Granulocyte-macrophage colony-stimulating factor alone or with dacarbazine in metastatic melanoma: a randomized phase II trial

Sargramostim and immune checkpoint inhibitors: combinatorial therapeutic studies in metastatic melanoma

The use of immune checkpoint inhibitors in patients with metastatic melanoma generates clinical benefit, including improved survival. Yet disease resistance and immune-related adverse events persist as unmet needs. Sargramostim, a yeast-derived recombinant human GM-CSF, has shown clinical activity against diverse solid tumors, including metastatic melanoma. Here we review the use of sargramostim for treatment of advanced melanoma. Potential sargramostim applications in melanoma draw on the unique ability of GM-CSF to link innate and adaptive immune responses. We review preclinical and translational data describing the mechanism of action of sargramostim and synergy with immune checkpoint inhibitors to enhance efficacy and reduce treatment-related toxicity.

An update on GM-CSF and its potential role in melanoma management

GM-CSF drives the differentiation of granulocytes and monocyte/macrophages from hematopoietic stem cell progenitors. It is required for differentiating monocytes into dendritic cells (DC). Although approved for recovery of granulocytes/monocytes in patients receiving chemotherapy, G-CSF is preferred. Enthusiasm for GM-CSF monotherapy as a melanoma treatment was dampened by two large randomized trials. Although GM-CSF has been injected into tumors for many years, the efficacy of this has not been tested. There is a strong rationale for GM-CSF as a vaccine adjuvant, but it appears of benefit only for strategies that directly involve DCs, such as intratumor talimogene laherparepvec and vaccines in which DCs are loaded with antigen ex vivo and injected admixed with GM-CSF.

Relative Efficacy of Granulocyte-Macrophage Colony-Stimulating Factor, Dacarbazine, and Glycoprotein 100 in Metastatic Melanoma: An Indirect Treatment Comparison

INTRODUCTION

Advances in the treatment of metastatic melanoma have been achieved in recent years: immunotherapies and targeted therapies have demonstrated survival benefits over older agents such as granulocyte-macrophage colony-stimulating factor (GM-CSF), dacarbazine, and glycoprotein peptide vaccine (gp100) in pivotal phase 3 trials. It is important to compare therapies to guide the treatment decision-making process, and establishing the relationship between older agents can strengthen the networks of evidence for newer therapies. We report the outcome of an indirect comparison of GM-CSF, dacarbazine, and gp100 in metastatic melanoma through meta-analysis of absolute treatment effect.

METHODS

A systematic literature review identified trials for inclusion in the meta-analysis. A valid network meta-analysis was not feasible: treatment-specific meta-analysis was conducted. A published algorithm was used to adjust overall survival estimates from trials of GM-CSF, dacarbazine, and gp100 for heterogeneity in baseline prognostic factors. Survival estimates were compared in three patient groups: stage IIIB-IV M1c, stage IIIB-IV M1a, and stage IV M1b/c.

RESULTS

One trial of GM-CSF, four of dacarbazine, and one of gp100 were included in the analysis. After adjusting for differences in baseline prognostic factors, median overall survival (OS) in all patient groups was longer for those receiving GM-CSF than for those receiving dacarbazine or gp100. The observed survival over time for GM-CSF was similar to the adjusted survival for dacarbazine and greater than for gp100 in all patient groups.

CONCLUSION

The relative treatment effect of GM-CSF, dacarbazine, and gp100 has been reliably estimated by adjusting for differences in baseline prognostic factors. Results suggest that OS with GM-CSF is at least as good as with dacarbazine and greater than with gp100. Given the role of these agents as controls in phase 3 trials of new immunotherapies and targeted agents, these results can be used to contextualize the efficacy of newer therapies.

FUNDING

Amgen Inc.

Stabilization of HIF-2α induces sVEGFR-1 production from tumor-associated macrophages and decreases tumor growth in a murine melanoma model

Macrophage secretion of vascular endothelial growth factor (VEGF) in response to hypoxia contributes to tumor growth and angiogenesis. In addition to VEGF, hypoxic macrophages stimulated with GM-CSF secrete high levels of a soluble form of the VEGF receptor (sVEGFR-1), which neutralizes VEGF and inhibits its biological activity. Using mice with a monocyte/macrophage-selective deletion of hypoxia-inducible factor (HIF)-1α or HIF-2α, we recently demonstrated that the antitumor response to GM-CSF was dependent on HIF-2α-driven sVEGFR-1 production by tumor-associated macrophages, whereas HIF-1α specifically regulated VEGF production. We therefore hypothesized that chemical stabilization of HIF-2α using an inhibitor of prolyl hydroxylase domain 3 (an upstream inhibitor of HIF-2α activation) would increase sVEGFR-1 production from GM-CSF-stimulated macrophages. Treatment of macrophages with the prolyl hydroxylase domain 3 inhibitor AKB-6899 stabilized HIF-2α and increased sVEGFR-1 production from GM-CSF-treated macrophages, with no effect on HIF-1α accumulation or VEGF production. Treatment of B16F10 melanoma-bearing mice with GM-CSF and AKB-6899 significantly reduced tumor growth compared with either drug alone. Increased levels of sVEGFR-1 mRNA, but not VEGF mRNA, were detected within the tumors of GM-CSF- and AKB-6899-treated mice, correlating with decreased tumor vascularity. Finally, the antitumor and antiangiogenic effects of AKB-6899 were abrogated when mice were simultaneously treated with a sVEGFR-1 neutralizing Ab. These results demonstrate that AKB-6899 decreases tumor growth and angiogenesis in response to GM-CSF by increasing sVEGFR-1 production from tumor-associated macrophages. Specific activation of HIF-2α can therefore decrease tumor growth and angiogenesis.

