Phase II trial of GM-CSF in advanced prostate cancer

The role of ketoconazole in current prostate cancer care

Ketoconazole is a nonselective steroid 17α-hydroxylase/17,20 lyase (CYP17A1) inhibitor that has been used, off-label, as a second-line therapy for castration-resistant prostate cancer (CRPC). The drug has shown clinical efficacy without survival benefit. Despite not improving survival, ketoconazole has beneficial characteristics, such as its low cost, a relatively favourable toxicity profile compared with chemotherapy, and its efficacy both before and after chemotherapy. The approval of several new, highly effective treatments, including abiraterone acetate, enzalutamide, and apalutamide, warrants re-evaluation of the role of ketoconazole and other classic agents in achieving the optimal timing and sequencing of available agents to prolong survival and maintain patients' quality of life. In the current CRPC treatment landscape, we believe that ketoconazole can be considered in patients with nonmetastatic CRPC and in those with metastatic CRPC who do not respond to, tolerate, or have access to chemotherapy and other standard therapeutic options.

Optimizing the use of docetaxel in men with castration-resistant metastatic prostate cancer

In 2009, castration-resistant metastatic prostate cancer continues to account for more deaths in US men than any other cancer apart from lung cancer. Although novel targeted molecular, hormonal and immunologic agents are accelerating in their development in this disease, docetaxel and prednisone remain the standard palliative regimen for the majority of men who have progressed despite hormonal therapies. Thus, understanding the practical and often subtle issues of docetaxel initiation, duration of therapy, cessation of therapy and treatment holidays is critical for the informed use of this US Food and Drug Administration-approved regimen. In this review we address these topics in light of prognostic and predictive factors to help guide the rational use of docetaxel chemotherapy in men with this aggressive disease.

MVA-MUC1-IL2 vaccine immunotherapy (TG4010) improves PSA doubling time in patients with prostate cancer with biochemical failure

PURPOSE

TG4010 is a recombinant MVA vector expressing the tumor-associated antigen MUC1 and IL2. We explored the effect two schedules of TG4010 on PSA in men with PSA progression.

PATIENTS AND METHODS

A randomized phase II trial was conducted in 40 patients with PSA progression. Patients had PSA doubling times less than 10 months, with no overt evidence of disease. Patients received either weekly subcutaneous injection (sc) of TG4010 10(8) pfu for 6 weeks, then one injection every 3 weeks or sc injection of TG4010 10(8) pfu every 3 weeks.

RESULTS

The primary endpoint of a 50% decrease in PSA values from baseline was not observed. Nevertheless, 13 of 40 patients had a more than two fold improvement in PSA doubling time. Ten patients had their PSA stabilized for over 8 months. Therapy was well tolerated.

CONCLUSIONS

Although the primary endpoint was not achieved, there is evidence of biologic activity of TG4010 in patients with PSA progression, further investigation in prostate cancer is warranted.

Phase II Clinical Trial of GM-CSF Treatment in Patients with Hormone-Refractory or Hormone-Naïve Adenocarcinoma of the Prostate

The objective of this Phase II clinical trial was to determine the effects of chronic GM-CSF dosing on PSA levels in men with hormone-refractory or hormone-naïve prostate cancer. Six hormone-refractory and 10 hormone-naïve patients were recruited from an institutional practice and were treated with 250 and 125 μg/m² of GM-CSF, respectively, 3 times per week for continuous 12-week treatment cycles until evidence of disease progression, as indicated by 2 consecutive rising PSA levels. PSA levels were measured every 6 weeks. Of the 6 hormone-refractory patients, 2 were classified with progressive disease after 4 months and 1 after 1.75 months. The best PSA responses for the remaining 3 patients were 3%, 12%, and 32% declines which lasted from 1.75 to 8.5 months. Of the 10 hormone-naïve patients, 2 were classified with progressive disease after 3 and 12 months, and 1 patient met the criteria for stable disease after 7.75 months. The best PSA response for the remaining 7 patients ranged from 7% to 42% declines which lasted from 0.5 to 10 months. These results indicate that further study of GM-CSF administration is not warranted for hormone-refractory patients but is recommended for hormone-naïve patients using a chronic dosing regimen.

