Updates on immunotherapy in non-small cell lung cancer

Abstract

Immunotherapy has made significant progress in patients with non-small cell lung cancer (NSCLC) in the last years. Early tumor vaccine studies showed trends toward better clinical outcomes, and larger trial results are currently being awaited. Immune checkpoint inhibitors are promising therapeutic agents in advanced NSCLC. While ipilimumab, a cytotoxic T-lymphocyte antigen 4 inhibitor, has clearly improved outcomes in metastatic malignant melanoma, its safety and efficacy in NSCLC are not yet known. Programmed death-1 (PD-1) and PD-1 ligand inhibitors such as nivolumab, MK3475 and MPDL3280 have demonstrated clinical efficacy in patients with advanced/metastatic NSCLC in early clinical trials. Their validation in larger Phase III trials is anxiously being awaited. Furthermore, exploring efficacy of these molecules in patients with early stages of lung cancer is also necessary.

Keywords::

• anti-cytotoxic T-lymphocyte antigen 4
• anti-programmed death-1
• anti-programmed death-1 ligand
• cytotoxic T-lymphocyte antigen 4
• immunotherapy
• lung cancer
• programmed death-1 ligand

1. Introduction

Despite recent progress in the treatment of non-small cell lung cancer (NSCLC), lung cancer remains one of the leading causes of mortality worldwide. These advances include new agents that target specific mutations (i.e., mutated epidermal growth factor receptor and anaplastic lymphoma kinase genes, respectively) that are only present in a small subset of patients [1,2]. While these agents demonstrate valuable clinical results in patients with tumors that harbor these mutations, individuals without a known mutation are still being treated with standard chemotherapy agents that demonstrate only moderate efficacy in expense for non-negligible toxicity. Consequently, immunotherapy is an attractive option as it is not dependent on mutational status of the tumor cells and demonstrates clear efficacy with less toxicity. The recent success recorded with the use of immunotherapy for malignant melanoma and renal cell carcinoma propelled the development of immune therapy for other solid tumors including NSCLC [3,4]. Although melanoma and renal cell carcinoma are thought of as highly immunogenic malignancies, evidence for the immunogenicity of lung cancer is also emerging. Improved prognosis in NSCLC is associated with high levels of infiltrating CD4⁺/CD8⁺ effector T-cells, and worse outcomes have been documented with elevated levels of infiltrating T regulatory cells at the tumor site [5,6]. While earlier attempts at using cancer vaccine to treat NSCLC have failed to demonstrate clinical benefit and improve survival, significant advancements are now being realized with newer agents. Early clinical data using new vaccines and novel agents that block immune checkpoint molecules demonstrate significant objective response rates (ORRs). Indeed, early studies with melanoma-associated antigen-A3 (MAGE-A3) vaccine and the tumor-associated mucinous glycoprotein 1 (MUC1) vaccines have demonstrated promising results in early-stage NSCLC. In advance-stage disease, belagenumatucel-L, EGFR vaccine and TG4010 have demonstrated encouraging results in Phase II trials. Furthermore, early clinical trials using immune checkpoint inhibitors ipilimumab, BMS-936558 and MK-3475 provide new and exciting data, demonstrating significant rate of objective and clinical response. We have recently described in great depth the immune alterations, immunogenicity and recent developments in immunotherapy for NSCLC [6]. The aim of the current article is to review and discuss the advancement in immunotherapy for NSCLC, including the new data on cancer vaccines and novel agents that block immune checkpoint molecules.

2. Materials and methods

To obtain the relevant data for this review, PubMed and Medline database searches were performed using the terms ‘non-small cell lung cancer', ‘NSCLC', ‘immunotherapy', ‘PD-1', ‘CTLA-4', ‘anti-PD-1', ‘checkpoint inhibitors' and the combination of specific terms. Abstracts presented at American Society of Clinical Oncology, European Society of Medical Oncology, International Lung Cancer Symposia, International Association for the Study of Lung and Cancer and Europian Cancer Symposia between 2010 and 2013 were reviewed and thoroughly analyzed. The relevant reports were extracted and data synthetized.