Hypoxia-inducible factor-2α regulates GM-CSF-derived soluble vascular endothelial growth factor receptor 1 production from macrophages and inhibits tumor growth and angiogenesis

Macrophage secretion of vascular endothelial growth factor (VEGF) in response to the hypoxic tumor microenvironment contributes to tumor growth, angiogenesis, and metastasis. We have recently demonstrated that macrophages stimulated with GM-CSF at low O(2) secrete high levels of a soluble form of the VEGF receptor 1 (sVEGFR-1), which neutralizes VEGF and inhibits its biological activity. Using small interfering RNA targeting to deplete hypoxia-inducible factor (HIF)-1α or HIF-2α in murine macrophages, we found that macrophage production of sVEGFR-1 in response to low O(2) was dependent on HIF-2α, whereas HIF-1α specifically regulated VEGF production. In our current report, we evaluated the growth of B16F10 malignant melanoma in mice with a monocyte/macrophage-selective deletion of HIF-1α or HIF-2α (HIF-1α(flox/flox)- or HIF-2α(flox/+)/LysMcre mice). GM-CSF treatment increased intratumoral VEGF and sVEGFR-1 in control mice, an effect that was associated with a decrease in microvessel density. GM-CSF treatment of HIF-1α(flox/flox)/LysMcre mice induced sVEGFR-1 but not VEGF, resulting in an overall greater reduction in tumor growth and angiogenesis compared with control mice. In addition, real-time PCR for melanoma-specific genes revealed a significantly reduced presence of lung micrometastases in HIF-1α(flox/flox)/LysMcre mice treated with GM-CSF. Conversely, GM-CSF treatment induced VEGF but not sVEGFR-1 in HIF-2α(flox/+)/LysMcre mice, and, correspondingly, GM-CSF did not decrease tumor growth, angiogenesis, or lung metastasis in these mice. This study reveals opposing roles for the HIFs in the regulation of angiogenesis by tumor-associated macrophages and suggests that administration of GM-CSF might be an effective means of inducing sVEGFR-1 and inhibiting tumor growth and angiogenesis in patients with melanoma.

Clinical uses of GM-CSF, a critical appraisal and update

The role of granulocyte-macrophage-colony-stimulating factor (GM-CSF) in the supportive care of cancer patients has been evaluated with promising results. More recently, GM-CSF has been added to regimens for the mobilization of hematopoietic progenitor cells. An expanding role for GM-CSF in regulating immune responses has been recognized based upon its activity on the development and maturation of antigen presenting cells and its capability for skewing the immune system toward Th1-type responses. GM-CSF has been shown to preferentially enhance both the numbers and activity of type 1 dendritic cells (DC1), the subsets of dendritic cells responsible for initiating cytotoxic immune responses. The increase in DC1 content and activity following local and systemic GM-CSF administration support a role for GM-CSF as an immune stimulant and vaccine adjuvant in cancer patients. GM-CSF has shown clinical activity as an immune stimulant in tumor cell and dendritic cell vaccines, and may increase antibody-dependent cellular cytotoxicity. The successful use of myeloid acting cytokines to enhance anti-tumor responses will likely require the utilization of GM-CSF in combination with cytotoxic or other targeted therapies.

GM-CSF plus antigenic peptide vaccination in locally advanced melanoma patients

Twenty-four (24) pretreated patients with relapsed high-risk resected The American Joint Committee on Cancer (AJCC) stage IIA-IV melanoma received adjuvant peptide vaccinations derived from the melanosomal antigens MelanA/MART1, MAGE-1, gp100, and tyrosinase, according to patient tumor-associated human leukocyte antigen (HLA) restricted antigen expression, in combination with granulocyte-macrophage colony-stimulating factor (GM-CSF). Pretreatment was comprised of surgery (n=23 primary tumor; n=23 metastases), local radiotherapy (n=2), immunotherapy (n=23), chemotherapy (n=10), and chemoimmunotherapy (n=1), respectively. All patients received peptide vaccines in an adjuvant setting. Seven (7) patients were relapse free for 3+ up to 25+ months. Of the patients exhibiting progressive disease (n=17), 13 patients developed metastases during vaccination (9 local, 4 distant), and 4 patients developed metastases (2 local, 2 distant) after finishing vaccine therapy. Two (2)-year local and distant metastases-free survival, 2-year distant metastases-free survival, and 2-year overall survival were calculated as 8.6%, 68%, and 85%, respectively. Vaccine treatment was well tolerated, with no severe side-effects. Twenty (20) of 24 patients developed local delayed-type hypersensitivity (DTH) reactions to synthetic peptide vaccination. Transient fever (n=2) and pain in muscle/bone (n=2) occurred rarely. In conclusion, antigenic peptide vaccination, combined with GM-CSF, is safe and may yield clinical benefits in relapsed high-risk resected melanoma patients.

