTC patients has small tumor burden and/or disease that is more indolent. The standard management of these patients is observation. Preliminary data suggest that tumor growth measured by the rate of CEA and calcitonin increase can be quantified in a 3-6 months. Retrospective data from prostate cancer studies suggest vaccines can alter growth rates within 3-4 months. We hypothesize that GI-6207 can alter tumor growth rates in MTC and impact long-term outcome. Methods: A phase II study will evaluate the effect of GI-6207 onthe rates ofincrease in calcitonin in metastatic MTC. 34 patients with minimally symptomatic, radiographically evaluable, metastatic MTC will be randomized 1:1. Arm A will receive vaccine for a year from the time of enrollment. Arm B will receive vaccine after 6 months of surveillance. GI-6207 will be administered subcutaneously at 4 sites (10 yeast units/site), every 2 weeks for 3 months, then monthly up to 1 year. The primary endpoint will compare the effect of GI-6207 on calcitonin kinetics between the vaccine and surveillance arms in the first 6 months. Secondary endpoints include immunologic responses (including antigen-specific T cell responses), objective responses, time to progression, and changes in CEA kinetics. If this trial can prospectively demonstrate that vaccines can alter tumor growth rates, and if such changes are associated with clinical outcomes, then changes in tumor growth rates may become a clinical metric to evaluate vaccine efficacy in MTC and other populations.

e16036 Background: Recombinant (rec) poxviruses have been developed as therapeutic cancer vaccines. A multi-institutional, randomized phase II trial of poxviral vaccine, PROSTVAC-V/F, suggested an improvement in median overall survival in men with metastatic castration resistant prostate cancer. A phase III trial in this same population is accruing. Accumulating data suggest a favorable safety profile of the poxviral vaccines (vacs). Methods: We reviewed all vaccine injections (inj) from 297 patients (pts) in 9 clinical trials involving poxviral vaccines. Vacs consisted of rec vaccinia and rec fowlpox encoded with 3 human costimulatory molecules (TRICOM), and a) prostate specific antigen, or b) carcinoembryonic antigen +/-mucin-1. Vacs were administered at doses between 1.2x108 to 2x109 pfu, subcutaneously, in all pts. 21 pts were also vaccinated intra-tumorally. 84 pts received concurrent treatments, such as radiation, celecoxib, ipilimumab, samarium-153, or flutamide in 4 of these trials. All 9 trials involved granulocyte-macrophage colony-stimulating factor (GM-CSF), or rec fowlpox encoding GM-CSF as an immune adjuvant. We report the grade >=2 adverse events (AEs) at least possibly attributed to vaccine. Results: A total of 1,793 poxviral inj were given. 33% (593) of all inj were associated with grade >=2 vaccination emergent AEs. Of those, 25.3 % (454) were local inj site reactions; none serious. There was no contact transmission or inadvertent inoculation. One patient experienced grade 4 myocardial infarction and thrombotic thrombocytopenic purpura (TTP) reported as possibly related to vaccine. Below is the summary of AEs. Conclusions: Recombinant poxviral TRICOM vaccines appear safe and well tolerated at a broad range of doses, routes of administration and in combination with other treatments. Clinical trial information: NCT00081848, NCT00088413, NCT00060528, NCT00060528, NCT00078585, NCT00096551, NCT00113984. [Table: see text]

85 Background: Recombinant poxviruses have been developed as therapeutic cancer vaccines. Here, we report the safety data from NCI clinical trials with poxviral vaccines. Methods: We evaluated all vaccine injections from 215 patients in 8 clinical trials involving poxviral viral vaccines. The Office of Biotechnology Activities, National Cancer Institute (NCI) Institutional Review Board, and NCI Scientific Review Committee approved all of these trials. Vaccines were consisted of recombinant vaccinia and recombinant fowlpox encoded with 3 human costimulatory molecules (TRICOM), and prostate specific antigen (PSA), or carcinoembryonic antigen, and/or mucin-1. Vaccines were administered at doses between 1.2x108 to 2x109 pfu, subcutaneously, in all patients. Twenty-one patients were also vaccinated intra-tumorally. 84 patients also received other concurrent treatment modalities, such as radiation, celecoxib, ipilimumab, samarium-153, or flutamide on 4 of these trials. All 8 clinical trials involved granulocyte-macrophage colony-stimulating factor (GM-CSF) 100mcg, or recombinant fowlpox encoding GM-CSF at 1x 108pfu as an immune adjuvant. Here, we report here the grade 2 or higher adverse events given at least a possible attribution to vaccine. Results: A total of 1,348 poxviral injections were given in 215 patients. No contact transmission, inadvertent inoculation, or any serious adverse events (AEs) related to vaccinia was observed. Below is the summary of proportion of vaccine administrations associated with specific AEs. Conclusions: These data demonstrate a favorable safety profile of the poxviral vaccines at a broad range of doses, routes of administration, in combination with other treatments, and in various tumor types. Clinical trial information: NCT00060528, NCT00096551, NCT00088413, NCT00081848, NCT00113984, NCT00450619, NCT00450463. [Table: see text]