3. Therapeutic cancer vaccines

Cancer vaccines are used to induce a specific T- and B-cell antitumor immune response. A crucial component of vaccine therapy is to prime the immune system against a specific protein or peptide that is overexpressed on cancer cells. We have previously described in great detail cancer vaccines currently being studied in patients with NSCLC [6]. The detailed description of the mechanism of action of each vaccine has been previously described elsewhere [7]. A summary of vaccine therapies that are currently being studied in NSCLC is presented in Table 1. Since our previous publication, a large (n = 2270) multicenter randomized Phase III study, MARGIT, of the MAGE-A3 vaccine has completed patient enrollment. Patients with resected stage IB-IIIA MAGE-A3+ were randomly assigned to receive either vaccine or placebo. The results of this study are not yet published.

Table 1. Summary of investigational vaccine therapies in NSCLC.

Vaccine therapy	Mechanism of action	Phase of clinical testing	n	Study design	Results and comments
MAGE-A3	Vaccine against MAGE-A3 tumor-specific antigen	II	182	Patients with MAGE-A3-positive resected stage IB/II NSCLC received vaccine versus placebo	DFS: HR = 0.73 (95% CI 0.45 – 1.16); OS: HR = 0.66 (95% CI 0.36 – 1.20). This study found a nonsignificant trend favoring vaccine
III	2270	Randomized double-blinded multicenter trial in patients with MAGE-A3-positive resected stage IIB–IIIA NSCLC; patients will receive either vaccine versus placebo	Primary endpoint – DFS; secondary endpoints – OS and validation of biomarkers
CimaVax-EGF	Vaccine specific against EGF	II	80	Randomized open-label study. Patients with stage IIIB/IV NSCLC received vaccine or placebo for maintenance therapy after first-line chemotherapy	Median OS of 6.5 months (vaccine) versus 5.3 months (placebo), p = 0.098
III	1464	Randomized open-label trial. Patients with unresectable stage III NSCLC will receive vaccine versus BSC	START trial is currently ongoing. Primary endpoint is OS; secondary endpoint is safety
L-BLP25 (tecemotide)	Vaccine against MUC1 glycoprotein	III	1513	Randomized double-blinded, placebo controlled clinical trial in patients with unresectable stage III NSCLC after CRT (START trial)	Median OS of 25.6 months (vaccine) versus 22.3 months (HR = 0.88, 95% CI 0.75 – 1.03, p = 0.123) Patients receiving the vaccine with sequential rather than concurrent chemotherapy derived some benefit. OS was 30.8 months versus 20.6 months. HR = 0.88 (95% CI 0.64 – 0.95, p = 0.016)
Belagenpumatucel-L (Lucanix)	Incorporates antisense TGF-β2 into allogeneic cancer cells, thus blocking the action of TGF-β2	III	532	Randomized double-blinded clinical trial in patients with stage IIIB/IV NSCLC (STOP trial). Patients received vaccine versus placebo as maintenance therapy after platinum doublet chemotherapy	Median OS: 20.3 months (vaccine) versus 17.8 months (placebo) (HR = 0.54; p = 0.0595) Improvement in OS was noted in the group that received Lucanix within 12 weeks of stopping chemotherapy when compared with the group who were vaccinated > 12 weeks after stopping chemotherapy (OS 20.7 vs 13.3 [p = 0.0092])
TG4010	Vaccine against the MUC1 glycoprotein and IL-2	II	148	Randomized trial in MUC-1-positive patients. Patients received first-line cisplatin/gemcitabine followed by vaccine versus doublet chemotherapy as maintenance therapy	6-month PFS of 43% in the vaccine arm
III	N/A	Randomized trial. Patients will receive first-line chemotherapy plus vaccine versus placebo concurrently and as maintenance	Currently in planning stages

BSC: Best supportive care; CRT: Chemoradiation; DFS: Disease-free survivial; HR: Hazard ratio; MAGE-A3: Melanoma-associated antigen-A3; MUC-1: Mucinous glycoprotein 1; NSCLC: Non-small cell lung cancer; OS: Overall survival; PFS: Progression-free survival.

