Ravi A. Madan

Ipilimumab and a poxviral vaccine targeting prostate-specific antigen in metastatic castration-resistant prostate cancer: a phase 1 dose-escalation trial

BACKGROUND Therapeutic cancer vaccines have shown activity in metastatic castration-resistant prostate cancer (mCRPC), and methods are being assessed to enhance their efficacy. Ipilimumab is an antagonistic monoclonal antibody that binds cytotoxic T-lymphocyte-associated protein 4, an immunomodulatory molecule expressed by activated T cells, and to CD80 on antigen-presenting cells. We aimed to assess the safety and tolerability of ipilimumab in combination with a poxviral-based vaccine targeting prostate-specific antigen (PSA) and containing transgenes for T-cell co-stimulatory molecule expression, including CD80. METHODS We did a phase 1 dose-escalation trial, with a subsequent expansion phase, to assess the safety and tolerability of escalating doses of ipilimumab in combination with a fixed dose of the PSA-Tricom vaccine. Patients with mCRPC received 2×10(8) plaque-forming units of recombinant vaccinia PSA-Tricom subcutaneously on day 1 of cycle 1, with subsequent monthly boosts of 1×10(9) plaque-forming units, starting on day 15. Intravenous ipilimumab was given monthly starting at day 15, in doses of 1, 3, 5, and 10 mg/kg. Our primary goal was to assess the safety of the combination. This study is registered with ClinicalTrials.gov, number NCT00113984. FINDINGS We completed enrolment with 30 patients (24 of whom had not been previously treated with chemotherapy) and we did not identify any dose-limiting toxic effects. Grade 1 and 2 vaccination-site reactions were the most common toxic effects: three of 30 patients had grade 1 reactions and 26 had grade 2 reactions. 21 patients had grade 2 or greater immune-related adverse events. Grade 3 or 4 immune-related adverse events included diarrhoea or colitis in four patients and grade 3 rash (two patients), grade 3 raised aminotransferases (two patients), grade 3 endocrine immune-related adverse events (two patients), and grade 4 neutropenia (one patient). Only one of the six patients previously treated with chemotherapy had a PSA decline from baseline. Of the 24 patients who were chemotherapy-naive, 14 (58%) had PSA declines from baseline, of which six were greater than 50%. INTERPRETATION The use of a vaccine targeting PSA that also enhances co-stimulation of the immune system did not seem to exacerbate the immune-related adverse events associated with ipilimumab. Randomised trials are needed to further assess clinical outcomes of the combination of ipilimumab and vaccine in mCRPC. FUNDING US National Institutes of Health.

Tumor regression and growth rates determined in five intramural NCI prostate cancer trials. The growth rate constant as an indicator of therapeutic efficacy.

PURPOSE In solid tumors such as prostate cancer, novel paradigms are needed to assess therapeutic efficacy. We utilized a method estimating tumor growth and regression rate constants from serial PSA measurements, and assessed its potential in patients with metastatic castration resistant prostate carcinoma (mCRPC). EXPERIMENTAL DESIGN Patients were enrolled in five phase II studies, including an experimental vaccine trial, representing the evolution of therapy in mCRPC. PSA measurements obtained before, and during, therapy were used. Data analysis using a two-phase mathematical equation yielded concomitant PSA growth and regression rate constants. RESULTS Growth rate constants (g) can be estimated while patients receive therapy and in such patients g is superior to PSA-DT in predicting OS. Incremental reductions in growth rate constants were recorded in successive trials with a 10-fold slower g in the most recent combination therapy trial (log g = 10(-3.17)) relative to single-agent thalidomide (log g = 10(-2.08)) more than a decade earlier. Growth rate constants correlated with survival, except in patients receiving vaccine-based therapy where the evidence demonstrates prolonged survival presumably due to immunity developing subsequent to vaccine administration. CONCLUSION Incremental reductions in tumor growth rate constants suggest increased efficacy in successive chemotherapy trials. The derived growth rate constant correlates with survival, and may be used to assess efficacy. The PSA-TRICOM vaccine appears to have provided marked benefit not apparent during vaccination, but consistent with subsequent development of a beneficial immune response. If validated as a surrogate for survival, growth rate constants would offer an important new efficacy endpoint for clinical trials.Purpose: In solid tumors such as prostate cancer, novel paradigms are needed to assess therapeutic efficacy. We utilized a method estimating tumor growth and regression rate constants from serial PSA measurements, and assessed its potential in patients with metastatic castration resistant prostate carcinoma (mCRPC). Experimental Design: Patients were enrolled in five phase II studies, including an experimental vaccine trial, representing the evolution of therapy in mCRPC. PSA measurements obtained before, and during, therapy were used. Data analysis using a two-phase mathematical equation yielded concomitant PSA growth and regression rate constants. Results: Growth rate constants (g) can be estimated while patients receive therapy and in such patients g is superior to PSA-DT in predicting OS. Incremental reductions in growth rate constants were recorded in successive trials with a 10-fold slower g in the most recent combination therapy trial (log g = 10−3.17) relative to single-agent thalidomide (log g = 10−2.08) more than a decade earlier. Growth rate constants correlated with survival, except in patients receiving vaccine-based therapy where the evidence demonstrates prolonged survival presumably due to immunity developing subsequent to vaccine administration. Conclusion: Incremental reductions in tumor growth rate constants suggest increased efficacy in successive chemotherapy trials. The derived growth rate constant correlates with survival, and may be used to assess efficacy. The PSA-TRICOM vaccine appears to have provided marked benefit not apparent during vaccination, but consistent with subsequent development of a beneficial immune response. If validated as a surrogate for survival, growth rate constants would offer an important new efficacy endpoint for clinical trials. Clin Cancer Res; 17(4); 907–17. ©2010 AACR.