[Active immunotherapy of prostate cancer with a focus on dendritic cells]

Recurrent or metastatic prostate cancer is generally considered an incurable disease. Given the transient benefit from hormone deprivation therapy and limited successes of systemic chemotherapy, alternative treatment modalities are needed both in the situation of PSA recurrence and in hormone-refractory disease. Prostate cancer cells express several tumor associated antigens which are currently being evaluated as targets for active and specific immunotherapy approaches. Dendritic cells (DC) are the most powerful antigen-presenting cells (APC), able to prime naive T cells and to break peripheral tolerance and thus induce tumor immune responses. Close to 1000 prostate cancer patients have been treated with DC-based or other forms of active immunotherapy to date. Vaccination-induced immune responses have been reported in two thirds of DC trials, and favorable changes in the clinical course of the disease in almost half of the patients treated. Most responses, however, were modest and transient. Therefore, mechanisms of treatment failure and possibilities to improve vaccination efficacy are being discussed.

Combining gene and immunotherapy for prostate cancer

The nitroreductase (NR)/CB1954 enzyme prodrug system has given promising results in pre-clinical studies and is currently being assessed in phase I and II clinical trials in prostate cancer. Enhanced cell killing by apparent immune-mediated mechanisms has been shown in pancreatic and colorectal cancer models, by co-expressing murine granulocyte macrophage colony-stimulating factor (GM-CSF) with NR in a single replication deficient adenoviral vector. This consists of the CMV immediate early promotor driving expression of NR, with an internal ribosome entry site (IRES) and the gene for murine GM-CSF (mGM-CSF). To examine if similar enhancement of tumour cell killing could be produced in prostate cancer, the TRAMP model was chosen. Results illustrate that the combination of suicide gene therapy using NR and CB1954, with cytokine stimulation with mGM-CSF gives an improved response compared with either modality alone. The mechanism of this improved response is however likely to be non-immune based as it lacks a memory effect.

Cellular immunotherapies for prostate cancer

Prostate cancer is currently the most commonly diagnosed malignancy, and the second leading cause of cancer-related death, in men in the United States. Most deaths from prostate cancer are due to metastatic disease that no longer responds to androgen deprivation. There have been several advances within the last decade leading to the approval of new agents for treating patients with castration-resistant prostate cancer. However, these agents can have significant side effects, and the average survival benefit from chemotherapy has been modest. Results from several clinical trials have suggested that immune-based therapies may have clinical benefits in patients with prostate cancer with significantly fewer adverse events. These new therapies, however, pose new potential benefits and risks. We review here two cellular immunotherapies furthest in clinical development for prostate cancer, and discuss the potential challenges to the treating oncologist with the possible advent of these new therapies.

Prostate cancer immunotherapy

PURPOSE OF REVIEW

Basic immunology research over several decades has led to an improved understanding of tumor recognition by components of the immune system and mechanisms of tumor evasion from immune detection. These findings have ultimately led to four phase III trials, currently underway, evaluating antitumor active immunotherapies in patients with prostate cancer. This article reviews recent published findings in the area of prostate cancer immunotherapies, focusing on both passive and active immunotherapy approaches that have entered clinical trials.

RECENT FINDINGS

Clinical trials with immune active agents reported in the last year have demonstrated efficacy in the treatment of prostate cancer. These agents include immune modulators such as granulocyte-macrophage colony stimulating factor and anticytotoxic T-lymphocyte-associated antigen 4 monoclonal antibodies, antibody therapies targeting prostate-specific membrane antigen, and vaccines such as those targeting prostatic acid phosphatase, prostate-specific antigen, and cellular vaccines expressing granulocyte-macrophage colony stimulating factor.

SUMMARY

Results from several recent clinical trials have suggested that immune-based therapies have clinical benefit in patients with prostate cancer with potentially less toxicity than traditional systemic treatments. We review recent reports of immunotherapies being evaluated in patients with prostate cancer, and highlight the direction for these therapies in combination with other immunotherapies and other traditional therapies.