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 imtris;al. All pts received DOC 35 mg/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. 2° endpoints included overall survival and immunologic correlative studies. 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). Patient 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). Toxicity was similar in both arms. Immune analysis and correlation to pt clinical outcomes is ongoing. 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. Acknowledgements M. Bilusic, J. Kim, N.K. Singh, J. Hodge. Clinical trials.gov number NCT00179309. Disclosure J. Schlom: The Laboratory of Tumor Immunology and Biology, of which I am Lab Chief, has a Collaborative Research and Development Agreement with Bavarian Nordic. The LTIB's research is funded by the Intramural Research Program, CCR, NCI, NIH. All other authors have declared no conflicts of interest.

458 Background: Saccharomyces cerevisiae (yeast) has been genetically modified to express CEA protein and employed as a heat-killed immune-stimulating, vector-based vaccine. Preclinical studies have shown that yeast CEA vaccine can induce a strong CEA-specific T-cell immune response (IR) and anti-tumor activity. Methods: Patients (Pts) were enrolled in this phase I trial at 3 dose levels: 4, 16, and 40 yeast units (each unit =107 yeast particles). The vaccine was administered equally at 4 sites subcutaneously in bilateral inguinal and anterior chest wall regions. Vaccine was administered at 2 week intervals for 3 months, then monthly. Eligible pts were required to have a serum CEA > 5 ng/ml or > 20% CEA+ positive tumor block and no autoimmune history. An expansion cohort of 10 pts was enrolled to focus on IR. Pts had re-staging scans at 3 months, then bimonthly. Peripheral blood was collected for analysis of IR including the Effector/Regulatory T-cell ratio, ELISPOT assay, changes in the myeloid-derived suppressor cells (MDSC) and natural killer cells (NK). Results: 25 pts with progressive metastatic CEA-expressing carcinoma were enrolled; 22 had colorectal adenocarcinoma. Vaccine was well tolerated with no dose limiting toxicities. The most common adverse event was grade 1/2 injection site reaction. Overall, 7 patients had stabilization or declines in serum CEA after treatment. Of them, 5 pts (3 with colorectal cancer) had stable disease beyond 3 months and 1 is still on-going (14 +, 8, 8, 4.5 and 4 months). No anti-CEA antibodies were detected. Post vs. pre-vaccination: a) five out of 9 evaluable pts showed evidence by ELISPOT of CEA-specific T-cell IRs b) 8/16 pts had increased and 8/16 pts had decreased CD4 Effector/Treg ratio and c) 6/13 pts had increased and 2/13pts had decreased NK frequency. Conclusions: Saccharomyces cerevisiae-CEA demonstrated an acceptable safety profile. Although this is an advanced disease population of pts which is not ideal for immune-based therapy, CEA serum stabilizations and CEA-specific IRs were seen in some pts. Randomized studies are required to determine the clinical benefit of this vaccine in a more appropriate patient population for vaccine therapy.

2604 Background: Saccharomyces cerevisiae (yeast) were engineered to express human CEA protein and administered as a heat killed, whole yeast therapeutic vaccine. Preclinical studies have shown that these modified yeast can induce a strong immune response to CEA as well as antitumor responses in a CEA-transgenic host. Methods: Patients (pts) were enrolled in this classic phase I design at 3 dose levels: 4, 16, and 40 yeast units (each unit =107 yeast particles). The vaccine was administered in equal doses at 4 sites subcutaneously in bilateral inguinal and anterior chest wall regions. Vaccine was administered at 2 week intervals for 3 months, then monthly. Eligible patients were required to have a serum CEA > 5 ng/ml or >20% CEA+ positive tumor block, ECOG PS 0-2, and no autoimmune history. An expansion cohort of 10 ECOG PS 0-1 pts was enrolled to focus primarily on immune response at the 40 yeast unit dose. Pts had re-staging scans at 3 months, then bimonthly. Peripheral blood was collected for analysis ...

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.