In addition, after favorable results with CIMAvax-EGF vaccine in a subset of patients that developed antibodies to EGF, a large Phase III international study was launched [8]. The study recently completed enrollment of 579 patients with advanced NSCLC who had stable or responding disease following initial platinum-based chemotherapy. The patients are randomized to receive either CimaVax-EGF and low-dose cyclophosphamide or best supportive care [9]. Due to its immunomodulatory effects, cyclophosphamide was added to help ‘boost' the effects of CimaVax-EGF vaccine [10].

Tumor-associated MUC1 vaccines include the TG40010 and the L-BLP25 vaccines. MUC1 is a transmembrane protein found on epithelial cell surface and is overexpressed in patients with NSCLC. These vaccines induce a T-cell response against MUC1 antigen. A large Phase III clinical trial (n = 1513), START, evaluated the efficacy of L-BLP25 (tecemotide). The study looked at the effects of tecemotide following chemotherapy and radiation therapy. Unfortunately, it failed to meet its primary endpoint of improved overall survival (OS) (25.6 vs 22.3 months, adjusted hazard ratio [HR] = 0.88, 95% CI 0.75 – 1.03, p = 0.123). Further analysis of the data indicated that patients who had received tecemotide after concurrent rather than sequential chemoradiation therapy derived some benefit in terms of OS (30.8 vs 20.6 months, HR = 0.78, 95% CI 0.64 – 0.95, p = 0.016) [11]. Currently, a clinical trial (NCT00828009) is recruiting patients in order to investigate the combined use of L-BLP25 and bevacizumab after concurrent chemotherapy and radiation therapy in patients with advanced NSCLC [12]. The TG4010 vaccine (MVA-MUC1-IL-2) is a recombinant viral vector vaccine that incorporates the MUC1 antigen into Ankara virus vector. Based on promising Phase II results, a large Phase IIb/III clinical trial was launched to compare the outcomes of first-line chemotherapy combined with TG4010 versus chemotherapy alone [13].

Belagenpumatucel-L (Lucanix) is a whole tumor cell-based vaccine composed of irradiated NSCLC cell lines. It transfects cells with a TGF-β2 antisense gene, downregulating the production of TGF-β2 and potentiating tumor antigen recognition. After promising Phase II results with belagenpumatucel-L, a prospective, multicenter, randomized, double-blinded Phase III trial (n = 532) was launched. The results of this study were recently presented at the multidisciplinary European cancer congresses. Unfortunately, belagenpumatucel-L (Lucanix) maintenance therapy administered after platinum-based frontline chemotherapy did not improve the OS. The median OS was 20.3 versus 17.8 months when compared to the placebo group (HR = 0.54; p = 0.0595) [14]. Interestingly, the study found that the OS improved in patients if the vaccine was given within 12 weeks of finishing frontline chemotherapy. Indeed, further data analysis revealed an OS of 20.7 in patients who received the vaccine within 12 weeks of stopping frontline chemotherapy versus 13.3 months in patients who received the vaccine after 12 weeks of stopping chemotherapy (HR = 0.77; p = 0.0092). Further studies will have to be conducted in order to further investigate this effect.

4. Immune checkpoint inhibitors

The advancing knowledge of the biology and immunology of solid tumors and their microenvironment led scientists to explore novel molecular targets. Of particular interest are two immune checkpoint molecules that are known to inhibit the host T-cell immune response and promote tumor growth and metastasis, the programmed death-1 (PD-1) and cytotoxic T-lymphocyte antigen 4 (CTLA-4). Indeed, immune checkpoint inhibitors have demonstrated impressive results in other solid tumors, particularly, in patients with metastatic melanoma [15]. A summary of immune checkpoint inhibitors that are currently being studied in NSCLC is presented in Table 2.

