New Therapies on the Horizon

Although lung cancer treatment has been transformed by the advent of checkpoint inhibitor immunotherapies, there remains a high unmet need for new effective therapies for patients with progressive disease. Novel treatment strategies include combination therapies with currently available programmed death ligand 1 inhibitors, targeting alternative immune checkpoints, and the use of novel immunomodulatory therapies. In addition, antibody-drug conjugates offer great promise as potent management options. As these agents are further tested in clinical trials, we anticipate that more effective therapies for patients with lung cancer are integrated into regular clinical practice.

Immunotherapy in Advanced NSCLC Without Driver Mutations: Available Therapeutic Alternatives After Progression and Future Treatment Options

The treatment paradigm of non-small-cell lung cancer without oncogenic drivers has varied dramatically in recent years and is constantly evolving. Immune- checkpoint inhibitors have demonstrated unprecedented durable efficacy in a subset of these patients, so these drugs have become the standard of care in most cases. There are different ways to deliver these agents, such as monotherapy and combinations of immunotherapy or chemotherapy plus immunotherapy. Treatment selection is complicated by an absence of head-to-head comparisons in randomized trials because these agents have gained approval by demonstrating superiority to platinum-doublet chemotherapy alone. Unfortunately, most patients will progress and die from their disease despite advances. Furthermore, after progression on these agents, there is a lack of randomized controlled data to support further management, constituting an unmet need. This review discusses the therapeutic alternatives after progression, summarizes mechanisms of resistance and progression patterns, and describes the main approaches under clinical investigation in the field.

Managing Resistance to Immune Checkpoint Inhibitors in Lung Cancer: Treatment and Novel Strategies

A proportion of patients with lung cancer experience long-term clinical benefit with immune checkpoint inhibitors (ICIs). However, most patients develop disease progression during treatment or after treatment discontinuation. Definitions of immune resistance are heterogeneous according to different clinical and biologic features. Primary resistance and acquired resistance, related to tumor-intrinsic and tumor-extrinsic mechanisms, are identified according to previous response patterns and timing of occurrence. The clinical resistance patterns determine differential clinical approaches. To date, several combination therapies are under development to delay or prevent the occurrence of resistance to ICIs, including the blockade of immune coinhibitory signals, the activation of those with costimulatory functions, the modulation of the tumor microenvironment, and the targeting T-cell priming. Tailoring the specific treatments with distinctive biologic resistance mechanisms would be ideal to improve the design and results of clinical trial. In this review, we reviewed the available evidence on immune resistance mechanisms, clinical definitions, and management of resistance to ICIs in lung cancer. We also reviewed data on novel strategies under investigation in this setting.

Which treatment after first line therapy in NSCLC patients without genetic alterations in the era of immunotherapy?

Cancer immunotherapy has produced an unprecedented durable response rate, thus shifting from traditional doublet chemotherapy to immunotherapy-based treatments with and without chemotherapy as the first line strategies for advanced non-small cell lung cancer patients without a molecular driver. However, the majority of patients do not benefit from the treatment or may relapse after a period of response. As few treatment options are available after failure of cancer immunotherapy, including the combination of chemotherapy and anti-angiogenic drugs, a better understanding of the mechanisms limiting cancer immunotherapy may be of help in the definition of the best second line. Whereas only retrospective data support an immunotherapy rechallenge approach, new combination strategies including immunotherapy and cell-signaling inhibitors or double immunotherapy represent the newest and most promising strategy to overcome primary or acquired resistance to first line immunotherapy.

Entinostat plus Pembrolizumab in Patients with Metastatic NSCLC Previously Treated with Anti-PD-(L)1 Therapy

PURPOSE

New therapies are needed to treat immune checkpoint inhibitor-resistant non-small cell lung cancer (NSCLC) and identify biomarkers to personalize treatment. Epigenetic therapies, including histone deacetylase inhibitors, may synergize with programmed cell death-1 (PD-1) blockade to overcome resistance. We report outcomes in patients with anti-programmed cell death ligand-1 [PD-(L)1]-resistant/refractory NSCLC treated with pembrolizumab plus entinostat in ENCORE 601.

PATIENTS AND METHODS

The expansion cohort of ENCORE 601 included patients with NSCLC who previously experienced disease progression with immune checkpoint inhibitors. The primary endpoint for the phase II expansion cohort is overall response rate (ORR); safety, tolerability, and exploratory endpoints are described.

RESULTS

Of 76 treated patients, 71 were evaluable for efficacy. immune-regulated RECIST-assessed ORR was 9.2% [95% confidence interval (CI): 3.8-18.1], which did not meet the prespecified threshold for positivity. Median duration of response was 10.1 months (95% CI: 3.9-not estimable), progression-free survival (PFS) at 6 months was 22%, median PFS was 2.8 months (95% CI: 1.5-4.1), and median overall survival was 11.7 months (95% CI: 7.6-13.4). Benefit was enriched among patients with high levels of circulating classical monocytes at baseline. Baseline tumor PD-L1 expression and IFNγ gene expression were not associated with benefit. Treatment-related grade ≥3 adverse events occurred in 41% of patients.