Vaccination therapy in prostate cancer

Radical prostatectomy and radiation therapy provide excellent localized prostate cancer (PC) control. Although the majority of prostate carcinoma is nowadays diagnosed at early stages with favourable risk features, in patients up to 30-40% it recurs within 10 years. Furthermore, the lack of effective therapies, once prostate carcinoma becomes refractory to androgen deprivation, mandates the development of alternative therapeutic options. There is a growing interest in harnessing the potency and specificity of anti-tumour immunity through the generation of fully competent dendritic cells and tumour reactive effector lymphocytes. Several strategies to treat or prevent the development of metastatic PC have been explored in clinical trials and are summarized in this review, considering also the feasibility and safety of these approaches. In some cases clinical responses were achieved showing that vaccine-primed T cells induced anti-tumour activity in vivo. The present findings and perspectives of the immunologic interventions in PC patients will be discussed.

Intermittent chemotherapy for metastatic hormone refractory prostate cancer

While docetaxel/prednisone chemotherapy has demonstrated a survival advantage in metastatic hormone refractory prostate cancer (HRPC) patients, the optimal duration of chemotherapy has not yet been established. Currently, a standard practice is to treat patients indefinitely until unacceptable toxicity or disease progression. A systematic approach to providing breaks in treatment schedules (intermittent chemotherapy) for patients who experience an initial response to chemotherapy may avoid or delay the development of progressive toxicity. Whether continuous therapy offers an advantage over intermittent therapy, in terms of balancing disease control and overall survival with treatment-related toxicities and quality-of-life (QOL) is yet unanswered. This article will: (1) review the data from prior studies of intermittent versus continuous chemotherapy in other solid tumors, (2) review existing trials of intermittent chemotherapy in prostate cancer, (3) discuss intermittent chemotherapy clinical trial design considerations, and (4) discuss the future role of intermittent chemotherapy for the treatment of prostate cancer.

Future innovations in treating advanced prostate cancer

Many novel techniques for the treatment of prostate cancer are being aggressively investigated because prostate cancer is prevalent in the population and the current treatments for advanced prostate cancer are woefully inadequate. Although the current treatment options prolong life, most patients will eventually experience local recurrence or develop advanced disease. A greater understanding of the molecular events underlying cancer has enabled investigators to explore gene therapy approaches that are targeted against these molecular events. This article discusses antiangiogenic therapy, immune based therapy, and gene therapy. Any of these experimental modalities could be developed to replace hormone ablation therapy which causes unpleasant side effects, decreases the quality of life of the patient, and only temporarily controls the disease.

Immunomodulatory effects of human recombinant granulocyte-macrophage colony-stimulating factor (rhuGM-CSF): evidence of antitumour activity

Human recombinant granulocyte-macrophage colony-stimulating factor (rhuGM-CSF) is traditionally used as supportive care for patients undergoing cytotoxic chemotherapy or haematopoietic cell progenitor mobilisation. Emerging evidence suggests rhuGM-CSF, through activity on monocytes and dendritic cells, acts as a potent modulator of immune responses and has the ability to recruit inflammatory cells and cytokines to local and systemic sites of infection. The immunomodulatory effects of rhuGM-CSF suggest the potential to enhance innate and acquired immune responses against tumour-related antigens. Enhancement of innate antitumour immunity, especially in the context of minimal residual disease, is of central importance and presents the potential for meaningful contributions to long-term disease survival. This article discusses the immunomodulatory effects of rhuGM-CSF in the context of single-agent therapy in solid tumours, as well as combination therapy in lymphoma. In addition, dendritic cell modulation with rhuGM-CSF in haematopoietic progenitor grafts and rhuGM-CSF-transduced tumour vaccines will be discussed.

Immune-based therapies for prostate cancer

Prostate cancer is a leading cause of cancer morbidity and mortality in the United States. Animal and clinical studies performed four decades ago suggested that immunological approaches might be useful for the treatment of prostate cancer. The wealth of information that has been learned over the last two decades has suggested many new directions to the immune-based therapy of prostate cancer, including passive and active immunotherapy approaches. The findings from current trials, and the likely combination of current immunotherapy approaches with conventional therapies, portends a hopeful future for the treatment of prostate cancer.

