Jennifer L. Marte

Combining a Recombinant Cancer Vaccine with Standard Definitive Radiotherapy in Patients with Localized Prostate Cancer

Purpose: Many patients with clinically localized prostate cancer develop biochemical failure despite excellent local therapy perhaps due to occult metastatic disease. One potential solution is the utilization of a well-tolerated systemic therapy (e.g., vaccine) in concert with local therapy. Experimental Design: We present a randomized phase II clinical trial designed to determine if a poxviral vaccine encoding prostate-specific antigen (PSA) can induce a PSA-specific T-cell response when combined with radiotherapy in patients with clinically localized prostate cancer. Thirty patients were randomized in a 2:1 ratio into vaccine plus radiotherapy or radiotherapy-only arms. Those patients in the combination arm received a “priming” vaccine with recombinant vaccinia (rV) PSA plus r V containing the T-cell costimulatory molecule B7.1 (rV-B7.1) followed by monthly booster vaccines with recombinant fowlpox PSA. The vaccines were given with local granulocyte-macrophage colony-stimulating factor and low-dose systemic interleukin-2. Standard external beam radiation therapy was given between the fourth and the sixth vaccinations. Results: Seventeen of 19 patients in the combination arm completed all eight vaccinations and 13 of these 17 patients had increases in PSA-specific T cells of at least 3-fold versus no detectable increases in the radiotherapy-only arm (P < 0.0005). There was also evidence of de novo generation of T cells to well-described prostate-associated antigens not found in the vaccine, providing indirect evidence of immune-mediated tumor killing. The vaccine was well tolerated. Conclusion: This vaccine regimen can be safely given in patients undergoing radiation therapy for localized prostate cancer, with the majority of patients generating a PSA-specific cellular immune response to vaccine.

A randomized phase II study of concurrent docetaxel plus vaccine versus vaccine alone in metastatic androgen-independent prostate cancer.

PURPOSE: Docetaxel has activity against androgen-independent prostate cancer and preclinical studies have shown 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 the vaccine. Secondary end points were whether vaccine could be given safely with docetaxel and the clinical outcome of the treatment regimen. EXPERIMENTAL DESIGN: The vaccination regimen was composed of (a) recombinant vaccinia virus (rV) that expresses the prostate-specific antigen gene (rV-PSA) admixed with (b) rV that expresses the B7.1 costimulatory gene (rV-B7.1), and (c) sequential booster vaccinations with recombinant fowlpox virus (rF-) containing the PSA gene (rF-PSA). Patients received granulocyte macrophage colony-stimulating factor with each vaccination. Twenty-eight patients with metastatic androgen-independent prostate cancer 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. The ELISPOT assay 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 postvaccination. Eleven patients who progressed on vaccine alone crossed over to receive docetaxel at time of progression. Median progression-free survival on docetaxel was 6.1 months after receiving vaccine compared with 3.7 months with the same regimen in a historical control. CONCLUSION: This is the first clinical trial to show that docetaxel can be administered safely with immunotherapy 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.

Immune impact induced by PROSTVAC (PSA-TRICOM), a therapeutic vaccine for prostate cancer.

Gulley and colleagues report immune responses from patients treated with PSA-TRICOM (a vaccinia prime/fowlpox boosts vaccine regimen with vectors expressing human PSA, B7.1, ICAM-1, and LFA-3), with 57% of 104 patients developing PSA-specific immune responses and 68% with antigen spreading. PSA-TRICOM (PROSTVAC) is a novel vector-based vaccine designed to generate a robust immune response against prostate-specific antigen (PSA)-expressing tumor cells. The purpose of this report is to present an overview of both published studies and new data in the evaluation of immune responses to the PSA-TRICOM vaccine platform, currently in phase III testing. Of 104 patients tested for T-cell responses, 57% (59/104) demonstrated a ≥2-fold increase in PSA-specific T cells 4 weeks after vaccine (median 5-fold increase) compared with pre-vaccine, and 68% (19/28) of patients tested mounted post-vaccine immune responses to tumor-associated antigens not present in the vaccine (antigen spreading). The PSA-specific immune responses observed 28 days after vaccine (i.e., likely memory cells) are quantitatively similar to the levels of circulating T cells specific for influenza seen in the same patients. Measurements of systemic immune response to PSA may underestimate the true therapeutic immune response (as this does not account for cells that have trafficked to the tumor) and does not include antigen spreading. Furthermore, although the entire PSA gene is the vaccine, only one epitope of PSA is evaluated in the T-cell responses. Because this therapeutic vaccine is directed at generating a cellular/Th1 immune response (T-cell costimulatory molecules and use of a viral vector), it is not surprising that less than 0.6% of patients (2/349) tested have evidence of PSA antibody induction following vaccine. This suggests that post-vaccine PSA kinetics were not affected by PSA antibodies. An ongoing phase III study will evaluate the systemic immune responses and correlation with clinical outcomes. Cancer Immunol Res; 2(2); 133–41. ©2013 AACR.