Prostvac-VF: a vector-based vaccine targeting PSA in prostate cancer

Prostvac is a prostate cancer vaccine regimen consisting of a recombinant vaccinia vector as a primary vaccination, followed by multiple booster vaccinations employing a recombinant fowlpox vector. Both vectors contain the transgenes for prostate-specific antigen (PSA) and multiple T-cell co-stimulatory molecules (TRICOM). The PSA-TRICOM vaccines infect antigen-presenting cells (APCs) and generate proteins that are expressed on the surface of the APCs in an immune context. The interaction of these APCs with T cells initiates a targeted immune response and T cell-mediated tumor cell destruction. Preliminary clinical trials have indicated negligible toxicity, and Phase II trials have suggested a survival benefit after treatment with Prostvac, especially in patients with indolent disease characteristics. Preclinical and clinical data indicate that radiation, hormonal therapy, and chemotherapy may be combined with Prostvac to enhance the vaccines efficacy. Additional strategies are in development to further enhance the clinical benefits of Prostvac, and a Phase III trial is being planned in metastatic castration-resistant prostate cancer.

Phase II Trial of Bevacizumab, Thalidomide, Docetaxel, and Prednisone in Patients With Metastatic Castration-Resistant Prostate Cancer

PURPOSE We previously demonstrated that thalidomide appears to add to the activity of docetaxel in metastatic castration-resistant prostate cancer (CRPC). Phase II studies combining docetaxel with bevacizumab have had substantial antitumor activity. We hypothesized that the combination of docetaxel plus these antiangiogenic drugs with different targets would have substantial clinical activity. To explore safety and efficacy, this was tested in mice and in human patients. PATIENTS AND METHODS Preclinical efficacy of the combination therapy was evaluated in PC3 xenograft mice. Sixty patients with progressive metastatic CRPC received intravenous docetaxel and bevacizumab plus oral thalidomide and prednisone. The primary end point was a prostate-specific antigen (PSA) decline of > or = 50%. Secondary end points included time to progression, overall survival, and safety. Results In the mouse model, combination therapy of docetaxel, bevacizumab, and thalidomide inhibited tumor growth most effectively. In the clinical trial, 90% of patients receiving the combination therapy had PSA declines of > or = 50%, and 88% achieved a PSA decline of > or = 30% within the first 3 months of treatment. The median time to progression was 18.3 months, and the median overall survival was 28.2 months in this group with a Halabi-predicted survival of 14 months. While toxicities were manageable, all patients developed grade 3/4 neutropenia. CONCLUSION The addition of bevacizumab and thalidomide to docetaxel is a highly active combination with manageable toxicities. The estimated median survival is encouraging, given the generally poor prognosis of this patient population. These results suggest that definitive clinical trials combining antiangiogenic agent combinations with docetaxel are warranted to improve treatment outcomes for patients with metastatic CRPC.

Analysis of Overall Survival in Patients with Nonmetastatic Castration-Resistant Prostate Cancer Treated with Vaccine, Nilutamide, and Combination Therapy

Purpose: We reported previously the first randomized study of any kind in patients with nonmetastatic, castrate-resistant prostate cancer. The study employed vaccine, the hormone nilutamide, and the combined therapy (crossover for each arm) with an endpoint of time to progression. We now report survival analyses at 6.5 years from the initiation of therapy with a median potential follow-up of 4.4 years. Experimental Design: Forty-two patients were randomized to receive either a poxvirus-based prostate-specific antigen (PSA) vaccine or nilutamide. Patients in either arm who developed increasing PSA without radiographic evidence of metastasis could cross over to receive the combined therapies. Results: Median survival among all patients was 4.4 years from date of enrollment. Median survival exhibited a trend toward improvement for patients initially randomized to the vaccine arm (median, 5.1 versus 3.4 years; P = 0.13). Starting from the on-study date, the retrospectively determined subset of 12 patients who initially received vaccine and then later received nilutamide suggested improved survival compared with the 8 patients who began with nilutamide and subsequently were treated with vaccine (median, 6.2 versus 3.7 years; P = 0.045). A subgroup analysis of patients randomized to the vaccine arm versus the nilutamide arm showed substantial improvements in survival if at baseline patients had a Gleason score <7 (P = 0.033) and PSA <20 ng/dL (P = 0.013) or who had prior radiation therapy (P = 0.018). Conclusions: These data indicate that patients with nonmetastatic castration-resistant prostate cancer (D0.5) who receive vaccine before second-line hormone therapy may potentially result in improved survival compared with patients who received hormone therapy and then vaccine. These data also suggest that patients with more indolent disease may derive greater clinical benefit from vaccine alone or vaccine before second-line hormone therapy compared with hormone therapy alone or hormone therapy followed by vaccine. These findings have potential implications for both the design and endpoint analysis of larger vaccine combination therapy trials.