Novel cytotoxic and biological agents for prostate cancer: Where will the money be in 2005?

In 2004, docetaxel-based chemotherapy became the first treatment capable of extending life in androgen-independent prostate cancer. The era of therapeutic nihilism in this disease has thus been put to rest and a broad range of agents is being tested with the goal of improving on the successes of 2004. Lessons learned from other tumour types will need to be applied to prostate cancer in order to harness the bounty of available ideas. Target amplification or activating mutations and not merely the presence of a target are likely to be important to the success of targeted agents. Thus, the promise of the current crop of targeted agents is most likely to be realised when pursued in the context of well-credentialed targets and tested in highly translational clinical trials that are capable not only of assessing tumour response, but also of evaluating the status of the targeted pathway. The most promising agents in clinical development are reviewed.

Phase II trial of GM-CSF + thalidomide in patients with androgen-independent metastatic prostate cancer

BACKGROUND

Androgen-independent metastatic prostate cancer is a major therapeutic dilemma. Granulocyte-macrophage colony stimulating factor (GM-CSF) and thalidomide have some biologic activity as single agents in this disease subset. We performed a Phase II trial of this combination to assess its toxicity and potential utility as an immunomodulatory approach to management of advanced prostate cancer.

METHODS

Twenty-two patients were treated with GM-CSF 250 microg administered SC on Monday, Wednesday and Friday of each week. Thalidomide was escalated to reach the study dose of 200 mg/day. Patients were assessed every 4 weeks with therapy continuing to a maximum of 6 months.

RESULTS

All 22 patients had a decrement in PSA at 2 weeks postinitiation of therapy. Five patients had a > or =50% decline (56, 64,66,66, and 94%, respectively) from baseline verified at 4 weeks post best response. This corresponds to an observed response rate of 23% (95% confidence interval 8-45%). Therapy was well tolerated with the majority of patients experiencing only one event.

CONCLUSIONS

The combination of GM-CSF + thalidomide is relatively well tolerated and has the potential to produce antitumor activity in a population of patients with metastatic, androgen independent prostate cancer. This nonchemotherapy combination should be explored in a subset of patients with less advanced disease.

Immunotherapy for urological malignancies

PURPOSE

For decades urologists have successfully used immunotherapy in the battle against cancer. Interleukin-2 in renal cell carcinoma and bacillus Calmette-Guerin in bladder cancer are standard primary and/or adjunctive therapies for these diseases. Recent advances in our understanding of mechanisms governing immune system activation have fostered a myriad of novel immunotherapeutic approaches that show great promise in vivo but have had limited success in human trials to date. This review highlights current immunotherapy strategies that may prove to be successful treatments for urological cancers.

MATERIALS AND METHODS

We performed a MEDLINE literature search for articles relating to immunotherapy in bladder, prostate and renal cell carcinoma in animals and humans. We included the most promising developments in this review.

RESULTS

In addition to combining existing therapies to improve their efficacy, novel approaches that attempt to exploit the immune system ability to identify, target and eradicate malignancies are now being developed. These therapies include the use of antitumoral monoclonal and bi-specific antibodies, manipulation of T-lymphocyte costimulatory molecules and the administration of newly discovered cytokines as well as the development of antitumor vaccines.

CONCLUSIONS

To date the full potential of immunotherapy for the treatment of urological malignancies has not been recognized. As our knowledge of the immune system expands, so too may our ability to manipulate it to affect tumor regression. This review describes the most recent and most promising developments in immunotherapy for urological malignancies.

The potential for prostate cancer immunotherapy

The components of an effective immune response have been elucidated in recent years. An understanding of the dysfunctional immune response in cancer in one or more of these components has lead to a variety of immunotherapeutic approaches. These therapeutic strategies are designed to stimulate dendritic cell (DC) proliferation, promote antigen uptake and processing, stimulate an effector cell response via direct antigen presentation or target tumor cells via antibody therapy. Many approaches in prostate cancer have demonstrated successful induction of the desired immune response. Limited clinical success has also been seen.