Table 2. Summary of investigational checkpoint inhibitors in NSCLC.

Checkpoint inhibitor	Mechanism of action	Phase of clinical testng	n	Study design	Results and comments
Ipilimumab	Monoclonal antibody directed against CTLA-4 on T-cells, leading to immune stimulation	II	204	Patients with stage IIIB–IV NSCLC; randomized trial of concurrent versus phased ipilimumab with carboplatin/paclitaxel versus chemotherapy alone	‘Phased' ipilimumab group showed improvement based on irPFS (HR = 0.64, p = 0.03) Median OS of 12.9 versus 9.1 versus 9.9 months for ‘phased,' ‘concurrent' and control groups, respectively No statistically significant differences
III	920	Randomized paclitaxel/carboplatin alone or with ipilimumab in patients with advanced squamous cell NSCLC	Primary endpoint – OS Secondary endpoint – PFS, ORR
Nivolumab (BMS-936558)	Monoclonal antibody against PD-1, leading to immune stimulation	Ib	129	Nonrandomized trial in pretreated patients with advanced NSCLC	ORR of 17.1% and median OS of 9.6 months, with durable responses at 1 year
III	264	Randomized trial of chemotherapy (docetaxel) versus nivolumab	Primary endpoint – OS Secondary endpoint – PFS
MK-3475	Monoclonal antibody against PD-1, leading to immune stimulation	I	38	Nonrandomized trial in previously pretreated patients with advanced NSCLC	Preliminary data: The immune-related ORR of 24 and 21% in nonsquamous and squamous NSCLC subtypes, respectively
MPLDL3280A	Monoclonal antibody against PD-L1, leading to immune stimulation	I	53	Nonrandomized trials in pretreated patients with advanced NSCLC with squamous and nonsquamous histology	Preliminary data: ORR of 24% and 24-week PFS of 46% Patients with PD-L1-positive tumors had 100% (4/4) responses Higher response rates in smokers (ORR = 26%) than non-smokers (ORR = 10%)

CTLA-4: Cytotoxic T-lymphocyte antigen 4; HR: Hazard ratio; irPFS: Immune-related progression-free survival; NSCLC: non-small cell lung cancer; ORR: Objective response rate; OS: Overall survival; PD-1: Programmed death-1; PFS: progression-free survival.

Ipilimumab is a monoclonal antibody directed against CTLA-4, a surface protein that blocks T-cell activation. In patients with untreated metastatic melanoma, ipilimumab was the first agent to demonstrate improved survival in two different Phase III clinical trials [16,17]. On the basis of this data, the FDA has approved ipililumab for the treatment of metastatic melanoma. As a result, ipilimumab is currently being evaluated for the treatment of advanced NSCLC. However, clinical trials using single-agent ipilimumab in NSCLC have not been published. Consequently, safety and efficacy of ipilimumab alone in NSCLC are not yet known. A Phase II multicenter double-blind randomized trial evaluated the efficacy of ipilimumab combined with paclitaxel and carboplatin in the setting of advanced NSCLC. Chemotherapy-naïve patients (n = 130) with advanced and previously untreated NSCLC were randomized to receive standard chemotherapy (paclitaxel and carboplatin) with placebo (control group) or chemotherapy plus concurrent ipilimumab (10 mg/kg) or phased ipilimumab. The primary endpoint of this study was progression-free survival (PFS) assessed via immune-response criteria (irRC). This approach takes into account that clinical response to immunotherapy can manifest after an initial increase in tumor burden or appearance of new lesions [18]. Only the phased ipilimumab schedule improved the immune-related progression-free survival (irPFS) versus control (HR = 0.64, p = 0.03). However, no improvement in PFS (HR = 0.93, p = 0.37) or OS (HR = 0.75, p = 0.13) was observed. The median OS was 12.9, 9.1 and 9.9 months for the ‘phased,' ‘concurrent' and control groups, respectively. However, no statistically significant differences were recorded. Interestingly, a subgroup analysis of this study found that the benefit of phased ipilimumab was more pronounced in patients with squamous cell lung cancer with HR for irPFS and OS of 0.55 (95% CI 0.27 – 1.12) and 0.48 (95% CI 0.22 – 1.03), respectively [19]. Consequently, this led to the initiation of a Phase III clinical trial evaluating the efficacy of phased ipilimumab in patients with squamous cell histology (NCT01285609) [20]. The immune-related adverse effects (AEs) were rash, pruritus, colitis and diarrhea. There were no grade 4 events for rash or pruritus. No cases of pneumonitis were noted. One event of grade 4 colitis was observed in the ‘phased' ipilimumab group. Of note, grade 3 or 4 elevations in alanine aminotransferase were noted in phased and concurrent ipilimumab groups, but none in the control group. Overall, the rates of grade 3 – 4 AEs were 21, 17 and 9% for the concurrent ipilimumab, phased ipilimumab and control groups, respectively [19].