Heat-inducible amplifier vector for high-level expression of granulocyte-macrophage colony-stimulating factor

PURPOSE

In cytokine immunotherapy of cancer it is critical to deliver sufficiently high local cytokine concentrations in order to reach the therapeutic threshold needed for clinical efficacy. Simultaneously, for optimal clinical safety adverse effects caused by high systemic cytokine levels must be minimized. One of the most promising anti-cancer therapeutic cytokines, granulocyte-macrophage colony-stimulating factor (GM-CSF), has elicited anti-tumour immune responses in animal studies and clinical trials. However, the clinical efficacy has been limited, with local GM-CSF levels being therapeutically insufficient and systemic toxicity being a limiting factor.

METHODS

To address these problems we have developed a novel GM-CSF expression vector, pAD-HotAmp-GM-CSF, which can provide high levels of GM-CSF expression, and induction of cytokine expression to limited tissue areas. This expression system combines inducible and amplifying elements in a single multi-genic construct. The first transcriptional unit contains the inducible element, the heat shock protein 70B (HSP70B) promoter that regulates expression of the transcription-activating factor tat.

RESULTS

Upon the binding of tat to the second promoter, the HIV2 long terminal repeat amplifies downstream gene expression of the therapeutic cytokine GM-CSF. Moderate hyperthermia at 42 degrees C for 30 min induced GM-CSF expression in pAD-HotAmp-GM-CSF that was over 2.5- and 2.8-fold higher than levels reached with HSP70B promoter alone and the prototypical human cytomegalovirus promoter.

CONCLUSIONS

Thus, the inducible amplifier vector, pAD-HotAmp-GM-CSF, represents a novel system for regulated and enhanced GM-CSF expression, which enables both greater efficacy and safety in cytokine immunotherapy of cancer.

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.

Complete remission of brain metastases in three patients with stage IV melanoma treated with BOLD and G-CSF

BACKGROUND

Brain metastases are the most life-threatening among the secondary localizations of melanoma for their unresponsiveness to the surgical, radiotherapeutic and/or chemotherapeutic treatments.

METHODS

Accidentally, we observed a complete response (CR) in a patient undergoing chemotherapy with bleomycin, vincristine or Oncovin, CCNU or lomustine, dacarbazine (BOLD) regimen for metastatic melanoma including brain metastases, who was also treated with G-CSF to manage a concomitant leukopenia. After this observation, seven more patients with stage IV melanoma with brain metastases were treated with BOLD regimen repeated every 6 weeks with administration of G-CSF in the intervals.

RESULTS

Three patients presented CR (37.5%). Two patients stopped the treatment after two courses for evident progressive disease (25%). The other three patients showed stable disease (SD: 37.5%). Median duration of SD was 24 weeks. Among the eight patients, six (75%) achieved clinical benefit. Median time to progression was 8.5 months (range 0-74+ months). Median survival was 12.5 months (range 4-74+ months). Two patients are still alive and disease-free after 74 and 57 months, respectively.

CONCLUSION

We believe that the brilliant CR, the long duration of the disease-free intervals and the long survival in at least three of eight patients should encourage further research on BOLD with G-CSF for the treatment of advanced melanoma.

Re-evaluating the role of dacarbazine in metastatic melanoma: what have we learned in 30 years?

Since dacarbazine was approved for treating metastatic melanoma in the 1970s, numerous studies have evaluated whether different schedules and dacarbazine-based combinations improve clinical outcomes. This evidence-based review shows that combining dacarbazine with other drugs having single-agent activity and/or hormonal or immunotherapeutic compounds fails to provide clinically meaningful improvements in survival, and may increase toxicity. In patients with metastatic melanoma, dacarbazine was previously administered in cycles of multiple consecutive daily infusions per cycle. The introduction of potent antiemetics, together with concerns relating to patient comfort and clinic utilisation time, has enabled regimens involving single-dose dacarbazine, administered at the same total dose per cycle. These appear to be as effective as multiple-dose schedules, are well tolerated, and are more straightforward to administer. Single-administration dacarbazine (850-1000 mg/m2), once every 3 weeks, is currently the standard reference therapy in patients with advanced melanoma. New effective therapies are urgently needed for this treatment-refractory disease.