Avelumab for metastatic or locally advanced previously treated solid tumours (JAVELIN Solid Tumor): a phase 1a, multicohort, dose-escalation trial

BACKGROUND Avelumab (MSB0010718C) is a human IgG1 monoclonal antibody that binds to PD-L1, inhibiting its binding to PD-1, which inactivates T cells. We aimed to establish the safety and pharmacokinetics of avelumab in patients with solid tumours while assessing biological correlatives for future development. METHODS This open-label, single-centre, phase 1a, dose-escalation trial (part of the JAVELIN Solid Tumor trial) assessed four doses of avelumab (1 mg/kg, 3 mg/kg, 10 mg/kg, and 20 mg/kg), with dose-level cohort expansions to provide additional safety, pharmacokinetics, and target occupancy data. This study used a standard 3 + 3 cohort design and assigned patients sequentially at trial entry according to the 3 + 3 dose-escalation algorithm and depending on the number of dose-limiting toxicities during the first 3-week assessment period (the primary endpoint). Patient eligibility criteria included age 18 years or older, Eastern Cooperative Oncology Group performance status 0-1, metastatic or locally advanced previously treated solid tumours, and adequate end-organ function. Avelumab was given as a 1-h intravenous infusion every 2 weeks. Patients in the dose-limiting toxicity analysis set were assessed for the primary endpoint of dose-limiting toxicity, and all patients enrolled in the dose-escalation part were assessed for the secondary endpoints of safety (treatment-emergent and treatment-related adverse events according to National Cancer Institute Common Terminology Criteria for Adverse Events version 4.0), pharmacokinetic and pharmacodynamic profiles (immunological effects), best overall response by Response Evaluation Criteria, and antidrug antibody formation. The population for the pharmacokinetic analysis included a subset of patients with rich pharmacokinetic samples from two selected disease-specific expansion cohorts at the same study site who had serum samples obtained at multiple early timepoints. This trial is registered with ClinicalTrials.gov, number NCT01772004. Patient recruitment to the dose-escalation part reported here is closed. FINDINGS Between Jan 31, 2013, and Oct 8, 2014, 53 patients were enrolled (four patients at 1 mg/kg, 13 at 3 mg/kg, 15 at 10 mg/kg, and 21 at 20 mg/kg). 18 patients were analysed in the dose-limiting toxicity analysis set: three at dose level 1 (1 mg/kg), three at dose level 2 (3 mg/kg), six at dose level 3 (10 mg/kg), and six at dose level 4 (20 mg/kg). Only one dose-limiting toxicity occurred, at the 20 mg/kg dose, and thus the maximum tolerated dose was not reached. In all 53 enrolled patients (the safety analysis set), common treatment-related adverse events (occurring in >10% of patients) included fatigue (21 patients [40%]), influenza-like symptoms (11 [21%]), fever (8 [15%]), and chills (6 [11%]). Grade 3-4 treatment-related adverse events occurred in nine (17%) of 53 patients, with autoimmune disorder (n=3), increased blood creatine phosphokinase (n=2), and increased aspartate aminotransferase (n=2) each occurring in more than one patient (autoimmune disorder in two patients at 10 mg/kg and one patient at 20 mg/kg, increased blood creatine phosphokinase in two patients at 20 mg/kg, and increased aspartate aminotransferase in one patient at 1 mg/kg, and one patient at 10 mg/kg). Six (11%) of 53 patients had a serious treatment-related adverse event: autoimmune disorder (two [13%]), lower abdominal pain (one [7%]), fatigue (one [7%]), and influenza-like illness (one [7%]) in three patients treated at 10 mg/kg dose level, and autoimmune disorder (one [5%]), increased amylase (one [5%]), myositis (one [5%]), and dysphonia (one [5%]) in three patients who received the 20 mg/kg dose. We recorded some evidence of clinical activity in various solid tumours, with partial confirmed or unconfirmed responses in four (8%) of 53 patients; 30 (57%) additional patients had stable disease. Pharmacokinetic analysis (n=86) showed a dose-proportional exposure between doses of 3 mg/kg and 20 mg/kg and a half-life of 95-99 h (3·9-4·1 days) at the 10 mg/kg and 20 mg/kg doses. Target occupancy was greater than 90% at doses of 3 mg/kg and 10 mg/kg. Antidrug antibodies were detected in two (4%) of 53 patients. No substantial differences were found in absolute lymphocyte count or multiple immune cell subsets, including those expressing PD-L1, after treatment with avelumab. 31 (58%) of 53 patients in the overall safety population died; no deaths were related to treatment on study. INTERPRETATION Avelumab has an acceptable toxicity profile up to 20 mg/kg and the maximum tolerated dose was not reached. Based on pharmacokinetics, target occupancy, and immunological analysis, we chose 10 mg/kg every 2 weeks as the dose for further development and phase 3 trials are ongoing. FUNDING National Cancer Institute and Merck KGaA.