Modulation of antitumor immune responses by hematopoietic cytokines

BACKGROUND

Advances in immunotherapy for the treatment of patients with malignant disease have led to increasingly successful use of these methods in the clinical setting. This review presents findings from recent studies that have explored improved methods for the presentation of tumor-associated antigens and for the restoration of tumor specific immune responses using cytokine therapy.

METHODS

A review of human clinical trial research on immune cytokines from 1995 (MEDLINE) to the present was conducted. Particular attention was focused on articles that reported results from Phase II or later clinical studies in patients with malignant disease.

RESULTS

The defects in cellular immunity commonly seen in patients with malignancies often are expressed as tumor specific anergy. Reversing patient tolerance to tumor antigens may be accomplished by treatment with immunoregulatory cytokines, such as Flt-3 and granulocyte-macrophage-colony stimulating factor, that mature and activate dendritic cells. Published clinical studies indicate that granulocyte-macrophage-colony stimulating factor stimulates antigen-presenting cells and has promising antitumor activity as an adjunct or as stand-alone therapy for patients with malignant disease, including leukemia, melanoma, breast carcinoma, prostate carcinoma, and renal cell carcinoma.

CONCLUSIONS

Immune-modulating cytokines may be used alone or in combination with other treatments to help restore immune function, improve response to tumor-associated antigens, and reduce the toxic effects of standard antitumor therapies. The evolving understanding of how dendritic cells regulate immune responses and promising results from published studies of immune-enhancing cytokines in the treatment of patients with malignant disease support the conduct of randomized clinical trials to confirm the clinical benefit of these immunotherapeutic strategies.

What's new in the treatment of advanced prostate cancer?

Increased insight into the biology of prostate cancer and the emergence of new therapeutic strategies and chemotherapeutic agents has changed approaches in treating patients with advanced prostate cancer. After secondary hormonal manipulations, new approaches include: second-line hormonal therapy, chemotherapy, immunotherapy with granulocyte macrophage-colony stimulating factor (GM-CSF) therapy, dendritic cell therapy, gene vaccination therapy, inhibition and/or blockade of growth factor receptors or growth factor receptor pathways, inhibition of neo-angiogenesis and inhibition of invasion and metastases.

Prostate-specific antigen kinetics as a measure of the biologic effect of granulocyte-macrophage colony-stimulating factor in patients with serologic progression of prostate cancer

PURPOSE

To determine the biologic effect of granulocyte-macrophage colony-stimulating factor (sangramostim, GM-CSF; Immunex Corporation, Seattle, WA) as measured by prostate-specific antigen (PSA) kinetics in patients with serologic progression of prostate cancer after definitive local therapy.

PATIENTS AND METHODS

Patients with prostate cancer who had undergone previous definitive surgical or radiation therapy with nonmetastatic, recurrent disease as manifested by a rising PSA between 0.4 ng/mL and 6.0 ng/mL were enrolled on this phase II trial. Patients received 250 micro g/m(2)/day of subcutaneous GM-CSF on days 1 through 14 of a 28-day cycle. PSA was measured at day 1 of each cycle.

RESULTS

Thirty patients with serologic progression of prostate cancer were treated. The median pretreatment PSA was 2.9 ng/mL. Of the 29 evaluable patients, three patients (10%; 95% confidence interval, 2% to 27%) achieved a 50% reduction in PSA. For the patients (n = 26) in whom the on-treatment PSA doubling time could be calculated, the median PSA doubling time increased from 8.4 months to 15 months (P =.001), and the median slope of the PSA versus time curve decreased with treatment (P =.004). Therapy was well tolerated by all patients, with an average treatment duration of 16.5 cycles (range, 5 to 33).

CONCLUSION

GM-CSF has a biologic effect in patients with serologic progression of prostate cancer after definitive local therapy, as measured by PSA declines and modulation of PSA kinetics.