PD-1 is an inhibitory T-cell surface receptor that binds PD-L1 and PD-L2 in order to regulate the balance between T-cell activation and tolerance. Tumors are able to evade the antitumor immune response by upregulating the production of PD-1 ligands. Highly expressed in human tumors, PD-L1 has been associated with the propensity toward metastases and portends poor prognosis [21]. Furthermore, increased expression of PD-1 has been associated with CD8⁺ T-cell dysfunction and impaired immune response [22]. Preclinical data of single-agent PD-1 blockade only showed modest efficacy. Surprisingly, clinical activity was noted in several tumors even in very early clinical trials. Specifically, objective responses were noted in melanoma and renal cell carcinoma. However, objective responses were also noted in patients with NSCLC, a tumor generally considered as non-immunogenic. Consequently, PD-1 checkpoint inhibition with antibodies against the receptor or its ligands has demonstrated promising early results in patients with NSCLC in numerous Phase I trials. Several agents targeting the PD-1 pathway are currently in development, including the anti-PD1 antibodies; MK-3475, nivolumab (BMS-936558/MDX-1106/ONO-4538) and the anti-PD-L1 antibodies MPLDL3280A and MedI-4736.

The efficacy and safety of nivolumab were studied in a Phase Ib multicenter study, which enrolled 298 patients with melanoma, renal cell carcinoma, castrate-resistant prostate cancer, advanced colon cancer and advanced NSCLC [23]. Efficacy was evaluated in 76 out of 122 patients with NSCLC. Overall responses (ORs) by RECIST criteria were seen in 18% (14/76) patients with NSCLC, with 24% having a PFS of 24 weeks. Of note, objective responses were noted in 6/18 patients with squamous cell histology and 7/56 patients with nonsquamous cell histology, suggesting activity in both histologic subtypes. Long-term data on 129 heavily pretreated patients were recently reported at the World Conference on Lung Cancer. The OR was 17.1% (16.7% squamous and 17.6% non-squamous histology), with a median OS of 9.6 months. Additionally, nivolumab was able to produce durable responses with an OS of 42% at 1 year and a median duration of response of 74 weeks [24]. Earlier safety studies reported immune-related AEs of any grade in 71% of patients, including rash (12%), diarrhea (11%), pruritus (9%), transaminitis (4%) and infusion reaction (3%). Grade 3 – 4 AEs were noted in 14% of patients. In addition, drug-related pneumonitis occurred in 6% of patients [23]. A recent interim analysis of AEs was presented at American Society of Clinical Oncology. Based on their data, 49% of the patients had grade 3 or 4 AEs, including pneumonitis (7%), rash (5%), nephritis (2%) and colitis (2%) [25]. Current guidelines suggest that pretreatment with immunosuppressive therapy can reduce the severity of pneumonitis. Consequently, patients suspected of PD-1–related pneumonitis should be treated with steroids, the anti-PD-1 antibody discontinued and empiric antibiotics should be considered as it maybe difficult to differentiate between drug-related and infection-induced pneumonitis. Currently, a large Phase III trial is investigating the use of single-agent nivolumab versus docetaxel in previously treated patients with advanced NSCLC (NCT01642004) [26].