Phase I Trial of a Yeast-Based Therapeutic Cancer Vaccine (GI-6301) Targeting the Transcription Factor Brachyury

Carcinomas can overexpress brachyury, a transcription factor not expressed in most adult tissues. A therapeutic yeast vaccine targeting brachyury was tested in phase I clinical trials. It induced T-cell responses with no autoimmunity and showed preliminary clinical activity. The nuclear transcription factor brachyury has previously been shown to be a strong mediator of the epithelial-to-mesenchymal transition (EMT) in human carcinoma cells and a strong negative prognostic factor in several tumor types. Brachyury is overexpressed in a range of human carcinomas as well as in chordoma, a rare tumor for which there is no standard systemic therapy. Preclinical studies have shown that a recombinant Saccharomyces cerevisiae (yeast) vaccine encoding brachyury (GI-6301) can activate human T cells in vitro. A phase I dose-escalation (3+3 design) trial enrolled 34 patients at 4 dose levels [3, 3, 16, and 11 patients, respectively, at 4, 16, 40, and 80 yeast units (YU)]. Expansion cohorts were enrolled at 40- and 80-YU dose levels for analysis of immune response and clinical activity. We observed brachyury-specific T-cell immune responses in the majority of evaluable patients despite most having been heavily pretreated. No evidence of autoimmunity or other serious adverse events was observed. Two chordoma patients showed evidence of disease control (one mixed response and one partial response). A patient with colorectal carcinoma, who enrolled on study with a large progressing pelvic mass and rising carcinoembryonic antigen (CEA), remains on study for greater than 1 year with stable disease, evidence of decreased tumor density, and decreased serum CEA. This is the first-in-human study to demonstrate the safety and immunogenicity of this therapeutic cancer vaccine and provides the rationale for exploration in phase II studies. A randomized phase II chordoma study is now enrolling patients. Cancer Immunol Res; 3(11); 1248–56. ©2015 AACR.

Docetaxel Alone or in Combination With a Therapeutic Cancer Vaccine (PANVAC) in Patients With Metastatic Breast Cancer: A Randomized Clinical Trial.

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<.001). In the final data analysis, median PFS was 7.9 months in arm A vs 3.9 months in arm B (hazard ratio, 0.65 [95% CI, 0.34-1.14]; 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.

Samarium-153-EDTMP (Quadramet ® ) with or without vaccine in metastatic castration-resistant prostate cancer: A randomized Phase 2 trial