CONCLUSIONS

In anti-PD-(L)1-experienced patients with NSCLC, entinostat plus pembrolizumab did not achieve the primary response rate endpoint but provided a clinically meaningful benefit, with objective response in 9% of patients. No new toxicities, including immune-related adverse events, were seen for either drug. Future studies will continue to evaluate the association of monocyte levels and response.

TAM kinase inhibition and immune checkpoint blockade- a winning combination in cancer treatment?

Introduction: Immune checkpoint inhibitors (ICI) have shown great promise in a wide spectrum of malignancies. However, responses are not always durable, and this mode of treatment is only effective in a subset of patients. As such, there exists an unmet need for novel approaches to bolster ICI efficacy.Areas covered: We review the role of the Tyro3, Axl, and Mer (TAM) receptor tyrosine kinases in promoting tumor-induced immune suppression and discuss the benefits that may be derived from combining ICI with TAM kinase-targeted tyrosine kinase inhibitors. We searched the MEDLINE Public Library of Medicine (PubMed) and EMBASE databases and referred to ClinicalTrials.gov for relevant ongoing studies.Expert opinion: Targeting of TAM kinases may improve the efficacy of immune checkpoint blockade. However, it remains to be determined whether this effect will be better achieved by the selective targeting of each TAM receptor, depending on the context, or by multi-receptor TAM inhibitors. Triple inhibition of all TAM receptors is more likely to be associated with an increased risk for adverse events. Clinical trial designs should use high-resolution clinical endpoints and proper control arms to determine the synergistic effects of combining TAM inhibition with immune checkpoint blockade.

Treatment options after first-line immunotherapy in metastatic NSCLC

Introduction: The recent approvals of checkpoint inhibitors as single agents or in combination with chemotherapy with programmed death ligand 1 expression of < or ≥1% have challenged clinicians when it is time to begin a metastatic lung cancer patient in second-line therapy. The advantages given by immunotherapy over conventional chemotherapy such as improved overall survival and a better toxicity profile make the second-line clinical scenario more difficult for a patient who faces a likely inferior regimen as well as toxicity which may significantly impact the quality of life.Areas covered: Options given today by the National Comprehensive Cancer Network are very limited, and essentially, we go back to conventional cytotoxic agents alone or in combination with biological agents if possible. In this article, we discuss the actual treatment available for this difficult scenario and some of the ongoing trials which aim to address this dilemma.Expert commentary: This is an unmet need in lung cancer management; we need a better understanding of the mechanism of resistance to immunotherapy so we can target them once the patient moves to second-line treatment.

Phase I/Ib Study of Pembrolizumab Plus Vorinostat in Advanced/Metastatic Non-Small Cell Lung Cancer

PURPOSE

Histone deacetylase inhibitors (HDACi) enhance tumor immunogenicity through several mechanisms and may improve response to immune checkpoint inhibitors (ICIs). In a phase I/Ib trial, we tested the oral HDACi vorinostat combined with the programmed cell death protein 1 inhibitor pembrolizumab in advanced/metastatic non-small cell lung cancer.

PATIENTS AND METHODS

Patients received intravenous pembrolizumab (200 mg every 3 weeks) plus oral vorinostat (200 or 400 mg/day). Primary endpoint was safety/tolerability. Secondary endpoints included response rate, progression-free survival, disease control rate (DCR), and overall survival. Tumor gene expression changes, T-cell density, and myeloid cell levels were studied in serial tissue specimens.

RESULTS

Thirty-three patients were treated (13 in phase I, 20 in phase Ib). In phase I, both ICI-naïve and ICI-pretreated patients were enrolled to determine dose-limiting toxicities (DLT). No DLTs were observed, and the recommended phase I dose was pembrolizumab 200 mg and vorinostat 400 mg. Any-grade adverse events were mainly fatigue (33%) and nausea/vomiting (27%). Of six ICI-naïve and 24 ICI-pretreated patients evaluable for response, four (13%) had partial response [two confirmed, one unconfirmed with subsequent prolonged stable disease (SD), one unconfirmed with subsequent progressive disease (PD)], 16 (53%) had SD, and 10 (33%) had PD for a DCR of 67%. In the ICI-pretreated cohort, three patients (one confirmed, two unconfirmed) had partial response and 10 had SD. Pretreatment CD8⁺ T-cell presence in tumor stromal regions was associated with treatment benefit.

CONCLUSIONS

Pembrolizumab plus vorinostat was well tolerated and demonstrated preliminary antitumor activity despite progression on prior ICI treatment.