MK-3475 is a humanized monoclonal IgG4 antibody against PD-1 that demonstrated a preliminary efficacy in patients with previously treated advanced NSCLC. Interim data of a Phase I trial was presented at the 15th World Conference on Lung Cancer. Previously treated patients with NSCLC (n = 38) were given MK-3475 at 10 mg/kg every 3 weeks. This study assessed response rate using irRC. The OR in nonsquamous and squamous subtypes was 24 and 21%, respectively. At the time of this report, nine responders continued to receive the therapy. The most commonly reported drug-related AEs were rash (21%), pruritus (18%), fatigue (16%), diarrhea (13%) and arthralgia (11%), with only one incident of grade 3 pulmonary edema [27].

There are two blocking anti-PD-L1 antibodies currently in development. They include MPDL3280A and MedI-4736. These antibodies block the interaction between PD-1 and PD-L1, not affecting the PD-1 and PD-L2 interaction. While in theory this can cause differences in efficacy and toxicity, clinically meaningful differences remain to be demonstrated. The first clinical study of anti-PD-L1 antibodies using BMS-936559 was conducted in various solid tumor types including NSCLC. The ORR in NSCLC was 10%, and 31% of patients were free from tumor progression at 6 months [28].

Although BMS-936559 is no longer in clinical development, MPDL3280A, a human monoclonal anti-PD-L1 antibody, has demonstrated promising results in an early Phase I trial. Preliminary data were recently presented at the European Cancer Congress. An ORR of 24% was observed in patients (n = 53) with squamous and non-squamous histology; the 24-week PFS was 46%. Interestingly, the analysis of biomarker data from archived tissue demonstrated a strong correlation between PD-L1 status and efficacy, with an ORR of 100 and 15% observed in PD-L1 positive and negative patients, respectively. In addition, the response rates were higher among current and former smokers (ORR = 26%) versus never-smokers (ORR = 10%). The incidence of all grade 3 and 4 AEs was 34%, including pericardial effusion (6%), dehydration (4%), dyspnea (4%) and fatigue (4%), with no grade 3 – 4 pneumonitis or diarrhea reported [29,30].

Immunotherapy has made significant progress in the past few years. Novel molecules such as immune checkpoint inhibitors (i.e., nivolumab, ipilimumab, MK-3475 and MPDL3280) have demonstrated exciting results in early clinical trials. Further understanding of the role of these molecules in treating patients with early stages of lung cancer or using them synergistically with other treatment modalities is necessary. While tumor vaccine therapies have yet to show improvement in OS, some of them display a clear trend toward better clinical outcomes. Nevertheless, significant challenges remain such as validation of efficacy in large randomized Phase III trials and validation of biomarkers of response to immune checkpoint inhibitors. While the new checkpoint inhibitors have unleashed new hopes in the battle against lung cancer, more research is required to understand their true clinical potential.

Declaration of interest

We certify that we do not have any affiliation with or financial involvement in any organization or entity with a direct financial interest in the subject matter or materials discussed in the manuscript (e.g., employment, consultancies, stock ownership, honoraria and expert testimony). We do not have any commercial or proprietary interest in any drug, device or equipment mentioned in the article.

Notice of correction

Please note that in the Abstract, we have removed “ipilimumab” from the sentence “Programmed death-1 (PD-1) … in early clinical trials.” after initial online publication of this article (10th February 2014).