PSA-TRICOM is a therapeutic vaccine in late stage clinical testing in metastatic castration-resistant prostate cancer (mCRPC). Samarium-153-ethylene diamine tetramethylene phosphonate (Sm-153-EDTMP; Quadramet®), a radiopharmaceutical, binds osteoblastic bone lesions and emits beta particles causing local tumor cell destruction. Preclinically, Sm-153-EDTMP alters tumor cell phenotype facilitating immune-mediated killing. This phase 2 multi-center trial randomized patients to Sm-153-EDTMP alone or with PSA-TRICOM vaccine. Eligibility required mCRPC, bone metastases, prior docetaxel and no visceral disease. The primary endpoint was the proportion of patients without radiographic disease progression at 4 months. Secondary endpoints included progression-free survival (PFS), overall survival (OS), and immune responses. Forty-four patients enrolled. Eighteen and 21 patients were evaluable for the primary endpoint in Sm-153-EDTMP alone and combination arms, respectively. There was no statistical difference in the primary endpoint, with two of 18 (11.1%) and five of 21 (23.8%) in Sm-153-EDTMP alone and combination arms, respectively, having stable disease at approximately the 4-month evaluation time point (P = 0.27). Median PFS was 1.7 vs. 3.7 months in the Sm-153-EDTMP alone and combination arms (P = 0.041, HR = 0.51, P = 0.046). No patient in the Sm-153-EDTMP alone arm achieved prostate-specific antigen (PSA) decline > 30% compared with four patients (of 21) in the combination arm, including three with PSA decline > 50%. Toxicities were similar between arms and related to number of Sm-153-EDTMP doses administered. These results provide the rationale for clinical evaluation of new radiopharmaceuticals, such as Ra-223, in combination with PSA-TRICOM.

Phase I Trial of M7824 (MSB0011359C), a Bifunctional Fusion Protein Targeting PD-L1 and TGFβ, in Advanced Solid Tumors

Purpose: M7824 (MSB0011359C) is an innovative first-in-class bifunctional fusion protein composed of a mAb against programmed death ligand 1 (PD-L1) fused to a TGFβ “trap.” Experimental Design: In the 3+3 dose-escalation component of this phase I study (NCT02517398), eligible patients with advanced solid tumors received M7824 at 1, 3, 10, or 20 mg/kg once every 2 weeks until confirmed progression, unacceptable toxicity, or trial withdrawal; in addition, a cohort received an initial 0.3 mg/kg dose to evaluate pharmacokinetics/pharmacodynamics, followed by 10 mg/kg dosing. The primary objective is to determine the safety and maximum tolerated dose (MTD); secondary objectives include pharmacokinetics, immunogenicity, and best overall response. Results: Nineteen heavily pretreated patients with ECOG 0–1 have received M7824. Grade ≥3 treatment-related adverse events occurred in four patients (skin infection secondary to localized bullous pemphigoid, asymptomatic lipase increase, colitis with associated anemia, and gastroparesis with hypokalemia). The MTD was not reached. M7824 saturated peripheral PD-L1 and sequestered any released plasma TGFβ1, -β2, and -β3 throughout the dosing period at >1 mg/kg. There were signs of efficacy across all dose levels, including one ongoing confirmed complete response (cervical cancer), two durable confirmed partial responses (PR; pancreatic cancer; anal cancer), one near-PR (cervical cancer), and two cases of prolonged stable disease in patients with growing disease at study entry (pancreatic cancer; carcinoid). Conclusions: M7824 has a manageable safety profile in patients with heavily pretreated advanced solid tumors. Early signs of efficacy are encouraging, and multiple expansion cohorts are ongoing in a range of tumors. Clin Cancer Res; 24(6); 1287–95. ©2018 AACR.

Phase I Study of a Poxviral TRICOM-Based Vaccine Directed Against the Transcription Factor Brachyury

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.

Detection and Characterization of Circulating Tumour Cells from Frozen Peripheral Blood Mononuclear Cells

Retrospective analysis of patient tumour samples is a cornerstone of clinical research. CTC biomarker characterization offers a non-invasive method to analyse patient samples. However, current CTC technologies require prospective blood collection, thereby reducing the ability to utilize archived clinical cohorts with long-term outcome data. We sought to investigate CTC recovery from frozen, archived patient PBMC pellets. Matched samples from both mCRPC patients and mock samples, which were prepared by spiking healthy donor blood with cultured prostate cancer cell line cells, were processed “fresh” via Epic CTC Platform or from “frozen” PBMC pellets. Samples were analysed for CTC enumeration and biomarker characterization via immunofluorescent (IF) biomarkers, fluorescence in-situ hybridization (FISH) and CTC morphology. In the frozen patient PMBC samples, the median CTC recovery was 18%, compared to the freshly processed blood. However, abundance and localization of cytokeratin (CK) and androgen receptor (AR) protein, as measured by IF, were largely concordant between the fresh and frozen CTCs. Furthermore, a FISH analysis of PTEN loss showed high concordance in fresh vs. frozen. The observed data indicate that CTC biomarker characterization from frozen archival samples is feasible and representative of prospectively collected samples.