Therapeutic Cancer Vaccines in Prostate Cancer: The Paradox of Improved Survival Without Changes in Time to Progression

Therapeutic cancer vaccines represent a new class of agents in the treatment of cancer. Sipuleucel-T is an antigen-presenting cell-based vaccine that recently demonstrated a significant 4.8-month improvement in overall survival in advanced prostate cancer patients and was well tolerated. The findings of that study have been met with skepticism, primarily because the agent did not change initial disease progression and yet led to longer survival. Although the commonly accepted treatment paradigm suggests that treatments should initially decrease tumor volume, perhaps vaccines work differently. Vaccines may induce delayed responses not seen in the first few months of therapy or they may initiate a dynamic immune response that ultimately slows the tumor growth rate, resulting in longer survival. Subsequent therapies may also combine with the induced immune response, resulting in a combination that is more effective than conventional treatments alone. Also, other treatments may alter tumor-associated antigen expression, enhancing the immune response. Future trials are currently planned to investigate these hypotheses; however, the results of the sipuleucel-T vaccine in prostate cancer should not be dismissed. Results with another vaccine in prostate cancer are similar, perhaps suggesting a class effect. In a broader context, clinicians may need to reconsider how they measure success. Several agents have been approved that produce superior disease progression results, but do not affect overall survival. Given the toxicity and costs of cancer therapies, perhaps studies should put more weight on long-term survival endpoints than on short-term endpoints that may be less consequential.

A Pilot Study of MUC-1/CEA/TRICOM Poxviral-Based Vaccine in Patients with Metastatic Breast and Ovarian Cancer

Purpose: PANVAC is a recombinant poxviral vaccine that contains transgenes for MUC-1, CEA, and 3 T-cell costimulatory molecules. This study was conducted to obtain preliminary evidence of clinical response in metastatic breast and ovarian cancer patients. Experimental design: Twenty-six patients were enrolled and given monthly vaccinations. Clinical and immune outcomes were evaluated. Results: These patients were heavily pretreated, with 21 of 26 patients having 3 or more prior chemotherapy regimens. Side effects were largely limited to mild injection-site reactions. For the 12 breast cancer patients enrolled, median time to progression was 2.5 months (1–37+) and median overall survival was 13.7 months. Four patients had stable disease. One patient had a complete response by RECIST and remained on study for 37 months or more, with a significant drop in serum interleukin (IL)-6 and IL-8 by day 71. Another patient with metastatic disease confined to the mediastinum had a 17% reduction in mediastinal mass and was on study for 10 months. Patients with stable or responding disease had fewer prior therapies and lower tumor marker levels than patients with no evidence of response. For the ovarian cancer patients (n = 14), the median time to progression was 2 months (1–6) and median overall survival was 15.0 months. Updated data are presented here for one patient treated with this vaccine in a previous trial, with a time to progression of 38 months. Conclusions: Some patients who had limited tumor burden with minimal prior chemotherapy seemed to benefit from the vaccine. Further studies to confirm these results are warranted. Clin Cancer Res; 17(22); 7164–73. ©2011 AACR.

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.

Elevated serum soluble CD40 ligand in cancer patients may play an immunosuppressive role.

Tumor cells can induce certain cytokines and soluble receptors that have a suppressive effect on the immune system. In this study, we showed that an extracellular portion of a membrane-bound ligand of CD40 (soluble CD40 ligand; sCD40L) was significantly elevated in the serum of cancer patients compared with healthy donors. In addition, PBMCs from cancer patients had a relatively larger population of myeloid-derived suppressor cells (MDSCs), defined as CD33(+)HLA-DR(-) cells, and these cells expressed higher levels of CD40. T-cell proliferation and IFN-γ production decreased when stimulated T cells were cocultured with an increased amount of autologous MDSCs. The addition of recombinant monomeric sCD40L enriched MDSCs and had an additive inhibitory effect on T-cell proliferation. PBMCs cultured in vitro with sCD40L also showed an expansion of regulatory T cells (CD4(+)CD25(high)Foxp3(+)), as well as induction of cytokines, such as IL-10 and IL-6. Moreover, sCD40L-induced enrichment of programmed death-1-expressing T cells was greater in cancer patients than in healthy donors. Preexisting sCD40L also inhibited IL-12 production from monocytes on activation. These data suggest that the higher levels of sCD40L seen in cancer patients may have an immunosuppressive effect.